Welding
Handbook
Ninth Edition
Volume 5
MATERIALS AND APPLICATIONS, PART 2
American Welding Society
i
Welding Handbook, Ninth Edition
Volume 1 Welding Science and Technology
Volume 2 Welding Processes, Part 1 Volume
3
Welding Processes, Part 2 Volume
4
Materials and Applications, Part 1
Volume 5 Materials and Applications, Part 2
ii
Welding
Handbook
Ninth Edition
Volume 5
MATERIALS AND APPLICATIONS, PART 2
Prepared under the direction of
the Welding Handbook
Committee
Annette O’Brien, Editor Kathy
American Welding Society
8669 NW 36 St, # 130
Miami, FL 33126
iii
© 2015 by American Welding Society
All rights reserved
No portion of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means,
including mechanical, photocopying, recording, or otherwise, without the prior written permission of the copyright
owner.
Authorization to photocopy items for internal, personal, or educational classroom use only, or the internal, personal,
or educational classroom use only of specific clients, is granted by the American Welding Society (AWS) provided
the appropriate fee is paid to the Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923; telephone:
(978) 750-8400; Internet: www.copyright.com.
Library of Congress Control Number: 2001089999
ISBN: 978-0-87171-856-3
The Welding Handbook is the result of the collective effort of many volunteer technical specialists who provide information to assist with the design and application of welding and allied processes.
The information and data presented in the Welding Handbook are intended for informational purposes only. Reasonable care is exercised in the compilation and publication of the Welding Handbook to ensure the authenticity of the contents. However, no representation is made as to the accuracy, reliability, or completeness of this information, and an
independent substantiating investigation of the information should be undertaken by the user.
The information contained in the Welding Handbook shall not be construed as a grant of any right of manufacture,
sale, use, or reproduction in connection with any method, process, apparatus, product, composition, or system, which
is covered by patent, copyright, or trademark. Also, it shall not be construed as a defense against any liability for such
infringement. Whether the use of any information in the Welding Handbook would result in an infringement of any
patent, copyright, or trademark is a determination to be made by the user.
iv
DEDICATION
The Welding Handbook Committee dedicates this book jointly to Bernhard J. (Bernie) Bastian, long-term member
of the Welding Handbook Committee, and Annette O’Brien, Senior Editor, in recognition of their contributions to
the five volumes of the 9th edition of the Welding Handbook for the American Welding Society.
B. J. Bastian
B. J. Bastian, M.S., P.E., welding consultant, teacher, writer, mentor, and contributor to the technology of automotive welding, has generously shared the expertise acquired during his 50-year career in the welding industry by
serving on the Welding Handbook Committee. He has provided valuable guidance to the Committee on the organization and technical content of the Welding Handbook, and was responsible for oversight and final reviews of
various chapters of each of the five volumes of the 9th edition.
Bernie’s career includes work with Ford Motor Company and Chrysler Corporation, not only in welding engineering and management, but also as an instructor and coach for welders and technicians. He has a Bachelor of Science
degree in mechanical engineering and a Master's degree in metallurgical engineering from Rensselaer Polytechnic
Institute. He added postgraduate studies at the University of Michigan. He taught welding and related courses at
Henry Ford Community College for 17 years, and has written instructive articles for a number of technical publications.
He is a Fellow of the American Welding Society and was also honored as a Life Member in recognition of his work
as a volunteer with AWS. He is a past member of the AWS Board of Directors.
Annette O’Brien
Annette O’Brien served as Editor for all five volumes of the Ninth Edition of the Welding Handbook. For more
than 15 years she diligently and patiently guided the volumes, each containing over 700 pages, through many
stages of editing, proofing, review, and final approval necessary to produce one of the finest series of reference
books in the welding industry.
Annette also served as Secretary to the Welding Handbook Committee, organizing meetings, preparing minutes,
expediting and distributing chapters for peer reviews, and communicating the information necessary to keep the
committee informed and on schedule. Her many years of commitment to the Welding Handbook have been invaluable
to the American Welding Society.
v
CONTENTS
DEDICATION .
ACKNOWLEDGMENTS .
PREFACE .
REVIEWERS .
CONTRIBUTORS .
v
x
xi
xii
xiii
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS.
Introduction .
Aluminum Product Forms .
Properties and Performance of Aluminum Weldments .
Arc Welding of Aluminum.
High Energy Beam Welding Processes.
Resistance Welding .
Solid-State Welding.
Oxyfuel Gas Welding.
Brazing .
Soldering .
Adhesive Bonding .
Joining Aluminum to Dissimilar Metals .
Arc Cutting .
Applications .
Safe Practices .
Bibliography .
Supplementary Reading List .
2
2
3
37
48
86
93
101
106
111
117
123
124
126
128
131
132
133
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS .
Introduction .
Alloying Elements.
Arc Welding.
Resistance Welding .
High-Energy Beam Welding.
Solid-State Welding.
Oxyfuel Gas Welding.
Brazing .
Soldering .
Joining of Dissimilar Metals .
Plasma Arc Cutting .
Applications .
Safe Practices .
Bibliography .
Supplementary Reading List .
137
138
140
148
165
175
179
190
192
196
198
198
199
206
207
210
CHAPTER 3—COPPER AND COPPER ALLOYS.
Introduction .
Copper Alloys .
High-Copper Alloys .
Welding and Joining Processes.
Filler Metals .
Joint Designs for Copper Welds.
Welding Conditions .
Brazing .
Soldering .
Applications .
Safe Practices .
215
216
217
221
225
229
233
233
253
260
263
271
vii
Bibliography. ......................................................................................................................................................272
Supplementary Reading List. . . ..........................................................................................................................272
CHAPTER 4—NICKEL AND COBALT ALLOYS. . .................................................................................275
Introduction . . ....................................................................................................................................................276
Physical and Mechanical Properties. . .................................................................................................................277
Alloy Groups. . ...................................................................................................................................................278
Surface Preparation for Welding. ........................................................................................................................289
Arc Welding . ......................................................................................................................................................290
Other Welding Processes . . .................................................................................................................................315
Fabrication for High-Temperature Service. . .......................................................................................................323
Weld Cladding . . ................................................................................................................................................327
Brazing. ..............................................................................................................................................................338
Soldering . . .........................................................................................................................................................342
Thermal Cutting. . . ............................................................................................................................................343
Applications . . ....................................................................................................................................................344
Safe Practices. . ...................................................................................................................................................347
Bibliography. . ....................................................................................................................................................349
Supplementary Reading List. . ............................................................................................................................349
CHAPTER 5—LEAD AND ZINC . ................................................................................................................351
Introduction . . ....................................................................................................................................................352
Welding of Lead . . ..............................................................................................................................................352
Lead Soldering . . . ..............................................................................................................................................362
Welding and Soldering of Zinc . ..........................................................................................................................367
Typical Applications for Lead . ...........................................................................................................................376
Typical Applications for Zinc . ............................................................................................................................378
Safe Practices. .....................................................................................................................................................380
Bibliography. ......................................................................................................................................................382
Supplementary Reading List. . ............................................................................................................................383
CHAPTER 6—TITANIIUM AND TITANIUM ALLOYS . . .......................................................................385
Introduction . . ....................................................................................................................................................386
Physical Metallurgy of Titanium . . . ...................................................................................................................388
Welding Metallurgy of Titanium and Titanium Alloys . ......................................................................................400
Joint Processes for Titanium. . . ..........................................................................................................................415
Brazing. ..............................................................................................................................................................432
Thermal Cutting. . . ............................................................................................................................................434
Applications . . ....................................................................................................................................................435
Safe Practices. .....................................................................................................................................................444
Bibliography. . ....................................................................................................................................................445
Supplementary Reading List. . ............................................................................................................................445
CHAPTER 7—REACTIVE, REFRACTORY, AND PRECIOUS METALS . . ........................................449
Introduction . . ....................................................................................................................................................450
Reactive Metals. . . .............................................................................................................................................450
Zirconium ..........................................................................................................................................................451
Hafnium .............................................................................................................................................................463
Beryllium . . ........................................................................................................................................................467
Beryllium-Aluminum . ........................................................................................................................................470
Uranium .............................................................................................................................................................473
Refractory Metals . . ...........................................................................................................................................475
Tantalum . .......................................................................................................................................................475
Niobium . . ......................................................................................................................................................478
Molybdenum and Tungsten . . .........................................................................................................................483
Rhenium. ........................................................................................................................................................488
viii
Precious Metals .
Gold .
Silver.
Platinum and Platinum Alloys.
Palladium.
Iridium.
Osmium .
Rhodium.
Ruthenium .
Applications .
Safe Practices .
Bibliography .
Supplementary Reading List .
491
494
497
499
502
503
505
505
506
506
511
512
513
CHAPTER 8—PLASTICS.
Introduction .
Welding Processes for Thermoplastics .
Weld Quality of Thermoplastics .
Applications .
Safe Practices .
Bibliography .
Supplementary Reading List .
517
518
520
557
558
564
565
566
CHAPTER 9—CERAMICS .
Introduction .
Ceramic Materials .
Welding and Joining Processes.
Applications .
Safe Practices .
Bibliography .
Supplementary Reading List .
569
570
571
575
590
592
595
596
CHAPTER 10—COMPOSITES .
Introduction .
Welding Polymeric Composites.
Metal Matrix Composites .
Safe Practices .
Bibliography .
Supplementary Reading List .
599
600
603
613
638
639
642
APPENDIX A—SAFETY CODES AND OTHER STANDARDS .
Publishers of Safety Codes and Other Standards .
643
645
APPENDIX B—WELDING HANDBOOK REFERENCE GUIDE .
649
MAJOR SUBJECT INDEX.
Volumes 3 and 4, Eighth Edition .
Volumes 1, 2, 3, 4, and 5, Ninth Edition .
667
667
667
INDEX OF VOLUME 5, NINTH EDITION .
691
ix
ACKNOWLEDGMENTS
The Welding Handbook Committee of the American Welding Society and the editors gratefully recognize the contributions of the volunteers who have created, developed, and documented the technology of welding and shared it in past
editions of the Welding Handbook, beginning with the first edition published in 1938. The enthusiasm and meticulous
dedication of the authors and technologists reflected in the previous eight editions of the Welding Handbook are
continued in this volume of the Ninth Edition.
This volume was compiled by the members the Welding Handbook Volume 5 Committee and the WH5 Chapter
Committees, with oversight by the Welding Handbook Committee. Chapter committee chairs, chapter committee
members, and oversight persons are recognized on the title pages of the chapters.
The Welding Handbook Committee and the editors recognize and appreciate the AWS technical committees who
developed the consensus standards that pertain to this volume, and acknowledge the work of the editors of the Eighth
Edition of the Welding Handbook: L. P. Connor, Volume 1; R. L. O’Brien, Volume 2; and W. R. Oates, Volumes 3
and 4. The Welding Handbook Committee is grateful to members of the AWS Technical Activities Committee and
the AWS Safety and Health Committee for their reviews of the chapters. The editors appreciate the AWS Technical
Services staff for their assistance during the preparation of this volume.
Welding Handbook Committee Chairs, 1938–2015
1938–1942
Circa 1950
1956–1958
1958–1960
1960–1962
1962–1965
1965–1966
1966–1967
1967–1968
1968–1969
1969–1970
1970–1971
1971–1972
1972–1975
1975–1978
1978–1981
1981–1984
1984–1987
1987–1990
1990–1992
1992–1996
1996–1999
1999–2004
2004–2007
2007–2009
2009–2014
2015–0000
D. S. Jacobus
H. L. Boardman
F. L. Plummer
R. D. Stout
J. F. Randall
G. E. Claussen
H. Schwartzbart
A. Lesnewich
W. L. Burch
L. F. Lockwood
P. W. Ramsey
D. V. Wilcox
C. E. Jackson
S. Weiss
A. W. Pense
W. L. Wilcox
J. R. Condra
J. R. Hannahs
M. J. Tomsic
C. W. Case
B. R. Somers
P. I. Temple
H. R. Castner
P. I. Temple
C. E. Pepper
Wangen Lin
D. D. Kautz
x
PREFACE
This is Volume 5, the last in the series of the Ninth Edition of the Welding Handbook. It is Materials and Applications,
Part 2, presented in ten peer-reviewed chapters covering the welding of nonferrous metals and materials. The titles
of the chapters in this book indicate the variety of challenges presented to welders, designers, welding engineers, and
others in the welding workplace.
The scientists who examine the microstructures of metals and other materials, identify constituents, and determine
how the properties of these materials can be used and controlled during welding have contributed to the expanded
information in this book. Some of the best scientists in the welding industry from universities, government and private research laboratories, metals-producing companies, fabricators, consulting firms, and testing facilities have
stepped forward as volunteers to update this volume. They are recognized on the title pages of their respective
chapters.
This volume covers the technicalities of joining aluminum; magnesium; copper; nickel and cobalt; lead and zinc;
titanium; reactive, refractory, and precious metals; plastics; ceramics; and composites. Each chapter includes a
thorough explanation of the metal or other material, details of the welding processes used to join it, and a comprehensive bibliography. A section on safe practices pertinent to the specific metal or material is included in each
chapter.
Two appendices provide supplemental information. Appendix A is a list of sources of safety codes and standards,
with contact information of the publishers. Appendix B is a reference guide to Ninth Edition Volumes 1, 2, 3, and
4, included to accommodate the frequent references to the chapters of these books.
This volume concludes the Ninth edition of the Welding Handbook, following the four published volumes: Volume
1, Welding Science and Technology, which provides the foundation for successful welding and allied processes;
Volume 2, Welding Processes, Part 1, which contains the technical details of arc welding and cutting, the gas
processes, brazing, and soldering; Volume 3, Welding Processes, Part 2, comprised of the resistance, solid-state,
and other welding processes; and Volume 4, Materials and Applications, Part 1, which covers the ferrous metals.
Volume 5, Materials and Applications, Part 2, covers nonferrous metals and materials, including ceramics, plastics,
and composites.
These five books, all peer-reviewed, are made up of 67 chapters; overall, they represent the collaborative work of a
total of 428 volunteers who generously spent many hours of personal time to provide authentic technical information from their specific areas of expertise. The Welding Handbook Committee extends its gratitude to each of these
volunteers.
The Welding Handbook Committee welcomes your comments and suggestions. Please address them to the Editor,
Welding Handbook, American Welding Society, 8669 NW 36 St, # 130, Miami, FL 33126.
Wangen Lin, Past Chair
Welding Handbook Committee
Douglas D. Kautz, Chair
Welding Handbook Committee
and Volume 5 Committee
Welding Handbook
Annette O’Brien, Senior Editor
Kathy Sinnes, Associate Editor
xi
REVIEWERS
AMERICAN WELDING SOCIETY SAFETY
AND HEALTH COMMITTEE AND
TECHNICAL ACTIVITIES COMMITTEE
D. E. Clark
D. A. Fink
S. R. Fiore
W. A. Komlos
D. J. Landon
K. A. Lyttle
D. D. Rager
A. W. Sindel
W. J. Sperko
Idaho National Laboratory, Ret.
The Lincoln Electric Company
Hobart Brothers Company
Arc Tech, LLC
Vermeer Corporation
Praxair Inc.
Rager Consulting, Incorporated
Alstom Power, Incorporated
Sperko Engineering Services
xii
CONTRIBUTORS
WELDING HANDBOOK COMMITTEE
Wangen Lin, Chair
R. W. Warke, 1st Vice Chair
D. D. Kautz, 2nd Vice Chair
A. O’Brien, Secretary
B. J. Bastian
H. R. Castner
M. D. Hayes
S. P. Moran
J. H. Myers
T. A. Palmer
J. J. Perdomo
C. E Pepper
P. I. Temple
G. A. Young
Pratt & Whitney
Stress Engineering Services
Los Alamos National Laboratory
American Welding Society
Benmar Associates
EWI
Acute Technological Services
Weir American Hydro
Welding Inspection & Consulting Services
Pennsylvania State University
ExxonMobile Research and Engineering Co.
Ford, Bacon & Davis
eNergyWise Consulting, LLC
Consultant
WELDING HANDBOOK VOLUME 4 COMMITTEE
D. D. Kautz, Chair
R. W. Warke, Vice Chair
A. O’Brien, Secretary
B. J. Bastian
H. R. Castner
S. P. Moran
J. Myers
Los Alamos National Laboratory
Stress Engineering Services
American Welding Society
Benmar Associates
EWI
Weir American Hydro
Welding Inspection and Consulting Services
CHAPTER CHAIRS
Chapter 1
Chapter 2
Chapter 3
Chapter 4
Chapter 5
Chapter 6
Chapter 7
Chapter 8
Chapter 9
Chapter 10
T. A. Anderson
C. E. Cross
K. Lachenberg
G. R. LaFlamme
H. J. White
F. E. Goodwin
C. E. Cross
B. Krueger
B. Krueger
G. W. Ritter
C. E. Pepper
A. Benatar
ITW North America
Los Alamos National Laboratory
PTR Precision Technologies
Sciaky
PCC Energy Group
International Lead and Zinc Research Organization
Los Alamos National Laboratory
Los Alamos National Laboratory
Los Alamos National Laboratory
EWI
Ford, Bacon & Davis
The Ohio State University
xiii
1
AWS WELDING HANDBOOK
CHAPTER
C H A P T E1 R
9
ALUMINUM AND
ALUMINUM
ALLOYS
Prepared by the Welding
Handbook Chapter
Committee on Aluminum
and Aluminum Alloys:
T. Anderson, Chair
ITW Welding North America
B. E. Anderson
Consultant
F. G. Armao
The Lincoln Electric Company
P. Berube
Consultant
T. Burns
AlcoTec Wire Corp.
D. M. DePauw
Miller Electric Mfg. Co.
J. Ginder
ESAB
B. W. Hemmert
Miller Electric Mfg. Co.
R. B. Hirsch
Unitrol Electronics Inc.
C. Hsu
Nelson Stud Welding
M. S. Kadlec
Miller Electric Mfg. Co.
S. F. McCleary
ALCOA, Inc.
M. A. Palmer
Miller Electric Mfg. Co.
S. E. Pollard
Machinists, Inc.
M. J. Russell
TWI
D. J. Spinella
ALCOA, Inc.
M. P. Vandenberg
Miller Electric Mfg. Co.
K. L. Williams
ALCOA, Inc.
J. Zhang
The Lincoln Electric Company
Welding Handbook Volume 4
Committee Member:
J. H. Myers
Weld Inspection and
Consulting Services
Contents
Introduction
Aluminum Product Forms
Properties and Performance
of Aluminum Weldments
Arc Welding of Aluminum
High Energy Beam
Welding Processes
Resistance Welding
Solid-State Welding
Oxyfuel Gas Welding
Brazing
Soldering
Adhesive Bonding
Joining to Dissimilar Metals
Arc Cutting
Applications
Safe Practices
Bibliography
Supplementary Reading List
Photograph courtesy of Miller Electric Company
Gas Metal Arc Welding an Aluminum Seat Frame for a Racing Car
2
3
37
48
88
95
103
108
109
119
125
126
128
130
133
134
135
2
AWS WELDING HANDBOOK
CHAPTER 1
ALUMINUM AND
ALUMINUM ALLOYS
INTRODUCTION
Aluminum (Al), one of the most plentiful elements
mined from the earth, is found in its oxidized form in
bauxite, which, when refined, yields 40% to 60% alumina (aluminum oxide, Al2O3). The aluminum is
separated from the oxygen using the Hall-Héroult electrolysis process, which was invented in 1886. This
process made possible the production of aluminum
on an industrial scale, increasing availability and drastically reducing the cost from the prevalent price of
$600/lb in the years before. Aluminum usage in the
world has grown exponentially since then, driven by
the development of new joining technology and new
applications.
Aluminum is highly ranked among the most useful
metals known to manufacturers and fabricators. The
strength of some aluminum alloys exceeds that of mild
steel; aluminum can be cast, rolled, stamped, drawn,
spun, stretched, or roll-formed. It can be hammered,
forged, or machined with ease and speed, or extruded
into a wide variety of shapes; then it can be given an
equally wide variety of mechanical, electromechanical,
chemical, or paint finishes.
Aluminum retains good ductility at subzero temperatures, is highly resistant to corrosion, and is not toxic. It
has good electrical and thermal conductivity, is highly
reflective of heat and light, and is nonsparking and
nonmagnetic.
The properties of aluminum and aluminum alloys
are valuable for critical applications in the space and
aircraft, marine, and automotive industries; for structural applications; for vessels and storage tanks; and
are also vital for countless consumer products. Processes to weld aluminum continue to improve and have
contributed to the widespread use of this remarkable
material.
Most of the common joining methods—welding,
brazing, soldering, adhesive bonding, and mechanical
fastening—can be used to join aluminum.1 All processes, except mechanical fastening, are discussed in
this chapter; a brief section on aluminum cutting is also
included.2, 3
GENERAL CHARACTERISTICS OF
ALUMINUM
Pure aluminum melts at 660°C (1220°F). Aluminum
alloys have an approximate melting range of 480°C to
660°C (900°F to 1220°F), depending on the alloy.
There is no color change in aluminum when heated to
the welding or brazing temperature range, therefore the
welder cannot be guided by color and must assume a
position that will allow direct observation of the melting of the base and filler metals under the arc or flame.
1. For information on welding, brazing, soldering, and adhesive
bonding processes, refer to American Welding Society (AWS) Welding
Handbook Committee, 2004, Welding Handbook, 9th ed., ed. A.
O’Brien, and Welding Processes, vol. 2, Part 1, ed. A. O’Brien, and
Welding Processes, vol. 3, Part 2, 2007, ed. A. O’Brien and C. Guzman,
Miami: American Welding Society. Refer to Appendix B of this volume
for a list of chapter contents for the five volumes of Welding Handbook,
9th ed.
2. At the time this chapter was prepared, the referenced codes and
other standards were valid. If a code or other standard is cited without a date of publication, it is understood that the latest edition of the
document referred to applies. If a code or other standard is cited with
the date of publication, the citation refers to that edition only, and it
is understood that any future revisions or amendments to the code are
not included; however, as codes and standards undergo frequent revision, the reader must consult the most recent edition.
3. Welding terms and definitions used throughout this chapter are
from American Welding Society (AWS) Committee on Definitions and
Symbols, 2010, Standard Welding Terms and Definitions, AWS
A3.0M/A3.0:2010, Miami: American Welding Society.
AWS WELDING HANDBOOK
For fusion welding, the high thermal conductivity of
aluminum (compared to steel) necessitates a high rate of
heat input. Thick sections may require preheating. For
resistance spot welding, the high thermal and electrical
conductivity of aluminum requires a higher current, a
shorter weld time, and more precise control of welding
variables than required for steel. Because aluminum is
nonmagnetic and no arc blow occurs when welding
with direct current, aluminum is often used for weld
backing and for the construction of welding fixtures.
Aluminum and aluminum alloys develop an oxide
film when exposed to air. This natural oxide film,
which melts at about 2040°C (3700°F), can be broken
up by the application of direct current electrode positive
(DCEP) polarity during welding. Aluminum oxide can be
chemically or mechanically removed. Exposure to elevated temperatures during thermal treatments or exposure to moist environments causes the aluminum oxide
film to thicken significantly, necessitating mechanical or
chemical removal prior to welding or joining.
Anodic electrolytic or anodized treatments applied to
aluminum result in the formation of thick, dense oxide
coatings that must be removed prior to joining with
fusion welding, resistance welding, brazing, or soldering.4 Anodic coatings can resist 400 volts (V) or more,
so a welding arc cannot be initiated. During preparations for arc welding, the oxide coating must be
removed, not only from the joint, but also from the area
adjacent to the workpiece lead.
The properties and performance of aluminum
weldments are influenced by microstructural changes
that occur during any elevated-temperature joining process. The original properties of strength, fatigue life,
ductility, and formability in the workpieces can change,
depending on the amount of annealing, over-aging, and
cast-structure formation that occurs during the joining
process. The results of these changes are presented in
subsequent sections of this chapter devoted to specific
joining processes.
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
alloys are additionally classified by the method of casting: sand casting, permanent mold casting, and die casting. Wrought and cast aluminum alloys have similar
joining characteristics, regardless of product form, so
that essentially the same welding, brazing, and soldering practices are used on both cast and wrought aluminum, with one exception: welding or brazing is not
recommended for joining conventional die castings.
Conventional die castings can be joined by adhesive
bonding and, to a limited extent, by soldering. Vacuum
die casting technology has improved the quality of castings to the point that some castings may be satisfactorily joined by welding.
To increase corrosion resistance, some aluminum
alloys are manufactured with a high-purity aluminum
or a special aluminum alloy material applied to the
product surfaces. The cladding process is accomplished
by the application of cladding material to one or both
sides of the workpieces in thicknesses ranging from
2.5% to 15% of the total thickness of the workpiece.
Cladding not only protects the composite, but generally
exerts a galvanic effect, which further protects the core
alloy. Special cladding alloys are also available for brazing, soldering, and finishing purposes.
WROUGHT ALUMINUM ALLOYS
Wrought aluminum alloys are supplied as sheet,
plate, extrusions, or forgings. Table 1.1 lists the major
alloying elements in wrought aluminum alloys. A system of four-digit numerical designations is used to classify wrought aluminum alloys.
Table 1.1
Designations for Wrought Alloy Groups
Aluminum, 99.0% and greater
ALUMINUM PRODUCT FORMS
Aluminum is supplied as wrought products (sheet,
plate, extrusions, and forgings) or cast products. Pure aluminum is readily alloyed with many other metals to produce a wide range of physical and mechanical properties.
Aluminum alloys are classified according to the
means by which the alloying elements strengthen the
aluminum, which places the alloys into two categories:
nonheat treatable and heat treatable. Cast aluminum
4. The term coating is used to describe a deliberate chemical buildup
of aluminum oxide on aluminum surfaces that results in a very thick,
dense oxide layer on the aluminum surface.
3
1XXX
Major Alloying Element
Copper
2XXX
Manganese
3XXX
Silicon
4XXX
Magnesium
5XXX
Magnesium and Silicon
6XXX
Zinc
7XXX
Other elements
8XXX
Unused series
9XXX
Note: The second digit in all groups indicates consecutive modifications of an
original alloy, such as 5154, 5254, 5454, and 5654 alloys. The last two digits
in the 1xxx series indicate the minimum aluminum purity, e.g., 1060 is a
99.60% minimum Al. The last two digits in all other groups have no significance.
4
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
Aluminum Alloys and Alloying Elements
According to the four-digit numerical designation
system, the first digit of the 1XXX series indicates
the alloy group; the second digit indicates consecutive
modifications of an original alloy; the last two digits
indicate the minimum percentage of aluminum.
For alloys in the 2XXX through 9XXX series, the
first digit indicates the alloy group. The second digit
indicates the consecutive modifications to an original
alloy, such as Alloys 5154, 5254, 5454, and 5654. The
position of the last two digits in the 2XXX through
9XXX series has no special significance, but serves only
to identify the aluminum alloys in the group.
1XXX Series. Alloys in the 1XXX series are often
referred to as the pure aluminum alloys because they
are required to have a minimum of 99.0% aluminum.
These alloys are weldable, but because they have a narrow melting range, they require certain considerations
when acceptable welding procedures are being developed. When considered for fabrication, these alloys are
selected primarily for applications requiring superior
corrosion resistance, such as specialized chemical tanks
and piping, or excellent electrical conductivity, such as
for bus bar applications. These alloys have relatively
poor mechanical properties and usually would not be
considered for general structural applications. The
1XXX base alloys are often welded with a matching
filler metal chemistry or with filler alloys of the 4XXX
series, depending on application and performance
requirements. These alloys are not heat treatable and
have an ultimate tensile strength ranging from 69 MPa
to 186 MPa (10 ksi to 27 ksi).
2XXX Series. Alloys in the 2XXX series are the
aluminum-copper (Al-Cu) group, with copper additions ranging from 0.7% to 6.8%. The 2XXX series
high-strength alloys are often used for aerospace and
aircraft applications because they maintain excellent
strength over a wide range of temperatures. Some of
the alloys in the 2XXX series are not considered
weldable by arc welding processes because they are
susceptible to hot cracking and stress-corrosion
cracking; however, other alloys in this series can be
readily welded with arc processes when correct
procedures are used. As base metals, these alloys are
often welded with high-strength filler alloys in the
2XXX series, which are designed to match base-metal
performance characteristics. Depending on the
application and service requirements, however, they
can sometimes be welded with the filler metals in
the 4XXX series, which contain silicon (Si) or silicon
and copper. These alloys are heat treatable and have
an ultimate tensile strength ranging from 186 MPa to
AWS WELDING HANDBOOK
3XXX Series. The 3XXX series aluminummanganese (Al-Mn) alloys, with manganese additions
ranging from
0.05% to 1.8%, provide moderate strength, good
corrosion resistance, and excellent formability, and are
suited for use at elevated temperatures. One of the first
uses of alloys in this series was in the manufacturing of
kitchen utensils, pots, and pans; today these alloys are
the major component of heat exchangers in vehicles and
power plants. The moderate strength of these alloys,
however, often precludes consideration for structural
applications. These base alloys are welded with filler
alloys from the 1XXX, 4XXX, and 5XXX series,
depending on the specific chemistry, the particular
application, and service requirements. These alloys are
not heat treatable, and they have an ultimate tensile
strength of 110 MPa to 283 MPa (16 ksi to 41 ksi).
4XXX Series. Alloys in the 4XXX series, which consist
of aluminum-silicon (Al-Si) alloys where silicon
additions range from 0.6% to 21.5%), include both
heat-treatable and nonheat-treatable alloys. When
added to aluminum, silicon lowers the melting point,
and when melted, improves fluidity. Consequently, this
series of alloys is predominantly used as filler metals for
both fusion welding and brazing. Silicon, independently
in aluminum, is not heat treatable; however, a number
of the aluminum-silicon alloys have been designed to
incorporate additions of magnesium or copper, which
provide the ability to respond favorably to solution
heat-treatment. Typically, these heat-treatable filler
alloys are used only when a weldment is to be subjected
to postweld thermal treatments. Alloys in the 4XXX
series have ultimate tensile strengths ranging from
172 MPa to 379 MPa (25 ksi to 55 ksi).
5XXX Series. Alloys in the 5XXX series consist of
aluminum-magnesium (Al-Mg), with magnesium additions ranging from 0.2% to 6.2%; they have the highest
strength of the alloys that are not heat treatable. This
series of alloys is readily weldable and is used for a wide
variety of structural applications, such as components
of ships, vehicles, pressure vessels, bridges, and
buildings. Base alloys of aluminum-magnesium are
often welded with filler alloys, which are selected in
consideration of the magnesium content of the base
material, the application, and the intended service
conditions of the welded component.
Alloys in the 5XXX series that contain more than
3.0% magnesium are not recommended for service at
elevated temperatures (higher than 66°C [150°F])
because of the potential for sensitization and
subsequent susceptibility to stress-corrosion cracking.
Base alloys with less than approximately 2.5% magnesium are often welded successfully with filler metal
from the 4XXX or 5XXX series. The base alloy 5052
AWS WELDING HANDBOOK
content that can be welded with a filler metal made
from the 4XXX series.
Materials that have magnesium contents higher than
that of 5052 are generally welded only with 5XXX
series filler alloys that closely match the magnesium in
the base alloy material. These alloys are not heat
treatable; they have a tensile strength in the range of 124
MPa to 352 MPa (18 ksi to 51 ksi).
6XXX Series. The 6XXX series, consisting of aluminum-
magnesium-silicon (Al-Mg-Si) alloys (with magnesium
and silicon additions of around 1.0%), is widely used
throughout the welding fabrication industry. These
alloys are used predominantly in the form of extrusions
and are incorporated in many structural components.
The addition of magnesium and silicon to aluminum
produces a compound of magnesium-silicide that can
be solution heat-treated for improved strength. Alloys
in the 6XXX series are naturally sensitive to
solidification cracking, so autogenous welds (made
without filler metal) should not be used; filler metal is
required. The addition of adequate amounts of filler
metal during the arc welding process is essential to
provide dilution of the base metal, thereby
preventing the hot-cracking problem. The 6XXX
alloys are welded with filler metals from the 4XXX
and 5XXX series, with the selection depending on the
application and service requirements. These alloys are
heat treatable and have an ultimate tensile strength
in the range of 124 MPa to 400 MPa (18 ksi to 58
ksi).
7XXX Series. The 7XXX series consists of the aluminum-
zinc (Al-Zn) alloys, with zinc additions ranging from
0.8% to 12.0%. Alloys in this series are among the
highest-strength aluminum alloys; they are often used in
high-performance applications, such as aircraft and
aerospace components and competitive sports
equipment. Like the 2XXX alloy series, the 7XXX
series incorporates some alloys that are considered
unsuitable for arc welding and others that are often
welded successfully with an arc welding process. The
commonly welded base-metal alloys in this series,
such as 7003 and 7005, are predominantly welded
with filler alloys from the 5XXX series. These alloys are
heat treatable and have an ultimate tensile strength range
Principle Effects of Alloying Elements
Alloying elements are added to pure aluminum to
give the alloy unique characteristics, such as greater
strength, better ductility, and improved fluidity. The
effects of various alloys on the properties of aluminum
are discussed in this section.
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
5
2XXX Series, Copper. The aluminum-copper (Al-
Cu) alloys typically contain between 2% and 10%
copper, with smaller additions of other elements, but
the copper provides substantial increases in strength
and facilitates precipitation hardening. The introduction
of copper to aluminum may also reduce ductility and
corrosion
resistance.
The
susceptibility
of
aluminum-copper alloys to solidification cracking is
increased; consequently, some of these alloys may be
among the most challenging aluminum alloys to weld.
The 2XXX alloy series includes some of the higheststrength, heat-treatable aluminum alloys. The most
common applications for alloys in this series are in the
defense and aerospace industry, such as for
components of military vehicles and rocket fins.
3XXX Series, Manganese. The addition of manganese (Mn) to aluminum increases strength somewhat
through solution strengthening and improves strain
hardening (sometimes called work hardening or cold
working) while not appreciably reducing ductility or
corrosion resistance. These are moderate-strength, nonheat-treatable materials that retain strength at elevated
temperatures and are not generally used for major
structural applications. The most common applications
for alloys in the 3XXX series are the fabrication of
cooking utensils, radiators, air conditioning condensers,
evaporators, heat exchangers, and associated piping
systems.
4XXX Series, Silicon. The addition of silicon (Si) to
aluminum reduces the melting temperature and
improves fluidity. Silicon alone in aluminum produces
an alloy that cannot be heat treated; however, in combination with magnesium, it produces a precipitationhardening heat-treatable alloy. Consequently, both
heat-treatable and nonheat-treatable alloys are included
within the 4XXX series. Silicon additions to aluminum
are commonly used for castings, but the most common
applications for alloys in the 4XXX series are the manufacturing of welding filler metal electrodes produced
for the fusion welding and brazing of aluminum.
5XXX Series, Magnesium. The addition of magnesium (Mg) to aluminum increases strength through
solid-solution strengthening and improves the strainhardening properties. These alloys are the highest
strength, nonheat-treatable aluminum alloys available
and are used extensively for structural applications.
Alloys in the 5XXX series are produced primarily as
sheet and plate. They are used only occasionally as
extrusions because these alloys strain harden quickly
and are difficult and expensive to extrude. Alloys in the
5XXX series are commonly used in the construction of
truck and rail car bodies, buildings, armored vehicles,
6
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
ships and boats, chemical tankers, pressure vessels, and
cryogenic tanks.
6XXX Series, Magnesium and Silicon. The addition of magnesium (Mg) and silicon (Si) to aluminum
produces the compound magnesium-silicide (Mg2Si).
The formation of this compound makes it possible for
the 6XXX series to respond to heat treatment. Alloys in
the 6XXX series are easily and economically extruded
and for these reasons are used in an extensive selection
of extruded shapes. These alloys form an important
complementary system with alloys in the 5XXX series.
Aluminum plate in the 5XXX series and extruded
forms of alloys in the 6XXX series are commonly
joined. Typical applications for the 6XXX alloys are
handrails, drive shafts, automotive frame sections, bicycle
frames, tubular lawn furniture, scaffolding, stiffeners
and braces used on trucks, boats, and many other
structural fabrications.
7XXX Series, Zinc. The addition of zinc (Zn) to
aluminum (in combination with some other elements,
primarily magnesium or copper, or both) produces
heat-treatable aluminum alloys of high strength. The
zinc substantially increases strength and permits
precipitation hardening. Some of these alloys may be
susceptible to stress-corrosion cracking, and for this
reason they are not usually joined by fusion welding.
Other alloys in this series are often fusion welded
with excellent results. Common applications for alloys
in the 7XXX series include aerospace components,
armored vehicles, baseball bats, and bicycle frames.
Iron. Iron (Fe) is the most common impurity found in
aluminum and is intentionally added to some pure
alloys (1XXX series) to provide a slight increase in
strength.
Chromium. Chromium (Cr) is added to aluminum to con-
trol grain structure, to prevent grain growth in aluminummagnesium alloys, and to prevent recrystallization in
aluminum-magnesium-silicon or aluminum-magnesiumzinc alloys during heat treatment. Chromium will also
reduce susceptibility to stress corrosion and improve
toughness. It has a significant effect on electrical resistivity.
Nickel. Nickel (Ni) is added to aluminum-copper and
aluminum-silicon alloys to improve hardness and
strength at elevated temperatures and to reduce the
coefficient of expansion.
Titanium. Titanium (Ti) is added to aluminum primarily
as a grain refiner. The grain-refining effect of titanium
is enhanced if boron is present in the melt or if the
titanium is added as a master alloy containing boron
AWS WELDING HANDBOOK
(largely combined as Ti-B2). Titanium is a common
addition to aluminum filler metal because it refines the
weld structure and helps prevent weld cracking.
Zirconium. Zirconium (Zr) is added to aluminum to
form a fine precipitate of intermetallic particles that
inhibit recrystallization.
Lithium. The addition of lithium (Li) to aluminum
substantially increases strength, and relative to Young’s
modulus, provides precipitation hardening and
decreases density.
Lead and Bismuth. Lead (Pb) and bismuth (Bi) are
added to aluminum to assist in chip formation and to
improve machinability. These free-machining alloys are
often not weldable because the lead and bismuth
produce low-melting-point constituents that can
induce poor mechanical properties or high sensitivity
to cracking on solidification, or both.
Nonheat-Treatable Aluminum Alloys
The initial strength of the nonheat-treatable aluminum alloys depends primarily on the hardening effect of
alloying elements, such as silicon, iron, manganese, and
magnesium. These elements promote increases in
strength, either as dispersed phases or by solid-solution
strengthening. As shown in Table 1.2, the nonheattreatable alloys are mainly within the 1XXX, 3XXX,
4XXX, and 5XXX series, depending on the major
alloying elements.
Iron and silicon are the major impurities in commercially pure aluminum, but they add strength to alloys in
the 1XXX series. Silicon is the major element in many
welding and brazing filler alloys. Magnesium is the
most effective solution-strengthening element in the
nonheat-treatable alloys. Aluminum-magnesium alloys
in the 5XXX series have relatively high strength in the
annealed condition. The strength of all of the nonheattreatable alloys can be improved by strain hardening.
To remove the effects of strain hardening and
improve ductility, the nonheat-treatable alloys can be
annealed by heating to a uniform temperature in the
range of 340°C to 410°C (650°F to 775°F). The exact
annealing schedule will depend on the alloy.
Although the rate of cooling from the annealing temperature is not critical, fixturing may be required to
prevent distortion or warping. Basic temper designations applicable to the nonheat-treatable alloys are
shown in Table 1.3.
When fusion welded, the nonheat-treatable alloys
lose the effects of strain hardening in the narrow heataffected zone (HAZ) adjacent to the weld; the strength
in the HAZ will approach that of the annealed
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
7
Table 1.2
Composition and Typical Applications of Nonheat-Treatable Wrought Alloys
Aluminum
Association
Designation
Nominal Composition (% Alloying Element)
Cu
1060
1100
1350
3003
Mn
Mg
Cr
99.60% minimum aluminum
99.00% minimum aluminum
0.12
99.50% minimum aluminum
1.2
—
—
3004
5005
5050
5052, 5652
—
—
—
—
1.2
—
—
—
1.0
0.8
1.4
2.5
—
—
—
—
5083
—
0.7
4.4
0.15
5086
5154, 5254
—
—
0.45
—
4.0
3.5
0.15
0.25
5454
5456
—
—
0.8
0.8
2.7
5.1
0.12
0.12
Typical Applications
Chemical process equipment, tanks, piping.
Architectural and decorative applications, furniture, deep drawn parts, spun hollow
ware.
Electrical conductor wire, bus and cable.
General purpose applications where slightly higher strength than 1100 is required.
Process and food handling equipment, chemical and petroleum drums and tanks.
Sheet metal requiring higher strength than 3003.
Electrical conductor and architectural applications.
Similar to 3003 and 5005 but stronger. Has excellent finishing qualities.
Sheet metal applications requiring higher strength than 5050. Formable and good
corrosion resistance. Storage tanks, boats, appliances. Alloy 5652 has closer control
of impurities for H2O2 service.
Marine components, tanks, unfired pressure vessels, cryogenics structures, railroad
cars, drilling rigs.
Marine components, tanks, tankers, truck frames.
Unfired pressure vessels, tankers. Alloy 5254 has closer control of impurities for
H2O2 service.
Structural applications and tanks for sustained high-temperature service.
Structures, tanks, unfired pressure vessels, marine components.
Table 1.3
Basic Temper Designations Applicable to the Nonheat-Treatable Aluminum Alloys
Designation*
Description
-0
Annealed, recrystallized
-F
As fabricated
-H1
Strain hardened only
-H2
Strain hardened and then
partially annealed
-H3
Strain hardened and then
stabilized
Application
Applies to wrought products that are annealed to obtain the lowest strength temper, and to cast
products that are annealed to improve ductility and dimensional stability.
Applies to products of shaping processes in which no special control over thermal conditions or
strain hardening is employed. For wrought products, there are no mechanical property limits.
Applies to products that are strain hardened to obtain the desired strength without supplementary
thermal treatment. The number following this designation indicates the degree of strain hardening.
Applies to products that are strain hardened more than the desired final amount and then reduced
in strength to the desired level by partially annealing. For alloys that age soften at room temperature, the H2 tempers have the same minimum ultimate tensile strength as the corresponding H3
tempers. For other alloys, the H2 tempers have the same minimum ultimate tensile strength as
the corresponding H1 tempers and slightly higher elongation. The number following this designation indicates the degree of strain hardening remaining after the product has been partially
annealed.
Applies to products that are strain hardened and that have mechanical properties stabilized by a
low-temperature thermal treatment, which results in slightly lowered tensile strength and
improved ductility. This designation is applicable only to those alloys which, unless stabilized,
gradually age soften at room temperature. The number following this designation indicates the
degree of strain hardening before the stabilization treatment.
*The digit following the designation H1, H2, and H3 indicates the degree of strain hardening. Numeral 8 has been assigned to indicate tempers having an ultimate tensile strength equivalent to that achieved by a cold reduction of approximately 75% following a full anneal. Tempers between 0 (annealed) and 8 are
designated by numerals 1 through 7. Material having an ultimate tensile strength about midway between that of the 0 temper and that of the 8 temper is designated by the numeral 4; about midway between the 0 and 4 tempers by the numeral 2; and about midway between the 4 and 8 tempers by the numeral 6.
Numeral 9 designates tempers whose minimum tensile strength exceeds that of the 8 temper by 137.9 MPa (2.0 ksi) or more. For two-digit H tempers whose
second digit is odd, the standard limits for ultimate tensile strength are exactly midway between those of the adjacent two-digit H tempers whose second digits are even. The third digit, when used, indicates a variation of a two-digit temper. It is used when the degree of control of temper or the mechanical properties
are different from but close to those for the two-digit H temper designation to which it is added, or when some other characteristic is significantly affected.
8
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
condition. Table 1.4 contains information on process
selection and the relative weldability of common nonheat-treatable wrought aluminum alloys in various tempers. The physical properties of the same alloys are
shown in Table 1.5; the mechanical properties are
shown in Table 1.6.
Heat-Treatable Aluminum Alloys
The initial strength of aluminum alloys in the heattreatable group depends on the alloy composition, just
as it does in the nonheat-treatable alloys. Because elements such as copper, magnesium, zinc, and silicon,
either singularly or in various combinations, undergo a
significant increase in solid solubility in aluminum with
increasing temperature, it is possible to subject them to
thermal treatments that will impart pronounced
strengthening. Basic temper designations applicable to
the heat-treatable alloys are shown in Table 1.7.
Properties of heat-treatable aluminum alloys are
developed by solution heat-treating and quenching, followed by either natural or artificial aging. Cold working may add strength. The heat-treatable alloys can also
be annealed to achieve maximum ductility. This treatment involves holding the alloy at an elevated tempera-
ture and controlling the cooling rate to achieve
maximum softening.
The heat-treatable aluminum alloys are primarily in
the 2XXX, 6XXX, and 7XXX series, although some
alloys in the 4XXX series are heat treatable, depending
on the combination of alloying elements. Some of the
widely used heat-treatable alloys, nominal compositions, and general applications are listed in Table 1.8.
The comparative weldability of heat-treatable wrought
aluminum alloys is shown in Table 1.9.
The physical properties of heat-treatable wrought
aluminum alloys are provided in Table 1.10. Typical
mechanical properties of heat-treatable wrought aluminum alloys are listed in Table 1.11.
CAST ALUMINUM ALLOYS
Cast alloys are either nonheat-treatable or heat-treatable, based on the composition of the specific alloy, as
previously described for the wrought alloys. The cast
alloys also may be classified according to the casting
method for which the alloy is suitable, i.e., sand casting,
permanent-mold casting, or die casting. Table 1.12
shows the alloy designations for cast aluminum alloys.
Table 1.4
Compatibility Ratings for Welding, Brazing, and
Soldering of Nonheat-Treatable Wrought Aluminum Alloys1, 2
Aluminum
Alloy
Oxyfuel
Gas
Arc with
Flux
Arc with
Inert Gas
Resistance
Pressure
Brazing
Soldering
with Flux
1060
A
A
A
B
A
A
A
1100
A
A
A
A
A
A
A
1350
A
A
A
B
A
A
A
3003
A
A
A
A
A
A
A
3004
B
A
A
A
B
B
B
5005
A
A
A
A
A
B
B
5050
A
A
A
A
A
B
B
5052, 5652
A
A
A
A
B
C
C
5083
C
C
A
A
C
X
X
5086
C
C
A
A
B
X
X
5154, 5254
B
B
A
A
B
X
X
5454
B
B
A
A
B
X
X
5456
C
C
A
A
C
X
X
1. Weldability ratings are based on the most weldable temper:
A. Readily weldable.
B. Weldable in most applications; may require special technique or preliminary trials to establish welding procedures, performance, or
both.
C. Limited weldability.
X. This joining method is not recommended.
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
Table 1.5
Physical Properties of Non-Heat-Treatable Wrought Aluminum Alloys
Density
Aluminum
Alloy
1060
Approximate Melting Range
kg/m3
lb/in.3
°C
°F
W/(m·K)
BTU/(h·ft·°F)
Electrical
Conductivity
(% IACS) b
2699
0.0975
646–657
1195–1215
234
135
62
231
133
61
222
128
59
218
126
57
234
135
62
234
135
62
193
112
50
-H14
158
92
41
-H18
154
89
40
163
94
42
-H34
163
94
42
-H38
163
94
42
200
116
52
-H34
200
116
52
-H38
200
116
52
193
112
50
-H34
193
112
50
-H38
193
112
50
138
80
35
-H34
138
80
35
-H38
138
80
35
Temper
-0
-H18
1100
-0
2713
0.098
643–657
1190–1215
-H18
1350
-0
2699
0.0975
646–657
1195–1215
-H19
3003
3004
5005
5050
5052, 5652
Thermal Conductivitya
-0
-0
-0
-0
-0
2740
2713
2713
2685
2685
0.099
0.098
0.098
0.097
0.097
643–654
629–654
632–654
624–652
607–649
1190–1210
1165–1210
1170–1210
1155–1205
1125–1200
5083
-0
2657
0.096
574–638
1065–1180
117
68
29
5086
-0
2657
0.096
585–641
1085–1185
125
72
31
5154, 5254
-0
2657
0.096
593–643
1100–1190
125
72
32
-H12
125
72
32
-H34
125
72
32
-H38
125
72
32
134
77
34
-H32
134
77
34
-H34
134
77
34
117
68
29
5454
5456
-0
-0
2685
2657
0.097
0.096
602–646
568–638
1115–1195
1055–1180
a. Thermal conductivity at 25°C (77°F).
b. Percentage of International Annealed Copper Standard (IACS) value for Volume Electrical Conductivity, which equals 100% at 20°C (68°F).
9
10
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
Table 1.6
Typical Mechanical Properties of Non-Heat-Treatable Wrought Aluminum Alloys
Ultimate
Tensile Strength
Aluminum
Alloy
Temper
1060
-0
1100
-0
1350
-0
-H18
-H18
-H19
3003
3004
5005
5050
5052, 5652
5083
5086
5154, 5254
5454
5456
Yield Strength
(0.2% Offset)
Elongation % in
50.8 mm (2 in.)
ksi
MPa
ksi
69
10
28
4
131
19
124
18
—
90
13
34
5
45
166
24
152
22
15
83
12
28
4
23
186
27
166
24
—
1.5
Fatigue
Strengtha
MPa
ksi
MPa
ksi
Brinnell
Hardnessb
(500 kg load)
48
7
21
3
19
6
76
11
45
7
35
35
62
9
34
5
23
5
90
13
62
9
44
—
55
8
—
—
—
—
103
15
48
7
—
12.7 mm 1.6 mm
(0.500 in.) (0.062 in.)
Round
Sheet
MPa
Shear
Strength
43
-0
110
16
41
6
40
30
76
11
48
7
28
-H14
152
22
145
21
16
8
96
14
62
9
40
-H18
200
29
186
27
10
4
110
16
69
10
55
-0
179
26
69
10
25
20
110
16
96
14
46
-H34
241
35
200
29
12
9
124
18
103
15
63
-H38
283
41
248
36
6
5
145
21
110
16
77
-0
124
18
41
6
—
25
76
11
—
—
28
-H34
159
23
138
20
—
8
96
14
—
—
41
-H38
200
29
186
27
—
5
110
16
—
—
51
-0
145
21
55
8
—
24
103
15
83
12
36
-H34
193
28
166
24
—
8
124
18
90
13
53
-H38
221
32
200
29
—
6
138
20
96
14
63
-0
193
28
90
13
30
25
124
18
110
16
47
-H34
262
38
214
31
14
10
145
21
124
18
68
-H38
290
42
255
37
8
7
166
24
138
20
77
-0
290
42
145
21
22
—
172
25
—
—
—
-H116
317
46
228
33
16
—
—
—
159
23
—
-H321
317
46
228
33
16
—
—
—
159
23
—
-0
262
38
117
17
—
22
159
23
—
—
—
-H116
290
42
207
30
—
12
—
—
—
—
—
-H34
324
47
255
37
—
10
186
27
—
—
—
-0
241
35
117
17
—
27
152
22
117
17
58
-H112
241
35
117
17
—
25
—
—
117
17
63
-H34
290
42
228
33
—
13
166
24
131
19
73
-H38
331
48
269
39
—
10
193
28
145
21
80
-0
248
36
117
17
—
22
159
23
—
—
62
-H32
276
40
207
30
—
10
166
24
—
—
73
-H34
303
44
241
35
—
10
179
26
—
—
81
-0
310
45
159
23
24
—
—
—
—
—
—
-H112
310
45
166
24
22
—
—
—
—
—
—
-H116
352
51
255
37
16
—
207
30
—
—
90
a. Fatigue strength for round specimens and 500 million cycles.
b. 10 mm (0.40 in.) ball used.
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
11
Table 1.7
Basic Temper Designations Applicable to the Heat-Treatable Aluminum Alloys
Designation*
Description
Application
-0
Annealed
Applies to wrought products that are annealed to obtain the lowest strength temper, and to
cast products that are annealed to improve ductility and dimensional stability. The 0 may be
followed by a digit other than zero.
-F
As fabricated
Applies to products of shaping processes that employ no special control over thermal conditions or strain hardening. For wrought products, there are no mechanical property limits.
-W
Solution heat treated
An unstable temper applicable only to alloys that spontaneously age at room temperature
after solution heat treatment. This designation is specific only when the period of natural
aging is indicated, for example: W 0.5 h.
-T1
Cooled from an elevated-temperature shaping process and naturally aged to a substantially
stable condition. Applies to products that are not cold worked after cooling from an elevatedtemperature shaping process, or when the effect of cold work in flattening or straightening
may not be recognized in mechanical property limits.
-T2
Cooled from an elevated-temperature shaping process, cold worked, and naturally aged to a
substantially stable condition. Applies to products that are cold worked to improve strength
after cooling from an elevated-temperature shaping process, or when the effect of cold work
in flattening or straightening is recognized in mechanical property limits.
-T3
Solution heat treated, cold worked, and naturally aged to a substantially stable condition.
Applies to products that are cold worked to improve strength after solution heat treatment, or
when the effect of cold work in flattening or straightening is recognized in mechanical property
limits.
-T4
Solution heat treated and naturally aged to a substantially stable condition. Applies to products that are not cold worked after solution heat treatment, or when the effect of cold work in
flattening or straightening may not be recognized in mechanical property limits.
-T5
Cooled from an elevated-temperature shaping process and then artificially aged. Applies to
products that are not cold worked after cooling from an elevated-temperature shaping process,
or when the effect of cold work in flattening or straightening may not be recognized in
mechanical property limits.
-T6
Solution heat treated and stabilized. Applies to products that are not cold worked after
solution heat treatment, or when the effect of cold work in flattening or straightening may not
be recognized in mechanical property limits.
-T7
Solution heat treated and stabilized. Applies to products that are stabilized after solution heat
treatment to carry them beyond the point of maximum strength to provide control of some
special characteristic.
-T8
Solution heat treated, cold worked, and then artificially aged. Applies to products that are cold
worked to improve strength, or when the effect of cold work in flattening or straightening is
recognized in mechanical property limits.
-T9
Solution heat treated, artificially aged, and then cold worked. Applies to products that are cold
worked to improve strength.
-T10
Cooled from an elevated-temperature shaping process, cold worked, and then artificially
aged. Applies to products that are cold worked to improve strength, or when the effect of cold
work in flattening or straightening is recognized in mechanical property limits.
*Additional digits, the first of which shall not be zero, may be added to designation T1 through T10 to indicate a variation in treatment which significantly
alters the characteristics of the product.
12
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
Table 1.8
Composition and Typical Applications of Heat-Treatable Wrought Aluminum Alloys
Nominal Composition (% Alloying Element)
a.
b.
c.
d.
e.
f.
g.
Base
Alloy
Cu
Si
Mn
Mg
Zn
Ni
Cr
2014
4.4
0.8
0.8
0.50
—
—
—
Structures, structural and hydraulic fittings, hardware,
and heavy-duty forgings for aircraft or automotive uses.
2017
4.0
0.50
0.7
0.6
—
—
—
Same as 2014; screw machine parts.
2024
4.4
—
0.6
1.5
—
—
—
Structural, aircraft sheet construction, truck wheels;
often clad for strength with good corrosion resistance
2036
2.6
—
0.25
0.45
—
—
—
Automotive body sheet.
2090a
2.7
—
—
—
—
—
—
Structural; high strength and damage tolerant aerospace
applications.
2218
4.0
—
—
1.5
—
2.0
—
Forging alloy; engine cylinder heads, pistons, parts
requiring good strength and hardness at elevated
temperature.
2219b
6.3
—
0.30
—
—
—
—
Structural; high-temperature strength; aerospace tanks;
good weldability.
2519c
5.8
—
0.30
0.17
0.06
—
—
Structural; high-strength armor.
2618d
2.3
0.18
—
1.6
—
1.0
—
Same as 2218.
6005
—
0.8
—
0.50
—
—
—
Structural and architectural.
Typical Applications
6009
0.40
0.8
0.50
0.6
0.25
—
0.10
Automotive body sheet.
6010
0.40
1.0
0.50
0.8
0.25
—
0.10
Automotive body sheet.
6013
0.9
0.25
0.35
0.95
—
—
—
General structural applications, improved strength over
6061.
6061
0.25
0.6
—
1.0
—
—
0.20
Structural, architectural, automotive, railway, and
marine applications; pipe and pipe fittings; good
formability, weldability, corrosion resistance, strength.
6063
—
0.40
—
0.7
—
—
—
6070
—
1.4
—
0.8
—
—
—
Structural applications; piping.
6101
0.50
—
—
0.6
—
—
—
Electrical conductors.
6262e
0.28
—
—
1.0
—
—
0.09
6351
—
1.0
0.6
0.6
—
—
—
Same as 6061.
6951
—
0.35
—
0.6
—
—
—
Brazing sheet core alloy.
7004f
—
—
—
1.5
4.2
—
—
Truck trailer, railcar extruded shapes.
7005g
—
—
0.45
1.4
4.5
—
0.13
Truck trailer, railcar extruded shapes.
Pipe, railings, hardware, architectural applications.
Screw machine products, fittings.
7039
—
—
0.30
2.8
4.0
—
0.20
Armor plate; military bridges.
7075
1.6
—
—
2.5
5.6
—
0.23
High-strength aircraft and other applications; cladding
gives good corrosion resistance.
7079
0.6
—
—
3.3
4.3
—
0.20
Strongest aluminum alloy where section thickness
exceeds 76.2 mm (3 in.), large and massive parts for
aircraft and allied construction.
7178
2.0
—
—
2.8
6.8
—
0.23
Aircraft construction; slightly higher strength than 7075.
Also 2.2 Li and 0.12 Zr.
Also 0.06 Ti, 0.10 V, and 0.18 Zr.
Also 0.06 Ti 0.17 Zr, and 0.10 Va.
Also 1.1 Fe and 0.07 Ti.
Also 0.6 Pb and 0.6 Bi.
Also 0.15 Zr.
Also 0.15 Zr and 0.035 Ti.
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
13
Table 1.9
Compatibility Ratings for Welding, Brazing, and
Soldering of Heat-Treatable Wrought Aluminum Alloys1, 2
Aluminum
Alloy
Oxyfuel
Gas
Arc with
Flux
Arc with
Inert Gas
Resistance
Pressure
Brazing
Soldering
with Flux
2014
X
C
C
B
C
X
C
2017
X
C
C
B
C
X
C
2024
X
C
C
B
C
X
C
2036
X
C
B
B
C
X
C
2090
X
X
B
B
C
X
C
2218
X
C
C
B
C
X
C
C
2219
X
C
A
B
C
X
2519
X
C
B
B
C
X
C
2618
X
C
C
B
C
X
C
6005
A
A
A
A
B
A
B
6009
C
C
B
B
B
X
C
6010
C
C
B
B
B
X
C
6013
C
C
B
A
B
X
C
6061
A
A
A
A
B
A
B
6063
A
A
A
A
B
A
B
6070
C
C
B
B
B
X
C
6101
A
A
A
A
A
A
A
6262
C
C
B
A
B
B
B
6351
A
A
A
A
B
A
B
6951
A
A
A
A
A
A
A
7004
X
X
A
A
B
B
B
7005
X
X
A
A
B
B
B
B
7039
X
X
A
A
B
C
7075
X
X
C
B
C
X
C
7079
X
X
C
B
C
X
C
7178
X
X
C
B
C
X
C
1. Weldability ratings are based on the most weldable temper:
A. Readily weldable.
B. Weldable in most applications; may require special technique or preliminary trials to establish welding procedures, performance, or
both.
C. Limited weldability.
X. This joining method is not recommended.
Detailed information for cast aluminum alloys is provided in tabular form as follows:
Table 1.13 shows the composition, casting method,
and typical applications of nonheat-treatable cast
aluminum alloys.
Table 1.14 shows the composition, casting method,
and typical applications for heat-treatable cast
aluminum alloys.
Table 1.15 shows the comparative weldability of nonheat-treatable cast aluminum alloys for various
joining processes.
Table 1.16 shows the physical properties of nonheattreatable cast aluminum alloys;
Table 1.17 lists typical mechanical properties of nonheat-treatable cast aluminum alloys.
Table 1.18 shows heat-treatable cast aluminum alloys
and joining process selection.
14
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
Table 1.10
Physical Properties of Heat-Treatable Wrought Aluminum Alloys
Aluminum
Alloy
2014
2017
2024
2036
2090
2218
2219
2519
2618
6005
6009
6010
6013
6061
6063
6070
6101
6262
6351
6951
7004
7005
7039
7075
7079
7178
Approximate
Melting Range
Density
Temper
kg/m3
lb/in.3
°C
°F
-0
-T4
-T6
-0
-T4
-0
-T3
-T4
-T361
-T4
-T8
-T72
-0
-T31
-T62
-T81
-T87
-T87
-T61
-T1
-T5
-T4
-T4
-T4
-T6
-0
-T4
-T6
-0
-T1
-T5
-T6
-T6
-H111
-T6
-T9
-T5
-T6
-0
-F6
-T5
-T6
-T53
-T64
-0
-T6
-T73
-0
-T6
-0
-T6
2796
0.101
507–638
945–1180
2796
0.101
513–641
955–1185
2796
0.101
502–638
935–1180
2768
2574
2796
2851
0.100
0.093
0.101
0.103
554–649
561–589
507–638
543–643
1030–1200
1042–1091
945–1180
1010–1190
2823
2768
2685
0.102
0.100
0.097
554–643
549–638
607–654
1030–1190
1020–1180
1125–1210
2713
2713
2713
0.098
0.098
0.098
560–649
560–649
579–649
1040–1200
1040–1200
1075–1200
2713
0.098
582–652
1080–1205
2685
0.097
616–655
1140–1210
2713
2685
0.098
0.097
566–649
621–654
1050–1200
1150–1210
2713
2713
0.098
0.098
582–652
596–652
1080–1205
1105–1205
2713
0.098
616–654
1040–1210
2768
0.100
—
—
2768
2740
2796
0.100
0.099
0.101
607–646
577–638
477–635
1125–1195
1070–1180
890–1175
2740
0.099
482–638
900–1180
2823
0.102
477–629
890–1165
Thermal Conductivitya
W/(m·K)
77.5
112
89
77.5
112
70
112
70
70
159
88
154
99
65
70
70
70
133
150
109
104
167
150
86.7
94
89
104
96.7
112
126
121
116
172
—
126
172
102
102
114
114
—
198
—
154
75
BTU /(ft·h·°F)
Electrical
Conductivity
(% IACS)b
193
134
154
193
134
193
121
121
121
92
51
89
172
112
121
121
121
76.7
86.7
180
189
96.7
86.7
150
163
180
154
167
218
193
209
200
99
—
218
99
176
176
198
198
—
114
—
89
99
56
52
—
52
—
34
87
125
72.5
32
—
—
—
31
a. Thermal conductivity at 25°C (77°F).
b. Percentage of International Annealed Copper Standard (IACS) value for Volume Electrical Conductivity, which equals 100% at 20°C (68°F).
50
34
40
50
34
50
30
30
30
41
17
40
44
28
30
30
30
33
39
47
49
44
39
38
42
47
40
43
58
50
55
53
44
—
57
44
46
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
15
Table 1.11
Typical Mechanical Properties of Heat-Treatable Wrought Aluminum Alloys
Ultimate Tensile
Strength
Aluminum
Alloy
Temper
2014
2017
2024
MPa
ksi
-0
186
-T4
428
-T6
Yield Strength
(0.2% Offset)
% Elongation in
50.8 mm (2 in.)
1.6 mm
12.7 mm
(0.062 in.) (0.500 in.)
Sheet
Round
MPa
ksi
27
96
14
—
62
290
42
—
483
70
414
60
-0
180
26
69
-T4
428
62
276
-0
186
27
76
11
-T3
483
70
345
-T4
469
68
324
-T361
496
72
393
Shear Strength
Fatigue Strengtha
Brinnell
Hardnessb
(500 kg load)
MPa
ksi
MPa
ksi
18
124
18
20
262
38
138
89.6
13
45
20
105
—
13
290
42
124
18
135
10
—
22
124
18
40
—
22
262
38
20
22
124
18
50
18
—
283
41
138
20
120
47
20
19
283
41
13 8
20
120
57
13
—
290
42
124
18
120
24
89.6
124
89.6
13
45
18
105
13
45
2036
-T4
338
49
193
28
—
—
—
124
18
—
2090
-T8
538
78
496
72
7.5
6
—
—
—
—
—
2218
-T72
331
48
255
37
—
11
207
30
—
—
95
2219
-0
172
25
76
11
18
—
—
—
—
—
—
-T31
358
52
248
36
17
—
—
—
—
—
—
-T62
414
60
290
42
10
—
—
—
103
15
—
-T81
455
66
352
51
10
—
—
—
103
15
—
-T87
476
69
393
57
10
—
—
—
103
15
—
2519
-T87
496
72
441
64
10
—
303
44
189
28
132
2618
-T61
441
64
372
54
—
10
262
38
124
18
115
6005
-T1
193
28
124
18
—
18
—
—
—
—
—
-T5
303
44
269
39
—
12
179
26
—
—
—
6009
-T4
228
33
124
18
25
—
152
22
117
17
—
6010
-T4
290
42
172
25
24
—
193
28
124
18
—
6013
-T4
296
43
159
23
22
—
—
—
—
—
—
-T6
407
59
372
54
9
—
234
34
—
—
—
-0
124
18
55
8
25
30
83
12
62.1
9
30
-T4
241
35
145
21
22
25
166
24
96.5
14
65
-T6
310
45
276
40
12
17
207
30
96.5
14
95
-0
90
13
48
7
—
69
10
55.2
8
25
-T1
152
22
90
13
20
—
96
14
62.1
9
42
-T5
186
27
145
21
12
—
117
17
68.9
10
60
31
12
—
—
22
68.9
10
73
10
—
234
34
96.5
14
—
—
—
—
—
—
—
—
138
20
—
—
71
6061
6063
-T6
6070
-T6
6101
-H111
-T6
35
379
55
352
51
96
14
76
11
221
32
193
28
—
—
15
(Continued)
16
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
Table 1.11 (Continued)
Typical Mechanical Properties of Heat-Treatable Wrought Aluminum Alloys
Ultimate Tensile
Strength
Aluminum
Alloy
Temper
Yield Strength
(0.2% Offset)
MPa
ksi
MPa
ksi
% Elongation in
50.8 mm (2 in.)
1.6 mm
12.7 mm
(0.062 in.) (0.500 in.)
Sheet
Round
Shear Strength
Fatigue Strengtha
MPa
ksi
MPa
ksi
Brinnell
Hardnessb
(500 kg load)
6262
-T9
400
58
379
55
—
10
241
35
89.6
13
120
6351
-T5
310
45
283
41
—
12
186
27
—
—
—
-T6
331
48
310
45
—
11
186
27
—
—
—
-0
110
16
6
30
—
76
11
—
—
28
-T6
269
39
228
33
13
—
179
26
—
—
82
7004
-T5
393
57
331
48
—
—
234
34
—
—
—
7005
-T53
365
53
324
47
—
12
207
30
—
—
—
7039
-T64
448
65
379
55
13
10
262
38
—
—
120
7075
-0
228
33
103
15
17
16
152
22
—
—
60
-T6
572
83
503
73
11
11
331
48
159
23
150
-T73
503
73
434
63
—
13
303
44
152
22
—
7079
-0
228
33
103
15
17
16
—
—
—
—
—
-T6
538
78
469
68
—
14
310
45
159
23
145
7178
-0
228
33
103
15
15
16
152
22
—
—
60
-T6
607
88
538
78
10
11
358
52
152
22
160
6951
41.4
a. Fatigue strength for round specimens and 500 million cycles.
b. 10 mm (0.40 in.) ball used.
Table 1.12
Designations for Cast Aluminum Alloy Groups
Aluminum, 99.00% and greater
1XX.X
Major Alloying Element
Copper
Silicon, with added Copper, Magnesium, or both
Silicon
Magnesium
Zinc
Tin
Other Element
Unused series
2XX.X
3XX.X
4XX.X
5XX.X
7XX.X
8XX.X
9XX.X
6XX.X
For the 1XX.X series, The first digit indicates the alloy group. The second two
digits identify the minimum aluminum percentage. For all castings, the last
digit, which is separated from the others by a decimal point, indicates the
product form. Castings are indicated by XXX.0. Ingot types are indicated by
XXX.1 and XXX.2. A modification of the original alloy or impurity limits is
indicated by a serial letter before the numerical designation. The serial letters
are assigned in alphabetical sequence starting with “A.” “X” is reserved for
experimental alloys.
Table 1.19 shows the comparative weldability of heattreatable cast aluminum alloys for various joining
processes.
Table 1.20 lists the physical properties of heat-treatable
cast aluminum alloys.
FILLER METALS AND FILLER METAL
SELECTION
A fundamental difference between the arc welding of
steel and the arc welding of aluminum is the evaluation
method used during the filler metal selection process.
Many aluminum base metals can be welded successfully
with any number of different filler metals. As an example, the base metal 6061-T6 is commonly welded with
at least four very different filler metals and can be
welded successfully with even more.
(Continued on page 25)
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
17
Table 1.13
Composition, Casting Type, and Typical Applications of Nonheat-Treatable Cast Aluminum Alloys
Nominal Composition
(% Alloying Element)
Suitable Types of Castings
Cu
Si
Mg
Zn
Sand
Permanent
Mold
Die
Typical Applications
208.0
4.0
3.0
—
—
X
X
—
General-purpose alloy; manifolds, valve housings,
and applications requiring pressure tightness.
213.0
7.0
2.0
—
—
X
X
—
—
238.0
10.0
4.0
0.25
—
—
X
—
High as-cast hardness. Sole plates for electric hand
irons.
360.0
—
9.5
0.5
—
—
—
X
General-purpose die castings, cover plates, and
instrument cases. Excellent casting characteristics.
380.0
3.5
8.5
—
—
—
—
X
General purpose. Good casting characteristics and
mechanical properties.
413.0
—
12.0
—
—
—
—
X
General-purpose die casting alloy for large, intricate
parts with thin sections, as typewriter frames,
instrument cases, etc. Excellent casting characteristics;
very good corrosion resistance.
443.0
A443.0
B443.0
0.6 max.
0.3 max.
0.15 max.
5.25
5.25
5.25
—
—
—
—
—
—
X
X
X
X
X
X
—
—
—
General-purpose alloy, cooking utensils, pipe fittings,
architectural and marine applications. Excellent
castability and pressure tightness.
A444.0
—
7.0
X
—
Structural applications (AASHTO)
511.0
—
0.5
4.0
—
X
—
—
Anodically treated architectural parts and ornamental
hardware. Takes uniform anodic finish.
512.0
—
1.8
4.0
—
X
—
—
Cooking utensils and pipe fittings.
513.0
—
—
4.0
1.8
X
—
Cooking utensils and ornamental hardware; takes
uniform anodic finish.
514.0
—
—
4.0
—
—
—
Chemical process fittings, special food-handling
equipment, and marine hardware. Excellent corrosion
resistance.
518.0
—
—
8.0
—
—
X
Marine fittings and hardware. High strength, ductility,
and resistance to corrosion.
535.0a
—
—
6.9
—
X
—
—
High welded strength and ductility.
710.0
0.5
—
0.7
6.5
X
—
—
General-purpose sand castings for subsequent
brazing. Good machinability.
711.0b
0.5
—
0.35
6.5
X
—
Torque converter blades and brazed parts. Good
machinability.
712.0c
—
—
0.6
5.8
—
—
Same as 710.0 above, good corrosion resistance.
Base Alloy
a. Also 0.18 Mn, 18 Ti, and 0.005 Be.
b. Also 1.0 Fe.
c. Also 0.5 Cr.
—
X
X
18
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
Table 1.14
Composition, Casting Type, and Typical Applications of Heat-Treatable Cast Aluminum Alloys
Nominal Composition (% Alloying Element)
Suitable Types
of Castings (X)
Base Alloy
Cu
Si
Mg
Ni
Sand
Permanent
Mold
A201.0a
4.5
—
0.25
—
X
—
—
222.0
10.0
—
0.25
—
X
X
Bushings, bearing caps, meter parts, and air-cooled cylinder
heads. Retains strength at elevated temperatures.
240.0b
8.0
—
6.0
0.50
X
—
—
242.0
4.0
—
1.5
2.0
X
X
Heavy-duty pistons and air-cooled cylinder heads. Good
strength at elevated temperatures.
A242.0c
4.1
—
1.5
2.0
X
—
Heavy-duty pistons and air-cooled cylinder heads. Good
strength at elevated temperatures.
295.0
4.5
1.1
—
—
X
—
Machinery and aircraft structural members, crankcases,
and wheels.
319.0
3.5
6.0
—
—
X
X
General purpose, engine parts, automobile cylinder
heads, piano plates.
332.0d
3.0
9.5
1.0
—
—
X
Automotive pistons. Good properties at elevated operating
temperatures.
333.0
3.5
9.0
0.30
—
—
X
Engine parts, gas meter housing, regulator parts, and
general purpose.
336.0
1.0
12.0
1.0
2.5
—
X
Heavy-duty diesel pistons. Good strength at elevated
temperatures.
354.0
1.8
9.0
0.50
—
—
X
Aircraft, missile, and other applications requiring premiumstrength castings.
355.0
1.3
5.0
0.50
—
X
X
General-purpose castings, crankcases, accessory housings,
and aircraft fittings.
C355.0
1.3
5.0
0.50
—
X
X
Aircraft, missile, and other structural applications requiring
high strength.
356.0
—
7.0
0.35
—
X
X
General-purpose castings, transmission cases, truck-axle
housings and wheels, cylinder blocks, railway tank-car
fittings, marine hardware, bridge railing parts, architectural
uses.
A356.0
—
7.0
0.35
—
X
X
Aircraft, missile, and other structural applications and
aircraft fittings.
A357.0e
—
7.0
0.55
—
X
X
Aircraft, missile, and other structural applications requiring
high strength.
359.0
—
9.0
0.6
—
X
X
Aircraft, missile, and other structural applications requiring
high strength.
520.0
—
—
10.0
—
X
—
Sand castings requiring strength and shock resistance,
such as aircraft structural members. Excellent corrosion
resistance. Not recommended for use over 121°C (250°F).
a.
b.
c.
d.
e.
Also 0.7 Ag, 0.30 Mn, and 0.25 Ti.
Also 0.5 Mn.
Also 0.20 Cr.
Also 1.0 Zn.
Also 0.05 Be.
Typical Applications
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
Table 1.15
Compatibility Ratings for Welding, Brazing, and
Soldering of Nonheat-Treatable Cast Aluminum Alloys1, 2
Aluminum
Alloy
Oxyfuel
Gas
Arc with
Flux
Arc with
Inert Gas
Resistance
Pressure
Brazing
Soldering
with Flux
Sand Castings
208.0
C
C
B
B
X
X
C
213.0
C
C
B
B
X
X
C
430.0
A
A
A
A
X
C
C
443.0
A
A
A
A
X
C
C
A443.0
A
A
A
A
X
C
C
B443.0
A
A
A
A
X
C
C
511.0
X
X
A
A
X
C
C
512.0
X
X
B
B
X
C
C
514.0
X
X
A
A
X
C
C
535.0
X
X
A
A
X
X
C
710.0
C
C
B
B
X
A
B
712.0
C
C
A
B
X
A
B
Permanent Mold Castings
208.0
C
C
B
B
X
X
C
213.0
C
C
B
B
X
X
C
238.0
C
C
B
A
X
X
C
443.0
A
A
A
A
X
C
C
B443.0
A
A
A
A
X
C
C
A444.0
B
B
A
A
X
C
C
513.0
X
X
A
A
X
C
C
711.0
C
C
A
A
X
A
C
Die Castings
360.0
C
X
C
B
X
X
X
380.0
C
X
C
B
X
X
X
413.0
C
C
C
B
X
X
X
518.0
X
X
C
B
X
X
X
1. Weldability ratings are based on the most weldable temper:
A. Readily weldable.
B. Weldable in most applications; may require special technique or preliminary trials to establish welding procedures, performance, or
both.
C. Limited weldability.
X. This joining method is not recommended.
19
20
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
Table 1.16
Physical Properties of Nonheat-Treatable Aluminum Alloys
Density
Aluminum
Alloyc
kg/m3
Approximate Melting Range
lb/in.3
°C
°F
Thermal Conductivity a, c
W/(m·K)
BTU/(ft·h·°F)
Electrical
Conductivity
(% IACS) b, c
Sand Castings
208.0
2796
0.101
521–632
970–1170
121
70
31
213.0
2934
0.106
518–627
965–1160
121
70
30
430.0
2685
0.097
577–632
1070–1170
146
84
37
A443.0
2685
0.097
577–632
1070–1170
146
84
37
B443.0
2685
0.097
577–632
1070–1170
146
84
37
511.0
2658
0.096
588–638
1090–1180
141
82
36
512.0
2658
0.096
588–632
1090–1170
146
84
38
514.0
2658
0.096
599–638
1110–1180
137
79
35
535.0
2519
0.091
549–632
1020–1170
100
58
23
710.0
2823
0.102
599–649
1110–1200
137
79
35
712.0
2823
0.102
599–638
1110–1180
158
92
40
Permanent Mold Castings
208.0
2796
0.101
521–632
970–1170
121
70
31
213.0
2934
0.106
518–627
965–1160
121
70
30
238.0
2962
0.107
510–599
950–1110
104
60
25
443.0
2685
0.097
577–632
1070–1170
146
84
37
B443.0
2685
0.097
577–632
1070–1170
146
84
37
A444.0
2685
0.097
577–632
1070–1170
158
92
41
513.0
2685
0.097
583–638
1080–1180
133
77
34
711.0
2851
0.103
599–644
1110–1190
158
92
40
Die Castings
360.0
2685
0.097
515–588
960–1090
146
84
37
380.0
2740
0.099
521–588
970–1090
108
62
27
413.0
2658
0.096
577–588
1070–1090
154
89
39
518.0
2519
0.091
538–621
1000–1150
100
58
24
a. Thermal conductivity at 25°C (77°F).
b. Percentage of International Annealed Copper Standard (IACS) value for Volume Electrical Conductivity, which equals 100% at 20°C (68°F).
c. All casting alloys are in the “F” temper.
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
21
Table 1.17
Typical Mechanical Properties of Nonheat-Treatable Cast Aluminum Alloys
Ultimate Tensile
Strength
Aluminum
Alloy
Temper
MPa
ksi
Yield Strength
(0.2% Offset)
MPa
ksi
Elongation % in
50.8 mm (2 in.)
12.7 mm (0.500 in.)
Diameter Round
Shear Strength
Fatigue Strengtha
MPa
ksi
MPa
ksi
Brinnell
Hardness
(500 kg load)b
Sand Castings
208.0
F
145
21
96
14
2.5
117
17
76
11
55
213.0
F
166
24
103
15
1.5
138
20
62
9
70
430.0
F
131
19
55
8
8.0
96
14
55
8
40
A443.0
F
131
19
55
8
8.0
96
14
55
8
40
B443.0
F
131
19
55
8
8.0
96
14
55
8
40
511.0
F
145
21
83
12
3.0
117
17
55
8
50
50
512.0
F
138
20
90
13
2.0
117
17
59
8.5c
514.0
F
172
25
83
12
9.0
138
20
48
7
50
535.0
F
248
36
124
18
9.0
—
—
—
—
65
710.0c
F
241
35
172
25
5.0
179
26
55
8
75
712.0c
F
241
35
172
25
5.0
179
26
62
9
75
13
70
Permanent Mold Castings
208.0
F
193
28
110
16
2.0
152
22
90
213.0
F
207
30
166
24
1.5
166
24
66
9.5
238.0
F
207
30
166
24
1.5
166
24
—
—
100
443.0
F
159
23
62
9
10.0
110
16
55
8
45
B443.0
F
159
23
62
9
10.0
110
16
55
8
45
A444.0
F
241
35
124
18
8.0
—
—
76
11
70
513.0
F
186
27
110
16
7.0
152
22
69
10
60
711.0c
F
241
35
124
18
8.0
—
—
76
11
70
85
Die Castings
360.0
F
324
47
172
25
3.0
307
30
131
19
75
380.0
F
331
48
166
24
3.0
214
31
145
21
80
413.0
F
296
43
145
21
2.5
193
28
131
19
80
518.0
F
310
45
186
27
8.0
200
29
138
20
80
a. Fatigue strength for round specimens and 500 million cycles.
b. 10 mm (0.40 in.) ball used.
c. Tests made approximately 30 days after casting.
22
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
Table 1.18
Compatibility Ratings for Welding, Brazing, and Soldering of Heat-Treatable Cast Aluminum Alloys1, 2
Aluminum
Alloy
Oxyfuel
Gas
Arc with
Flux
Arc with
Inert Gas
Resistance
Pressure
Brazing
Soldering
with Flux
Sand Castings
A201.0
C
C
B
B
X
X
C
222.0
X
C
B
B
X
X
X
240.0
X
X
C
B
X
X
X
242.0
X
X
C
B
X
X
X
A242.0
X
X
C
B
X
X
X
295.0
C
C
B
B
X
X
X
319.0
C
C
B
B
X
X
X
355.0
B
B
B
B
X
X
X
C355.0
B
B
B
B
X
X
X
356.0
A
A
A
A
X
C
C
A356.0
A
A
A
A
X
C
C
A357.0
B
B
A
A
X
C
C
359.0
B
B
A
A
X
C
C
520.0
X
X
B
C
X
X
X
Permanent Mold Castings
222.0
X
C
B
B
X
X
X
242.0
X
X
C
B
X
X
X
319.0
C
C
B
B
X
X
X
332.0
X
X
B
B
X
X
X
333.0
X
X
B
B
X
X
X
336.0
C
C
B
B
X
X
X
354.0
C
C
B
B
X
X
X
355.0
B
B
B
B
X
X
X
C355.0
B
B
B
B
X
X
X
356.0
A
A
A
A
X
C
C
A356.0
A
A
A
A
X
C
C
A357.0
B
B
A
A
X
C
C
359.0
B
B
A
A
X
C
C
1. Weldability ratings are based on the most weldable temper:
A. Readily weldable.
B. Weldable in most applications; may require special technique or preliminary trials to establish welding procedures and
performance.
C. Limited weldability.
X. This joining method is not recommended.
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
23
Table 1.19
Typical Mechanical Properties of Heat-Treatable Cast Aluminum Alloys
Ultimate Tensile
Strength
Aluminum
Alloy
Temper
MPa
ksi
Yield Strength
(0.2% Offset)
MPa
ksi
Elongation % in
50.8 mm (2 in.)
12.7 mm (0.500 in.)
Diameter Round
Shear Strength
Fatigue Strengtha
MPa
ksi
MPa
ksi
Brinnell
Hardness
(500 kg load)b
290
221
—
166
179
—
179
228
166
200
152
193
193
—
138
179
166
—
276
—
234
42
32
—
24
26
—
26
33
24
29
22
28
28
—
20
26
24
—
40
—
34
—
59
—
72
76
—
48
55
76
76
55
62
69
—
55
59
62
—
83
—
55
—
8.5
—
10.5
11
—
7
8
11
11
8
9
10
—
8
8.5
9
—
12
—
8
130
115
90
75
85
—
60
90
80
80
65
80
85
85
60
70
75
75
85
—
75
179
207
241
—
—
186
228
193
193
248
276
234
221
207
172
193
241
—
26
30
35
—
—
27
33
28
28
36
40
34
32
30
25
28
35
—
62
72
66
—
—
83
103
83
93
—
—
69
96
80
76
90
103
110
9
10.5
9.5
—
—
12
15
12
13.5
—
—
10
14
13
11
13
15
16
140
105
110
95
105
100
105
90
105
125
110
90
100
80
70
90
100
—
Sand Castings
A201.0
222.0
240.0
242.0
A242.0
295.0
319.0
355.0
C355.0
356.0
A356.0
A357.0
359.0
520.0
-T6
-T61
-F
-T77
-7571
-T75
-T4
-T62
-T5
-T6
-T51
-T6
-T7
-T6
-T51
-T6
-T7
-T6
-T6
-T6
-T4
448
283
234
207
221
214
221
283
207
248
193
241
262
269
172
228
234
276
317
—
331
65
41
34
30
32
31
32
41
30
36
28
35
38
39
25
33
34
40
46
—
48
379
276
193
159
207
—
110
221
179
166
159
172
179
200
138
166
207
207
248
—
179
55
40
28
23
30
—
16
32
26
24
23
25
26
29
20
24
30
30
36
—
26
8.0
<0.5
1.0
2.0
0.5
2.0
8.5
2.0
1.5
2.0
1.5
3.0
0.5
5.0
2.0
3.5
2.0
6.0
3.0
—
16.0
Permanent Mold Castings
222.0
242.0
319.0
332.0
333.0
336.0
354.0
355.0
C355.0
356.0
A356.0
A357.0
359.0
-T65
-T571
-T61
-T6
-T5
-T5
-T6
-T7
-T551
-T65
-T62
-T6
-T61
-T6
-T7
-T61
-T6
-T62
331
276
324
276
248.
234
290
255
248
324
393
290
317
262
221
283
358
345
48
40
47
40
36
34
42
37
36
47
57
42
46
38
32
41
52
50
248
234
290
186
193
172
207
193
193
296
317
186
234
186
234
207
310
290
36
34
42
27
28
25
30
28
28
43
46
27
34
27
24
30
45
42
a. Fatigue strength for round specimens and 500 million cycles.
b. 10 mm (0.40 in.) ball used.
<0.5
1.0
0.5
3.0
1.0
1.0
1.5
2.0
0.5
0.5
3.0
4.0
6.0
5.0
6.0
10.0
5.0
5.5
24
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
Table 1.20
Physical Properties of Heat-Treatable Cast Aluminum Alloys
Density
Aluminum
Alloy
Temper
kg/m3
lb/in.3
°C
Thermal Conductivitya
°F
W/(m·K)
BTU/(ft·hr·°F)
Electrical
Conductivity
(% IACS)b
Approximate Melting Range
Sand Castings
A201.0
-T6
2796
0.101
571–649
1060–1200
1452
840
30
222.0
-T61
2962
0.107
521–627
970–1160
1539
890
33
240.0
-F
2768
0.100
516–604
960–1120
1141
660
23
242.0
-T77
2823
0.102
527–638
980–1180
1798
1040
38
-T571
—
—
—
—
1591
920
34
A242.0
-T75
2823
0.102
527–638
980–1180
—
—
—
295.0
-T4
2823
0.102
521–643
970–1190
1642
950
35
-T62
—
—
—
—
1694
980
35
319.0
-T5
2796
0.101
521–604
970–1120
—
—
—
-T6
—
—
—
—
—
—
—
355.0
-T51
2713
0.098
549–621
1020–1150
2006
1160
43
-T6
—
—
—
—
1694
980
36
-T7
—
—
—
—
1954
1130
42
C355.0
-T6
2713
0.098
549–621
1020–1150
1746
1010
39
356.0
-T51
2685
0.097
560–616
1040–1140
2006
1160
43
-T6
—
—
—
—
1798
1040
39
-T7
—
—
—
—
1850
1070
40
A356.0
-T6
2713
0.098
560–610
1040–1130
1798
1040
40
A357.0
-T6
2713
0.098
554–610
1030–1130
1902
1100
40
359.0
-T6
2713
0.097
566–599
1050–1110
1642
950
35
520.0
-T4
2574
0.093
449–599
840–1110
1037
600
21
33
Permanent Mold Castings
222.0
-T65
2962
0.107
521–627
970–1160
1556
900
242.0
-T571
2823
0.102
527–638
980–1180
1591
920
34
-T61
—
—
—
—
1591
920
33
319.0
-T6
2796
0.101
527–604
970–1120
—
—
—
332.0
-T5
2768
0.100
527–638
970–1180
1245
720
26
333.0
-T5
2768
0.100
527–643
970–1090
1452
840
29
-T6
—
—
—
—
1400
810
29
-T7
—
—
—
—
1694
980
35
-T551
2713
0.098
538–627
1000–1060
1400
810
29
-T65
—
—
—
—
—
—
—
354.0
-T62
2713
0.098
538–599
1000–1110
1504
870
32
355.0
-T6
2713
0.098
549–621
1020–1150
1798
1040
39
C355.0
-T61
2713
0.098
549–621
1020–1150
1746
1010
39
356.0
-T6
2685
0.097
560–616
1040–1140
1798
1040
41
-T7
—
—
—
—
1850
1070
40
A356.0
-T61
2713
0.098
560–610
1040–1130
1798
1040
40
A357.0
-T6
2713
0.098
554–610
1030–1130
1902
1100
40
359.0
-T62
2685
0.097
566–599
1050–1110
1642
950
35
336.0
a. Thermal conductivity at 25°C (77°F).
b. Percentage of International Annealed Copper Standard (IACS) value for Volume Electrical Conductivity, which equals 100% at 20°C (68°F).
AWS WELDING HANDBOOK
Choosing an aluminum filler metal that will work
best for a particular welded component requires an
understanding of the component and the expected
performance in service, and then determining which of
the characteristics associated with weld performance
is most important. It should be noted that selecting a
filler metal that is not recommended for the specific
application may result in inadequate service performance
that could cause premature failure of the welded joint.
The following characteristics should be considered
when evaluating a filler metal for the arc welding of
aluminum:
1. Crack sensitivity: This characteristic pertains to the
avoidance of hot cracking. The crack-sensitivity
rating of the weld metal can be established by
using hot cracking sensitivity curves that have
been developed for the various aluminum alloys,
and by assessing the amount of dilution that
occurs between the filler metal and base metal.
2. Strength of the welded joint: The tensile strength
of groove welds and the shear strength of fillet
welds can be determined by making trial welds
with different filler alloys; this can provide
extremely important parameters to be included
in the design of the weld. Various filler metals
may exceed the as-welded tensile strength of the
base material, but may produce significantly
different results in shear strength performance.
3. Ductility: This is a consideration when forming
operations are to be used during fabrication and
may also be a design consideration for service if
fatigue or shock loading, or both, are of
importance. In general, filler metals in the 5XXX
series have higher ductility than those in the
4XXX series.
4. Corrosion resistance: This property of an
aluminum weldment is a vital consideration if
it will be exposed to adverse environmental
conditions, such as exposure to fresh water or
salt water.
5. Sustained temperature service: The reaction of
some filler metals at sustained elevated temperature (higher than 66°C [150°F]) may promote
premature failure of the component due to stress
corrosion cracking. Any of the filler metals in the
5XXX series with more than 3% Mg content
may be susceptible to this condition.
6. Color match: Matching the colors of the base
metal and filler metal after anodizing can be of
major concern in applications requiring
enhanced appearance. For example, when welding
base metals in the 6XXX series, filler metals in the
4XXX series will produce a very dark gray color
after anodizing that will not match the base
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
25
series will more closely match the base metal
color after anodizing.
7. Postweld heat treatment (PWHT): Some filler
alloys will not respond favorably to postweld
heat treatment; other alloys have been developed
specifically to respond well to postweld heat.
Thus, when designing a welding procedure, it is
important to consider the chemistry of the filler
alloy and how it responds to postweld heat
treatment.
The extent and complexity of filler metal selection
can be demonstrated by using one of the many
aluminum base metals, 6061-T6 in this example, for
three different applications:
1. Alloy 6061-T6 tubing was used for a hand rail
that was to be clear-coat anodized after welding.
The filler metal was selected with color match
after anodizing as the prime consideration. The
most appropriate filler for this application was
Alloy 5356. Filler metals 4043, 4047, or 4643
are often considered to be suitable for this base
metal, but if these were used, the weld would
become dark gray after anodizing and would not
be an acceptable match to the bright silver
appearance of the hand-rail tubing.
2. Alloy 6061-T6 extruded angle bar was used as a
welded attachment bracket for a heating
component that is to operate consistently at
120°C (250°F). Filler alloys suitable for
elevated-temperature service were investigated.
Filler metals 5554, 4043, or 4047 are all
suitable for elevated-temperature service. Filler
metals 5356, 5183, or 5556 are often
considered to be suitable for this base
material, but if one of these were used, it
could introduce the possibility of sensitization
of the magnesium in these alloys, run the risk
of stress corrosion, and might cause premature
failure of the welded component.
3. Alloy 6061-T6 was used to fabricate a large
safety-critical lifting device that was required to
undergo extensive welding during fabrication,
followed by postweld solution heat-treatment
and artificial aging to restore strength and return
the structure to the T6 temper. In this
application, the strength of the weld after it
had been exposed to postweld heat treatment
was a concern. Most filler metals commonly
used for welding this base material will
not respond favorably to heat treatment. Filler
metals 5356, 5183, and 5556 are nonheattreatable alloys that can undergo undesirable
changes if subjected to this form of heat
treatment. Filler alloy 4043, on its own, is
26
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
the base material to achieve any significant
response to the heat- treatment. The use of Alloy
4643 or Alloy 4943 filler metal was considered.
Both are heat treatable and respond well to
postweld heat treatment, and both would provide weld strength comparable to that of the
base metal.
ALUMINUM LITHIUM
ALUMINUM SILICON
Each of the characteristics specific to the application
should be evaluated in detail. Filler metal selection
charts resulting from careful consideration of all the
variables have been developed and often provide a rating system for each variable. A basic filler metal selection chart, shown in Table 1.21 is published by the
American Welding Society (AWS).5 The chemical composition of solid wires and rods is shown in Table 1.22.
A number of such charts are available in AWS documents and from aluminum filler metal manufacturers.
As previously noted, many base metals can be welded
using any one of several filler metals, but only one may
be ideal for a specific application.
ALUMINUM COPPER
ALUMINUM MAGNESIUM
ALUMINUM Mg2-Si
Cracking
The nonheat-treatable aluminum alloys typically can
be welded with a filler metal of the same basic composition as the base alloy. The metallurgy of heat-treatable
alloys is somewhat more complex and these alloys are
more sensitive to intergranular, or grain-boundary,
cracking during the weld cooling cycle.
Generally, a dissimilar filler metal with a lower melting temperature and similar or lower strength compared to the base metal can be used for the heattreatable alloys, e.g., Alloy 4043 with a solidus of
577°C (1070°F) or Alloy 4145 with a solidus of 510°C
(970°F). By allowing the constituents of the base metal
adjacent to the weld to solidify before the weld metal
(base alloy mixed with filler metal) solidifies, stresses
are minimized in the base metal during cooling, thus
intergranular cracking tendencies are minimized.
The relative sensitivity to cracking, based on the
composition of weld metal of the alloys in the Al-Si
4XXX series, the Al-Mg 5XXX series, the Al-Cu 2XXX
series, and the Al-Mg2Si 6XXX series, are shown in Figure 1.1. These curves show that the aluminum alloys
with high silicon content and those with high magnesium content are successfully welded because they have
a low sensitivity to cracking. If the chemistry of the
weld metal falls within the crack sensitivity peaks, weld
cracking could be a problem.
5. American Welding Society (AWS) Committee on Filler Metals and
Allied Materials, 2012, Specification for Bare Aluminum and AluminumAlloy Welding Electrodes and Rods, AWS A5.10/AWS 5.10M:2012
(ISO 18273:2004 MOD) an American National Standard, Miami:
American Welding Society.
0
1
2
3
4
5
6
PERCENTAGE OF ALLOYING ELEMENT
Figure 1.1—Relative Sensitivity to Hot Cracking
of Welds in Aluminum Alloyed with (A) Lithium,
(B) Silicon, (C) Copper, (D) Magnesium,
and (E) Magnesium-Silicide
The heat-treatable Alloy 2219 (6.3% Cu) is easily
welded using companion Alloy 2319 filler metal. Alloys
in the 6XXX series are very sensitive to cracking if the
weld metal composition remains close to the base metal
composition, as shown in the square groove joint in
Figure 1.2. These alloys can be easily welded if the
edges are beveled to permit an excess amount of filler
metal to mix with the base metal. For Alloy 6061, the
weld metal should be composed of at least 50% Alloy
4043 filler metal or 70% Alloy 5356 filler metal. Fillet
welds naturally permit mixing of filler metal, provided
the base metal is not excessively melted. Autogenous
welding of base metals in the 6XXX series is not recommended, as illustrated in Figure 1.3.
Alloy 4145 filler metal provides the least susceptibility to cracking when welding base metal alloys in the
2XXX series, such as 2014 and 2618, and also the AlCu and Al-Si-Cu cast alloys, such as 319.0 and 355.0.
—
—
—
—
—
5083
5086
5154, 5254i
5454
5456
201.0, 206.0, 224.0
C355.0
354.0, 355.0
319.0, 333.0
443.0, A444.0
A357.0, 413.0
356.0, A356.0, 357.0
514.0, 535.0
511.0, 512.0, 513.0
ER2319a, h
ER4145c
ER4145
—
—
7004, 7005, 7039
710.0, 712.0
ER4145
6009, 6010, 6070
6351, 6951
6101, 6151, 6201
ER4145
—
5052, 5652i
6005, 6061, 6063
—
2219
5005, 5050
ER4145e
ER2319a
2014, 2036
—
ER4145e
ER4145e
1100, 3003, Alc 3003
3004, Alc 3004
ER4145
ER4145
1060, 1070, 1080, 1350
ER4145b, c, h
ER4145b, c
ER4043b, h
ER4043f
ER4043b, f
ER4043b
—
ER4043a, b, g
ER4043b, f, g
ER4145b, c
ER4145b, c
ER5356d
ER5356c, d
—
(Continued)
ER5356f
ER5356f
ER4043
ER5356f
ER5356f
ER5356f
ER5356d
ER5356c, d
ER4043f
ER5356d
ER4043f
ER4043b
—
—
—
ER5356f
ER5356c, d
ER5356f
ER5356f
ER4043
—
ER4043f
ER4043b
ER4043b
ER4043b
ER4043b
ER4145b, c
ER4145
ER5356c, d
ER5356c, d
ER4043a, b
ER4043a, b
511.0, 512.0,
513.0, 514.0,
535.0
356.0, A356.0
357.0, A357.0
413.0, 443.0,
A444.0
ER4043b
ER4145
ER4145
Base Metal
319.0, 333.0,
354.0, 355.0,
C355.0
201.0
206.0
224.0
ER5356d
ER4043
ER5356c, f
ER5556d
ER5356f
ER5356f
ER5356d
ER5183d
ER5356f
ER5356f
ER5356f
ER4043
—
ER5356c, d
ER5356c, d
7004, 7005,
7039, 710.0,
712.0
ER4043a, b, g
ER4043a, b, g
—
ER4043b
—
—
—
ER4043b
ER4043b
ER4043b
ER4043a, b
ER4145
ER4043a, b
ER4043a, b
6009
6010
6070
ER4043b, f, g
ER5356d
ER5356c, f
ER5356f
ER5356d
ER5356d
ER5356c, f
ER4043b, f
ER4043b, f
ER4043a, b
ER4145
ER4043b
ER4043b
6005, 6061,
6063, 6101,
6151, 6201,
6351, 6951,
Table 1.21
Guide to the Choice of Filler Metal for General Purpose Welding
ER5556d
ER5356f
ER5356f
ER5356d
ER5183d
ER5356f
ER5356d
ER5356d
—
—
ER5356d
ER5356d
5456
ER5554c, f
ER5356f
ER5356d
ER5356d
ER5356f
ER5356f
ER5356f
ER4043b
—
ER4043b, d
ER4043b, d
5454
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
27
ER5356d
ER5356d
ER5356d
ER5356d
ER5356f
ER5356d
ER5356d
ER5356f, i
5052, 5652i
5083
5086
5154, 5254i
3004
ER5356f
ER5183d
ER5356d
ER5356d
ER5356d
—
—
ER5356d
ER5356d
5083
ER5654c, f, i
ER5356c, d
ER4145e
ER2319a
ER4145
ER4145e
ER4145
2014
2036
ER4145b, c
ER4145b, c
2219
ER1100b, c
ER1100b, c
ER1188b, c, h, j
1060
1070
1080
1350
ER4145 may be used for some applications.
ER4047 may be used for some applications.
ER4043 may be used for some applications.
ER5183, ER5356, or ER5556 may be used.
ER2319 may be used for some applications. It can supply high strength when the weldment is postweld solution heat-treated and aged.
ER5183, ER5356, ER5554, ER5556, and ER5654 may be used. In some cases, they provide: (1) improved color match after anodizing treatment, (2) highest weld ductility, and (3) higher weld
strength. ER5554 is suitable for sustained elevated temperature service.
ER4643 and ER4943 will provide higher strength than ER4043 in 12 mm (0.500 in.) and thicker groove welds in 6XXX base alloys when postweld solution heat-treated and aged. They will also provide higher strength fillet welds than ER4043 in the as welded, postweld aged, or postweld heat-treated and aged conditions.
Filler metal with the same analysis as the base metal is sometimes used. The following wrought filler metals possess the same chemical composition limits as cast filler alloys: ER4009 and R4009
as R-C355.0; ER4010 and R4010 as R-A356.0; and R4011 as R-A357.0.
Base metal Alloys 5254 and 5652 are used for hydrogen peroxide service. ER5654 filler metal is used for welding both alloys for service temperatures below 66°C (150°F).
ER1100 may be used for some applications.
ER5356c, f
ER4043a, b
ER4145
ER4043b, d
ER4043b, d
3004
Alc. 3004
1100
3003
Alc. 3003
Source: Adapted from American Welding Society (AWS) Committee on Filler Metals and Allied Materials, 2012, Specification for Bare Aluminum and Aluminum-Alloy Welding Electrodes and Rods,
A5.10/A5.10M:2012 (ISO 18273:2004 MOD), Miami: American Welding Society. Table 1.
Notes:
1. ER4047, ER4643, or ER4943 may be used in some applications when alloy ER4043 is specified.
2. Service conditions such as immersion in fresh or salt water, exposure to specific chemicals, or a sustained high temperature (over 66°C [(150°F]) may limit the choice of filler metals. Filler metals
ER5183, ER5356, and ER5556 are not recommended for sustained elevated temperature service.
3. Recommendations in this table apply to gas shielded arc welding processes. For oxyfuel gas welding, only ER1188, ER1100, ER4043, ER4047, and ER4145 filler metals are ordinarily used.
4. Where no filler metal is listed, the base metal combination is not recommended for welding.
i.
j.
h.
g.
a.
b.
c.
d.
e.
f.
ER5356c, f
ER5356c, f
ER4043a, b
ER5356c, f
ER4145
—
ER1100b, c
ER1100b, c
5005
5050
ER4043b
ER4043b, d
ER4043b, d
5052
5652i
Note: ISO Classifications different from AWS Classifications have not been added to this table.
3004,
5005, 5050
—
—
ER5356d
Alc
ER4043
ER5356f
2219
—
ER5356c, d
1100, 3003, Alc 3003
2014, 2036
ER5356d
ER5356c, d
1060, 1070, 1080, 1350
ER5356d
5086
5154
5254i
Base Metal
Table 1.21 (Continued)
Guide to the Choice of Filler Metal for General Purpose Welding
28 CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
29
FILLET WELDS
80% FILLER METAL
20% BASE METAL
LOW SENSITIVITY TO CRACKING
SINGLE-V-GROOVE WELD
60% FILLER METAL
40% BASE METAL
LOW SENSITIVITY TO CRACKING
(A)
(B)
Photograph courtesy of ITW Welding North America
Figure 1.3—Differences in Welded Joint in Alloy
6061 (A) with Filler Metal (No Cracking)
and (B) without Filler Metal (Cracking)
SQUARE-GROOVE WELD
20% FILLER METAL
80% BASE METAL
HIGH SENSITIVITY TO CRACKING
Figure 1.2—Admixture of Base Metal and
Filler Metal in Typical Weld Joints
Alloys in the 7XXX series exhibit a wide range of
sensitivity to cracking because of a relatively high copper content. Base metal alloys with a lower copper content (e.g., Alloys 7004, 7005, and 7039) are welded
with filler metal 5356, 5183, or 5556. Aluminum alloys
with higher copper content (e.g., 7075 and 7178) are
not acceptable for arc welding.
Filler metals with high silicon content (i.e., the
4XXX series) should not be used to weld alloys in the
5XXX series with high magnesium content because the
excessive magnesium-silicide eutectics that develop in
the weld structure decrease ductility and increase crack
sensitivity. Mixing high-magnesium-content alloys with
high-copper-content alloys results in high sensitivity to
weld cracking and low ductility in the weld.
Strength
In many cases, several filler metals are available that
meet the minimum required as-welded mechanical
properties. Typical all-weld-metal minimum shear
strengths and ultimate tensile strengths of several filler
metals are listed in Table 1.23. The diffusion of alloying
elements from the base metal into the weld metal may
increase the as-welded mechanical properties.
The selection of filler metal is more limited when
weldments in heat-treatable alloys are to be postweld
heat treated. When welding base metal Alloys 2219 and
2014, the heat-treatable filler metal 2319 will provide
the highest strength. In most cases, a filler metal that is
not a heat-treatable composition or is only mildly
responsive to strengthening by thermal treatments can
be used. For example, when welding base metal Alloy
6061-T6 that is less than 12.7 mm (0.5 in.) thick with
Alloy 4043 filler metal, the magnesium in Alloy 6061T6 migrates into the weld metal and produces enough
magnesium-silicide to respond to heat treatment. In
thicker groove welds, the wider bevels can prevent
the diffusion of magnesium to the center of the weld,
and little or no response results from postweld heat
R-C355.0
R-A356.0
R-357.0
R-A357.0
ER4009,
R4009
ER4010,
R4010
R4011
ER4018,
R4018
ER4043,
R4043
ER4043A,
R4043A
ER4046,
R4046
ER4047,
R4047
ER4047A,
R4047A
ER3103,
R3103
R-206.0c
ER2319,
R2319
ER1070,
R1070
ER1080A,
R1080A
ER1100,
R1100
ER1188
R1188
ER1200,
R1200
ER1450,
R1450
AWS
Classification
Al99,0Cu
Al 99,88
Al99,0
Al99,5Ti
Al 1100
Al 1188
Al 1200
Al 1450
AlSi7Mg0,5Ti
AlSi7Mg
AlSi5
AlSi5(A)
AlSi10Mg
AlSi12
AlSi12(A)
Al 4011
Al 4018
Al 4043
Al 4043A
Al 4046
Al 4047
Al 4047A
AlSi7Mg
Al 4010
—
—
—
—
AlSi5Cu1Mg
AlMn 1
AlCu6MnZrTi
Al 4009
—
—
—
—
Al 3103
Al 2319
—
Al99,8(A)
Al 1080A
—
Al99,7
ISO 18273
Chemical
Al 1070
ISO 18273
Numerical
Alloy Symbol
0.15
0.25
Fe
0.06
11.0–13.0
11.0–13.0
9.0–11.0
4.5–6.0
4.5–6.0
6.5–7.5
6.5–7.5
6.5–7.5
4.5–5.5
4.5–5.5
6.5–7.5
6.5–7.5
6.5–7.5
0.50
0.20
0.10
0.25
0.6
0.8
0.50
0.6
0.8
0.20
0.20
0.20
0.20
0.20
0.20
0.15
0.20
0.7
0.30
0.15
0.40
Si + Fe 1.00
0.06
Si + Fe 0.95
0.15
0.20
Si
0.30
0.30
0.03
0.30
0.30
0.05
0.20
0.20
1.0–1.5
1.0–1.5
0.20
0.05
0.20
0.10
5.8–6.8
4.2–5.0
0.05
0.05
0.005
0.05–0.20
0.03
0.04
Cu
Mg
Cr
0.02
–
0.15
0.15
0.40
0.15
0.05
0.10
0.10
0.10
0.10
0.10
0.10
0.03
0.10
(Continued)
0.10
0.10
0.20–0.50
0.20
0.05
0.50–0.8
0.45–0.7
0.30–0.45
—
—
—
—
—
—
—
—
—
0.20
0.20
0.10
0.10
0.10
0.10
0.10
0.10
0.10
0.10
0.10
0.05
0.10
ALUMINIUM-SILICON
0.40–0.6
—
0.25–0.45
—
0.45–0.6
—
0.40–0.7
—
0.45–0.6
0.20
0.30
0.10
0.10
0.9–1.5
ALUMINIUM-MANGANESE
0.20–0.40
0.10
0.10
0.03
0.10
0.06
0.04
ALUMINIUM-COPPER
0.20–0.50
0.15–0.35
—
—
—
—
—
—
0.07
0.05
—
0.01
—
0.02
0.03
Zn
—
0.05
0.05
0.01
0.05
0.02
0.03
ALUMINIUM-LOW ALLOYED
Mn
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
V 0.05–
0.15
—
0.10–0.25
—
—
—
—
—
—
—
Zr
0.15
—
0.15
0.15
0.20
0.20
0.04–0.20
0.20
0.20
0.20
0.20
0.20
0.04–0.20
—
—
—
—
—
—
—
—
—
—
—
—
—
Ti + Zr 0.10
0.10–0.20
0.15–0.30
0.10–0.20
0.05
0.01
—
—
—
0.02
0.03
Ti
Ga 0.03
V 0.05
Ga 0.03
V 0.05
Ga, V
Chemical Composition in Weight Percenta, b
Table 1.22
Chemical Composition of Solid Wires and Rods
0.0003
0.0003
—
0.0003
0.0003
0.0003
0.0003
0.0003
0.0003
Be
0.0003
0.0003
Rem
Rem
Rem
Rem
Rem
Rem
0.0003
0.0003
0.0003
0.0003
0.0003
0.0003
Rem 0.04–0.07
Rem
Rem
Rem
—
Rem
—
Rem
—
Rem 0.04–0.07
Rem
Rem
Rem
99.50
99.00
99.88
99.00
99.80
99.70
Almin.
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.03
0.05
0.01
0.05
0.02
0.03
Other
Each
0.15
0.15
0.15
0.15
0.15
0.15
0.15
0.15
0.15
0.15
0.15
0.15
0.15
0.15
0.15
0.15
—
0.15
—
0.15
—
—
Other
Total
30 CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
—
AlSi4Mg
Al 4643
—
AlSi10Cu4
Al 4145
ISO 18273
Chemical
0.8
0.40
5.0–6.0
0.8
Fe
3.6–4.6
9.3–10.7
Si
0.10
0.10
3.3–4.7
Cu
Mg
Cr
0.05
0.05
0.15
0.10–0.50
0.10–0.30
0.15
—
—
0.15
ALUMINIUM-SILICON (Continued)
Mn
0.10
0.10
0.20
Zn
—
—
—
Ga, V
0.15
0.15
—
Ti
Chemical Composition in Weight Percenta, b
—
—
—
Zr
0.0003
0.0003
0.0005
0.0005
0.0003
0.0003
0.0005
0.0003
0.0003
0.0003
0.0005
0.0005
0.0003
0.0005
0.0003
Rem
Rem
Rem
Rem
Rem
Rem
Rem
Rem
Rem
Rem
Rem
Rem
Rem
Rem
0.0003
0.0003
0.0003
Be
Rem
Rem
Rem
Rem
Almin.
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
Other
Each
0.15
0.15
0.15
0.15
0.15
0.15
0.15
0.15
0.15
0.15
0.15
0.15
0.15
0.15
0.15
0.15
0.15
0.15
Other
Total
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
Source: Adapted from American Welding Society, AWS A5.10/A5.10M:2012 (ISO 18273:2004 MOD), Table 1.
ALUMINIUM-MAGNESIUM
ER5087,
Al 5087
AlMg4,5MnZr
0.25
0.40
0.05
0.7–1.1
4.5–5.2
0.05–0.25 0.25
—
0.15
0.10–0.20
R5087
ER5183,
Al 5183
AlMg4,5Mn0,7(A)
0.40
0.40
0.10
0.50–1.0
4.3–5.2
0.05–0.25 0.25
—
0.15
—
R5183
ER5183A,
Al 5183A
AlMg4,5Mn0,7(A)
0.40
0.40
0.10
0.50–1.0
4.3–5.2
0.05–0.25 0.25
—
0.15
—
R5183A
ER5187,
Al 5187
AlMg4,5MnZr
0.25
0.40
0.05
0.7–1.1
4.5–5.2
0.05–0.25 0.25
—
0.15
0.10–0.20
R5187
ER5249,
Al 5249
AlMg2Mn0,8Zr
0.25
0.40
0.05
0.50–1.1
1.6–2.5
0.30
0.20
—
0.15
0.10–0.20
R5249
ER5356,
Al 5356
AlMg5Cr(A)
0.25
0.40
0.10
0.05–0.20 4.5–5.5
0.05–0.20 0.10
—
0.06–0.20
—
R5356
ER5356A
Al 5356A
AlMg5Cr(A)
0.25
0.40
0.10
0.05–0.20 4.5–5.5
0.05–0.20 0.10
—
0.06–0.20
—
R5356A
ER5554,
Al 5554
AlMg2,7Mn
0.25
0.40
0.10
0.50–1.0
2.4–3.0
0.05–0.20 0.25
—
0.05–0.20
—
R5554
ER5556,
Al 5556
AlMg5Mn1Ti
0.25
0.40
0.10
0.50–1.0
4.7–5.5
0.05–0.20 0.25
—
0.05–0.20
—
R5556
ER5556A,
Al 5556A
AlMg5Mn
0.25
0.40
0.10
0.6–1.0
5.0–5.5
0.05–0.20 0.20
—
0.05–0.20
—
R5556A
ER5556B,
Al 5556B
AlMg5Mn
0.25
0.40
0.10
0.6–1.0
5.0–5.5
0.05–0.20 0.20
—
0.05–0.20
—
R5556B
ER5556C,
Al 5556C
AlMg5Mn1Ti
0.25
0.40
0.10
0.50–1.0
4.7–5.5
0.05–0.20 0.25
—
0.05–0.20
—
R5556C
ER5654,
Al 5654
AlMg3,5Ti
Si + Fe 0.45
0.05
0.01
3.1–3.9
0.15–0.35 0.20
—
0.05–0.15
—
R5654
ER5654A,
Al 5654A
AlMg3,5Ti
Si + Fe 0.45
0.05
0.01
3.1–3.9
0.15–0.35 0.20
—
0.05–0.15
—
R5654A
ER5754,
Al 5754e
AlMg3
0.40
0.40
0.10
0.50
2.6–3.6
0.30
0.20
—
0.15
—
R5754
a. Single values shown in the table are maximum values, except for Al.:
b. The results shall be rounded to the same number of significant figures as in the specified value using the rules in accordance with ISO 80000-1 or ASTM E29.
c. For R-206.0, Ni = 0.05 max. and Sn = 0.05 max.
d. These classifications have patent application pending.
e. Alloy Al 5754 also limits the sum (Mn + Cr): 0.10 to 0.6.
ER4145,
R4145
ER4643,
R4643
ER4943,d
R4943d
AWS Classi- ISO 18273
fication
Numerical
Alloy Symbol
Table 1.22 (Continued)
Chemical Composition of Solid Wires and Rods
AWS WELDING HANDBOOK
31
32
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
Table 1.23
Typical Properties of Aluminum Filler
Metals (As-Welded Condition)
Minimum Shear
Strength
All-Weld-Metal
Ultimate Tensile Strength
Filler
Alloy
MPa
ksi
MPa
ksi
1100
52
7.5
93
13.5
2319
110
16
258
37.5
4043
79
11.5
200
29
5183
128
18.5
283
41
5356
117
17
262
38
5554
117
17
230
33
5556
138
20
290
42
5654
83
12
221
32
treatments. Filler metal 4643 and filler metal 4943 contain sufficient magnesium so that a weld in base metal
Alloy 6061 that is 76 mm (3 in.) thick will attain a
transverse ultimate tensile strength of 440 MPa (45 ksi)
when postweld heat treated and aged to meet the original properties of Alloy 6061-T6.
The strength of fillet welds is highly dependent on
the filler metal composition and minimum shear
strength values (refer to Table 1.23). Filler metal 5356,
5183, and 5556 provide high shear strength for structural fillet welds.
The 1XXX and 5XXX series filler metals produce
very ductile welds and are preferred when the weldment
is subjected to forming or spinning operations, or
postweld straightening operations.
Elevated and Cryogenic Temperature
Service
Filler metals containing a composition of magnesium
nominally in excess of 3% (i.e., Alloys 5183, 5356,
5556, and 5654) are not suitable for applications in
which temperatures are sustained higher than 66°C
(150°F) because these filler metals can be sensitized to
stress-corrosion cracking. This sustained temperature
would include the length of time required for aging
treatments used in postweld thermal treatments in addition to service temperatures higher than 66°C (150°F).
All aluminum filler metals are suitable for cryogenic
temperature applications.
Corrosion Resistance, Filler Metals
Assemblies, vessels, drums, and tanks for use in certain corrosive environments or with certain chemicals
may require welding with special filler metals. These
special alloys may be of higher purity, such as Alloy
1188 filler metal than for welding chemical drums
made of Alloy 1060 base metal, or may have closer
composition limits on some alloying elements. A good
example is the tight control over copper and manganese
impurities in base Alloy 5254 plate with Alloy 5654
filler metal used for fabrication in hydrogen peroxide
service.
Aluminum-magnesium filler metals are highly resistant to general corrosion when used with base alloys
that have similar magnesium content. The 5XXX series
filler metals, however, can be anodic to base metal
alloys in the 1XXX, 3XXX, and 6XXX series with
which they might be used. In immersed service, the
weld metal will pit and corrode at varying rates, based
on the difference in electrical potential of the weld
metal and the base metal. Thus, an aluminum-silicon
filler metal, such as Alloy 4043 or Alloy 4047, would
be preferred over Alloy 5356 filler metal for improved
corrosion resistance and for protection of the base
metal when welding Alloy 6061 base metal for an
immersed-service application.
Color Match
Color match between the weld metal and base metal
is often required for ornamental or architectural applications for which the weldments are given chemical or
electrochemical finishes. The final color is highly dependent on the composition of the filler alloy and how
closely it matches specific elements in the base alloy.
The two elements of primary interest are silicon and
chromium.
Silicon in an alloy will create a gray-to-black color
that varies with increasing percentages of silicon. Thus,
welds made with aluminum-silicon filler metal will
exhibit a sharp color contrast with all base alloys
except those clad with an aluminum-silicon alloy or
with one of the aluminum-silicon casting alloys. Chromium causes an alloy to develop a yellow or gold shade
when anodically treated, so a filler metal in the 5XXX
series with chromium content similar to the base metal
would be preferred. Copper and manganese in aluminum alloys produce slight darkening effects that need to
be considered.
Alloy 1188 filler metal will produce a good color
match in welds in alloys of the 1XXX series and also
with Alloys 3003, 5005, and 5050. Alloy 5356 filler
metal is a good choice for welding base metal alloys in
the 5XXX and 6XXX series when a color match is
needed.
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
33
POROSITY
Shielding During the Welding Operation
Contamination may occur because of inadequate
shielding gas coverage during welding. Exposure to the
surrounding atmosphere and contamination of the molten weld metal during the welding operation are possibilities to consider when examining a porosity problem.
Examples of the causes of contamination include the
following:
Figure 1.4—Porosity in
a Cross Section of a Fillet
Weld in Aluminum
TEMPERATURE °C
660
H2 SOLUBILITY (cm3/100 g)
Porosity can often be a problem when welding aluminum. It is caused by hydrogen gas becoming
entrapped within the solidifying aluminum weld pool,
resulting in voids in the completed weld. An example of
this condition is shown in a cross-section of a fillet weld
in aluminum in Figure 1.11.
Hydrogen is highly soluble in molten aluminum, and
for this reason, the potential for excessive amounts of
porosity during arc welding of aluminum is considerably high. The solubility of hydrogen in aluminum is
illustrated in Figure 1.12.
Hydrogen is sometimes introduced unintentionally
during the welding operation through contaminants
within the welding area. It is important to thoroughly
understand the many sources of these contaminants in
order to detect the cause and take the necessary action
to resolve porosity problems.
2500
BOILING POINT
50
0.7
0.036
MELTING POINT
SOLUBILITY IN LIQUID
AT MELTING POINT
SOLUBILITY IN SOLID
AT MELTING POINT
1220
TEMPERATURE °F
4532
Figure 1.5—Solubility of
Hydrogen in Aluminum
1. Welding in drafty conditions, such as strong
drafts from open doors or fans directed at
the welding area, can remove the shielding gas
during welding;
2. Excessive spatter buildup inside the gas nozzle
when gas metal arc welding can restrict gas flow
and reduce the efficiency of the shielding gas;
3. Incorrect standoff distance (the distance from
the end of the nozzle to the surface of the
workpiece) and changes in this distance can
produce significant variations in shielding gas
efficiency; and
4. Establishing and maintaining the correct
shielding gas flow rate will provide the most
efficient gas coverage; it should be high enough
to ensure adequate shielding, but not so
high that it can cause turbulence in the
weld pool during welding.
Reducing the level of porosity is sometimes
achievable by using argon-helium shielding gas mixtures.
The advantage of an argon-helium mixture is that it
provides additional heat during welding, and consequently allows a greater opportunity for the hydrogen
to escape prior to solidification. The use of helium as
an additive, sometimes up to 75%, can help to reduce
porosity levels; however, the best recourse against
unacceptable porosity levels is to remove the source
of hydrogen contamination.
34
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
Hydrocarbons
Hydrocarbons that may be present on the surface of
the aluminum plate or on the welding wire are sources
of hydrogen-related porosity. Some precautions include
the following:
1. Thoroughly cleaning plate surfaces prior to
welding to remove contaminants, such as
lubricants, grease, oil or paint;
2. Ensuring that exhaust contaminants, such as oil
and moisture derived from compressed air tools
used during weld preparation are removed from
the surface of the plate;
3. Ensuring that the quality of the aluminum
welding wire is satisfactory and that the welding
wire is clean and free of any residual oil used
during the wire manufacturing process,
otherwise it may be virtually impossible to
produce welds with acceptable porosity levels;
and
4. Anti-spatter compounds applied to the welding
nozzle or to the plate surface are not usually
recommended for aluminum welding when low
Moisture
Moisture (H2O) can be a cause of contamination to
the weld area of an aluminum plate. The following are
potential sources:
1. Water leaks that occur within the welding
equipment, if using a water-cooled welding
system;
2. The use of inadequately pure shielding gas
that does not meet the minimum purity
requirements specified by the appropriate code
or standard;
3. Moisture caused by imperfections within the gas
delivery line, such as leaking pipes or hoses;
4. High atmospheric humidity or a change in
temperature, (crossing a dew point) can
result in condensation on the plate. When
welding in high humidity, moisture is readily
acquired, even from small fluctuations in
temperature; and
5. Hydrated aluminum oxide is a source of
moisture that can result in porosity.
Hydrated Aluminum Oxide. Aluminum has a
protective layer of aluminum oxide that is relatively
thin and naturally forms on any exposed surface. The
oxide layer is porous and can absorb moisture, grow in
AWS WELDING HANDBOOK
also on the welding wire; however, properly stored aluminum with a thin uncontaminated oxide layer can be
easily welded with the gas shielding processes gas metal
arc welding (GMAW) and gas tungsten arc welding
(GTAW) processes, which break down and remove the
oxide during welding. When the aluminum oxide has been
exposed to moisture, it becomes hydrated and potential
problems with porosity arise.
Material Preparation
Other potential contamination problems are
associated with preparation of the workpieces for
welding. Cutting or grinding methods that may deposit
contaminants onto the plate surface or subsurface,
cutting fluids, debris from grinding discs, and lubricants
on discs or saw blade are areas of concern.
Material preparation methods must be evaluated as a
control element of the welding procedure that must not
be changed without revalidation. Certain types of
grinding discs, for example, can deposit particles within
the aluminum that will react during welding and cause
major porosity problems. Additionally, aluminum filler
materials should be stored in an area that will prevent
contamination by hydrocarbons or moisture.
Cleaning Prior to Welding. To achieve low porosity
levels for x-ray quality welds, it is important to
understand the methods available for the effective
removal of hydrocarbons and moisture from the weld
area, and to incorporate the appropriate methods into
the welding procedure. If contaminants are present in
the weld area during welding, they will produce hydrogen
and significantly contribute to porosity problems.
When designing welding procedures intended to
avoid high levels of porosity, it is important to incorporate
degreasing and oxide removal. Typically, this can be
achieved through a combination of chemical cleaning
or the use of solvents to remove hydrocarbons, followed
by brushing with a stainless steel wire brush to remove
contaminated aluminum oxide.
Finding and eliminating the cause of porosity within
a specific welding operation is not always a
straightforward exercise; it is often a time-consuming
and frustrating process. Correct cleaning of the
workpieces prior to welding is essential, in addition
to the use of proven surface preparation procedures.
It is also essential to use well-maintained equipment,
a high quality of shielding gas, and a high
quality of aluminum welding wire that is free from
contamination. All are important variables if a low
level of porosity is to be achieved.
AWS WELDING HANDBOOK
Storage and Use of Aluminum
Filler Metal
A major step toward producing good aluminum
welds is the use of quality filler metal of the correct size
and alloy composition. Filler metal should be free of gas
and nonmetallic impurities and have a clean, smooth
surface that is free of moisture, lubricant, or other contaminants. Preventive care is required during storage
and use to avoid contamination that would cause poor
welds.
The quality of the filler metal is particularly important when using the gas metal arc welding process. In
this consumable-electrode process, relatively smalldiameter filler wire is fed through the welding gun at
a high rate of speed. To feed properly, the filler metal
must be free from slivers, scratches, inclusions, kinks,
waves, or sharp bends; it must be uniform in diameter, of a suitable temper, and spooled so that it is free
to unwind without restriction. Proper pitch and cast
also are important to prevent wandering of the wire
as it emerges from the contact tip. If the electrode
surface is not clean, the high rate of wire feed can
carry a relatively large amount of foreign material
into the weld pool, resulting in porosity or poor-quality
welds.
To avoid contamination, supplies of filler metal
must be kept covered and stored in a dry place at a relatively uniform temperature. Electrode spools temporarily left on the welding machine (e.g., between work
shifts) should be covered with a clean cloth or plastic
bag if the feed unit does not have a built-in cover. If a
spool of wire will not be used overnight, it should be
returned to the original carton and tightly sealed,
unless it is in a spool enclosure that provides a dry or
protective atmosphere. Original containers of electrodes should not be opened until the contents are to
be used. Electrodes in the 5XXX series are most likely
to develop a hydrated surface oxide; therefore when
these electrodes are not in use, they should be stored in
cabinets that maintain a low (less than 35%) relative
humidity.
Information on the manufacture, packaging, testing,
and selection of bare aluminum filler materials is contained in Specification for Bare Aluminum and Aluminum-Alloy Welding Electrodes and Rods, AWS A5.10/
A5.10M:2012, published by the American Welding
Society.6
6. American Welding Society (AWS) Committee on Filler Metals and
Allied Materials, 2012, Specification for Bare Aluminum and AluminumAlloy Welding Electrodes and Rods, AWS A5.10/A5.10M:2012 (ISO
1873:2004 MOD), an American National Standard, Miami: American
Welding Society.
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
35
SURFACE PREPARATION
Quality arc welds in aluminum require the metals to
be clean, dry, and coated with a thin oxide film. Aluminum materials must be properly stored to maintain this
condition. Any moisture or hydrocarbons in the arc
area during welding will dissociate and produce hydrogen, which is the primary cause of porosity in aluminum welds. Hydrated oxides and water stains on
aluminum that has been improperly stored can be particularly troublesome because the moisture penetrates
and causes inward oxide growth. This hydrated-oxide
layer contains chemically combined water, which causes
porosity. Also, the thickened oxide is difficult to remove
by arc cleaning action (the oxide melts at 2038°C
[3700°F]), which is significantly higher than the melting
point of aluminum alloys) and prevents proper fusion.
Aluminum materials should be properly stored when
they are received to minimize future cleaning operations. Storing layers of aluminum outdoors or in buildings without adequate climate control will result in
moisture condensation on the metal, which permits
moisture to be drawn between the layers by capillary
action. If the product is interleaved with paper, a wicking action can occur which will further contribute to
water stains and hydrated-oxide conditions. Good storage practice is to position aluminum sheets vertically
and far enough apart to permit moisture to run off and
to allow air circulation to dry the surfaces.
Prior to welding, the first operation should be to
remove all grease, oil, dirt, paint, and other surface contaminants that can generate hydrogen or interfere with
weld fusion. The materials can be degreased by wiping,
spraying, dipping, or steam cleaning.
The cleaning and welding areas must be well ventilated. If chlorinated solvents are used for degreasing,
this should take place at a location remote from the
welding area. Highly toxic phosgene gas can result from
the dissociation of the vapors of chlorinated hydrocarbons (e.g., trichloroethylene and other chlorinated
hydrocarbons) by arc radiation. (Refer to the Safe Practices section of this chapter.)
Petroleum-base solvents leave little residue and are
nontoxic when used in a well-ventilated welding area,
but these solvents have low flash points and require
special storage and handling. Instructions for the safe
handling and use of the solvent provided by the manufacturer in the safety data sheet (SDS) should be carefully followed.
The thin aluminum-oxide film is naturally formed on
the surface of aluminum and is removed by the arc of
the gas shielded processes or by the fluxes used in other
joining methods. The thick oxide film or coating resulting from thermal, chemical, or electrochemical treatments, or poor storage conditions must be removed and
the surfaces cleaned before welding.
36
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
Oxide removal is accomplished with caustic soda,
acids, or proprietary solutions. Some of these are listed
in Table 1.24. The rinsing and drying cycles require special attention to avoid residual chemicals or production
of a hydrated oxide. If the metal surface is rough from
machining, sawing, forming, or improper handling, the
welding surface may have folds that could entrap oxide
or lubricants. Chemical etching is often used to open
and remove any metal folds or burrs. (Refer to the Safe
Practices section of this chapter for information on the
safe handling of chemical cleaning and etching agents.)
Mechanical oxide removal, although not as consistent as chemical means, is usually satisfactory if performed properly. These methods include wire brushing,
scraping, or filing. Grinding or sanding with wheels or
discs can be done with proper equipment, although
abrasive particles can be easily embedded in the aluminum surface, which may result in unacceptable inclusions in the weld. Contamination of the surface with a
binder compound may create poor fusion or porosity in
the weld.
Wire brushing is, by far, the most widely used
method for removing oxides. Stainless steel brushes with
bristle diameters of 0.25 mm to 0.38 mm (0.010 in. to
0.015 in.) provide good abrasive action. The brush
must be kept clean of all contaminants, and it should be
used with a light pressure to avoid burnishing the aluminum surface and entrapping oxide particles. Hand
brushes are as effective as power brushes.
Table 1.24
Chemical Treatments for Oxide Removal Prior to Welding or Brazing Aluminum*
Type of Solution
Concentration
1. Sodium Hydroxide 1. NaOH 50 grams
(Caustic Soda)
(1.76 oz) 1 L
(0.26 per gal) of
water
Temperature
Type of Container
Procedure
Purpose
1. 60°C–71°C
(140°F–160°F)
1. Mild steel
1. Immerse for 10 seconds to 60 seconds.
Rinse in cold water.
2. Room
2. Type 347
stainless steel
2. Immerse for 30 seconds. Rinse in cold
water. Rinse in hot
water and dry.
60°C–82°C
(160°F–180°F)
Antimonial lead
lined steel tank
Dip for 2 minutes to
3 minutes. Rinse in cold
water. Rinse in hot water
and dry.
For removal of heattreatment and annealing
films and stains and for
stripping oxide coatings.
Dip for 5 minutes to
10 minutes. Rinse in
cold water. Rinse in hot
water and dry.
For removal of heattreatment and annealing
films and stains and for
stripping oxide coatings.
Removes thick oxide for
all welding and brazing
procedures. Active
etchant.
followed by
2. Nitric Acid
2. Equal parts of
HNO3 (68%)
and water
Sulfuric-Chromic
H2SO4—
3.79 L (1 gal)
CrO3—
1.28 kg (45 oz)
Water—
34.1 L (9 gal)
Phosphoric-Chromic
H3PO4 (75%)—
13.3 L (3.5 gal)
CrO3—
79.4 grams (1.75 lb)
Water—
379 L (100 gal)
93°C (200°F)
Type 347
stainless steel
Sulfuric Acid
H2SO4—
165 grams (5.81 oz)
Water—
1 L (0.26 gal)
73°C (165°F)
Polypropylene-lined Immerse for 5 minutes
steel tank
to 10 minutes. Rinse in
cold water. Rinse in hot
water and dry.
Oxide removal. Mild
etchant.
Ferrous Sulfate
Fe2SO4 H2O
10% by volume
26.7°C (80°F)
Polypropylene
Oxide removal.
Immerse for 5 minutes
to 10 minutes. Rinse in
cold water. Rinse in hot
water and dry.
*All chemicals used as etchants are potentially dangerous. All persons using any of these etchants should be thoroughly familiar with all of the chemicals
involved and the proper procedures for handling and mixing these chemicals. Always add the chemicals to water. Never add the water to the chemicals.
Safety glasses must be worn at all times when using chemical etchants. Avoid contact with the skin. When working with unfamiliar chemicals or cleaning
products, the Safety Data Sheet (SDS) for the specific product should always be consulted before use. These are available from the suppliers and must be
available to all employees for guidance on the proper handling of the materials.
AWS WELDING HANDBOOK
Abrasive pads or belts should not be used when preparing for arc welding because they will leave a residue
(hydrocarbon) that leads to porosity in the welds.
It should be noted that chemical cleaning and brushing of joint components should be done prior to assembly for welding; fitted joints may retain solvents or
contaminants that result in weld discontinuities.
PROPERTIES AND
PERFORMANCE OF
ALUMINUM WELDMENTS
The properties and performance of a welded joint in
aluminum are influenced by many factors, including the
composition, form, and temper of the base metals, the
filler metal used, the welding process, rate of cooling,
joint design, postweld mechanical or thermal treatments, and the service environment.
METALLURGICAL EFFECTS
The effect of the heat of welding, which causes the
softening of the base metal adjacent to the weld, is generally the controlling factor relative to the as-welded
strength of an aluminum weldment. The composition
and structure of the weld metal can also significantly
affect final strength, ductility, and toughness.
Weld Metal
The properties of the deposited aluminum weld
metal are influenced by the composition and rate of
solidification. The solidification rate depends on the
welding process and technique, in addition to all the
factors affecting heat input and the rate of heat transfer away from the weld pool. A higher rate of solidification generally produces a finer-grained microstructure
with greater strength and decreased tendency for hot
cracking.
The composition of the weld metal depends on the
chemical composition of the base metal and filler metal,
and the resultant mixture is influenced by the joint
design, welding process, and procedure employed.
When welding the nonheat-treatable aluminum alloys,
a filler metal with a chemical composition similar to
that of the base metal is generally selected. The melting
range of the heat-treatable aluminum alloys is much
wider and these alloys are more sensitive to hot cracking. A dissimilar filler metal with a lower solidus temperature than that of the base metal is generally
employed; this will allow the heat-treatable base metal
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
37
to completely solidify and develop strength along the
fusion zone before weld solidification shrinkage stresses
occur.
The molten weld metal exhibits a high solubility for
hydrogen. Hydrogen can be introduced into the weld
metal from residual hydrocarbons or hydrated oxides
on the surfaces of the base and filler metals, and also
from faulty welding equipment or improper gas shielding that permits moist atmospheric contamination.
During solidification of the weld, hydrogen precipitates
out of the solidifying molten aluminum and becomes
entrapped in the solid weld metal as porosity. Thus, it
becomes very important to eliminate sources of hydrogen from the weld area when using welding procedures
that result in rapid solidification of the weld metal. Bare
filler wire must be properly cleaned and stored in a dry
environment until needed for production.
Heat-Affected Zone
The effect of the heat of welding on aluminum base
alloys varies with the distance from the weld and may
be divided roughly into areas that are represented by
the temperature attained by the metal. The length of
time at a specific temperature can be significant for the
heat-treatable alloys. The width of the heat-affected
zone (HAZ) in all alloys and the extent of metallurgical
changes in the heat-treatable alloys depend on the rate
of heat input and heat dissipation. These are influenced
by the welding process, the thickness or geometry of the
workpiece, the speed of welding, the preheat and interpass temperatures, and the types of backing or fixturing.
Figure 1.4 illustrates the effect of three heat-input conditions on the properties of the heat-affected zone and
the width of the HAZ in heat-treatable Alloy 6061-T6.
The recrystallization of cold-worked metal and some
grain growth are likely to occur in the HAZ of nonheattreatable alloys. The strength of the HAZ will be similar to that of the annealed material because the portion
of the HAZ subjected to temperatures higher than the
annealing temperature will be instantaneously
annealed. Time at temperature and cooling rate are not
critical variables for these alloys. The mechanical properties of welds in butt joints in nonheat-treatable aluminum alloys are shown in Table 1.25.
A typical metallurgical structure across the weld of a
nonheat-treatable alloy is illustrated in Figure 1.5. Very
little change in microstructure can be noted in the base
metal. The service performance of the weldment when
stressed parallel to the weld will depend somewhat on
the ratio of the width of the HAZ relative to that of the
unaffected base metal; when stressed transverse to the
weld, the mechanical properties obtained are independent of the welding process and technique employed in
making the weld.
38
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
DISTANCE FROM WELD, mm
5
10
15
20
25
110
100
HARDNESS, HRE
90
80
KEY
70
580 J/mm
(14 730 J/in.)
60
756 J/mm
(19 200 J/in.)
1128 J/mm
(28 650 J/in.)
50
0.25
0.5
0.75
1.0
DISTANCE FROM WELD, in.
Figure 1.4—Rockwell Hardness E Scale Profiles
of the Heat-Affected Zone of Gas Tungsten Arc
Welds on 6061-T6 Using Varied Heat Input
Heat-Treatable Alloys. The heat-treatable alloys
contain alloying elements that exhibit a noticeable
change in solubility with a change in temperature. The
high strengths of these alloys are induced by the controlled-solution heat-treatment and precipitation hardening (aging) of some of the microconstituents. The
heat-treatable alloys typically are welded in the aged
condition, during which a controlled amount of hardening microconstituents are precipitated from solid
solution. The heat of welding causes resolution of the
hardening microconstituents in the HAZ, followed by
an uncontrolled precipitation of the microconstituents
in the HAZ on cooling. This overaging in the HAZ lowers the base-metal strength adjacent to the weld.
The response of heat-treatable alloys to welding is
much more complex than that of the nonheat-treatable
alloys because response depends on the peak temperature and the time at temperature to which the metal is
exposed (refer to Figure 1.4). Thus, variations in the
metallurgical structure will change with distance from
the weld interface, as illustrated in Figure 1.6 and Figure 1.7. To completely soften these alloys, the annealing
temperature must be maintained for several hours. In
the HAZ, the annealing temperature is exceeded for a
short period of time. The welding process, technique,
preheat and interpass temperatures, and the rate of
cooling greatly influence the degree of microstructural
changes, which influences the sensitivity to hot cracking
and the amount of softening that occurs.
Table 1.25
Mechanical Properties of Gas-Shielded
Arc Welded Butt Joints in Nonheat-Treatable Aluminum Alloys
Base
Alloy
Filler
Alloy
ksi
Tensile
Elongation %
in 50.8 mm
(2 in.)
Free Bend
Elongation %
Average Ultimate
Tensile Strength
Minimum Ultimate
Tensile Strength
Minimum Tensile
Yield Strength*
MPa
MPa
MPa
ksi
ksi
1060
1188
69
10
55
8
17
2.5
29
63
1100
1100
90
13
76
11
31
4.5
29
54
1350
1188
69
10
55
8
17
2.5
29
63
3003
1100
110
16
97
14
48
7
24
58
5005
5356
110
16
97
14
48
7
15
32
5050
5356
158
23
124
18
55
8
18
36
5052
5356
193
28
172
25
90
13
19
39
5083
5183
296
43
276
40
165
24
16
34
5086
5356
269
39
241
35
117
17
17
38
5154
5654
228
33
207
30
103
15
17
39
5454
5554
241
35
214
31
110
16
17
40
5456
5556
317
46
290
42
179
26
14
28
*0.2% offset in a 254 mm (10 in.) gauge length across a butt joint.
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
39
Figure 1.5—Cross Section of (A) Gas Metal Arc Weld in 5456-H321
Plate, 9.5 mm (0.375 in.) Thick (Magnified 2X), Showing (B) Weld Metal,
(C) Heat-Affected Zone, and (D) Unaffected Zone (Magnified 100X)
The base metal immediately adjacent to the fusion
zone (B) is heated to a temperature sufficient to rapidly
re-dissolve any precipitates. This solid-solution zone (C)
will attain an intermediate strength and will be quite
ductile. Adjoining the solid-solution area is a zone (D)
that has been subjected to temperatures higher than the
precipitation-hardening temperature but lower than the
solution-heat-treatment temperature. This zone exhibits
varying degrees of over-aging and softening, depending
on the temperature and time held at the over-aging temperature. The portion of overaged (or partially
annealed) metal (D) closest to the solid-solution zone
generally possesses the lowest strength. Postweld aging
treatments have little effect on the strength of this zone.
The entire weldment must be solution heat-treated and
aged to reproduce the previous properties of the base
material. It is best to weld the heat-treated alloys with a
fast procedure that rapidly dissipates the heat to minimize the degree of over-aging and reduction of strength
that can occur in the heat-affected zone (HAZ).
Complete heat treatment (solution treating followed
by age hardening) of weldments may be practical in
some cases. When this is not the case, only postweld
aging can be used to improve the strength of the solidsolution zones, but this method should not be expected
to strengthen the already overaged material. If the base
metal is welded in the solution-heat-treated (-T4) condition, postweld aging can be very effectively employed to
improve as-welded strength. This procedure is most
effective for low-heat-input welding processes or techniques that avoid excessive precipitation aging. Typical
calculations of this improvement in strength of welds in
butt joints in heat-treated aluminum alloys are shown
in Table 1.26. Table 1.27 shows the effect of welding
conditions on the strength of groove joints in Alloy
6061 with filler metal ER4043.
TENSILE STRENGTH AND DUCTILITY
The tensile strength and ductility of aluminum-base
alloys are affected by the heat of welding and by applied
heat treatments. The effects on nonheat-treatable alloys
and heat-treatable alloys are presented in this section.
Nonheat-Treatable Alloys
The heat of welding causes nonheat-treatable alloys
to lose the effects of strain hardening in the HAZ. This
zone (adjacent to the weld) reaches the annealed condition, which is characterized by decreased strength and
increased ductility. Because the metal is annealed by the
initial welding operation, repeated welding during a
repair operation does not further reduce the strength,
except as influenced by a possibly wider HAZ. For this
reason, the minimum annealed tensile strength of the
base metal is generally considered as the minimum
strength of butt joints in the nonheat-treatable alloys.
40
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
KELLER’S ETCH
KELLER’S ETCH
1000X
(A)
(B)
(C)
(D)
(E)
Figure 1.6—Characteristics of the Five Microstructural
Zones Typical of Heat-Treatable Alloys
The as-welded properties of these nonheat-treatable
alloys are less affected by the temper of the base-metal
than the heat-treatable alloys. The same is generally
true of the effect that workpiece thickness has on these
properties. (Refer to Table 1.25 for data on the mechanical properties of butt joints in commonly welded nonheat-treatable alloys.)
Excellent ductility is exhibited by welds in the nonheat-treatable alloys. These welds are capable of developing extensive deformation prior to failure. The
higher-strength alloys in the 5XXX series are particularly favorable because of the closer matching of
strength and ductility in the various zones across the
weld joint. The aluminum-magnesium-manganese alloys,
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
DISTANCE FROM FUSION ZONE, mm
5
10
15
20
25
110
HARDNESS, DPH-500G
T4, PWA
100
T6, PWA
90
T6, AW
80
T4, AW
70
0
0.25
0.5
0.75
1.0
DISTANCE FROM FUSION ZONE, in.
Figure 1.7—Hardness Profiles of the
Heat-Affected Zone for 6061-T4 and 6061-T6
Starting Material in the As-Welded (AW)
and Postweld-Aged (PWA) Conditions
such as Alloys 5083, 5086, and 5456, are widely
applied in welded construction due to the superior
annealed strength and ductility of these alloys.
Heat-Treatable Alloys
The strength of the heat-treatable alloys is also
decreased by the heat of welding, but the substantial
time at temperature required to fully anneal these alloys
is not attained during welding. As a result, only partially annealed properties are observed in the HAZ in
the as-welded condition. These properties vary considerably with chemical composition, heat input, and cooling rate; these variations make it difficult to establish
minimum mechanical property values when designing
the weld. Performance data for a specific alloy, including temper, thickness, and joining process should be
established during the welding procedure qualification
process.
Refer to Table 1.26 for typical properties of welds in
butt joints in some of the heat-treatable alloys. The
mechanical property values provided are average and
cover a wide range of material thicknesses, which are
welded by either the gas tungsten arc or gas metal arc
welding process. Many different joint designs and weld-
41
ing procedures can be used. Weldments in heat-treatable alloys generally exhibit lower weld ductility in the
as-welded condition than that of similarly as-welded
nonheat-treatable alloys. The major exception involves
alloys in the weldable 7XXX series, which naturally are
aged quite rapidly after welding and provide increased
strength with good ductility.
The thickness of the workpiece can have a significant
effect on the as-welded properties of welds in the heattreatable alloys. Thinner gauges can be welded with less
total heat input and can dissipate the heat more rapidly
than the thicker gauges. The reduced time at temperature results in higher strength in the thinner heat-treatable alloys in the as-welded condition.
Preheating can noticeably reduce the strength of
welds in the heat-treatable alloys, particularly when
applied at temperatures in excess of 120°C (250°F);
corrosion resistance may also be impaired. Preheating
the heat-treatable alloys is rarely recommended, except
when the welds will be subjected to postweld heat
treatment.
It should be noted that repair welding of heat-treatable alloys may cause a slight lowering of the joint
strength of the weld when compared to the original
weld strength. Because of the microstructural changes
that take place during the original welding and the
greater restraint generally associated with repairs, the
tendency toward hot cracking can be greater in the
HAZ or in previously deposited weld metal.
Abnormal microstructure in aluminum, as in other
materials, may sometimes lead to difficulties in welding.
Areas of segregation, such as stringers of constituents
with low melting temperatures, can lead to porosity and
cracking. Grain size and orientation may have a noticeable effect on the weldability and resultant weld performance. As illustrated in Figure 1.8, the adverse grain
size and orientation in the Alloy 2014-T6 forging contributed to intergranular cracking of the grain boundary constituents with low melting temperatures.
Postweld Heat Treatment
The heat-treatable alloys may be heat-treated again
after welding to restore the base metal in the HAZ to
nearly the original strength. When tested, the joint will
fail in the weld metal except where the weld bead reinforcement is left intact. In this case, failure typically
occurs in the fusion zone at the edge of the weld. The
strength obtained in the weld metal after postweld heat
treatment depends on the filler metal used. When a
composition of filler metal different from that of the
base-metal composition is used, strength will depend on
the amount of admixture of the filler metal with base
metal. To obtain the highest strength, it is essential that
the weld metal responds to the type of postweld heat
42
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
Table 1.26
Typical Mechanical Properties of Gas-Shielded
Arc Welded Butt Joints in Heat-Treated Aluminum Alloys
As-Welded
Tensile Strength
Yield Strengtha
Postweld Heat-Treated and Aged
Elongation %
Filler
Alloy
MPa
ksi
MPa
ksi
Tensile in
50.8 mm
(2 in.)
2014-T6
4043
234
34
193
28
2014-T6
2319
241
35
193
28
2036-T4
4043
255
37
172
25
Base Alloy
and Temper
Tensile Strength Yield Strengtha
Elongation %
Tensile in
50.8 mm
(2 in.)
Free
Bend
MPa
ksi
4
9
345
50
—
—
2
5
5
—
414
60
317
46
5
—
5
—
—
—
—
—
—
—
MPa
ksi
Free
Bend
2219-T81, -T87
2319
241
35
179
26
3
15
379
55
262
38
7
5
2219-T31, -T37
2319
241
35
179
26
3
15
276b
40b
227b
33b
2b
12b
2519-T87
2319
255
37
227
33
4
15
386
56
—
5.5
—
41b
276b
40b
5.0b
—
—
—
—
—
—
2519-T37
2319
—
—
—
—
—
—
283b
6009-T4
4043
221
32
138
20
9
—
—
6010-T4
4043
234
34
145
21
10
—
—
—
—
—
—
—
6061-T6
4043
186
27
124
18
8
16
303c
44c
276c
40c
5c
11
6061-T6
5356
207
30
131
19
11
25
—
—
—
—
—
—
35b
165b
24b
3b
6061-T4
4043
186
27
124
18
8
16
241b
6063-T6
4043
138
20
83
12
8
16
207
30
—
—
6063-T6
5356
138
20
83
12
12
25
—
—
—
—
7004-T5
5356
276
40
165
24
8
38
—
—
—
—
—
—
7005-T53
5556
303
44
172
25
10
33
345
50
227
33
4
25
7039-T63
5183
324
47
221
32
10
34
—
—
—
—
—
—
13
—
—
11
—
a. Offset is 0.2% in gauge lengths of 50.8 mm (2 in.).
b. Postweld aged only.
c. For thickness greater than 12.7 mm (0.5 in.), 4643 filler is required.
treatment (PWHT) used. Although PWHT increases the
tensile strength, some loss in weld ductility occurs.
In very thick material, the mechanical properties of a
postweld heat-treated weldment may be lower than
those of the base metal if the filler metal used is not heat
treatable; in this case, the weld metal would be an
admixture that would require sufficient alloy pickup
from the base alloy to achieve a heat-treatable composition. (Refer to Table 1.27, Line F, for an illustration of
this effect for a single-V-groove weld in Alloy 6061
plate, 76 mm [3 in.] thick.) When the joint design does
not accommodate sufficient admixture and the weldment is to be postweld heat treated, consideration
should be given to the use of an Al-Si-Mg filler metal
(e.g., Alloy 4643 or 4943) in place of Al-Si filler metal
(e.g., Alloy 4043). (Refer to Table 1.27, Line G, for a
description of the properties of multiple-pass filler
welds in thick Alloy 6061 base metal using Alloy 4643
as the filler metal.)
In cases where complete postweld heat treatment of
a weldment is not practical, the workpieces can be
welded in the solution-heat-treated condition and then
artificially aged after welding. A substantial increase in
the mechanical property values over typical as-welded
strengths can sometimes be obtained in this manner
when high rates of welding speed are employed. For
example, if Alloy 6061 is welded in the T4 temper and
then aged to T6, the strength of the joint may approach
275 MPa (40 ksi), which is a great improvement over
the as-welded strength of 186 MPa (27 ksi). (Refer to
Table 1.27, Line C.) The mechanical properties rarely
attain those of a fully postweld heat-treated weldment
(with solution heat-treatment followed by aging). An
additional benefit that results from welding heat-treatable alloys in the solution-heat-treated T4 condition is
76
76
6061-T6
6061-T4
6061-T6
6061-T6
6061-T4
6061-T6c
A
B
C
D
E
F
G
3
3
0.250
0.125
0.125
0.031
0.031
in.
Auto-GMAW
Multipass
V-Groove
Auto-GMAW
Auto-GMAW
One pass
each side
16.9 mm/s
(39.9 in./min)
SP-DC GTAW
14.8 mm/s
(34.9 in./min)
Single pass
SP-DC
GTAW
8.5 mm/s
(20.1 in./min)
AC-GTAW
40.6 mm/s
(95.9 in./min)
AC-GTAW
40.6 mm/s
(95.9 in./min)
Welding
Process and
Conditions
a. 4643 filler metal was used in line G.
b. Letters in this column are used only as line references.
c. Offset is 0.2% in gauge lengths of 50.8 mm (2 in.).
6.4
3.2
3.2
0.8
0.8
6061-T4
Keyb
mm
Base Alloy
and
Temper
Thickness
186
172
255
248
234
227
227
MPa
27
25
37
36
34
33
33
ksi
Tensile
Strength
97
90
138
165
145
179
145
MPa
14
13
20
24
21
26
21
ksi
Yield
Strengthc
As Welded
13
10
6
6
8
2
6
—
—
—
—
283
—
—
—
—
—
—
41
—
—
Elongation
Tensile
% in
Strength
50.8 mm
(2 in.)
Gauge
MPa
ksi
—
—
—
—
179
—
—
MPa
—
—
—
—
26
—
—
ksi
Yield
Strengthc
—
—
—
—
3
—
—
310
234
296
303
303
—
—
45
34
43
44
44
—
—
276
—
276
276
276
—
—
MPa
40
—
40
40
40
—
—
ksi
Yield
Strengthc
6
5
5
5
—
—
Elongation
% in
50.8 mm
(2 in.)
Gauge
Solution Heat-Treated and Aged After
Elongation
Tensile
% in
Strength
50.8 mm
(2 in.)
Gauge
MPa
ksi
Aged After Welding
Table 1.27
Effect of Welding Conditions on Strength of Groove Joints in Alloy 6061 with Filler Metal ER4043 a
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
43
44
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
Table 1.28
Minimum Shear Strength of Fillet Welds
Shear Strength
Longitudinal
Filler
Alloy
Figure 1.8—Grain Size and Orientation in
the Forging (left) Contributed to the Fracture
(See Arrow) in a 2014-T6 Plate-to-Forging Weld
that hot cracking is minimized due to the more uniform
microstructure that results from microconstituents
being held in solid solution.
The heat-treatable alloys with low copper content in
the 7XXX series (e.g., Alloys 7004, 7005, and 7039)
combine good weldability with high as-welded strength.
These alloys are less sensitive to the rate of quench from
the solution-heat-treating temperature and are solution
heat-treated at lower temperatures than other types of
heat-treatable alloys. These alloys will naturally age
quite rapidly at room temperature (in 2 to 4 weeks) and
then will provide high tensile and yield strengths and
high joint efficiency. An artificial aging treatment after
welding can be used instead of natural aging for
improvement of the yield strength. A full postweld solution heat-treatment followed by precipitation hardening
produces the highest strength.
MPa
Transverse
ksi
7.5
MPa
52
ksi
1100
52
2319a
110
7.5
2319b
152
4043
79
4643
93
13.5
5183
127
18.5
193
28
5356
117
17
179
26
5554
103
15
158
23
5556
138
20
207
30
5654
83
12
124
18
16
110
16
22
200
29
11.5
103
15
138
20
a. Naturally or artificially postweld aged.
b. Solution heat-treated and artificially aged after welding.
exhibit a brittle transition range at low temperatures (as
is typical of many ferrous materials) and they maintain
ductility and resistance to shock loading at extremely
low temperatures. Tensile strength and yield strength of
aluminum improve as temperature decreases.
In some aluminum alloys and tempers, test specimens do not fracture, but merely bend, which results in
high impact values but invalidates the test. In general,
Charpy V-Notch and Izod test values obtained for aluminum should be used only for comparison purposes.
SHEAR STRENGTH
Fillet welds are designed in consideration of shear on
a plane area through the weld. This area is the product
of the effective throat and the length of the weld. The
composition of the weld metal in a fillet weld is nearly
the same as the filler metal because little admixture of
filler metal with the base metal takes place.
Shear strength values of fillet welds made with several filler alloys are shown in Table 1.28. Longitudinal
loading develops the lowest strength and is used as the
basis for minimum design criteria values. Highest aswelded shear strengths are obtained with the high-magnesium-content filler metals in the 5XXX series.
IMPACT STRENGTH
Aluminum weldments hold up quite well under
impact loading, particularly when made with nonheattreatable alloys. Aluminum and aluminum alloys do not
FATIGUE STRENGTH
The fatigue strength of welded structures is obtained
by following the same general rules that apply to other
kinds of fabricated assemblies. Fatigue strength in
weldments is governed by the peak stresses at points of
stress concentration rather than by nominal stresses.
Anything that can be done to reduce the peak stresses
by eliminating stress raisers, such as excessive spatter or
weld reinforcement, (which concentrate imposed cyclic
stresses) will tend to increase the fatigue life of an
assembly under repeated loads.
Figure 1.9 shows average fatigue strength for transverse welds in butt joints in four aluminum alloys. For
the shorter cyclic service life, the fatigue strength
reflects differences in static strength. For the very large
numbers of cycles, however, the difference between the
alloys is small. The fatigue strength of a groove weld
may be significantly increased by means such as remov-
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
45
60
400
MINIMUM
STRESS RATIO (SR) =
STRESS = 0
MAXIMUM
300
40
5154-H34
200
AXIAL
LOADING
3003-F
100
MAXIMUM STRESS IN CYCLE, ksi
MAXIMUM STRESS IN CYCLE, MPa
50
5456-H321
30
EFFECT OF ALLOY
0
10
102
103
104
105
106
107
108
CYCLES TO FAILURE
Figure 1.9—Average Fatigue Strength for Groove Welds in Four Aluminum Alloys
ing weld bead reinforcements or peening the weldment.
If these procedures are not practical, an alternative
would be to blend the reinforcement smoothly into the
base plate to avoid any abrupt changes in thickness. For
welding processes that produce relatively smooth weld
beads, there is little or no increase in strength with further smoothing. The benefit of smooth weld beads can
be nullified by excessive spatter during welding. Adhering spatter creates severe stress raisers in the base metal
adjacent to the weld.
For long fatigue life, the allowable stress for aluminum plate welded with transverse fillet welds is less
than half that of plate joined with transverse groove
welds. Welds in aluminum alloys usually perform very
well under repeated load conditions. Properly designed
and fabricated welded joints will generally perform as
well under repeated load conditions as riveted joints
designed for the same static loading.
EFFECT OF TEMPERATURE
The minimum tensile strengths of aluminum welds at
temperatures other than room temperature are listed in
Table 1.29. The performance of welds closely follows
that of the annealed base metal in the nonheat-treatable
alloys. At temperatures as low as –196°C (–320°F), the
strength of aluminum increases without loss of ductility; therefore, it is a particularly useful metal for lowtemperature or cryogenic applications.
Aluminum alloys lose strength as the temperature
rises above room temperature. Alloys in the 2XXX series
exhibit the highest strength at elevated temperatures.
Alloys in the aluminum-magnesium group with a magnesium content of 3.5% or more are not recommended
for sustained temperatures exceeding 66°C (150°F)
because these alloys are susceptible to stress corrosion.
FRACTURE CHARACTERISTICS
The fracture characteristics of a weldment can be
described in terms of resistance to rapid crack propagation at elastic stresses or the occurrence of plastic deformation in the presence of stress raisers (avoiding the
low-energy initiation and propagation of cracks). Resistance to rapid crack propagation can be measured in
terms of tear resistance (notch toughness).
46
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
Table 1.29
Ultimate Tensile Strength at Various Temperatures for
Gas Metal Arc and Gas Tungsten Arc Welded Groove Joints in Aluminum Alloys
Ultimate Tensile Strength
–184°C (–300°F)
a.
b.
c.
d.
–129°C (–200°F)
–73°C (–100°F)
149°C (300°F)a
260°C (500°F)a
MPa
ksi
MPa
ksi
35.0
214
31.0
131
19.0
50.0
262
38.0
152
22.0
38°C (100°F)
Alloy and
Temper
Filler
Alloy
MPa
ksi
MPa
ksi
MPa
ksi
MPa
ksi
2219-T37b
2319
334
48.5
276
40.0
248
36.0
241
2219c
2319
445
64.5
410
59.5
379
55.0
345
3003
1100
190
27.5
148
21.5
121
17.5
97
14.0
66
9.5
34
5.0
5052
5356
262
38.0
214
31.0
183
26.5
172
25.0
145
21.0
72
10.5
5083a
5183
376
54.5
317
46.0
279
40.5
276
40.0
—
—
—
—
5086a
5356
331
48.0
279
40.5
245
35.5
241
35.0
—
—
—
—
5454
5554
303
44.0
255
37.0
221
32.0
214
31.0
179
26.0
103
15.0
5456
5556
386
56.0
327
47.5
293
42.5
290
42.0
—
—
—
—
6061-T6b
4043
238
34.5
207
30.0
183
26.5
165
24.0
138
20.0
41
6.0
6061c, d
4043d
379
55.0
341
49.5
317
46.0
290
42.0
217
31.5
48
7.0
Alloys not listed at 149°C and 260°C (300°F and 500°F) are not recommended for use at sustained operating temperatures higher than 66°C (150°F).
As-welded.
Postweld solution heat-treated and aged.
4643 filler alloy for 19 mm (0.750 in.).
A fracture toughness test is useful for this purpose
but only for material with relatively low ductility. Most
weldments in aluminum alloys are too ductile for this
test to be of significance. Plastic deformation and redistribution of load to adjacent regions that take place in a
weldment are expressed as notch toughness. The relationship of the tensile strength of notched specimens to
yield strength of a joint provides an alternative but generally imprecise measure of these characteristics.
Regardless of the criteria used to measure fracture
characteristics, and depending on the filler metal used,
welds in aluminum alloys are usually at least as tough
as the base aluminum alloy. In nonheat-treatable alloys,
the heat of welding anneals a narrow zone on each side
of the weld and causes the weld to have the same high
resistance to rapid crack propagation as annealed material, and much more than cold-worked base metal. The
elongation of specimens measured across a weld in
cold-worked base metal may be slight, suggesting that
this is not the case. This low value is actually the result
of the varied strength of regions within the gauge length
and the resultant strain concentration at the weld.
The same situation exists for heat-treated alloys in
the as-welded condition, in which tear resistance is
much greater than that of the heat-treated base metal.
Heat treatment or aging after welding increases the
strength of the weld and brings the fracture characteris-
tics more in line with those of the base metal, particularly when the base metal and filler metals are of
essentially the same chemical composition. When the
composition of a heat-treatable filler alloy differs from
that of the base metal (for example, in a weldment of
Alloy 4043 filler metal and Alloy 6061 base metal) the
weld metal may be less tough than the base metal after
postweld heat treating of the weldment. The relative
merits of aluminum alloy weldments based on notch
toughness and tear resistance are shown in Figure 1.10.
The ratio of notch tensile strength to tensile yield
strength is shown on the left axis, whereas the unit
propagation energy of tear resistance is on the right
axis.
CORROSION RESISTANCE
Many aluminum alloys can be welded without reducing resistance to corrosion. In general, the welding process does not affect corrosion resistance, except when
oxyfuel gas welding or shielded metal arc welding is used
and residual flux residue is not completely removed. The
excellent corrosion resistance of the nonheat-treatable
alloys is not changed appreciably by welding. Combinations of these alloys have good resistance to corrosion;
however, for applications involving service at elevated
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
NOTCH TENSILE STRENGTH/TENSILE
YIELD STRENGTH RATIO
UNIT PROPAGATION ENERGY
2800
4200
2
2.8
3200
4800
2.4
3600
2.0
3000
1.6
2400
1.2
1800
UNIT PROPAGATION ENERGY, kJ/m
TENSILE YIELD STRENGTH
RATIO =
NOTCH TENSILE STRENGTH
3.2
2400
2000
1600
1200
0.8
1200
0.4
600
400
0
0
0
BASE
2219 2219 3003 5052 5083 5083 5154 5454 5456 6061 6061 6061 7005 7039
METAL
FILLER
b
c
c
a
a
a
a
2219 2219 1100 5052 5183 5356 5654 5554 5556 4043 4043 5356 5356 5039
ALLOY
47
800
UNIT PROPAGATION ENERGY, in. lb/in.2
AWS WELDING HANDBOOK
Notes:
a. As-welded condition.
b. Aged after welding.
c. Heat treated and aged after welding.
Figure 1.10—(Left Axis) Ratio of Notch Tensile Strength
to Tensile Yield Strength and (Right Axis) Relative Tear
Resistance Ratings of Aluminum Alloy Weldments
temperature (higher than 66°C [150°F]), limitations are
placed on the amount of cold work that is permissible
for some of the alloys in the 5XXX series, particularly
those with high magnesium content, which may show
susceptibility to stress corrosion.
The aluminum-magnesium-silicon alloys (e.g., 6061
and 6063) have high resistance to corrosion in both
the unwelded and welded condition and are not noticeably affected by factors such as temper, operating
temperature, type and magnitude of stress, and service
environment.
Resistance to corrosion may be lowered by the heat
of welding in the 2XXX and 7XXX series of heat-treatable aluminum alloys, which contain substantial
amounts of copper and zinc. Precipitation at the grainboundary of the HAZ of these alloys creates an electri-
cal potential different from the remainder of the weldment, and in the presence of an electrolyte, selective
corrosion at the grain boundaries may take place. This
corrosion can proceed rapidly in the presence of stress.
Postweld heat treatment provides a more homogeneous structure and improves the corrosion resistance
of heat-treatable alloys. If the assembly cannot be solution heat-treated and artificially aged after welding, better resistance to corrosion can still be achieved if the
original material is welded in the T6 temper rather than
in the T4 temper.
The corrosion resistance of welded assemblies fabricated of clad metal is superior to that of welded assemblies in unclad material. Protection by painting is
recommended when welded joints in base alloys in the
2XXX or 7XXX series are employed in outdoor service.
48
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
ARC WELDING OF ALUMINUM
Properties of the specific aluminum alloy, joint configuration, strength requirement, appearance, and cost
are factors that determine the choice of the welding
process or joining method. Each method has advantages and limitations. For most applications, the conventional equipment and techniques used to join other
metals can be used to join aluminum. Occasionally, specialized equipment or techniques, or both, may be
required.
JOINT GEOMETRY
Aluminum joints require smaller root openings and
larger groove angles than those generally used for steel
because aluminum weld metal is more fluid and welding gun nozzles are larger. Typical joint geometries for
arc welds in aluminum are shown in Figure 1.11.
The special joint geometry shown in Figure 1.12 is
recommended for gas tungsten arc welding (GTAW) or
gas metal arc welding (GMAW) when only one side of
the joint is accessible and a smooth root surface is
required. The effectiveness of this design for complete
joint penetration depends on the surface tension of the
weld metal. This design can be used with section thicknesses greater than 3.2 mm (0.125 in.) and in all welding positions. The abutting sections are designed so that
complete joint penetration is possible with the first weld
pass. It should be noted that this design has a large
groove area and requires a relatively large amount of
filler metal to fill the joint. Distortion is always greater
with this design than with conventional joint designs.
The principal application is for circumferential joints in
aluminum pipe.
For thick plate, U-groove or double V-groove welds
are preferred over the V-groove design to minimize the
amount of deposited metal and to permit access to the
weld root. Special joint geometries, as shown in Figure
1.13, may be warranted to minimize porosity caused by
entrapment of hydrogen while welding in the horizontal
position.
AWS WELDING HANDBOOK
The electrode is shielded by an inert gas that flows
through the nozzle of the GTAW torch. The shielding
gas is usually argon, but helium or a mixture of argon
and helium can be used. The weld metal may be composed of base metal alone or a mixture of base and filler
metal. Filler metal is typically added, but in some cases,
is not required. The filler metal is not melted directly by
the arc, but by the molten base metal in the weld pool.
During welding, if the filler metal contacts the tungsten
electrode or if the tungsten electrode touches the weld
pool, both the weld bead and the electrode become contaminated.
Equipment
Several types of power sources are used for the
GTAW process: transformers with magnetic amplifier,
transformers with phase control, and inverters. Details
of the GTAW process and associated equipment and
consumables are discussed in Chapter 3 of Volume 2,
Welding Handbook, 9th edition.7
Transformer Magnetic-Amplifier Power Source.
The first power sources for GTAW were transformer
magnetic-amplifier (Mag-Amp) machines, consisting of
an iron core transformer and a magnetic amplifier to
control the current. As with all GTAW power sources,
these were the constant-current type with a “drooping”
volt-ampere characteristic, in which the slope of the
volt-ampere curve was relatively steep so that a change
in the arc voltage (arc length) would not create a major
change in the arc current. They also produced a true
sine wave while in the ac mode. These power sources
were generally superseded by phase-controlled power
sources, which were introduced in the 1970s.
Transformer Phase-Controlled Power Sources.
GAS TUNGSTEN ARC WELDING
Like the transformer magnetic ampere machines, the
phase-controlled machines, referred to as square-wave
silicon-controlled rectifier (SCR) power sources, also
use a bulky 50 Hz to 60 Hz transformer. The SCR
design enables the machine to produce an ac waveform
that is closer to square when compared to the sine
wave. It provides limited wave-shaping capability
(balance control) and has a closed-loop feedback for
consistent weld output.
The gas tungsten arc welding (GTAW) process uses
an arc between a tungsten electrode (nonconsumable)
and the weld pool. The process is used with shielding
gas and without the application of pressure. An arc,
alternating current (ac) or direct current electrode negative (DCEN), is established between the base metal and
the nonconsumable tungsten electrode.
7. Refer to Welding Handbook, Welding Processes, Part 1, Chapter
1, Arc Power Sources, and Chapter 3, Gas Tungsten Arc Welding,
American Welding Society (AWS) Welding Handbook Committee,
2004, ed. A. O’Brien, Vol. 2, Welding Handbook, 9th ed., Miami:
American Welding Society. See Appendix B of this volume for a
detailed description of chapter contents for the five volumes of Welding
Handbook, 9th ed.
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
R
R
T
T
TEMPORARY
BACKING
2T
T
4
(A)
(B)
60°–90°
60°, 90°
or 110°
R
R
(C)
A to B
C
(D)
60°
90°
A to B
R
T
R
A to B
TEMPORARY
BACKING
E
(E)
T
4
(F)
60°
A to B
R
R
T
T
F
BACKING
STRIP
BACKING
STRIP
F
T (MAX. = D)
T (MAX. = D)
(G)
(H)
60°
T MAX.
2
TEMPORARY
BACKING
T
(I)
Key:
A = 1.6 mm (0.062 in.)
B = 2.4 mm (0.094 in.)
(J)
D = 9.5 mm (0.375 in.)
E = 12.7 mm (0.500 in.)
(K)
R = root opening
T = thickness
Figure 1.11—Typical Joint Geometries for Arc Welds in Aluminum
49
50
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
30°
R
A
B
Dimensions
Process
A
B
R
AC-GTAW
4.8 mm
(0.19 in.)
1.6 to 2.4 mm
(0.06 to 0.09 in.)
1.6 mm
(0.06 in.)
DCEN-GTAW
and GMAW
1.6 mm
(0.06 in.)
2.4 mm
(0.09 in.)
1.6 mm
(0.06 in.)
Inverter Power Sources. Although inverters were
introduced in the 1940s, electronic technology was not
developed for use in the GTAW ac process until the
1990s. Instead of operating at a common input frequency of 50/60Hz, inverters boost the frequency as
much as 1000 times that of the input frequency; this
drastically reduces the number of turns of the transformer coil and reduces the core area resulting in a
machine much smaller and lighter in weight than the
transformer power source.
Inverter power sources produce a true square wave.
With this technology, ac power sources incorporate
fast-switching electronics capable of switching current
up to 50,000 times per second, thus the inverter power
source can be much more responsive to the welding arc.
These machines provide increased control of balancing
the waveform, and are able to change output frequency
from 20 Hz to 400 Hz.
Welding Current and Polarity
Aluminum can be welded with the gas tungsten arc
welding process using ac or DCEN. Direct current electrode positive (DCEP) is rarely used because of the limited current-carrying ability of the tungsten electrode.
Figure 1.12—Special Joint Geometry
for Complete Joint Penetration for
Arc Welding from One Side Only
ALUMINUM
BACKING
STRIP
C MAX.
B MAX.
C MAX.
60°
60° MIN.
45°
60° MIN.
A to B
WELDED FROM
ONE SIDE
Key:
A to B
10°–15°
15°
A = 0 mm (0 in.)
10°–15°
WELDED FROM ONE
OR BOTH SIDES
B = 1.6 mm (0.062 in.)
WELDED FROM
BOTH SIDES
C = 3.2 mm (0.125 in.)
Figure 1.13—Special Joint Geometries for Welding
Aluminum in the Horizontal Position Using Arc Welding
-
AWS WELDING HANDBOOK
Current type
Electrode
polarity
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
51
DC
DC
Balanced AC
Unbalanced AC
Negative
Positive
50% Negative
50% Positive
70% Negative
30% Positive
None
Very wide zone
Wide zone
Narrow zone
70% at work end
30% at electrode end
30% at work end
70% at electrode end
50% at work end
50% at electrode end
70% at work end
30% at electrode end
Deep; narrow
Shallow; wide
Medium
Deep; medium
Excellent
e.g., 3.18 mm (0.125 in.)—
400 A
Poor
e.g., 6.35 mm (0.250 in.)—
120 A
Good
e.g., 3.18 mm (0.125 in.)—
225 A
Very good
e.g., 3.18 mm (0.125 in.)—
325 A
Electron and
ion flow
Joint
penetration
characteristics
Oxide cleaning
action
Heat balance in
the arc (approx.)
Joint
penetration
Electrode
capacity
Figure 1.14—Characteristics and Effects of Current Type
and Electrode Polarity for Gas Tungsten Arc Welding
This makes welding in this polarity very difficult, and,
in general, impractical for GTAW. The characteristics
and effects of current type and electrode polarity are
illustrated in Figure 1.14.
Direct Current Electrode Negative. Direct cur-
rent electrode negative (DCEN) may be used for gas
tungsten arc welding. This polarity requires the use of
100% helium and thoriated, ceriated, or lanthanated
tungsten electrodes.
Welding aluminum using DCEN has proven advantageous for many automatic welding operations, especially when welding heavy sections. Because there is less
tendency to overheat the electrode, smaller electrodes
can be used for a given welding current. This contributes to keeping the weld bead narrow. Figure 1.15
shows an example of a properly prepared tungsten electrode for use with DCEN.
The use of DCEN provides a greater rate of heat
input than can be obtained with ac. Greater heat
density is developed in the weld pool, which results
in a weld that is deeper and narrower, as shown in
Figure 1.16.
Figure 1.15—Properly Prepared Tungsten
Electrode for Manual and Mechanized
Gas Tungsten Arc Welding Using
Direct Current Electrode Negative
52
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
preweld cleaning of the base metal is necessary. This
usually involves degreasing, chemical cleaning, wire
brushing, scraping, or filing the joint area.
Gas tungsten arc welding with DCEN has distinct
advantages compared to ac, particularly with
mechanized welding, during which a consistently
short arc length can be easily maintained. The deep
joint penetration made possible with helium shielding
is particularly useful for welding thick sections. A
much higher travel speed on thin sections is possible with
DCEN than with ac.
Direct Current Electrode Positive. Welding with
direct current electrode positive (DCEP) provides good
surface cleaning action and permits welding of thin
aluminum sections with sufficient current to maintain a
stable arc. Argon shielding should be used because helium
or argon-helium mixtures would contribute to electrode
overheating. This causes the tungsten electrode to ball
excessively, as shown in Figure 1.17, and would require
much larger electrodes. The weld bead would tend to be
wide and joint penetration would be shallow.
Photograph courtesy of Miller Electric Company
Figure 1.16—Deep and Narrow Weld
Pool in Aluminum Produced by the Gas
Tungsten Arc Welding Process Using
Direct Current Electrode Negative
and Pure Helium Shielding
The greater heat input of DCEN used with GTAW
produces rapid melting of the base metal and excellent
joint penetration. It is not necessary to preheat thick
sections before welding. Edge preparation can be eliminated and the groove can be reduced in size so that less
filler metal is required. The heating rate is rapid with
DCEN; the weld pool is formed immediately, which
results in less distortion of the base metal.
The surface appearance of an aluminum bead while
welding with DCEN differs from that of ac welds.
Welders accustomed to using ac expect to see clean,
bright metal on the weld surface during welding; conversely, while welding with DCEN, the weld pool
appears dirty and is difficult to see. Surface oxide does
not indicate incomplete fusion, porosity, or inclusions
in the weld. When welding is completed, the welded
surface is dulled by an oxide film, which can be easily
removed by light wire brushing. There is no cleaning
action by the arc when using DCEN, so a thorough
Figure 1.17—Excessive Balling
on a Tungsten Electrode
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
53
It should be noted that DCEP is not commonly used
to weld aluminum because the arc tends to wander and
DCEP contributes to extreme balling of the electrode.
Alternating Current. Alternating current (ac) is the
most commonly used polarity for welding aluminum.
The oxide on the surface of aluminum alloys is removed
by the same cleaning action provided by the positive
portion of the ac waveform; the negative portion
provides most of the depth of fusion during
welding. Shielding gases for welding in ac can be
100% argon, 100% helium, or mixtures of argon and
helium. Technological advances in power sources for
GTAW have resulted in different ac waveforms: sine
waves, square waves, and true square waves.
The sine wave shown in Figure 1.18 is typical of
older power source models; however, this waveform
can be reproduced electronically in inverter power
sources. The duration of time between the electrode
positive and the electrode negative portion of the cycle
cannot be adjusted in magnetic-amplifier power sources
and the transition time between each is much slower.
Less time spent at the peak of the electrode positive or
electrode negative portion of each cycle relates to
reduced heat on the negative portion and excessive heat
on the positive portion. This requires larger electrode
diameters to overcome erosion but provides excellent
cleaning action.
After a change in technology in the 1970s, square
waveforms, which were based on the transformer
power source, were closer to square when compared to
the sine wave, as illustrated in Figure 1.19. The square
portion of the waveform is enhanced at the peak of the
Figure 1.19—A Square Waveform
electrode positive and electrode negative portions of the
waveform. This is a result of transition times between
the positive and negative portions occurring at a much
faster rate, which produces a much more stable arc.
This allows more time at the peak portions of the electrode positive and electrode negative cycles, resulting in
more heat to the workpiece during the negative cycle
and more time for the positive cycle (which provides
oxide removal or cleaning action). This waveform
design provides control (although limited) of the time
between electrode positive and electrode negative,
which produces more heat in the weld and allows less
heat back to the tungsten electrode.
A true square wave (refer to Figure 1.18) is associated with the inverter power source technology developed in the 1990s. It is regarded as a true square wave
because when the peak portion of the positive or negative part of the cycle occurs, the corners are truly
square; also, more time is spent at the peak portion
Figure 1.18—Representations of a Sine Wave,
a Square Wave, and a True Square Wave
54
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
than that provided by previous square-wave designs.
The transition time from electrode positive to electrode
negative also happens much faster and allows the arc to
remain responsive as it passes through the 0 crossing
point of the cycle without the aid of high frequency. In
addition, the inverter design provides operators with
greater control over balance (i.e., the ratio of electrode
positive to electrode negative) and output frequency.
With conventional square-wave design, the output frequency is limited to 60 Hz; with the advanced squarewave design, the frequency can be selected from a range
of 20 Hz to 400 Hz, depending on the capacity provided by the power source manufacturer. The advan-
tages are increased travel speeds and better directional
control of the arc through the use of a pointed tungsten
electrode, which in turn provides more heat to the weld
and allows less heat back to the tungsten electrode.
Welding Procedures
Table 1.30 lists typical procedures for manual gas
tungsten arc welding of butt joints with ac. Table 1.31
shows typical procedures for manual GTAW for fillet
welds with ac, and Table 1.32 lists this information for
edge and corner joints with alternating current. Data in
Table 1.30
Typical Procedures for Manual Gas Tungsten Arc Welding
of Butt Joints in Aluminum with AC and Argon Shielding
Section
Thickness
mm in.
1.6
2.4
3.2
4.8
6.4
9.5
0.062
0.094
0.125
0.188
0.25
0.375c
Welding
Joint
Positiona Geometryb
in.
No. of
Weld
Passes
Root Opening
mm
Filler Rod
Diameter
mm
in.
Electrode
Diameter
mm
in.
Welding
Current,
A
Travel Speed
mm/s
in./min
F, V, H
B
0–1.6
0–0.062
1
1.6, 2.4
0.062, 0.094
1.6
0.062
60–80
3.4–4.2
8–10
O
B
0–1.6
0–0.062
1
1.6, 2.4
0.062, 0.094
1.6
0.062
60–75
3.4–4.2
8–10
F
B
0–2.4
0–0.094
1
3.2
0.125
2.4
0.094
95–115
3.4–4.2
8–10
V, H
B
0–2.4
0–0.094
1
2.4, 3.2
0.094, 0.125
2.4
0.094
85–110
3.4–4.2
8–10
O
B
0–2.4
0–0.094
1
2.4, 3.2
0.094, 0.125
2.4
0.094
90–110
3.4–4.2
8–10
F
B
0–3.2
0–0.125
1–2
3.2, 4.0
0.125, 0.156
2.4
0.094
125–150
4.2–5.1
10–12
V, H
B
0–2.4
0–0.094
1–2
3.2
0.125
2.4
0.094
110–140
4.2–5.1
10–12
O
B
0–2.4
0–0.094
1–2
3.2, 4.0
0.125, 0.156
2.4
0.094
115–140
4.2–5.1
10–12
F
D—60°
0–3.2
0–0.125
2
4.0, 4.8
0.156, 0.188
3.2
0.125
170–190
4.2–5.1
10–12
V
D—60°
0–2.4
0–0.094
2
4.0
0.156
3.2
0.125
160–175
4.2–5.1
10–12
H
D—90°
0–2.4
0–0.094
2
4.0
0.156
3.2
0.125
155–170
4.2–5.1
10–12
O
D—110°
0–2.4
0–0.094
2
4.0
0.156
3.2
0.125
165–180
4.2–5.1
10–12
F
D—60°
0–3.2
0–0.125
2
4.8
0.188
4.0
0.156
220–275
3.4–4.2
8–10
V
D—60°
0–2.4
0–0.094
2
4.8
0.188
4.0
0.156
200–240
3.4–4.2
8–10
H
D—90°
0–2.4
0–0.094
2–3
4.0, 4.8
0.156, 0.188
4.0
0.156
190–225
3.4–4.2
8–10
O
D—110°
0–2.4
0–0.094
2
4.8
0.188
4.0
0.156
210–250
3.4–4.2
8–10
F
D—60°
0–3.2
0–0.125
2
4.8, 6.4
0.188, 0.25
4.8
0.188
315–375
3.4–4.2
8–10
F
E
0–2.4
0–0.094
2
4.8, 6.4
0.188, 0.25
4.8
0.188
340–380
3.4–4.2
8–10
V
D—60°
0–2.4
0–0.094
3
4.8
0.188
4.8
0.188
260–300
3.4–4.2
8–10
V, H, O
E
0–2.4
0–0.094
2
4.8
0.188
4.8
0.188
240–300
3.4–4.2
8–10
H
D—90°
0–2.4
0–0.094
3
4.8
0.188
4.8
0.188
240–300
3.4–4.2
8–10
O
D—110°
0–2.4
0–0.094
3
4.8
0.188
4.8
0.188
260–300
3.4–4.2
8–10
a. Welding positions
F = flat
H = horizontal
V = vertical
O = overhead
b. Refer to Figure 1.3(B), (D), and (E). Angle dimension is the appropriate groove angle.
c. May be preheated. Caution: Preheat above 121°C (250°F) may significantly affect the as-welded strength of heat-treatable aluminum alloys.
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
55
Table 1.31
Typical Procedures for Manual Gas Tungsten Arc Welding
of Fillet Welds in Aluminum with AC and Argon Shielding
Section Thickness
No. of
Weld
Passes
mm
in.
mm
Filler Rod Diameter
Electrode Diameter
in.
Welding
Current,
A
mm/s
in./min
70–110
3.4–4.2
8–10
Travel Speed
mm
in.
Welding
Positiona
1.6
0.062
F, H, V
1
1.6, 2.4
0.062, 0.094
1.6
0.062
O
1
1.6, 2.4
0.062, 0.094
1.6
0.062
65–90
3.4–4.2
8–10
24
0.094
F
1
2.4, 3.2
0.094, 0.125
2.4
0.094
110–145
3.4–4.2
8–10
3.2
4.8
6.4
9.5
0.125
0.188
0.25
0.375b
H, V
1
2.4
0.094
2.4
0.094
90–125
3.4–4.2
8–10
O
1
2.4
0.094
2.4
0.094
110–135
3.4–4.2
8–10
F
1
3.2
0.125
2.4
0.094
135–175
4.2–5.1
10–12
H, V
1
3.2
0.125
2.4
0.094
115–145
3.4–4.2
8–10
O
1
3.2
0.125
2.4
0.094
125–155
3.4–4.2
8–10
F
1
4.0
0.156
3.2
0.125
190–245
3.4–4.2
8–10
H, V
1
4.0
0.156
3.2
0.125
175–210
3.4–4.2
8–10
O
1
4.0
0.156
3.2
0.125
185–225
3.4–4.2
8–10
F
1
4.8
0.188
4.0
0.156
240–295
3.4–4.2
8–10
H, V
1
4.8
0.188
4.0
0.156
220–265
3.4–4.2
8–10
O
1
4.8
0.188
4.0
0.156
230–275
3.4–4.2
8–10
F
2
4.8
0.188
4.8
0.188
325–375
3.4–4.2
8–10
V
2
4.8
0.188
4.8
0.188
280–315
3.4–4.2
8–10
H
3
4.8
0.188
4.8
0.188
270–300
3.4–4.2
8–10
O
3
4.8
0.188
4.8
0.188
290–335
3.4–4.2
8–10
a. Welding positions
F = flat
H = horizontal
V = vertical
O = overhead
b. May be preheated. Caution: Preheats above 121°C (250°F) may significantly affect the as-welded strength of heat-treatable aluminum alloys.
Table 1.32
Typical Procedures for Manual Gas Tungsten Arc Welding
of Edge and Corner Joints in Aluminum with AC and Argon Shielding
Section Thickness
Joint
Geometrya
No. of
Weld
Passes
mm
in.
Filler Rod Diameter
Electrode Diameter
mm
in.
Welding
Current,b, c
A
Travel Speedc
mm
in.
mm/s
in./min
1.6
0.062
I, K
1
1.6, 2.4
0.062, 0.094
1.6
0.062
60–85
4.2–6.8
10–16
2.4
0.094
I, K
1
3.2
0.125
1.6
0.062
90–120
4.2–6.8
10–16
3.2
0.125
I, K
1
3.2, 4.0
0.125, 0.156
2.4
0.094
115–150
4.2–6.8
10–16
4.8
0.188
J, K
1
4.0
0.156
3.2
0.125
160–220
4.2–6.8
10–16
6.4
0.250
J, K
2
4.8
0.188
3.2
0.125
200–250
3.4–5.1
8–12
a. See Figure 1.3.
b. Use current in low end of range for welding in the horizontal and vertical positions.
c. Higher welding current and travel speed may be used for corner joints if temporary backing is employed.
56
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
these tables are intended to serve only as guides to
establish welding procedures for a specific application. 8
Welding Technique
For manual gas tungsten arc welding of aluminum,
the torch is held in one hand and the filler rod (if used)
in the other. To reduce the possible occurrence of tungsten inclusions in weld starts, the arc can be initiated on
a starting block in the joint or away from the surface of
the base metal. The arc is then broken and restarted in
the joint while the tungsten electrode is still warm. The
arc is held at the starting point until the metal melts and
a weld pool is established. Establishment and maintenance of a suitable weld pool are important, and welding must not proceed ahead of the weld pool.
If filler metal is required, it can be added to the front,
or leading edge, of the weld pool. The welder moves
both hands in unison. Different techniques can be used,
depending on the individual welder and the welding
procedure followed. Some welders use a slight backward and forward motion along the joint while timing
the dipping of the filler material; others travel consistently straight across the joint and dip the filler material
with no manipulation. Regardless of the personal technique, the tungsten electrode should never touch the
filler rod or the weld pool, and the end of the filler rod
should not be withdrawn from the argon shield.
A short arc length must be maintained to obtain sufficient joint penetration, to avoid undercutting, and
also to prevent excessive weld bead width, loss of control of penetration, and weld contour. One rule is to use
an arc length approximately equal to the diameter of
the tungsten electrode. The arc and weld pool must be
observed by the welder, and this is more difficult with a
shorter arc length.
The gas nozzle should have a minimum inside diameter of three times the diameter of the electrode. If there
is discoloration of the tungsten electrode prior to welding, it may be because the shielding gas nozzle is too
small.
The torch should be held perpendicular to the center
of the joint, then lowered to a forehand angle of about
70° to 85° from the plane of the workpiece, and should
progress toward the filler metal, as shown in Figure
1.20(A), (B), and (C). Torch orientation for a corner
joint is shown in 1.20(D). When welding unequal sections, the arc angle may need to be changed to create an
equal weld pool on both thicknesses of material. In this
8. For additional information, refer to American Welding Society
(AWS) Committee on Performance Qualification, B2.1-22-015, 2011,
Standard Welding Procedure Specification (SWPS) for Gas Tungsten
Arc Welding of Aluminum (M/P-22 to M/P-22), 18 through 10
Gauge, ER4043 or R4043, in the As-Welded Condition, with or
without Backing (ISBN #978-0-87171), Miami: American Welding
Society.
AWS WELDING HANDBOOK
case, the arc should be directed slightly toward the
thicker section.
Welding speed and frequency of adding filler metal
are dependent on the skill and preference of the welder.
When using the correct current, the travel speed is
higher and less heat is dissipated into the workpiece.
This promotes progressive solidification and better control of the weld bead. When the arc is broken, shrinkage cracks may occur in the weld crater, which may
result in a defective weld. This condition can be prevented by gradually reducing weld current while adding
filler metal to the crater until the weld pool solidifies.
Crater filling devices, such as sequencers, may be used
but must be properly adjusted and timed.
When the tungsten electrode has been contaminated
with aluminum (refer to Figure 1.21), it must be
replaced or cleaned. Minor contamination can be
burned off by increasing the current while holding the
arc on a piece of scrap metal. Severe contamination
should be removed with a grinding wheel or by cutting
off the contaminated portion of the electrode with a
cut-off wheel. Breaking off the contaminated portion of
the tungsten electrode should always be avoided to prevent microfractures and to keep the electrode from
splintering.
Tacking before welding is helpful in controlling distortion. Tack welds should be of ample size and
strength and should have a profile that would not create an inconsistent appearance of the final bead.
Joint Designs
The joint designs previously described are applicable
to GTAW, with minor exceptions. (Refer to Figure 1.11,
Figure 1.12, and Figure 1.13 for illustrations of the
designs and to Table 1.30, Table 1.31, and Table 1.32
for accompanying data.) Welds with a tight fit, such as
edge joints and corner joints in Alloy 3003 and alloys in
the 1XXX series can be made rapidly without the addition of filler metal and will have a good appearance.
However, these joint designs are not recommended for
welding Alloys 6061, 6063, 3004, 5052, 7005, 7039
(or similar alloys that tend to be susceptible to intergranular cracking or grain boundary cracking during
the weld cooling cycle when welded without the addition of filler metal). Smaller V-grooves, U-grooves, and
a thicker root face can be used, and the greater depthto-width weld ratio will result in less weldment distortion, more favorable distribution of residual stress in
the weld, and the use of less filler wire. With slight
modifications, the same joint geometry can be used as
those used in GTAW-DCEN. Welding with inverter
machines that produce a true square wave may permit a
narrower area of joint preparation due to the superior
arc focus these machines provide. This can also help
with distortion caused by excess heat input.
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
(A) Butt Joint and Stringer Bead
(B) Lap Joint
(C) T-Joint
(D) Corner Joint
Figure 1.20—Torch Orientation for Gas Tungsten Arc Welding of (A) Butt Joint
and Stringer Bead, (B) Lap Joint, (C) T-Joint, and (D) Corner Joint
57
58
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
Arc Starting
Figure 1.21—Tungsten Electrode
Contaminated with Aluminum
Shielding Gases for GTAW
Argon is the most commonly used shielding gas, particularly for manual welding, but helium is used in special cases. Arc voltage characteristics when using argon
permit greater arc length variations with minimal effect
on arc power compared to those of helium. Argon also
provides better arc starting characteristics and
improved cleaning action with alternating current.
When the helium content of argon-helium shielding gas
mixtures is increased, arc starting becomes more difficult as more helium is added. Helium is usually selected
for mechanized welding with DCEN, which permits
welding at higher travel speeds than argon.
Helium-argon mixtures are sometimes used to take
advantage of the higher heat input or thermal conductivity of helium while maintaining the favorable arc
characteristics of argon. A mixture of 25% helium and
75% argon is most common and will permit higher
travel speeds with ac.
The appearance and quality of the final weld bead is
greatly influenced by effective shielding gas coverage. If
the weld pool is not properly shielded, contamination
will result. Proper shielding gas flow can be achieved by
using the correct equipment for the application. The
consumables within the torch (nozzle, collet, collet
body and gas lens) have a major effect on successful and
uniform shielding gas coverage. For example, a gas
nozzle that is worn, damaged, or severely discolored
should not be used. Any of these conditions can cause
uneven gas flow. Figure 1.22 illustrates (A) shielding
gas flow without the use of a gas lens, and (B) the
improvement in shielding gas coverage when using a gas
lens. Both the nozzle and the gas lens will provide
proper shielding.
Successful establishment of the arc in gas tungsten
arc welding requires that certain conditions be met
when striking the arc: proper shielding gas coverage,
correct starting amperage, and proper workpiece preparation. These conditions can create enough heat in the
tungsten electrode to allow easy emission of electrons
and to keep the arc stable. Other factors that will result
in successful arc starts include the composition of the
tungsten electrode alloy, electrode preparation and condition, type of gas, gas flow and pressure, condition of
the gas lines, and condition and length of the torch.
Three techniques can be used to start the arc: scratch
start, lift-arc, and high frequency.
Scratch Start. Starting an arc with the scratch technique involves contact between the tungsten electrode
and the workpiece. The output of the power source is
set before the electrode touches the workpiece. This arc
starting method is not used as frequently as in the past
because other options provide better results. When output is set and the electrode touches the workpiece, there
is a high possibility of tungsten inclusions at the beginning of the weld. These inclusions are considered discontinuities in the weld bead, which can subsequently
lead to a failure.
Lift-Arc. The lift-arc technique also involves contact
between the tungsten electrode and base metal, but with
this method the power source does not supply welding
output until the machine senses that the tungsten electrode has been touched to the workpiece and lifted
from it. Compared to the scratch-start method, the liftarc technique greatly reduces the possibility of tungsten
inclusions at the beginning of a weld bead because no
welding current is present when the tungsten touches
the workpiece. If current is present when the electrode
touches the workpiece, it gets hot, which may cause the
tip of the electrode to detach from the main body and
become embedded in the workpiece.
High Frequency. A high-frequency arc start does not
require contact between the electrode and the base
metal. High frequency is a high voltage (4 kV to 14 kV),
low-amperage ac sine-wave charge that jumps between
the tungsten electrode and the base metal. The frequency of this voltage charge is about 1 MHz to 2 MHz.
Starting an arc with high frequency involves placing the
tungsten electrode about 3 mm (0.125 in.) away from
the workpiece. When the electrode is in place, the
remote control (foot, hand, or fingertip) is turned to the
on position; high frequency will jump from the electrode to the workpiece and the arc will be established.
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
(A)
59
(B)
Photograph courtesy of Miller Electric Company
Figure 1.22—(A) Gas Flow with Standard Shielding Gas
Coverage and (B) Improved Shielding with a Gas Lens
Electrodes
Several types of tungsten electrodes may be used:
pure tungsten and lanthanated, zirconiated, ceriated,
and thoriated. The choice of electrode depends on the
welding current and the application. Figure 1.23 shows
the tungsten electrodes described in this section. They
are color-coded for identification: pure tungsten is
green, 1% lanthanum is black, 2% cerium is gray (formerly orange), 1.5% lanthanum is gold, 2% lanthanum
is blue, 1% thorium is yellow, 2% thorium is red, and
1% zirconium is brown.
Pure Tungsten. The pure tungsten electrodes (EWP
[green]) are unalloyed and have a minimum purity of
99.5% tungsten. They provide good arc stability and
are used in ac only. These tungsten electrodes are preferred for welding in ac with the older sine-wave
machines, but better options are available for use with
newer welding machines.
2% Cerium. The 2% cerium electrodes (EWCe [gray])
consist of a small percentage of cerium oxide added to
pure tungsten. The EwCe electrodes are preferred for
welding in ac with older sine wave power sources, but
should not be used with inverters. When compared to
pure tungsten, cerium-alloyed tungsten has much better
arc-starting characteristics and provides a much more
stable arc while welding. This high-performance electrode
can be used with ac or dc applications.
When welding with EWCe in ac, the shape of the
electrode tip is maintained very well because of the high
current-carrying capacity of the electrode. This capacity
makes it possible to sharpen the electrode and maintain
a small crown on the tip rather than a large ball, as
would be typical of a pure tungsten electrode.
60
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
for welding in ac, other tungsten alloys may be better
suited for welding in this polarity.
1% Zirconium. The zirconiated tungsten electrode
(EWZr [brown]) is similar to the pure tungsten type. It
will readily create a ball on the end of the electrode and
it is recommended for use only with ac. The EWZr electrode works very well for welding in ac because it has a
higher current-carrying capacity than pure tungsten,
which results in less risk of tungsten inclusions. The
EWZr electrode will retain the tip shape better and will
undergo less tungsten degradation than pure tungsten,
which helps stabilize the arc.
Applications
Figure 1.23—Tungsten Electrodes Color
Coded to Identify Alloying Elements
1%, 1.5%, and 2% Lanthanum. The lanthanated
electrodes (EWLa: 1% [black], 1.5% [gold], and 2%
[blue]) have excellent properties for arc starting, arc stability, and re-ignition. These high-performance electrodes
work well with ac or dc.
The addition of lanthanum oxide increases the maximum current-carrying capacity by approximately 50%
over that of pure tungsten for a given electrode diameter while welding with ac. The lanthanum-alloyed tungsten electrode undergoes less tip wear at the same current
levels, resulting in longer service life and greater resistance to tungsten contamination in the weld. This electrode is preferred over the EWCe for critical applications.
1% and 2% Thorium. The thoriated tungsten electrodes (EWTh: 1% [yellow] and 2% [red]) are commonly used for dc applications because the arc performs
better than when pure tungsten is used. Thorium is
slightly radioactive, however, so when preparing a thoriated tungsten electrode, special safety measures must
be followed to collect and dispose of the tungsten particles so they are not inhaled or ingested.
The thoriated tungsten electrode used with ac does
not ball like the pure tungsten electrode; instead, it
forms ball-like projections or nodules. Special care must
be exercised when welding with this electrode in ac
because of the potential for the nodules to break off the
tip of the electrode and fall into the weld pool.
Although thoriated tungsten can be used successfully
Very precise welds in aluminum can be obtained
when using gas tungsten arc welding. The GTAW process is most often selected for applications in industries
such as aerospace, petrochemical, power generation,
food processing, marine, medical, motorsports, and
tube and pipe manufacturing.
The GTAW process can be used for manual or automated welding applications. Automated applications
vary from simple (i.e., the workpiece rotates or moves
while the torch is in a fixed position) to automated and
robotic, which are used in high-volume production
systems that require consistent and repeatable weld
quality. Automated applications generally use microprocessors, arc length control systems, magnetic arc
oscillators, seam-tracking devices, and cold-wire or hotwire feeders.
GAS METAL ARC WELDING
Gas metal arc welding (GMAW) is an arc welding
process that uses an arc between a continuous filler
metal electrode and the weld pool. The process is used
with shielding from an externally supplied gas and
without the application of pressure.9
A marine application is shown in Figure 1.24, the
welded aluminum hull and superstructure of a patrol
boat under construction for use by the United States
armed forces.
Gas Metal Arc Welding Equipment
The choice of GMAW equipment depends on several
factors, such as welding position, size of the workpieces, amount of welding required bead profile, and
9. Refer to Chapter 4, Gas Metal Arc Welding, in American Welding
Society (AWS) Welding Handbook Committee, 2004, Welding Processes, Part 1, Welding Handbook, vol. 2, A. O’Brien, ed. See Appendix B of this volume for a list of chapter contents for the five volumes
of Welding Handbook, 9th ed.
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
61
Photograph courtesy of The Lincoln Electric Company
Figure 1.24—Construction of the Aluminum Hull and Superstructure
of a Patrol Boat for the United States Armed Forces
desired production rate. As illustrated in Figure 1.25,
the main elements of GMAW equipment are a power
source, electrode feeding mechanism, welding gun, and
shielding gas delivery accessories.
In semiautomatic welding, three drive systems are
available for the delivery of the filler metal (the electrode) from the spool to the arc: push, pull, and pushpull. The electrode drives are illustrated in Figure 1.26.
In the push systems, the drive rolls are located near
the spool and the wire electrode is pushed to the gun
through a conduit that is about 3.0 m to 3.6 m (10 ft to
12 ft) long. The push system is limited to electrodes that
have adequate stiffness to overcome the drag in the conduit and welding gun.
Pull System. In the pull system, the drive rolls are
located at the gun and the electrode is pulled through
the conduit. The pull distance through a conduit is also
limited to 3.0 m to 3.6 m (10 ft to 12 ft) for aluminum
electrodes. The pull-type feed systems are commonly
used with mechanized welding and with some semiautomatic welding guns. These systems are used with
1.1 mm (0.040 in.) and smaller electrode sizes of any
aluminum alloy. In automatic or mechanized welding,
the electrode drive unit is typically located just above
the welding gun.
Push-Pull System. In the push-pull system, the electrode is fed through the conduit by two or more sets of
rolls, one near the spool and one in the gun. This permits conduit lengths of 6.6 m (25 ft) or more. Some systems include conduit modules with a drive at each end.
The push-pull systems are applicable to most types and
sizes of aluminum electrodes.
The selection of a drive system is based largely on the
diameter and tensile strength of the electrode and the
distance between the electrode source and the workpiece. The electrode wire drive motor must have ample
power to feed the wire at uniform speed.
Wire passages should not have sharp bends or discontinuities and should be perfectly aligned.
Drive rolls with U-grooves are preferred over drive
rolls with V-grooves and serrated rolls because the Ugrooves do not mark the wire or leave fine aluminum
shavings in the electrode conduit. The grooves should
be perfectly aligned to minimize friction.
Drive rolls should provide adequate pressure on the
wire to promote a consistent feed rate. Typically, the
drive roll pressure can be changed by adjusting a knob
located on the drive roll assembly. Drive rolls should be
placed as close to the arc as practical, minimizing the
slack in the wire that can occur between the drive rolls
and the contact tip. This practice ensures consistent
transfer of current to the contact tip. Wire straighteners
are sometimes used to reduce the cast in the electrode
wire as it comes off the spool and to keep the electrode
and arc directed properly into the desired location.
62
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
Source: Miller Electric Company.
Figure 1.25—Main Elements of GMAW Equipment (A) Power Source,
(B) Electrode Feeding Mechanism, (C) Welding Gun, and
(D) Shielding Gas Delivery Accessories
Contact Tips. Bent contact tips restrict feeding of
low-strength aluminum electrodes. Contact tips of short
lengths, 19 mm to 25 mm (0.75 in. to 1 in.), minimize
current commutation to the aluminum electrode.
Straight contact tips of sufficient length, 102 mm to
152 mm (4 in. to 6 in.), are preferred so that the electrode has maximum contact with the inside diameter of
the contact tip to minimize arcing. Longer contact tips
also can straighten and stabilize the electrode as it exits
the contact tip. When spool, drive rolls, and electrode
holder are suitably oriented and aligned, wire should
feed uniformly without wandering.
Gas Metal Arc Welding Guns. Handheld guns for
manual and semiautomatic welding may be either
pistol-shaped or may have a straight body with a
curved nozzle. Water-cooled and air-cooled guns are
available.
The guns used in mechanized and automatic welding
are similar to handheld guns and are designed with
varying degrees of bend in the neck of the gun. The
choice of gun design depends on a number of factors;
the most important of these is the ease with which the
gun can be manipulated for a particular joint design
and welding position.
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
63
Source: Miller Electric Company.
Figure 1.26—Gas Metal Arc Drive Systems for Delivery of Filler Metal to the Arc
Power Sources
Welding power sources are designated with one of
two types of electrical characteristics, constant current
or constant voltage, which refer to the change in output
voltage as the welding current varies. Both may be used
satisfactorily if the magnitude of the current stays relatively constant. Differences become evident when the
welding conditions must be adjusted or when transient
events occur, such as arc ignition or changes in gun-toworkpiece distance.
Constant-Current. If a constant-current power source
is used, a slow electrode run-in rate is desirable. If the
wire strikes the workpiece at full welding speed, a constant-current power source will not initiate an arc
because the short-circuit current is not high enough.
This unsatisfactory arc initiation can be overcome by
using a slow run-in, which advances the electrode to the
workpiece at a slow speed, switching to full welding
speed when the arc has been established. When welding
with a semiautomatic constant-current power source, a
touch-start feature is preferred.
64
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
Constant Voltage. The constant-voltage power
source is the most widely used because it has the capability of welding aluminum and can also be used to weld
ferrous metals.
A slow run-in is also desirable with a constant-voltage power source to minimize arcing in the contact tip,
reduce weld buildup at starts, and provide improved
weld fusion at starts. The reduced buildup at starts also
reduces discontinuities when overlapping the start.
High current surges resulting from a fast electrode runin with constant-voltage power causes arcing inside the
contact tip and results in frequent burn-backs when
attempting arc starts. A slow run-in feed for arc starting
substantially reduces the amplitude of current surges,
thus minimizing the arcing.
Shielding Gas
For gas metal arc welding, the shielding gas serves a
secondary function in addition to shielding the molten
metal. Some control over heat distribution to the weld
can be obtained by adjusting the composition of the
shielding gas (argon, helium, or a mixture of the two).
This control influences the shape of the weld-metal
cross section and the speed of welding. Typical cross
sections of weld beads that were made using argon,
helium, and argon-helium mixtures are shown in Figure
1.27. The geometry of the deep, narrow weld cross section created with argon shielding gas can be used to
gain penetration when needed; however, the weld will
be more susceptible to gas entrapment. The addition of
helium to the shielding-gas broadens the cross section
AWS WELDING HANDBOOK
of the weld and increases voltage at the arc. This
increase can be significant, depending on the amount of
helium added; however, the arc becomes unstable as the
helium content approaches more than 75% of the
shielding gas mixture.
Shielding gas is supplied from cylinders or a bulk
supply via pipelines, depending on production requirements. The purity of the shielding gas is of utmost
importance. Gas used for shielding should have a
minimum purity of 99.997% and a dew point of –60°C
(–76°F) or less for argon, and a minimum purity of
99.995% and a dew point of –57°C (–71°F) or lower
for helium. Care must be taken to prevent contamination. Dust, dirt, and moisture can accumulate in the
cylinder fitting, which should be carefully cleaned and
blown out before use. All hose connections and other fittings must be pressure-tight to prevent the entrance of air
or the escape of shielding gas, which will affect the weld.
Argon is the most commonly used shielding gas for
semiautomatic GMAW in the spray transfer mode.
Argon provides excellent arc stability, bead shape, and
penetration, and can be used in all welding positions.
Helium-argon mixtures are preferred for semiautomatic
welding with aluminum-alloy electrodes in the 5XXX
series and when increased heat input is desirable to help
lower porosity levels.
Metal Transfer
The types of metal transfer discussed in this section
include short-circuiting transfer, globular transfer, and
spray transfer of the GMAW process. Because spray
transfer has a very high heat input that can overcome
the high thermal conductivity of aluminum, the spray
transfer mode is the preferred mode of metal transfer
for gas metal arc welding of aluminum.
Short-Circuiting Transfer. In short-circuiting transfer, molten metal from a consumable electrode is deposited during repeated short circuits; the filler metal
actually short circuits (touches) the base metal many
times per second. Some spatter is produced, but this
transfer mode can be used in all welding positions and
on all thicknesses of metal. This type of metal transfer is
generally considered to be unacceptable for welding
aluminum because of problems associated with the
potential for incomplete fusion.
Figure 1.27—Comparative Geometry
of Welds Made with Argon and
Mixtures of Argon and Helium
Globular Transfer. Globular transfer is the transfer
of molten metal in large drops from a consumable
electrode across the arc. Drops are usually larger than
the electrode diameter. Globular transfer does not produce a very smooth weld bead, and some spatter can
occur. This transfer method is usually limited to the flat
and horizontal welding positions, and is not used on
thin metals. Like short-circuiting transfer, the globular
AWS WELDING HANDBOOK
transfer mode is not well suited for welding aluminum
with the GMAW process.
Spray Transfer. Spray transfer is a technique of the
GMAW process, defined as metal transfer in which
molten metal from a consumable electrode is propelled
axially across the arc in small droplets. Argon or an
argon-rich shielding gas is used. When the current is
increased beyond the globular-to-spray transition current the globular transfer mode moves into spray transfer mode. With DCEP, the filler metal will be
transferred across the arc as a stream of fine, superheated droplets when the welding current and arc voltage are above certain threshold values. These values
will depend on the electrode alloy, size, and feed rate.
Spray transfer is a result of a pinch effect on the molten
tip of the consumable filler metal. The pinch effect
physically limits the size of the molten ball that can be
formed on the end of the filler metal, and therefore only
small droplets of metal are transferred rapidly through
the welding arc from the wire to the workpiece.
The spray transfer mode is characterized by high
heat input, a very stable arc, a smooth weld bead, and
very little spatter, thus it is the preferred metal transfer
mode for welding aluminum with the GMAW process.
Table 1.33 shows globular-to-spray transition currents
for several aluminum electrode diameters for welding
aluminum.
Weld profiles for various metal transfer modes of gas
metal arc welding are shown in Figure 1.28.
Pulsed Spray Transfer. Pulsed spray welding can be
used in all positions: flat, horizontal, overhead, and vertical. Metal transfer takes place during the periods of
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
65
Table 1.33
Transition Current for GMAW Spray Transfer
Wire Diameter
mm (in.)
Shielding Gas
Arc Current,
Spray Transition
0.8 (0.030)
100% argon
90 A ± 5 A
0.9 (0.035)
100% argon
110 A ± 5 A
1.2 (0.047)
100% argon
135 A ± 5 A
1.6 (0.062)
100% argon
180 A ± 5 A
high welding current, but ceases during the intervening
periods of low current. The pulsing action reduces the
overall heat input to the base metal and results in good
control of the weld pool and joint penetration. The
lower heat input makes it easier to weld thin aluminum
sections. Pulsed current also allows the use of larger
electrodes than those used with steady current, especially on thin metal.
When the arc length is decreased below a certain
value for a specific electrode and amperage; the size of
the droplets will increase; the properties of the arc will
change; the electrode melting rate will increase; and
deeper penetration is achieved. Decreasing the arc
length can be useful when welding thick sections.
Welding Procedures
Gas metal arc welding procedures depend on many
variables, as indicated by the data in the following
tables.
Figure 1.28—Weld Profiles for Various Gas Metal Arc Transfer Modes
66
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
Table 1.34 shows typical procedures for gas
metal arc welding of groove welds in aluminum alloys,
including data for small-diameter and large-diameter
electrodes. Small-diameter electrodes can be used for
semiautomatic welding in all positions; large-diameter
(3.2 mm [0.125 in.]) or larger electrodes can be used
only in the flat position with automatic welding.
Table 1.35 lists typical procedures for gas metal arc
fillet welds in aluminum alloys, using argon as the
shielding gas.
Table 1.34
Typical Procedures for Groove Welds in Aluminum Alloys Using GMAW with Argon Shielding
Section
Thickness
mm
in.
1.6 0.060
2.4 0.094
3.2 0.125
4.8 0.190
6.4 0.250
9.6 0.380
19.1 0.750
Root Opening
mm
in.
No. of
Weld
Passes
F
A
0
0
1
F
G
2.4
0.09
F
A
0
0
1
F, V, H, O
G
3.2
0.12
1
F, V, H
A
2.4
0.09
1
F, V, H, O
G
4.6
0.19
F, V, H
B
1.6
0.06
F, V, H
F
1.6
0.06
1
1.6
0.06
2
Joint
Welding
Positiona Geometryb
Electrode Diameter
mm
in.
0.8
0.030
0.8–1.2 0.030–0.047
Welding
Shielding Gas
Current
Arc
Flow Ratec
(DCEP), Voltage,
L/min ft3/h
A
V
Travel Speed
mm/s
in./min
70–110
15–20
12
25
10.5–19.0 25–45
10.5–19.0 25–45
90–150
18–22
14
30
110–130
18–23
14
30
9.7–12.7 23–30
0.8–1.2 0.030–0.047 120–150
20–24
14
30
10.2–12.7 24–30
1
0.8–1.2 0.030–0.047 110–135
19–23
14
30
7.6–11.8 18–28
2
0.8–1.2 0.030–0.047 130–175
22–26
16
35
10.3–12.7 24–30
0.8
0.030
1.2
0.047
140–180
23–27
16
35
10.3–12.7 24–30
1.2
0.047
140–175
23–27
28
60
10.3–12.7 24–30
1.2–1.6 0.047–0.062 140–185
23–27
16
35
10.3–12.7 24–30
130–175
23–27
28
60
10.5–14.8 25–35
O
F
F, V
H
H, O
H
4.8
0.19
3
F
B
2.4
0.09
2
1.2–1.6 0.047–0.062 175–200
24–28
19
40
10.3–12.7 24–30
F
F
24
0.09
2
1.2–1.6 0.047–0.062 185–225
24–29
19
40
10.3–12.7 24–30
V, H
F
2.4
0.09
3F,1R
165–190
25–29
21
45
10.5–14.8 25–35
2.4
0.09
3F,1R
1.2–1.6 0.047–0.062 180–200
25–29
28
60
10.5–14.8 25–35
2–3
1.2–1.6 0.047–0.062 175–225
25–29
19
40
10.3–12.7 24–30
1.2–1.6 0.047–0.062 170–200
10.5–16.9 25–40
2.4–4.8 0.09–0.19
2
1.2
1.2
0.047
0.047
O
F
F, V
H
O, H
H
6.4
0.25
4–6
25–29
28
60
F
C—90°
2.4
0.09
1F,1R
1.6
0.062
225–290
26–29
24
50
8.5–12.7 20–30
F
F
2.4
0.09
2F,1R
1.6
0.062
210–275
26–29
24
50
10.3–14.8 24–35
V, H
F
2.4
0.09
3F,1R
1.6
0.062
190–220
26–29
26
55
10.3–12.7 24–30
2.4
0.09
5F,1R
1.6
0.062
200–250
26–29
38
80
10.5–16.9 25–40
4
1.6
0.062
210–290
26–29
24
50
10.3–12.7 24–30
10.5–16.9 25–40
5.9–8.5
14–20
3.3–6.4 0.12–0.25
O
F
F, V
H
O, H
F
H
C—60°
9.6
2.3
0.38
0.09
8–10
1.6
0.062
190–260
3F,1R 1.6–2.4 0.062–0.094 340–400
26–29
26–31
38
28
80
60
F
F
3.2
0.12
4F,1R
2.4
0.094
325–375
26–31
28
60
V, H, O
F
1.6
0.06
8F,1R
1.6
0.062
240–300
26–31
38
80
10.3–12.7 24–30
F
E
1.6
0.06
3F,3R
1.6
0.062
270–330
26–31
28
60
6.8–10.3 16–24
V, H, O
E
1.6
0.06
6F,6R
1.6
0.062
230–280
26–31
38
80
6.8–10.3 16–24
6.4–9.6 0.25–0.38
a. Welding positions
F = flat
H = horizontal
V = vertical
O = overhead
b. Refer to Figure 1.11.
c. Nozzle ID = 16 mm to 19 mm (0.625 in. to 0.750in.).
6.8–8.5
16–20
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
67
Table 1.35
Typical Procedures for Fillet Welds in Aluminum Alloys Using GMAW with Argon Shielding
Section Thickness
No. of
Weld
Passes
mm
Shielding Gas
Flow Rateb
in.
Welding
Current
(DCEP), A
Arc
Voltage,
V
L/min
ft3/h
mm/s
in./min
Electrode Diameter
Travel Speed
mm
in.
Welding
Positiona
2.4
0.094
F, V, H, O
1
0.8
0.030
100–130
18–22
14
30
10–13
24–30
3.2
0.125
4.8
6.4
9.6
19.1
0.19
0.25
0.38
0.75c
F
1
0.8–1.2
0.030–0.047
125–150
20–24
14
30
10–13
24–30
V, H
1
0.8
0.030
110–130
19–23
14
30
10–13
24–30
O
1
0.8–1.2
0.030–0.047
115–140
20–24
19
40
10–13
24–30
F
1
1.2
0.047
180–210
22–26
14
30
10–13
24–30
V, H
1
0.8–1.2
0.030–0.047
130–175
21–25
16
35
10–13
24–30
O
1
0.8–1.2
0.030–0.047
130–190
22–26
21
45
10–13
24–30
F
1
1.2–1.6
0.047–0.062
170–240
24–28
19
40
10–13
24–30
V, H
1
1.2
0.047
170–210
23–27
21
45
10–13
24–30
O
1
1.2–1.6
0.047–0.062
190–220
24–28
28
60
10–13
24–30
F
1
1.6
0.062
240–300
26–29
24
50
8–11
18–25
H, V
3
1.6
0.062
190–240
24–27
28
60
10–13
24–30
O
3
1.6
0.062
200–240
25–28
31
65
10–13
24–30
F
4
2.4
0.094
360–380
26–30
28
60
8–11
18–25
H, V
4–6
1.6
0.062
260–310
25–29
33
70
10–13
24–30
O
10
1.6
0.062
275–310
25–29
40
85
10–13
24–30
a. Welding positions
F = flat
H = horizontal
V = vertical
O = overhead
b. Nozzle ID = 15.9 mm to 19 mm (0.625 in. to 0.750 in.).
c. For thicknesses of 19 mm (0.75 in.) and larger, a double-bevel joint with a 50° minimum groove angle and a 2.3 mm to 3.3 mm (0.09 in. to 0.13 in.) root
face is sometimes used.
Table 1.36 shows typical conditions for flat-position
groove welds in aluminum alloys using large-diameter
electrodes.
Table 1.37 shows typical procedures for gas metal
arc welding of fillet welds in aluminum alloys using
large-diameter electrodes with argon shielding.
Constant-voltage power and constant-speed electrode drives are typically used with small- diameter
electrodes less than 1.2 mm (0.045 in.). The electrode
feed rate is adjusted to obtain the desired welding current for good fusion and penetration. The arc length
(voltage) is critical with respect to good fusion with the
groove faces. If the voltage is too low, short circuiting
will take place between the electrode and the weld pool.
Welding procedures for pulsed spray welding depend
on the design of the power source. The power source
may accommodate some or all of the following variables:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Electrode diameter,
Wire feed speed,
Shielding gas,
Pulse rate,
Pulse peak voltage,
Average welding current,
Background current,
Travel speed,
Arc length, and
Arc control and inductance.
The recommendations of the welding power source
manufacturer should be followed when developing
procedures for pulsed spray welding of aluminum.
Unique programs can be preset in power sources for
different filler alloys.
68
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
Table 1.36
Typical Conditions for Flat-Position Groove Welds in Aluminum
Alloys Using Large-Diameter Electrodes with Gas Metal Arc Welding
Joint Geometry
Section Thickness
Electrode
Diameter
F
Welding
Current
(DCEP),
A3
mm/s
in./min
28
450
6.8
16
Arc
Voltage,
V
Travel Speed
mm
in.
Type1
α,
Degrees
19.1
0.75
A
90
6.3
0.25
4.0
0.156
Ar
1
25.4
1.00
A
90
3.3
0.13
4.8
0.188
Ar
1, 2
26.5
500
5.1
12
31.8
1.25
A
70
4.6
0.18
4.8
0.188
Ar
1, 2
26.5
550
4.2
10
31.8
1.25
B
45
6.3
0.25
4.0
0.156
Ar
1
25
500
4.2
10
mm
in.
mm
in.
Shielding
Gas
Weld
Pass2
2
38.1
1.50
38.1
1.50
44.5
1.75
44.5
1.75
A
70
A
4.6
70
A
4.6
70
B
3.3
45
6.3
0.18
0.18
0.13
0.25
4.8
5.56
5.56
4.8
0.188
0.219
0.219
0.188
Ar
Ar
Ar
Ar
500
2
27
4.2
10
Back
26
5.1
12
1
26
550
4.2
10
3.4
8
4.2
10
2
27
575
3, 4
29
600
1
27
650
2
27.5
675
1, 2
26
650
3, 4
27
600
1, 2
28
600
4.2
10
14
3, 4
30
550
5.9
Back
30
550
4.2
10
50.8
2.00
A
70
4.6
0.2
4.8
0.188
He
1, 2, 3, 4
32
550
4.2
10
50.8
2.00
B
45
6.3
0.3
4.8
0.188
Ar
1, 2
28
600
4.2
10
76.2
3.00
76.2
3.00
A
70
C
30
4.6
12.7
0.18
0.50
5.56
5.56
0.219
0.219
3–7
26
500
5.9
14
Back
28
550
4.2
10
Ar-
1, 2
25
650
3.8
9
25%He
3, 4
23
500
4.2
10
5, 6
26
650
3.8
9
He
7–10
27
625
3.8
9
1, 2
29
650
4.2
10
3–6
31
1. The following joint types are referred to by letter in the indicated column under joint geometry:
T
α
α
α
F
T
T
F
F
R = 6.4 mm (0.250 in.)
(A)
(B)
(C)
2. All passes are welded in the flat position, odd numbers from one side and even numbers from other side with joint designs (A) and (C). Joint is back
gouged prior to depositing the back weld.
3. Constant-current dc power source and constant-speed electrode drive unit.
4. The root opening is 0 mm (0 in.) for all joints.
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
69
Table 1.37
Typical Procedures for Gas Metal Arc Fillet Welds in Aluminum
Alloys Using Large-Diameter Electrodes and Argon Shielding
Fillet Size
Electrode Diameter
Travel Speed
mm
in.
mm
in.
Weld Passa
Welding
Current, Ab
Arc Voltage,
V
12.7
0.5
4.0
0.156
1
525
mm/s
in./min
22
5.1
12
12.7
0.5
4.8
0.188
1
550
25
5.1
12
16.0
0.63
4.0
0.156
1
525
22
4.2
10
19.1
0.75
4.0
0.156
1
600
25
4.2
10
19.1
0.75
4.8
0.188
1
625
27
3.4
8
25.4
1
4.0
0.156
1
600
25
5.1
12
10
25.4
1
4.8
0.188
2,3
555
24
4.2
1
625
27
3.4
8
2,3
550
28
5.1
12
31.8
1.25
4.0
0.156
1, 2, 3
600
25
4.2
10
31.8
1.25
4.8
0.188
1
625
27
3.4
8
2,3
600
28
4.2
10
a. Welded in the flat position with one or three passes, using stringer beads.
b. Constant-current power source and constant-speed electrode wire drive unit.
Automatic Gas Metal Arc Welding
The GMAW process is readily adapted to automatic
welding. Because of the fixed welding gun angle and
nozzle-to-workpiece distance, the weld is adequately
shielded by gas, and the automatic gun travel allows for
higher welding speeds than those of manual welding.
Longitudinal or circumferential welds can be made
without intermediate stops and starts; this virtually
eliminates the crater-crack problem at weld termination. Higher current can be used with automatic welding than with the manual method (the upper range is
limited only by arc stability).
A robotic welding system, in which the welding process is controlled with equipment that moves along a
controlled path using controlled parameters, is shown
in Figure 1.29.
Welding current above 360 A is not suitable for constant-voltage power. Welding currents up to 500 A can
be used with power sources with drooping volt-ampere
characteristics and argon shielding. Considerably
higher welding current, even greater than 750 A, is
practical with helium or argon-helium mixtures. The
high current allows welds to be made in fewer weld
passes with little or no edge preparation.
Single-pass welds in butt joints are made in aluminum up to 12.7 mm (0.5 in.) in thickness without edge
preparation. Material as thick as 38 mm (1.5 in.) has
been welded with one weld pass on each side, without
edge preparation, using helium as a shielding gas. In
heavy material, it may be necessary to bevel the plate
edges in order to reduce the height of weld reinforcement.
Greater control over welding variables is made possible with automatic welding, which can join material as
thin as 0.5 mm (0.02 in.) provided that adequate fixturing is used. The higher travel speeds that can be
achieved when welding light-gauge material result in
better weld appearance, minimal distortion, and lower
welding costs. In general, automatic welding requires
fewer weld passes, lower heat input, and less edge preparation and results in reduced labor cost.
Major areas that require attention in automatic
welding are those affecting uniformity of the electrode
wire drive speed and maintenance of a constant welding
current. A high-quality electrode with uniform surface
resistance is necessary to provide uniform current. For
material thinner than 3.2 mm (0.125 in.), synergic control may be used in the conventional manner by governing the feed speed. Proper operation with either
constant-current or constant-voltage power requires
uniform and dependable electrode feeding.
The need for proper fixturing in automatic welding
cannot be overstated. Joint edges must be precisely
aligned and joint spacing maintained over the length of
the weld. This can be accomplished by the use of tack
70
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
Gas Metal Arc Spot Welding
Photograph courtesy of Miller Automation
Figure 1.29—Robotic System with
Programmed Welding Variables
welds, but some form of fixturing that will maintain the
required conditions is strongly recommended.
Adequate shielding gas coverage is vitally important;
the welding gun should be capable of providing adequate coverage at all currents and travel speeds. The
automatic welding carriage must have sufficient power
and mass to stabilize the equipment.
For vertical and lateral adjustments, the welding gun
must be rigidly mounted so that the gun angle and work
angle can be accurately set and maintained. The gun
carriage and track should be rigid enough to prevent
the transmission of vibrations to the welding head,
which would produce erratic results.
Resolution of the actual welding variables is influenced by many factors pertinent to the specific application. Fabricators should become familiar with available
data before planning an automatic welding operation.
Spot welds in lap joints in aluminum sheet can be
made with gas metal arc welding. In this process, the
arc melts through the top sheet, which should be less
than 3.2 mm (0.125 in.) thick, and penetrates into the
bottom sheet. This action produces a round nugget of
weld metal that joins the sheets, similar to the nugget
produced by resistance spot welding. The filler metal
forms a convex reinforcement on the face of the nugget.
Depth of fusion into the bottom sheet may be partial or
complete. For partial fusion, the bottom sheet should be
thicker than the top sheet.
Equipment for arc spot welding is similar to that
used for manual GMAW. A pull or push-pull drive system and an insulated shielding gas nozzle (which is in
contact with the top sheet) should be used. A push drive
system should not be used because it may produce
inconsistent results. A more consistent series of spot
welds is produced when the gun system exerts a uniform force against the top sheet during each weld.
A control unit is needed to time the duration of
welding current, electrode feed, and shielding gas flow.
Welding current and wire-feed timers should have a
range of 0 seconds (s) to 2 s and be accurate within
0.015 s.
A slow run-in electrode feed is used until arc initiation. At the termination of the weld, the welding current should flow briefly after the wire feed stops; a
predetermined length of wire is melted, thus preventing
the tip of the electrode from freezing in the weld metal.
Argon or helium, or a mixture of the two can be used
for shielding. Argon is usually used, but helium is preferred for welding thin sheet because it produces a nugget with a larger cone angle than that produced by
argon. Disadvantages of GMAW spot welding with
helium shielding are a rough weld surface and the creation of excess spatter.
Table 1.38 shows typical conditions for spot welding
lap joints in aluminum sheet with an electrode such as
ER5554 with a diameter of 1.2 mm (0.047 in.). These
welding conditions may vary somewhat with the composition of the base metal, the electrode, surface conditions, fitup, shielding gas, and equipment design.
Welding conditions for each application should be verified by appropriate destructive tests.
The depth of fusion into the back sheet depends on
arc voltage, welding current, and weld time. Increasing
any of these variables will increase penetration. Obtaining good depth of fusion with thick sheet requires high
electrode feed rates, which provide high current with
constant-voltage power sources. If a small adjustment
in depth of fusion is desired, only the wire-feed speed
(amperage) needs to be changed.
A weld time of approximately 0.5 s is usually satisfactory for making arc spot welds. A weld time less
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
71
Table 1.38
Typical Settings for Gas Metal Arc Spot Welding with
Constant-Voltage Power Sources for Various Aluminum Sheet Thicknesses
Sheet Thickness
Top
Partial Penetration Welds
Bottom
mm
Complete Penetration Welds
Electrode Feed
in.
Open-Circuit
Voltage, V
mm/s
in./min
Weld
Time, s
Open-Circuit
Voltage, V
Electrode Feed*
mm/s
in./min.
Weld
Time, s
mm
in.
0.51
0.020
0.51
0.020
—
—
—
—
27
106
250
0.3
0.51
0.020
0.76
0.030
—
—
—
—
28
127
300
0.3
0.76
0.030
0.76
0.030
25.5
120
285
0.3
28
140
330
0.3
0.76
0.030
1.27
0.050
25.5
140
330
0.3
31
182
430
0.3
0.76
0.030
1.63
0.064
30
152
360
0.3
31
190
450
0.3
0.4
1.27
0.050
1.27
0.050
31
163
385
0.4
32
190
450
1.27
0.050
1.63
0.064
32
169
400
0.4
32
212
500
0.4
1.63
0.064
1.63
0.064
32
178
420
0.4
32
233
550
0.5
1.63
0.064
3.17
0.125
32.5
275
650
0.5
34.5
286
675
0.5
1.63
0.064
4.75
0.187
35
296
700
0.5
39
296
700
0.5
1.63
0.064
6.35
0.250
39
328
775
0.5
41
338
800
0.5
3.2
0.125
3.17
0.125
39.5
338
800
0.5
41
360
850
0.6
3.2
0.125
4.75
0.187
41
360
850
0.75
41
381
900
0.75
3.2
0.125
6.35
0.250
41
381
900
1.0
—
—
—
—
*Electrode is ER5554 with a 1.2 mm (0.047 in.) diameter. The welding current in amperes is about 0.5 times the electrode feed rate in in./min.
than 0.25 s may result in non-uniform welds because
the arc starting time adds to the total weld time. Long
weld times may help to reduce porosity. Short weld
times may be best for vertical and overhead welding, or
when a flat nugget is desired. With short weld times, the
arc length must be adjusted using the open-circuit voltage setting on constant-voltage welding power sources.
Inaccurate fit-up of the workpieces can cause variations in gas metal arc spot welds. If the welds are inconsistent despite careful control of the variables, better
methods of fixturing may be needed. Solid contact of
the upper and lower workpieces is necessary for adequate heat transfer into the bottom member.
SHIELDED METAL ARC WELDING
Shielded metal arc welding (SMAW) is an arc welding process that uses an arc between a covered electrode
and the weld pool. The process is used with shielding
resulting from the decomposition of the electrode covering, without pressure, and with filler metal from the
electrode. Table 1.39 shows suggested procedures for
the shielded metal arc welding of aluminum.
This process is primarily used in small shops for
welding aluminum components to be used in noncritical applications and for repair work. It requires simple,
low-cost equipment that is readily available and portable.10 Welding travel speed is slower with SMAW than
that achieved with GMAW.
Shielded metal arc welding is not recommended for
joining aluminum for service in applications when very
high weld quality and performance are critical. One of
the gas-shielded arc welding processes should be used
for these applications.
The aluminum electrode covering contains an active
flux that combines with aluminum oxide to form a slag.
This slag becomes a potential source of corrosion and
must be completely removed after each weld pass. The
covering on aluminum electrodes is prone to deterioration over time and with exposure to moisture, so the
electrodes must be stored in a dry atmosphere. Otherwise,
10. Refer to Chapter 2 of American Welding Society (AWS) Welding
Handbook Committee, 2004, Welding Processes, Part 1, ed. A.
O’Brien, vol. 2, Welding Handbook, 9th ed., Miami: American Welding
Society. See Appendix B of this volume for a detailed description of
chapter contents for all five volumes of Welding Handbook, 9th ed.
72
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
Table 1.39
Suggested Procedures for Shielded Metal Arc Welding of Aluminum
Filler Metal Consumption
Thickness
Electrode or
Filler Diameter
Butt
Lap and
Fillet kg/100 m
Lap
lb/100 ft
kg/100 m
Fillet
in.
2.0
0.081
3.23
0.13
60
1
1
0.70
4.7
0.79
5.3
0.93
6.3
2.6
0.102
3.2
0.13
70
1
1
0.74
5.0
0.85
5.7
0.93
6.3
3.2
0.125
3.2
0.13
80
1
1
0.85
5.7
0.93
6.3
0.93
6.3
4.0
0.156
3.2
0.13
100
1
1
0.93
6.3
0.97
6.5
0.97
6.5
4.8
0.188
4.0
0.16
125
1
1
1.3
8.7
1.34
9.0
1.34
9.0
6.4
0.250
4.8
0.19
160
1
1
1.8
12
1.8
12
1.8
2
9.5
0.375
4.8a
0.19a
200
2
3
3.7
25
4.3
29
4.3
29
6.4b
0.25b
4.8a
0.19a
300
3
3
5.2
35
5.2
35
5.2
35
6.4b
0.25b
0.50
in.
Butt
mm
12.7
mm
Approximate
DCEP
Current,
A
No. of
Weld Passes
lb/100 ft
kg/100 m
lb/100 ft
25.4
1.00
7.9
0.31
450
3
3
19.3
130
22.3
150
22.3
150
50.8
2.00
7.9–9.5
0.31–0.38
550
8
8
60
400
67
450
67
450
a. For lap joints and fillet joints.
b. For butt joints.
before use, they should be oven-dried according to recommendations from the manufacturer. This typically
entails drying in an oven at 65°C to 95°C (149°F to
203°F). Welding is done with DCEP. Important factors
to consider when welding aluminum with SMAW are
the following:
1.
2.
3.
4.
Moisture content of the electrode covering,
Cleanliness of the electrode and base metal,
Preheating of the base metal, and
Complete slag removal between passes and after
welding.
Single-pass welds should be used if possible. If multiple-pass welds are needed, thorough removal of slag
between passes is essential for optimum results. After
the completion of the weld, the bead and workpiece
should be thoroughly cleaned to remove all traces of
slag. Most of the slag can be removed by mechanical
means, using a rotary wire brush, needle gun, or a slag
hammer. Residual traces can be removed by steam
cleaning or by applying a hot-water rinse. To test for
complete slag removal, the weld area can be swabbed
with a solution of 5% silver nitrate; foaming will occur
if slag is present. Any remaining slag can be removed by
soaking the weld in a hot 5% nitric acid or warm 10%
sulfuric acid solution for a short time, followed by a
thorough rinse in hot water.
PLASMA ARC WELDING
Plasma arc welding (PAW) employs a constricted arc
between a nonconsumable electrode and the weld pool
(transferred arc) or between the electrode and the constricting nozzle (nontransferred arc). Shielding is
obtained from the ionized gas issuing from the watercooled torch, which may be supplemented by an auxiliary source of shielding gas.
Plasma arc welding is similar to GTAW, but uses a
different mechanism to deliver the heat for welding.11
The constricting nozzle of the torch increases the energy
density, directional stability, and focusing effect of the
plasma arc.
The two techniques used for plasma arc welding are
the melt-in and keyhole methods. The melt-in technique
11. Refer to Chapter 7 of American Welding Society (AWS) Welding
Handbook Committee, 2004, Welding Processes, Part 1, ed. A.
O’Brien, vol. 2, Welding Handbook, 9th ed., Miami: American Welding
Society. See Appendix B of this volume for a detailed description of
chapter contents for the five volumes of the Welding Handbook,
9th ed.
AWS WELDING HANDBOOK
is similar to that of GTAW. The keyhole technique
involves establishing the weld pool, then gradually
increasing the orifice gas flow rate, which displaces the
molten metal and forms a small hole, which fully penetrates the base metal. As the plasma arc torch moves
along the weld joint, metal flows from the leading edge
of the keyhole around the plasma stream and to the
back, where the weld progressively solidifies. This technique is typically used when welding relatively thick
sections.
Direct current electrode negative (DCEN) is usually
used for plasma arc welding of aluminum. Like GTAW
when used with DCEN, there is no arc cleaning action.
Surface cleaning prior to welding is necessary. Conventional or square wave ac or direct current electrode positive (DCEP) also can be used to take advantage of arc
cleaning. Power sources for PAW are similar to those
used for GTAW.
Deeper joint penetration and faster welding speeds
are advantages of PAW over GTAW. Using the melt-in
technique, these conditions tend to increase the presence of porosity in aluminum welds because gases have
less time to escape to the surface of the weld pool.
Porosity can be minimized by preweld cleaning of the
base metal, using a clean filler wire, and providing adequate inert gas shielding of the weld. The oxides at the
abutting edges are dispersed, however, and porosityfree welds are produced using the keyhole technique
with a sophisticated variable polarity system. Inert gas
shielding is recommended on both sides of the weld
with this method, especially with alloys in the 5XXX
series and aluminum-lithium alloys.
Crater Filling, Arc Welding
Aluminum alloy weld metal has a tendency to form
crater cracks when arc welding is stopped abruptly.
This problem can be remedied if the proper technique is
used to fill the crater.
With manual welding, the forward travel should be
stopped and the arc extinguished and reignited rapidly
several times, filling the crater as it solidifies. When
using GTAW or PAW with remote current control, the
welding current should be decreased gradually while
adding filler metal until the weld pool solidifies. If
remote current control is not used, the direction of
travel should be reversed as the welding torch speed is
accelerated. This will substantially reduce the size of the
weld pool prior to breaking the arc. This is often
referred to as “tailing out” the weld.
To tail out the weld when using semiautomatic
GMAW, arc travel should be reversed and accelerated
over a short length before the arc is broken. With automatic welding, the wire-feed speed, the welding current,
and the arc voltage (and the orifice gas with PAW)
should be programmed to fill the crater when travel
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
73
stops. These variables are gradually decreased as the
crater fills. Removable aluminum run-off tabs can be
used to terminate the welds with any of the processes.
When weld tabs are not practical, as with welding of
pipe or when the arc must be terminated within the
weld joint, it is necessary to remove the weld crater by
mechanical means prior to restarting the weld.
ARC STUD WELDING
Arc stud welding (SW) is an arc welding process
using an arc between a metal stud, or similar part, and
the workpiece. The process is used without filler metal;
with or without shielding gas or flux; with or without
partial shielding from a ceramic or graphite ferrule surrounding the stud; and with the application of pressure
after the faying surfaces are sufficiently heated. The
three commonly used methods for the arc stud welding
of aluminum are drawn arc with ferrule, short-cycle gas
arc, and initial gap capacitor discharge (CD). The discussion of stud welding in this chapter is limited to the
requirements specific to aluminum alloys.12
When welding aluminum studs, a maximum ratio of
plate thickness to stud diameter of 1 to 2 is recommended for the drawn arc method.
Capacitor Discharge Stud Welding of
Aluminum
The capacitor-discharge stud welding method is recommended for welding fasteners onto thin aluminum
sheets because heat input is significantly less than the
drawn arc methods. A maximum ratio of plate thickness to stud diameter of 1 to 4 is recommended for the
capacitor discharge method.
The equipment for capacitor-discharge stud welding
consists of a stud welding gun and a power unit with
associated interconnecting cables. Welding is typically
accomplished without shielding gases or ferrules.
Most capacitor-discharge units operate on ac power
(e.g., 120 V, single phase). A charge circuit is used
to charge a bank of capacitors. This stored energy is
discharged through a silicon-controlled rectifier to provide the arc energy for melting the stud and the base
material.
There are two different capacitor discharge methods:
initial gap and initial contact. Ferrules are not used due
to the short welding time of a few milliseconds. Capacitor discharge welding requires the use of studs that have
a timing tip (projection) on the face of the stud (i.e., the
12. Refer to Chapter 9 of American Welding Society (AWS) Welding
Handbook Committee, 2004, Welding Processes—Part 1, Volume 2
of the Welding Handbook, 9th ed., Miami: American Welding Society.
74
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
end of the stud to be welded), which serves as a fuse
that melts to create the arc. The arc time is controlled
by the projection diameter and the spring pressure of
the gun. For the initial-gap technique, arc time is controlled by the initial-gap distance. The arc current is
controlled by the capacitor voltage, capacitance and
weld cable impedance (mostly inductance). The gap can
be created manually (manual gap) or by a solenoid
(auto gap).
Initial Gap Capacitor Discharge Stud Welding.
Of the capacitor-discharge methods, the initial-gap
method has the shortest arc time, making it superior for
welding aluminum. The welding sequence is shown in
Figure 1.30; refer to notes (A) through (F). The timing
tip is triggered to initiate the arc. Because the stud is
already moving downward before contact and arc ignition, total arc time is very short. The length of the weld
cable should be short in order to keep circuit inductance to a minimum. Two ground cables and clamps at
opposite ends of the workpiece are recommended for
uniform current distribution, which will help avoid arc
blow that might cause expulsion of molten metal
toward one side only and reduce the strength of the
welded joint. Due to the high amperage, the ground
path for the current is critical and the ground area must
be thoroughly cleaned. Spring tension and cleanliness of
the chuck must be maintained to prevent arcing
between the stud and the chuck.
ure 1.30). Instead, the stud is pressed against the workpiece prior to discharging the capacitors. Because high
spring pressure is needed to shorten the arc time for aluminum, and the aluminum timing tip may be too soft to
withstand such high pressure, initial contact CD can
result in deformed timing tips, inconsistent arc time and
inconsistent weld quality. Thus, initial contact CD is
not recommended for aluminum stud welding in production environments.
Portable equipment for capacitor-discharge initial
gap stud welding is shown in Figure 1.31. Dual grounding clamps at opposite ends of the workpiece are recommended to minimize arc blow. Voltage, gap, and
pressure are the three key parameters in process control. Commonly used aluminum studs are shown in Figure 1.32.
Drawn Arc Stud Welding of Aluminum
The drawn arc stud welding method is recommended
for welding large-diameter aluminum studs because this
method produces welds of higher quality and better
process tolerance. The two commonly used drawn arc
stud welding processes are drawn arc with gas and ferrule and short-cycle gas arc without ferrule. The CD
process for stud welding cannot provide melting over
the entire surface of the large diameter stud; better
quality is achieved with drawn arc stud welding.
Initial Contact Capacitor-Discharge Stud Welding. Unlike initial gap CD welding, initial contact CD
stud welding does not start with Step (A) (refer to Fig
(A)
(A)
(B)
(C)
(D)
(E)
(F)
(B)
(C)
(D)
(E)
(F)
Stud is positioned, leaving an arc-length space.
Stud is released and voltage is applied.
Stud contacts the workpiece and initiates an arc.
The stud end and workpiece melt.
Stud plunges into workpiece.
Weld is complete.
Figure 1.30—Sequence of
Capacitor-Discharge Stud Welding
Figure 1.31—Portable Equipment for Initial Gap
or Initial Contact Capacitor-Discharge
Stud Welding of Aluminum
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
75
Drawn Arc Stud Welding Method. For drawn arc
stud welding of aluminum, an inert shielding gas is used
with a ceramic ferrule, and the gun is equipped with a
controlled plunge-dampening device. A ferrule holder
with a special gas-adaptor foot is used to contain the
high-purity inert shielding gas during the weld cycle.
Argon shielding is usually used, but helium may be useful with large studs because helium has the potential for
a hotter arc at higher ionization levels. Direct current
electrode positive (DCEP) is usually used to weld studs
on thick plate material because it provides cathodic
cleaning of surface oxide. The stud functions as the
electrode.
A typical equipment combination for manual welding includes a power source and a spring-coil hand gun
outfitted with gas foot and a plunge dampener, as
shown in Figure 1.33. Key welding parameters are arc
current, arc time, lift height and plunge depth. When
using the drawn arc method for aluminum welding, a
faster plunge rate or longer free travel is recommended
to avoid cold plunge—a defect caused by the solidification of the weld pool prior to plunging of the stud into
the pool. Aluminum is more susceptible to cold plunge
due to its high thermal conductivity. A motorized hand
gun can also be used to achieve fast free travel, first to
bridge the arc gap and then slowly ease the stud into the
weld pool to minimize spatter.
Drawn-arc stud welding equipment is available with
gas timers controlled by the power unit that require less
operator skill, and a self-actuating gas foot control with
an integral valve that lowers gas consumption.
A drawn arc aluminum stud differs from a steel stud
in that no flux is used on the stud weld tip. A cylindrical
or cone-shaped aluminum projection is used on the base
of the aluminum stud, as illustrated by the stud designs
shown in Figure 1.34. The projection serves to initiate the
long arc used for aluminum stud welding. Figure 1.35
Figure 1.32—An Assortment of Stud Designs
for Capacitor-Discharge Stud Welding
Figure 1.34—Commonly Used Aluminum
Studs for Drawn Arc Stud Welding
Figure 1.33—Basic Equipment Setup for
Drawn Arc Stud Welding of Aluminum
76
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
BASE-METAL
TIP PROJECTION
Figure 1.35—Full-Diameter Weld Base
Aluminum Stud with Compound Angle
Weld End for Drawn Arc Stud Welding
shows a typical fastener and weld-end projection for
drawn arc stud welding. Aluminum studs for shortcycle gas arc welding may not have the projection.
Examples are tapped studs used to manufacture items
such as aluminum utensils and aluminum insulation
pins, and European-produced aluminum studs.
Aluminum studs for the drawn arc method range in
weld-base diameters from 5 mm to 13 mm (0.188 in. to
AWS WELDING HANDBOOK
0.500 in.). The stud-base diameter welded by the capacitor-discharge process is 2 mm to 8 mm (0.062 in. to
0.312 in.), although 9.5 mm (0.3758 in.) may be
welded under carefully limited circumstances.
Drawn arc stud welding of aluminum is more challenging than welding steel with this method, because
aluminum has a lower melting temperature, higher
thermal conductivity, and the tendency to rapidly form
surface oxides. Weld contamination, incomplete fusion,
melt through, arc blow, undercut, and distortion are
commonly encountered problems. Computer-controlled
inverters have pulsing capabilities and independent control of the current during the plunging action. These
machines are capable of producing good quality welds
under adverse conditions. A pulse waveform, illustrated
in Figure 1.36, reduces overall heat input to minimize
distortion and melt-through. High peak-current pulses
are used to increase cathodic cleaning action, which
removes refractory oxides and increases arc stiffness.
Low background current is used to lower heat input.
Aluminum conducts heat very rapidly and cools rapidly
during the plunge as the arc voltage drops. Insufficient
heat input makes the weld prone to cold plunge. Higher
current during the plunging action alleviates cold
plunge and forms a robust, full-bodied flash ring (donut
shaped), with good wetting in both the flat and vertical
positions, as shown in Figure 1.37.
Short-Cycle Arc Stud Welding. Aluminum studs
can also be welded without ferrules in short-cycle arc
stud welding. Because inert shielding gas must be used
for aluminum, this process is also called gas arc stud
welding. The short-cycle welding sequence is shown in
Figure 1.38 and the basic equipment setup for automated short-cycle stud welding of aluminum is shown in
Figure 1.39. The key parameters are the same as those
Figure 1.36—Pulse Waveform for Drawn Arc Stud Welding of Aluminum
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
Figure 1.37—Properly Formed Flash around the
Base of a Pulse-Waveform Weld with 12.7 mm
(0.5 in.) Internally Threaded Aluminum Stud
77
for drawn arc welding with a ferrule, except for shorter
arc time (typically less than 50 ms for aluminum).
In addition to the hand gun outfitted with a plunge
dampener or other welding tools, such as a motorized
hand gun with position and speed control or a servoelectric weld head with encoder feedback and gas diffuser front end held by a robot arm may be used. During automated welding, the studs are sorted and fed
from the feeder to the weld head pneumatically. The
servo-electric weld head for automated aluminum stud
welding is typically used in automotive production. Figure
1.40 shows the stud shapes for short-cycle stud welding.
Direct current electrode positive (DCEP) welding
cleans surface oxide, but it also introduces more heat to
the workpiece than DCEN. This may cause meltthrough when welding to thin aluminum sheets. Alternating current (ac) drawn arc stud welding technology
has the potential to clean surfaces while minimizing
heat input, which is good for welding fasteners on very
thin gauge aluminum sheet metal.
Source: Nelson Stud Welding.
Figure 1.38—Short-Cycle Stud Welding Sequence
78
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
Source: Nelson Stud Welding.
Figure 1.39—Basic Equipment Setup for Automated Short-Cycle Stud Welding of Aluminum
Figure 1.40—Aluminum Stud Shapes
for Short-Cycle Stud Welding
Short-cycle stud welding provides several advantages
when used to join aluminum alloys because this method
minimizes over-aging and softening of the adjacent base
metal; however, metallurgical compatibility between the
stud material and the base metal must be considered.
A comparison of the three aluminum stud welding
processes is provided in Table 1.40. Small studs can be
welded to thin sections with the capacitor-discharge
method. Studs have been welded to sheet as thin as
0.5 mm (0.020 in.) without melt-through. Because the
penetration of the weld pool is very shallow, capacitordischarge welds can be made without damage to aluminum with a prefinished opposite side. No subsequent
cleaning or finishing is required.
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
Table 1.40
Comparison of Three Commonly Used Methods for the Stud Welding of Aluminum
Largest stud diameter
Initial Gap
Capacitor Discharge
Gas Arc
Without Ferrule
Drawn Arc with
Gas and Ferrule
7.9 mm (0.31 in.)
9.52 mm (0.375 in.)
12.7 mm (0.5 in.)
No
Yes
Yes
Gas shielding
Ferrule used
No
No
Yes
Tipped
7° angle or spherical
Compound angle
Coil and tip
Coil
Coil
1.02 mm (0.040 in.)
2.03 mm (0.080 in.)
3.175 mm (0.125 in.)
14 000 A, peak
800 A
275 A
Stud weld end shape
Arc length source
Min. base metal thickness for 7.9 mm (0.312 in.)
Weld current for 7.9 mm (0.312 in.)
Weld time for 7.9 mm (0.312 in.)
Stud length reduction 7.9 mm (0.312 in.)
Tolerance for surface contamination or roughness
Distortion and heat effect
1 ms–4 ms
100 ms
450 ms
0.38 mm (0.015 in.)
1.27 mm (0.050 in.)
3.175 mm (0.125 in.)
Very poor
Fair
Good
Minimal
Slight
Significant
Yes
No
Yes
MIL-Spec qualified (MIL-S-24149)
Capacitor-discharge power facilitates the welding of
dissimilar aluminum alloys. Studs larger than 8 mm
(0.3 in.) in diameter must be welded with a drawn arc
welding method. Drawn arc with ferrules is commonly
used in shipyard and industrial applications. Short-cycle
stud welding without ferrules is commonly used in
automotive applications. Drawn arc stud welding is a
closed-loop, current-controlled method, so it is more
tolerant of impediments such as surface oxide on the
aluminum base-metal, wax and dry lubrication residue,
oil, surface texture, stud dimensional variations, weld
cable inductance, chuck electrical erosion, and gripping
force than capacitor discharge methods.
Table 1.41
Weldability (Arc Stud Welding) of
Aluminum Alloy Base Plate Material
Base Plate
Alloy Series
Weldability
Strength
1XXX
Excellent
High
2XXX
Poor
Low
3XXX
Excellent
High
4XXX
Good
Low
5XXX
Excellent
High
6XXX
Good
High
7XXX
Poor
Low
Base Metal and Stud Alloys
Base metal alloys of Series 1XXX, 3XXX, and
5XXX and also Alloy 2219 are considered excellent for
stud welding. The Series 4XXX and 6XXX alloys are
considered fair; Series 2XXX and 7XXX alloys are generally poor. Table 1.41 and Table 1.42 summarize the
weldability of aluminum base metal and stud materials.
Table 1.43 shows the comparative weldability of several
combinations of base aluminum alloys and stud materials used in applications and notes some base alloys with
good weldability.
Aluminum studs are commonly made of aluminummagnesium alloys, including Alloys 5083, 5086, 5183,
5356, and 5556, which have a typical tensile strength of
approximately 275 MPa (40 ksi). These alloys have
Table 1.42
Weldability (Arc Stud Welding) of
Aluminum Alloys Used as Stud Material
Stud Alloy
Weldability
Strength
1100
Fair
Low
2319
Excellent
High
5356
Excellent
High
5183
Excellent
High
5556
Excellent
High
4043
Excellent
Medium
79
80
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
Table 1.43
Aluminum Stud Alloys Commonly Used
with Selected Aluminum Base Alloys
Base Alloys
Stud Alloy
1XXX
1100
2219a
2319
3XXX
1100, 4043
4XXX
4043
5XXX
5356, 5183, 5556, 5456, 5083, and 5086
6XXX
4043, 5XXX
7XXXb
5XXX type
a. Good weldability.
b. Good weldability (7004, 7005, 7039).
high strength and good ductility. They are compatible
with most aluminum alloys used in fabrication.
A typical arc stud weld in aluminum is shown in the
macrograph in Figure 1.41, illustrating that molten
weld metal is pushed to the perimeter of the stud to
form flash. The amount of weld metal (cast structure)
in the joint is minimal. The length of aluminum arcwelded studs is typically reduced by 3 mm (0.12 in.)
during welding. For studs welded with any of the
capacitor-discharge methods, the volume of metal that
is melted is almost negligible. For example, the length
of aluminum capacitor-discharge studs is reduced
between 0.20 mm to 0.38 mm (0.008 in. to 0.015 in.).
The heat-affected zone common to arc welding is
present, but it is small because of the short welding
time.13
Typical welding time, current settings, and shielding
gas flow rates for arc stud welded aluminum fasteners
are shown in Table 1.44. For the capacitor discharge
method, flanged studs are preferred, when possible, for
two reasons. First, the flanged studs are more reliable
because the welded area is larger than the cross sectional area through the threads. The increased area
compensates for the softening effect caused by the heating and cooling cycle and ensures the full strength of the
finished assembly. Second, flanged studs are usually less
expensive, because the larger flanges aid in producing
the timing tips; otherwise a secondary operation is
needed to remove or modify the flanges.
Part of the molten material derived from the length
reduction of arc stud welds appears as the weld metal
13. Refer to Chapter 4 of American Welding Society (AWS) Welding
Handbook Committee, 2001, Welding Science and Technology, ed.
C. Jenney and A. O’Brien, vol. 1, Welding Handbook, 9th ed.,
Miami: American Welding Society.
Figure 1.41—Macrostructure of a 9.5 mm (0.375 in.)
Diameter Aluminum Alloy 5356 Stud Welded
to a 6.4 mm (0.250 in.) Alloy 5053 Plate
or flash that forms around the stud base. This type of
flash should not be confused with a conventional fillet
weld because it is formed in a different manner. When
properly formed and contained, the flash indicates complete penetration and complete fusion over the full cross
section of the stud base. In drawn arc stud welding, the
dimensions of the flash are controlled by the design of
the ferrule. The diameter of the flash increases the effective diameter of the stud, and this must be considered
when designing integrating or matching components.
Figure 1.42 shows methods for accommodating the
stud flash. Table 1.45 shows the clearance for round
studs. The size of the flash varies with the size and thickness of the stud material and ferrule clearance. Test
welds should be made to confirm the necessary clearances. The stud-weld flash may not be fused along the
vertical and horizontal legs of the weld, but, because
flash is not considered part of the weld, this incomplete
fusion is not considered detrimental to joint quality.
The capabilities of drawn arc stud welding and
capacitor-discharge methods overlap in some applications, but well-defined procedures for selecting the
appropriate methods have been established. The criteria
used in selection should be fastener size, base-metal
thickness, and minimization of reverse-side marking.
The more difficult choice may be selecting the capacitor-discharge technique that should be used, e.g., initial
gap, or initial contact. A selection chart is shown in
Table 1.46.
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
Table 1.44
Typical Conditions for Arc Stud Welding of Aluminum Alloys
Stud Weld Base Diameter
mm
in.
Weld Time,
Seconds
6.4
7.9
9.5
11.1
12.7
0.250
0.312
0.375
0.438
0.500
0.33
0.50
0.67
0.83
0.92
Shielding Gas Flowb
Welding Current,
Aa
L/min
ft3/h
250
325
400
430
475
7.1
7.1
9.4
9.4
9.4
15
15
20
20
20
a. The currents shown are actual welding current and do not necessarily correspond to power source dial settings.
b. Shielding gas—argon.
(A)
(C)
(B)
Figure 1.42—Methods of Accommodating Flash (A) Oversized Hole, (B) Spacer, and (C) Cavity
Table 1.45
Weld Fillet Clearances for Aluminum Arc Stud Welds
Counterbore
Countersink
B*
A*
Stud Base Diameter
C*
mm
in.
mm
in.
mm
in.
mm
in.
4.8
6.4
7.9
9.5
11.1
12.7
0.188
0.250
0.312
0.375
0.438
0.500
9.9
11.9
13.5
16.7
19.1
21.4
0.390
0.469
0.531
0.656
0.750
0.844
4.0
4.0
4.7
5.6
6.4
7.1
0.156
0.136
0.187
0.218
0.250
0.281
4.0
4.0
4.7
4.7
6.4
6.4
0.156
0.156
0.187
0.187
0.250
0.250
*A, B, and C dimensions are measured as shown in these diagrams:
B
A
C
45°
81
82
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
Preparation of Base Metal for Stud Welding
Cleaning the base metal to ensure good welding
results may be necessary. Mill-finish aluminum usually
does not require cleaning but should be free of dirt, oil,
paint, and similar contaminants. Polished aluminum is
usually clean enough to weld; etching to remove the
aluminum oxide film is usually unnecessary. Heavy
coatings of aluminum oxide should be removed by
brushing with a stainless-steel wire brush prior to welding. Pulsed cleaning and pulsed welding with an
inverter power source will make the process more tolerant of surface oxide and contamination.
Anodizing aluminum creates a high surface resistance and should not be performed until after the studs
have been welded; the studs also benefit from anodiz-
Table 1.46
Aluminum Stud Welding Process Selection Chart1
Capacitor-Discharge Stud Welding
Factors to be Considered
Arc Stud Welding
Initial Gap
Initial Contact
Drawn Arc
A
A
A
C
D
B
B
B
C
D
A
A
B
C
D
A
A
A
A
A
A
B
A
B
B
B
B
B
A
B
B
B
B
A
C
A
B
A
A
C
B
D
B
C
B
B
D
B
C
B
B
B
B
D
A
A
A
A
B
A
A
A
B
A
A
A
A
A
A
A
B
A
B
B
A
A
A
A
Stud Diameter
1.6 mm to 3.2 mm (0.062 to 0.125)
3.2 mm to 6.4 mm (0.125 to 0.250)
6.4 mm to 7.9 mm (0.250 to 0.312)
7.9 mm to 9.5 mm (0.312 to 0.375)
9.5 mm to 12.7 mm (0.375 to 0.500)
D
C
A
A
A
1100
4043
5183
5356
5556
6061
D
A
B
B
B
B
Stud Material
Base Material
1000 Series
2000 Series2
3000 Series
4000 Series
5000 Series
6000 Series
7000 Series3
B
D
B
C
B
B
D
Base Metal Thickness
Under 0.4 mm (0.015 in.)
0.4 mm to 1.6 mm (0.015 in. to 0.062 in.)
1.6 mm to 3.2 mm (0.062 in. to 0.125 in.)
Over 3.2 mm (0.125 in.)
D
C
B
A
Heat effect on exposed surfaces
Weld fillet clearance
Strength of stud governs
Strength of base metal governs
B
B
A
A
Strength Criteria
1. Applicability of factors in chart are coded as follows:
A—Applicable without special procedures, equipment, etc.
B—Applicable with special techniques or on specific applications which justify preliminary trials or testing to develop welding procedure and technique.
C—Limited application.
D—Not recommended.
2. 2219 is easily welded with 2319 stud.
3. 7004, 7005, and 7039 are very weldable.
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
ing. When anodizing cannot be avoided prior to welding, the base metal surface must be milled at the
location where the studs are to be welded. Milling may
reduce the sheet thickness of anodized aluminum sheet
to the point that reverse-side marking or melt-through
may occur. This can be prevented by using a smaller
stud or heavier-gauge aluminum sheet. In addition to
milling the anodized surface for good stud-to-basemetal contact, it is necessary to provide a low-resistance
path for the weld current to the workpiece connector.
Strength of Aluminum Studs
The average tensile strength of the aluminum alloys
commonly used for drawn arc stud welding is 290 MPa
(42 ksi) with an average yield strength of 207 MPa
(30 ksi). Table 1.47 shows the weld strength that can be
expected for various diameters of threaded studs. The
torque figures are based on a torque coefficient factor
of 0.20. For a particular application, ultimate torque
and tensile strength of the studs should be established
and acceptable proof load ranges should be specified.
For design purposes, the smallest cross-sectional area
of the stud should be used for load determination. Adequate safety factors must be considered in the design.
83
To develop full stud strength when using drawn arc
stud welding, the aluminum plate (base metal) thickness
should be a minimum of half the weld-base diameter
of the stud. As shown in Table 1.48, a minimum
plate thickness is required for each stud size to permit
drawn arc stud welding without melt-through or excessive distortion.
Typical strengths of aluminum capacitor-discharge
welded studs are shown in Table 1.49.
Quality Control and Inspection
Code requirements for qualifying, testing, and
inspecting aluminum studs welded by capacitor-discharge stud welding methods are outlined in Structural
Welding Code—Aluminum (AWS D1.2).14 Qualification procedures are included. Failed studs can be
repaired or replaced in accordance with AWS D1.2 code
requirements.
14. American Welding Society (AWS) Committee on Structural
Welding, 2008, Structural Welding Code—Aluminum, D1.2/
D1.2M:2014, Miami: American Welding Society.
Table 1.47
Typical Strengths of Aluminum Arc-Welded Studsa
METAb
Stud Thread
Diameter
mm2
in.2
Yield
Tensile Loadc
kg
lb
Yield
Torque Loadc
N·m
in.·lb
Ultimate
Tensile Load
kg
lb
Ultimate
Torque Load
N·m
in.·lb
Ultimate
Shear Loadd
kg
lb
10-24 UNC
11.0
0.017
231
510
2
19
324
714
3
27
194
428
10-32 UNF
12.9
0.020
272
600
2.5
22
381
840
4
32
229
504
1/4-20 UNC
19.4
0.032
435
960
5
48
610
1344
7.6
67
366
806
1/4-28 UNF
23.2
0.036
490
1080
6
54
686
1512
8.6
76
411
907
5/16-18 UNC
33.5
0.052
708
1560
11
97
991
2184
136
594
1310
15
5/16-24 UNF
37.4
0.058
789
1740
12
108
1105
2436
17
152
663
1462
3/8-16 UNC
50.3
0.078
1061
2340
20
175
1486
3276
28
246
892
1966
3/8-24 UNF
56.8
0.088
1197
2640
22
198
1676
3696
31
277
1005
2217
7/16-14 UNC
68.4
0.106
1442
3180
31
278
2019
4452
44
389
1211
2671
7/16-20 UNF
76.1
0.118
1606
3540
35
310
2248
4956
49
434
1349
2973
1/2-13 UNC
91.6
0.142
1932
4260
48
426
2705
5964
67
596
1623
3578
1/2-20 UNF
103.2
0.160
2177
4800
54
480
3048
720
76
672
1829
4032
a. Mechanical properties are based on 290 MPa (42 ksi) ultimate strength and 207 MPa (30 ksi) yield strength.
b. Mean effective thread area (META) is based on a mean diameter between the minor and pitch diameters, providing a closer correlation with actual yield and
tensile strengths.
c. Typically, studs should be used at no more than 60% of the yield load figures.
d. Ultimate shear load is calculated at 60% of the ultimate tensile load.
84
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
Table 1.48
Recommended Minimum Aluminum Plate Thicknesses for Drawn Arc Stud Welding
Aluminum
Stud Base Diameter
With Backup*
Without Backup
mm
in.
mm
in.
mm
in.
4.8
0.19
3.3
0.13
3.3
0.13
6.4
0.25
3.3
0.13
3.3
0.13
7.9
0.31
4.8
0.19
3.3
0.13
9.5
0.38
4.8
0.19
4.8
0.19
11.1
0.44
6.4
0.25
4.8
0.19
12.7
0.50
6.4
0.25
6.4
0.25
*A metal backup to prevent melt-through of the plate.
Table 1.49
Typical Strengths of Aluminum Capacitor-Discharge Welded Studs
METAa
Stud Thread
Diameter
mm2
in.2
Yield
Tensile Loadb
Yield
Torque Loadb
Ultimate
Tensile Load
kg
N·m
kg
lb
in.·lb
lb
Ultimate
Torque Load
N·m
in.·lb
Ultimate
Shear Loadc
kg
lb
Aluminum Alloy 1100d
4-40
3.9
0.006
54
120
0.3
2.7
57
126
0.3
2.8
34
76
6-32
5.8
0.009
82
180
0.6
5
86
189
0.6
5.2
52
113
8-32
9.0
0.014
127
280
1.0
9
133
294
1.1
9.6
80
176
10-24
11.0
0.017
154
340
1.5
13
170
375
1.6
14
102
225
10-32
12.9
0.020
181
400
1.7
15
191
420
1.8
16
115
252
1/4-20
19.4
0.032
290
640
3.6
32
305
672
3.8
34
183
403
1/4-28
23.2
0.036
327
720
4
37
343
756
4.3
38
206
454
5/16-18
33.5
0.052
472
1040
7
65
495
1092
7.7
68
297
655
5/16-24
37.4
0.058
526
1160
8
73
552
1218
8.6
76
331
731
68
151
Aluminum Alloys 5183, 5356,
4-40
3.8
0.006
82
180
0.5
6061e
4
114
252
0.6
5.6
6-32
5.8
0.009
122
270
0.8
7.4
171
378
1.1
10
103
227
8-32
9.0
0.014
191
420
1.6
13.7
267
588
2.1
19
160
353
10-24
11.0
0.017
231
510
2
19
324
714
3
27
194
428
10-32
12.9
0.020
272
600
3
22
381
840
4
32
229
504
1/4-20
19.4
0.032
435
960
5
48
610
1344
7
67
366
806
1/4-28
23.2
0.036
490
1080
6
54
686
1512
8
76
411
907
5/16-18
33.5
0.052
708
1560
11
97
991
2184
15
136
594
1310
5/16-20
37.4
0.058
789
1740
12
108
1105
2436
17
152
663
1462
a. Mean effective thread area (META) is based on a mean diameter between the minor and pitch diameters, providing a closer correlation with actual yield and
tensile strengths.
b. Typically, studs should be used at no more than 60% of the yield load figures.
c. Ultimate shear load is calculated at 60% of the ultimate tensile load.
d. Mechanical properties of 1100 alloy are based on 145 MPa (21 ksi) ultimate strength and 138 MPa (20 ksi) yield strength.
e. Mechanical properties of 5183, 5356, and 6061 alloys are based on 290 MPa (42 ksi) ultimate strength and 207 MPa (30 ksi) yield strength.
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
The appearance of aluminum studs welded with the
drawn arc method is radically different from that of
studs welded with capacitor-discharge methods. The
amount of metal melted during drawn arc welding is
greater than that melted during capacitor-discharge
welding; this weld metal is usually formed into a flash
ring around the periphery of the stud base, making
visual inspection easier. The flash ring is not load bearing and should not be considered a fillet weld, as it
would be in other arc welding processes.
Figure 1.43(A) illustrates the visual appearance of a
typical satisfactory flash structure for aluminum arc
stud welds. Examples of unsatisfactory flash structures
are shown in Figure 1.43(B) through (F).
The weld flash around the stud base is inspected
for consistency and uniformity. Incomplete flash may
85
indicate a faulty weld. To pass visual inspection, the
studs should have a well-formed and fully wetted
circumferential flash over at least 75% of the periphery.
In contrast to drawn arc stud welding, capacitor-discharge welded studs do not exhibit a flash of sufficient
formation to visually determine deficiencies. There
should be some flash and full wetting at the weld joint.
Figure 1.44 is a macrograph of expelled weld metal
from a capacitor-discharge weld showing the low-profile flash and wetting of the stud periphery.
It is more difficult to visually inspect the weld flash
of a capacitor-discharge stud weld than that of a stud
weld produced by the drawn arc welding method. Figure
1.45(A) shows an example of a satisfactory capacitordischarge welded aluminum stud; Figure 1.45(B) and
(A)
(B)
(C)
(D)
(E)
(F)
(A) Satisfactory stud weld with 360° flash formation.
(B) Incomplete flash for 360°.
(C) Very little or no flash.
(D) Incomplete flash for 360°.
(E) No flash.
(F) Excessive flash.
Figure 1.43—Visual Appearance of (A) Satisfactory and
(B–F) Unsatisfactory Arc Stud Welded Aluminum Studs
86
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
(A) Good Weld
Figure 1.44—Macrostructure of 9.5 mm (0.375 in.)
Diameter 6061-T6 Aluminum Stud Welded to
3.2 mm (0.125 in.) Aluminum Sheet of the
Same Alloy (Magnified 10X), Using the
Capacitor-Discharge Method
Figure 1.45(C) show unsatisfactory welds and typical
causes.
(B) Weld Power Too High
HIGH ENERGY BEAM
WELDING PROCESSES
The high-energy beam welding processes used for
welding aluminum include electron beam welding and
laser beam welding. Both are described in this section.
ELECTRON BEAM WELDING
Electron beam welding (EBW) produces coalescence
with a concentrated beam, composed primarily of highvelocity electrons impinging on the joint. The process is
used with or without shielding gas and without the
application of pressure. This process is generally applicable to edge joints, butt joints, T-joints, corner joints,
and lap joints.15
Welding can be done in a chamber under high vacuum at a pressure of 1.2 × 10–4 Pa to 0.13 Pa (10–6 torr
15. Refer to Chapter 13 of American Welding Society (AWS) Welding Handbook Committee, 2007, Welding Processes, Part 2, ed. A.
O’Brien and C. Guzman, vol. 3,Welding Handbook, 9th ed., Miami:
American Welding Society. See Appendix B of this volume for a
detailed description of chapter contents for the five volumes of Welding
Handbook, 9th ed.
(C) Weld Power Too Low
Figure 1.45—Visual Appearance of
Satisfactory and Unsatisfactory CapacitorDischarge Welded Aluminum Studs
to 10–3 torr), at medium vacuum from 0.133 Pa to 330 Pa
(10–3 torr to 25 torr) or at atmospheric pressure using
helium shielding. In the latter case, the electron beam is
generated in a vacuum and exited to atmospheric pressure
through a series of ports.
Most aluminum alloys can be welded with EBW, but
cracking may occur with some of the heat-treatable
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
87
alloys, such as those in the 2XXX, 6XXX, and 7XXX
series. The addition of filler metal may help to prevent
weld cracking.
Wire feeders are available for use in EBW chambers.
Figure 1.46 shows a cross section from a weld in Alloy
6061-T6 made with filler metal supplied by a wire
feeder. Also, filler metals in the form of preplaced shims
can be used.
Joint Geometry
The square-groove joint design is typically used to
make electron beam welds with complete joint penetration. Figure 1.47 and Figure 1.48 show cross sections of
this type of weld. A concave bead may occur in some
instances, but this can be corrected by applying a second weld pass, with or without the addition of filler
metal. Root spiking and variation in joint penetration
(i.e., incomplete joint penetration) can occur when
welding thick sections in a single pass with the EBW
process. These problems are minimized by using multiple-pass autogenous welds or wire-fed EBW.
Figure 1.49 illustrates the multiple-pass autogenous
method that fuses base metal by supplementing the
weld metal with a raised surface feature with dimensions to suit the particular weld. The surface feature is
removed by machining after welding when a smooth
surface is required. Weld distortion can be corrected by
premachining the joints for dimensional compensation.
The joints shown in Figure 1.50 for multiple-pass
welding were developed for applications using a specific
thickness but may be modified for other thicknesses.
For example, details of the groove for joint (C) may be
used instead of the rectangular groove in joint (D) when
filling a thicker joint using filler metal. Figure 1.51
shows a multiple-pass weld with an autogenous root
pass and three wire-fed fill passes in Alloy 5083 with a
Figure 1.47—Single-Pass Electron Beam Weld in
Aluminum Alloy 5083 (Both Sides Machined
After Welding) (19.3 mm [0.760 in.] Thick)
(Magnified 7X)
thickness of 7.9 mm (0.31 in.). In this instance, the
addition of filler metal was not necessary to prevent
cracking in this alloy but was needed to fill the joint.
Equipment
Figure 1.46—Electron Beam Weld in Aluminum
Alloy 6061-T6 (5.4 mm [0.21 in.] Thick) with
ER4043 Filler Metal (Magnified 10X)
Aluminum alloys can be welded with either lowvoltage or high-voltage EBW equipment. Electron beam
welding machines are available from 60 V to 175 kV
and up to 100 kW of power. The choice of equipment
88
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
and procedures depends on the type and thickness of the
workpiece alloy, joint design, and service requirements.
Welding Conditions
Figure 1.48—Single-Pass Electron Beam Weld in
Aluminum Alloy 7049-T73 (4.1 mm [0.16 in.]
Thick) (Magnified 10X; Reduced to 67%)
Typical conditions for single-pass electron beam
welds in various aluminum alloys and thicknesses are
shown in Table 1.50.
Table 1.51, Table 1.52, and Table 1.53 show conditions developed for multiple-pass welding of Alloys 6061T6 and 5083-0 with the addition of filler metal and also
for multiple-pass autogenous welding of Alloy 5083-0.
(Refer to Figure 1.50 for joint geometries for these welds.)
Table 1.51 shows welding conditions for multiplepass electron beam welding of aluminum with coldwire fed filler metal of 5.3 mm (0.2 in.) Alloy 6061-T6.
(Refer to joint geometry in Figure 1.50[C].)
Table 1.52 shows welding conditions for multiplepass autogenous electron beam welds in Alloy 5083.
(Refer to joint geometry in Figure 1.50[D].)
Table 1.53 shows welding conditions for an autogenous electron beam root pass followed by multiple
passes with cold-wire-fed filler metal. (Refer to joint
geometry in Figure 1.50[D].)
Computer-controlled EBW machines are particularly
useful for multiple-pass autogenous welds and for automatically fed wire filler metal.
Depletion of Elements and Properties
(A) Root Bead
(B) Multiple-Pass
Figure 1.49—Autogenous Electron Beam
Weld on 5083 Aluminum (7.9 mm [0.31 in.]
Thick) (Magnified 7X; Reduced to 62%)
Some elements in aluminum alloys can be depleted
during electron beam welding, which will impact the
properties of the alloys. Magnesium can be depleted
from electron beam welds when Alloy 5083 is welded
using EBW in a vacuum environment. The 5% magnesium cold-wire-fed welds in Figure 1.52 were made
using the joint design shown (refer to Figure 1.50[D],
except that a bevel groove was used to accommodate
the automatically fed wire filler metal. The loss of
magnesium from the autogenous root bead was
between 0.6 wt % and 1.1 wt %. Lower losses of magnesium occurring in the second and third autogenous
beads resulted in a total loss of 1.1 wt %. There is an
increased loss of magnesium from the weld bead of the
third pass. The loss of other elements, such as zinc, can
be minimized.
The loss of alloying elements generally does not
result in a significant reduction in yield strength, but the
amount of loss must be determined for each application. Electron beam welds in nonheat-treatable aluminum alloys of the 1XXX, 3XXX, and 5XXX series
have properties equal to or better than those of gas
tungsten arc welds. Typical properties of electron beam
welds in some aluminum alloys compared to properties
of base metals are shown in Table 1.54.
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
F MAX.
R = A MAX.
(A)
Square Groove
7.5°
(B)
Complete Penetration Multiple-Pass Autogenous
D
F
G
R = A MAX.
R = C
L
M
J
E
H
B
A
K
7.5°
(C)
Complete Penetration Multiple-Pass Wire-Fed Filler
Key:
A = 0.25 mm (0.01 in.)
B = 0.51 mm (0.02 in.)
C = 0.64 mm (0.025 in.)
D = 0.76 mm (0.030 in.
E = 1.02 mm (0.040 in.)
F = 1.07 mm (0.042 in.)
G = 1.52 mm (0.060 in.)
H = 1.91 mm (0.075 in.)
J = 2.54 mm (0.100 in.)
(D)
Partial Penetration Multiple-Pass Autogenous
K = 3.18 mm (0.125 in.)
L = 4.65 mm (0.183 in.)
M = 7.87 mm (0.310 in.)
R = corner radius
Figure 1.50—Joint Designs for the Electron Beam Welding of Aluminum
Figure 1.51—Electron Beam Weld with an Autogenous
Root Bead and Three Cold-Wire-Fed Fill Beads Made
with Alloy 5356 Filler (7.9 mm [0.312 in.] Thick), Weld
Boss Removed (Magnified 8X; Reduced to 67%)
89
90
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
Table 1.50
Typical Conditions for Electron Beam Welding of Aluminum Alloys
Thicknessa
mm
in.
Alloy
Welding
Atmosphereb
1.27
1.27
3.05
3.17
3.17
9.65
12.70
16.00
19.05
25.40
50.80
60.45
152.40
0.050
0.050
0.120
0.125
0.125
0.38
0.50
0.63
0.75
1.00
2.00
2.38
6.00
6061
2024
2014
6061
7075
2219
2219
6061
2219
5086
5086
2219
5083
HV
HV
HV
HV
HV
Helium
HV
HV
HV
HV
HV
HV
HV
Beam
Voltage,
kV
Beam
Current,
mA
mm/s
in./min
kJ/m
kJ/in.
18
27
29
26
25
175
30
30
145
35
30
30
58
33
21
54
52
80
40
200
275
38
222
500
1000
525
42.3
30.0
31.7
33.8
38.1
23.3
40
31.7
21.1
12.7
15.2
18.2
4.2
100
71
75
80
90
55
95
75
50
30
36
43
10
14.17
18.90
51.18
39.37
51.18
299.21
149.61
259.84
259.84
590.55
984.25
1653.54
7165.34
0.36
0.48
1.3
1.00
1.3
7.6
3.8
6.6
6.6
15
25
42
182
Travel Speed
Energy Input
a. Square-groove butt joint.
b. HV = high vacuum (1.33 × 10–3 Pa [10–5 torr]).
Table 1.51
Welding Conditions for Multiple-Pass Electron Beam Welding of
5.4 mm (0.21 in.) Thick Alloy 6061-T6 with Cold-Wire Fed Alloy 4043 Filler Wirea
Travel Speed
a.
b.
c.
d.
Wire Feed Rated
Weld Passb
mm/s
in./mm
Beam Focus, mAc
mm/s
in./min
1
2
3
4
7.6
7.6
5.1
5.1
18
18
12
12
410
420
430
430
7.6
12.7
12.7
12.7
18
30
30
30
Refer to Figure 1.50(C) for joint geometry.
A hairpin filament gun was used. Voltage was constant at 75 kV. Beam current was constant at 9 mA.
Sharp focus at the root of the joint was 385 mA at a beam current of 2 mA.
Alloy 4043 wire was 0.76 mm (0.030 in.) in diameter.
Table 1.52
Welding Conditions for Multiple-Pass Autogenous Electron Beam Welding of Alloy 5083 a
a.
b.
c.
d.
Weld Speed
Weld Passb
Beam
Current, mA
mm/s
1
2
3
4
9.3
17.0
17.0
17.0
16.9
16.9
16.9
16.9
Beam Oscillationd
in./min
Beam
Focus (mA)c
mm
in.
40
40
40
40
495
520
520
540
None
0.03
0.03
0.03
None
0.080
0.080
0.080
Refer to Figure 1.50(D) for joint geometry.
A ribbon filament gun was used. Voltage was constant at 120 kV.
Sharp focus at the root of the joint was 470 mA at a beam current value of 2 mA.
The electron beam was oscillated transverse to the weld joint (X-direction) at 1 kHz to the dimension shown.
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
91
Table 1.53
Welding Conditions for Multiple-Pass Electron Beam Welding of
Alloy 5083: Autogenous Root Weld and Cold-Wire-Fed Weld Passesa
a.
b.
c.
d.
e.
Weld Speed
Weld Passb
Beam
Current, mA
mm/s
1
2, 3, 4
11
13
16.9
3.0
Beam Oscillationd
Wire Feed Ratee
in./min
Beam
Focus mAc
mm
in.
mm/s
in./min
40
7.04
500
510
(2.54) Y
(2.03) Y
(0.100) Y
(0.080) Y
None
19.0
None
45.0
Refer to Figure 1.50(D) for joint geometry.
A ribbon filament gun was used. Voltage was constant at 120 kV.
Sharp focus at the root of the joint was 470 mA at a beam current value of 2 mA.
The electron beam was oscillated longitudinal (Y-direction) or transverse (X-direction) at 1 kHz to the dimension shown.
Aluminum alloy 5356 wire was 0.9 mm (0.035 in.) in diameter.
DEPTH IN WELD, mm
2
1
5
3
4
5
6
7
4
3.4 wt %
MAGNESIUM CONTENT, wt %
3
2
• COLD-WIRE-FED EBW
• ALUMINUM ALLOY 5356 WIRE
• FILL WELD SPEED
6 mm/s (15 in./min)
1
0
5
4
3.9 wt %
3
• MULTIPASS AUTOGENOUS EBW
• FILL WELD SPEED
17 mm/s (40 in./min)
2
1
0
0
0.05
0.10
0.15
0.20
DEPTH IN WELD, in.
0.25
BASE METAL ~ 4.5 wt % Mg
Figure 1.52—Magnesium Content (Wt %) in Electron Beam Welds in Aluminum Alloy 5083
LASER BEAM WELDING
Laser beam welding (LBW) produces coalescence
with the heat from a laser beam impinging on the joint
and is performed using the heat generated by a highenergy-density photon (light) beam.16 Because the laser
16. Refer to Chapter 14 of American Welding Society (AWS) Welding Handbook Committee, 2007, Welding Processes, Part 2, ed. A.
O’Brien and C. Guzman, vol. 3, Welding Handbook, 9th ed., Miami:
American Welding Society. See Appendix B of this volume for a
detailed description of chapter contents for the five volumes of Welding Handbook, 9th ed.
beam can be focused very sharply, laser welds can penetrate comparatively thick joints while producing a very
narrow weld and a correspondingly narrow heataffected zone (HAZ) compared to arc welding processes. Because a smaller volume of metal is melted, less
heat energy goes into the workpiece.
When welding aluminum alloys, the reduction of
total heat input can have a beneficial effect. Almost all
industrial aluminum alloys are strengthened either by
precipitation hardening or strain hardening. The temperatures reached in the HAZ during arc welding are
sufficient to result in local overaging of precipitation-
92
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
Table 1.54
Properties of Aluminum Electron Beam Welds Compared to Base-Metal Properties
Average Tensile Strength
Base Metal
Specimen
Identitya, b
MPa
ksi
Average Yield Strength,
O.2% Offset
MPa
ksi
Average Tensile Elongation
% in 25.4 mm (1 in.)
% in 50.8 mm (2 in.)
22.0
Nonheat-Treatable Alloys
5083-0
5456-H321d
BM
290
42.0
145
21.0
—
AW
261
37.8
149
21.6
—
9.6
AWc
252
36.5
145
21.0
—
11.3
BM
317
46.0
228
33.0
—
12.0
AW
310
45.0
265
38.4
—
4.0
Heat-Treatable Alloys
2219-T87e
6061-T6
7039-T64
7039-0
7075-T6
BM
476
69.0
379
55.0
—
10.0
AW
317
46.0
228
33.0
—
3.0
BMf
310.
45.0
276
40.0
—
18.0
AW
238
34.5
199
28.9
—
10.0
AWg
210
30.4
154
22.3
7.0
—
BM
418
60.6
356
51.6
10.0
—
AW
298
43.2
256
37.2
3.8
—
WHT
309
44.8
305
44.2
1.8
BM
228
33.1
113
16.4
17.8
—
AW
227
32.9
116
16.9
14.7
—
BM
524
76.0
462
67.0
11.0
—
AW
348
50.5
299
43.3
2.0
—
WHT
483
70.1
416
60.4
6.0
—
a.
b.
c.
d.
e.
f.
Welds are autogenous except where addition of wire is indicated.
BM (base-metal specimen), AW (as-welded specimen), WHT (welded in heat-treated condition then reheat-treated specimen).
ER 5356 filler wire.
Hamilton Standard Electron Beam Welding Data Manual, Data Sheet No. 4.1.12 and 4.1.20.
Brennecke, M. W. 1965, Electron Beam Welded Heavy Gage Alloy 2219, Welding Journal, 44(1): 27-s–39-s.
Refer to American Society for Metals (ASM) International, 1990, Properties and Selection: Nonferrous Alloys and Special-Purpose Materials, Vol. 2, ASM
Handbook, 10th ed., Materials Park, Ohio: ASM International.
g. ER4043 filler metal.
hardened alloys or local annealing of strain-hardened
alloys. The effect of this overaging or annealing is a
degradation of the mechanical properties of the HAZ
compared to base-metal properties. This degradation
can be substantial. In high-strength arc-welded alloys in
the 2XXX series, a reduction of mechanical properties
of up to 50% or more is common.
The much narrower weld zone and heat-affected
zone made possible with laser beam welding results in a
much smaller volume of metal becoming overaged or
annealed during welding. This, in turn, results in higher
yield strength and tensile strengths in transverse tension
testing of laser beam welds than in arc welds of equal
thicknesses. There is, however, a disadvantage to a very
narrow HAZ: the mismatch of the mechanical properties (i.e., the weak HAZ compared to the stronger base
metal) is highly localized. In applications that involve
plastic deformation, the deformation strains are localized in the HAZ. As a consequence, transverse tension
tests of laser beam welds typically exhibit low elongation, not because of less ductility in the weld or HAZ,
but because all of the deformation occurs in the HAZ.
This can be a problem when forming components that
have been welded with the laser beam process; failure
occurs in the HAZ. Strain localization can also have an
AWS WELDING HANDBOOK
adverse effect on fatigue and impact properties of laser
beam welds.
The major difficulty in the laser beam welding of aluminum alloys is that aluminum does not couple well
with the light emitted by Nd:YAG (1.06 μm wavelength) and CO2 (10.5 μm wavelength) lasers. In other
words, the laser beam energy tends to be reflected
rather than absorbed by the aluminum, which does not
contribute to the energy required to melt the metal. On
polished aluminum surfaces, as much as 90% of the
laser energy is reflected. It should be noted that once a
weld pool and keyhole are established, the reflectivity
goes down dramatically, resulting in a power density
that is too high.
Early LBW control systems did not accommodate
this change in reflectivity. Control systems have been
developed that can vary the energy input to compensate
for the reflectivity change when the weld keyhole is
established.
Another way to reduce the reflectivity of the aluminum is to modify the surface by mechanical or chemical
roughening, painting on various absorptive coatings, or
anodizing and dyeing the aluminum surface. All of
these methods have been tried with varying degrees of
success.
These problems make aluminum more difficult to
weld with LBW than other common structural materials. Despite these difficulties, the aerospace industry is
successfully welding alloys in the 2XXX and 6XXX
series in many applications. Laser-beam aluminum-lithium Alloy 2090 and Alloy 2091 have been successfully
welded in laboratory development programs. The automotive industry has reported preliminary success in LBW
thin-gauge (0.8 mm to 2.0 mm [0.03 in. to 0.08 in.])
2XXX and 5XXX series alloy sheet. Although the general application of LBW to aluminum alloys requires
further developments of the process and equipment,
the use of LBW for aluminum alloys is increasing at a
moderate rate.
RESISTANCE WELDING
Resistance welding (RW) includes a group of welding processes producing coalescence of the faying surfaces with the heat obtained from the resistance of the
workpieces to the flow of the welding current in a circuit of which the workpieces form part of the circuit,
and by the application of pressure.
Some aluminum alloys are more suited for resistance
welding than others. (For the relative weldability of various wrought and cast alloys (refer to Table 1.4, Table
1.9, Table 1.15, and Table 1.18). In general, the casting
alloys that are considered weldable by other processes
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
93
can also be joined by resistance welding. Permanentmold and sand-casting alloys can be successfully spot
welded. Casting alloys can be spot welded to the same
casting alloy, to other casting alloys, and to wrought
alloys.17
The temper of an aluminum alloy affects weldability;
alloys with very low temper, especially –0, are very difficult to join with resistance welding.
Aluminum alloys in the annealed condition are more
difficult to weld with a resistance welding process than
the alloys in a work-hardened or solution-heat-treated
condition, due to deeper indentations, distortion, and
increased electrode pickup. Electrode life and weld consistency are improved when welding alloys with harder
temper.
JOINT DESIGN
The best joint properties for resistance spot welds are
obtained when welding aluminum alloys of equal thickness in the range of 0.71 mm to 3.2 mm (0.03 in. to
0.13 in.). Acceptable spot welds can be made in materials of unequal thickness with ratios ranging up to 3:1.
As the thickness ratio increases, the welding conditions
become more critical; thus, closely controlled welding
conditions are required to ensure that weld quality is
acceptable.
Resistance-welded joints in aluminum require greater
edge distance and joint overlap than those used for
steel. Suggested design dimensions and suggested resistance spot-weld spacing for varying thicknesses are provided in Table 1.55. Closer spacing than those indicated
in the table will require adjustment of the spot welding
schedule to account for increased shunting of current
through previous welds. When a flange is used on one
or both components, it should provide the required
overlap and it should be flat. Sometimes, spring-back
action will permit only the edge of the flange to contact
the other component. If the faying surfaces cannot be
brought together with light hand pressure, the flange
should be reworked.
Spot welds typically should be used when the weldment is expected to carry shear loads, not tensile or peel
loads. When tension or combined loadings are applied,
special tests should be conducted to determine the
strength required of the joint under expected service
conditions. The strength of the spot welds in tension
may vary from 20% to 90% of the shear strength.
17. Refer to Chapter 1 of American Welding Society (AWS) Welding
Handbook Committee, 2007, Welding Processes, Part 2, ed. A.
O’Brien and C. Guzman, vol. 3, Welding Handbook, 9th ed., Miami:
American Welding Society. Also refer to Resistance Welding Manufacturing Alliance (RWMA), 2003, Resistance Welding Manual, 4th
ed., Philadelphia: RWMA. See Appendix B of this volume for detailed
descriptions of chapter contents for the five volumes of Welding
Handbook, 9th ed.
94
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
Table 1.55
Minimum Design Dimensions for Resistance Spot-Welded Joints in Aluminum Sheet
Sheet Thicknessa
Nugget Diameter
mm
mm
in.
in.
Weld Spacingb
mm
in.
Edge Distancec
mm
in.
Joint Overlap
mm
in.
0.81
0.032
3.6
0.14
12.7
0.50
6.3
0.25
12.7
0.50
1.02
0.040
4.1
0.16
12.7
0.50
6.3
0.25
14.2
0.56
1.27
0.050
4.6
0.18
16.0
0.63
7.9
0.31
16.0
0.63
1.60
0.062
5.1
0.20
16.0
0.63
9.7
0.38
19.0
0.75
1.80
0.071
5.3
0.21
19.0
0.75
9.7
0.38
20.6
0.81
2.03
0.080
5.8
0.23
19.0
0.75
9.7
0.38
22.4
0.88
2.29
0.090
6.1
0.24
22.4
0.88
11.2
0.44
23.9
0.94
2.54
0.100
6.3
0.25
25.4
1.00
11.2
0.44
25.9
1.00
3.17
0.125
7.1
0.28
31.8
1.25
12.7
0.50
28.7
1.13
a. Data for other thicknesses may be obtained by interpolation, or the data for the next smaller thickness may be used.
b. Distance between centers of adjacent spot welds.
c. Distance from the center of a spot weld to the edge of the sheet or flange.
The shear strength of individual spot welds will vary
considerably with alloy composition, section thickness,
welding schedule, weld spacing, edge distance, and
overlap. Joint strength will depend on the average individual spot strength, the number of welds, and the positioning of the welds in the joint.
The minimum strength per weld and the minimum
average strength are shown in Table 1.56. Somewhat
lower strengths may be used for less critical industrial
applications in which less strength is needed. The
strengths shown in Table 1.56 are based on spot welds
with the minimum nugget diameters listed. Weld nuggets of a smaller diameter than those shown in the table
are not recommended. Nugget diameter and joint penetration are directly affected by changes in the welding
schedule and any changes in the electrode face geometry
caused by wear.
Surface Preparation
Welds of uniform strength and good appearance
depend on consistently low resistance of the surface
oxide thickness. The surface condition of as-received
material may be satisfactory for producing high-quality
welds for many commercial spot and seam welding
applications. Conversely, applications such as aerospace
components and other special equipment components
require very consistent welds of high quality; therefore
proper methods and uniform cleaning of the workpiece
surfaces and monitoring of the cleaning operation are
required.
For most resistance welding applications, some
cleaning, such as degreasing, is necessary before welding.
If thick oxide is present, a non-etching deoxidizer
should be used. Excellent results have been produced by
immersion in a room-temperature nitric-hydrofluoric
solution for 2 minutes to 6 minutes.
It should be noted that all acids used in cleaning
solutions have the potential to be extremely hazardous.
Personnel using them should be thoroughly familiar
with all chemicals involved and adequate safety
equipment should be used. Refer to the Safe Practices
section for precautions related to the use of acid cleaning
solutions.
After immersion of the workpieces,
subsequent actions are the following:
1. 30 seconds in a cold rinse under running water,
2. 10 seconds in a hot water rinse (60°C to 71°C
[140°F to 160°F]), and
3. Drying in a warm air blast.
Surface Contact Resistance. Measurement of
surface contact resistance is an effective method of
monitoring a cleaning operation. Figure 1.53 shows a
diagram of a surface-resistance measuring device. Two
cleaned coupons are overlapped and placed between
two radius-faced spot-welding electrodes that are 76
mm (3 in.). A standardized current and electrode force
are applied; a current of 50 mA and a force of 2.67 kN
(600 lb) are frequently used. The voltage drop between
the two coupons is measured with a millivolt meter or a
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
95
Table 1.56
Minimum Tension-Shear Strength for Resistance Spot Welds in Aluminum Alloys (MIL-W-6858D)
Base Metal Tensile Strength
Below 134 MPa
(19.5 ksi)
134 MPa–241 MPa
(19.5 ksi–35 ksi)
241 MPa–386 MPa
(35 ksi–56 ksi)
386 MPa (56 ksi)
and above
Tension-Shear Strength per Weld
Thickness
of Thinner
Sheet,
mm (in.)
Minimum
Nugget
Diameter,
mm (in.)
Min.
N (lb)
Min. Avg.*
N (lb)
Min.
N (lb)
Min. Avg.*
N (lb)
Min.
N (lb)
Min. Avg.*
N (lb)
Min.
N (lb)
Min. Avg.*
N (lb)
0.4
(0.016)
2.2
(0.085)
222
(50)
289
(65)
311
(70)
400
(90)
445
(100)
556
(125)
489
(110)
623
(140)
0.5
(0.020)
2.5
(0.10)
336
(80)
445
(100)
445
(100)
125
(556)
601
(135)
756
(170)
623
(140)
778
(175)
0.6
(0.025)
3.0
(0.12)
489
(110)
623
(140)
645
(145)
823
(185)
778
(175)
890
(200)
823
(185)
1045
(235)
0.8
(0.032)
3.6
(0.14)
734
(165)
934
(210)
934
(210)
1179
(265)
1045
(235)
1312
(295)
1157
(260)
1446
(325)
1.0
(0.040)
4.1
(0.16)
1001
(225)
1268
(285)
1334
(300)
1668
(375)
1379
(310)
1735
(390)
1535
(345)
1935
(435)
1.3
(0.050)
4.6
(0.18)
1312
(295)
1646
(370)
1779
(400)
500
(2224)
430
(1913)
2402
(540)
465
(2068)
2602
(585)
1.6
(0.062)
5.1
(0.20)
1757
(395)
2202
(495)
2535
(570)
3180
(715)
2713
(610)
3403
(765)
2980
(670)
3737
(840)
1.8
(0.071)
5.3
(0.21)
2002
(450)
2513
(565)
2869
(645)
3603
(810)
3203
(720)
4003
(900)
3670
(825)
4604
(1035)
2.0
(0.080)
5.8
(0.23)
2335
(525)
2936
(660)
3403
(765)
4270
(960)
855
(3803)
4760
(1070)
4559
(1025)
5716
(1285)
2.3
(0.090)
6.1
(0.24)
2647
(595)
3314
(745)
3870
(870)
4849
(1090)
4448
(1000)
1250
(5560)
5583
(1255)
6984
(1570)
2.5
(0.100)
6.4
(0.25)
3003
(675)
3759
(845)
4181
(940)
5227
(1175)
5204
(1170)
6517
(1465)
6628
(1490)
8296
(1865)
3.2
(0.125)
7.1
(0.28)
3492
(785)
4381
(985)
4671
(1050)
5849
(1315)
7228
(1625)
9052
(2035)
9430
(2120)
11 788
(2650)
3.6
(0.140)
7.6
(0.30)
—
—
—
—
—
—
—
—
8541
(1920)
10 676
(2400)
11 232
(2525)
14 056
(3160)
4.1
(0.160)
8.1
(0.32)
—
—
—
—
—
—
—
—
10 854
(2440)
13 567
(3050)
13 878
(3120)
17 348
(3900)
4.6
(0.180)
8.6
(0.34)
—
—
—
—
—
—
—
—
13 345
(3000)
16 681
(3750)
16 570
(3725)
20 729
(4660)
4.8
(0.190)
8.9
(0.35)
—
—
—
—
—
—
—
—
14 412
(3240)
18 015
(4050)
17 949
(4035)
22 441
(5045)
6.4
(0.250)
—
—
—
—
—
—
—
—
—
—
28 469
(6400)
35 586
(8000)
32 694
(7350)
40 924
(9200)
*Average of three or more tension-shear tests.
96
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
STANDARD FORCE
MILLIAMMETER
MILLIVOLTMETER
ELECTRODES
CURRENT
ADJUSTMENT
STANDARD FORCE
Figure 1.53—Arrangement for Measuring Surface
Contact Resistance for Monitoring Cleanness
Kelvin bridge. The resistance between the two coupons
is then calculated from the current and voltage
readings, as follows:
R = E/I
(1.1)
where
R = Resistance in ohms (Ω)
E = Electromotive force in volts (V)
I = Current in amps (A)
It is important that all tests are carried out under
identical conditions because the results are sensitive to
small changes in procedure. Average surface resistance
is usually obtained from at least five readings on each
set of coupons. The coupons must not move as
electrode force is applied because movement may break
the oxide coating and cause false readings. With this
test, the contact resistance between properly cleaned
aluminum sheets will range from 10–5 Ω to about 10–
4 Ω; contact resistance of uncleaned stock may range
up to 10–2 Ω or higher.
Resistance Spot Welding
Resistance spot welding (RSW), a resistance welding
process that produces a spot weld, is a practical joining
method for fabricating aluminum sheet structures. It
can be used with all wrought alloys and also with many
permanent-mold and sand-cast alloys.
The procedures and equipment for spot welding aluminum are similar to those used for steels; however, the
higher thermal and electrical conductivity of aluminum
alloys require some variations in equipment and welding schedules. For example, the weld current must be
two to three times higher, but only one-third the cycle
time than that required for a comparable joint between
steel sections.
Equipment
Power sources that produce continuous or pulsed dc
are preferred. Aluminum can be welded with either
alternating current (ac) or direct current (dc). Acceptable welds for some applications can be made with single-phase ac equipment.
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
97
High welding current is required because of the high
electrical conductivity of aluminum. Consequently, the
primary power demand is higher than that required for
spot welding an equivalent thickness of steel. In any
case, the welding machine should be equipped with a
low-inertia force system to provide fast electrode follow-up as the weld nugget is formed. In addition, a
forging force system may be necessary to consistently
produce crack-free welds, particularly in heat-treatable
aluminum alloys in the 2XXX, 6XXX, and 7XXX
series.
Electrodes
Standard electrodes with radius-contoured faces are
used on both sides of the joint for most welding operations. To prevent unacceptable surface marking, a flatfaced electrode can be used on one side. When this is
done, the heat balance in the joint must be considered.
Resistance welding electrode materials are classified
by the Resistance Welding Manufacturing Alliance
(RWMA).18 The RWMA Group A, Class 1 copperalloy electrodes are recommended for the spot welding
of aluminum. Class 1 alloys have the highest electrical
conductivity of the Group A alloys. Class 2 alloys are
sometimes used when greater hardness is needed to
maintain contour and reduce tip wear common with
high electrode forces.
A brittle copper-aluminum alloy with relatively low
electrical conductivity, called electrode pickup, tends to
form on the face of each electrode during use. As this
alloy coating builds up, the contact resistance increases
and the electrode pickup tends to stick to the surface of
the aluminum workpiece. Electrode pickup mars the
surface, produces an unpleasant appearance, and may
also pull particles of the copper-aluminum alloy from
the electrode face. This action increases the surface
roughness and also increases the rate of electrode deterioration. It may also reduce the size of the weld nugget
and radically change the nugget shape.
Excessive electrode pickup is generally the result of
improper surface preparation of the workpieces prior
to welding, insufficient electrode force, or excessive
welding current. The unwanted coating on the electrode
faces can be removed by periodic dressing of the electrodes with an appropriately shaped tool covered with
a fine abrasive cloth, as shown in Figure 1.54. The
original face contour of the electrode must be carefully
maintained. A file should not be used to dress the
electrode.
18. Refer to Resistance Welding Manufacturing Alliance (RWMA),
1996, Bulletin 16: Resistance Welding Equipment Standards, Philadelphia: RWMA.
18-137009
REPLACEABLE 2 in.
ROLL ABRASIVE
CLOTH
Source: NSRW, Inc.
Figure 1.54—Tip Dressing Tool
with an Abrasive Cloth
Schedules, Spot Welding
Suggested schedules for spot welding with three
types of machines are shown in the following tables:
Table 1.57 shows schedules for single-phase alternatingcurrent machines. Table 1.58 provides this information
for three-phase frequency converter machines, and
Table 1.59 contains suggested schedules for three-phase
rectifier machines. These tables can be used as guides
for establishing production welding schedules.
Resistance Seam Welding and Roll Spot
Welding
The resistance seam welding (RSEW) process produces a weld at the faying surfaces of overlapped workpieces progressively along a length of a joint. The weld
may be made with overlapping weld nuggets, a continuous weld nugget, or by forging the joint as it is heated
to the welding temperature by resistance to the flow of
the welding current.
Roll spot welding is a resistance seam welding process variation that produces spot welds at intervals
using one or more circular electrodes that are rotated
continuously or intermittently.
Resistance seam welding and roll spot welding are
very similar to resistance spot welding except that copper alloy circular electrodes are used. Seam welding
consists of a series of overlapping weld nuggets capable
of forming a gas-tight or liquid-tight joint. Roll spot
98
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
Table 1.57
Suggested Schedules for Spot Welding of
Aluminum Alloys with Single-Phase Alternating-Current Machines
Electrode Face Radii,
Top-Bottom
Thickness*
Net Electrode Force
mm
in.
mm
in.
N
lb
Approximate
Welding
Current, kA
0.81
0.032
51-51 or
51-Flat
2-2 or
2-Flat
2224
500
26
7
1.02
0.040
76-76 or
76-Flat
3-3 or
3-Flat
2669
600
31
8
1.27
0.050
76-76 or
76-Flat
3-3
3-Flat
3025
680
33
8
1.57
0.062
76-76 or
76-Flat
3-3 or
3-Flat
3336
750
36
10
1.78
0.070
102-102
4-4
3559
800
38
10
2.06
0.081
102-102
4-4
3914
880
42
10
2.29
0.090
152-152
6-6
4226
950
46
12
2.54
0.100
152-152
6-6
4671
1050
56
15
2.79
0.110
152-152
6-6
5115
1150
64
15
3.17
0.125
152-152
6-6
5783
1300
76
15
Welding Time,
Cycles
(60 Hz)
*Thickness of one sheet of a two-sheet combination.
Table 1.58
Suggested Schedules for Spot Welding of Aluminum Alloys
with Three-Phase Frequency Converter Machines
Electrode Force
Sheet
Thicknessa
Electrode
Face Radiib
Weld
N
Current, kAc
Forge
mm
in.
mm
in.
lb
0.64
0.025
76
3
2224
500
0.81
0.032
102
4
3114
1.02
0.040
102
4
1.27
0.050
102
1.60
0.062
1.80
N
Time, Cycles
(60 Hz)
lb
Weld
Postheat
Weld
Postheat
6672
1500
34
8.5
1
3
700
8007
1800
36
9.0
1
4
3559
800
8896
2000
42
12.6
1
4
4
4003
900
10 231
2300
46
13.8
1
5
152
6
5783
1300
13 345
3000
54
18.9
2
5
0.071
152
6
7117
1600
16 014
3600
61
21.4
2
6
2.03
0.080
152
6
8896
2000
19 127
4300
65
22.8
3
6
2.29
0.090
152
6
10 676
2400
23 575
5300
75
30.0
3
8
2.54
0.100
203
8
12 455
2800
30 248
6800
85
34.0
3
8
3.17
0.125
203
8
17 793
4000
40 034
9000
100
45.0
4
10
a. Thickness of thinnest sheet of a two-sheet combination.
b. Top and bottom electrode face radii are identical.
c. Suitable for Alloys 2014-T3, -T4, and -T6; 2024-T3 and -T4; 7075-T6. Somewhat lower current may be used for softer alloys, such as 5052, 6009, and 6010.
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
99
Table 1.59
Suggested Schedules for Spot Welding of Aluminum Alloys with Three-Phase Rectifier Machines
Electrode Force
Sheet
Thicknessa
Electrode
Face Radiib
mm
in.
mm
in.
0.81
0.032
76
3
Weld
N
2980
Current, kAc
Forge
lb
670
N
6850
Time, Cycles
(60 Hz)
lb
Weld
Postheat
Weld
Postheat
1540
28
0
2
0
1.02
0.040
76
3
3247
730
8007
1800
32
0
3
0
1.27
0.050
203
8
4003
900
10 008
2250
37
30
4
4
1.60
0.062
203
8
4893
1100
12 900
2900
43
36
5
5
1.80
0.071
203
8
5293
1190
14 412
3240
48
38
6
7
2.03
0.080
203
8
6494
1460
16 903
3800
52
42
7
9
2.29
0.090
203
8
7562
1700
19 127
4300
56
45
8
11
2.54
0.100
203
8
8452
1900
22 241
5000
61
49
9
14
3.17
0.125
203
8
11 121
2500
28 913
6500
69
54
10
22
a. Thickness of one sheet of a two-sheet combination.
b. Top and bottom electrode face radii are identical.
c. Suitable for Alloys 2014-T3, -T4, and -T6; 2024-T3 and -T4; 7075-T6. Somewhat lower current may be used for softer alloys, such as 5052, 6009, and 6010.
welding consists of a series of uniformly spaced individual spot welds. The same equipment used for seam
welding can be used for roll spot welding by adjusting
the interval between weld heat cycles (cool time or off
time).
Welding may take place while the circular electrodes
and the workpieces are in motion or while they are
momentarily stopped. Surface appearance and weld
quality will be better when the electrodes and workpieces are stationary. With moving electrodes, the weld
nugget moves from between the electrodes before the
nugget is adequately cooled. The welding force is maintained on the nugget during solidification and cooling.
Equipment. Equipment used for roll spot welding or
seam welding usually has features similar to those of
spot welding machines. Somewhat higher welding currents and electrode forces may be required for these
processes because the shunting of current through the
previous nugget may be greater than that which occurs
with spot welding. Excessive travel speed can contribute to aluminum pickup on the circular electrodes. This
can be corrected by increasing the time between welds
and decreasing the travel speed to produce the preferred
number of welds per unit length.
Electrodes. Radius-faced circular electrodes are typically used. Face radii generally range from 25 mm to
250 mm (1 in. to 10 in.). Typically, the face radius
should be about the same as the circular electrode
radius to achieve a spherical radius in contact with the
workpieces. The faces should be cleaned after every 3 to
5 revolutions of continuous welding, and after every 10
to 20 revolutions of roll spot welding. An appropriate
cutting tool may be used for cleaning. The electrodes
can also be cleaned continuously with a medium-to-fine
grade abrasive material bearing against each electrode
face under 22 N to 45 N (5 lb to 10 lb) of force.
Schedules. Typical settings for the resistance seam
welding of Alloy 5052-H34 aluminum sheet with single-phase alternating-current seam-welding machines
are shown in Table 1.60. These data can be used as a
guide when developing welding schedules for other
alloys or tempers. Quality control for roll spot welding
and seam welding is the same as that required for spot
welding.
Weld Quality. The quality of roll spot welds and seam
welds in aluminum alloys is more sensitive to process
variations than similar welds in steel. This is related to
the high resistivity of aluminum oxides and the high
electrical and thermal conductivity of the metal. The
size of the weld nugget is very sensitive to the heat
energy developed by the resistance of the workpieces to
the welding current. The energy must be produced rapidly to overcome losses to the surrounding base metal
and the electrodes.
The contact resistance between the faying surfaces
and between the electrodes and the workpieces is a sig-
100
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
Table 1.60
Typical Schedules for Gas-Tight Seam Welds in 5052-H34
Aluminum Alloy with Single-Phase Alternating-Current Machines
mm
in.
per m
per in.
On + Off
Time,
Cycles
(60 Hz)b
0.64
0.025
709
18
5-1/2
Sheet Thicknessa
a.
b.
c.
d.
Welds
Travel Speedc
On Times, Cycles
(60 Hz)
Electrode Force
mm/s
ft/min
Min.
Max.
N
15.2
3.0
1
1-1/2
2669
Approximate
Weld Widthd
lb
Welding
Current,
kA
mm
in.
600
26.0
2.8
0.11
0.81
0.032
630
16
5-1/2
17.2
3.4
1
1-1/2
3069
690
29.0
3.3
0.13
1.02
0.040
551
14
7-1/2
14.7
2.9
1-1/2
2-1/2
3381
760
32.0
3.6
0.14
1.27
0.050
472
12
9-1/2
13.2
2.6
1-1/2
3
3825
860
36.0
4.1
0.16
1.60
0.062
394
10
11-1/2
13.2
2.6
2
3-1/2
4270
960
38.5
4.8
0.19
2.03
0.080
354
9
15-1/2
10.6
2.1
3
5
4849
1090
41.0
5.6
0.22
2.54
0.100
315
8
20-1/2
9.1
1.8
4
6-1/2
5471
1230
43.0
6.6
0.26
3.17
0.125
276
7
28-1/2
7.6
1.5
5-1/2
9-1/2
6005
1350
45.0
8.1
0.32
Thinner of a two-sheet combination.
Use next higher full cycle setting if timer is not equipped for synchronous initiation.
Should be adjusted to give the desired number of spots per inch.
Welding force, welding current, or both should be adjusted to produce the desired weld width. Use lower force for soft alloys or tempers and higher force
for hard alloys or tempers.
nificant part of the total resistance in the circuit. Significant variations in these contact resistances can cause
large changes in the density of the welding current.
Because contact resistance is affected by the condition
of the aluminum surfaces, uniform cleanliness is essential for consistent weld quality.
The contact resistance between the electrodes and
the workpieces increases as electrode pickup on the
electrode faces increases, and as contact resistance
increases, so does electrode heating and wear. As the
contact area increases, welding current density
decreases, which results in reduced nugget size and joint
penetration. Weld strength decreases at the same time.
Electrode wear requires constant attention.
Other important factors that affect weld quality are
surface appearance, internal discontinuities, sheet separation, metal expulsion, weld strength, and weld ductility. Uniform weld quality can be obtained only with the
use of proper equipment, well trained operators, and
adherence to qualified welding schedules and procedures developed prior to production. Procedures should
be monitored and maintained during production with a
regular program of quality control.
Discontinuities
Factors that tend to produce cracks or porosity in
welds are excessive heating of the nugget, cooling rate,
and improper application of the electrode force. Spot
welds in some high-strength alloys, such as 2024 and
7075, are susceptible to cracking if the welding current
is too high or the electrode force is too low. The cooling
rate can be controlled by the application of current
downslope or a postheat cycle. With dual-force
machines, proper adjustment of the forge delay time
may assist in preventing cracking.
Quality Control
The quality of aluminum roll spot and seam welds
depends on the welding schedule, electrode condition,
and surface preparation. All three must be controlled to
maintain acceptable weld quality.
Quality criteria for resistance welds should be established for the intended application. When service conditions for resistance welds vary for a particular product,
a range of quality standards based on service and reliability requirements should be developed. Quality criteria for military hardware and aircraft are established by
military specifications.
FLASH WELDING
Flash welding (FW) is a resistance welding process
that produces a weld at the faying surfaces of butting
members by the rapid upsetting of the workpieces after
a controlled period of flashing action. All aluminum
AWS WELDING HANDBOOK
alloys can be joined by the flash welding process.19 This
process is particularly adapted to making butt joints or
corner joints composed of two components of similar
cross section. Flash welding can be used to join aluminum to copper.
Good mechanical properties are obtained in flashwelded joints, and joint efficiency of at least 80% is
readily obtained. Strength is generally higher when the
alloy is in a hard temper condition. Heat treatment
after flash welding may increase joint efficiency.
Flash welding equipment used to weld aluminum is
similar to that used for welding steel, except that more
rapid platen acceleration and upset force are applied
and higher welding currents are necessary. Electrodes
may be fabricated from tool steels to prevent sticking of
the aluminum to copper surfaces and also to provide a
sharp edge to shear off the flash at the conclusion of the
upset. Bend tests or tensile tests, or both, are used to
determine joint strength and to assess weld quality.
HIGH-FREQUENCY RESISTANCE WELDING
High-frequency resistance welding (HFRW) includes
a group of resistance welding process variations that
use a welding current frequency of at least 10 kHz to
concentrate the welding heat at the desired location.
Resistance welding with high-frequency current is
used primarily for high-speed production of tubing. In
this application, squeeze rolls forge the linear edges of
the sheet together after they are heated to the welding
temperature with high-frequency current. Tubing with
wall thicknesses of 0.76 mm to 3.2 mm (0.03 in. to
0.125 in.) can be welded at high travel speeds.20
Equipment
Equipment for HFRW includes a power source,
induction coils, contacts, impeders, control devices, and
mechanical equipment for the preparation and alignment of the workpieces.
High-frequency generators and associated control
systems require the standard care and safety precautions used in handling or repairing all electrical devices.
19. Refer to Chapter 3 of American Welding Society (AWS) Welding
Handbook Committee, 2007, Welding Processes, Part 2, ed. A.
O’Brien and C. Guzman, vol. 3, Welding Handbook, 9th ed., Miami:
American Welding Society. See Appendix B of this volume for
detailed descriptions of chapter contents for the five volumes of Welding Handbook, 9th ed.
20. Refer to Chapter 5 of American Welding Society (AWS) Welding
Handbook Committee, 2007, Welding Processes, Part 2, ed. A.
O’Brien and C. Guzman, vol. 3, Welding Handbook, 9th ed., Miami:
American Welding Society. See Appendix B of this volume for
detailed descriptions of chapter contents for the five volumes of Welding Handbook, 9th ed.
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
101
Voltages range from 400 V to 20,000 V and frequencies
from 100 kHz to 800 kHz. Proper care and safety precautions must be taken while working on high-frequency generators and associated control systems.
(Refer to “High-Frequency Generators” in the Safe
Practices section of this chapter.)
SOLID-STATE WELDING
Solid-state welding (SSW) includes a group of welding processes that produce coalescence by the application of pressure without melting any of the joint
components. Cold welding, diffusion welding, explosion welding, roll welding and variations of friction
welding are among the solid-state processes that can be
used to weld aluminum.
COLD WELDING
Cold welding (CW) is a solid-state process in which
pressure is applied to produce a weld at room temperature with substantial deformation at the weld.21 A fundamental requisite of cold welding is that at least one of
the workpieces is highly ductile and does not undergo
significant work hardening. Butt joints and lap joints
can be made with cold welding.
The weld flash (metal expelled from the joint during
welding) in cold-welded butt joints must be removed
mechanically by grinding or machining. The plastic
deformation occurring in a butt joint during cold welding breaks up aluminum oxides on the surface, and the
oxides are expelled from the joint. Preweld cleaning for
cold welding is not as critical for the cold welding of
butt joints as it is for lap joints; precleaning lap joints
for cold welding is critical. The preferred methods are
degreasing and wire brushing of the faying surfaces.
Because there is no heat-affected zone, the weld in a
butt joint is as strong, or nearly as strong, as the base
material. Cold welding can be used to join many aluminum alloys that cannot be welded by an arc welding
process because of susceptibility to cracking. For example, butt joints in Alloy 2024 and Alloy 7075 have been
successfully produced using cold welding, but lap joints
have not.
21. Refer to Chapter 15 of American Welding Society (AWS) Welding Handbook Committee, 2007, Welding Processes, Part 2, ed. A.
O’Brien and C. Guzman, vol. 3, Welding Handbook, 9th ed., Miami:
American Welding Society. See Appendix B of this volume for detailed
descriptions of chapter contents for the five volumes of Welding
Handbook, 9th ed.
102
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
Butt joints and corner joints can be made in most
aluminum alloy wire, rod, tubing, and simple extruded
shapes. Lap joints can be welded in sheet. Butt joints in
soft annealed alloys require a total upset distance of
approximately 1.5 times the thickness of the workpieces. Producing an acceptable weld in the higherstrength alloys requires a greater upset distance of
approximately 4 to 5 times the workpiece thickness.
Welds in lap joints require a thickness reduction of
about 70% at the weld location and are only practical
in the low-strength alloys in the 1XXX and 3XXX
series. These welds provide good shear strength but do
not perform well when subjected to a bending or peeling type of load.
AWS WELDING HANDBOOK
strength as resistance spot or seam welds. The strength
of ultrasonic welds in the higher-strength alloys can
exceed the strength of resistance welds. The primary
reasons are that ultrasonic welding does not produce a
heat-affected zone in the base metal and the size of the
weld is usually greater.
Ultrasonic welding generally requires less surface
preparation than that required for resistance welding,
but degreasing the aluminum is usually advisable. To
obtain uniform welds, surface oxides on heat-treated
alloys and alloys containing high percentages of magnesium should be removed before welding.
EXPLOSION WELDING
Ultrasonic welding (USW) is a solid-state welding
process that produces a weld by the local application of
high-frequency vibratory energy as the workpieces are
held together under pressure.22
Ultrasonic welding is used to join foil and sheet
gauges of aluminum alloys and also to join thin wires to
sheet or foil. The thickness limit of the sheet in contact
with the ultrasonic horn is the thinner of stack-up
gauges. The opposing sheet that is in contact with the
anvil can be thicker than the governing gauge on the
horn side.
The sheet on the horn side for the ultrasonic welding
of a lap joint in aluminum alloys is usually 1.5 mm
(0.060 in.), although spot welds have been made in
thicknesses up to 3.2 mm (0.13 in.). The anvil side sheet
can be up to 25.4 mm (1 in.) thick. The types of welds
possible with the ultrasonic process are spot welds, roll
spot welds, seam welds, and lap welds.
All aluminum alloys can be ultrasonically welded,
but the degree of weldability varies with the type and
temper of the alloy. Aluminum alloys can also be joined
to other metals with this process.
Ultrasonic welding can be carried out with minimum
surface preparation, with minimum deformation, and
with low compressive loads. The welds look much like
resistance spot or seam welds, but they are often characterized by a localized roughened surface. Reduction
in thickness of an ultrasonic weld in a lap joint is about
5%, which can be compared to a 70% reduction in a
cold weld.
For relatively low-strength aluminum alloys, ultrasonic spot welds exhibit approximately the same
Explosion welding (EXW) is a solid-state welding
process that produces a weld by high-velocity impact of
the workpieces as the result of controlled detonation.
The technology of explosion welding is described in
Chapter 9 of Volume 3, Welding Handbook.23 An overview is presented in this section.
Typically, three components are used in explosion
welding: the base plate (backing plate), the cladding
plate, and the explosive. The backing plate generally
remains stationary, and the cladding plate is usually
positioned parallel to it. A specified space, the standoff
distance, separates the two workpieces, as shown in
Figure 1.55. On detonation, the explosion locally bends
and accelerates the cladding plate across the stand-off
distance at a high velocity so that it collides at an angle
with the backing plate. The angular collision and welding front progresses across the joint, and in a fraction of
a second, a high-strength weld with minimum diffusion
and deformation at the interface is produced. The characteristic wavy profile of an explosion welded joint is
shown in Figure 1.56.
As pressure forces the two surfaces into intimate
contact and causes localized plastic flow in the immediate area of the collision point, a jet forms at the point of
collision (refer to Figure 1.55). The jet sweeps away the
original surface layer on each component, along with
any contaminating film that might be present. This
exposes clean underlying metal, which is required to
make a strong metallic bond. Residual pressures within
the system are maintained long enough after the collision to avoid release of the contact of the metal components and the weld is completed.
Explosion welding is essentially a low-temperature
process; intense heating and melting of the workpiece
22. Refer to Chapter 8 of American Welding Society (AWS) Welding
Handbook Committee, 2007, Welding Processes, Part 2, ed. A.
O’Brien and C. Guzman, vol. 3, Welding Handbook, 9th ed., Miami:
American Welding Society. See Appendix B of this volume for
detailed descriptions of chapter contents for the five volumes of Welding Handbook, 9th ed.
23. Refer to Chapter 9 of American Welding Society (AWS) Welding
Handbook Committee, 2007, Welding Processes, Part 2, ed. A.
O’Brien and C. Guzman, vol. 3, Welding Handbook, 9th ed., Miami:
American Welding Society. See Appendix B of this volume for detailed
descriptions of chapter contents for the five volumes of Welding
Handbook, 9th ed.
ULTRASONIC WELDING
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
103
Source: Dynamic Materials Corporation.
Figure 1.55—Schematic of the Explosion Welding Process
Common applications are the cladding of carbon steel,
stainless steel, copper, or titanium alloys with aluminum. Explosion-welded bimetallic sections are primarily
used as transition segments for subsequent fabrication.
Conventional welding processes are then used to weld
similar metal on each side of the transition segment.
The net effect is to facilitate the joining of aluminum to
another metal to produce a bimetallic transition joint.
Surface preparation for the explosion welding of aluminum is similar to that used for other welding processes. The faying surfaces should be cleaned shortly
before welding. The typical surface oxides are broken
up and dispersed during welding.
Micrograph courtesy of Dynamic Materials Corporation
Figure 1.56—A Micro-Etch of the Characteristic
Wavy Profile of an Explosion-Welded Joint
does not occur. The faying surfaces, however, are heated
to some extent by the energy of the collision, and welding is accomplished through plastic flow of the metal on
those surfaces.
Explosion welding is limited to lap joints and to the
cladding of workpieces with a second metal, which is
often applied to provide special properties to the substrate metal.
DIFFUSION WELDING
Diffusion welding (DFW) is a solid-state welding
process that produces a weld by the application of pressure at elevated temperature, with no macroscopic
deformation or relative motion of the workpieces. A
solid filler metal may be inserted between the faying surfaces. Joint formation takes place with the migration of
atoms from each of the two workpieces into the other.24
24. Refer to Chapter 12 of American Welding Society (AWS) Welding Handbook Committee, 2007, Welding Processes, Part 2, ed. A.
O’Brien and C. Guzman, vol. 3, Welding Handbook, 9th ed., Miami:
American Welding Society. See Appendix B of this volume for detailed
descriptions of chapter contents for the five volumes of Welding
Handbook, 9th ed.
104
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
A means to prevent, disrupt, or dissolve the surface
oxides must be implemented for the diffusion welding
of aluminum alloys. The weld can be expedited and
weld strength can be achieved by inserting a thin intermediate layer of another metal, such as silver, copper,
or a gold-copper alloy, into the joint. A wide range of
temperatures, times, and pressures may be used. The
welding operation must be performed under vacuum or
in an inert gas atmosphere.
FRICTION WELDING
Friction welding (FRW) is a solid-state welding process that produces coalescence of materials under
compressive-force contact of the workpieces rotating or
moving relative to one another to produce heat and plastically displace material from the faying surfaces.25 The
plastically displaced material, called flash, may be
removed in a later operation to produce a smooth surface.
Almost all aluminum alloys can be successfully
joined by friction welding, including the 2XXX and
7XXX series, some of which typically cannot be welded
by the arc processes because of susceptibility to cracking. With FRW, the aluminum workpieces, even highstrength, heat-treatable aluminum alloys, are softened
by frictional heating; plastically displaced base metal is
expelled from the joint, resulting in joint strength that
approaches that of the base material. The aluminum
oxide present on the faying surfaces is also broken up
and expelled from the joint; therefore, preweld cleaning
is not as critical as it is for other welding processes.
While not all material combinations are joinable,
aluminum alloys can be readily welded to many other
materials using friction welding. Two of the more common dissimilar metal combinations are aluminum to
copper alloys, used in the electrical industry, and aluminum to stainless steel, used as transition couplings in
piping systems and pressure vessels.
Linear friction welding is an adaptation of friction
welding in which a linear back-and-forth motion is used
to produce heat and coalescence of the workpiece under
axial-force contact.
Most friction welding is based on rotary motion and
is best applied to joining circular parts (i.e., rod, bar,
wire, tube, and pipe). The linear friction welding technique was developed to weld configurations other than
those of circular symmetry.26
25. Refer to Chapters 6 and 7 of American Welding Society (AWS) Welding Handbook Committee, 2007, Welding Processes, Part 2, ed. A. O’Brien
and C. Guzman, vol. 3, Welding Handbook, 9th ed., Miami: American
Welding Society. See Appendix B of this volume for detailed descriptions
of chapter contents for the five volumes of Welding Handbook, 9th ed.
26. Linear friction welding was developed in the 1980s at The Welding Institute (TWI) in Cambridge, United Kingdom. The process uses
linear oscillation, which allows FRW technology to be applied to nonround components.
AWS WELDING HANDBOOK
Linear friction welding is currently being used for the
production of critical aerospace engine components
(e.g., blisks) and the technique is being assessed for the
manufacture of main airframe structures. Production
applications of this process often involve the joining of
titanium alloys; however, linear friction welding is suitable for almost all aluminum alloys and also for a range
of dissimilar material combinations.
Generating frictional heat for linear friction welding
is achieved by the rubbing contact of the surface of a
laterally reciprocating component against the surface of
a stationary component under axially applied pressure,
as shown in Figure 1.57. The faying surfaces are rapidly
heated and softened, and after a pre-set time, the amplitude of oscillation is decayed to 0. This brings the reciprocating component into axial alignment, and sustained
pressure is applied to consolidate the joint as it cools.
Figure 1.58 shows examples of linear friction welds in
aluminum alloys.
FRICTION STIR WELDING
Friction stir welding (FSW) is a variation of friction
welding that produces a weld by the frictional heating
and displacement of the plastic material caused by a
rapidly rotating tool traversing the weld joint.27 This
variation is discussed in detail in Chapter 7, Friction
Stir Welding, Volume 3 of the Welding Handbook,
Welding Processes, Part 2.28
This variation is best known as a single-pass technique for welding materials approximately 1 mm to
75 mm (0.04 in. to 3 in.) thick and for the capability of
making continuous seam welds of excellent quality and
with high repeatability. This process can use a 2-pass
double sided welding technique which is typically used
when welding thicker materials. Although the initial
investment is very high, significant cost savings may
be realized when FSW is compared to other welding
processes.
In friction stir welding, a rotating, nonconsumable
tool (consisting of a shoulder and a probe) is plunged
into a joint line between two (or more) components, as
illustrated in Figure 1.59. The components (usually
plate or sheet materials) are clamped onto a backing
bar in a manner that prevents the abutting joint faces
from being forced apart. Friction between the rotating
tool and the workpieces generates heat, which softens
(but does not melt) the material around the tool. The
rotating FSW tool traverses the joint line, heating, soft27. Friction stir welding was invented in 1991 by Wayne Thomas
and developed by The Welding Institute (TWI) in Cambridge, United
Kingdom.
28. Refer to Chapter 7 in American Welding Society (AWS) Welding
Handbook Committee, 2007, Welding Handbook, vol. 3, Welding
Processes, Part 2, Miami: American Welding Society.
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
Figure 1.57—Heat for Welding Generated by
Lateral Reciprocation in Linear Friction Welding
Figure 1.58—Examples of Linear Friction Welding in Aluminum Alloy
105
106
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
Figure 1.59—Weld in Progress Under Rotating Tool of Friction Stir Welding
ening, and forging material as it moves. Softened material is transferred from the leading edge of the tool to
the trailing edge of the tool and is forged by the forces
generated, and contained under the shoulder of the
tool. A consolidated solid-phase joint is formed as the
tool moves along the joint.
The low heat input of friction stir welding makes this
technique appropriate for the joining of metals with
low melting points and high thermal conductivity; thus,
it is most often applied to aluminum alloys. All commonly known aluminum alloys in a wide range of
thicknesses and product forms can be joined by FSW, a
process variation that requires no special preweld edge
profiling or cleaning (in most cases) and does not
require shielding gas or filler metal. Workpiece shrinkage and distortion are reduced. In general, welds have
excellent mechanical properties, particularly fatigue
performance. Table 1.61 provides tensile properties of
base metals and friction stir welds for a number of commonly used aluminum alloys.
Some modes of FSW require specialized equipment
due to the relatively high levels of force generated.
Workpieces must be rigidly clamped (although FSW
tack welding can be used). Run-in and run-off weld
tabs are sometimes used, and a backing bar is usually
required (except when specially designed tools are
used). Fillet welds can only be made when specially
designed tools are employed.
OXYFUEL GAS WELDING
Oxyfuel gas welding (OFW) includes a group of
welding processes that produce coalescence of the
workpieces by heating them with an oxyfuel gas flame.
The processes are used with or without the application
of pressure and with or without filler metal.
PROCESS SELECTION
Aluminum can be welded by oxyfuel gas welding;
however, this process should be used only for noncritical or repair applications when suitable gas-shielded arc
welding equipment is not available.29
The advantages of using oxyfuel gas welding are simplicity, portability, and low cost of equipment, but there
are significant disadvantages when compared to arc
welding. The aluminum oxide on the surface melts at a
29. Refer to Chapter 11, Oxyfuel Gas Welding, in American Welding
Society (AWS) Welding Handbook Committee, 2004, Welding Processes, Part 1, ed. A. O’Brien, vol. 2, Welding Handbook, 9th ed.,
Miami: American Welding Society. See Appendix B of this volume for
a detailed description of chapter contents for the five volumes of
Welding Handbook, 9th ed.
T6
T73/T7451
T651
T73
6082
7050
7075
7075
393 (57)
503 (73)
434 (63)
262 (38)
N/A
276 (40)
303 (44)
145 (21)
207 (30)
241 (35)
117 (17)
145 (21)
N/A
345 (50)
414 (60)
474 (69)
572 (83)
496 (72)
310 (45)
N/A
310 (45)
365 (53)
276 (40)
276 (40)/
303 (44)
248 (36)
290 (42)
N/A
483 (70)
483 (70)
Ultimate
Tensile
Strength
MPa (ksi)
7
11
12
6
N/A
17
5
20
10
22
22
N/A
18
13
%
Elongation
N/A
334 (48.4)
444 (64.4)
150 (21.7)
119 (17.2)
161 (23.4)
265 (38.5)
191 (27.7)
119 (17.3)
101 (14.6)
132 (19.1)
253 (36.7)
308 (44.7)
243 (35.2)
Average
MPa (ksi)
N/A
16 (2.3)
63 (9.1)
10 (1.4)
23 (3.3)
48 (6.9)
46 (6.6)
40 (5.8)
8 (1.1)
8 (1.1)
7 (1)
10 (1.5)
34 (5)
25 (3.6)
Standard
Deviation
MPa (ksi)
Yield Strength
N/A
3
6
8
5
7
5
3
9
3
4
29
15
2
Number
of Data
Points
444 (64.4)
439 (63.6)
473 (68.6)
238 (34.6)
211 (30.6)
221 (32.1)
316 (45.9)
306 (44.4)
251 (36.4)
245 (35.5)
306 (44.4)
396 (57.5)
416 (60.4)
355 (51.4)
Average
MPa (ksi)
54 (7.8)
30 (4.3)
45 (6.5)
12 (1.7)
32 (4.6)
23 (3.3)
21 (3.1)
12 (1.8)
9 (1.3)
17 (2.4)
19 (2.8)
11 (1.6)
27 (3.9)
36 (5.2)
Standard
Deviation
MPa (ksi)
4
7
11
9
7
13
5
3
9
5
15
35
23
9
Number
of Data
Points
Ultimate Tensile Strength
N/A
5
6.5
10.2
14.5
10
6.4
4.8
19.6
18.9
22.5
8.5
7.8
N/A
Average
N/A
2.1
0.5
6.1
6.2
3.4
1.4
3.1
3.8
4.4
0.7
1.6
3.8
N/A
Standard
Deviation
% Elongation
N/A
3
6
8
5
7
3
3
9
5
2
33
14
N/A
Number
of Data
Points
*Typical properties of base metals are from ASM Metals Handbook, Materials Park, Ohio: ASM International. Properties of 6013 and 6075 are from Aluminum Standards and Data, 2006, Aluminum
Association. Properties of 6082-T6 are from ASTM B209, ASTM International.
Notes:
— The test configuration was in the transverse orientation.
— N/A = Not available for this table.
— Standard deviation normally applies only to Gaussian distributions and is applicable only for distributions with sample sizes greater than 8; however, standard deviations are included in this table
for small sample sizes to provide some indication of the distribution about the mean.
T6
T4
T6
6013
6082
T4
6013
6061
O
H32/H34
5454
O
5083
5454
T3
T8
2014
2195
T6
Alloy
2024
Original
Temper
Yield
Strength
MPa (ksi)
Base Metal—Typical Properties*
Friction Stir Welds—Sample Properties
Table 1.61
Test Data for Tensile Properties of Base Metals and Friction Stir Welds for Commonly Used Aluminum Alloys
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
107
108
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
much higher temperature than the aluminum. Coupled
with this, aluminum does not change color when the
melting temperature is reached. With the low rate of
heat input from oxyfuel gas, an unskilled operator may
melt a hole in the aluminum before the surface has
reached the molten state. The unmelted oxide on the
surface cannot support the molten metal, which falls
through the bottom of the section.
Other disadvantages of using OFW instead of an arc
welding process are that an active welding flux is
required to remove oxide and protect the molten aluminum from oxidation; welding speeds are slower; heataffected zones are wider; weld-metal solidification rates
are slower (which increases the possibility of hot cracking); the gas flame offers no surface cleaning action; distortion of the weldment is greater; and the welding flux
must be completely removed. However, when oxyfuel
gas welding is the selected process, the welding conditions noted in the next section can be used. Table 1.62
provides suggested schedules for welding aluminum
with the oxyfuel gas flame.
Equipment
Standard oxyfuel gas welding torches are suitable for
welding aluminum sections about 0.76 mm to 25 mm
(0.03 in. to 1 in.) thick. Thicker sections are seldom
welded with OFW because good fusion is difficult with
the limited heat available from the oxyfuel gas flame.
Fuel Gases
Acetylene is the most commonly used fuel for oxyfuel gas welding of aluminum because of the high combustion intensity and flame temperature it provides. A
slightly reducing flame (excess acetylene) is used to
lessen the possibility of forming unwanted aluminum
oxides. This produces a carbonaceous deposit which
obscures the weld pool and requires a highly skilled
welder to manipulate the filler metal.
Hydrogen is preferred over acetylene fuel for welding
aluminum. Hydrogen is used with a neutral flame; it
produces good visibility of the weld and is the easiest
fuel to use. A larger tip is used for oxyhydrogen welding
than for oxyacetylene to compensate for the lower
intensity.
Welding Flux
Flux for welding aluminum is designed to remove the
aluminum-oxide surface film and also to exclude oxygen
from the weld pool. Flux is generally available in powder
form and mixed with water to form a thin, free-flowing
paste. The filler metal should be uniformly coated with
the flux mixture either by dipping or painting; the joint
faces and adjacent surfaces should be coated with flux to
prevent oxidation of these surfaces during welding.
Flux residues are corrosive to aluminum when moisture is present; thus thorough cleaning after welding is
of prime importance. Weldments or assemblies of small
Table 1.62
Suggested Schedules for Oxyfuel Gas Welding of Aluminum
Oxyhydrogen
Metal Thickness
Diameter of
Orifice in Tip
Oxygen
Pressure
Oxyacetylene
Hydrogen
Pressure
Diameter of
Orifice in Tip
Oxygen
Pressure
Acetylene
Pressure
mm
in.
mm
in.
kPa
psi
kPa
psi
mm
in.
kPa
psi
kPa
psi
0.51
0.020
0.89
0.035
6.9
1
6.9
1
0.63
0.025
6.9
1
6.9
1
0.81
0.032
1.14
0.045
6.9
1
6.9
1
0.89
0.035
6.9
1
6.9
1
1.30
0.051
1.65
0.065
13.8
2
6.9
1
1.14
0.045
13.8
2
13.8
2
2.06
0.081
1.91
0.075
13.8
2
6.9
1
1.40
0.055
20.7
3
20.7
3
3.17
0.125
2.41
0.095
20.7
3
13.8
2
1.65
0.065
27.6
4
27.6
4
6.35
0.250
2.67
0.105
27.6
4
13.8
2
1.91
0.075
34.5
5
34.5
5
7.92
0.312
2.92
0.115
27.6
4
13.8
2
2.16
0.085
34.5
5
34.5
5
9.52
0.375
3.17
0.125
34.5
5
20.7
3
2.41
0.095
41.4
6
41.4
6
15.87
0.625
3.81
0.150
55.2
8
41.4
6
2.67
0.105
48.3
7
48.3
7
AWS WELDING HANDBOOK
parts may be cleaned by immersion in an acid-base
cleaning solution. One of the following solutions may
be used:
1. 10% sulfuric acid at room temperature for 20
minutes to 30 minutes,
2. 5% sulfuric acid at 66°C (150°F) for 5 minutes
to 10 minutes, or
3. 40% to 50% nitric acid at room temperature
for 10 minutes to 20 minutes.
The application of an acid-base cleaner should be
followed by a hot-water rinse and then a cold-water
rinse. All acids used in cleaning solutions are potentially
hazardous. Personnel using them should be
thoroughly familiar with these chemicals and should
use appropriate safety equipment and personal protective
equipment (PPE). Instructions from the safety data sheet
(SDS) supplied by the manufacturer should be carefully
followed.
Steam cleaning may be used to remove flux residue,
particularly on workpieces that cannot be immersed.
Joint Designs
Joint designs for OFW are the same as those for
GTAW (refer to Figure 1.11 and Figure 1.12). For sections more than 4.5 mm (0.18 in.) thick, complete joint
penetration is best achieved by beveling the edges to be
joined. Single V-groove joints are sometimes used on
plate up to approximately 12.7 mm (0.5 in.) thick. Permanent backings are not recommended for oxyfuel gas
welding due to the possibility of entrapping welding
flux and the probability of subsequent corrosion. Partial joint penetration groove weld joints should not be
welded where flux entrapment could be possible. Filletwelded lap joints generally are not recommended for
the same reason.
Preweld Cleaning
Grease and oil should be removed from the welding
surfaces with a safe solvent. Fluxes will perform better
if thick oxide layers are removed from the surfaces
prior to welding.
Filler Metals
Bare filler rods ER1100, ER4043, ER4047, and
ER4145 can be used for oxyfuel gas welding.30 Covered
30. American Welding Society (AWS) Committee on Filler Metals
and Allied Materials, 2012, Specification for Bare Aluminum and
Aluminum-Alloy Welding Electrodes and Rods, ANSI/AWS A5.10/
A5.10M:2012 (ISO 18273:2004 MOD), Miami: American Welding
Society.
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
109
electrodes E1100, E3003, and E4043 can also be
used.31 Although the welding of alloys in the 5XXX
series is not recommended because of poor wetting
characteristics, thin sections containing no more than
2.5% magnesium may be welded with a single pass.
The proper choice of filler metal depends on the alloy
being used and the service requirements.
The size of the filler metal rod is related to the thickness of the workpieces. A large rod may melt too slowly
and tend to solidify the weld pool prematurely. A small
rod may melt too rapidly and make it difficult to add
filler metal into the weld pool.
Preheating
Preheating is necessary when the mass of base metal
is so great that the heat is conducted away from the
joint too fast to accomplish welding. Preheating will
also improve control of the weld pool.
Welding Technique
Initially, the flame is moved in a circular motion to
preheat both edges of the joint uniformly. The flame is
then moved to the point where the weld will begin and
then held until a small weld pool forms. The forehand
technique is used, in which the end of the filler rod is
fed into the weld pool to deposit a drop of metal and is
then withdrawn, leaving a weld bead. This technique is
repeated as welding progresses. The flame should be
oscillated so that it melts both joint faces simultaneously. The inner flame cone should be kept 1.6 mm to
6.4 mm (0.062 in. to 0.25 in.) away from the weld pool
and should not touch it. The crater should be filled
before removing the flame.
WELDING ALUMINUM CASTINGS
Welding is sometimes used to correct foundry
defects, to repair castings damaged in service, or to
assemble castings into weldments. (Refer to Table 1.13,
Table 1.14, Table 1.15, Table 1.16, Table 1.17, Table
1.18, Table 1.19, and Table 1.20 for the nominal compositions, weldability, and physical and mechanical
properties of various casting alloys.)
Standard filler metals for casting alloys are listed in
Table 1.63. Sand-mold and permanent-mold castings can
31. American Welding Society (AWS) Committee on Filler Metals
and Allied Materials, 2007, Specification for Aluminum and Aluminum-Alloy Electrodes for Shielded Metal Arc Welding, AWS A5.3/
A5.3M:1999(R2007), Miami: American Welding Society.
110
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
Table 1.63
Composition of Standard Filler Metals for Welding and Repair of Aluminum Castings, wt %a
Other Elements
Filler
Alloy
Si
Fe
Cu
Mn
Mg
Ni
Zn
Ti
Each
Total
Al
206.0
0.10
0.15
4.2–5.0
0.20–0.50
0.15–0.35
0.05
0.10
0.15–0.30
0.05
0.15
Remainder
C355.0
4.5–5.5
0.20
1.0–1.5
0.10
0.40–0.6
—
0.10
0.20
0.05
0.15
Remainder
4009b
4.5–5.5
0.20
1.0–1.5
0.10
0.45–0.6
—
0.10
0.20
0.05b
0.15
Remainder
A356.0
6.5–7.5
0.20
0.20
0.10
0.25–0.45
—
0.10
0.20
0.05
0.15
Remainder
4010b
6.5–7.5
0.20
0.20
0.10
0.30–0.45
—
0.10
0.20
0.05b
0.15
Remainder
357.0
6.5–7.5
0.15
0.05
0.03
0.45–0.6
—
0.05
0.20
0.05
0.15
Remainder
A357.0c
6.5–7.5
0.20
0.20
0.10
0.40–0.7
—
0.10
0.04–0.20
0.05c
0.15
Remainder
0.04–0.20
0.05c
0.15
Remainder
4011c
6.5–7.5
0.20
0.20
0.10
0.45–0.7
—
0.10
a. Single values are maximum, except when otherwise specified.
b. Beryllium shall not exceed 0.0008%.
c. Beryllium content shall be 0.04% to 0.07%.
be welded in a manner similar to that of wrought aluminum alloys; weldability is based primarily on the chemical composition and melting range of the casting alloy.
Die castings tend to contain gassy elements due to the
entrapment of die lubricants; thus, welds that penetrate
the surface layer of these materials will be extremely
porous. Vacuum-die castings can have very sound internal structures and have been welded satisfactorily.
When repairing newly made castings in the foundry,
a filler metal of the same alloy is used to provide a
homogeneous structure. If a filler metal with the same
composition as the casting is not available, the foundry
can cast a matching filler metal. New castings are clean,
so it is usually necessary only to remove any sand or
other surface contaminants before repair welding. Internal defects, determined by radiography, need to be
gouged out by chipping or with manual routers or
deburring tools to permit penetration of the weld into
sound metal.
Gas tungsten arc welding is commonly used to repair
new castings. Alternating current (ac) is commonly used
to repair sections that are 4.8 mm (0.188 in.) and thinner. Direct current electrode negative (DCEN) is often
preferred for thicker sections to minimize preheating
requirements.
Repair welding of castings that have been in service
requires different consideration. These castings have
usually been exposed to oil, grease, or other contaminants and must be thoroughly cleaned before welding.
Also, a filler metal of the same composition as the
workpiece may not be available. In such circumstances,
it is often acceptable to use another standard filler alloy
(refer to Table 1.63 for standard filler metals for cast
aluminum).
Typical tensile strengths of groove welds in casting
alloys are presented in Table 1.64. The heat-treatable
casting alloys will exhibit a partial loss of mechanical
properties from the heat of welding in the same manner
as that of the wrought alloys. By selecting a proper filler
metal (one that responds to subsequent heat treatment),
Table 1.64
Typical As-Welded Tensile Strength of
Gas Metal Arc Welds in Aluminum Castings
Ultimate Tensile Strength
Base Alloy
Filler Alloy
MPa
ksi
208.0-F
4043
138
20
295.0-T6
2319
224
32.5
22.2
354.0-T4, -T61, -T62
4043, 4047
153
356.0-T6, -T7, -T71
4043
186
27
A356.0-T6, -T61
4043
186
27
443.0-F
4043
124
18
A444.0-F
4043
169
24.5
514.0-F
5654
170
25
520.0-T4
5356
170
25
535.0-F
5356, 5556
196
37
710.0-F
5356
193
34
AWS WELDING HANDBOOK
these heat-treatable alloys can be postweld heat-treated
to restore the original heat-treated properties.
When joining an assembly that requires welding an
aluminum casting to a wrought aluminum alloy, it
should be noted that the strength of the weldment will
be controlled by the heat-affected zone that has the
lower-strength of the two workpieces. If heat-treatable
alloys are joined and postweld heat treatment is
planned, the compatibility of the solution-heat-treatment and artificial aging practices is an important consideration in the selection of the cast and wrought
alloys. The selection of filler metal for a cast-towrought alloy weldment is usually a compromise, and
each case requires specific consideration.
For highest strengths and greatest ductility, castings
with a high silicon content should be welded with an
aluminum-silicon filler alloy, such as Alloy 4043. Cast
or wrought alloys with a high magnesium content
should be welded with an aluminum-magnesium filler
metal, such as Alloy 5356. Mixing large amounts of
magnesium and silicon in the weld metal will result in
the formation of large quantities of brittle magnesiumsilicide, which increases susceptibility to weld cracking
and may affect corrosion resistance.
Welding a high-silicon-content casting alloy (e.g.,
356.0) to a high-magnesium-content wrought alloy
(e.g., 5083) should be avoided. Whether 4XXX or
5XXX series filler metal is selected, the magnesium-silicide problem will occur in one of the weld transition
zones. The best overall performance is provided by joining a 5XXX series wrought alloy to a 5XX.X series
casting alloy. The 3XX.X and 4XX.X casting alloys can
be joined to wrought alloys in the 1XXX, 2XXX,
3XXX, 4XXX, and 6XXX series with a filler metal
from 4XXX series.
When welding thick sections to thin sections, thermal strains may result in cracking or distortion. It may
be necessary to preheat the casting for welding. The
temperature will depend on the casting shape, alloy,
and prior heat treatment, but it is generally between
20°C and 480°C (390°F and 900°F). The properties of
the -T6 temper will be affected by temperatures up
to 316°C (600°F), but little loss will be incurred for
the -T5 and -T7 tempers. When the temperature is
greater than 316°C (600°F), all alloys become annealed
and postweld heat treatment is necessary to restore
properties.
BRAZING
Brazing includes a group of joining processes that
produce the bonding of materials by heating them to
the brazing temperature in the presence of a brazing
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
111
filler metal that has a liquidus above 450°C (840°F) and
below the solidus of the base metal. The brazing filler
metal is distributed and retained between the closely fitted faying surfaces of the joint by capillary action.32
BRAZING ALLOYS
Many aluminum alloys can be brazed with commercially available filler metals.33 The alloy may be a casting or a wrought product, heat treatable or nonheat
treatable. (Refer to Table 1.4, Table 1.9, Table 1.15,
and Table 1.18 for aluminum alloys that are rated for
brazeability.) All of the alloys in the 1XXX and 3XXX
series can be brazed, and also alloys in the 5XXX series
that contain less than 2% magnesium. The 5XXX series
high-magnesium alloys are difficult to braze because of
poor wetting characteristics and melting points that are
below those of available filler metals, which result in
poor joint properties.
Alloys in the 6XXX series are the easiest of the heattreatable alloys to braze. Alloys in the 2XXX series and
most of the 7XXX series cannot be brazed because the
melting temperatures of these alloys are below those of
commercially available filler metals.
Casting alloys that can be brazed include 356.0,
357.0, 359.0, 443.0, and 712.0. High-quality castings
are as easy to braze as the equivalent wrought alloys.
Problems arise when the casting quality is low and the
metal is porous. Die castings are difficult to braze.
Filler Metals
Commercial brazing filler metals used for aluminum
are described in Table 1.65.34 They are all based on the
aluminum-silicon eutectic. Increasing the silicon
decreases the liquidus temperature until the eutectic
composition (12% silicon) is reached at 577°C
(1070°F). The addition of 4% copper, as in BAlSi-3,
lowers the solidus temperature to the point that this
alloy can be used to braze aluminum-silicon casting
alloys.
32. For more information, refer to American Welding Society (AWS)
3.7 Committee on Brazing and Soldering, 2005, Specification for Aluminum Brazing, Miami: American Welding Society.
33. Refer to Chapter 12 of American Welding Society (AWS) Welding Handbook Committee, 2004, Welding Processes, Part 1, ed. A.
O’Brien, vol. 2, Welding Handbook, 9th ed., Miami: American Welding Society. See also American Welding Society (AWS) Committee on
Brazing and Soldering, 2007, Brazing Handbook, 5th ed., Miami:
American Welding Society. See Appendix B of this volume for detailed
description of chapter contents for the five volumes of Welding Handbook, 9th ed.
34. Refer to American Welding Society (AWS) Committee on Filler
Metals and Allied Materials, 2011, Specification for Filler Metals for
Brazing and Braze Welding, A5.8M/A5.8:2011, Miami: American
Welding Society.
112
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
Table 1.65
Filler Metals for Aluminum Brazing
Nominal
Composition,%b
Melting Range
Brazing Range
Applicable
Brazing
Processesd
Classa
Designation
Si
Mg
°C
°F
°C
°F
Standard
Formsc
BAlSi-2
4343
7.5
—
577–617
1070–1142
599–621
1110–1150
C
D, F
BAlSi-3e
4145
10
—
521–585
970–1085
571–604
1060–1120
R
D, F, T
BAlSi-4
4047
12
—
577–582
1070–1080
582–604
1080–1120
P, R, S
D, F, T
BAlSi-5
4045
10
—
577–599
1070–1110
588–604
1090–1120
C
D, F
BAlSi-7
4004
10
1.5
559–596
1038–1105
588–604
1090–1120
C
Vf
BAlSi-9
4147
12
0.3
562–582
1044–1080f
582–604
1080–1120
C
Vf
BAlSi-11g
4104
10
1.5
559–596
1038–1105f
588–604
1090–1120
C
Vf
—
577–602
1070–1115f
593–613
1100–1135
C
D, F
—
a.
b.
c.
d.
e.
f.
g.
4044
8.5
See AWS A5.8/A5.8M:2004, Specification for Filler Metals for Brazing and Braze Welding.
Remainder Al.
C—cladding on sheet; P—powder; R—rod or wire; S—sheet or foil.
D—dip; F—furnace; T—torch; Vf—vacuum furnace.
Also contains 4% Cu.
Melting range in air. Melting range in vacuum is different.
Also contains 0.1% Bi.
Filler metals are available in the form of wire, rod,
foil, shim, powder, or paste. Powdered filler metal products typically contain brazing flux and a binder for
forming a paste; premixed paste for torch brazing applications contains flux.
In some cases, filler metal is applied as cladding to
one or both sides of an aluminum core (substrate) sheet
or substrate. This product is known as brazing sheet
and can be formed and worked by conventional means.
It is widely used for assemblies that are furnace brazed
or dip brazed. Table 1.66 describes common types of
aluminum brazing sheet. Sheets clad with BAlSi-7,
BAlSi-9, or BAlSi-11 filler metal are designed for vacuum brazing applications.
Brazing Fluxes
Chemical fluxes are required for conventional aluminum brazing operations, but not for vacuum brazing.
Magnesium is used as an oxide modifier to remove
excess free oxygen in vacuum brazing or inert-gas brazing without salt fluxes.
Aluminum brazing fluxes are mixtures of fluoride
and chloride inorganic salts. They are available as a dry
powder. For torch brazing and furnace brazing, the flux
is mixed with water or alcohol to make a paste. The
paste, or slurry, is brushed, sprayed, dipped, or flowed
onto the entire joint area, including preplaced filler
Table 1.66
Aluminum Brazing Sheeta
Designation No.
No. of
Sides Clad
Core Alloy
Cladding Alloy
3003
BAlSi-7
3003
BAlSi-2
6951
BAlSi-7
6951
BAlSi-2
6951
BAlSi-5
6951
4044
6951
4044
7
1
8
2
11
1
12
2
13
1
14
2
21
1
22
2
23
1
24
2
33
1
34
2
44b
2
7072
—
1 or 2
3003
BAlSi-9
—
1 or 2
3105
BAlSi-11c
a. Not all designations are allowable as commercial products.
b. One side is clad with 7072 alloy for corrosion resistance.
c. Maximum brazing temperature is 593°C (1110°F).
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
metal. Fluxes are hygroscopic and will absorb water
from the atmosphere if left in unsealed containers.
In dip brazing, the hot bath consists of molten flux.
The bath remains stable and active for months or years
with only moderate maintenance requirements.
A flux made of complex fluoride salts is available
for torch and furnace brazing. The flux residuals are
not water soluble and are therefore not corrosive to
aluminum.
Removal of Flux Residue
Corrosive flux residue must be removed after brazing. The most effective method is soaking in hot agitated water 80°C to 95°C (180°F to 200°F). For some
fluxes, a chemical cleaning may be required after hotwater soaking.
Immersion in hot water before the brazement has
cooled is effective for removing a major portion of the
flux. The assembly should be allowed to cool to prevent
distortion by thermal shock. The hot-water soak will
then remove virtually all of the flux residues. Mechanical cleaning, such as wire brushing or grinding, is not
adequate. It breaks up the residue into fine particles
that may become embedded in the aluminum surface.
Scrubbing with a fiber brush under hot, running water
is an effective practice.
Final traces of residues can be removed chemically.
Acceptable solutions for this are provided in Table
1.67. A number of commercial proprietary cleaners also
are available for this purpose. All methods require a
113
thorough final rinse in clean water to remove the cleaning agent.
It should be recognized that all acids used in cleaning
solutions have the potential to be extremely hazardous.
Personnel using them should be thoroughly familiar
with all chemicals involved and adequate safety equipment should be used. Hydrofluoric acid is highly corrosive and can cause severe tissue damage, which can lead
to cardiac arrest. Always use proper personal protective
equipment, including chemical splash goggles, face
shield, neoprene (or other impervious material) gloves
and acid resistant clothing. Seek immediate medical
attention if exposed. Information on the safety data
sheet (SDS) from the manufacturer should be carefully
followed. Acids must be properly stored in accordance
with the SDS and should only be used under a fume
hood.
A silver nitrate test is used to check for remaining
flux residue. The brazed assembly or joint is soaked in a
minimal amount of distilled or deionized water. Heating the water increases the accuracy of the test. A small
sample of the water is tested for chlorides by adding
several drops of a 5% silver nitrate solution. A white
precipitate indicates the presence of residue, and cleaning should be repeated.
An alternate method is to place a few drops of distilled water on the joint area. After one minute, the
water is collected and dropped into a 5% silver nitrate
solution. An emitted white cloud indicates flux residue
is present.
Table 1.67
Chemical Solutions for Removing Brazing Flux Residue from Aluminum
Solution
Compositiona
Bath Temperature
Procedureb
Nitric acid
3.8 L (1 gal) HNO 3,
26.5 L (7 gal) water
Ambient
Immerse 10 to 20 minutes, rinse in hot or
cold water.c
Nitric-hydrofluoric acid mixture
3.8 L (1 gal) HNO3
0.23 L (0.06 gal) HF
37.8 L (10 gal) water
Ambient
Immerse for 5 minutes, rinse in cold and hot
water.d
Hydrofluoric acid
0.3 gal (1.14 L) HF
37.8 L (10 gal) water
Ambient
Immerse for 2 to 5 minutes, rinse in cold
water, immerse in nitric acid solution, rinse in
hot or cold water.
Phosphoric acid-chromium trioxide
mixture
1.5 L (0.4 gal) 85% H3PO4
1.8 lb (0.82 kg) CrO3
10 gal (37.8 L) water
82°C (180°F)
Immerse for 10 to 15 minutes, rinse in hot or
cold water.e
a. Acids are concentrated technical grades.
b. In all cases, remove the major portion of flux residue with a hot-water rinse. To check for flux residue, place a few drops of distilled water on the area. After
1 minute, collect the water and drop it into a 5% silver nitrate solution. A white precipitate indicates the presence of residue, and cleaning should be repeated.
c. Chloride concentration should not exceed 5 g/L (0.68 oz/gal). Not recommended for sections less than 0.5 mm (0.020 in.) thick.
d. Chloride concentration should not exceed 3g/L (0.40 oz/gal). Not recommended for sections less than 0.5 mm (0.020 in.) thick.
e. Chloride concentration should not exceed 100 g/L (13.4 oz/gal). Suitable for thin sections.
114
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
BRAZING PROCESSES
Aluminum can be brazed with the use of torch brazing (TB), dip brazing (DB), furnace brazing (FB), or
induction brazing (IB). Brazing of aluminum that takes
place in a chamber or retort below atmospheric pressure in a vacuum is a fluxless process, whereas furnace
brazing is usually done with conventional salt fluxes.
Several specialized processes exist, but the majority of
aluminum assemblies are brazed using these processes.
An application of aluminum brazing is shown in Figure 1.60, a multiple-torch system brazing an evaporator
coil.
Joint Designs for Brazing
Many brazing applications require the use of flux
and filler metal. The preferred joint design for such
brazing is the lap joint. The basic, square butt joint used
in some welding applications does not function well for
brazing because it does not accommodate the flow of
flux and filler metal. Also, the required joint spacing is
difficult to maintain. Lap joint spacing produces a
capillary effect, which draws the molten brazing filler
AWS WELDING HANDBOOK
metal into the joint clearance. The amount of overlap
required to obtain full-strength joints is usually about
3 × T (where T equals the workpiece thickness).
The strength of the joint varies inversely with the
joint clearance. To obtain capillary action with torch,
furnace, induction, or dip brazing, and thus adequate
strength, the joint thickness usually should be 0.05 mm
to 0.10 mm (0.002 in. to 0.004 in.) with a 3T lap. If the
joint thickness exceeds 0.25 mm (0.010 in.), capillary
action is limited, which results in low joint strength. If
the amount of lap exceeds 6.35 mm (0.25 in.), a greater
joint clearance may be required. As the brazing alloy
flows through increased lap distances, there may be a
pickup of alloys as mutual diffusion occurs between the
base and filler metals. This can increase filler metal viscosity. In this case, the joint clearance is increased so
that the joint can be completely filled even though the
fluidity of the filler metal has been somewhat decreased.
The amount of increase in the joint clearance may have
to be determined by trial.
In fluxless brazing, the workpieces must be in close
contact with one another throughout the brazing operation. This is accomplished by tightly fitting or press-fitting them together.
Photograph courtesy of Belman Melcor, LLC
Figure 1.60—Brazing of an Aluminum Evaporator Coil
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
Figure 1.61 illustrates 16 joint designs that are typical of those suitable for brazing aluminum and aluminum alloys. The selected joint design should facilitate
easy assembly and inspection. When possible, the workpieces should be self-positioning. Figure 1.62 shows
designs which include self-positioning features. The
joint should be designed to avoid unvented pockets in
the assembly where pressure could build when the brazing heat is applied. Such pressure could cause the braze-
115
ment to become misaligned, which could prevent a
leak-tight joint from developing.
Fixturing devices to hold the workpieces in the preferred orientation can lower the cost of manufacturing
for high-volume production. The fixture may include
loading features that will decrease the joint clearance as
the flux and brazing alloy are brought to the flowing
temperature. Decreasing joint thickness increases joint
strength and increases joint-filling integrity.
T-JOINT
LAP
CORNER
SINGLE STRAP BUTT
ANGLE T-JOINT
DOUBLE LAP
CORNER
FLANGED BUTT
FLANGED T-JOINT
FLUSH LAP
FLANGED CORNER
LINE CONTACT
FLANGED EDGE
FLAT LOCK SEAM
FLANGED BOTTOM
FLANGED BOTTOM
Figure 1.61—Recommended Joint Designs for Brazing Aluminum Alloys
116
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
SPOT
WELDED
MECHANICALLY
EXPANDED
HYDRAUICALLY
EXPANDED
LOCK SEAMED
(A)
(B)
AWS WELDING HANDBOOK
PRESSED
STAKED
CLIPPED
(A)
COUNTERSUNK AND SPUN
(A)
FORMED
(B)
PRESSED
CRIMPED
(B)
SWAGED
(C)
PEENED
(A)
(B)
SLITTING AND EARING
Figure 1.62—Typical Self-Positioning Joints for Aluminum Alloys
The selection of material used for fixturing is important, especially when flux is used. Flux can inadvertently come in contact with the fixture and can react
with the fixture materials; therefore it is important
either to design the fixture so that the flux cannot come
in contact with it or use materials that will not react.
Stainless steel or protectively coated carbon steel are
commonly used in fixture construction. The design of
the fixture must be rigid enough so that it does not
cause misalignment or movement of the brazement
when heat is applied.
Surface Preparation
Degreasing the aluminum surface is recommended
prior to brazing. Degreasing usually is adequate preparation for fluxless brazing and when flux is used for
nonheat-treatable alloys, because contamination and
oxide film formation are minor concerns in these applications. A vaporizing solvent is recommended for
degreasing when cleaning thin sections, such as the
components used in heat exchangers.
Light etching is a permissible treatment to prepare
thin-gauge clad aluminum for brazing, but care must be
exercised to prevent removing an excessive amount of
cladding.
Chemical cleaning is usually a necessary supplement
to degreasing to remove the thicker oxide film on the
surface of heat-treatable alloys. Metalworking operations, even manual hammering, can embed oxides
into the surface. The fluidity of filler metals in the form
of wire or sheet can be enhanced by light etching,
mechanical abrasion, or chemical cleaning before
preplacement.
AWS WELDING HANDBOOK
A caustic or nitric-hydrofluoric acid solution can be
effective in chemically cleaning the heavy oxides from
the surface. Caustic cleaning is capable of removing
thick aluminum-oxide layers. Several effective proprietary cleaning solutions are available. The procedure
for caustic cleaning is:
1. Degreasing,
2. Dipping for 60 seconds into 5% (wt %) sodium
hydroxide 60°C (at 140°F),
3. Rinsing with tap water at ambient temperature,
4. Dipping for 10 seconds in 50% (vol %) nitric
acid at room temperature, and
5. Rinsing in hot or cold water and drying.
The procedure for acid cleaning is as follows:
1. Degreasing,
2. Dipping for 5 minutes in a solution of 10%
(vol %) nitric acid and 0.25% (vol %)
hydrofluoric acid at room temperature, and
3. Rinsing in hot or cold water and drying.
The purity of the rinse water used may be a consideration. Tap water purity varies with geographic location.
The demands of the brazing application and the purity of
the tap water are the deciding factors of whether a water
filtering operation or special water may be necessary.
Acids used in cleaning solutions are potentially
hazardous. Personnel using them should be
thoroughly familiar with these chemicals and should
use appropriate safety equipment and personal protective
equipment (PPE). Instructions from the safety data sheet
(SDS) supplied by the manufacturer should be carefully
Joint Properties
Because the brazing temperatures of aluminum are
much closer to the melting temperature than those of
most other base metals, it is important to carefully control the brazing temperature (usually within 3°C [5°F]
for furnace brazing and dip brazing) and also the time
at that temperature.
If the upper limit of one or both of these conditions
is exceeded, or if an excessive amount of diffusion
results, melting or incipient melting may occur at the
grain boundaries, resulting in deleterious grain-structure changes and decreased corrosion resistance. In
addition, annealing will occur at brazing temperatures.
When the brazement is a nonheat-treatable alloy, it will
assume the mechanical properties of the annealed temper of the alloy. For heat-treatable aluminum alloys,
strength and resistance to corrosion can be improved by
post-braze heat treating and quenching from the brazing temperature.
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
117
The complex geometry of a brazement may preclude
quenching from the brazing temperature because the resulting
dimensional changes could cause the newly formed
joints to fail. Complex brazements should be allowed to
cool before performing post-braze heat treatment.
Solidification of the brazed joint must take place
before quenching to prevent rupturing. When quenching
from the brazing temperature is permissible, quenching
can be accomplished by one of the following methods:
1. Spraying with water,
2. Immersing in a tank of hot or cold water, or
3. Blasting with cold air (the slowest of these
quenching methods).
The corrosion resistance of a brazement depends on
the grain structure after brazing and the thoroughness
of flux residue removal. If the cleaning operation does
not remove all flux residue, the combination of residual
flux and moisture may result in corrosion of the joint.
SOLDERING
Soldering includes a group of joining processes in
which the workpiece(s) and soldering filler metal are
heated to the soldering temperature to form a joint.35
Although aluminum and many aluminum-base alloys
can be soldered by techniques similar to those used for
other metals, problems can arise if insufficient consideration is given to the application involved.36 Reaction
soldering (in which a reactive flux is used) and abrasion
soldering (in which wetting is enhanced by abrading the
faying surfaces) are more frequently used with aluminum than with other metals. The soldering of aluminum requires special fluxes. Rosin fluxes are unsuitable
for removing surface oxides.
Refer to the Safe Practices section of this chapter for
information on fume removal and the safe handling of
chemicals used in soldering processes.
SOLDERABLE ALUMINUM ALLOYS
The most commonly soldered aluminum alloys usually contain less than 1% magnesium or less than 5%
silicon. The magnesium in aluminum alloys forms a
35. Vianco, P. T., 1999, Soldering Handbook, 3rd ed., Miami: American Welding Society.
36. Refer to Chapter 13 in American Welding Society (AWS) Welding Handbook Committee, 2004, Welding Processes, Part 1, ed. A.
O’Brien, vol. 2, Welding Handbook, 9th ed., Miami: American Welding Society. See Appendix B of this volume for a detailed description
of chapter contents for the five volumes of Welding Handbook,
9th ed.
118
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
tenacious oxide on the surface that results in poor wetting and flowing characteristics of the soldering filler
metal. Rapid penetration of the filler metal in these
alloys can result in loss of mechanical properties. Aluminum casting alloys usually are not easily soldered
because of composition, and also because the surface
condition of castings makes them more difficult to solder than wrought alloys. Oxide removal and cleaning of
castings is more difficult, and surface porosity can
result in incomplete flux removal.
Residual stresses from quenching or cold working
may interfere with forming a satisfactory soldered joint.
Stress accelerates the penetration of soldering filler metal
along grain boundaries and causes cracking or degradation of mechanical properties. Intergranular penetration
of the filler metal can be minimized by relieving stress
through heating, although this occurs naturally when
soldering with high-temperature zinc filler metals.
Clad aluminum alloys often exhibit improved soldering characteristics when compared to the bare alloys.
Cladding can improve flux wetting and soldering filler
metal wetting properties and can reduce the diffusion of
filler metal into the alloy. These properties are especially
useful when soldering alloys in the 2XXX to 7XXX
series at low temperatures. In addition to aluminum
cladding on aluminum alloys, other metals such as copper, brass, nickel, zinc, or silver can be applied to the
aluminum surface to facilitate soldering. Copper, in particular, can be electroplated or rolled onto the aluminum
to permit low-temperature soldering with filler metals
and fluxes typically used with copper. Copper-clad aluminum wire is used in many electrical applications.
SOLDERING FILLER METALS FOR
ALUMINUM
Soldering filler metals for aluminum can be classified
into three types, according to the melting ranges. Melting
temperatures, composition, and other properties of aluminum soldering filler metals are compared in Table 1.68.
AWS WELDING HANDBOOK
Low-Temperature Filler Metals
The melting points of low-temperature soldering
filler metals are in the range of 150°C to 260°C (300°F
to 500°F). These filler metals contain lead or tin, or
both, with small additions of zinc, cadmium, or bismuth.
The addition of these elements increases corrosion resistance of soldered joints. A tin-zinc filler metal has more
corrosion resistance than a lead-tin filler metal.
The low-temperature filler metals produce joints
with the least corrosion resistance, but they are the easiest to use in soldering operations. The mechanical
strength of low-temperature soldered joints approaches
that of soldered joints in copper, which exhibit shear
strength of about 41 MPa (6 ksi).
Intermediate-Temperature Filler Metals
The melting points of intermediate-temperature soldering filler metals are in the range of 260°C to 370°C
(500°F to 700°F). These filler metals contain tin or cadmium in combination with zinc. Additions of copper,
lead, nickel, silver, and sometimes aluminum are made
to improve various properties of the soldering filler
metals. Among the most commonly used of the intermediate-temperature filler metals are the 70% tin-30%
zinc and the 60% zinc-40% cadmium. Because of the
higher zinc content, these filler metals generally wet aluminum readily and produce stronger and more corrosion-resistant joints than the low-temperature types.
High-Temperature Filler Metals
The melting points of high-temperature soldering
filler metals are in the range of 370°C to 430°C (700°F
to 800°F). These zinc-base filler metals contain up to
10% aluminum. Small amounts of other metals, such as
copper, cadmium, iron, and nickel are sometimes added
to modify melting and wetting characteristics. Of the
aluminum soldering filler metals, the high-zinc filler
metals have the highest strength (with shear strengths in
Table 1.68
General Characteristics of Aluminum Soldering Filler Metals
Type
Melting Range
Common Constituents
Low temperature
149°C to 260°C
(300°F to 500°F)
260°C to 371°C
(500°F to 700°F)
371°C to 430°C
(700°F to 800°F)
Tin or lead base plus zinc,
cadmium, or both
Zinc-cadmium or zinc-tin
base
Zinc base plus aluminum,
copper, cadmium
Intermediate
temperature
High temperature
Relative
Corrosion
Resistance
Ease of
Application
Wetting of
Aluminum
Relative
Strength
Best
Poor to Fair
Low
Low
Moderate
Good to
Excellent
Good to
Excellent
Moderate
Moderate
High
Good
Most Difficult
AWS WELDING HANDBOOK
excess of 100 MPa [15 ksi]). These filler metals are
usually the least expensive and exhibit the greatest corrosion resistance.
SOLDERING FLUXES
The most widely used method of removing aluminum-oxide films is to apply a flux. Commercially available fluxes are classified as organic types and reaction
types, as described in this section.
Organic Fluxes
Organic fluxes are usually viscous materials ranging
in color from pale yellow to brown. These fluxes are
typically used with low-temperature soldering filler
metals and will deteriorate rapidly at temperatures
higher than 260°C (500°F). Overheating organic fluxes
should be carefully avoided; when this happens they will
carbonize and inhibit, rather than promote, soldering.
Most organic flux residues are mildly corrosive and
should be removed from workpieces that are thinner
than 0.13 mm (0.005 in.). Alcohols are effective in
removing organic flux residues. Some modified fluxes
contain zinc and ammonia compounds; the residues of
these fluxes are significantly more corrosive than those
of the unmodified fluxes and should be removed.
Flux residues are electrically conductive in the presence of moisture and should be removed from soldered
electrical joints.
Reaction Fluxes
The major component of the reaction fluxes is zinc
chloride. Compositions of these fluxes vary according to
the application. Fluxes for furnace or automatic flame soldering, in which the soldering filler metal is preplaced, contain a high percentage of zinc chloride and are completely
expended when the reaction temperature is reached.
Fluxes used for manual torch soldering contain a
high proportion of other halides in conjunction with the
zinc chloride, which provide an effective flux cover during the manual addition of filler metal. Reaction fluxes,
on reaching a specific temperature, penetrate the aluminum oxide film, react with the underlying aluminum by
deposing metallic zinc, and evolve gaseous aluminum
chloride, which appears as white smoke. The molten
zinc that forms when reaction fluxes are used is sometimes enough to produce soldered joints without additional soldering filler metal. These fluxes are used at
temperatures close to 370°C (700°F) because the zinc
filler metals melt at this temperature. Reaction flux residues are highly corrosive and should be removed from
the soldered workpieces by thorough rinsing in hot or
cold water.
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
119
Removal of Organic Flux Residue
The chloride-free organic fluxes are usually noncorrosive or, at most, only slightly corrosive, and the residues of most organic fluxes are not hygroscopic. Flux
residues are not typically removed from aluminum foil
assemblies thicker than 0.13 mm (0.005 in.) and aluminum wire greater than 0.25 mm (0.010 in.) in diameter.
Flux removal is considered necessary in high voltage
electrical applications or when insulating coatings are
applied. Flux removal is best when performed as soon
after soldering as possible. Flux residues are most easily
removed when they have not been overheated to the
char point, or “cooked,” by unduly long exposure to
soldering temperature.
Water immersion, cold or hot, is not recommended
for removal of organic flux residues. Water may cause
the soldering filler metal to penetrate into the aluminumfiller metal interface and promote electrochemical
attack and rapid failure of the joint. Flux residue
removal is best when accomplished with organic solvents, such as alcohol or chlorinated hydrocarbon solvents. The soldered joint can be dipped into the solvent,
but more effective cleaning is accomplished by scrubbing
the joint with a fiber brush or by mechanical agitation.
Removal of Reaction Flux Residue
Residues remaining after a reaction flux or chloride
flux is used should be removed as quickly as possible
after soldering. These residues are hygroscopic and
highly corrosive to aluminum. Both the chloride fluxes
and reaction fluxes contain inorganic chlorides or other
halides that are best removed with water. The assemblies, while still hot, can be immersed directly into hot
or boiling water or can be sprayed with hot water. In a
production line, flux removal is usually accomplished
by using several tanks of wash water in a cascade system
with a final rinse composed of clean, chloride-free water.
Flux residues containing high percentages of zinc
chloride are difficult to remove with water alone, so
chemical cleaning baths are often used to remove this
type of residue. Typically, a cleaning procedure consists
of a hot-water wash followed by soaking in a dilute
bath of hot hydrochloric-acid, another rinse, soaking in
a dilute solution of hot alkaline, and finally, thoroughly
rinsing in hot water. The workpieces may be dried in a
stream of hot air if water staining is to be avoided.
Test for Complete Flux Removal
A silver nitrate test is used to determine if any flux
residue remains on a workpiece after it has been
washed and dried. The silver nitrate test solution is
made by adding 5 g of silver nitrate to 100 mL of tripledistilled water, to which 3 or 4 drops of nitric acid have
been added. The solution should test acid to litmus.
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CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
To test for residual chlorides, a few drops of distilled
water are placed on an area where flux residue is suspected. After a few minutes, an eye dropper is used to
transfer the test water to a sample of the test solution. If
the test solution becomes cloudy, it indicates that chlorides are present. This test is extremely sensitive and
can detect airborne contamination and chlorides in tap
water. Because of this, the test requires judgment on the
part of the user. It is good practice to run a blank whenever this test is used. By carefully employing these techniques, operators can detect chloride residue as low as
1 ppm.
The silver nitrate test is essentially a test to determine
the presence of chlorides and should not be used with
fluxes that do not contain chlorides. For these fluxes, a
spectrophotometer can be used to detect the presence of
elements that make up organic flux residue.
contact with the flux because charring of the flux will
occur and the fluxing activity will be reduced or
destroyed. Organic flux residues should be removed
with alcohol.
SOLDERING PROCESSES
Reaction soldering occurs as the result of applying a
reaction flux that contains a high percentage of zinc chloride. This technique, illustrated in Figure 1.63, is especially suitable for aluminum applications. When the
reaction temperature of 370°C to 385°C (700°F to
725°F) is reached, the zinc chloride reacts chemically
with the aluminum and deposits zinc at the joints. This
reaction evolves aluminum-chloride fumes, so adequate
ventilation is imperative. Sufficient zinc to form line-contact joints is usually deposited from the flux alone. If
additional filler is required, zinc particles can be mixed
with the flux, or preplaced zinc or zinc-base soldering
filler metal can be used. Heat can be supplied by furnace,
by gas flame, or by resistance or induction processes. An
application of reaction soldering is shown in Figure 1.64.
Reaction fluxes are usually highly hygroscopic and
must be handled and stored with care. Moisture
absorption leads to the formation of hydrated zinc chloride; after this stands for a period of time, it forms oxychlorides that hamper satisfactory fluxing action and
filler metal flow. For maximum performance of reaction
fluxes, anhydrous vehicles such N-propyl alcohol, Nbutyl alcohol, or methylethyl ketone should be used
instead of water. When using reaction fluxes, it is essential to remove the alcohol vehicle and also the copious
fumes produced by the flux reaction by providing adequate exhaust ventilation of the work areas.
The excellent thermal conductivity of aluminum,
combined with the higher melting temperature of many
of the soldering filler metals used to join aluminum
assemblies typically require the use of a large-capacity
heat source to bring the joint area to the proper temperature. Uniform, well-controlled heating is a necessity.
Several soldering processes are described in this section.
Torch Soldering
Air-fuel gas torches are commonly used to solder aluminum assemblies. The process may be either manual or
automatic. Abrasion or ultrasonic techniques may be
used, or flux can be applied to the joint and the filler
metal either preplaced or manually fed. The best torch
soldering technique is to apply heat to both sides of the
assembly until soldering filler metal flow is initiated. The
flame is then moved directly over the joint slightly
behind the front of the filler metal flow. Because the
flame does not come into direct contact with the flux,
there is no premature flux reaction. A major application
of torch soldering is the soldering of U-return bends on
heat exchangers.
Heating with Soldering Irons
Soldering irons are commonly used, although it is
difficult to heat aluminum sheet thicker than 1.6 mm
(0.062 in.) with a soldering iron, even if the crosssectional area of an assembly is small. Auxiliary heat
sources such as ovens or hot plates are often used. Flux
may be applied to the joint, and soldering filler metal
wire may be fed manually into the joint. The soldering
iron is brought into direct contact with the joint immediately behind the front of filler metal flow. When an
organic flux is used, the iron should never be in direct
Furnace Soldering
Furnace soldering uses the heat of a furnace or oven
and can be performed with all types of soldering filler
metal for aluminum. Distortion of the workpieces due
to differential thermal expansion is low. Filler metal is
preplaced at the joints and flux is applied by spraying,
brushing, or immersion. Temperature control is critical
to ensure that fluxing action and filler-metal flow occur
simultaneously. If the temperature is not controlled,
poor wetting will result.
Reaction Soldering
Dip Soldering
Dip soldering (DS) is a process that uses heat from a
metal, oil, or salt bath in a vessel or pot in which the
workpieces are immersed. This process is well suited for
joining aluminum because the soldering pot itself is an
excellent large-capacity heat source. This method is
ideal for soldering aluminum assemblies at a high production rate and can employ the same techniques
and production schedules typically used to solder other
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
FLUX (ZnCI2)
FLUX (ZnCI2)
OXIDE
(AI2O3)
121
OXIDE (AI 2O3)
AI
AI
FLUX (ZnCI2)
AI CI3
(GAS)
CRACKS
OXIDE (AI 2O3)
AI
Source: Vianco, Paul T., 1999, Soldering Handbook, Miami: American Welding Society.
Figure 1.63—Schematic Illustration of
Reactive Soldering of Aluminum
metals. The low-temperature soldering filler metals and
organic fluxes are more readily adapted to this process,
although high-temperature filler metals and reaction
fluxes are sometimes employed.
Resistance Soldering
Figure 1.64—Heat Exchanger
Fabricated Using Reaction Soldering
(Reduced to 67%)
Resistance soldering (RS) is a process that uses heat
from the resistance to the flow of electric current in a
circuit containing the workpieces. The workpiece is
connected between a ground and a movable electrode
or between two movable electrodes. The resulting heat
is applied to the joint both by the electrical resistance of
the workpiece and by conduction from the electrode,
which is usually carbon. Resistance soldering can be
used to join aluminum to aluminum or to other metals.
It is also suitable for spot soldering or tack soldering.
When soldering aluminum, flux is usually applied to
the joint area by brush, and the soldering filler metal is
either preplaced in the joint or fed manually. A metal or
carbon electrode is then brought into contact with the
joint area and maintained in position while current
passes through the joint until filler-metal flow occurs.
Because the heat is generated in the aluminum, better
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CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
temperature control can be maintained and there is less
risk of damaging the flux by overheating. Flux residues
should be removed after soldering.
JOINT DESIGN
The joint designs used for soldering aluminum
assemblies are similar to those used for soldering other
metals. The most commonly used designs are forms of
lap, crimp, and T-joints. A good joint design will
accommodate the following conditions:
1. An ample area for soldering filler metal contact;
2. An adequate joint clearance and a path for flux,
filler metal, or both, to flow into the entire joint
area;
3. A means for proper placement of the filler
metal;
4. A means for flux escape or removal;
5. Minimum access for the entry of corrosive
attack; and
6. A contour suitable for subsequent protective
coating if needed.
The required joint clearance varies with the specific
soldering method, base alloy composition, soldering
filler metal composition, and the type of flux employed.
As a general guide, when chemical fluxes are used, joint
clearances ranging from 0.12 mm to 0.50 mm (0.005
in. to 0.020 in.) are required. When reaction fluxes are
employed, joint clearances ranging from 0.05 mm to
PREPARATION FOR SOLDERING
Aluminum surfaces must be free of grease, dirt, and
other foreign material before soldering. In most
instances, solvent degreasing is sufficient for surface
preparation. Wire brushing or chemical cleaning are
occasionally required for heavily oxidized surfaces,
especially surfaces of alloys containing high levels of
magnesium or silicon, or both, which often have particularly tenacious oxides that may need abrasive or chemical cleaning.
Oxide Removal
The oxide layer on the aluminum surface must be
removed to obtain sound soldered joints in aluminum.
Removal can be accomplished during soldering by
mechanical abrasion, ultrasonic dispersion, or fluxing
(refer to the Surface Preparation section of this chapter). Mechanical abrasion and ultrasonic dispersion are
described in this section.
AWS WELDING HANDBOOK
Abrading the aluminum surface under a layer of molten soldering filler metal permits soldering to occur.
Oxide removal can be accomplished through the molten
filler metals by brushing with a fiberglass or stainless steel
brush or buffing with stainless steel wool. Alternatively,
the filler metal rod may be used to break up the oxide
and allow molten filler metal to contact the aluminum and
bond to it, particularly when using zinc-base filler metals.
Another means of removing the oxide film is to
erode it from the aluminum using ultrasonic energy.
When ultrasonic energy is introduced into molten soldering filler metal, cavitation occurs, forming numerous
voids within the molten metal. Collapse of these voids
creates an abrasive effect that removes the aluminumoxide film and allows the filler metal to wet the aluminum.
Ultrasonic soldering can be accomplished when an
ultrasonically vibrating tip is brought into contact with
molten soldering filler metal on the workpiece. A more
effective approach is to dip the assembly into a pot of
molten filler metal that is agitated by ultrasonic energy.
PERFORMANCE OF SOLDERED
ALUMINUM JOINTS
The mechanical strength developed by soldered aluminum assemblies, although often of secondary importance, ranges approximately from a minimum equal
to the strength of soft soldering filler metals (4 MPa
[0.6 ksi]) to a maximum shear stress greater than 275
MPa (40 ksi). The intermediate- and high-temperature
filler metals retain considerable strength at temperatures at which soft filler metals melt (about 175°C
[347°F]). High-temperature filler metals are fully effective up to about 100°C (212°F) and can be exposed to
temperatures up to 175°C (347°F) without loss of
strength; however, creep can occur under conditions of
stress at temperatures higher than 120°C (248°F).
Like soldered joints in other metals, soldered joints
in aluminum corrode when two or more parts of the
joint are in contact with an electrolyte. The corrosion
process is essentially electrochemical in nature, and the
metals joined by the electrolyte form a galvanic couple.
The anodic element (the least noble cell element) corrodes more rapidly, protecting the remaining elements
until the anodic element is consumed. The rate of corrosion depends on the potential difference between the
elements, the distance that separates the elements, and
the composition of the electrolyte. When soldered joints
are properly cleaned, no residual salts remain. As long
as no moisture is present, no corrosion will occur. In
practice, these conditions are not usually attained, and
some corrosion will occur.
If soldering filler metal containing tin is used to solder aluminum, the intermetallic interface will have a
high tin content. This interface is highly negative
AWS WELDING HANDBOOK
(anodic) to the other constituents of the joint. When
exposed to an electrolyte, this highly negative interface
will corrode rapidly, and the joint fails catastrophically.
The filler metal separates from the aluminum as if cut
by a knife. For maximum service life, this type of joint
should be used in a dry atmosphere, or the joint should
be coated to protect it from exposure to the elements.
When a joint is formed with zinc soldering filler
metal, which is anodic to aluminum, galvanic corrosion
is spread over the face of the zinc. Because no highly
anodic, thin, intermetallic interface is present, the zinc
filler metal will protect the aluminum, and the joint will
remain intact until all the filler metal is consumed.
Assemblies prepared with pure zinc or zinc-aluminum
filler metals have withstood corrosive attack for many
years and are considered satisfactory for most applications requiring long outdoor service. An outstanding
example of a zinc-soldered assembly is the condenser
coil of an automobile air conditioner.
ADHESIVE BONDING
Adhesive bonding is a joining process in which an
adhesive, placed between faying surfaces, solidifies to
produce a bond. Most aluminum alloys are readily
joined by adhesive bonding.37 Depending on the application, this process can provide unique advantages over
other joining processes.
The primary advantage of adhesive bonding is that
applied loads can be distributed over a wide area,
thereby reducing the working stress levels. Additionally,
adhesive joints often can be made as strong as the base
materials. There is no weakening by a heat-affected
zone, such as that occurring with fusion welds. Joint
strength can be increased merely by increasing the joint
area (i.e., the overlap distance).
Another advantage of adhesive bonding is that aluminum can be joined to most other structural metals,
plastics, and composites. Also, the adhesive forms an
electrically insulating barrier between two metals being
joined. This insulating barrier reduces the likelihood of
galvanic corrosion, which occurs when metals with different electric potentials are in direct contact with one
another, as is usually the case when mechanical fasteners are used for joining. Adhesive bonding can also be
used to attenuate noise and structural vibration if the
adhesive and joint design are properly selected.
37. Refer to Chapter 10 of American Welding Society (AWS) Welding Handbook Committee, 2007, Welding Processes, Part 2, ed. A.
O’Brien and C. Guzman, vol. 3, Welding Handbook, 9th ed., Miami:
American Welding Society. See Appendix B of this volume for
detailed descriptions of chapter contents for the five volumes of Welding Handbook, 9th ed.
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
123
ADHESIVE MATERIALS
Most adhesives used for joining aluminum are
organic polymeric materials. The long-term mechanical
performance depends on the chemical nature of these
adhesives and the environment in which they are
expected to perform. Commercial adhesives are available in a wide range of compositions, spanning a large
spectrum of processes and performance properties.
The epoxy adhesives are the most often used for joining aluminum. These adhesives can be formulated to
cure either rapidly or slowly at room temperature. They
provide high-temperature performance and moisture
resistance that can be enhanced by curing at elevated
temperatures. The cleanliness and preparation of the
surface to be bonded is of paramount importance when
epoxy adhesives are used.
Anaerobic acrylics are another class of adhesives for
bonding aluminum. This group of adhesives is used in
applications in which only minimal surface preparation
can be performed, but high strength and durable joints
are required. As a class, these adhesives can provide
joint strength equivalent to that obtained with epoxies
and can be applied without requiring pristine oil-free
bonding surfaces. Anaerobic acrylic adhesives are capable of dissolving thin films of mill oil into the bulk
adhesive layer without adversely affecting joint strength
or performance. For aluminum, however, the weak natural oxide film found on non-anodized bonding surfaces will be the determining factor for maximizing the
bond strength. Additional surface treatments and corrosion-inhibiting primers must be used to prevent undermining corrosion at the metal-to-adhesive interface that
may occur in harsh environments. Nevertheless, anaerobic acrylics are a viable alternative to epoxies for
many metal bonding applications.
SURFACE PREPARATION
Complete wetting of the metal bonding surface by
the adhesive must be obtained to develop maximum
adhesion between the epoxy resin adhesive and the aluminum surface. Any oxide present on the surfaces of
the workpiece must be removed by grinding or wire
brushing before welding. In addition to removing aluminum oxide from the bonding surface, mechanically
abrading the bonding surface increases the surface area
available for bonding and decreases the joint stress for a
given load. The rough surface permits greater penetration and mechanical interlocking of the adhesive into
the bonding surface, thereby increasing the overall joint
strength.
Any mill oil present on the metal bonding surface
must be removed by vapor degreasing with an organic
solvent, such as trichloroethane, prior to the application of adhesive. If this is not practical or if the bonding
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CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
surface is small, wiping with a lint-free cloth saturated
with a suitable solvent until all traces of dirt and oil are
gone is acceptable. For some applications, this is all the
surface preparation required prior to applying the adhesive. Work with solvents should only be done in wellventilated areas.
Additional surface treatments are needed when
bonded metallic materials will be exposed to harsh
environments or when maximum bond strength is
required. Corrosion-inhibiting primers, usually containing chromium compounds, are often used on the surfaces of aluminum workpieces to prevent corrosion of
the metal at the bond interface. This is especially important for bonded joints in aluminum intended for service
in corrosive environments, such as salt. For these environments, it is important to take precautions to prevent
corrosion that may occur between the adhesive and
metal at the bond interface. Ultimately this will control
the long-term durability and bond strength of the joint.
A thin oxide film is always present on aluminum surfaces when exposed to air. This oxide film is often the
weak link in structures joined by adhesive bonding,
with joint failure occurring in the oxide layer rather
than the adhesive. To achieve maximum strength and
long-term durability of bonded joints in aluminum, the
thin oxide film must be removed first, and then a new
stronger oxide will form in its place. For critical applications, this requires the use of mineral-acid etching to
remove the natural oxide film from the surface of the
aluminum workpiece. This is followed by the application of either phosphoric-acid anodizing or chromicacid anodizing which will form a stronger, more durable oxide suitable for adhesive bonding. Mechanical
removal of the natural oxide film in lieu of acid etching
is not recommended because the newly exposed aluminum is highly reactive and oxidizes almost immediately
when in contact with oxygen, thereby reducing the
effectiveness of the oxide-removal procedure.
AWS WELDING HANDBOOK
2.
3.
4.
5.
6.
7.
8.
9.
10.
JOINING ALUMINUM TO
DISSIMILAR METALS
Aluminum can be joined to most other metals, either
directly or indirectly, by precoating the dissimilar metal
or using bimetallic transition pieces. In addition to riveting, bolting, and adhesive bonding, which can be used
to join aluminum to nonmetallics and also to other metals, the following processes have been used with specific
dissimilar metals:
11.
1. Low-temperature soldering can be used to join
aluminum to silver, bronze, copper, magnesium,
13.
12.
nickel, lead, tin, titanium, zinc, precious metals,
ceramics, cermet, and glass.
High-temperature soldering with a high-zinc
soldering filler metal is used for joining
applications such as bonding copper tubes into
flared aluminum tubes at the ends of the
circuits of aluminum air conditioning
condensers for automotive and household use.
Ultrasonic dip soldering is used to make tubular
connections, such as copper-to-aluminum in airconditioning condensers, and also “pigtailed”
wire connections between aluminum and copper
wire for electrical applications.
Ultrasonic soldering irons have been used to
precoat aluminum and other metals with zinc
soldering filler metal or other lower-meltingtemperature filler metals to facilitate joining of
dissimilar metals;
Brazing can be used to join aluminum to copper
after the joint surfaces have been precoated with
a silver-base filler metal, and to join aluminum
to steel that has been precoated with aluminum.
Diffusion welding can be used to join
aluminum to copper, nickel, stainless steel,
zirconium, uranium, and many of the silverplated and copper-plated metals.;
Flash welding is an excellent method for joining
aluminum to copper tube, rod, and plate
transition segments for refrigeration tubing
and electrical connectors.
Ultrasonic welding can be used to join aluminum
foil and sheet directly to silver, gold, beryllium,
copper, iron, germanium, magnesium,
manganese, nickel, palladium, platinum,
silicon, tin, tantalum, titanium, tungsten, and
zinc.
Cold welding (at room temperature) can be used
to join aluminum to copper with lap joints and
butt joints in wire, rod, and bar, primarily for
electrical applications.
Forge welding (elevated-temperature pressure
welding) can be used to join aluminum to copper, steel, stainless steel, and zinc to produce
bimetallic sheets and plates by hot rolling for
cookware, electrical connections, and transition
assemblies for welding.
Explosion welding can be used as a transition
sheet to join aluminum to copper, steel, and
stainless steel for the arc welding of plate,
tube, and ring sections.
Friction welding or inertia friction welding can
be used to join aluminum to copper, bronze,
brass, steel, stainless steel, magnesium, nickel,
titanium, and zirconium.
Plug welding, a gas metal arc process, can be
used to make through-holes in copper sheet, mild
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
125
obtain a combination of electrical and
mechanical connections in the form of a fused
rivet.
Gas tungsten arc welding performed with lowamperage DCEP can be used to join aluminum
to aluminum-coated steel by directing the arc
onto the weld pool of the aluminum alloy,
causing the weld pool to flow over the coating
without breaking the aluminum-steel bond.
(600°F) during welding. It is good practice to perform
the aluminum-to-aluminum weld first. This can provide
a larger heat sink for the steel-to-steel weld, which will
help prevent overheating the steel-aluminum interface.
For some applications, joint details can be designed to
minimize the amount of heat directed toward the transition weld.
When brazing is used to join aluminum to steel, the
steel is prepared by coating it with aluminum by
dipping the clean steel, with or without fluxing, into
molten aluminum at 690°C to 705°C (1275°F to 1300°F).
It should be noted that when flash welding is used to
join an assembly of aluminum-to-aluminum and copper-to-copper, the brittle copper-aluminum intermetallic
phase can be squeezed out of the joint during the upset
operation, and then arc welding can be used to
complete the aluminum-to-aluminum and copper-to-
various thicknesses and in strip, plate, and tubular
product forms, as shown in Figure 1.65. A major structural use is in the shipbuilding industry, where transition insert joints have become the standard means of
welding aluminum superstructures and bulkheads to
14.
Typical Applications for Bimetallic Transition
Inserts. Bimetallic transition inserts are available in
BIMETALLIC TRANSITION INSERTS
Bimetallic transition inserts are used to accommodate the welding of aluminum to a dissimilar metal,
such as steel or copper. Inserts are often used for producing welds of excellent quality within structural
applications.
One side of the metal is coated with aluminum so
that it can be welded to the aluminum side of another
workpiece using the GTAW or GMAW process. The
steel or copper side can be welded to a complementary
component. This technique is used for tube connections
in refrigeration, air-conditioning, and cryogenic tank
and piping applications. Examples of other applications
include joining aluminum tubes to carbon steel or stainless steel tube sheets for use in heat exchangers, welding
an aluminum deck house onto a steel ship deck, and
welding a large-diameter (365 m [120 ft]) aluminum
sphere (designed to hold liquid natural gas) to the steel
structure of a ship.
Welding of Bimetallic Transition Inserts
Steel-aluminum transition inserts can be used in production welding using gas metal arc welding (GMAW)
or gas tungsten arc welding (GTAW). One side of the
insert is welded steel-to-steel and the other aluminumto-aluminum.
Overheating the inserts during welding should be
carefully avoided, as this may cause growth of brittle
intermetallic compounds at the steel-aluminum interface of the transition insert. Some manufacturers of
bimetallic inserts recommend that the weld zone of the
steel-aluminum joint should not be heated above 315°C
Photographs courtesy of Dynamic Materials Corporation
Figure 1.65—Transition Inserts in Various
Thicknesses Available in Plate, Strip,
and Tubular Form
126
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
steel hulls, framing, and decks. This aluminum-to-steel
welding method makes it possible for shipbuilders to
maximize the benefits of both materials: the strength
and economy of steel, and the lightweight and corrosion resistance of aluminum.
Transition inserts for structural use in shipbuilding
are typically composed of 5XXX series aluminum welded
to low-carbon manganese steel. In addition to welding
aluminum tubes to steel or stainless steel tube sheets in
heat exchangers, bimetallic transition inserts are used
in other applications, such as couplings for welding
components of aluminum and stainless steel pipelines
with the arc welding processes. An example is shown in
Figure 1.66.
CORROSION PREVENTION
Oxyfuel gas welding, brazing, and some soldering
methods used for joining aluminum to other metals are
performed with fluxes containing a variety of chlorides.
Residues from these fluxes are hygroscopic and, on
absorption of moisture, become active electrolytes that
will accelerate corrosion in the aluminum member of
the dissimilar-metal joint. All flux residues must be
removed from aluminum workpieces and assemblies
after joining.
When aluminum is in direct contact with another
metal, the presence of an electrolyte will set up a galvanic cell between the two metals and cause preferential
attack. Because aluminum is anodic to most common
metals except magnesium and zinc, aluminum will pref-
Photograph courtesy of Dynamic Materials Corporation
Figure 1.66—A Welded Transition Coupling
Used to Join Aluminum and Stainless
Steel Components of a Pipeline
AWS WELDING HANDBOOK
erentially protect steel, copper, lead, and other metals
that are cathodic to it on the galvanic scale. These joints
should be painted, coated, wrapped, or protected by an
appropriate means to eliminate moisture or any electrolyte at the contact area.
ARC CUTTING
Two arc cutting processes used with aluminum,
plasma arc cutting and air carbon arc cutting are discussed in this section.38
PLASMA ARC CUTTING
Plasma arc cutting (PAC) is an arc cutting process
which employs a constricted arc and removes molten
metal with a high-velocity jet of ionized gas issuing
from the constricted orifice. This process can be used to
cut aluminum alloys and can be used in any position.
Compressed air, nitrogen, or a mixture of argon and
hydrogen is commonly used as the plasma-producing
gas. Argon, nitrogen or an argon-hydrogen mixture is
used as the shielding gas for the dual flow systems.
Equipment is available for both manual and mechanized cutting.
Aluminum can be cut within a wide range of operating conditions. The quality of the cut is related to the
operating conditions and the equipment used. Typical
conditions for mechanized plasma arc cutting are
shown in Table 1.69. Section thicknesses of 3.2 mm to
150 mm (0.13 in. to 6 in.) can be cut with mechanized
equipment. The maximum practical thickness for manual cutting is about 51 mm (2 in.).
The plasma arc process can also be used to gouge
aluminum to produce J-groove-joints and U-groovejoints. Special designs of the torch orifice are needed to
produce the desired shape of the grooves. The aluminum is melted during cutting, and the heat produces a
heat-affected zone (HAZ) similar to fusion welding on
each side of the cut. The metallurgical reactions that
occur during cutting of aluminum alloys are similar to
those produced during welding.
No significant problems occur when cutting nonheat-treatable alloys, but the HAZ adjacent to the cut
surface in some high-strength heat-treatable alloys, such
as Alloys 2014, 2024, and 7075, may display reduced
38. Refer to Chapter 15 of American Welding Society (AWS) Welding Handbook Committee, 2004, Welding Processes, Part 1, ed. A.
O’Brien, vol. 2, Welding Handbook, 9th ed., Miami: American Welding
Society. See Appendix B of this volume for a detailed description of
chapter contents for the five volumes of Welding Handbook, 9th ed.
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
127
Table 1.69
Typical Conditions for Mechanized Plasma Arc Cutting of Aluminum Alloys
Thickness
Orifice Diameter*
Speed
mm
in.
mm/s
in./min
mm
in.
Current
(DCEN), A
Power,
kW
6
1/4
127
300
3.2
0.125
300
60
13
1/2
86
200
3.2
0.125
250
50
25
1
38
90
4.0
0.156
400
80
51
2
9
20
4.0
0.156
400
80
76
3
6
15
4.8
0.188
450
90
102
4
5
12
4.8
0.188
450
90
152
6
3
8
6.4
0.250
750
170
*Plasma gas flow rates vary with orifice diameter and gas used from about 47 L/min (100 ft 3/h) for a 3.2 mm (0.125 in.) orifice to about 118 L/min (250 ft3/h) for
a 6.4 mm (0.250 in.) orifice. The gases used are nitrogen and 65% argon-35% hydrogen. The equipment manufacturer should be consulted for each application.
corrosion resistance. When cutting heat-treatable
alloys, shallow shrinkage cracks may develop in the
cut surface, as shown in Figure 1.67. Cracking in a
transverse section of an aluminum alloy is shown in
Figure 1.68.
Unlike machining methods that require a cutting
fluid or a lubricant, plasma arc cutting does not contaminate the metal, but any aluminum oxide formed on
the cut edges of the nonheat-treatable alloys during cutting should be removed prior to welding. Common
methods of oxide removal can be used. Before welding
the plasma arc-cut surface of heat-treatable alloys,
mechanical removal of edge cracks, up to a depth of
3.2 mm (0.13 in.), is recommended.
Figure 1.67—Cracking in the Plasma-Arc-Cut
Surface in a Heat-Treatable Aluminum
Alloy (Magnified 3X)
Figure 1.68—Transverse Section Through the Heat-Affected Zone of a
Heat-Treatable Aluminum Alloy Showing an Intergranular Crack (Magnified 100X)
128
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
A plasma arc cutting apparatus is generally sold as a
package, including the torch and the power source.
Because voluminous fumes develop when cutting aluminum, a water table and an exhaust hood are recommended for operator safety. When cutting close to a
water surface, hydrogen will be generated if molten aluminum reacts with water. A cross flow of air is required
to avoid a buildup of an explosive atmosphere. When
cutting under water, a perforated air line should be
used to bubble air through the water to avoid elevated
hydrogen concentrations.
AIR CARBON ARC CUTTING
Air carbon arc cutting (CAC-A) is a carbon arc cutting process variation that removes molten metal with a
jet of air. For aluminum, this process is more effective for
gouging grooves than for cutting. Grooves up to 25 mm
(1 in.) deep can be made in a single pass, but depth increments of 6.35 mm (0.25 in.) provide better process control. The width of the groove is determined primarily by
the size of the carbon electrode. The depth of the groove
is determined by the torch angle and travel speed.
The arc is operated with DCEN. Operating conditions must be closely controlled to ensure that all molten metal is blown from the workpiece surfaces. The arc
length must be great enough to permit the air stream to
pass under the tip of the electrode.
Carbon contamination commonly occurs on the surfaces of cuts in aluminum. Air carbon arc cutting can
cause intergranular cracking of the cut edges in heattreatable alloys, as previously described (refer to the
Plasma Arc Cutting section).
AWS WELDING HANDBOOK
The welding of aluminum in the automotive manufacturing is extensive, Figure 1.69(A) shows the structure of an automobile body frame and (B) shows other
aluminum components. The robotic welding of an
automobile frame is shown in Figure 1.70.
A multiple-arc welding application is shown in Figure 1.71, the construction of an aluminum trailer floor.
Figure 1.72 shows a manual welding project, an aluminum truck mount ladder. Figure 1.73 shows the welding of a section of an aluminum tool box.
Aluminum is extensively used in boats and ships of
all sizes and classes, including utility vessels, commercial
ships, and various types of military ships.
Figure 1.74 shows a littoral combat ship (LCS) under
construction for the United States Navy. It has an alu-
(A)
APPLICATIONS
Welded aluminum applications range from very thin
aluminum foil wrap, thin beverage cans, and phone cases
to structural aluminum applications in automobiles,
boats, ships, aircraft, space vehicles, and countless consumer products. Existing aluminum alloys and current
welding, cutting, or joining processes continue to meet
these varied production requirements; however, as special
aluminum materials are being developed, weld quality
and production techniques continue to improve, steadily
adding to the quality and diversity of aluminum products.
An example is the high-strength, wear-resistant aluminum
alloy, MSFC-398, that was originally developed by the
National Aeronautics and Space Administration (NASA)
for aerospace applications, but was subsequently transitioned to the automotive, marine, and other industries for
use in automobile parts and other wear-intensive products, such as pistons in outboard marine engines.
(B)
Photographs courtesy of the Aluminum Association
Figure 1.69—(A) Structural Aluminum
in an Automobile Body Frame, and
(B) Aluminum Components
AWS WELDING HANDBOOK
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
Photograph courtesy of The Lincoln Electric Company
Figure 1.70—Robotic Welding of an
Aluminum Automobile Frame
129
Photograph courtesy of Miller Electric
Company
Figure 1.73—Robotic Gas
Metal Arc Welding of an
Photograph courtesy of The Lincoln Electric Company
Figure 1.71—Multiple-Arc Welding a Truck-Trailer
Floor for a Major Trailer Manufacturer
Photograph courtesy of Austal USA
Photograph courtesy of Polar Custom Trailers
Figure 1.72—Aluminum Truck Mount Ladder
Welded Using Manual Gas Metal Arc Welding
Figure 1.74—Littoral Combat Ship
(LCS) with Aluminum Superstructure
in Final Stages of Construction
for the United States Navy
130
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
Photograph courtesy of Bollinger Shipyards, Inc.
AWS WELDING HANDBOOK
©Rafael
Gamo. Used with permission.
Figure 1.75—Aluminum Superstructure Mounted
to the Steel Hull of a Vessel to Reduce
Weight and Resist Corrosion
Figure 1.76—The Six-Story Museo Soumaya
Art Museum in Mexico City, A Steel Structure
Covered with 16,000 Hexagonal Aluminum Tiles
minum hull and an aluminum superstructure that reduces
weight and withstands the harsh sea environment. Figure
1.75 shows the aluminum superstructure mounted to the
steel hull of a vessel.
The aircraft industry makes important use of aluminum
parts. The wear resistance and light weight of aluminum
add to the efficiency of aircraft of all types, commercial
and military, and also for satellites and space vehicles.
Aluminum is widely applied in the construction
industry for window and door frames, roofing,
siding, and decorative elements of commercial and residential buildings. A related application of aluminum is
in the equipment, such as scaffolds, ladders, and concrete-casting forms, used during construction.
Figure 1.76 shows an aluminum-clad building, an art
museum in Mexico City. Approximately 16,000 octagonal aluminum tiles were used in the decorative cover for
the museum. Innumerable consumer products are made
of aluminum, such as appliances, indoor and outdoor furniture, garden fences, storage units, racks, railings, light
poles, playground and sports equipment, and any other
item that requires light weight, strength, and long service
life.
Considering the importance of the properties of aluminum to world-wide industry and commerce, a significant feature remains after aluminum products have
served the intended purpose: they are readily recyclable.
AWS WELDING HANDBOOK
SAFE PRACTICES
Chapter 17 of the Welding Handbook, Volume 1,
9th edition,39 provides a comprehensive presentation of
safety in welding, brazing, soldering, and cutting, which
is intended for reference collectively for the five
volumes of the 9th edition; thus, details of these topics
are not fully addressed in this chapter. This section
does not repeat the information in Chapter 17, but
provides references to appropriate codes and standards,
and also presents safe practices specific to the topics
discussed in this chapter.
The American National Standards Institute (ANSI)
standard Safety in Welding, Cutting, and Allied
Processes (ANSI Z49.1) should be consulted.40 Appendix
A provides a list of safety and health standards,
publishers, and facts of publication.
In addition to the general safe practices described in
the publications noted above, the following section pertains to the specific aspects of welding processes and
procedures associated with the welding of aluminum
and aluminum alloys. Because most welding processes
use enough heat to produce molten filler and base metal
to accomplish welding, the following conditions warrant
safety precautions in the welding of aluminum alloys:
1. High levels of fumes may be produced when
welding any aluminum alloy, however, welding
of the 5XXX series aluminum alloys tends to
produce higher fume levels; and
2. The welding of aluminum and aluminum alloys
tends to utilize argon-base or helium-base
shielding gases, which produce an intense arc
and very little visible fume. The ultraviolet
radiation produced by the arc reacts with
oxygen in the surrounding atmosphere to
produce ozone. The high reflectivity of
aluminum tends to exacerbate the problem.
While ozone may be produced during any arc
welding process, the particular features
associated with the welding of aluminum
make it more of a concern. Adequate ventilation
should always be used, and air sampling should
always be performed to ensure that ozone does
not exceed permissible exposure limits.
Ozone is produced as a result of the action of the arc
(UV) on oxygen in the surrounding atmosphere. While
39. American Welding Society (AWS) Welding Handbook Committee,
2001, Welding Science and Technology, ed. C. Jenney and A. O’Brien,
vol. 1, Welding Handbook, 9th ed., Miami: American Welding Society.
40. American National Standards Institute (ANSI), 2012, Safety in
Welding, Cutting, and Allied Processes, ANSI Z49.1:2012, Miami:
American Welding Society. A copy of this standard is available for
download at www.aws.org.
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
131
some degree with any shielding gas. Higher fumeproducing gases (and processes) will produce more visible fume, which helps to shield the atmosphere from the
arc rays. Processes that produce a very intense arc and
very little fume (such as GMAW and GTAW) will produce more ozone. Also, because aluminum is very
reflective, the production of ozone tends to be higher.
The use of filtering masks or air-supplied respirators
are required if it is determined that personnel are
exposed to excessive pollutants.
As with any welding process, the work area should
be kept clean of any paper, wood, rags, or other combustible materials that can be ignited by flying sparks.
Before repairs to equipment are attempted, electrical power
should be turned off and electric switch boxes locked.
SURFACE PREPARATION
Preparing a surface for welding, brazing, and other joining processes requires the removal of all grease, oil, dirt,
paint, and other contaminants that can generate hydrogen.
The cleaning and welding areas must be well ventilated. If chlorinated solvents are used for degreasing,
this should take place at a location remote from the
welding area. Highly toxic phosgene gas can result from
the dissociation of the vapors of chlorinated hydrocarbons (e.g., trichloroethylene and other chlorinated
hydrocarbons) by arc radiation.
Petroleum-base solvents, such as acetone, leave little
residue and are nontoxic when used in a well-ventilated
welding area, but these solvents have low flash points
and require special storage and handling. Instructions for
the use of the solvent provided by the manufacturer in
the safety data sheet (SDS) should be carefully followed.
Caution must also be observed due to the reaction
between aluminum and certain solvents and cleaners.
Safety data sheets provided by manufacturers outlining
the required safe practices in the use of the product
should be consulted and carefully followed.
If acid cleaning or etching of the aluminum surface is
required, it should be recognized that all acids used in
cleaning and etching solutions have the potential to be
extremely hazardous. Personnel using them should be
thoroughly familiar with all chemicals involved and
adequate safety equipment should be used. Hydrofluoric acid, used in some etchants, is highly corrosive and
can cause severe tissue damage, which can lead to cardiac arrest. Proper personal protective equipment must
be used, including chemical splash goggles, face shield,
neoprene (or other impervious material) gloves, and
acid resistant clothing. The worker should seek immediate medical attention if exposed. Information on the
safety data sheet (SDS) from the manufacturer of the
chemicals should be carefully followed. Acids must be
properly stored in accordance with the SDS and must
only be used under a fume hood.
132
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
AWS WELDING HANDBOOK
PLASMA ARC CUTTING
STUD WELDING
As noted in the plasma arc cutting section, voluminous fumes are evolved when cutting aluminum with
this process, therefore a water table and exhaust hood
are recommended for operator safety. When cutting
close to a water surface, hydrogen will be generated if
molten aluminum reacts with the water. A cross flow of
air is required to prevent a buildup of an explosive
atmosphere. When cutting under water, a perforated air
line should be used to bubble air through the water to
reduce hydrogen concentrations.
Personnel operating stud welding equipment should
be provided with face and skin protection to guard
against burns from spatter produced during welding.
Eye protection in the form of safety glasses with side
shields or a face shield with a No. 3 filter lens should be
worn to protect against arc radiation.
When an inert gas is used to shield aluminum stud
welding, proper procedures for handling, storing, refilling, and using the gas storage cylinders should be
observed. Capacitor-discharge stud welding is characterized by a sharp noise when the arc disintegrates the
stud tip. Continual exposure to this elevated noise level
may damage hearing, so the use of hearing protection is
advised. Operators with pacemakers should not operate
stud welding equipment or come near the welding vicinity.
Users of capacitors and capacitor-discharge equipment should exactly follow instructions from the manufacturer for equipment installation and repair.
Capacitors should be completely drained of electrical
charge before starting repairs. Other safety details are
outlined in Recommended Practices for Stud Welding
(ANSI/AWS C5.4-93).42
RESISTANCE WELDING
The main hazards that may be encountered with
resistance welding processes and equipment are the
following:
1. Electric shock from contact with high-voltage
terminals or components,
2. Ejection of small particles of molten metal from
the weld, and
3. Crushing of some part of the body between the
electrodes or other moving components of the
machine.
High-Frequency Generators. High-frequency gen-
erators must be equipped with safety interlocks on
access doors and automatic safety grounding devices to
prevent operation of the equipment when access doors
are open. The equipment should not be operated when
panels or high-voltage covers have been removed or
when interlocks and grounding devices are blocked.
The output high-frequency primary leads should be
encased in metal ducting and should not be operated in
the open. Induction coils and contact systems should
always be properly grounded for operator protection.
Grounding of high-frequency currents is more difficult
than low-frequency currents, and grounding lines must
be kept short and direct to minimize inductive
impedance. The magnetic field from the output system
must not induce heat in adjacent metallic sections or
fires or burns may result.
Injuries from high-frequency power, especially at the
upper range of welding frequencies, tend to produce
severe, local surface-tissue damage; however, they are
not likely to be fatal because current flow is shallow.41
41. Refer to Chapter 4 of American Welding Society (AWS) Welding
Handbook Committee, 2004, Welding Processes, Part 1, ed. A.
O’Brien, vol. 2, Welding Handbook, 9th ed., Miami: American Welding Society.
BIBLIOGRAPHY
American National Standards Institute (ANSI). 2005.
Safety in welding, cutting, and allied processes. ANSI
Z49.1:2012. Miami: American Welding Society. An
electronic copy of this publication is available online
at aws.org.
American Welding Society (AWS) Committee on Arc
Welding and Cutting. 1993. Recommended practices
for stud welding. AWS C5.4-93. Miami: American
Welding Society.
American Welding Society (AWS) Committee on Brazing and Soldering. 2007. Brazing handbook. 5th ed.
Miami: American Welding Society.
American Welding Society (AWS) Committee on Definitions and Symbols. 2010. Standard welding terms
and definitions. AWS A3.0M/A3.0:2010. Miami:
American Welding Society.
American Welding Society (AWS) Committee on Filler
Metals and Allied Materials. 2012. Specification for
aluminum and aluminum-alloy electrodes for
shielded metal arc welding. AWS A5.3/A5.3M:1999
(R2007). Miami: American Welding Society.
42. American Welding Society (AWS) Committee on Arc Welding
and Cutting, 1993, Recommended Practices for Stud Welding, ANSI/
AWS C5.4-93, Miami: American Welding Society.
AWS WELDING HANDBOOK
American Welding Society (AWS) Committee on Filler
Metals and Allied Materials. 2012. Specification for
bare aluminum and aluminum-alloy welding electrodes and rods. ANSI/AWS A5.10/A5.10M:2012
(ISO 18273:2004 MOD). Miami: American Welding
Society.
American Welding Society (AWS) Committee on Structural Welding. 2014. Structural welding code—Aluminum. AWS D1.2/D1.2M:2014. Miami: American
Welding Society.
American Welding Society (AWS) Welding Handbook
Committee. 2001. Welding science and technology.
Edited by C. Jenney and A. O’Brien. Vol. 1 of Welding handbook. 9th ed. Miami: American Welding
Society.
American Welding Society (AWS) Welding Handbook
Committee. 2004. Welding processes, part 1. Edited
by A. O’Brien. Vol. 2 of Welding handbook. 9th ed.
Miami: American Welding Society.
American Welding Society (AWS) Welding Handbook
Committee. 2007. Welding processes, part 2. Edited
by A. O’Brien and C. Guzman. Vol. 3 of Welding
handbook. 9th ed. Miami: American Welding Society.
Fridlyander, I. N., et al. 1967. Aluminum-base alloy.
British Patent GB1172736A, filed February 27,
1967, and issued December 3, 1969.
Pickens, J. R. 1985. Review of the weldability of lithium-containing aluminum alloys. Journal of materials science. 20: 4247–4258.
Pickens, J. R., F. H. Heubaum, and T. J. Langan.
1991. Airframe materials. Proceedings of 30th
annual CIM conference of metallurgists, Ottawa,
Canada, August 21.
Pickens, J. R., F. H. Heubaum, T. J. Langan, and L. S.
Kramer. 1989. Al-(4.5-6.3)Cu-1.3Li-0.4Ag-0.4Mg0.14Zr alloy Weldalite® 049. In Aluminum-lithium
alloys, 1397–1414. Edited by T. H. Sanders and E.
A. Starke. Birmingham, United Kingdom.: Materials
and Components Engineering Publications, Ltd.
Pickens, J. R., T. J. Langan, and E. Barta. 1986. The
weldability of Al-5Mg-2Li-0.1Zr alloy 01420. In
Aluminum-lithium alloys III, 137–147. Edited by C.
Baker, P. J. Gregson, S. J. Harris, and C. J. Peel. Vol.
3. London: The Institute of Metals.
Pickens, J. R. 1990. Recent developments in the
weldability of lithium-containing aluminum alloys.
Journal of materials science. 25: 3035–3047.
Resistance Welding Manufacturing Alliance (RWMA).
2003. Resistance welding manual. 4th ed. Philadelphia: RWMA.
Resistance Welding Manufacturing Alliance (RWMA).
1996. Bulletin 16: Resistance welding equipment
standards. Philadelphia: RWMA.
Vianco, P. T. 1999. Soldering handbook. 3rd ed.
Miami: American Welding Society.
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
133
SUPPLEMENTARY
READING LIST
Aluminum Association. 2009. Aluminum standards
and data. Publication 1. Washington, D.C.: The Aluminum Association.
Aluminum Association, 2002. Welding aluminum: theory and practice, Fourth ed. Washington, D.C.: The
Aluminum Association.
Anderson, T. 2010. Welding aluminum—questions and
answers, a practical guide for troubleshooting aluminum welding-related problems (2nd edition). ISBN:
978-0-87171-085-7 Miami: American Welding Society.
ASM International. 1990. Introduction to aluminum
and aluminum alloys. In Properties and selection:
Nonferrous alloys and special-purpose materials.
Vol. 2 of ASM handbook. Materials Park, Ohio:
ASM International.
ASM International. 1993. Brazing of aluminum alloys.
In Welding, brazing, and soldering. Edited by D. L.
Olson, T. A. Siewert, S. Liu, and G. R. Edwards.
Vol. 6 of ASM handbook. Materials Park, Ohio:
ASM International.
ASM International. 1993. Selection and weldability of
heat-treatable aluminum alloys. In Welding, brazing,
and soldering. Edited by D. L. Olson, T. A. Siewert,
S. Liu, and G.R. Edwards. Vol. 6 of ASM handbook.
Materials Park, Ohio: ASM International.
ASM International. 1993. Welding of aluminum alloys.
In Welding, brazing, and soldering. Edited by D. L.
Olson, T. A. Siewert, S. Liu, and G. R. Edwards.
Vol. 6 of ASM handbook. Materials Park, Ohio:
ASM International.
ASTM International. 2010. Standard test methods for
tension testing wrought and cast aluminum- and
magnesium-alloy products. ASTM B557-10. West
Conshohocken, Pennsylvania: ASTM International.
American Society of Civil Engineers (ASCE). 1962. Suggested specifications for structures of aluminum alloy
6063-T5 and 6063-T6. Journal of the structural division. 88(7): 47–96.
American Welding Society (AWS) Committee on Piping
and Tubing. 2008. Guide for the gas shielded
arc welding of aluminum and aluminum alloy pipe.
AWS D10.7M/D10.7:2008. Miami: American Welding Society.
Andrew, R. C. and J. Waring, 1974. Effect of porosity
on transverse weld fatigue behavior. Welding journal.
53(2): 85-s–90-s.
Baeslack, W. A., G. Fayer, S. Ream, and C. E. Jackson.
1975. Quality control in arc stud welding. Welding
journal. 54(11): 789–798.
134
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
Barhorst, S. 1985. The cathodic etching technique for
automated aluminum tube welding. Welding journal.
64(5): 28–31.
Brennecke, M. W. 1965. Electron beam welded heavy
gage aluminum alloy 2219. Welding journal. 44(1):
27-s–39-s.
Collins, F. R. 1958. Porosity in aluminum-alloy welds.
Welding journal. 37(6): 589–593.
Dalziel, C. F. 1956. The effects of electric shock on
man. Washington, D.C.: United States Government
Printing Office.
Dowd, J. D. 1952. Weld cracking of aluminum alloys.
Welding journal. 31(10): 448-s–456-s.
Dudas, J. H., and F. R. Collins. 1966. Preventing weld
cracks in high-strength aluminum alloys. Welding
journal. 45(6): 241-s–249-s.
Hill, H. N. 1961. Residual welding stresses in aluminum alloys. Metal progress. 80(2): 92–96.
Howden, D. G. 1971. An up-to-date look at porosity
formation in aluminum weldments. Welding journal.
50(2): 112–114.
Krumpen, R. P., and C. R. Jordan. 1984. Reduced fillet
weld sizes for naval ships. Welding journal. 63(4):
34–41.
Marsh, C. 1985. Strength of aluminum fillet welds.
Welding journal. 64(12): 335-s–338-s.
Marsh, C. 1988. Strength of aluminum T-joint fillet
welds. Welding journal. 67(8): 171-s–176-s.
Mathers, G. 2002. The welding of aluminum and its
alloys. Cambridge, England: Woodhead Publishing
Limited.
Murphy, J. L., and P. W. Turner. 1976. Wire feeder and
positioner for narrow groove electron beam welding.
Welding journal. 55(3): 181–190.
Murphy, J. L., R. A. Huber, and W. E. Lever. 1990.
Joint preparation for electron beam welding thin aluminum alloy 5083. Welding journal. 69(4): 125-s–
132-s.
Murphy, J. L., T. M. Mustaleski, and L. C. Watson.
1988. Multipass, autogenous electron beam welding.
Welding journal. 67(9): 187-s–195-s.
Nelson, F. G., and R. L. Rolf. 1966. Shear strengths of
aluminum alloy fillet welds. Welding journal. 45(2):
82-s–84-s.
Nelson, F. G., J. G. Kaufman, and E. T. Wanderer.
1969. Tensile properties and notch toughness of
groove welds in wrought and cast aluminum alloys
at cryogenic temperatures. Advances in cryogenic
engineering. 14: 71–82.
Nordmark, G. E. 1963. Peening increases fatigue
strength of welded aluminum. Metal progress. 84(5):
101–103.
Pease, C. C., F. J. Preston, and J. Taranto. 1973. Stud
welding on 5083 aluminum and 9% Ni steel for
cryogenic use. Welding journal. 52(4): 232–237.
AWS WELDING HANDBOOK
Pense, A. W., and R. D. Stout. 1970. Influence of weld
defects on the mechanical properties of aluminum
weldments. Bulletin 152. New York: Welding
Research Council.
Rolf, R. L. 1976. Welded aluminum cylinders under
external pressure. Proceedings of the ASCE Natural
water resources and ocean engineering convention,
San Diego, April 5–8.
Sanders, W. W. and R. H. Day. 1983. Fatigue behavior
of aluminum alloy weldments. Bulletin 286. New
York: Welding Research Council.
Saperstein, Z. P., G. R. Prescott, and E. W. Monroe.
1964. Porosity in aluminum welds. Welding journal.
43(10): 443-s–453-s.
Sharp, M. L., R. L. Rolf, G. E. Nordmark, and J. W.
Clark. 1982. Tests of fillet welds in aluminum.
Welding journal. 61(4): 117-s–124-s.
Shore, R. J., and R. B. McCauley. 1970. Effects of
porosity on high strength aluminum 7039. Welding
journal. 49(7): 311-s–321-s.
Shoup, T. E. 1976. Stud welding. Bulletin 214. New
York: Welding Research Council.
Singleton, R. C. 1963. The growth of stud welding.
Welding engineer. 7: 257–263.
Stol, I., K. L. Williams, and D. W. Gaydos. 2006. Back
to basics: Using a buried gas metal arc for seam
welds. Welding journal. 85(4): 28–33.
PERFORMANCE OF WELDS
Aluminum Association. 1986. Specifications for Aluminum Structures. Publication 30. Washington, D.C.:
Aluminum Association.
Aluminum Design Manual, The Aluminum Association.
Burk, J. D., and F. V. Lawrence. 1978. Effects of lackof-penetration and lack-of-fusion on the fatigue
properties of 5083 aluminum alloy welds. Bulletin
234. New York: Welding Research Council.
Kaufman, J. G., and G. W. Stickley. 1967. Notch
toughness of aluminum alloy sheet and welded joints at
room and subzero temperatures. Cryogenic technology. July/August.
Lawrence, F. V., and W. H. Munse. 1973. Effects of
porosity on the tensile properties of 5083 and 6061
aluminum alloy weldments. Bulletin 181. New York:
Welding Research Council.
Lawrence, F. V., W. H. Munse, and J. D. Burke. 1975.
Effects of porosity on the fatigue properties of 5083
aluminum alloy weldments. Bulletin 206. New York:
Welding Research Council.
McCarthy, W. A., H. Lamba, and F. V. Lawrence.
1980. Effects of porosity on the fracture toughness
of 5083, 5456, and 6061 aluminum alloy
weldments. Bulletin 261. New York: Welding
Research Council.
AWS WELDING HANDBOOK
Nelson, F. G., J. G. Kaufman, and M. Holt. 1966. Fracture characteristics of welds in aluminum alloys.
Welding journal. 45(7): 321-s–329-s.
Sharp, M. L. 1992. Behavior and design of aluminum
structures. New York: McGraw-Hill.
BRAZING
Aluminum Association. 1990. Aluminum brazing handbook. Publication 21. Washington, D.C.: Aluminum
Association.
Dickerson, P. B. 1965. Working with aluminum?
Here’s what you can do with dip brazing. Metals
Progress. 87(5): 80–85.
Dickerson, P. B. 1965. How to dip braze aluminum
assemblies. Metals Progress. 87(6): 73–78.
Patrick, E. P. 1975. Vacuum brazing of aluminum.
Welding journal. 54(3): 159–163.
Swaney, O. W., D. E. Trace, and W. L. Winterbottom.
1986. Brazing aluminum automotive heat exchangers in vacuum: Process and materials. Welding journal. 65(5): 49–57.
SOLDERING
Aluminum Association. 2004. Aluminum soldering handbook. Publication 22. Washington, D.C.: Aluminum
Association.
ALUMINUM-LITHIUM ALLOYS
Cross, C. E., D. L. Olson, G. R. Edwards, and J. F.
Capes. 1983. Weldability of aluminum-lithium
alloys. In Aluminum-lithium alloys II, 675–682.
Edited by T. H. Sanders and E. A. Starke. Warren-
CHAPTER 1—ALUMINUM AND ALUMINUM ALLOYS
135
dale, Pennsylvania: The Materials Society (TMS) and
the American Institute of Mining, Metallurgical, and
Petroleum Engineers (AIME).
Gayle, F. W., F. H. Heubaum, and J. R. Pickens. 1990.
Structure and properties during aging of an ultrahigh strength Al-Cu-Li-Ag-Mg alloy. Scripta metallurgica et materialia. 24: 79–84, 1990.
Gittos, M. F. 1987. Gas shielded arc welding of Al-Li
alloy 8090. Report 7944.01/87/556.2. Cambridge,
United Kingdom: The Welding Institute.
Kramer, L. S., F. H. Heubaum, and J. R. Pickens. 1989.
The weldability of high strength Al-Cu-Li alloys. In
Aluminum-lithium alloys, 1415–1424. Edited by T.
H. Sanders and E. A. Starke. Birmingham, United
Kingdom: Materials and Components Engineering
Publications, Ltd.
Langan, T. J., and J. R. Pickens. 1989. Identification of
strengthening phases in the Al-Cu-Li alloy
Weldalite® 049. In Aluminum-lithium alloys, 691–
700. Edited by T. H. Sanders and E. A. Starke. Birmingham, U.K.: Materials and Components Engineering Publications, Ltd.
Martukanitz, R. P., C.A. Natalie, and J. O. Knoefel.
1987. The weldability of an Al-Cu-Li alloy. Journal
of metals. 39(11): 42–43.
Moore, K. M., T. J. Langan, F. H. Heubaum, and J. R.
Pickens. 1989. Effects of Cu content on the corrosion and stress corrosion behavior of Al-Cu-Li
Weldalite® alloys. In Aluminum-lithium alloys,
1281–1291. Edited by T. H. Sanders and E. A.
Starke. Birmingham, U.K.: Materials and Components Engineering Publications, Ltd.
Pickens, J. R., F. H. Heubaum, and L. S. Kramer. 1990.
Ultra-high strength, forgeable Al-Cu-Li-Ag-Mg alloy.
Scripta metallurgica et materialia. 24: 457–465.
Pumphrey, W. I., and J. V. Lyons. 1948. Cracking during the casting and welding of the more common
binary aluminum alloys. Journal of the institute for
metals. 74: 439–455.
137
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CHAPTER
C H A P T E2 R
9
MAGNESIUM AND
MAGNESIUM
ALLOYS
Prepared by the
Welding Handbook
Chapter Committee
on Magnesium and
Magnesium Alloys:
C. E. Cross, Chair
Los Alamos National
Laboratory
J. F. dos Santos
Helmholtz-Zentrum
Geesthacht GmbH
M. Y. Lee
POSCO
X. Cao
MRC Aerospace
A. E. Shapiro
Titanium Brazing, Inc.
N. Y. Zhou
University of Waterloo
Welding Handbook
Volume 5 Committee
Member:
S. P. Moran
Weir American Hydro
Contents
Photograph courtesy of Helmholtz-Zentrum Geesthacht GmbH
A Magnesium Cover for an Automobile Fuel Tank, Cast in Two Parts and Welded Together using Friction Stir Welding (FSW)
Introduction
138
Alloying Elements
140
Arc Welding
148
Resistance Welding
165
High-Energy
Beam Welding
175
Solid-State Welding
179
Oxyfuel Gas Welding
190
Brazing
192
Soldering
196
Joining of Dissimilar
Metals
198
Plasma Arc Cutting
198
Applications
199
Safe Practices
206
Bibliography
207
Supplementary
Reading List
210
138
AWS WELDING HANDBOOK
CHAPTER 2
MAGNESIUM AND
MAGNESIUM ALLOYS
INTRODUCTION
Magnesium alloys are used in a wide variety of applications when light weight is an important requirement.
Structural applications include industrial machinery,
materials-handling equipment, commercial products,
and numerous components used in the aerospace, automotive and medical fields.1, 2
Magnesium alloys are ideal for use in components of
industrial machinery, such as textile weaving machines
and printing machines that operate at high speeds and
must therefore be lightweight to minimize inertial
forces. Examples of materials-handling equipment are
dock boards, grain shovels, and gravity conveyors.
Commercial products include luggage, ladders, and
cases for electrical or electronic devices, such as mobile
phone and computer cases.
Magnesium alloys have high specific strength and
stiffness, making these alloys particularly useful for
aerospace applications in which weight savings are paramount. For similar reasons, magnesium is used in the
manufacture of automobile components: wheels, body
panels, seat frames, engine blocks and cradles, and
gearbox housings. The properties of magnesium are
also beneficial when used in biodegradable medical
implants, which are designed to corrode within the
body over a specific period of time.
1. Welding terms and definitions used throughout this chapter are
from American Welding Society (AWS) Committee on Definitions and
Symbols, 2010, Standard Welding Terms and Definitions, Including
Terms for Adhesive Bonding, Brazing, Soldering, Thermal Cutting,
and Thermal Spraying, AWS A3.0M/A3.0:2010, Miami: American
Welding Society.
2. At the time this chapter was prepared, the referenced codes and
other standards were valid. If a code or other standard is cited without a date of publication, it is understood that the latest edition of the
referenced document applies. If a code or other standard is cited with
the date of publication, the citation refers to that edition only, and it
is understood that any future revisions or amendments to the code are
not included; however, as codes and standards undergo frequent revision, the reader should consult the most recent edition.
When weight is a design consideration, magnesium is
most often compared to aluminum, as both are considered low-density materials; however, magnesium is
considerably less dense than aluminum, i.e., (δAl = 2.70,
δMg = 1.74 specific gravity). This translates into a
lighter-weight metal. When compared to aluminum,
limitations to the use of magnesium are strength, cost,
formability, and corrosion resistance.
Magnesium alloys are not as strong or stiff as aluminum and they are more costly, less formable, and highly
susceptible to galvanic corrosion. Thus, choosing magnesium over aluminum for a specific application requires
a very strong incentive to minimize weight. (For comprehensive information on welding, brazing, and soldering of magnesium and magnesium alloys, refer to the
resources listed at the end of this chapter.)
CHEMICAL PROPERTIES
Magnesium is an alkaline earth metal (atomic number 12) that readily reacts with oxygen.3 When exposed
to air at elevated temperature, magnesium oxidizes rapidly and generates heat. This oxide formation inhibits
wetting and flow during welding, brazing, or soldering.
For this reason, a protective shield of inert gas or flux
must be used during exposure to elevated temperature
in order to minimize oxidation. The oxide layer that
forms on magnesium will recrystallize at high temperatures and become flaky, breaking up during welding
more readily than the oxide layer that forms on aluminum. Magnesium oxide (MgO) is highly refractory and
insoluble in both liquid and solid magnesium. When
exposed to air, magnesium will also form a relatively
3. The atomic number represents the number of protons in the
nucleus.
AWS WELDING HANDBOOK
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
unstable nitride (MgN2) that will decompose in the
presence of moisture.
Under non-abrasive operating conditions, the corrosion resistance of many magnesium alloys in dry atmospheres is equal to some aluminum alloys. The
formation of a gray oxide film on the surface is usually
the extent of attack. For maximum corrosion resistance, chemical surface treatments (e.g., chemical conversion coatings), paint finishes, and electroplating
(e.g., anodizing) can be used; however, galvanic corrosion can be a serious problem when magnesium is in
direct contact with other metals in the presence of an
electrolyte. Magnesium has a largely negative corrosion
potential relative to all other structural metals, which
means that it will preferentially corrode when joined to
dissimilar metals. This property of corrosion is often
planned for and used beneficially. In fact, magnesium
can be used as a sacrificial anode to protect other
metals from corrosive attack in applications such as offshore structures, pipelines, and water heaters. Problems
with galvanic attack can be mitigated by insulating the
joints between dissimilar metals and protecting against
contact with electrolytes.
Like other metals, some magnesium alloys are susceptible to stress-corrosion cracking if residual stresses
from welding or fabrication are not reduced to safe levels
by heat treatment.
PHYSICAL PROPERTIES
Magnesium has a low density and a correspondingly
high strength-to-weight ratio. It has a density of 1740
kg/m3 (0.0626 lb/in.3), which is low compared to the
density of steel at 7860 kg/m3 (0.283 lb/in.3) and the
density of aluminum at 2700 kg/m3 (0.0972 lb/in.3). On
an equal-volume basis, magnesium weighs about onefourth as much as steel and two-thirds as much as aluminum. Table 2.1 lists the comparative chemical and
physical properties of magnesium and aluminum.
Pure magnesium melts at 650°C (1202°F), which is
only slightly lower than the melting point for aluminum: 660°C (1220°F); magnesium boils at 1090°C
(1994°F), which is low compared to other structural
metals. This has implications regarding the stability of
magnesium and magnesium alloys that are joined by
gas metal arc welding or processes using keyhole welding techniques. These stability concerns are discussed in
subsequent sections of this chapter.
The average coefficient of thermal expansion for
magnesium alloys at temperatures from 18°C to 399°C
(65°F to 750°F) is about 27 × 10–6/°C (15 × 10–6/°F),
which is about the same as that of aluminum and twice
that of steel. The relatively high coefficient of thermal
expansion tends to cause considerable distortion during
welding and requires fixturing. Fixtures for the welding
Table 2.1
Comparative Chemical and Physical Properties of Pure Magnesium and Aluminum
Magnesium
Aluminum
Atomic number
12
Atomic weight
24
27
Specific gravity
1.74
2.70
Density*
1740 kg/m3 (0.0626 lb/in.3)
2700 kg/m3 (0.0972 lb/in.3)
Crystal structure
Hexagonal close-packed
Face-centered cubic
Melting point
650°C (1202°F)
660°C (1220°F)
Boiling point
1090°C (1994°F)
2467°C (4472°F)
Plastic deformation temperature
Below 225°C
Coefficient of thermal expansion
Average: 27 × 10–6/°C (15 × 10–6/°F)
18°C to 399°C (65°F to 750°F)
Thermal conductivity
Approximate: Pure Mg 154 W/(m × K)
Approximate: 30% more than Mg
Mg Alloys, Range: 70 W/(m × K) to 110 W/(m × K)
(40 Btu/[ft × h × °F] to 64 Btu/[ft × h°F])
Electrical conductivity
2.30 × 107 S/m
13
Approximate: 27 × 10–6/°C (15 × 10–6/°F)
18°C to 399°C (65°F to 750°F)
3.80 × 107 S/m
Latent heat of fusion
368 J/g
398 J/g
Specific heat
1.02 J/g°C
0.90 J/g°C
Modulus of elasticity
44 800 MPa (6500 ksi)
68 950 MPa (10 000 ksi)
*Density of steel, 7860 kg/m 3 (0.283 lb/in.).
139
140
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
of magnesium are very similar to those needed for
aluminum.
The thermal conductivity of magnesium is about
154 W/(m × K) (89 Btu/[ft × h × °F]); for magnesium
alloys, the thermal conductivity ranges from 70 W/(m ×
K) to 110 W/(m × K) (40 Btu/[ft × h × °F] to 64 Btu/[ft ×
h × °F]), which is about 70% that of aluminum.
The electrical conductivity of magnesium is 2.25 ×
107/Ω, which is about 60% that of aluminum. Magnesium requires a relatively low heat input for melting
because it has a comparatively low latent heat of fusion
(0.640 J/mm3) and specific heat (0.0178 J/°C × mm3),
which is similar to the heat input requirements of aluminum. On an equal volume basis, the total heat of
fusion is roughly two-thirds that for aluminum and
one-fifth that for steel.
MECHANICAL PROPERTIES
Magnesium and magnesium alloys have a hexagonal,
close-packed (HCP) crystal structure, with low-temperature plastic deformation (below 225°C [437°F]) limited
to dislocation slip on the {0 0 0 1} basal plane and
twinning on the {1012} pyramidal plane. Twinning is
possible only in compression, which leads to differences
in yield point data between tension and compression.
Therefore, the amount of deformation that can be sustained at room temperature is limited when compared
to structural steel and aluminum alloys, with tensile
elongations typically ranging from 2% to 15% (50 mm
[2.0 in.] gauge). It should be noted that formability
improves with temperatures above 225°C (437°F), at
which point additional slip systems engage, allowing
magnesium to be more severely worked. Thus, forming,
straightening, and weld peening are generally done at
elevated temperatures.
Magnesium has a modulus of elasticity of 44 800 MPa
(6500 ksi), which is lower than aluminum (68 950 MPa
[10 000 ksi]) and steel (206 800 MPa [30 000 ksi]).
This means that magnesium is less rigid than aluminum
and exhibits greater displacement under similar elastic
loads. Properties differ greatly between cast and wrought
forms of commercially pure magnesium, demonstrating
the effect that cold work and grain refinement have on
strengthening. Cast magnesium (commercially pure)
has a yield strength of about 21 MPa (3 ksi) and a
tensile strength of about 90 MPa (13 ksi). Wrought
magnesium products (commercially pure) have tensile
strengths in the range of 165 MPa to 221 MPa (24 ksi
to 32 ksi). Yield strength in compression is normally
lower than in tension due to the difference in deformation mechanisms (i.e., twinning in compression compared to dislocation slip in tension). Alloying can
significantly increase the mechanical properties of magnesium. Magnesium and magnesium alloys are notch
AWS WELDING HANDBOOK
sensitive, particularly in fatigue, because of the low ductility. Tensile properties increase and ductility decreases
as the testing temperature decreases.
ALLOYING ELEMENTS
The addition of alloying elements to magnesium can
profoundly affect strength, ductility, corrosion resistance, and weldability. Thus, it is important to identify
the constituents of a particular base metal alloy and
consider how alloying elements will affect weldability,
filler metal selection, and subsequent performance of
the weld. This section explains the standard magnesium
alloy designation system, describes the applications of
the alloying elements, and provides mechanical properties for various alloys.
ALLOY SYSTEMS
Most magnesium alloys are of a ternary type (Mg-X-Y)
and can be classified in one of four groups based on the
major alloying element: aluminum, zinc, thorium, or
rare earths.4 There are also two binary alloy systems
that employ either manganese or zirconium. Magnesium alloys can also be grouped according to service
temperatures. The Mg-Al-X and Mg-Zn-X alloy groups
are suitable only for room-temperature service, because
the tensile and creep properties of these alloys degrade
rapidly when the service temperature is above about
149°C (300°F). The magnesium-thorium and magnesiumrare-earth alloys are designed for elevated-temperature
service, because they have good tensile and creep properties up to 370°C (700°F).
Designation Method
Magnesium alloys are designated by a combination
letter-number system composed of four parts. Part 1 of
the designator includes code letters for the two principal alloying elements arranged in order of decreasing
percentage. Part 2 is a number indicating the percentages of the two principal alloying elements, rounded to
the nearest whole number and displayed in the same
order as the code letters. Part 3 is an assigned letter to
distinguish different alloys with the same percentages as
4. Specifically, rare earth elements are a group of 15 metallic elements
of similar chemical behavior, also known as lanthanides (atomic numbers 57–71), plus scandium and yttrium. They form an alloy known
as mischmetal, which consists primarily of cerium (50% to 75%) and
lanthanum (25%).
AWS WELDING HANDBOOK
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
the two principal alloying elements. Part 4 indicates the
condition of temper of the product and consists of a letter and number (similar to those used for aluminum), as
shown in the temper designation (T) and number is
added to the last letter of the designator, separated by a
hyphen.
To summarize, the AZ in Alloy AZ63A-T6 indicates
that aluminum and zinc are the two principal alloying
elements. The number 63 indicates that the alloy contains nominally 6 weight percent (wt %) aluminum and
3 wt % zinc. The letter A shows that this was the first
standardized alloy of this composition. The fourth part,
-T6, indicates that the product has been solution heattreated and artificially aged.
Table 2.2 lists the code letter designations for magnesium alloys; Table 2.3 shows temper designations.
141
Table 2.3
Temper Designations for Magnesium Alloys
F
As fabricated
O
Annealed, recrystallized (wrought products only)
H
Strain-hardened
T
Thermally treated to produce stable tempers other than F, O, or H
W
Solution heat-treated (unstable temper)
Subdivisions of H
H1, and one or more digits
Strain-hardened only
H2, and one or more digits
Strain-hardened and then partially
annealed
H3, and one or more digits
Strain-hardened and then stabilized
Subdivisions of T
T1
Cooled and naturally aged.
COMMERCIAL ALLOYS
T2
Annealed (cast products only)
T3
Solution heat-treated and then cold-worked
Magnesium alloys are produced in the form of castings and wrought products, including forgings, sheet,
plate, and extrusions. Most of the alloys produced in
these forms can be welded. The ASTM designation,
nominal composition, product form, and method of
manufacture of commercial magnesium alloys designed
for service at room-temperature are listed in Table 2.4.
Information for elevated-temperature service is listed in
Table 2.5. As noted in these tables, some alloys are
most prevalent in either wrought or cast forms. Examples of commonly used alloys from these two categories
are discussed in this section.
T4
Solution heat-treated
T5
Cooled and artificially aged
T6
Solution heat-treated and artificially aged
T7
Solution heat-treated and stabilized
T8
Solution heat-treated, cold-worked, and artificially aged
T9
Solution heat-treated, artificially aged, and cold-worked
T10 Cooled, artificially aged, and cold-worked
Wrought Alloys
Table 2.2
Code Letters for Magnesium Alloy Designations
Letter
Alloying Element
A
Aluminum
C
Copper
E
Rare earths
H
Thorium
J
Strontium
K
Zirconium
L
Lithium
M
Manganese
Q
Silver
S
Silicon
W
Yttrium
X
Calcium
Z
Zinc
Magnesium alloy AZ31B is one of the more common
alloys used to produce wrought plate. This alloy provides a good combination of strength, ductility, toughness, formability, and weldability in all wrought
product forms. It follows, therefore, that Alloy AZ31B
is frequently used in weldments designed for roomtemperature service. It can be strengthened by solid
solution and work hardening.
Alloys AZ80A and ZK60A, with higher percentages
of added aluminum, can be artificially aged to develop
precipitation hardening and higher strength for roomtemperature applications. Alloys containing aluminum
are susceptible to stress-corrosion cracking and are typically given a postweld heat treatment to relieve stress.
Alloys AZ10A, M1A, and ZK21A are not sensitive
to stress-corrosion cracking; therefore, postweld stress
relieving is not required. These alloys are strengthened
by work hardening for room-temperature service.
Alloys HK31A, HM21A, and HM31A can be
strengthened by a combination of work hardening and
then artificial aging. They are designed for elevatedtemperature service.
142
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
AWS WELDING HANDBOOK
Table 2.4
Commercial Magnesium Alloys
for Service at Room Temperature
Table 2.5
Commercial Alloys for
Service at Elevated Temperature
Nominal Composition, Wt % (Remainder Mg)
ASTM
Designation
Al
Zn
Mn
RE*
Zr
Th
Nominal Composition, Wt % (Remainder Mg)
ASTM
Designation
Th
Sheet and Plate
Zn
Zr
RE*
Mn
Ag
Sheet and Plate
AZ31B
3.0
1.0
0.5
—
—
—
HK31A
3.0
—
0.7
—
—
—
M1A
—
—
1.5
—
—
—
HM21A
2.0
—
—
—
0.5
—
Extruded Shapes and Structural Sections
Extruded Shapes and Structural Sections
AZ10A
1.2
0.4
0.5
—
—
—
AZ31B
3.0
1.0
0.5
—
—
—
AZ61A
6.5
1.0
0.2
—
—
—
EK41A
—
—
0.6
4.0
—
—
AZ80A
8.5
0.5
0.2
—
—
—
EZ33A
—
2.6
0.6
3.2
—
—
M1A
—
—
1.5
—
—
—
HK31A
3.2
—
0.7
—
—
—
ZK21A
—
2.3
—
—
0.6
—
HZ32A
3.2
2.1
0.7
—
—
—
ZK60A
—
5.5
—
—
0.6
—
QH21A
1.1
—
0.6
1.2
—
2.5
Sand, Permanent Mold, or Investment Castings
AM100A
HM31A
3.0
—
—
—
1.5
—
Sand, Permanent Mold, or Investment Castings
*As mischmetal (approximately 52% Ce, 26% La, 19% Nd, 3% Pr).
10.0
—
0.2
—
—
—
AZ63A
6.0
3.0
0.2
—
—
—
AZ81A
7.6
0.7
0.2
—
—
—
AZ91C
8.7
0.7
0.2
—
—
—
AZ92A
9.0
2.0
0.2
—
—
—
K1A
—
—
—
—
0.6
—
ZE41A
—
4.2
—
1.2
0.7
—
ZH62A
—
5.7
—
—
0.7
1.8
ZK51A
—
4.6
—
—
0.7
—
ZK61A
—
6.0
—
—
0.8
—
*As mischmetal (approximately 52% Ce, 26% La, 19% Nd, 3% Pr).
Cast Alloys
Magnesium alloys AZ91C and AZ92A are the most
widely used casting alloys for room-temperature service.
These alloys are more crack-sensitive than wrought AZ
alloys and, consequently, can require preheating prior
to welding.
Alloy EZ33A, designed for elevated-temperature service, has good strength stability and excellent pressure
tightness.
Alloys HK31A and HZ32A are designed to operate
at even higher temperatures than EZ33A. Alloy
QH21A has excellent strength properties up to 260°C
(500°F). All of these alloys require heat treatment to
develop optimum properties, and they all have good
welding characteristics.
MECHANICAL PROPERTIES
Typical strength properties for magnesium alloys at
room temperature are shown in Table 2.6. For castings,
the compressive strength and tensile yield strength are
about the same; however, for wrought products the
yield strength in compression is often lower than in tension due to a difference in deformation mechanism (dislocation glide versus twinning). Wrought alloys are
typically between 50% and 100% higher in strength
than cast alloys.
Tensile and creep properties of typical magnesium
alloys at three elevated temperatures are shown in Table
2.7. It can be observed in Table 2.7 that the alloys containing thorium (i.e., HK, HM, and HZ) have greater
resistance to creep at 200°C and 320°C (400°F and
600°F) than the magnesium-aluminum-zinc alloys.
MAJOR ALLOYING ELEMENTS
Alloying elements can provide useful improvements
to the mechanical properties of magnesium. In some
cases, heat treatment is required to attain these benefits.
Alloying elements can sometimes be detrimental to
weldability and corrosion resistance; thus, understanding how alloying and heat treatment influence metal
properties is important to achieving quality weldments.
AWS WELDING HANDBOOK
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
143
Table 2.6
Mechanical Properties of Magnesium Alloys at Room Temperature
Tensile Strength
ASTM
Designation
MPa
ksi
Tensile Yield Strength
(0.2% Offset)
MPa
Compressive Yield Strength
(0.2% Offset)
ksi
MPa
ksi
% Elongation in
51 mm (2 in.)
Sheet and Plate
AZ31B-O
255
37
152
22
110
16
21
AZ31B-H24
290
42
221
32
179
26
15
HK31A-H24
228
33
207
30
152
22
9
HM21A-T8
234
34
172
25
131
19
10
M1A-O
234
34
131
19
—
—
18
M1A-H24
269
39
200
29
—
—
10
76
11
10
Extruded Shapes and Structural Sections
AZ10A-F
241
35
152
22
AZ31B-F
262
38
200
29
97
14
15
AZ61A-F
310
45
228
33
131
19
16
AZ80A-F
338
49
248
36
152
22
11
AZ80A-T5
303
44
262
38
186
27
8
HM31A-T5
303
44
262
38
186
27
8
M1A-F
255
37
179
26
83
12
11
ZK21A-F
290
42
228
33
172
25
10
ZK60A-F
338
49
255
37
193
28
14
ZK60A-T5
358
52
303
44
248
36
11
1
Sand, Permanent Mold, or Investment Castings
AM100A-T6
276
40
152
22
152
22
AZ63A-F
200
29
97
14
—
—
6
AZ63A-T4
276
40
90
13
—
—
12
AZ63A-T6
276
40
131
19
131
19
5
AZ81A-T4
276
40
83
12
83
12
15
AZ91C-F
165
24
97
14
—
—
2
14
AZ91C-T4
276
40
83
12
—
—
AZ91C-T6
276
40
145
21
145
21
5
AZ92A-F
165
24
97
14
—
—
2
AZ92A-T4
276
40
97
14
—
—
9
AZ92A-T6
276
40
145
21
145
21
2
EK41A-T5
172
25
90
13
—
—
3
EZ33A-T5
159
23
103
15
103
15
3
HK31A-T6
221
32
103
15
103
15
8
HZ32A-T5
186
27
97
14
97
14
4
K1A-F
172
25
48
7
—
—
19
QH21A-T6
276
40
207
30
—
—
4
ZE41A-T5
207
30
138
20
138
20
4
ZH62A-T5
241
35
172
25
172
25
4
ZK51A-T5
206
30
165
24
165
24
4
ZK61A-T6
310
45
193
28
193
28
10
172
241
193
172
193
165
152
186
152
228
AZ31B-F
AZ80A-T5
HM31A-T5
ZK60A-T5
AZ92A-T6
AZ63A-T6
EZ33A-T5
HK31A-T6
HZ32A-T5
QH21A-T6
33
22
27
22
24
28
25
28
35
25
23
26
22
ksi
200
83
103
97
103
117
152
172
159
103
145
165
90
MPa
29
12
15
14
15
17
22
25
23
15
21
24
13
ksi
Tensile Yield
Strength
*Creep strength based on 0.2% total extension in 100 h.
179
159
HM21A-T8
152
AZ31B-H24
HK31A-H24
MPa
Alloy
Tensile
Strength
148°C (300°F)
—
—
—
—
—
4.1
3.8
1.0
—
3.5
3.0
—
—
1.0
ksi
—
—
—
28.3
26.2
6.9
—
24.1
20.7
—
—
6.9
MPa
Creep
Strength*
207
117
165
145
124
117
103
165
152
103
131
165
90
MPa
MPa
124
145
55
83
145
103
62
30
17
24
21
18
17
186
69
97
83
83
83
Casting Alloys
15
24
22
15
Extrusion Alloys
19
24
13
27
10
14
12
12
12
12
21
15
9
18
21
8
ksi
Tensile Yield
Strength
Sheet and Plate Alloys
ksi
Tensile
Strength
204°C (400°F)
82.7
53.8
65.5
55.2
—
—
—
75.2
—
—
78.6
41.4
—
MPa
12
7.8
9.5
8.0
—
—
—
10.9
—
—
11. 4
6.0
—
ksi
Creep
Strength*
97
83
138
83
55
55
—
124
62
41
103
83
41
MPa
14
12
20
12
8
8
—
18
9
6
15
12
6
ksi
Tensile
Strength
90
55
83
55
41
34
—
103
21
14
90
48
14
MPa
13
8
12
8
6
5
—
15
3
2
13
7
2
ksi
Tensile Yield
Strength
316°C (600°F)
Table 2.7
Properties of Some Representative Magnesium Alloys at Elevated Temperature
—
20.7
20.0
8.3
—
—
—
52.4
—
—
34.5
—
—
MPa
—
3.0
2.9
1.2
—
—
—
7.6
—
—
5.0
—
—
ksi
Creep
Strength*
144 CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
AWS WELDING HANDBOOK
AWS WELDING HANDBOOK
With most magnesium alloy systems, the solidification range increases correspondingly as the addition of
alloying elements increases. At the same time, decreases
take place in the melting temperature, thermal conductivity, and electrical conductivity. Consequently, less
heat input is required for fusion welding as the alloying
element content increases.
Aluminum
When added to magnesium, aluminum provides the
most favorable attributes of the major alloying elements; aluminum increases strength, castability and
weldability, and general corrosion resistance. On solidification, a eutectic reaction results in the formation of a
divorced intermetallic phase, β-Mg17Al12, commonly
observed in microstructures of castings and weldments.
This phase can also form as an incoherent precipitate
on aging of solution heat treated magnesium-aluminum
alloys, but without significant effect on strength. Only
the alloys with high aluminum content (e.g., AZ80A)
will respond to aging; however, when in solution, aluminum is a potent strengthener. Alloys containing more
than 1.5 wt % aluminum may be susceptible to stress
corrosion and may require postweld stress relief.
The addition of zinc to magnesium-aluminum alloys
improves fluidity and increases room-temperature
strength by refining the age-hardening precipitate. Zinc
atoms replace aluminum atoms in the intermetallic, and
the beta phase becomes Mg17 (Al,Zn). But concentrations of zinc higher than 1.5 wt % in high-aluminumcontent alloys may lead to hot cracking in welds. Also,
high levels of both aluminum and zinc (i.e., greater than
10 wt %) may lead to a brittle cast structure associated
with the continuity of brittle intermetallics.
Beryllium
Magnesium alloys have a tendency to burn during
melting and casting. The addition of beryllium up to
about 0.001 wt % reduces this tendency. Beryllium is
added to magnesium filler metals to reduce oxidation
and to lower the risk of ignition at elevated temperatures
during joining operations.
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
145
Lithium
Special ultralight and stiff magnesium alloys containing large amounts of lithium (e.g., LA141A) have been
successfully produced. When lithium content is greater
than 11 wt %, the magnesium matrix phase becomes
body-centered cubic (BCC) and has good formability at
room temperature. These alloys also respond to aging
for improved strength.
Manganese
Manganese has very little effect on tensile strength,
but slightly increases yield strength. The most important function of manganese is to improve the saltwater
corrosion resistance of magnesium-aluminum and magnesium-aluminum-zinc alloys by modifying impurity
iron compounds. Magnesium-manganese alloys have
relatively high melting temperatures and thermal conductivities; therefore, these alloys can require somewhat
higher welding heat input than the AZ-type alloys.
Weld joint efficiency is low in magnesium-manganese
alloys because of grain growth in the heat-affected zone.
Rare Earths
Rare earths are added either as mischmetal or didymium (i.e., a mixture of 85 wt % praseodymium and
15 wt % neodymium) and tend to form large quantities
of low melting eutectics that allow feeding of solidification shrinkage, thus avoiding hot cracking and
microporosity in welds and castings. These elements
will also form Guinier-Preston (GP) zones and semicoherent precipitates on aging (e.g., Mg3Nd), thus
improving strength.5 The stability of these precipitates
along grain boundaries at elevated temperatures probably contributes to the improved creep resistance of rareearth alloys.
Silicon
Silicon is added to magnesium to improve the fluidity of alloys in the molten state (e.g., AS21 and AS41).
Additions are limited to below 1.2 wt % to minimize
the formation of coarse eutectic constituents, which are
harmful to ductility and impact strength.
Silver
Copper
Copper is added to magnesium-zinc alloys (e.g.,
ZC63A) to provide enhanced response to aging and to
improve ductility. While magnesium-zinc-copper alloys
have better creep resistance than AZ91E, corrosion
resistance is inferior.
Silver improves the mechanical properties of magnesium-rare-earth alloys and alloys containing thorium by
modifying age-hardening precipitates and potentially
aiding in nucleation. Alloy QH21A-T6 is among the
5. Guinier-Preston zones are local regions of high alloy content providing a precursor for second phase formation.
146
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
highest strength magnesium casting alloys commercially
available for room-temperature service, and also has
good weldability. These benefits also add significantly
to the cost of this alloy.
Thorium
Thorium additions greatly increase the strength of
magnesium alloys at temperatures up to 370°C (700°F).
The most commonly used alloys contain 2 wt % to
3 wt % thorium in combination with zinc, zirconium,
or manganese. Thorium improves the weldability of alloys
containing zinc.
Yttrium
Yttrium is added to magnesium-rare earth alloys (e.g.,
WE43A and WE54A) to improve high-temperature
strength and creep resistance in the age-hardened condition. These alloys have superior corrosion resistance
compared to other high-temperature magnesium alloys.
AWS WELDING HANDBOOK
A precipitation-hardening heat treatment following
solution heat treatment will increase the yield strength,
tensile strength, and hardness, but usually with some
loss of ductility and toughness. Combinations of solution heat treating, strain hardening, and precipitation
hardening are sometimes used with wrought products
to produce excellent strength properties. In such cases,
fine precipitation is augmented by the presence of dislocations created during deformation.
WELDABILITY
The relative weldability of magnesium alloys joined
by gas shielded arc welding and resistance spot welding
processes is shown in Table 2.8. Castings are not usu-
Table 2.8
Relative Weldability of Magnesium Alloys
Zinc
Magnesium-zinc alloys display a marked response to
aging, producing GP zones and coherent MgZn2 precipitates. The addition of copper to magnesium-zinc alloys
leads to improved ductility and response to aging. As
previously noted, zinc is often used in combination with
aluminum to improve the room-temperature strength of
magnesium-aluminum alloys. Zinc is also used in combination with zirconium, thorium, or rare earths to produce precipitation-hardenable magnesium alloys with
good strength properties.
Zirconium
Zirconium is a powerful grain-refining agent when
used in magnesium alloys that do not contain aluminum. It is added to alloys containing zinc, thorium, rare
earths, or combinations of these. Zirconium is believed
to have a beneficial effect on the weldability of magnesium-zinc alloys, probably because of grain refinement.
HEAT TREATMENT
Magnesium alloys are heat-treated to improve
mechanical properties and relieve residual stress. The
type of heat treatment depends on the alloy composition, product form, and service requirements. A solution heat treatment is used to uniformly dissolve
alloying elements in the magnesium matrix and is usually followed by a water quench to trap alloying elements in solution. Magnesium alloys in this condition
will be low in strength, but high in ductility and toughness with no precipitates and low dislocation density.
Alloy
Gas Shielded
Arc Welding
Resistance
Spot Welding
Wrought Alloys
AZ10A
Excellent
AZ31B, AZ31C
Excellent
Excellent
Excellent
AZ61A
Good
Excellent
AZ80A
Good
Excellent
HK31A
Excellent
Excellent
HM21A
Excellent
Good
HM31A
Excellent
Good
M1A
Excellent
Good
ZK21A
Good
Excellent
ZK60A
Poor
Excellent
Cast Alloys
AM100A
Good
—
AZ63A
Fair
—
AZ81A
Good
—
AZ91C
Good
—
AZ92A
Fair
—
EK41A
Good
—
EZ33A
Excellent
—
HK31A
Good
—
HZ32A
Good
—
K1A
Excellent
—
QH21A
Good
—
ZE41A
Good
—
ZH62A
Poor
—
ZK51A
Poor
—
ZK61A
Poor
—
AWS WELDING HANDBOOK
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
ally welded using resistance welding processes. The
magnesium-aluminum-zinc alloys and alloys that contain rare earths or thorium as the major alloying element have the best weldability. Alloys with zinc as the
major alloying element are more difficult to weld. These
alloys have a rather wide melting range, which makes
them more sensitive to hot cracking. With proper joint
design and welding conditions, joint efficiency will
range from 60% to 100%, depending on the alloy and
temper.
Most wrought alloys are readily welded with the
resistance spot welding process. Because of the short
weld cycles and heat transfer features that are characteristic of resistance spot welding, fusion zones are finegrained and heat-affected zones undergo only slight
degradation from grain coarsening.
147
SURFACE PREPARATION
The cleanliness of magnesium alloy components and
filler metals is important for obtaining sound joints of
acceptable quality. Any surface contamination or heavy
oxidation will inhibit wetting and fusion; thus, magnesium alloys are supplied by the manufacturer with an
oil coating, an acid-pickled surface, or a chromate
conversion coating for protection during shipping and
storage. The surfaces and edges to be joined must be
cleaned immediately before welding to remove the surface
protection and any dirt or oxide that may be present. 6
Chemical cleaners commonly used for magnesium
alloys are listed in Table 2.9.
6. ASM International, 1994, Surface Engineering, vol. 5, ASM Handbook, 10th ed., Materials Park, Ohio: ASM International.
Table 2.9
Chemical Cleaning of Magnesium Alloys
Type of Treatment
Composition of Solution
Method of Application
Uses
Alkaline cleaner
Sodium carbonate
Sodium hydroxide
Water to make
Temperature
Solution pH
85 gm (3 oz)
57 gm (2 oz)
3.8 L (1 gal)
87°C–100°C (190°F–212°F)
11 or greater
3 min–10 min immersion
followed by cold water rinse
and air dry.
Used to remove oil and grease
films and also chrome-pickle
residue or dichromate
coatings.
Bright pickle
Chromic acid
Ferric nitrate
Potassium fluoride
Water to make
Temperature
680 gm (1.5 lb)
150 gm (5.3 oz)
14.2 gm (0.5 oz)
3.8 L (1 gal)
16°C–38°C (60°F–100°F)
0.25 min–3 min immersion
followed by cold and hot water
rinse and air dry.
Used after degreasing to
prepare surfaces for welding
and brazing. Results in bright,
clean surface; resistant to
tarnish.
Spot weld cleaners
No. 1 Bath
Conc. sulfuric acid
Water to make
Temperature
38 mL (1.3 fl oz)
3.8 L (1 gal) 21°C–32°C
(70°F–90°F)
Immerse 0.25 min–1 min in
No. 1 bath. Rinse in cold
water, followed by immersing
in either No. 2 or No. 3 bath.
No. 2 Bath
Chromic acid
Conc. sulfuric acid
Water to make
Temperature
680 gm (1.5 lb)
2.1 mL (0.07 fl oz)
3.8 L (1 gal) 21°C–32°C
(70°F–90°F)
No. 3 Bath
Chromic acid
Water to make
Temperature
9.4 gm (0.33 oz)
3.8 L (1 gal) 21°C–32°C
(70°F–90°F)
Flux remover clean
Sodium dichromate
Water to make
Temperature
23 gm (0.5 lb)
3.8 L (1 gal)
82°C–100°C (180°F–212°F)
Immerse 2 hours in boiling
bath, followed by cold and hot
water rinse and air dry.
Used after hot-water cleaning
and chrome pickling to remove
or inhibit any flux particles
remaining from welding or
brazing.
Chrome pickle
MIL-M-3171 Type 1
AMS 2475
Sodium dichromate
Conc. nitric acid
Water to make
Temperature
680 gm (1.5 lb)
710 mL (24 fl oz)
3.8 L (1 gal)
21°C–32°C (70°F–90°F)
0.5 min–2 min immersion,
hold in air 5 s, followed by
cold and hot water rinse and
air or forced dry, max 121°C
(250°F). When brushed on,
wait 1 min before rinse.
Used as paint base and for
surface protection; also as
second step in flux removal.
Applied with brush for touch-up
of welds and treatment of large
structures.
Used after degreasing to
remove oxide layer and prepare
surface for spot welding.
Results in consistently low
surface resistance.
For No. 2 bath, immerse
3 min, followed by cold water
rinse and air dry.
For No. 3 bath, immerse 0.5
min, followed by cold water
rinse and air dry.
148
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
The best ways to remove contaminants, such as oil,
grease, and wax are by washing with organic solvents
or degreasing with vapors of a chlorinated hydrocarbon
solvent.7 Subsequent cleaning with alkaline or emulsion-type cleaners is recommended to ensure that the
surfaces are absolutely free of oil or grease. Alkaline
cleaners will also remove previously applied chemical
surface treatments. Cleaners of this type that are suitable for steel are generally satisfactory for magnesium.
Cleaning can be accomplished with either the immersion or the electrolytic method. Thorough water rinsing
after alkaline cleaning, preferably by spray, is necessary
to remove the alkaline cleaning agent to avoid degradation of subsequent acid chemical baths used to treat the
workpieces.
After all oil or other organic material has been
removed, the workpiece should be chemically or
mechanically cleaned. A bright pickle will produce suitably clean surfaces for welding. A final mechanical
cleaning is preferred for most critical production applications to ensure uniform surface cleanliness. Stainless
steel wool or a stainless steel wire brush is recommended; however, wire brushing should not gouge the
surface. For resistance spot welding, chemical cleaning
is preferred because it provides a uniformly low surface
resistance (refer to Table 2.9).
If neutralization is necessary after chemical cleaning
and prior to rinsing, a water solution of 49 g/L (6.5 oz/
gal) of sodium metasilicate at 80°C (180°F) can be
used. After cleaning, the components must be carefully
protected from contamination during all subsequent
handling operations.
Any oxide film or soot on the surface of weldments
can be removed by wire brushing or by chemical treatment in a water solution of 120 g/L (16 oz/gal) of tetrasodium pyrophosphate and 90 g/L (12 oz/gal) of sodium
metaborate at 82°C (180°F).
ARC WELDING
Arc welding processes used with an inert shielding
gas, i.e., gas metal arc welding (GMAW) and gas tungsten arc welding (GTAW), are particularly suitable for
the arc welding of magnesium alloys. Argon or helium
shielding gas, or mixtures of argon and helium, serve to
protect molten magnesium and surrounding hot metal
from excessive oxidation. Processes that involve the use
of flux are not as effective.
7. Vapors of these solvents are toxic. Refer to American National
Standards Institute (ANSI), 2005, Safety in Welding, Cutting, and
Allied Processes, ANSI Z49.1:2012, Miami: American Welding Society.
An electronic copy of this publication can be downloaded from
www.aws.org.
AWS WELDING HANDBOOK
Joint designs, filler alloy selection, and welding
parameters of GTAW and GMAW are detailed in this
section.
JOINT DESIGN
Joint designs suitable for gas-shielded arc welding
processes are shown in Figure 2.1. The thickness limitations for welding these joint designs are shown in Table
2.10. Because of the high deposition rate of the gas
metal arc welding process, a root opening or a beveled
joint, or both should be used to provide space for the
deposited metal. Increasing the travel speed to maintain
a conventional bead size is not acceptable, because
undercutting, incomplete fusion, or insufficient weld
penetration can result.
Backing is employed when welding sheet metal components to help control joint penetration, root surface
contour, and heat removal. Strips of magnesium, aluminum, copper, mild steel, or stainless steel can be
employed as backing material. When a temporary backing strip is used, the root side of the joint should be
shielded with inert gas to prevent oxidation of the root
surface; the gas is supplied through holes in the backing
strip. In instances where a backing strip cannot be used
because of space limitations, a chemical flux can be
applied to the root side of the joint to smooth the root
bead and control joint penetration. Chemical fluxes
must be completely removed after welding to avoid corrosive attack.
FILLER METALS
Most magnesium alloys are weldable when the
proper filler metal is employed. A filler metal alloy that
is identical to the base metal, or one with a slightly
lower melting point and wider solidification range, usually provides good weldability and minimizes weld
cracking. Recommended filler metals for various magnesium alloys are shown in Table 2.11. The availability
of the preferred filler metal alloy can be limited, however, and a substitute choice may be required.
Alloy ER AZ61A is one of the more commonly available filler metal alloys used to weld magnesium-aluminum-zinc alloys. Alloys ER AZ61A or ER AZ92A filler
metals can be used to weld alloys of similar composition; however, alloy ER AZ61A filler metal is preferred
because of low cracking tendencies.
Alloy ER AZ92A filler metal shows less crack sensitivity for welding cast magnesium-aluminum-zinc and
magnesium-aluminum alloys (AM100A). The deposited
metal will respond to precipitation heat treatments
applied to the repaired casting. Alloy ER AZ101A filler
metal can also be used to weld magnesium-aluminumzinc cast alloys.
AWS WELDING HANDBOOK
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
149
60°
(typical)
60°
A to C
T
T
T
B
A to G
Square-Groove
Butt Joint
B to C
A to F
Double-V-Groove
Butt Joint
Single-V-Groove
Butt Joint
45°–60°
A to C
T
T
B to G
A to C
Fillet Corner Joint
Single-Bevel-Groove
Corner Joint
Square-Groove
T-Joint, Single Weld
F to H
A to C
45°
(typical)
A to C
5T
T
Square-Groove
T-Joint, Double Weld
T
Double-Bevel-Groove
T-Joint
Key:
A = 0 mm (0 in.)
B = 1.6 mm (0.062 in.)
C = 2.4 mm (0.094 in.)
F = 3.2 mm (0.125 in.)
G = 4.8 mm (0.188 in.)
H = 6.4 mm (0.250 in.)
T = thickness
Figure 2.1—Typical Joint Designs
for Arc Welding of Magnesium Alloys
Lap Joint
1.0 mm
6.4 mm
1.0 mm
(0.040 in.) (0.250 in.) (0.040 in.)
4.8 mm
(0.188 in.)
0.64 mm
6.4 mm
0.64 mm
(0.025 in.) (0.250 in.) (0.025 in.)
1.6 mm
4.8 mm
1.6 mm
(0.062 in.) (0.188 in.) (0.062 in.)
4.8 mm
(0.188 in.)
1.0 mm
(0.040 in.)
D
E
F
G
H
J
1.0 mm
(0.040 in.)
9.5 mm
(0.375 in.)
4.8 mm
(0.188 in.)
t (min)
t (max)
t (min)
t (max)
Short-Circuiting Transfer
t (min)
9.5 mm
(0.375 in.)
Note (c)
Not recommended
Not recommended
12.7 mm
(0.500 in.)
6.4 mm
(0.250 in.)
Note (c)
Note (c)
0.64 mm
(0.025 in.)
3.2 mm
(0.125 in.)
Note (c)
Note (c)
9.5 mm
(0.375 in.)
1.0 mm
4.0 mm
4.0 mm
(0.040 in.) (0.156 in.) (0.156 in.)
Not recommended
9.5 mm
1.6 mm
3.2 mm
1.6 mm
2.4 mm
4.0 mm
(0.375 in.) (0.062 in.) (0.125 in.) (0.062 in.) (0.094 in.) (0.156 in.)
4.0 mm
(0.156 in.)
Note (c)
19 mm
(0.750 in.)
9.5 mm
(0.375 in.)
Not recommended
0.64 mm
4.0 mm
1.6 mm
4.0 mm
4.0 mm
12.7 mm
(0.500 in.) (0.025 in.) (0.156 in.) (0.062 in.) (0.156 in.) (0.156 in.)
Note (c)
Note (c)
4.8 mm
(0.188 in.)
12.7 mm
(0.500 in.)
Note (c)
12.7 mm
(0.500 in.)
6.4 mm
(0.250 in.)
Note (c)
6.4 mm
1.0 mm
6.4 mm
1.6 mm
4.8 mm
4.8 mm
(0.250 in.) (0.040 in.) (0.250 in.) (0.062 in.) (0.188 in.) (0.188 in.)
Note (c)
9.5 mm
4.8 mm
9.5 mm
(0.375 in.) (0.188 in.) (0.375 in.)
9.5 mm
(0.375 in.)
t (max)
Spray Transfer
12.7 mm
0.64 mm
4.8 mm
0.64 mm
4.8 mm
4.8 mm
(0.500 in.) (0.025 in.) (0.188 in.) (0.025 in.) (0.188 in.) (0.188 in.)
t (max)
DCEP
The Use of Gas Metal Arc Welding with
Single- or double-welded lap joint.
Strength depends on size of fillet welds.
Maximum strength in tension on doublewelded joints is obtained when lap equals
five times thickness of thinner member.
Double-welded T-joint. Used on thick material
requiring 100% joint penetration.
Double-welded T-joint. Suggested thickness
limits based on 40% joint penetration.
Single-welded T-joint. Suggested thickness
limits based on 40% joint penetration.
Single or multiple-pass complete penetration
weld. Used on thick materials to minimize
welding. Produces square joint corners.
Single-pass complete penetration weld. For
material thicker than suggested maximum,
use single-bevel-groove corner joint E. It
requires less welding, especially if a square
corner is required.
Multiple-pass complete penetration weld.
Used on thick materials. Minimizes distortion
by equalizing shrinkage stress on both
sides of joint.
Multiple-pass complete penetration weld.
Used on thick material. On material thicker
than suggested maximum, use the doubleV-groove weld, butt joint C, to minimize
distortion.
Single-pass, complete penetration weld.
Used on lighter material thicknesses.
Remarks
a. Based on good welding practices and the use of gas tungsten arc welding with 300 A of ac, or DCEN, or with 125 A of DCEP, and also the use of gas metal arc welding with 400 A of DCEP.
b. Refer to Figure 2.1 for the appropriate joint design.
c. Thickest material in commercial use may be welded this way.
Note (c)
Note (c)
Note (c)
9.5 mm
(0.375 in.)
9.5 mm
(0.375 in.)
C
Note (c)
6.4 mm
9.5 mm
6.4 mm
(0.250 in.) (0.375 in.) (0.250 in.)
t (min)
B
t (max)
DCEN
0.64 mm
6.4 mm
0.64 mm
(0.025 in.) (0.250 in.) (0.025 in.)
t (min)
AC
A
Joint
Designb
The Use of Gas Tungsten Arc Welding with
Table 2.10
Thickness Limitations for Arc Welded Joints in Magnesium Alloys a
150 CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
AWS WELDING HANDBOOK
AWS WELDING HANDBOOK
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
151
matching, minimum galvanization, or sufficient
response to heat treatment is required. For these and
other special service requirements, the material supplier
should be consulted for additional information.
Table 2.11
Recommended Filler Metals
for Arc Welding Magnesium Alloys
Recommended Filler Metal*
Alloys
ER AZ61A
ER AZ92A
ER EZ33A
ER AZ101A
Base
Metal
Wrought Alloys
AZ10A
X
X
AZ31B
X
X
AZ61A
X
X
AZ80A
X
X
ZK21A
X
X
HK31A
X
HM21A
X
HM31A
X
M1A
X
Cast Alloys
AM100A
X
X
X
AZ63A
X
X
X
AZ81A
X
X
X
AZ91C
X
X
X
AZ92A
X
X
X
EK41A
X
X
EZ33A
X
X
HK31A
X
X
HZ32A
X
X
K1A
X
X
QH21A
X
X
ZE41A
X
X
ZH62A
X
X
ZK51A
X
X
ZK61A
X
X
*Refer to AWS A5.19-92 (R2006), Specification for Magnesium Alloy Welding Electrodes and Rods, for additional information.
The ER EZ33A (rare-earth–zinc–zirconium) filler
metal is used to weld wrought and cast alloys designed
for high-temperature service. The resulting welded
joints will have good mechanical properties at elevated
temperatures; however, ER EZ33A filler metal should
not be used for welding aluminum-containing magnesium alloys because of the possibility for severe cracking problems.
Casting repairs should be made with a filler metal of
the same composition as the base metal when color
PREHEATING
The need to preheat components prior to welding is
largely determined by the alloy, product form, section
thickness, and the degree of restraint on the joint. Thick
sections or highly restrained joints can require preheating to prevent cracking. This is particularly true of
alloys with limited ductility, such as those high in zinc.
Recommended preheat temperature ranges for cast
magnesium alloys are shown in Table 2.12. To avoid
significant degradation of weldment properties, the
maximum preheat temperature should not exceed the
solution heat-treating temperature for the alloy.
The method used for preheating depends on the size
of the component. Furnace heating is preferred, but
large components may have to be preheated locally. An
air-circulating furnace with a temperature control of
±6°C (±11°F) is recommended for preheating castings.
The furnace temperature should not cycle above the
maximum temperature (see Table 2.19). Solution heattreated castings or solution heat-treated and aged castings can be charged into a furnace operating at the preheat temperature without damage. Castings should
remain in the furnace until they are uniformly heated
and welding should proceed immediately after castings
are removed from the furnace. Most castings can be
cooled in still, ambient air after welding without risk of
cracking; however, castings of intricate design should be
cooled more slowly to room temperature to avoid distortion.
GAS TUNGSTEN ARC WELDING
Gas tungsten arc welding (GTAW) can be used for
joining magnesium components and for repairing
magnesium castings; it is particularly well suited for
welding thin sections. Control of heat input and the
weld pool is better with GTAW than with gas metal arc
welding (GMAW), and GTAW is inherently a more stable
process.8
8. Refer to Chapter 3, Gas Tungsten Arc Welding, in American Welding Society (AWS) Welding Handbook Committee, 2004, Welding
Processes, Part 1, ed. A. O’Brien, vol. 2, Welding Handbook, 9th ed.,
Miami: American Welding Society. See Appendix B of this volume for
a detailed description of chapter contents for the five volumes of
Welding Handbook, 9th ed.
152
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
AWS WELDING HANDBOOK
Table 2.12
Recommended Preheat and Postweld Heat Treatments for Welds in Cast Magnesium Alloys
Alloy
AZ63A
Metal Temper
Before Welding
Desired
Temper After
Welding
Weld Preheat*
Postweld Heat Treatment*
T4
T4
Heavy and unrestrained sections: none or local.
Thin and restrained sections: 177°C–382°C
(350–720°F)
1.5 h at 388°C (730°F)
T4 or T6
T6
Heavy and unrestrained sections: none or local.
Thin and restrained sections: 177°C–399°C
(350°F–750°F)
1.5 h at 388°C (730°F) and 5 h at
219°C (425°F)
T5
T5
Heavy and unrestrained sections: none or local.
Thin and restrained sections: None to 260°C
(500°F) (1.5 h max at 260°C [500°F])
5 h at 219°C (425°F)
AZ81A
T4
T4
Heavy and unrestrained sections: none or local.
Thin and restrained sections: 177°C–399°C
(350°F–750°F)
0.5 h at 416°C (780°F)
AZ91C
T4
T4
Heavy and unrestrained sections: none or local.
Thin and restrained sections: 177°C–399°C
(350°F–750°F)
0.5 h at 416°C (780°F)
T4 or T6
T6
Heavy and unrestrained sections: none or local.
Thin and restrained sections: 177°C–399°C
(350°F–750°F)
1.5 h at 416°C (780°F) and either 4 h
at 216°C (420°F) or 16 h at 168°C
(335°F)
T4
T4
Heavy and unrestrained sections: none or local.
Thin and restrained sections: 177°C–399°C
(350°F–750°F)
0.5 h at 410°C (770°F)
T4 or T6
T6
Heavy and unrestrained sections: none or local.
Thin and restrained sections: 177°C–399°C
(350°F–750°F)
0.5 h at 410°C (770°F) and either 4 h
at 260°C (500°F) or 5 h at 219°C
(425°F)
AM100A
T6
T6
Heavy and unrestrained sections: none or local.
Thin and restrained sections: 177°C–399°C
(350°F–750°F)
0.5 h at 416°C (780°F) and 5 h at
219°C (425°F)
EK41A
T4 or T6
T6
None to 260°C (500°F) (1.5 h max at 260°C [500°F])
16 h at 204°C (400°F)
T5
T5
None to 260°C (500°F) (1.5 h max at 260°C [500°F])
16 h at 204°C (400°F)
EZ33A
F or T5
T5
None to 260°C (500°F) (1.5 h max at 260°C [500°F])
5 h at 216°C (420°F); or 2 h at 329°C
(625°F) and 5 h at 216°C (420°F)
HK31A
T4 or T6
T6
None to 260°C (500°F)
16 h at 204°C (400°F); or 1h at 316°C
(600°F) and 16 h at 204°C (400°F)
HZ32A
F or T5
T5
None to 260°C (500°F)
16 h at 316°C (600°F)
K1A
F
F
None
None
ZE41A
F or T5
T5
None to 316°C (600°F)
2 h at 329°C (625°F); or 2 h at 329°C
(625°F) and 16 h at 177°C (350°F)
ZH62A
F or T5
T5
None to 316°C (600°F)
16 h at 249°C (480°F); or 2 h at 329°C
(625°F) and 16 h at 177°C (350°F)
ZK51A
F or T5
T5
None to 316°C (600°F)
16 h at 177°C (350°F); or 2 h at 329°C
(625°F) and 16 h at 177°C (350°F)
ZK61A
F or T5
T5
None to 316°C (600°F)
48 h at 149°C (300°F)
T4 or T6
T6
None to 316°C (600°F)
2 h to 5 h at 499°C (930°F) and 48 h at
129°C (265°F)
AZ92A
*Temperatures shown are maximum allowable; furnace controls should be set so temperature does not cycle above maximum.
AWS WELDING HANDBOOK
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
153
Welding Current
Magnesium alloys are welded using gas tungsten arc
welding techniques and equipment similar to those used
for aluminum. Welding can be accomplished using
alternating current (ac) or direct current (dc).9 Alternating current is preferred because the ac polarity provides
an arc-cleaning action. Specifically, the removal of surface oxide is accomplished during the electrode positive
portion of the ac cycle. Conventional ac of 60 Hz with
high-frequency arc stabilization or square-wave ac can
be used. With square-wave ac, the partitioning between
positive and negative electrode polarities is adjustable,
within limits. This type of power can provide adequate
cleaning action, good joint penetration, and arc stability. A cross section of a weld made with 60 Hz ac is
shown in Figure 2.2(A).
Modern variable-polarity power sources, originally
developed for welding thick-section aluminum, are
especially well suited for welding magnesium. These
power sources allow for independent adjustment of current and time at positive and negative polarities, with a
near-instantaneous change in polarity. This permits a
higher level of control compared to ac, which makes it
possible to achieve various combinations of cleaning
and penetration.
Direct current electrode positive (DCEP) provides an
arc with excellent cleaning action; however, this polarity can only be used to weld thin sections because the
welding current is limited by heating of the tungsten
electrode. Heat transfer is inefficient and joint penetration tends to be wide and shallow, as shown in Figure
2.2(B). Welds in relatively thick sections are typified by
low welding speeds, wide bead faces, and wide heataffected zones with large grain size.
Direct current electrode negative (DCEN) is not
commonly used for welding magnesium alloys because
of the absence of arc-cleaning action; however, this type
of power is sometimes used for mechanized welding of
square-groove butt joints in sections up to 6.4 mm
(0.25 in.) thick. Careful preweld cleaning and good
fitup are needed to produce sound welds. Welds with
narrow, deep joint penetration can be produced with
DCEN and helium shielding, as shown in Figure 2.2(C).
Shielding Gases
Argon, helium, and mixtures of these gases can be
used. The factors governing the selection of the shielding gas for magnesium alloys are the same as those for
9. Refer to Chapter 1, Arc Welding Power Sources, in American
Welding Society (AWS) Welding Handbook Committee, 2004, Welding
Processes, Part 1, ed. A. O’Brien, vol. 2, Welding Handbook, 9th ed.,
Miami: American Welding Society. See Appendix B of this volume for
a detailed description of chapter contents for the five volumes of
Welding Handbook, 9th ed.
(A) Alternating Current
(B) Direct Current Electrode Positive
(C) Direct Current Electrode Negative
Figure 2.2—Cross Sections of Gas Tungsten
Arc Welds Made in 4.8 mm (0.188 in.) Alloy
AZ31B with Various Types of Power
other metals, particularly aluminum. Oxygen, hydrogen, nitrogen, or carbon dioxide should not be used.
Electrodes
Electrodes of pure tungsten (EWP), tungsten-thorium
(EWTh-1 or EWTh-2), and tungsten-zirconium (EWZr)
can be used with magnesium alloys. The selection
depends primarily on the type of welding current and
the welding amperage to be used. The tungsten-thorium
electrodes should be restricted to use with dc.
154
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
AWS WELDING HANDBOOK
Welding Parameters
Typical parameters for the manual gas tungsten arc
welding of butt joints in magnesium alloys are shown in
Table 2.13. Welding conditions for mechanized gas
tungsten arc welding of butt joints for two thicknesses
of Alloy AZ31B (1.6 mm [0.062 in.] and 4.8 mm
[0.190 in.]) are shown in Table 2.14 Parameters shown
are for a balanced ac power source. This data can be
used as a guide for establishing welding procedures for
a specific application.
Repair Welding of Castings
Gas tungsten arc welding is recommended for repairing magnesium alloy castings, but the use of this process should be limited to repairing discontinuities in
clean metal, including broken sections, sand or blow
holes, cracks, and cold shuts. Repair welding is not recommended in areas containing gross porosity or inclusions of oxide or flux. Castings that have been
organically impregnated for pressure tightness or that
may contain oil in porous sections should not be
welded. Often, castings are part of integrated aircraft
structures that are heat treated to meet strength requirements and must therefore be heat treated again if they
are repaired by welding.
Factors to be considered when welding castings
include the following: type of alloy, previous heat treat-
ment, size and intricacy of sections, and degree of
restraint. The alloy should be identified, either from
designation markings or by chemical or spectrographic
analysis. The alloy and heat-treated condition of the
casting will determine the need for preheating and the
selection of the preheat temperature. Castings can be
welded in the as-cast, solution heat-treated, or solution
heat-treated and aged condition.
Castings should be stripped of paint and degreased
before welding, and conversion coatings should be
removed from around flawed areas with stainless steel
wool or a wire brush. A rotary deburring tool is recommended for removing defects and preparing the area for
welding. Broken workpieces should be clamped in position for welding. (Refer to Table 2.10 for the appropriate joint preparation.) When large holes or defective
areas are to be filled with weld metal, backing can be
used to prevent excessive melt-through.
The casting should be preheated if the section to be
repaired is relatively thick or highly restrained by surrounding structure. Welding of broken pieces should
commence at the center of the joint and progress
toward the ends, and medium-size weld beads are preferred. Low welding current can result in incomplete
fusion, oxide contamination, or porous welds, whereas
high welding current can cause weld cracking or incipient melting in the heat-affected zone.
The filling of holes is the most critical type of repair
relative to cracking. The arc should be struck at the bot-
Table 2.13
Typical Conditions for Manual Gas Tungsten Arc Welding of Magnesium Alloys
Thickness
mm
in.
Joint
Design1
No. of
Passes
Welding
Current (ac),
A
Pure Tungsten (EWP)
Electrode Diameter
mm
in.
Argon Flow2
L/min
Welding Rod Diameter
ft3/h
mm
in.
1.0
0.040
A
1
35
1.6
0.062
5.7
12
2.4
0.094
1.6
0.062
A
1
50
2.4
0.094
5.7
12
2.4
0.094
2.0
0.080
A
1
75
2.4
0.094
5.7
12
2.4
0.094
2.5
0.100
A
1
100
2.4
0.094
5.7
12
2.4
0.094
3.2
0.125
A
1
125
2.4
0.094
5.7
12
3.2
0.125
4.8
0.190
A
1
160
3.2
0.125
7.1
15
3.2
0.125
6.4
0.250
B
2
175
4.0
0.156
9.4
20
3.2
0.125
9.5
0.375
B
3
175
4.0
0.156
9.4
20
4.0
0.156
9.5
0.375
C
2
200
4.8
0.188
9.4
20
3.2
0.125
12.7
0.500
B
3
175
4.0
0.156
9.4
20
4.0
0.156
12.7
0.500
C
2
250
4.8
0.188
9.4
20
3.2
0.125
1. A—Square-groove butt joint, 0 root opening.
B—Single-V-groove butt joint, 1.6 mm (0.062 in.) root face, 0 root opening, 60° minimum included V-bevel.
C—Double-V-groove butt joint, 2.4 mm (0.094 in.) root face, 0 root opening, 60° minimum included V-bevel.
2. Helium shielding will reduce the welding current about 20 A to 30 A. Thorium-bearing alloys will require about 20% higher current.
AWS WELDING HANDBOOK
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
155
Table 2.14
Conditions for Automatic Gas Tungsten Arc Welding
of Square-Groove Butt Joints in Magnesium Alloy AZ31B
Welding Speed
Type of Power
mm/s
in./min
Weldinga
Current,
A
Filler Metal Feed Rateb
mm/s
Electrode Diameterc
in./min
Arc Length
mm
in.
mm
in.
Thickness = 1.6 mm (0.062 in.)
ac (balanced wave)
5.1
12
55
14.8
35
2.4
0.094
0.6
0.025
10.2
24
60
21.2
50
2.4
0.094
0.6
0.025
15.2
36
70
22.9
54
3.2
0.125
0.6
0.025
19.1
45
95
40.6
96
3.2
0.125
0.6
0.025
29.6
70
170
67.7
160
4.8
0.188
0.6
0.025
33.9
80d
195
80.4
190
4.8
0.188
0.6
0.025
40.2
95d
200
85.9
203
4.8
0.188
0.6
0.025
Thickness = 4.8 mm (0.190 in.)
DCEN
20.3
48
75
33.9
80
3.2
0.125
0.6
0.025
DCEP
33.9
80d
120
77.9
184
6.4
0.250
0.5
0.020
ac (balanced wave)
14.4
34d
300
67.3
159
6.4
0.250
0.5
0.020
8.5
20d
170
29.6
70
3.2
0.125
0.8
0.030
3.0
7d
4.2
10e
6.4
0.250
0.5
0.020
DCEN
DCEP
a.
b.
c.
d.
e.
120
With helium shielding.
Alloys AZ61A or AZ92A filler metal of 1.6 mm (0.062 in.) diameter except where noted (see Note e).
Pure tungsten or zirconia-tungsten for ac; thoria-tungsten for dc.
Maximum speed for arc stability and prevention of undercutting.
Filler metal diameter is 2.4 mm (0.094 in.).
tom of the hole and welding should progress upward.
The arc should not be held too long in one area to avoid
the possibility of cracking or incipient melting in the
heat-affected zone. The arc should be extinguished by
gradually reducing the welding current to zero using
appropriate current controls. This will permit the weld
pool to solidify slowly, which will prevent crater cracking.
welding time and fabrication costs. Because of the high
vapor pressure characteristic of magnesium, however, a
tendency toward excessive spatter and arc instability
exists when using the GMAW process. This can result in
welds of inferior quality and thus, inferior performance.
GAS METAL ARC WELDING
Argon is the most commonly used shielding gas for
GMAW. Occasionally, mixtures of argon and helium
are used to aid filler metal flow and alter the arc characteristics for deeper joint penetration. Pure helium is
commonly considered to be detrimental when used as a
shielding gas because it raises the current required for
spray arc transfer and increases weld spatter. Gases
other than argon or helium are not used; this excludes
oxygen, hydrogen, nitrogen, and carbon dioxide.
The fundamental principles of gas metal arc welding
(GMAW) of magnesium alloys are the same as for other
metals.10 Welding can be accomplished with this process at speeds that are two to three times faster than
speeds typical of gas tungsten arc welding, thereby
increasing filler metal deposition rates and reducing
10. Refer to Chapter 4, Gas Metal Arc Welding, in American Welding
Society (AWS) Welding Handbook Committee, 2004, Welding Processes, Part 1, ed. A. O’Brien, vol. 2, Welding Handbook, 9th ed.,
Miami: American Welding Society. See Appendix B of this volume for
a detailed description of chapter contents for the five volumes of
Welding Handbook, 9th ed.
Shielding Gas
Metal Transfer
Typical melting rates for standard sizes of magnesium
alloy electrodes using DCEP are shown in Figure 2.3,
156
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
AWS WELDING HANDBOOK
ELECTRODE FEED RATE, mm/s
0
100
700
400
500
600
700
800
D = 3.2 mm (0.125 in.)
D = 2.4 mm (0.094 in.)
D = 1.6 mm (0.062 in.)
SP
TRA RAY
NSF
ER
600
300
500
D = 1.2 mm (0.047 in.)
300
200
PUL
S
SP EDTRA RAY
NSF
ER
400
D = 1.0 mm
(0.040 in.)
SHO
STU
BBIN CIRC RTU
GT
RAN ITING
SFE
R
AVERAGE CURRENT, A (DCEP)
200
EXC
ESS
IVE
TUR ARC
BUL
ENC
E
800
0
200
400
600
800
1000
1200
1400
1600
1800
2000
ELECTRODE FEED RATE, in./min
Note: D = Electrode diameter.
Figure 2.3—Melting Rates for Bare Magnesium Alloy Electrodes Used with Argon Shielding
which also shows the relationship between electrode
feed rate and welding current for various wire diameters. The operating ranges for the three modes of metal
transfer used for GMAW, short-circuiting, pulsed-spray,
and spray transfer, are also shown in Figure 2.3.
The pulsed-spray transfer operating region occurs
between the spray transfer and short-circuiting transfer
regions and requires a special power source with pulsing capability. Without the pulsing function, the welding amperages between the short-circuiting and spray
transfer ranges would produce highly unstable globular
transfer, which is not suitable for welding magnesium
alloys.
The quality of welds made with the short-circuiting
transfer mode can be problematic because of the excessive spatter that results from gas metal arc welding of
magnesium and because of the highly reactive nature of
magnesium.
Like short-circuiting transfer, spray transfer is only
stable over a limited welding current range. Excessive
welding current causes arc turbulence, which must be
avoided.
The approximate ranges of arc voltage corresponding to each type of metal transfer are 13 V to 16 V for
short-circuiting transfer, 17 V to 25 V for pulsed-spray
transfer, and 24 V to 30 V for spray transfer.
AWS WELDING HANDBOOK
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
Equipment
Equipment (e.g., welding guns and wire feeders) used
for the gas metal arc welding of magnesium alloys is
similar to that used to weld other nonferrous alloys;
however, the selection of a power source requires special consideration. An appropriate power source is
needed to produce the preferred method of filler metal
transfer and also minimize spatter. A constant-current
(DCEP) power source is preferred for spray transfer and
should be operated at the lower end of the recommended current range for the applicable electrode size.
A wire feeder with a touch-start or slow run-in feature
is normally used. For pulsed-spray transfer, the power
source must be designed to produce two current levels,
with spray transfer taking place during the high pulse
157
current. For short-circuiting transfer, the new power
sources designed to stabilize the short-circuiting mode
can be helpful. These systems control either current
(i.e., reducing current in anticipation of the short circuit) or wire feed (i.e., wire retraction to assist detachment) to achieve more consistent metal transfer.
Welding Parameters
Typical parameters for gas metal arc welding of various
thicknesses of magnesium alloys are shown in Table 2.15.
These parameters can be used as guides when establishing welding conditions for a specific application. The
short-circuiting transfer mode is used for thin sections,
whereas the spray transfer mode is used for thick
Table 2.15
Typical Conditions for Gas Metal Arc Welding of Magnesium Alloysa
Electrode
mm
in.
Joint
Designb
No. of
Weld
Passes
0.6
1.0
1.6
2.3
3.2
4.1
4.8
0.025
0.040
0.062
0.090
0.125
0.160
0.190
A
A
A
A
B
B
B
1
1
1
1
1
1
1
1.0
1.0
1.6
1.6
2.4
2.4
2.4
1.6
3.2
4.8
6.4
0.062
0.125
0.190
0.250
A
A
A
C
1
1
1
1
1.0
1.6
1.6
2.4
Thickness
in./min
Pulse
Arc
Weldingc
Current
(DCEP),
A
140
230
185
245
135
165
205
—
—
—
—
—
—
—
13
14
14
16
14
15
15
25
40
70
95
115
135
175
152
119
201
123
360
280
475
290
55
55
52
55
21
24
25
29
50
110
175
210
224
121–131
135–152
140–157
140–157
530
285–310
320–360
330–370
330–370
—
—
—
—
—
27
24–30
24–30
24–30
24–30
240
320–350
360–400
370–420
370–420
Diameter
mm
Voltage
Feed Rate
in.
mm/s
Short-Circuiting Transfer
0.040
0.040
0.062
0.062
0.094
0.094
0.094
59.3
97.4
78.3
104
57.2
69.9
86.8
Pulsed-Spray Transfer
0.040
0.062
0.062
0.094
Spray Transfer
6.4
9.5
12.7
15.9
25.4
0.250
0.375
0.500
0.625
1.000
C
C
C
D
D
1
1
2
2
4
1.6
2.4
2.4
2.4
2.4
0.062
0.094
0.094
0.094
0.094
a. Argon shielding gas flow rate is 18.9 L/min to 28.3 L/min (40 ft3/h to 60 ft3/h) for short circuiting and pulsed spray; 23.6 L/min to 37.8 L/min (50 ft3/h to 80 ft3/
h) for spray transfer. Arc travel speed is 258 mm/s to 387 mm/s (24 in./min to 36 in./min). These conditions may also be used for fillet welds in
thicknesses of 6.4 mm to 25.4 mm (0.25 in. to 1.0 in.).
b. A—Square groove, no root opening.
B—Square groove, 2.3 mm (0.09 in.) root opening.
C—Single-V-groove, 1.5 mm (0.06 in.) root opening, 60° included-V.
D—Double-V-groove, 3.3 mm (0.13 in.) root opening, 60° included-V.
158
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
AWS WELDING HANDBOOK
sections and multiple-pass welds. Pulsed-spray transfer
is recommended for intermediate thicknesses or when
less heat input is preferred than is ideal for continuousspray transfer (e.g., to minimize distortion). Recommended electrode sizes for welding various thicknesses
of magnesium alloys are shown in Table 2.16. The lowest welding cost with both spray and pulsed-spray
transfer is achieved with the largest applicable electrode.
Electrodes for short-circuiting transfer are limited to
small sizes.
A ceramic ferrule is not needed. Helium shielding and
DCEP are used. The stud welding gun should be
equipped with controlled plunge to avoid excessive
spatter and undercutting of the base metal.
Typical conditions for welding AZ31B magnesium
alloy studs with diameters of 6.4 mm and 12.7 mm
(0.25 in. and 0.5 in.) to AZ31B plate and the average
breaking load of the welded studs are shown in Table
2.18. Figure 2.4 shows a cross section of a stud weld. In
general, the soundness of magnesium stud welds is very
similar to that of aluminum stud welds.
Gas Metal Arc Spot Welding
Gas metal arc spot welding can be used to join magnesium sheet and extrusions in a variety of thicknesses.
Welding schedules for suitable thickness combinations
of Alloy AZ31B are shown in Table 2.17. These parameters can be used as guides for developing weld schedules applicable to other magnesium alloys.
Commercially available gas metal arc spot welding
equipment is suitable for magnesium alloys. A constantpotential power source used with DCEP and argon
shielding is recommended. The strength of arc spot
welds made with GMAW can meet or exceed the
strength of resistance spot welds. Postweld stress relief
of gas metal arc spot welds is recommended for alloys
sensitive to stress corrosion cracking.
ARC STUD WELDING
The gas-shielded arc stud welding (SW) process used
for aluminum is also applicable to magnesium alloys.11
11. Refer to Chapter 9, Arc Stud Welding, in American Welding Society (AWS) Welding Handbook Committee, 2004, Welding Processes,
Part 1, ed. A. O’Brien, vol. 2, Welding Handbook, 9th ed., Miami:
American Welding Society. See Appendix B of this volume for a
detailed description of chapter contents for the five volumes of Welding Handbook, 9th ed.
STRESS RELIEVING
Residual stresses derived from welding or forming
can promote stress-corrosion cracking in magnesium
alloys that contain more than 1.5 wt % aluminum.
Thermal treatments are used with these alloys to reduce
residual stresses to safe levels to avoid this problem.
Other magnesium alloys are not as sensitive to this type
of cracking. Stress-corrosion cracking in welded structures usually occurs in the area adjacent to the weld
bead and is almost always trans-crystalline. Although
cracking can be delayed by using a surface coating, this
is a temporary solution and will not ensure crack-free
service for long periods. The weldment must be stress
relieved.
Stress relieving can be accomplished either in a furnace or with a torch. Heating in a furnace is preferred.
The time and temperature necessary to stress relieve
weldments for various alloys and product forms are
shown in Table 2.19. When a furnace is used, a fixture
should be used to support the weldment during heating
to prevent distortion. Ideally, the temperature of large
weldments should be monitored with thermocouples to
ensure that all sections reach the proper temperature.
With torch stress relieving, a temperature-indicating
device should be used to avoid overheating.
Table 2.16
Recommended Electrode Sizes for Gas Metal Arc Welding of Magnesium Alloys
Applicable Base Metal Thickness Range
Electrode Diameter
Short-Circuiting Transfer
Pulsed-Spray Transfer*
Spray Transfer*
mm
in.
mm
in.
mm
in.
mm
in.
1.0
1.1
1.6
2.4
0.040
0.045
0.062
0.094
0.8–1.5
1.0–1.8
1.5–2.3
2.3–4.8
0.03–0.06
0.04–0.07
0.06–0.09
0.09–0.19
1.5–2.3
1.8–3.0
2.5–6.4
5.1–7.9
0.06–0.09
0.07–0.12
0.10–0.25
0.20–0.31
4.1–6.4
4.8–6.4
5.1–7.6
≥ 7.6
0.16–0.25
0.19–0.25
0.20–.030
≥ 0.30
*Pulsed spray and spray transfer thickness schedules should provide good welding characteristics at minimum filler metal cost.
AWS WELDING HANDBOOK
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
159
Table 2.17
Typical Conditions for Gas Metal Arc Spot Welding of AZ31B Magnesium Alloy Sheet
Sheet Thickness
mm
in.
mm
in.
mm
in.
Welding
Current
(DCEP),
A
1.0
0.040
2.3
0.090
1.0
0.040
175
22–26
30–70
178–4826
40–1085
200
24–26
25–50
3405–5295
760–1190
22–26
40–100
1379–6138
310–1370
460–1710
Front
1.6
0.062
N/Spot
lb/Spot
0.040
175
200
22–28
20–90
2046–7606
4.8
0.190
1.0
0.040
175
22–26
40–100
222–5627
50–1265
200
22–28
20–100
1601–7672
360–1725
1.6
0.062
1.0
0.040
200
26
50–60
1548–3954
348–889
2.3
0.090
1.0
0.040
200
22–26
20–80
1112–3158
250–710
225
24–26
25–45
1601–3781
360–850
200
22–26
30–100
2291–5182
515–1165
225
22–28
20–100
1023–5960
230–1340
200
22–26
30–100
1112–3914
250–880
225
22–28
20–100
1423–8896
320–2000
2.3
4.8
0.125
Shear Strength
1.0
3.2
3.2
Weld Time,
Cyclesb
0.125
6.4
0.090
Arc
Voltage,
V
3.2
3.2
2.3
Electrode Diametera
Back
3.2
4.0
4.8
0.125
0.250
0.090
0.125
0.190
0.125
0.156
0.190
1.0
0.040
1.0
0.040
1.0
0.040
250
24–28
50–100
2282–5022
513–1129
1.6
0.062
275
25–28
40–90
1397–4795
314–1078
1.6
0.062
275
22–26
30–100
2313–4715
520–1060
300
24–28
25–80
1023–4271
230–960
275
22–26
30–100
1290–7562
290–1700
300
22–28
20–100
890–7562
200–1700
325
24–27
40–100
2593–7450
583–1675
350
24–25
40–100
3024–5947
680–1337
350
22–26
30–100
2357–8340
530–1875
375
24–26
30–80
2847–7116
640–1600
350
22–24
30–100
845–8451
190–1900
375
24–28
30–100
1200–7295
270–1640
1.6
0.062
2.4
0.094
2.4
0.094
2.4
0.094
4.0
0.156
4.0
0.156
2.4
0.094
375
24–26
80–150
2300–6392
517–1437
4.8
0.190
4.8
0.190
2.4
0.094
375
24–26
80–150
3479–5885
782–1323
400
24–26
60–110
3794–5311
853–1194
a. AZ61A electrode.
b. 60 Hz.
Table 2.18
Typical Welding Conditions and Breaking Loads for AZ31B-F
Magnesium Alloy Studs Joined to 6.4 mm (0.25 in.) AZ31B-O Alloy Plate
Stud Diameter
Welding
Current,a A
Weld Time,b
cycles
Lift
in.
mm
Avg. Breaking Load
mm
in.
6.4
0.250
125
45
3.2
0.125
6.4
0.250
6.80
1530
12.7
0.500
375
40
3.2
0.125
4.8
0.188
18.25
4100
a. DCEP and helium shielding.
b. 60 Hz.
mm
Plunge
in.
kN
lb
160
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
AWS WELDING HANDBOOK
POSTWELD HEAT TREATMENT
Repair-welded castings often require heat treatment to
obtain the essential properties. The appropriate postweld
heat treatment depends on the temper of the casting
before welding and the preferred temper after welding
(refer to Table 2.12). Because of the fine grain size and
fine dispersion of precipitates in the weld metal relative to
the casting, aluminum-containing castings in the T4 or
T6 condition can be solution-heat treated for relatively
short heating times after welding. In the case of castings
of Alloys AM100A, AZ81A, AZ91C, and AZ92A, the
solution heat-treating time must not exceed 30 minutes at
temperature to avoid excessive grain growth in the weld.
A protective atmosphere must be used when the solutiontreating temperature is above 400°C (750°F) to prevent
excessive oxidation. The postweld heat treatment specified for various alloys will produce the best weldment
properties and also relieve stress in castings, which will
prevent stress-corrosion cracking. Even if a postweld
solution or temper heat treatment is not required, aluminum-containing castings should be stress relieved.
WELD MICROSTRUCTURE
Examples of typical microstructures observed in
wrought Alloy AZ31 (magnesium-aluminum-zinc) are
illustrated in the transverse cross section of a weld
Figure 2.4—Typical Arc
Stud Weld in Alloy AZ31B
Table 2.19
Recommended Stress-Relieving Heat Treatments for Magnesium Alloys
Castings
Sheet
Temperature
Extrusions
Temperature
Alloy
°C
°F
Time,
min
AM100A
260
500
AZ63A
260
AZ81A
Temperature
Alloy
°C
°F
Time,
min
Alloy
°C
°F
Time,
min
60
AZ31B-O
260
500
15
AZ10A-F
260
500
15
500
60
AZ31B-H24
149
300
60
AZ31B-F
260
500
15
260
500
60
M1A-O
260
500
15
AZ61A-F
260
500
15
AZ91C
260
500
60
M1A-H24
204
400
60
AZ80A-F
260
500
15
AZ92A
260
500
60
HK31A-H24
316
600
30
AZ80A-T5
204
400
60
—
—
—
—
HM21A-T81
399
750
30
HM31A-T5
427
800
60
—
—
—
—
—
—
—
—
M1A-F
260
500
15
—
—
—
—
—
—
—
—
ZK21A-F
204
400
60
—
—
—
—
—
—
—
—
ZK60A-F
260
500
15
—
—
—
—
—
—
—
—
ZK60A-T5
149
300
60
AWS WELDING HANDBOOK
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
shown in Figure 2.5(A). Metallographic specimens were
prepared by polishing with colloidal silica slurry and
etching in an acetic-picric acid solution. Figure 2.5(A)
shows partially recrystallized, equiaxed grains with an
average diameter of 8 μm. Some grains remain elongated as a result of roll processing during manufacture.
The matrix phase consists of α-phase magnesium, solid-
(A)
Weld Metal
HAZ
(B)
Source: Kishore, N., N. K. Babu, and C. E. Cross, 2009, Influence of Variable Polarity
Pulsed Current Technique on Grain Refinement of AZ31 Weldments, in Proceedings, 8th
International Conference, Magnesium Alloys and Their Applications, Weimar, Wiley, BC
H, 996–1003.
Figure 2.5—Microstructure of AZ31 GTA
Weld Showing Transverse Cross-Section
of (A) Wrought AZ31 Base Metal, and
(B) Weld Metal (Upper Section)
and HAZ (Lower Section)
161
solution strengthened with aluminum. Within these αphase grains are coarse angular particles that are intermetallic compounds of aluminum and manganese (e.g.,
Al8Mn5, Al6Mn, and AlMnSi). Figure 2.5(B) shows the
transition from the heat-affected zone (HAZ) to the
weld metal. Recrystallization and non-uniform grain
growth is observed in the HAZ, resulting in grain sizes
up to 100 μm.
The microstructure of the weld metal has equiaxed
grains that have an average diameter of 60 μm. The
interdendritic eutectic β-phase (Mg17Al12) is distributed
uniformly (often in rows) within grains. Epitaxial
grains are observed along the weld interface. The
amount of eutectic β-phase in the weld metal will
increase with aluminum content, as determined by filler
metal selection and weld dilution. This is demonstrated
in Figure 2.6, which shows weld metal from two AZ31
weldments containing different amounts of aluminum.
The twinning observed in Figure 2.6(A) is likely an artifact from polishing.
Particles of aluminum-magnesium compounds and
β-phase can be observed in the HAZ, with the β-phase
providing evidence of partial melting. This is demonstrated in Figure 2.7, where a scanning electron micrograph shows the existence of a partially melted zone
(PMZ) within the HAZ adjacent to the weld interface.
Other magnesium alloys exhibit weld microstructures similar to those of AZ31. Typical microstructures
of the base metal and the weld interface of Alloy
HK31A–H24 are shown in Figure 2.8. Figure 2.9 shows
typical microstructures of the base metal and weld
interface of HM21A-T8. Typical microstructures of the
base metal and weld interface of Alloy HM31A-T5 are
illustrated in Figure 2.10. Two of these alloys (excluding HM21A, which recrystallized prior to welding)
showed a significant amount of recrystallization and
grain growth in the HAZ.
Radiographs of welds in alloys containing rare earths
and thorium will often show segregation along the
edges of the weld metal, as shown in Figure 2.11. This
segregation is caused by incipient melting in the HAZ.
A white line will appear along the weld interface
because of the x-ray absorptive characteristics of the
rare earths and thorium segregation.
WELD CORROSION
Because of the reactive nature of magnesium, consideration of any practical use of this metal must take into
account the possibility for corrosion. This is particularly true for galvanic couples formed by contact with
dissimilar metals because of the highly anodic corrosion
potential of magnesium relative to all other structural
metals. Galvanic couples can also form within a magnesium weldment; examination of the HAZ and weld
162
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
AWS WELDING HANDBOOK
(A) Area Fraction of β-Phase, 5%
(B) Area Fraction of β-Phase, 20%
Source: Cross, C. E, N. Winzer, S. Bender, and D. Eliezer, 2011, Welding in the World, 55, 7-8, 40–47.
Figure 2.6—Experimentally Controlled Aluminum Content of
AZ31 Weld Metal (A) Containing 1.6 wt % Aluminum and
(B) Containing 4.9 wt % Aluminum
WM
PMZ
BM
Figure 2.7—Weld Interface Showing
AZ31 Weld Metal, Partially Melted
Zone, and Base Metal
metal often reveals a slightly anodic condition relative
to the base metal. While this localized attack would
usually be considered detrimental, the HAZ and weld
metal rapidly passivate, thus transferring more uniform
corrosion to the base metal.
Galvanic couples also occur on a microscopic scale,
where intermetallic particles have been shown to be
cathodic relative to the magnesium matrix. Immersion
in an electrolyte leads to corrosive pitting at the surface,
whereby magnesium is preferentially dissolved around
each particle. Modern magnesium alloys are purposely
produced containing low impurity levels of nickel, iron,
copper, and silicon to minimize intermetallic particles and
mitigate pitting.
MECHANICAL PROPERTIES OF WELDS
The mechanical properties of gas tungsten arc welds
discussed in this section include tensile strength and
fatigue. The effect of various welding conditions on
mechanical properties is described.
AWS WELDING HANDBOOK
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
(A)
163
(B)
Figure 2.8—(A) Microstructure of 3.18 mm (0.125 in.) Thick HK31A-H24 Magnesium
Sheet (Base Metal), Magnified 250X, and (B) Microstructure of Weld Interface between
the HK31A Heat-Affected Zone and EZ33A Weld Metal, Magnified 100X
Weld Metal
(A)
Base Metal
(B)
Figure 2.9—(A) Microstructure of 3.18 mm (0.125 in.) Thick HM21A-T8 Magnesium Sheet,
Magnified 250X, and (B) Microstructure of Weld Interface between the HM21A
Heat-Affected Zone and EZ33A Weld Metal, Magnified 100X
Tensile Properties
Typical tensile strength properties at room temperature for gas tungsten arc welds in wrought and cast magnesium alloys are shown in Table 2.20. Typical tensile
strength properties at elevated temperature are shown in
Table 2.21. The properties of joints made by gas metal
arc welding are comparable to these strengths, depend-
ing on heat input and weld quality requirements. Table
2.22 shows the tensile properties of the weld metal of
magnesium alloys produced by several filler-metal and
base-metal combinations. The strength of welds in most
magnesium alloys is similar to those of the base metal.
This can be demonstrated by comparing the yield
strength data for welded joints shown in Table 2.20 with
similar data for base metals (refer to Table 2.5).
164
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
(A)
AWS WELDING HANDBOOK
(B)
Figure 2.10—(A) Microstructure of 3.18 mm (0.125 in.) Thick HM31A-T5 Magnesium
Extrusion, Magnified 500X, and (B) Microstructure of Weld Interface between the HM31A
Heat-Affected Zone and EZ33A Weld Metal (Left) and Base Metal (Right), Magnified 100X
weld metal will increase with increased aluminum
content as controlled by the filler alloy selected and by
the amount of weld dilution. The primary effect of
aluminum, in this case, is to refine the grain size of the
weld metal, as indicated in Figure 2.13.
Fatigue Properties. When welded components are
to be exposed to cyclic loading during service (e.g.,
typical of automotive applications) weld fatigue
life becomes an important design consideration. Most
magnesium alloys display a fatigue limit that is
roughly 50% of the ultimate tensile strength, and
the fatigue limit of the weld can be as low as 50%
of the fatigue limit of the base metal. Fatigue
failure is normally trans-granular and involves quasicleavage. The reduction in fatigue life and
strength associated with weldments is influenced by
the following conditions:
Figure 2.11—Microstructure of the Weld Interface
in an EZ33A Magnesium Alloy Casting Showing
Pools of a Eutectic (Base Metal on Right)
Magnified 100X
When the base metal is in the strain-hardened condition, recrystallization and some grain growth will take
place in the heat-affected zone during welding; thus, the
HAZ will be weaker than the base metal. The pattern of
hardness traverse shown in Figure 2.12 is typical for a
weld made in wrought AZ31 base metal using an AZ61
filler metal with GTAW process. The hardness of the
1. Residual tensile stress in the weld area;
2. Presence of stress risers such as weld undercut,
porosity, or cracks;
3. Coarse grains in the HAZ, and
4. Low-strength weld metal.
In addition, even when fatigue occurs under ambient
conditions, this can be considered a form of corrosionfatigue because oxidation at the fatigue crack can
strongly influence in-service performance. Therefore,
factors such as humidity, positive load ratio, and high
load frequency can adversely affect fatigue in ambient
air. When fatigue occurs in a corrosive saline
environment, a fatigue limit no longer exists because
AWS WELDING HANDBOOK
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
165
Table 2.20
Typical Tensile Properties of Gas Tungsten Arc Welds in Magnesium Alloys at Room Temperature
Yield Strength*
Tensile Strength
Alloy and
Temper
Filler Metal
MPa
ksi
MPa
ksi
% Elongation in
51 mm (2 in.)
Joint Efficiency,
%
Sheet
AZ31B-O
AZ61A,AZ92A
241–248
35–36
117–131
17–19
10–11
95–97
AZ31B-H24
AZ61A,AZ92A
248–255
36–37
131–152
19–22
5
86–88
HK31A-H24
EZ33A
214–221
31–32
138–152
20–22
2–4
82–84
HM21A-T8
EZ33A
193–214
28–31
131–138
19–20
2–4
80–89
ZE41A-T5
ZE41A
207
30
138
20
4
100
ZH62A-T5
ZH62A
262
38
172
25
5
95
6–9
91–94
Extrusions
AZ10A-F
AZ61A, AZ92A
221–228
32–33
103–124
15–18
AZ31B-F
AZ61A, AZ92A
248–255
36–37
131–152
19–22
5–7
95–97
AZ61A-F
AZ61A, AZ92A
262–276
38–40
145–165
21–24
6–7
84–89
AZ80A-F
AZ61A
248–276
36–40
152–179
22–26
3–5
74–82
AZ80A-T5
AZ61A
234–276
34–40
165–193
24–28
2
62–73
HM31A-T5
ZK21A-F
EZ33A
193–214
28–31
131–165
19–24
1–2
64–70
AZ61A, AZ92A
221–234
32–34
117
17
4–5
76–81
—
—
2
77
Castings
AZ63A-T6
AZ92A, AZ101A
214
31
AZ81A-T4
AZ101A
234
34
90
13
8
85
AZ91C-T6
AZ101A
241
35
110
16
2
87
AZ92A-T6
AZ92A
241
35
145
21
2
87
EZ33A-T5
EZ33A
145
21
110
16
2
100
HK31A-T6
HK31A
200
29
110
16
9
94
HZ32A-T5
HZ32A
200
29
117
17
5
97
K1A-F
EZ33A
159
23
55
8
10
100
*0.2% offset in a 51 mm (2 in.) gauge length.
For gas tungsten arc welds made on wrought AZ31,
fatigue in air normally initiates in the coarse-grained
HAZ and propagates through the weld metal. A
Wöhler fatigue curve (stress cycles) for this type of
weldment is shown in Figure 2.14. Also shown is the
curve corresponding to fatigue in a 3.5 wt % sodium
chloride solution, where fatigue cracks initiate prematurely at corrosion pits and extensive dissolution occurs
over long periods of time, reducing the ability to sustain
loading.
RESISTANCE WELDING
Resistance welding (RW) includes several processes
and variations that are applicable to the welding of
magnesium alloys: resistance spot welding (RSW), resistance seam welding (RSEW), and flash welding (FW).
Sources of further information on these processes
include Recommended Practices for Resistance Welding,
166
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
AWS WELDING HANDBOOK
Table 2.21
Typical Tensile Properties of Gas Tungsten Arc Welds in Magnesium Alloys at Elevated Temperatures a
Test Temperature
Alloyb
Filler Metal
°C
°F
Tensile Strength
MPa
ksi
Yield Strengthd
MPa
ksi
% Elongation in
51 mm (2 in.)
Joint
Efficiency,
%
Sheet
HK31A-H24
HM21A-T8
EZ33A
EZ33A
204
400
145
21
90
13
18
88
316
600
90
13
69
10
24
100
204
400
124
18
83
12
16
100
316
600
97
14
69
10
14
93–100
Extrusions
HM31A-T5
EZ33A
204
400
144
21
83
12
22
87
316
600
90
13
62
9
27
72
Castings
a.
b.
c.
d.
EZ33A-T5
EZ33A
HK31A-T6
HK31Ac
HZ32A-T5
HZ32Ac
204
400
131
19
76
11
13
90
316
600
76
11
48
7
50
92
204
400
124
18
76
11
33
82
316
600
103
15
62
9
25
79
204
400
131
19
90
13
33
100
316
600
83
12
69
10
26
92
Weld reinforcement removed.
Alloys designed for elevated-temperature service.
EZ33A filler metal will provide joint strength equivalent to base metal.
0.2% offset in a 51 mm (2 in.) gauge length.
Table 2.22
Tensile Properties of Magnesium Alloy Weld Metal
Produced from Various Combinations of Filler Metal and Base Metal
Ultimate Tensile Strength
Tensile Yield Strength*
Filler Metal
Base Metal
MPa
ksi
MPa
ksi
% Elongation in
51 mm (2 in.)
AZ61A
AZ31B
236
34.3
100
14.5
10.0
AZ92A
AZ31B
254
36.8
130
18.9
8.0
EZ33A
HK31A
221
32.0
123
17.8
9.0
EZ33A
HM31A
185
26.8
137
19.8
3.5
EZ33A
HM21A
207
30.0
146
21.2
6.3
HK31A
HM31A
179
26.0
95
13.8
10.5
HK31A
HM21A
186
27.0
95
13.8
13.3
*0.2% offset in a 51 mm (2 in.) gauge length.
AWS WELDING HANDBOOK
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
Source: Cross, C. E., P. Xu, N. Winzer, S. Bender, and D. Eliezer, 2011, Corrosion and Corrosion-Fatigue of AZ31 Magnesium
Weldments, Welding in the World, 55 (7-8) 40–47.
Figure 2.12—Pattern of Hardness in a Cross Section
of a Gas Tungsten Arc Weld in Wrought AZ31
Made with Alloy AZ61 Filler Metal
80
70
60
50
40
30
1
2
3
4
5
6
ALUMINUM CONTENT (WT %)
Source: Adapted from Babu, N. K., and C. E. Cross, 2012, Influence of Aluminum
Content on Grain Refinement and Strength of AZ31 Magnesium GTAW Weld Metal, Conference Proceedings, 9th International Trends in Welding Research, ASM International,
91–97.
Figure 2.13—Weld Metal Grain Size
Relative to Aluminum Content
167
168
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
AWS WELDING HANDBOOK
Source: Xu, P., N. Winzer, S. Bender, and C. E. Cross, 2009, Investigation of Corrosion-Fatigue Behavior of AZ31 Wrought
Magnesium Weldments, in Proceedings, 8th International Conference, Magnesium Alloys and their Applications, Weimar,
Wiley-VCH. 858–865.
Figure 2.14—Stress-Cycle (S/N) Fatigue Curves for a Weldment in
Alloy AZ31 Tested in Air and a 3.5 wt % Saline Solution
AWS C1.1M/C1.1:2012 and the Welding Handbook,
Volume 3, published by the American Welding Society
(AWS).12 The Resistance Welding Manufacturing
Alliance (RMWA) is a valuable source of detailed
information.13
RESISTANCE SPOT WELDING
Magnesium alloys in sheet and extruded forms in
thicknesses ranging from 0.5 mm to 3.3 mm (0.02 in. to
0.13 in.) can be joined by resistance spot welding
(RSW). Spot welding is used for low-stress magnesium
applications in which vibration is low or nonexistent
and welding procedures similar to those used for aluminum alloys are employed. Magnesium alloys recom12. Refer to Chapters 1, Arc Power Sources; 3, Gas Tungsten Arc
Welding; and 4, Gas Metal Arc Welding, in American Welding Society
(AWS) Welding Handbook Committee, 2007, Welding Processes, Part
2, ed. A. O’Brien and C. Guzman, vol. 3, Welding Handbook, 9th ed.,
Miami: American Welding Society. See Appendix B of this volume for
a detailed description of chapter contents for the five volumes of
Welding Handbook, 9th ed.
13. Refer to Chapters 1, 2, 4, and 5 in Resistance Welding Manufacturing Alliance (RWMA), 2003, Resistance Welding Manual, 4th ed,
Philadelphia: RWMA.
mended for spot welding include M1A, AZ31B,
AZ61A, HK31A, HM21A, HM31A, and ZK60A.
Preweld Cleaning
Careful preweld cleaning is essential for the production of spot welds of consistent size and soundness. A
uniform electrical surface resistance of about 50 μΩ or
less is necessary to obtain consistency. Chemically
cleaned workpieces will maintain a low consistent surface resistance for about 100 h when stored in a sufficiently clean and dry environment; however, the time
between cleaning and welding for critical applications
should be limited to 24 h or less. Mechanically cleaned
surfaces will develop progressively higher inconsistency
of surface resistance after 8 h to 10 h and should be
spot welded within this time frame. (Refer to Table 2.9
for chemical cleaning procedures for spot welding.)
Equipment
Because of the relatively high thermal and electrical
conductivity of magnesium alloys, high welding currents and short weld times are required for spot welding
AWS WELDING HANDBOOK
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
of these alloys. Spot welding machines designed for aluminum alloys are suitable for welding of magnesium.
As with aluminum, very rapid electrode force follow-up
is required to maintain pressure on the weld nugget as
the metal softens and rapidly deforms. For this reason,
low-inertia welding machines should be used. Although
a dual-force system is not an absolute requirement for
spot welding magnesium alloys, applying a higher forging force on the nugget during solidification sometimes
helps to reduce internal discontinuities. Correct timing
of the application of forging force is important to
achieving this reduction.
Electrodes
Spot welding electrodes for magnesium alloys should
be made from specific copper alloys: Group A, Class 1
or Class 2, as designated by the Resistance Welding
Manufacturing Alliance (RWMA). The faces of the electrodes must be kept clean and smooth to minimize the
contact resistance between the electrode and the adjacent workpiece. Cleaning should be done with
an electrode dressing tool with a matching face
contour covered with a very fine polishing cloth (i.e.,
280 grit).
Electrode service life between cleanings is limited by
the transfer of copper to the workpiece and subsequent
sticking of the electrode. The number of welds that can
be produced between cleaning depends on the method
of base metal cleaning, the composition of the magnesium alloy, the electrode alloy, welding conditions, and
cooling efficiency. Table 2.23 shows the relative effect
of mechanical and chemical surface preparations on
electrode service life for some magnesium alloys. Chemical cleaning is more effective than wire brushing for
extending electrode service life. The longest electrode
service life is obtained when the welding conditions
produce a weld nugget no larger than that necessary to
meet strength requirements of the specific design.
Copper pickup on spot welded surfaces of magnesium increases susceptibility to corrosion. Therefore,
any copper residue should be completely removed from
the abraded surfaces by a suitable mechanical cleaning
method. The presence of copper on spot welds can be
determined by applying a 10% acetic acid solution; any
dark spots will indicate the presence of copper.
Joint Design
Joint designs for the resistance spot welding of magnesium-alloy sheet are much the same as those for aluminum alloy sheet. Minimum recommended spot
spacing and edge distance for the location of spot welds
are shown in Table 2.24. When two unequal sheet
thicknesses are to be spot welded, the thickness ratio
should not exceed 2.5:1. With three different sheet
thicknesses, the thickness variation should not exceed
25%, and the thickest section should be in the center.
Welding Schedules
The following variables should be considered when
developing a welding schedule:
1. Dimensions, properties, and characteristics of
the alloys to be welded,
2. Type of welding equipment to be employed, and
3. Joint design.
A welding schedule can be established for any
particular combination of these factors. Typical schedules
for spot welding magnesium alloys with three-phase
frequency converter machines are shown in Table
2.25. Schedules for spot welding magnesium alloys with
Table 2.23
Effect of Surface Preparation on Spot Welding Electrode Life with Magnesium Alloys
No. of Spot Welds between Electrode Cleaning and Cleaning Method
Spot Weld Cleaner
Alloy
Electrode Classification
RWMA Group A
Wire Brushing
No. 2 Bath*
No. 3 Bath*
AZ31B
Class 1
30
over 200
over 550
AZ31B
Class 2
15
50
270
HK31A
Class 2
40
400
195
HM21A
Class 2
5
80
5
*Refer to Table 2.9 for composition of cleaning solutions.
169
170
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
AWS WELDING HANDBOOK
Table 2.24
Suggested Spot Spacing and Edge Distance for Spot Welds in Magnesium Alloys
Spot Spacing
Thickness*
Minimum
Edge Distance
Nominal
Minimum
Nominal
mm
in.
mm
in.
mm
in.
mm
in.
mm
in.
0.5
0.020
6.4
0.25
12.7
0.50
5.6
0.22
7.9
0.31
0.31
0.6
0.025
6.4
0.25
12.7
0.50
5.6
0.22
7.9
0.8
0.032
7.9
0.31
15.7
0.62
6.4
0.25
9.1
0.36
1.0
0.040
9.7
0.38
19.0
0.75
7.1
0.28
9.7
0.38
1.3
0.050
11.2
0.44
20.3
0.80
7.9
0.31
10.4
0.41
1.6
0.062
12.7
0.50
25.4
1.00
9.7
0.38
12.2
0.48
2.0
0.080
16.0
0.63
31.7
1.25
11.2
0.44
13.7
0.54
2.5
0.100
22.3
0.88
38.1
1.50
11.9
0.47
14.2
0.56
3.2
0.125
23.9
0.94
44.5
1.75
14.2
0.56
17.0
0.67
*Thinner section if thicknesses are unequal.
phase ac machines are shown in Table 2.26. Table 2.27
lists schedules for spot welding magnesium Alloy
AZ31B with capacitor-discharge stored-energy machines.
Table 2.28 shows schedules for spot welding magnesium Alloy AZ31B with dc rectifier machines. This data
is intended only as a guide for establishing schedules for
specific applications. The welding and postheating currents are approximate values. The magnitude of the
welding current is adjusted by transformer taps or
phase shift heat control, or both. The required current
can be obtained by starting with a low value of weld
heat and a corresponding percentage of postheating.
The current is gradually increased until the preferred
nugget diameter, penetration, and shear strength are
obtained. In some cases, it may be necessary to readjust
the weld time to achieve the required properties.
With single-phase ac equipment, welding current can
be determined by primary or secondary measurement
methods. The diameter of the spot weld nuggets and the
minimum indicated shear strength, shown in Table
2.28, should be obtained when the measured welding
current is within 5% of the listed value.
Timing of the application of forging force is very
important when dual electrode force is used. If the forging force is applied too late, the temperature of the
nugget will be too low to consolidate the nugget. If the
forging force is applied too soon, the nugget size may be
too small or the electrode indentation may be excessive.
Insufficient electrode force can cause weld metal expulsion, internal discontinuities in the nugget, surface
burning, or excessive electrode sticking. Excessive elec-
trode force is indicated by deep electrode indentation,
large sheet separation and distortion, or unsymmetrical
weld nuggets.
Weld-nugget diameter and depth of fusion can be
determined by preparing a test specimen by sectioning
through the center of the nugget. The exposed edge
is polished and then etched with a 10% acetic or
tartaric acid solution. When the specimen is viewed,
it should confirm that the depth of fusion is uniform
in equal sheet thicknesses. If it is not uniform, subsequent welds may require the use of an electrode with a
smaller radius placed against the side with the least
penetration. It may be necessary to clean the electrodes
more frequently or to clean the workpiece surfaces more
thoroughly.
When using the resistance spot welding process to
join dissimilar magnesium alloys, differences in thermal
and electrical conductivity can be compensated for by
using an electrode with a smaller radius in contact with
the alloy that requires the higher heat input. For example, to center the weld nugget in a joint between equal
thicknesses of M1A and AZ31B sheets, a smaller radius
face should be used against the M1A alloy.
Second-phase particles in magnesium-base material
have been shown to affect the microstructure of the
fusion zone and joint strength in resistance spot welds.
With a columnar-to-equiaxed transition (CET), there is
an increase in the fraction of equiaxed grains and an
improvement in joint strength. For example, studies
(Xiao et al.) have indicated that if Al 8Mn5 particles are
big enough, heterogeneous nucleation occurs ahead of
0.040
0.050
0.062
0.080
0.125
0.125
0.040
0.050
0.062
0.071
0.090
0.125
0.125
1.0
1.3
1.6
2.0
3.2
3.2
1.0
1.3
1.6
1.8
2.3
3.2
3.2
22.2
22.2
19.1
15.9
15.9
15.9
12.7
19.1
22.2
19.1
19.1
15.9
12.7
22.2
22.2
15.9
22.2
15.9
15.9
15.9
15.9
12.7
12.7
0.88
0.88
0.75
0.62
0.62
0.62
0.50
0.75
0.88
0.75
0.75
0.62
0.50
0.88
0.88
0.62
0.88
0.62
0.62
0.62
0.62
0.50
0.50
0.50
152
152
102
102
102
76
76
152
152
102
102
102
76
152
102
102
102
102
102
102
76
76
76
76
mm
6
6
4
4
4
4
3
6
6
4
4
4
3
6
4
4
4
4
4
4
3
3
3
3
in.
Face Radius
a. Two equal thicknesses.
b. Spherical radius-faced electrodes on both sides.
c. Cycles of 60 Hz.
0.125
3.2
0.062
1.6
0.090
0.050
1.3
2.3
0.050
1.3
0.062
0.040
1.0
0.062
0.032
0.8
1.6
0.025
0.6
1.6
0.020
0.5
12.7
mm
in.
mm
in.
Diameter
Thicknessa
Electrodeb
905
1725
1360
995
725
545
360
1090
2270
1540
1090
635
454
2040
905
545
545
795
725
635
545
454
360
360
kg
800
800
lb
2000
3800
3000
2200
1600
1200
800
2400
5000
3400
2400
1400
1000
4500
2000
1200
1200
1750
1600
1400
1200
1000
Weld
1630
—
—
—
—
—
—
1450
—
—
—
—
—
—
1950
870
1770
—
—
1590
—
—
—
—
kg
—
—
—
—
lb
3600
—
—
—
—
—
—
3200
—
—
—
—
—
—
4300
1920
3900
—
—
3500
Forge
Electrode Force
5
—
—
—
—
—
—
HM21A Alloy
2
—
—
—
—
—
HK31A Alloy
—
2
3
3
—
—
2
—
—
—
—
AZ31B Alloy
5
5
4
4
3
2
1
5
5
4
3
2
1
5
3
3
3
3
2
2
1
1
1
1
6
2
2
2
2
2
2
6
6
1
1
2
1
6
1
1
1
1
1
2
2
2
1
2
—
—
—
—
—
—
—
—
—
—
—
—
—
—
5
6
—
—
—
5
—
—
2
—
Forge Weld Heat
Delay or Pulse
Post-heat
No. of
Time,
Time,
Time,
cyclesc cyclesc Pulses cyclesc
56 500
66 700
53 200
47 400
40 600
30 700
21 600
50 900
65 900
50 500
39 400
31 600
19 600
66 900
42 700
43 600
43 600
35 200
31 000
29 000
28 300
26 400
20 200
25 400
Weld
—
—
—
—
—
—
—
—
—
—
—
—
—
—
15 000
24 800
—
—
—
10 300
—
—
4000
—
Postheat
Approximate
Current, A
9.4
8.1
6.6
7.4
5.8
5.3
4.6
9.4
8.4
7.4
6.4
5.8
4.3
11.7
6.6
7.4
6.4
5.6
4.8
4.8
5.3
5.1
3.6
4.8
mm
0.37
0.32
0.26
0.29
0.23
0.21
0.18
0.37
0.33
0.29
0.25
0.23
0.17
0.46
0.26
0.29
0.25
0.22
0.19
0.19
0.21
0.20
0.14
0.19
in.
Nugget
Diameter
Table 2.25
Schedules for Spot Welding Magnesium Alloys with Three-Phase Frequency Converter Machines
6250
5250
4225
3425
2490
2090
1580
6140
5780
3960
2935
2355
1380
9320
4050
3560
3070
2580
1955
1935
1890
1470
890
865
N
1405
1180
950
770
560
470
355
1380
1300
890
660
530
310
2095
910
800
690
580
440
435
425
330
200
195
lb
Min. Average
Shear Strength
AWS WELDING HANDBOOK
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
171
0.016
0.020
0.025
0.032
0.040
0.050
0.062
0.071
0.080
0.090
0.100
0.125
0.016
0.020
0.025
0.032
0.040
0.050
0.060
0.071
0.080
0.090
0.100
0.125
0.4
0.5
0.6
0.8
1.0
1.3
1.6
1.8
2.0
2.3
2.5
3.2
0.4
0.5
0.6
0.8
1.0
1.3
1.5
1.8
2.0
2.3
2.5
3.2
12.7
12.7
12.7
12.7
12.7
12.7
12.7
9.5
9.5
9.5
9.5
9.5
12.7
12.7
12.7
12.7
12.7
12.7
12.7
12.7
9.5
9.5
9.5
9.5
mm
in.
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.38
0.38
0.38
0.38
0.38
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.38
0.38
0.38
0.38
Diameter
a. Two equal thicknesses.
b. Spherical radius-faced electrodes on both sides.
c. Cycles of 60 Hz.
in.
mm
Thicknessa
152
152
102
102
102
102
102
76
76
76
76
51
152
152
102
102
102
102
102
76
76
76
76
51
6
6
4
4
4
4
4
3
3
3
3
2
6
6
4
4
4
4
4
3
3
3
3
2
in.
Face Radius
mm
Electrodeb
430
340
315
295
270
250
225
205
180
160
135
135
455
360
340
315
295
270
250
225
205
180
160
135
kg
950
750
700
650
600
550
500
450
400
350
300
300
M1A Alloy
1000
800
750
700
650
600
550
500
450
400
350
300
AZ31B Alloy
lb
Electrode Force
14
12
11
10
9
8
7
6
5
4
3
3
12
10
9
8
7
6
5
5
4
3
3
2
Weld Time,
cyclesc
45 000
38 000
36 000
35 000
33 000
32 000
30 000
28 000
26 000
24 000
20 000
17 000
42 000
36 000
34 000
33 000
32 000
31 000
29 000
26 000
24 000
22 000
18 000
16 000
Approx.
Welding
Current,
A
8.9
7.9
7.4
7.1
6.6
6.1
5.3
4.6
4.1
3.6
3.0
2.0
9.7
8.6
8.1
7.9
7.4
6.9
5.8
5.1
4.6
4.1
3.6
2.5
mm
0.35
0.31
0.29
0.28
0.26
0.24
0.21
0.18
0.16
0.14
0.12
0.08
0.38
0.34
0.32
0.31
0.29
0.27
0.23
0.20
0.18
0.16
0.14
0.10
in.
Nugget Diameter
Table 2.26
Schedules for Spot Welding Magnesium Alloys with Single-Phase AC Machines
3560
3025
2490
2200
1915
1710
1310
1000
780
580
425
310
4805
3850
3425
3070
2715
2425
1915
1535
1200
955
780
620
N
800
680
560
495
430
385
295
225
175
130
95
70
1080
865
770
690
610
545
430
345
270
215
175
140
lb
Min. Average
Shear Strength
172 CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
AWS WELDING HANDBOOK
0.040
0.051
0.064
0.100
0.125
0.5
1.0
1.3
1.6
2.5
3.2
mm
22.2
19.1
15.9
15.9
12.7
12.7
Diameter
0.020
0.032
0.040
0.051
0.064
0.081
0.093
0.102
0.125
0.5
0.8
1.0
1.3
1.6
2.1
2.4
2.6
3.2
22.2
22.2
22.2
22.2
15.9
15.9
15.9
15.9
15.9
mm
0.88
0.88
0.88
0.88
0.62
0.62
0.62
0.62
0.62
in.
Diameter
0.88
0.75
0.62
0.62
0.59
152
152
152
102
102
76
76
76
76
mm
6
6
6
4
4
3
3
3
3
in.
Face Radius
Electrodeb
a. Two equal thicknesses.
b. Spherical radius-faced electrodes on both sides.
c. Cycles of 60 Hz.
in.
mm
Thicknessa
in.
0.59
152
152
102
102
76
76
mm
Tip Radius
6
6
4
4
3
3
in.
1030
490
490
380
330
295
kg
2275
1800
1080
835
725
650
lb
Electrode Force
2.2
2.2
2.2
2.2
2.2
1.4
Charging
Voltage,
kV
9.6
8.6
6.9
5.8
5.1
3.6
mm
575
475
440
390
315
265
215
180
135
kg
970
860
700
580
480
400
300
lb
1270
1050
Weld
1260
1050
975
855
700
575
455
400
270
kg
880
600
lb
2780
2320
2150
1890
1540
1270
1000
Forge
Electrode Force
7.7
4.5
3.9
2.4
1.8
1.5
1.2
1.0
0.6
Forge
Delay
Time,
cyclesc
10
7
6
4
3
3
2
2
1
6
4
4
4
3
2
2
1
1
Weld Post-Heat
Time,
Time,
cyclesc cyclesc
48 000
41 300
38 750
35 750
29 300
28 500
26 000
24 000
21 000
Weld
33 400
28 800
27 100
25 000
20 500
20 000
18 000
16 900
14 700
Postheat
Approximate
Current, A
9.6
8.6
8.1
7.9
6.9
5.6
5.1
4.6
3.5
mm
1495
645
N
2490
5375
4380
0.14
0.38
0.34
0.32
0.31
0.27
0.22
0.20
0.18
5375
4380
3805
3290
2490
1935
1495
1090
645
N
1208
985
855
740
560
435
336
245
145
lb
Min. Average
Shear Strength
1208
985
560
435
336
145
lb
Min. Average
Shear Strength
1935
in.
Nugget
Diameter
0.38
0.34
0.27
0.23
0.20
0.14
in.
Spot Diameter
Table 2.28
Schedules for Spot Welding AZ31B Magnesium Alloy with DC Rectifier Machines
Source: The Dow Chemical Company.
a. Transformer turns ratio of 480:1.
b. Two equal thicknesses.
c. Spherical radius-faced electrodes on both sides.
in.
0.020
mm
Thicknessb
Electrodec
Table 2.27
Schedules for Spot Welding AZ31B Magnesium Alloy with Capacitor-Discharge Stored-Energy Machines a
AWS WELDING HANDBOOK
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
173
174
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
the columnar front, blocking off the growth of epitaxial
columnar grains and promoting CET.14 Typical solidification microstructures for two resistance-spot-welded
AZ31B alloys are shown in Figure 2.15. Detailed analysis facilitated by a transmission electron microscope
(TEM) has indicated that micro-scale Al8Mn5 particles
exist in the base metal in Figure 2.15(A), but not in that
of Figure 2.15(B). This refinement of the microstructure
14. Xiao, L., L. Liu, Y. Zhou, and S. Esmaeili, 2010, Resistance-SpotWelded AZ31 Magnesium Alloys, Part I: Dependence of Fusion Zone
Microstructures on Second-Phase Particles, Metallurgical and Materials Transactions, A, 41(6): 1511–1522.
AWS WELDING HANDBOOK
in the fusion zone in (A) has also improved joint fracture toughness.15
Preparation for Joint Sealing
Spot welded assemblies can be given either a chrome
pickle or a dichromate treatment, followed by painting
and finishing as needed. When sealed joints are required
or when the weldment is to be exposed to a corrosive
atmosphere, a suitable sealing compound should be
placed between the faying surfaces of the joint before
welding. Several proprietary compounds are available
for this purpose. Sealers should not be so viscous that
they will prevent metal-to-metal contact when the electrode force is applied. Welding should begin soon after
applying the compounds, and frequent tests should be
made to monitor weld quality.
Joint Strength
Typical shearing forces for spot welds for three magnesium alloys in several thicknesses are shown in Table
2.29. Although higher shearing forces are readily
obtainable, these represent average values for welds of
maximum soundness and consistency.
Resistance Seam Welding
(A)
Welding conditions for resistance seam welding
(RSEW) in magnesium alloys are similar to those
required for spot welding. Shear strength of seam welds
130 N/mm to 265 N/mm (750 lb/in. to 1500 lb/in.) can
be obtained in Alloy M1A in thicknesses of 1.0 mm to
3.3 mm (0.040 in. to 0.128 in.). The strength of seam
welds in Alloy AZ31B sheet is approximately 50%
higher.
FLASH WELDING
Source: Liu, L., L. Xiao, J. C. Feng, Y. H. Tian, S. Q. Zhou, and Y. Zhou, Resistance-SpotWelded AZ31 Magnesium Alloys: Part II: Effects of Welding Current on Microstructure
and Mechanical Properties, Metallurgical and Materials Transactions, A, 41(10), 2642–
2650.
Flash welding equipment and techniques similar to
those used for aluminum alloys can be used for magnesium alloys. High current densities and extremely rapid
flashing and upsetting rates are required. Upsetting current should continue for about 5 cycles to 10 cycles (60
Hz) after upset. Special shielding atmospheres are not
necessary.
Flash welds in magnesium Alloys AZ31B, AZ61A,
and HM31A have typical tensile strengths of 248 MPa,
290 MPa, and 262 MPa (36 ksi, 42 ksi, and 38 ksi),
Figure 2.15—Microstructure across the Weld
Nugget for Two Spot Welds in Alloy AZ31
with (A) Al8Mn5 Second-Phase Particles
and (B) Without Particles
15. Liu, L., L. Xiao, J. C. Feng, Y. H. Tian, S. Q. Zhou, and Y. Zhou,
2010, Resistance-Spot-Welded AZ31 Magnesium Alloys: Part II:
Effects of Welding Current on Microstructure and Mechanical Properties, Metallurgical and Materials Transactions, A, 41(10): 2642–
2650.
(B)
Note: The largest equiaxed dendritic zone (EDZ) is observed in (A)
and the largest columnar dendritic zone (CDZ) is observed in (B).
AWS WELDING HANDBOOK
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
175
Table 2.29
Typical Shear Strengths of Single Spot Welds in Wrought Magnesium Alloys
Spot Shear Strength
Thickness
Average Spot Diameter
AZ31B
HK31A
HM21A
mm
in.
mm
in.
N
lb
N
lb
N
lb
0.5
0.020
3.5
0.14
980
220
—
—
—
—
0.6
0.025
4.1
0.16
1200
270
—
—
—
—
0.8
0.032
4.6
0.18
1465
330
1335
300
—
—
1.0
0.040
5.1
0.20
1825
410
1670
375
1600
360
1.3
0.050
5.8
0.23
2355
530
2445
550
—
—
1.6
0.062
6.9
0.27
3335
750
3200
720
2935
660
2.0
0.080
7.9
0.31
3960
890
—
—
—
—
2.5
0.100
8.6
0.34
5250
1180
—
—
—
—
3.2
0.125
9.7
0.38
6805
1530
6625
1490
5425
1220
respectively, with elongations of about 4% to 8%. Typical microstructures for various zones in a flash welded
joint in an HM31A-T5 magnesium alloy extrusion are
shown in Figure 2.16.
HIGH-ENERGY BEAM
WELDING
Electron beam welding (EBW) and laser beam welding
(LBW) are used to join magnesium alloys. In both cases,
a high-energy-density beam is focused onto the weld
joint, resulting in fusion and vaporization of the base
metal. A concentrated energy source results in less heat
input, a smaller heat-affected zone, and less distortion.
ELECTRON BEAM WELDING
In general, magnesium alloys that can be welded by
means of the arc welding processes can also be joined
using electron beam welding (EBW). The same preweld
and postweld operations apply to all of these processes,
although electron beam welding requires much closer
tolerances on joint fit-up, with zero root opening. This
process is also less tolerant of minor contamination of
the joint. The fundamentals, procedures, and process
variations of electron beam welding are published in the
Welding Handbook, Volume 3.16
Close control of electron beam operating variables is
required to prevent overheating and porosity at the root
of the weld. The high vapor pressures in vacuum of
alloyed magnesium and zinc contribute to the porosity
problem. It is very difficult to produce sound electron
beam welds in magnesium alloys containing more than
1 wt % zinc. Beam manipulation (e.g., oscillation) can
be helpful in overcoming porosity. The micrograph in
Figure 2.17 shows a cross section of an electron beam
weld made in the keyhole mode (the typical nailhead
shape) in a magnesium extrusion of Alloy HM31A-T5
6.4 mm (0.25 in.) thick. There is also a nearly indistinguishable effect on the grain structure of the HAZ
(characteristic of a rapid thermal occurrence). This,
together with the ultra-fine grain size of the weld metal,
can produce very high joint efficiency and the absence
of porosity and undercutting.
16. Refer to Chapter 13, Electron Beam Welding, in American Welding
Society (AWS) Welding Handbook Committee, 2007, Welding Processes, Part 2, ed. A. O’Brien and C. Guzman, vol. 3, Welding Handbook, 9th ed., Miami: American Welding Society. See Appendix B of
this volume for detailed descriptions of chapter contents for the five
volumes of Welding Handbook, 9th ed.
176
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
AWS WELDING HANDBOOK
(A) Flash Weld [x5]
Figure 2.17—Electron Beam Weld in a
Magnesium Alloy HM31A-T5 Extrusion,
6.4 mm (0.25 in.) Thick (Magnified 10X)
(B) Weld Interface [x200]
LASER BEAM WELDING
(C) Upset Metal [x200]
Laser beam welding (LBW) can be carried out in
either the conduction mode or the keyhole mode.17 In
conduction welding, the surface of the material is
heated above the melting point, but below the vaporization temperature. Fusion occurs only by heat conduction through the weld pool. A weld bead with a
hemispherical cross section and an aspect ratio of 1:2 or
less is formed in a manner similar to the way a conventional fusion weld bead is formed. Conduction welds
are used to join thin materials.
Keyhole laser beam welding uses a high power density to cause local vaporization. Thus, a narrow and
deeply penetrated vapor cavity with an aspect ratio
higher than 1:2 is usually formed by multiple internal
reflections of the laser beam. Keyhole-mode welding
results in better energy coupling, deeper penetration,
and higher welding speed. Therefore, most applications
of laser beam welding are based on the keyhole tech-
(D) Unaffected Base Metal [x200]
Figure 2.16—Flash Weld and Microstructures
in HM31A-T5 Magnesium Alloy Rod
17. Refer to Chapter 14, Laser Beam Welding, Cutting and Associated Processes, in American Welding Society (AWS) Welding Handbook
Committee, 2007, Welding Processes, Part 2, ed. A. O’Brien and C.
Guzman, vol. 3, Welding Handbook, 9th ed., Miami: American Welding Society. See Appendix B of this volume for detailed descriptions of
chapter contents for the five volumes of Welding Handbook, 9th ed.
AWS WELDING HANDBOOK
(A)
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
177
(B)
Source: Cao, X., M. Xiao, M. Jahazi, and J. P. Immarigeon, 2005, Continuous Wave Nd:
YAG Laser Welding of Sand-Cast ZE41A-T5 Magnesium Alloys, Material Manufacturing
Processes, 20: 987–1004.
(A)
(B)
(C)
(D)
Figure 2.18—(A) Conduction Weld and
(B) Keyhole Weld in ZE41A-T5 Mg Alloy
nique.18 Figure 2.18 shows typical welds in the two
modes for the ZE41A-T5 magnesium alloy.
Various types of laser beam welding machines, such
as the Nd-YAG, CO2, diode, and fiber lasers, are used
to weld magnesium alloys. The Nd-YAG is believed to
work better than CO2 lasers because of better beam
coupling. The higher power densities of most laser
beam systems minimize the loss of mechanical properties of the weld compared to other heat sources (e.g.,
arc welding). Even when using laser systems, higher
power densities should generally be selected when possible. When welding AZ31B-H24, joint efficiencies of
90% can be achieved when using fiber lasers, and 60%
when using diode lasers. The loss of strength when
using the diode laser was attributed to the difference in
temper of the base metal and weld metal; the base metal
was received in a half-hard H24 temper and the assolidified weld metal was naturally in the softer, fully
annealed temper. Therefore, the higher power densities
of the fiber laser can reduce the softening effect caused
by welding. Typical fiber laser weld cross sections are
shown in Figure 2.19, which indicates that the laser
power is not sufficient in Figure 2.19(C) for complete
penetration, and laser power is too high in Figure
2.19(D), which caused too much vaporization and a
rough surface. Both (A) and (B) would be acceptable.
18. Cao, X., M. Xiao, M. Jahazi, and J. P. Immarigeon, 2005, Continuous Wave Nd: YAG Laser Welding of Sand-Cast ZE41A-T5 Magnesium Alloys, Material Manufacturing Processes, 20: 987–1004.
Source: E. Powidajko, 2009, Weldability of AZ31B Magnesium Sheet by Laser Welding
Processes, MASc Thesis, Waterloo, Ontario, Canada: University of Waterloo.
Figure 2.19—Transverse Cross Sections of
Fiber Laser Beam Welds in 2 mm Thick
AZ31B Sheet Made at 2 kW (A) 50 m/s;
(B) 150 m/s, (C) 250 m/s, and (D) 0.150 mm/s
Magnesium alloys possess certain inherent
characteristics, such as the following:
1. Low absorptivity of laser beams;
2. A strong tendency to oxidize;
3. High thermal conductivity;
178
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
4.
5.
6.
7.
High coefficient of thermal expansion;
Low melting and boiling temperatures;
A wide solidification temperature range;
High solidification shrinkage, a tendency to form
low melting constituents;
8. Low viscosity, low surface tensions;
9. High solubility for hydrogen in the liquid state;
and
10. Absence of color change at the melting-point
temperature.19
During laser beam welding of magnesium alloys,
therefore, welds can frequently exhibit unacceptable
conditions such as the following:
1. Unstable weld pool;
2. Substantial spatter;
3. Strong tendency to drop-through, sag,
underfill, and undercut;
4. Porosity;
5. Liquation cracking and solidification cracking;
AWS WELDING HANDBOOK
6. Oxide inclusions; and
7. Loss of alloying elements.20, 21
The typical porosity and underfill conditions that
can lead to weld defects can be observed in Figure 2.20.
Figure 2.20 shows liquation cracks in the HAZ and
solidification cracks in the fusion zone of the laser
welded ZE41A-T5 Mg alloy.22 When appropriate laser
processing parameters are used, however, crack-free
laser welded joints with low porosity can be achieved
for magnesium alloys.
Figure 2.21 shows the microstructures of laserwelded ZE41A-T5 Mg alloy.23 Fine equiaxed grains are
obtained in the fusion zone. The partially melted zone
of the HAZ is rather narrow, only a few grains wide.
No grain growth and coarsening are observed in the
19. Cao, X., and M. Jahazi, 2007, Use of Laser and Friction Stir
Welding for Aerospace Magnesium Alloys, Proceedings 3rd Int. Conference on Light Metals Technology, eds. K. Sadayappan and M.
Sahoo, Saint-Sauveur, Québec, Canada: 158–163.
20. Cao, X., and M. Jahazi, 2008, Overview of Friction Stir and
Laser Welding Techniques for Lightweight Alloys, Canadian Welding
Association, Journal of Materials Processing Technology, 19–30.
21. Cao, X., M. Jahazi, J. P. Immarigeon, and W. Wallace, 2006, A
Review of Laser Welding Techniques for Magnesium Alloys, Journal
of Materials Processing Technology, 171: 188–204.
22. Cao, X., M. Xiao, M. Jahazi, and J. P. Immarigeon, 2005, Continuous Wave Nd: YAG Laser Welding of Sand-Cast ZE41A-T5 Magnesium Alloys, Material Manufacturing Processes, 20: 987–1004.
23. Cao, X., M. Xiao, M. Jahazi, and J. P. Immarigeon, 2005, Continuous Wave Nd: YAG Laser Welding of Sand-Cast ZE41A-T5 Magnesium Alloys, Material Manufacturing Processes, 20: 987–1004.
(A)
(B)
Source: Cao, X., M. Xiao, M. Jahazi, and J. P. Immarigeon, 2005, Continuous Wave Nd:YAG Laser Welding of Sand-Cast ZE41A-T5 Magnesium Alloys, Material Manufacturing
Processes, 20: 987–1004.
Figure 2.20—(A) Heat-Affected Zone Liquation and (B) Fusion Zone
Solidification Cracks in 4 kW Nd:YAG Laser Beam-Welded ZE41A-T5
AWS WELDING HANDBOOK
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
(A)
(B)
179
(C)
Source: Cao, X., M. Xiao, M. Jahazi, and J. P. Immarigeon, 2005, Continuous Wave Nd:YAG Laser Welding of Sand-Cast ZE41A-T5 Magnesium Alloys, Material Manufacturing
Processes, 20: 987–1004.
Figure 2.21—Microstructure of 4 kW Nd:YAG Laser Welds in Alloy ZE41A-T5
in (A) the Fusion Zone, (B) Heat-Affected Zone, and (C) Base Metal
JOINT EFFICIENCIES (%)
100
80
60
40
20
0
AGED
AS-WELDED
= YIELD STRENGTH
= ULTIMATE TENSILE STRENGTH
= ELONGATION
Source: Cao, X., and M. Jahazi, 2008, Overview of Friction Stir and Laser Welding Techniques for
Lightweight Alloys, Canadian Welding Association, Invited paper, 19–30.
Figure 2.22—Joint Efficiencies Relative to Yield Strength, Ultimate Tensile Strength, and
Elongation of 4 kW Nd:YAG Laser Beam Welds in 2 mm (0.078 in.) Thick ZE41A-T5 Mg Alloy
HAZ. The welded joints can nearly reach yield and tensile strengths similar to those of the base metal ZE41AT5 Mg alloy, as shown in Figure 2.22, but there is some
loss in ductility after laser beam welding.24
24. Cao, X., and M. Jahazi, 2008, Overview of Friction Stir and
Laser Welding Techniques for Lightweight alloys, Canadian Welding
Association, Invited paper, 19–30.
SOLID-STATE WELDING
The solid-state welding process used in the welding
of magnesium alloys and discussed in this section is friction stir welding (FSW), a variation of friction welding
(FW). The weld is produced by the friction heating and
180
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
AWS WELDING HANDBOOK
plastic material displacement caused by a rapidly rotating tool traversing the weld joint.25
FRICTION STIR WELDING
Friction stir welding is a variation of friction welding
that produces a weld by the friction heating and plastic
material displacement caused by a rapidly rotating tool
traversing the weld joint.
Compared to traditional fusion welding processes,
FSW is a relatively new joining technique that has the
capability of joining various metals at temperatures
below the melting temperature of the metals. It is highly
versatile and safe to operate, and in addition, requires
less energy than fusion welding processes.26 Because
it does not require filler metals and shielding gases, and
does not generate fumes during welding, FSW is considered to be an efficient, economical, and environmentally favorable welding process. For basic information,
refer to the chapter on friction stir welding in Volume 3
of the Welding Handbook.27
Friction stir welding was invented and developed to
address a problem at hand: the difficulty of creating
high-strength and fatigue-resistant welds in advanced
aluminum alloys, such as those used in aerospace applications. Aluminum alloys of the 2XXX (Al-Cu-Mg)
and 7XXX (Al-Zn-Mg) series were considered to be virtually unweldable using fusion welding processes,
because porosity, solidification cracking, and microstructural degradation in the HAZ were inherent problems. Because it is a solid-state welding process, FSW
avoids altogether the first two of these problems.
A further development of friction stir welding is friction stir processing, a recent adaptation that is not used
for welding, but is used to locally modify the microstructure of a workpiece. Because of the broad spectrum of possible process parameters, a large variety of
modifications, such as ultrafine grains in an otherwise
coarse microstructure, can be achieved.
Friction stir welding is relatively simple; it is accomplished with the use of a nonconsumable tool and a
backing bar to accommodate the applied loads. The
tool, which has a specially designed pin and shoulder, as
shown in Figure 2.23, is set under rotation and is
inserted into the weld joint under axial force.
25. The titles, authors, and facts of publication of technical papers
and other resources represented in this section are listed in the Bibliography in the Friction Stir Welding section.
26. Friction stir welding was invented in 1991 by Wayne Thomas at
TWI, Ltd., Cambridge, United Kingdom, with TWI holding worldwide patents. Patent EP0615480 (expired) was renewed with innovations in 1995; also patents EP0752926, US5813592, and others.
27. American Welding Society (AWS) Welding Handbook Committee,
2004, Welding Handbook, Volume 3, Welding Processes, Part 2,
Miami, Florida: American Welding Society, Chapter 7.
Figure 2.23—Tool Assembly
(Side View and End View)
Figure 2.24 shows the sequence of friction stir welding. While the tool is moved into the joint, as shown in
Figure 2.24(A), the workpieces are heated by friction,
which results in plasticization of the metal under the tool.
In (B), the stirring motion of the tool moves the plasticized material around the tool, resulting in the local
mixing of the materials of the two workpieces. With the
onset of translation movement (C), material from the
front of the tool is transported to the back, creating a
weld. Then the tool is lifted from the workpiece (D),
leaving a characteristic end hole.
Due to the inherent asymmetry of the process, the two
sides of the weld are specifically designated: the advancing side (AS) is the side where the vector representing the
rotational and the translational movement of the tool
are the same; the opposite side is the retreating side (RS).
During friction stir welding, the workpiece material
undergoes intense plastic deformation at elevated temperatures, which results in a stir zone with a microstructure and texture that often varies greatly from the
base material.
Friction stir welding can be used to join a large variety of wrought and cast magnesium alloys, including
AZ (AZ31, AZ61, AZ91), ZK (ZK60), and the AM
(AM50, AM60) series. Even though the processing
route of the base material during manufacture has a
substantial influence on the resulting mechanical properties, the effect on weldability is negligible.
Preweld Cleaning
Preweld cleaning of the joint and the vicinity of the
joint is essential to avoiding oxide entrapment within
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CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
(A)
(B)
(C)
(D)
181
Source: Helmholtz-Zentrum Geesthacht.
Figure 2.24—Sequence of Friction Stir Welding: (A) Tool Plunge, (B) Beginning of
Rotational Movement, (C) Travel Along the Weld Joint, and (D) the Finished Weld
the weld. To remove the oxide layer that is inherent to
magnesium surfaces, it is recommended that the areas
that will be in contact with the tool shoulder be lightly
ground, using an abrasive paper. A subsequent cleaning
with ethanol is advised to remove any Mg dust residues
and greases remaining from handling. The latter is particularly important, because any grease would result in
a reduction in friction that would influence the process
repeatability and might even lead to flawed process zones.
Equipment
The handling systems for FSW can be adapted to a
variety of machines: the tool can be fixed and the workpieces moved (e.g., on a table) or the workpieces can be
fixed. Friction stir welding machines typically incorporate the ability to tilt the tool in one or more directions
to accommodate the direction of welding and to compensate for low rigidity of the machine. Linear FSW has
been conducted on reconstructed milling machines and
also on designated welding machines, such as gantrymounted machines. Three-dimensional welds have been
conducted on articulated and parallel kinematic robotic
systems. When large forces are applied during welding,
repeatability of the weld often depends on the ability of
the machine to accommodate these high loads.
Tool Construction
A tool made of high-speed steel is typically used for
friction stir welding of magnesium alloys. Specialty tool
material is not needed for friction stir welding of magnesium, in contrast to the tool construction required for
welding high-strength materials with high melting
points, such as steel or titanium. Different tool geometries with a variety of features have been widely used.
The geometries of tool shoulders range from concave,
flat, or convex shapes with features such as flutes or
other indentations. Pins also are made in different
shapes, some with features such as threads and flutes.
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In addition to conventional tools, bobbin tools have
been successfully used to join Mg alloys. Bobbin tools
are self-reacting tools having an additional lower shoulder that is used to confine the occurring loads under the
tool, rendering a backing bar unnecessary. Hollow profiles can easily be welded using a bobbin tool.
the tool and plate is often done when using friction stir
welding for high-melting-temperature materials, like
steel and titanium alloys, but is not necessary when
welding Mg alloys. It should be noted that controlled
cooling can be used to reduce extensive grain growth in
Mg alloys and also to limit the dissolution of strengthening precipitates within the weld.
PROCESS PARAMETERS
Process parameters for friction stir welding of magnesium are similar to those used for aluminum alloys.
Typical revolutions per minute (RPM) of the tool are
between 500 rpm and 5000 rpm. (Sticking of material
to the tool has been reported as the result of low rpm.)
Welding speed ranges from a few millimeters per
minute (mm/min) to approximately 20 meters per
minute (m/min [65.6 feet/min]) and has been carried
out in position and in force-control mode.
Filler metals and shielding gases are not needed
because the magnesium at the weld interface is not
melted, but merely plasticized.
Preheating and Cooling
Depending on the magnesium alloy to be welded,
preheating or cooling might be necessary. Preheating of
(A) Butt Joint
(D) T-Joint
Joint Design
The most commonly used joint designs for the friction stir welding of magnesium are butt joints and lap
joints, used in various configurations. Typical designs
are shown in Figure 2.25.
Depending on the chosen joint configuration, more
or less sophisticated clamping devices are needed to prevent the workpieces from separating during welding.
Clamping can be accomplished mechanically with
screw-down claws, hydraulically by creating a vacuum,
or with any other suitable means, as long as the clamping does not interfere with the weld path.
Special joint designs are not required when using
friction stir welding to produce leak-tight joints. The
process is often used as a sealing technique.
(B) Lap Joint
(E) Corner Joint
(C) Tube-to-Sheet Joint
(F) Double Corner Joint
Source: © EWI. Used with permission.
Figure 2.25—Basic Joint Designs for Friction Stir Welding
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CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
183
Postweld Heat Treatment
During manufacture, industrially used AZ31, AZ61
and AZ91 plates or sheets are usually exposed to a
stress-relieving heat treatment after rolling. For AZ31BO, stress relieving is performed at 345°C (653°F) for
120 min; AZ31B-H24 is exposed for stress relieving at
150°C (302°F) for 60 min. Extruded material, for
example, AZ31B-F, undergoes stress relieving at 260°C
(500°F) for 15 minutes. Postweld heat treatment is usually not required because residual stresses are low in
friction-stir-welded workpieces, in contrast to fusion
welded workpieces.
Postweld heat treatment can be used to impose controlled microstructural changes in the magnesium weldment; however, the parameters for such heat treatments
are beyond the scope of this general discussion.
(A)
(B)
(C)
(D)
WELD MICROSTRUCTURE
A weld created by FSW is typically divided into three
microstructural zones, as shown in Figure 2.26. In the
center of the weld is the stir zone (SZ), which mainly
consists of recrystallized grains. This zone undergoes
most of the thermal and mechanical load imposed during welding. The thermomechanically affected zone
(TMAZ) is adjacent to the stir zone. The TMAZ exhibits some thermal and mechanical loads that are not as
severe as those in the SZ. Bordering the TMAZ is the
heat-affected zone (HAZ), which undergoes only thermal loads.
Grain size depends greatly on welding parameters,
and can vary among the different microstructural weld
zones. The magnitude of the metallurgical changes is
dependent on welding parameters and also the manufacturing process route of the base material. This is particularly evident in the stir zone, where grain growth
and grain refinement that can be achieved is dependent
on thermal energy. The microstructure of these zones in
a friction stir weld, shown in Figure 2.27, varies greatly
compared to the microstructure of the base material. In
general, the grain shape is described as recrystallized.
The magnitude of grain size reduction is more pronounced in cast alloys, usually having larger initial grain
Figure 2.26—Typical Microstructural Zones
of a Friction Stir Weld in AZ31
Source: Afrin, N., D. Chen, X. Cao, and M. Jahazi, 2008, Microstructure and Tensile
Properties of Friction Stir Welded AZ31B Magnesium Alloy. Materials Science and
Engineering, A, 472(1-2), 179–186.
Figure 2.27—Optical Microscope Images of the
(A) Stir Zone, (B) Thermomechanically Affected
Zone, (C) Heat-Affected Zone, and (D) Base Metal
sizes. Various microstructural features also occur within
the different zones: the TMAZ can exhibit an even
greater reduction in grain size than that of the SZ, and the
HAZ can undergo grain growth due to the imposed thermal cycle, although the HAZ lacks the mechanical contribution that would give it a local annealing treatment.
Weld Texture. Most of the low-temperature form-
ability of magnesium is derived from basal slip; therefore, texture development during welding is of special
interest. The largest portion of deformation during
FSW happens within the surface layer under the shoulder. As material is picked up at the advancing side, it is
transported around the tool and deposited at the
retreating side. The material undergoes high amounts of
strain in these regions, which mainly arise from basal
slip, with contributions from twinning, and eventually
prismatic slip at elevated temperatures.
The texture changes in the process zone depend on
the base material, process parameters, and the tool
geometry. Although tools with large shoulder diameters
may create a more random texture, tools with smaller
shoulder diameters produce a pronounced basal texture.
Compared to the basal texture usually introduced during rolling, the texture in the stir zone exhibits a shift
184
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
AWS WELDING HANDBOOK
Source: Adapted from Park, S. H. C., Y. S. Sato, and H. Kokawa, 2003, Basal Plane Texture and Flow Pattern in Friction Stir Weld of a Magnesium Alloy.
Metallurgical and Materials Transactions, A, 34(4): 987–994.
Figure 2.28—Pole Figures Showing a Change in Preferred Crystal Orientation
within the Magnesium Stir Zone for Two Pole Directions: 0002 and 10TD
toward the direction of processing, as shown in Figure
2.28. The temperature during this shift can range from
30°C to 80°C (86°F to 176°F).
The degree of temperature at which the shift happens
and the resulting intensity strongly depend on processing parameters. The reorientation of the basal planes
combined with a decrease in grain size results in great
improvements in tensile strength and ductility that can
significantly surpass these values in the base metal.
Weld Corrosion
In general, corrosion in welded structures is an
important consideration, as it may define the applicability of processes and materials in certain environments. In an uncoated form, magnesium is generally
susceptible to contact corrosion; thus, preventive mea-
sures must be taken to avoid material degradation. During FSW, the material is not melted and no additional
filler material is introduced into the weld; this results in
a chemical equity between the weld zones and base
material. Differences in corrosion reactions can thus be
ascribed only to microstructural changes.
Corrosion tests conducted on AZ31 without external
mechanical loading revealed not only similar corrosion
morphologies between the weld zones and base metal,
but also showed an increase in corrosion resistance.
Tensile testing of weld zones in samples exposed to corrosive environments showed less resistance to stress
corrosion cracking than the base material.
Corrosion in friction stir welds in AM50 is strongly
dependent on β-Phase distribution. Intergranular corrosion is predominantly found in the base material,
whereas pitting and filiform corrosion occurs in the
AWS WELDING HANDBOOK
process zones. Corrosion resistance increases throughout the different metallurgical zones, with least corrosion resistance in the base metal.
Mechanical Properties
Mechanical properties discussed in this section
include hardness, tensile strength, compressive strength,
formability, and fatigue.
Hardness. Based on the results of research conducted
on the effect of FSW on microhardness, no explicit
conclusions could be drawn. Some investigations
showed an increase in hardness in the weld zones,
while others showed no difference, or even a decrease,
compared to the base material. The differences reported
were notable between the weld and the base metal,
and also within the various zones of the weld.
The observed differences in hardness are mainly
attributed to two factors. The first is the thermomechanical processing route of the base material during
manufacture, which defines grain size and shape,
texture, residual stresses and also stored plastic energy
introduced during rolling. The second factor is the
welding process, in which the plastic deformation and
the thermal input during welding are defined by the
process parameters. This ambiguity must be taken into
account relative to the base material, and process
parameters should be adjusted accordingly.
Tensile Strength. The applicability of welded
structures often depends on the joint strength. Because
joint formation occurs below the liquidus temperature,
friction stir welding has shown particularly good
results over conventional fusion welding.
In Mg alloys, tensile strength such as yield strength
(YS) and ultimate tensile strength (UTS) show only
minute decreases with joint strengths of ~95% of the
base metal, accompanied by a strain-hardening capability
of about twice that of the base material.
In wrought alloys, such as AZ31 and AZ61, the
cause of this decrease in strength is either due to the
buildup of oxides between the TMAZ and SZ originating
from the surface or due to alteration of the workhardened structure. Postweld loading steps such as
subsequent compression along the normal direction
show increased yield strength due to basal plane
reorientation. Cast alloys, such as AM50 and AM60,
show similar results, exhibiting a slightly greater
strength with increasing α-Mg content.
With extruded ZK60, friction stir processing combined with precipitate hardening (aging) steps can lead
to a significant increase in tensile strength, surpassing
the base material values while keeping elongation-tofracture at comparable levels.
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
185
FRICTION STIR PROCESSING
Friction stir processing uses the same tools and
handling systems as friction stir welding. Because of
the broad spectrum of possible process parameters, a
large variety of microstructural modifications can be
made. Results of the friction stir processing of extruded
ZK60 are shown in Figure 2.29.
In wrought alloys, weld ductility properties of
the weld, such as tensile elongation, often exhibit a
significant reduction. This reduction is correlated
to high strain rates that occur during FSW and the
resulting grain refinement. Postweld aging can be
used to improve tensile elongation, but often
comes at the expense of reduced tensile strength.
Compressive Strength. In addition to basal slip, the
main deformation mechanism under compressive loading
is compressive twinning. Because twinning is more
likely to occur in large grains, friction stir welding can
improve compressive strength by means of the grainrefinement capabilities of the process.
Formability. The formability of Mg alloys at room
temperature is inherently limited, due to the lack of
sufficient and available slip systems. The effect of friction
stir welding on formability has been investigated for
both wrought and cast magnesium.
Similar to the effect of FSW on hardness, no distinct
results can be drawn from the literature. Limited dome
height experiments conducted on wrought AZ31
revealed diverse results, where both an increase and
decrease in dome height was found when compared to
the base material. This is illustrated in Figure 2.30.
While the decrease has been attributed to grain
refinement in the weld zones, microstructural
homogenization was also deemed responsible for the
observed increase, stressing the fact that formability is
strongly dependent on the base material characteristics
in addition to the welding parameters. Conversely, cast
alloys, such as AZ91, undergo vast increases in
formability compared to the base material. This
increase is attributed mainly to the homogenization of
the coarse grain of the cast microstructure.
Fatigue. Fatigue is one of the main concerns relative
to welded structures; thus, the FSW process is often
selected because welds can be made at sub-melting temperatures, which reduces the risk of weld embrittlement.
While comprehensive studies have been conducted
on the fatigue behavior of friction-stir-welded aluminum structures that show better performance compared
to those welded with conventional techniques, similar
information on magnesium structures is limited. Fatigue
performance of friction-stir-welded AZ31 reached values
close to those of the base metal, as shown in Figure 2.31.
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CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
AWS WELDING HANDBOOK
Source: Adapted from Mansoor, B., and A. Ghosh, 2012, Microstructure and Tensile Behavior of a Friction Stir Processed Magnesium
Alloy. Acta Materialia, 60 (13-14): 5079–5088.
Figure 2.29—Tensile Stress-Strain Curves for Extruded ZK60 at Room Temperature
This is true for both notched and smooth specimens.
The increase in fatigue life over the base material values
in cast AZ91 has been attributed to the microstructural
refinement of the otherwise defect-prone cast microstructure and also the dissolution of the β phase.
This is true for both notched and smooth specimens.
The increase in fatigue life over the base material values
in cast AZ91 has been attributed to the microstructural
refinement of the otherwise defect-prone cast microstructure and also the dissolution of the β phase.
FRICTION STIR SPOT WELDING
In general, friction stir spot welding (FSSW) can be
applied to any of the magnesium alloys that have been successfully welded using the FSW process, including AZ31,
AZ61, AZ91 (as-cast and thixomolded), and AM60.
Tool Design
The tool, consisting of a pin and a shoulder, used in
friction stir spot welding of magnesium alloys is similar
to that used in FSW and FSSW of aluminum. Tools with
a concave or flat shoulder and pins with step, spiral
thread or three-flat, designs have been used for the friction stir spot welding of magnesium alloys.
Procedure
The sequence of friction stir spot welding is shown in
Figure 2.32. In 2.32(A), the rotating tool is plunged
into the workpieces to a predetermined depth, (B) rotation continues as the tool penetrates the base metal,
then (C) the tool is retracted from the weld metal, without translation movement on the surface.
AWS WELDING HANDBOOK
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
187
Source: Adapted from Venkateswarlu, G., D. Devaraju, M. J. Davidson, B. Kotiveerachari, and G. R. N. Tagore, 2013, Effect of Overlapping
Ratio on Mechanical Properties and Formability of Friction Stir Processed Mg AZ31B Alloy, Materials and Design, 45: 480–486.
Figure 2.30—Results of Limited Dome Height on Friction Stir
Processing of AZ31 with Varied Tool Shoulder Diameters
Refill Friction Spot Welding
Refill friction spot welding is a technique in which
the spot weld is made without leaving an indentation or
mark on the surface of the workpiece after the weld is
completed. In general, refill friction stir spot welding
can be used to join all magnesium alloys that can be
joined by friction stir welding.
Tool Design
The tool used for refill friction stir welding consists of
two rotating parts (a pin and sleeve) and a stationary
clamping ring. The tool parts move independently of
one another. Figure 2.33 shows the pin, sleeve, and
assembled tool.
Procedure
The refill procedure for joining sheet magnesium
using friction stir spot welding is shown in Figure 2.34.
The clamping ring holds workpieces against a backing
bar. One part of the rotating sleeve penetrates into the
workpieces to heat the weld interface, and the inner pin
is retracted to accommodate the plasticized material;
then both the rotating pin and shoulder move back to
the original position on the weld metal surface.
Weld Microstructure
Typical cross-section views of the weld joined by
FSSW with the refill technique are shown in Figure
2.35. Due to the nature of the process, an exit hole
(keyhole) can be observed on the weld surface produced
by FSSW in Figure 2.35(A), whereas a keyhole cannot
be observed on the weld surface produced by refill
FSSW in (B).
Common to samples produced by FSW, the weld can
be characterized into 3 regions: the stir zone (SZ), thermomechanically affected zone (TMAZ) and un-affected
base metal (BM). Microstructures obtained from the
SZ, TMAZ and unaffected base metal produced by
refill FSSW are shown in Figure 2.36. The SZ consists
of fine grains formed due to recrystallization, induced
by intense plastic deformation and high temperature
exposure. The TMAZ consists of elongated grains and
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CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
AWS WELDING HANDBOOK
Source: Adapted from Chowdhury, S., D. Chen, S. Bhole, and X. Cao. 2010, Effect of Pin Tool Thread Orientation on Fatigue Strength of
Friction Stir Welded AZ31B-H24 Mg Butt Joints, Procedia Engineering, 2(1), 825–833.
Figure 2.31—S-N Curves for a Friction Stir Weldment of AZ31-HZ4
Source: Adapted from Yuan, W., R. S. Mishra, B. Carlson, R. Verma, and R. K. Mishra, 2012. Materials Flow and Microstructural Evolution during
Friction Stir Spot Welding of AZ31 Magnesium Alloy, Materials Science and Engineering, A, 543: 200–209.
Figure 2.32—Sequence of Friction Stir Spot Welding (A) Plunge of Rotating Tool,
(B) Continuing Rotation during Welding, and (C) Retraction of the Tool
AWS WELDING HANDBOOK
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
189
Source: Helmholtz-Zentrum Geesthacht.
Figure 2.33—(A) Tool Components and (B) Complete Assembly for Refill Friction Stir Spot Welding
Source: Tier, M. D., T.S. Rosendo, J. F. dos Santos, N. Huber, J. A. Mazzaferro, C. P. Mazzaferro, T. R. Strohaecker, 2013, The Influence of Refill FSSW Parameters on the
Microstructure and Shear Strength of 5042 Aluminium Welds, Journal of Materials Processing Technology, Elsevier: 213: 917–1005.
Figure 2.34—Sequence of Refill Friction Stir Spot Welding: (A) Tool is Positioned,
(B) Sleeve Inserted, (C) Pin Inserted as Sleeve is Retracted, and (D) Weld is Complete
is characterized as a region that has undergone plastic
deformation while exposed to high temperature, but
has no recrystallization.
Friction stir spot welding (FSSW) is classified as
solid-state joining process, however, the formation of
αMg + Al17Mg12 eutectic phase has been reported during FSSW of Mg alloys having a high content of Al.
When the peak temperature reaches 437°C (819°F) or
higher during welding, some areas that have a eutectic
composition transform to a liquid phase starting at the
grain boundaries. During the cooling cycle, this liquid
phase at the grain boundary transforms to the eutectic,
as shown in Figure 2.37(A). Formation of this eutectic
might also lead to cracking, as shown in Figure 2.37(B).
Magnesium alloys that contain high amounts of aluminum are more susceptible to cracking induced by liquation; however, optimization of welding parameters can
eliminate the formation of eutectic and avoid cracking.
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CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
AWS WELDING HANDBOOK
(A)
Key:
SZ
=
TMAZ =
BM
=
Hook =
(B)
Stir Zone
Thermomechanical Zone
Base Metal
Discontinuity between the thermomechanically affected zone and the base metal.
Figure 2.35—Cross Section of Spot Weld Produced by Friction Stir Spot Welding with
(A) Keyhole and (B) Regions of the Weld (Note “Hook” Discontinuity)
(A)
(B)
(C)
Source: Campanelli L. C., U. F. H. Suhuddin, J. F. dos Santos, and N. G. Alcântara, 2012, Preliminary Investigation on Friction Spot Welding of AZ31 Magnesium Alloy, Materials
Science Forum, Trans Tech Publications, Switzerland: 706-709: 3016–3021.
Figure 2.36—Microstructure of Refill Friction Stir Spot Weld Metal:
(A) Base Metal, (B) Thermomechanically Affected Zone and (C) Stir Zone
Even though the measured peak temperature during
friction stir spot welding of AZ31 reached 514°C
(957°F), no eutectic phase could be observed in the
weld metal.
A common discontinuity found in the weld produced
by FSSW and refill FSSW is a hook, as shown in Figure
2.38. A hook in a lap weld in magnesium consists of a
partially welded region that forms when the interface of
contacting sheets is broken into intermittent oxide particles after penetration of the tool. The hook dimension
and curvature are important to weld metal strength,
where crack initiation can occur at the tip of the hook
during mechanical loading, such as during lap-shear
testing. (Refer to Figure 2.35.)
OXYFUEL GAS WELDING
Oxyfuel gas welding (OFW) is not recommended for
welding magnesium alloys; this process should be used
only for emergency welds, i.e., field repair work, when
suitable arc welding equipment is not available.28 The
use of OFW is restricted almost exclusively to simple
28. Refer to Chapter 11, Oxyfuel Gas Welding, in American Welding
Society (AWS) Welding Handbook Committee, 2004, Welding Processes, Part 1, ed. A. O’Brien, vol. 2, Welding Handbook, 9th ed.,
Miami: American Welding Society. See Appendix B of this volume for
a detailed description of chapter contents for the five volumes of
Welding Handbook, 9th ed.
AWS WELDING HANDBOOK
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
(A)
191
(B)
Source: Yamamoto, M., A. Gerlich, T. H. North, and K. Shinozaki, 2007, Cracking in the Stir Zones of Mg-Alloy Friction Stir Spot Welds, Journal of Materials Science, 42: 7657–7666.
Figure 2.37—(A) Microstructure of the Eutectic Phase in
the Weld and (B) Liquid-Penetration-Induced Cracking
(A)
(B)
Source: Wang. D., J. Shen, and L. Wang, 2012, Effects of the Types of Overlap on the Mechanical Properties of FSSW-Welded AZ series, International Journal of Minerals, Metallurgy, and Materials, 19(3): 231–235.
Figure 2.38—Patterns of Hooking Discontinuity (A) Friction Stir
Spot Weld and (B) Refill Friction Stir Spot Weld in AZ Series
192
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
groove welds from which residual flux can be effectively removed. Repair welds should be considered to
be temporary and should remain in service only until
they can be replaced with arc welds or a new component can be put in service.
FUEL GASES
The fuel gases most commonly used in oxyfuel gas
welding are acetylene or a mixture of approximately
80% hydrogen and 20% methane. The latter gas mixture is well suited for welding sheets up to 1.6 mm
(0.064 in.) thick because of the characteristic soft flame
it produces. For welding thicker gauges, acetylene is
preferable because it provides the properties of higher
heat of combustion. The oxyacetylene flame can cause
slight pitting of the weld surface, but this type of pitting
is rarely serious enough to impair the strength of the weld.
FLUXES
--``,,,,`,,,,`,,,,`,,,,,,,,,````-`-`,,`,,`,`,,`---
Fluxes specifically recommended for oxyfuel gas
welding of magnesium should be used. These fluxes
typically contain a mixture of chloride and fluoride
salts that serve to break down magnesium oxide. The
flux is prepared by dissolving the salt mixture in water
or alcohol and forming a slurry or paste, which should
be used soon after mixing. Prior to fluxing, the area to
be welded should be cleaned to remove any dirt, oil,
grease, oxide, or conversion coating.
A flux composition suitable for welding with various
fuel gases is a mixture of 53 wt % KCl, 29 wt % CaCl2,
12 wt % NaCl, and 6 wt % NaF. A flux mixture suitable only for oxyacetylene welding consists of 45 wt %
KCl, 26 wt % NaCl, 23 wt % LiCl, and 6 wt % NaF.
The sodium compounds in these welding fluxes will
give an intense yellow color to the flame. Suitable ventilation and eye protection are necessary when using
these fluxes.
WELDING TECHNIQUE
A coating of flux should be applied liberally to both
sides of the joint and to the welding rod. If needed, the
joint should be tack welded at 25 mm to 76 mm (1 in.
to 3 in.) intervals, depending on the metal thickness. All
tack welds and overlapping weld beads should be
remelted to float out any flux inclusions. All traces of
flux should be removed from the weldment using a hotwater rinse, followed by a chrome pickle and immersion in a boiling solution of flux remover.
AWS WELDING HANDBOOK
BRAZING
The brazing of magnesium is not widely practiced
because of the high oxidation tendency of magnesium,
the more tenacious structure of the magnesium oxide
film, and the limited availability of industrial brazing
filler metals and fluxes.
Furnace brazing, torch brazing, and dip brazing can
be employed, but experience is limited to furnace and
torch brazing of AZ10A, AZ31B, M1A, K1A, ZE10A,
and ZK12A, which are magnesium alloys that have a
solidus temperature around 600°C (1112°F) or above.
A complex oxide film consisting of magnesium oxide
and magnesium hydroxide is formed on the surface of
the base metal when heated in air. This chemically stable film is not reduced in conventional active gaseous
atmospheres or in a vacuum down to 10–3 Pa (10–5
torr). In addition, magnesium hydroxide is decomposed
to hydrogen and water during heating between 300°C
and 400°C (570°F to 760°F), which further hinders the
brazing process.
The density of magnesium brazing filler metals is
lower than that of brazing fluxes, which often results in
slag inclusions in the brazed joints. Also, magnesium has
a high negative value of electrode potential (–2.38 V),
which hinders the deposition of protective electrolytic
or chemical coatings that can improve wetting by
molten brazing filler metals or protect against flux
corrosion.29, 30
JOINT TYPES
Braze joints should be designed to take advantage of
capillary action, which allows the flux to be displaced
by the brazing filler metal that flows into the joint.
Because of the corrosive nature of the flux used during
the brazing process, the joints should be carefully
designed to minimize flux entrapment. Lap joints and
butt joints can be used for magnesium assemblies. Joint
clearances of 0.10 mm to 0.25 mm (0.004 in. to 0.010
in.) at the brazing temperature are satisfactory; however, joint designs with the smallest clearance that permits good capillary action of the brazing filler metal are
recommended. For dip brazing, the joint should be
designed with slots or recessed grooves to accommo29. Refer to Chapter 12, Brazing, in American Welding Society
(AWS) Welding Handbook Committee, 2004, Welding Processes, Part
1, ed. A. O’Brien, vol. 2, Welding Handbook, 9th ed., Miami: American Welding Society. See also Appendix B of this volume for detailed
description of chapter contents for the five volumes of Welding Handbook, 9th ed.
30. American Welding Society (AWS) Committee on Brazing and Soldering, 2007, Brazing Handbook, 5th ed., Miami: American Welding
Society.
AWS WELDING HANDBOOK
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
date the brazing filler metal and prevent it from being
washed into the flux bath.31
193
long and 3.2 mm (0.125 in.) in diameter; the brazing
temperature range is 604°C to 626°C (1120°F to
1160°F). Users must note that the brazing temperature
for this filler metal is above the heat-treatment temperature of most wrought magnesium alloys, which
means that some base metals can lose mechanical
strength, at least partially, when exposed to the brazing
temperature.33
Low-temperature, non-commercial brazing filler
metals based on the magnesium-zinc alloy system are
shown in Table 2.31. The lower melting range and
brazing temperatures for these alloys will not result in
reduced mechanical properties of base materials, but
can require the application of special fluxes or the assistance of ultrasound vibration to destroy the magnesium
oxide film. The brazing filler metals are alloyed with
0.1 wt % to 0.5 wt % manganese to improve corrosion
FILLER METALS
The only brazing filler metal specified for magnesium
in Specification for Filler Metals for Brazing and Braze
Welding (AWS A5.8) is BMg-1.32 This filler metal contains 9 wt % aluminum, and 2 wt % zinc, as described
in Table 2.30. Although similar to the casting Alloy
AZ92A, filler metal BMg-1 contains a small amount of
beryllium to prevent excessive oxidation and reduce the
risk of ignition while molten in air. Alloy BMg-1 filler
metal is supplied in the form of rods 455 mm (36 in.)
31. Peaslee, R. L., and R. L. Holdren, 2007, Brazement Design, in
American Welding Society (AWS) Committee on Brazing and Soldering,
Brazing Handbook, 21–66, 5th ed. Miami: American Welding Society.
32. American Welding Society (AWS) Committee on Filler Metals
and Allied Materials, 2011, Specification for Filler Metals for Brazing
and Braze Welding, AWS A5.8M/A5.8:2011, Miami: American Welding Society.
33. Shapiro, A. E., 2007, Brazing of Magnesium and Magnesium
Alloys, in American Welding Society (AWS) Committee on Brazing
and Soldering, Brazing Handbook, 5th ed. Miami: American Welding
Society, 497–510.
Table 2.30
Composition and Physical Properties of Commercial Magnesium Brazing Filler Metal
Designation
Nominal Composition, wt % (Balance Mg)
Temperatures
AWS
ASTM
Al
Zn
Mn
Cu
Be
Si
Others
Density,
g/cm3
(lbs/in.3)
BMg-1
AZ92A
8.3–9.7
1.7–2.3
0.15–1.5
0.05
0.0002–0.0008
0.05
Fe 0.005
Ni 0.005
1.83
(0.066)
Solidus, Liquidus,
°C (°F)
°C (°F)
443
(830)
599
(1110)
Brazing
Range,
°C (°F)
604–627
(1120–1160)
Source: Adapted from American Welding Society A5 Committee on Filler Metals and Allied Materials, 2011, Specification for Filler Metals for Brazing and
Braze Welding, AWS A5.8M/A5.8:2011 Miami: American Welding Society; Table 3.
Table 2.31
Composition and Physical Properties of Low-Temperature Brazing Filler Metals*
Temperatures
Nominal Composition, wt % (Balance Mg)
Al
Zn
Mn
Be
Others
Density,
g/cm3
(lbs/in.3)
11–13
4.5–5.5
—
0.3
2.1 (0.076)
770 (410)
565 (1049)
2
55
—
0.0002–
0.0008
—
—
4.7 (0.169)
330 (626)
360 (680)
P430Mg
0.7–1.0
13–15
0.1–0.5
—
0.3
2.7 (0.097)
380 (716)
430 (806)
P380Mg
2.0–2.5
23–25
0.1–0.5
—
0.3
3.0 (0.107)
340 (644)
380 (716)
Brazing
Filler Metal
BMg-2a (AZ125A)
GA432
Solidus,
°C (°F)
Liquidus,
°C (°F)
Brazing
Range,
°C (°F)
570–595
(1058–1103)
495–505
(925–940)
550–560
(1020–1040)
480–500
(896–932)
*The brazing filler metals listed in this table are not in commercial use in the United States. They have been used in the United States and Europe, and would
work well for future applications for the brazing of new magnesium alloys and magnesium matrix composites that have low solidus temperatures.
194
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
resistance, and with less than 0.02 wt % beryllium to
suppress oxidation and to reduce risk of ignition during
torch brazing. Three brazing filler metals, AWS BMg-1,
P430Mg, and P380Mg, allow electrolytic oxidation as
a finishing treatment for corrosion protection of brazed
components.
A typical tensile strength for brazed joints of magnesium alloys is in the range of 83 MPa to 117 MPa
(12 ksi to 17 ksi), depending on design, brazing filler
metal, and thickness of the joint. Typical shear strength
of brazed joints in magnesium-base metals is in the
range of 50 MPa to 70 MPa (7.2 ksi to 10 ksi) with a
joint overlap of 3 mm to 5 mm (0.12 in. to 0.2 in.). 34
Prebraze Cleaning
As with other metals, the workpieces should be thoroughly clean and free of burrs. All dirt, oil, or grease
should be removed by vapor or solvent degreasing. Surface films, such as chromates or oxides, should be
removed by mechanical or chemical cleaning. Abrasive
cloth or steel wool is satisfactory for mechanical cleaning. Chemical cleaning should consist of immersion in
hot alkaline cleaner, followed by immersion in a suitable
cleaner to remove the alkaline residue, e.g., chromate
pickling (refer to Table 2.9).
Pickling with hydrofluoric acid is a very effective
method for the surface preparation of magnesium
alloys. This method results in the formation of a magnesium fluoride (MgF2) film on the surface to be brazed,
which temporarily protects magnesium from oxidation,
and also improves wetting by magnesium-base and
magnesium-indium-zinc filler metals, as well as different
solders.35
AWS WELDING HANDBOOK
Table 2.32
Composition and Melting Point
of Magnesium Brazing Fluxes
Applicable
Brazing Processes
Flux Composition, %
Torch
KCl
45
NaCl
26
LiCl
23
Torch, dip, furnace
NaF
6
KCl
42.5
NaCl
10
LiCl
37
NaF
10
AlF3-3NaF
Approximate
Melting Point
538°C (1000°F)
388°C (730°F)
0.5
The composition and melting point of several suitable brazing fluxes are shown in Table 2.32. The fluxes
in this table meet the requirements of AWS brazing flux
FB2-A, which is used when brazing magnesium base
metals with magnesium brazing filler metals. 38 Because
of the corrosive nature of the flux, the complete
removal of flux residues is extremely important if good
corrosion resistance is to be maintained in the brazed
joints. Flux must be completely dried (sometimes by
additional heating) before torch brazing to avoid the
formation of magnesium hydroxide on the surfaces of
the brazement. The presence of magnesium hydroxide
makes quality brazing difficult and impractical to
achieve.
Fluxes
Chloride-base fluxes, similar to those used for oxyfuel gas welding, can be used for brazing magnesium
alloys. These fluxes are based on halogen salts of alkali
and alkali-earth metals with lithium chlorine (LiCl) or
sodium fluoride (NaF), or both, as active components.36 The so-called contact-reactive fluxes can also
be effective because they deposit a thin zinc film that
promotes the wetting of a fluxed magnesium surface by
the molten brazing filler metal.37
34. Busk, R. S., 1987, Magnesium Products Design, New York: International Magnesium Association, 93–100.
35. Watanabe, T., and H. Adachi, 2004, Effect of Halogen Surface
Treatment on the Ultrasonic Weldability and Brazeability of Magnesium Alloys, Journal of Japan Institute of Light Metals 54: 182–186.
36. Watanabe, T., S. Komatsu, and K. Oohara, 2005, Development
of Flux and Filler Metal for Brazing Magnesium Alloy AZ31B, Welding
Journal, 84(3): 37-s–40-s.
37. Shapiro, A. E., 2005, Brazing Magnesium Alloys and Magnesium
Matrix Composites, Welding Journal, 84(10): 33–43.
BRAZING PROCEDURES
Brazing procedures for furnace brazing, torch brazing, and dip brazing of magnesium and magnesium
alloys are described in this section. Recommendations
for temperature selection and postbraze cleaning are
included.
Furnace Brazing
Electric or gas furnaces with automatic temperature
controls capable of holding the temperature with the
accuracy ±6°C (±11°F) of the brazing temperature
should be used. A special atmosphere is not required.
38. American Welding Society (AWS) Committee on Filler Metals
and Allied Materials, 2003, Specification for Fluxes for Brazing and
Braze Welding, AWS A5.31M/A5.31:2012, Miami: American Welding
Society.
AWS WELDING HANDBOOK
Sulfur dioxide (SO2) or products of combustion in gasfired furnaces (used during heat treatment of magnesium) must be avoided because these products will
inhibit the flow of brazing filler metal.
The workpieces should be assembled and the filler
metal preplaced in or around the joint. Joint clearances
of 0.10 mm to 0.25 mm (0.004 in. to 0.010 in.) should
be used to provide good capillary flow of the brazing
filler metal. Best results are obtained when dry powdered flux is distributed along the joint. Flux pastes
made with water or alcohol will retard the flow of brazing filler metal. Flux pastes made with benzol, toluene,
or chlorbenzol can be used, but they are more difficult
to apply because these pastes are not smooth.
Flux pastes should be dried by heating the assembly
to 175°C to 205°C (350°F to 400°F) for 5 min to 15 min
in drying ovens or circulating air furnaces. Flame drying
is not recommended because improper oxyacetylene
flame adjustment can cause a heavy deposit of soot.
Brazing time depends on the metal thickness at the
joint and the amount of fixturing necessary to position
the workpieces. The time should be the minimum necessary to obtain complete filler metal flow with minimum
diffusion between the filler and base metals. One to two
minutes at the brazing temperature is sufficient. To minimize distortion after brazing, the brazement should be
allowed to air cool away from drafts.
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
195
Dip Brazing
Dip brazing is accomplished by immersing the
assembly into a bath of molten brazing flux held at
brazing temperature. In dip brazing, the molten flux
serves the dual function of heating and fluxing. To
minimize incipient melting, temperature control should
be accurate to within the range of ±6°C (±11°F) of the
preferred brazing temperature. Joint clearance should
be from 0.10 mm to 0.25 mm (0.004 in. to 0.010 in.).
After preplacing the filler metal, the workpieces
should be assembled in a brazing fixture, preferably one
constructed from stainless steel, which resists the
corrosive action of the flux. The fixtured assembly
is preheated in a furnace to a temperature between
450°C and 480°C (850°F and 900°F), which will help
minimize distortion and reduce the time in the flux
bath. Immersion time required in the flux bath should
be relatively short, because the preheated workpiece
will be heated rapidly by the molten flux. For example,
a magnesium alloy sheet that is 1.6 mm (0.062 in.)
thick can be heated to brazing temperature in 30 s to
45 s. Large assemblies with fixturing can require
immersion for 1 min to 3 min. Because of the uniform
heating created by the large volume of flux used in dip
brazing, more consistent braze quality can be achieved
with this process than with other brazing processes.
Brazing Temperature. The liquidus temperature
Torch Brazing
Torch brazing is done with a neutral oxyfuel gas or
air-fuel gas flame. Natural gas or propane is well suited
for torch brazing because relatively low flame temperatures are characteristic of these gases. The brazing filler
metal can be placed on the joint and fluxed before heating or it can be face fed. Considerable skill is necessary
for the face feeding of brazing filler metal because the
solidus temperature of the base metal and the temperature at the flow point of the brazing filler metal are very
close together. Flux pastes can be made with either
water or alcohol; pastes made with alcohol provide better results.
Heat should be applied to the joint until the filler
metal melts and flows into the joint. The base metal
should be heated by directing the torch toward the base
metal but away from the area of applied brazing filler
metal. This will avoid contact of the flame with the surface to be wetted. If the joint overlap is large, flux
should be supplied not only from the side on which the
brazing filler metal has been applied, but also from the
opposite side of the joint. The brazing filler metal
should be melted primarily by heat conducted through
the base metal; however, operators should avoid overheating the base metal because rapid diffusion and
drop-through of the metal can take place.
of the brazing filler metal selected should be as low as
possible compared to solidus temperature of the
base metal. Usually, the lowest permissible brazing
temperature is preferred to achieve the following results:
1. Minimize the effects of heat (e.g.,
recrystallization, grain growth, and distortion in
the base metal);
2. Minimize base metal and braze metal
interactions;
3. Increase the service life of fixtures and
tooling; and
4. Economize on the heat energy required.
Higher brazing temperatures are preferred when one or
more of the following objectives are to be accomplished:
1. Combine annealing, stress relief, or heat
treatment of the base metal with brazing;
2. Permit subsequent processing at elevated
temperatures;
3. Promote interactions of base metal with brazing
filler metal to modify the brazing filler metal (a
technique typically used to increase the remelt
temperature of the joint);
4. Effectively remove surface contaminants and
oxides with vacuum brazing or atmosphere
brazing; and
196
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
Postbraze Cleaning. Complete removal of flux from
the brazed workpiece is required to avoid subsequent
corrosion. Regardless of the brazing process used, the
removal of all traces of flux is vital. Brazed components
should be rinsed thoroughly in flowing hot water to
remove flux from the surface. A stiff-bristled brush can
be used to scrub the surface for fast removal of flux.
The brazed joint is then given a one-to-two minute
immersion in a chrome pickle, followed by two hours in
a boiling flux-removing cleaner. (Refer to Table 2.9 for
the composition of cleaning solutions.) The corrosion
resistance of brazed joints depends primarily on complete flux removal.
SOLDERING
Bare magnesium alloys can be soldered only by
using an abrasion method or ultrasonic soldering (USS).
Both methods involve the mechanical disruption of the
oxide film shown on the faying surfaces of the workpieces. A suitable flux is not available that will remove
these oxides and permit the solder to wet these surfaces.
Abrasion soldering is a technique during which surface
wetting is enhanced by abrading the faying surfaces.39, 40
Ultrasonic soldering is a process in which high-frequency vibratory energy is transmitted through molten
solder to remove unwanted surface films and thereby
promote wetting of the base metal. This is usually
accomplished without flux.
Conventional heating methods and tools, including
soldering irons and gas torches, can be used. Soldering
is not recommended if the service requirements of the
joint involve withstanding moderately high stress, as
soldered joints are low in strength and ductility. Soldered joints are also unsatisfactory for service in the
presence of an electrolyte, because of the considerable
difference in electrode potential between the magnesium and the soldering filler metal that can lead to
severe galvanic attack. A suitable protective coating
(e.g., a phosphate coating) should be applied to soldered joints for improved performance in service.
SOLDERING FILLER METALS
The soldering filler metals listed in Table 2.33 are
used for joining magnesium alloys. Soldering filler met39. Refer to Chapter 13, Soldering, in American Welding Society
(AWS) Welding Handbook Committee, 2004, Welding Processes, Part
1, ed. A. O’Brien, vol. 2, Welding Handbook, 9th ed., Miami: American Welding Society. See Appendix B of this volume for a detailed
description of chapter contents for the five volumes of Welding Handbook, 9th ed.
40. Vianco, P. T., 1999, Soldering Handbook, 3rd ed., Miami: American
Welding Society.
AWS WELDING HANDBOOK
als containing lead can be used, such as the 50 wt %
tin-50 wt % lead alloy, but severe galvanic attack can
take place in the presence of moisture. The tin-zinc filler
metals have lower melting points and better wetting
characteristics than the tin-zinc-cadmium solders, but
the tin-zinc filler metals can produce joints with low
ductility. Soldering filler metals of both the tin-zinc and
tin-cadmium systems with high tin content (e.g., Sn9Zn alloy and Sn-28Cd alloy) tend to produce brittle
joints due to the formation of coarse intermetallic
phases at the base-metal interface. The soldering filler
metals with high cadmium content produce the strongest and most ductile joints because the formation of
intermetallic compounds is avoided.41
Soldering filler metals from the magnesium-zinc and
magnesium-zinc-aluminum alloy systems that do not
require flux were developed and tested for ultrasonic
soldering. The composition and melting range of some
of these soldering filler metals are shown in Table 2.34.
Joints made with these filler metals exhibit satisfactory
shear strength, with corrosion resistance only slightly
below that of the base metal, Alloy AZ31B.42 The shear
strength of soldered joints in Alloy AZ31B made with
the 40Mg-50Zn-10Al soldering filler metal is in the
range of 30 MPa to 47 MPa (4.4 ksi to 6.8 ksi). Aluminum or zinc coatings greater than 150 microns thick,
applied by thermal spraying or cold gas spraying, significantly improve corrosion protection of soldered joints.
Soldering Procedure
To prepare for soldering, the faying surfaces of magnesium alloy workpieces should be degreased with a
suitable solvent and then mechanically cleaned immediately before soldering. A clean stainless steel wire brush,
stainless steel wool, or aluminum oxide cloths are suitable abrasives.
Soldering of bare magnesium alloys without flux is
limited to fillet joints and to the filling of surface defects
in noncritical areas of wrought and cast products prior
to painting. Bare magnesium surfaces must be precoated with a soldering filler metal that has good wetting characteristics. A filler metal pre-coating can be
applied using abrasion soldering, which entails rubbing
the soldering filler metal stick, soldering iron, or other
tool on the magnesium base metal to break up the oxide
film under the molten soldering filler metal.
The ultrasonic technique of pre-coating consists of
applying to the faying surfaces a hot soldering bit
vibrating at ultrasonic frequencies of at least 20 kHz.
When in contact with the molten soldering filler metal
on the magnesium, the vibration causes an abrasive
41. Vianco, P. T., 1999, Soldering Handbook, 3rd ed., Miami: American Welding Society, 275–280.
42. Wielage, B., and S. Mücklich, 2006, Improving the Soldering of
Magnesium Alloys, Welding Journal, 85(9): 48–51.
AWS WELDING HANDBOOK
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
197
Table 2.33
Soldering Filler Metals for Flux Soldering of Magnesium Alloys
Melting Range
Solidus
Composition, wt %
Liquidus
°C
°F
°C
°F
Use
Commercial Solders
91Sn-9Zn
199
390
199
390
60Sn-40Zn
199
390
341
645
80Sn-20Zn
199
390
270
580
70Sn-30Zn
199
390
311
592
50Sn-50Pb
183
361
211
421
Filler solder on precoated surface
High temperature—above 150°C
High temperature—above 150°C
Precoating solder
Non-Commercial Solders
90Cd-10Zn
265
509
299
570
72Sn-28Cd
177
350
243
470
60Cd-30Zn-10Sn
157
315
288
550
40Sn-33Cd-27Zn
Low temperature—below 150°C
Filler solder
Table 2.34
Soldering Filler Metals for Ultrasonic,
Flux-Free Soldering of Magnesium Alloys
Melting Range
Solidus
Liquidus
Composition, in wt %
°C
°F
°C
°F
40Mg-60Zn
342
648
349
660
40Mg-55Zn-15Al
338
640
343
646
40Mg-50Zn-10Al
338
640
433
812
96Zn-3Mg-1Al
338
640
400
752
effect known as cavitation erosion, which dislodges surface oxide and permits wetting. Immediately after the
surfaces are pre-coated with soldering filler metal, the
joint can be soldered using a soldering iron, torch, or
hot plate.
Conventional joints in magnesium can be prepared
for soldering by electroplating the faying surfaces of the
joint. Electroplated surfaces are soldered using procedures specified for the deposited metal. Electroplated
coatings of silver, nickel, nickel-gold, or hot-dipped
coatings of tin or tin-lead provide a good soldering
base. The first step in plating magnesium is a zinc
immersion, which provides a zinc coating. This is fol-
lowed by copper plating with a thickness of 0.0025 mm
to 0.0051 mm (0.0001 in. to 0.0002 in.), which provides a solderable surface.
Tin plating or silver plating can also be used for this
purpose. Fusing a tin coating improves the protective
value; this technique consists of electroplating and
then applying a coating of tin that is 0.0076 mm to
0.0127 mm (0.0003 in. to 0.0005 in.) thick over a copper electroplated surface. The workpiece is then
immersed in a hot oil bath to promote the flow of the
tin coating and close the pores. This technique is commonly used to facilitate the soldering of magnesium
electronic components.
Corrosion Resistance of Brazed or
Soldered Joints
The corrosion resistance of brazed or soldered joints
depends primarily on the thoroughness of flux removal
and the adequacy of the joint design to prevent flux
entrapment. Galvanic corrosion of brazed joints is minimized when magnesium-base or zinc-base soldering
filler metal or brazing filler metal is used; aluminumbased brazing filler metals, especially those containing
copper, and tin-base soldering filler metals require additional surface treatment to protect against corrosion in
air and water. If necessary, corrosion resistance of
brazed or soldered assemblies can be improved with a
phosphate coating that is chemically deposited.
198
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
AWS WELDING HANDBOOK
JOINING OF DISSIMILAR
METALS
Magnesium can be joined to other metals, such as
steel and aluminum. For example, magnesium alloy
AZ31B and coated DP600 steel were welded using the
resistance spot welding process, resulting in weld
strength similar to that of magnesium-to-magnesium
joints. In this case, a domed electrode was used against
the magnesium side and a flat electrode was used
against the steel side to avoid melting the steel, as
shown in Figure 2.39. The resulting joint was really a
mixture of soldering, brazing, solid-state, and fusion
welding, as shown in the micrograph in Figure 2.40. In
Region (A) of the micrograph, soldering of magnesium
to steel by zinc-base filler metal is evident. In Region
(B), magnesium was partially melted and the joint was
actually formed by a combination of solid-state and
fusion welding. In region (C), magnesium alloy was
melted to form a nugget and braze welded to steel.43
Detailed analysis has indicated that a transition layer,
Fe2All5 (refer to Figure 2.40) is crucial when welding
43. Includes the following works: Liu, L., L. Xiao, J. C. Feng, Y. H.
Tian, S. Q. Zhou, and Y. Zhou, 2010, The Mechanisms of Resistance
Spot Welding of Magnesium to Steel, Metallurgical and Materials
Transactions, A, 41(10): 2651–2661. Nasiri, A. M., L. Li, H. H. Kim,
Y. Zhou, D. C. Weckman, and T.C. Nguyen, 2011, Microstructure
and Properties of Laser Brazed Magnesium to Coated Steel, Welding
Journal, 90: 211s–219s. Kore, S., J. Imbert, M. J. Worswick, and Y.
Zhou, 2009, Electromagnetic Impact Welding of Mg to Al Sheets,
Science and Technology of Welding and Joining, 14(6): 549–553.
Figure 2.40—Cross Section of
Magnesium-to-Steel Weld Revealed
by a Scanning Electron Microscope
magnesium to steel, because little mutual solubility
exists between magnesium and steel, and this layer can
form semi-coherent interfaces on both the magnesium
and steel sides.44 A similar phenomenon was also observed
in laser brazing of magnesium to steel.
PLASMA ARC CUTTING
Magnesium alloys can be cut with a plasma arc cutting torch with the use of an argon-hydrogen mixture
for the orifice gas and shielding gas. A mixture of 80%
argon and 20% hydrogen (by volume) is recommended
for manual operation, whereas a mixture of 65% argon
and 35% hydrogen (by volume) is recommended for
automatic cutting. Typical conditions for automatic
cutting are shown in Table 2.35. An exhaust system is
needed because large amounts of fume are generated
during cutting.45
Source: Liu, L., L. Xiao, J. C. Feng, Y. H. Tian, S. Q. Zhou, and Y. Zhou, 2010, Metallurgical
and Materials Transactions, A, 41(10): 2651–2661.
Figure 2.39—Schematic Setup for the Resistance
Spot Welding of Magnesium to Steel
44. Liu, L., L. Xiao, J. Feng, L. Li, S. Esmaeili, and Y. Zhou, 2011,
Bonding of Immiscible Mg and Fe via a Nanoscale Fe2Al5 Transition
Layer, Scripta Materialia, 65(11), 982–5.
45. Refer to Chapter 15, Plasma Arc Cutting and Gouging, in American Welding Society (AWS) Welding Handbook Committee, 2004,
Welding Processes, Part 1, ed. A. O’Brien, vol. 2, Welding Handbook,
9th ed., Miami: American Welding Society. See Appendix B of this
volume for detailed descriptions of chapter contents for the five volumes of Welding Handbook, 9th ed.
AWS WELDING HANDBOOK
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
199
Table 2.35
Typical Conditions for Automatic Plasma Arc Cutting of Magnesium Alloy Plate a
Thickness
Plasma
Cutting Speed
Shielding Gas Flowb
mm
in.
Current
(DCEP), A
Voltage, V
mm/s
in./min
L/min
ft3/h
Remarks
6.4
0.250
200
60
95
225
33
70
Minimum fume
6.4
0.250
400
75
64
150
33
70
Squarest cut
6.4
0.250
400
80
127
300
33
70
Maximum speed
12.7
0.500
240
60
64
150
33
70
12.7
0.500
420
75
42
100
47
100
Squarest cut
Minimum fume
12.7
0.500
460
70
127
300
47
100
Maximum speed
25.4
1
300
75
25
60
33
70
Minimum fume
25.4
1
450
80
25
60
47
100
Squarest cut
25.4
1
660
80
32
75
47
100
Maximum speed
50.8
2
350
100
10.6
25
47
100
Minimum fume
50.8
2
520
100
10.6
25
47
100
Squarest cut
50.8
2
600
90
21
50
47
100
Maximum speed
101.6
4
500
210
5
12
94
200
Squarest cut
152.4
6
750
225
5
12
142
300
Squarest cut
a. AZ31B magnesium alloy.
b. 65% argon and 35% hydrogen.
APPLICATIONS
Magnesium and magnesium alloy applications, welding procedures, and joint designs (refer to Figure 2.1)
are quite similar to those of other metals, especially aluminum and aluminum alloys. As noted previously,
attention must be directed to reactivity (primarily oxidation) during welding, cracking due to restraint, filler
metal selection, welding and preheat procedures, and
the welding process. Another important consideration
is postweld behavior relating to galvanic and stress corrosion tendencies in service or after repair welding.
PROCESS SELECTION
The selection of a welding process is dependent on a
variety of factors. Welding of wrought metal is primarily achieved with manual and automatic gas tungsten
arc welding (GTAW) and gas metal arc welding
(GMAW). The commonplace repair welding of castings
requires manual GTAW, which can be carefully
controlled to avoid restraint cracking and distortion
problems. The selection of a welding process or procedure
is often influenced by considerations other than purely
technical factors, such as:
1. The quantity to be fabricated (short-run
prototype or longer production run);
2. Whether or not tack welding can be used in
place of more costly fixturing;
3. In-house familiarity with applicable processes
and procedures; and
4. In-house availability of preferred processes
and associated equipment.
Applications in this section include the welding of
tailored blanks for an automobile engine hood and a
dashboard configuration using laser beam welding.
Details of the automobile hood welding are shown in
Figure 2.41; the dashboard is shown in Figure 2.42.
The gas tungsten arc process was used to weld a
component for a rail car, shown in Figure 2.43,
and a mountain bicycle frame, shown in Figure 2.44.
200
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
AWS WELDING HANDBOOK
(A) Tailored Blank
(B) Surface Weld
(C) Back Weld
(D) Microstructures of the Welded Joint
Figure 2.41—(A) Laser Beam Welds in Strip-Cast and WarmRolled AZ31 Tailored Blank for an Automobile Engine Hood,
Welded from
Both Sides; (B) Surface Weld; (C) Back Weld; and
AWS WELDING HANDBOOK
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
201
Photograph courtesy of POSCO
Figure 2.42—Tailored Blank for an Automobile
Dashboard, Strip-Cast and Warm-Rolled AZ31,
Welded Using Nd:YAG Laser Beam
(1.5 kW, 3 m/min, δ = –2.0 mm)
Photograph courtesy of POSCO
Figure 2.43—Component Used in the Frame of
a Rail Car Welded Using the Gas Tungsten
Arc Process at 110 A with Argon Shielding
Joint surfaces for the automobile hood and dashboard were prepared using a cleaning agent consisting
of ethyl alcohol 100 ml, distilled water 100 ml, acetic
acid 10 ml, and picric acid 1 g.
Manual Gas Tungsten Arc Welding of an
Electronic Deck Assembly
On short production runs of an application, for
example, the electronic deck assemblies diagrammed in
Photograph courtesy of Paketa Bikes
(A) Mountain Bicycle Frame
Micrograph courtesy of POSCO
(B) Bicycle Frame Weld after Fatigue Test
Figure 2.44—(A) Mountain Bicycle Frame Welded
Using Gas Tungsten Arc Process at 110A with
Argon Shielding and (B) Macrograph of
the Weld after Fatigue Test
Figure 2.45, tack welds were used instead of fixtures to
position some of the components to minimize tooling
costs. The assemblies were essentially two rectangular
boxes 50 mm × 50 mm × 100 mm (2 in. × 2 in. × 4 in.) as
shown in Figure 2.45(A). Formed sheet sections of Alloy
AZ31B–H24 with a thickness of 1.27 mm (0.050 in.) were
tack welded into position using GTAW and RAZ61A
welding wire with a diameter of 1.6 mm (0.062 in.),
202
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
h
AWS WELDING HANDBOOK
B
2h
C
d
w
WELD
(A) AZ31B-H24 Deck Assembly
Mechanized Welding of Extruded Door
Frames
t
WELD METAL
t
BEFORE WELDING
Airtight doors for an aerospace application were
made by welding panels of Alloy AZ31B–H24 sheet to
AFTER WELDING
(B) Detail B (in welding position)
t
BEFORE WELDING
as detailed in 2.45(B). The tack welds were 3.2 mm
(0.125 in.) long and were spaced on 50 mm (2.0 in.)
centers, starting at each corner. A tool plate and toggle
clamp held the pieces for tack welding. Tack welds were
not needed to hold the angled pieces during welding.
The corner joints, shown in Figure 2.45(C), were
welded with continuous beads about 50 mm (2 in.)
long, and the flanged bottom of the top part of the
assembly was joined to the sides with fillet welds 25 mm
(1.0 in.) long. Fillet welds about 25 mm (1 in.) long
were used to join the extruded angle sections to the
ends of the boxes. Welding of the assembled and tackwelded components was completed by manual GTAW
under the conditions shown in Table 2.36.
The assembly was repositioned manually so that all
welds could be made in either the flat or the horizontal
position. A standard alternating current power source
with a high-frequency arc stabilizer was used. Helium
was selected as the shielding gas because a hotter and
more stable arc was produced than would have been
possible with argon shielding gas. Preheating was not
used, but after welding, the assemblies were stress
relieved at 180°C (350°F) for 3.5 h to prevent stresscorrosion cracking. Welds were inspected visually.
AFTER WELDING
(C) Detail C (in welding position)
Note: h = 51 mm (2 in.); w = 51 mm (2 in.);
Figure 2.45—Detail for Manual Gas
Tungsten Arc Welding of AZ31B-H24
Electronic Deck Assembly
Table 2.36
Conditions for Manual Gas Tungsten
Arc Welding of Electronic Deck Assembly
Joint types
Lap and corner
Weld types
Fillet and single-V-groove
Welding positions
Horizontal and flat
Preweld cleaning
Wire brushing
Preheat
None
Fixtures
Tool plate and toggle clamps
Shielding gas
Helium, at 11.8 L/min (25 ft3/h)
Electrode
1.0 mm (0.040 in.) diameter EWP
Filler metal
1.6 mm (0.062 in.) diameter R AZ61Aa
Torch
350 A, water cooledb
Power source
300-A transformerc
Current, fillet welds
25 A, ac
Current, V-groove welds
40 A, ac
Postweld heat treatment
177°C (350°F) for 3.5 h
a. Rod, 914 mm (36 in.) long.
b. Ceramic nozzle.
c. Continuous duty, with high-frequency oscillator.
AWS WELDING HANDBOOK
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
203
PANEL
w
t
t
45°
JOINT A
FRAME
JOINT A DETAIL
(BEFORE WELDING)
WELDED ASSEMBLY
(A) Curved Airframe Door Design
PANEL
w
t
t
45°
OFFSET LIP
JOINT B
FRAME
JOINT B DETAIL
(BEFORE WELDING)
WELDED ASSEMBLY
(B) Straight Airframe Door Design
Notes:
1. Frames are alloy AZ31B extrusions.
2. Panels are alloy AZ31B sheet.
3. Filler metal is magnesium alloy ER AZ61A.
4. t = 1.6 mm (0.062 in.); w = approximately 0.9 m (3 ft).
Figure 2.46—Mechanized Gas Tungsten Arc Welding of Extruded Door Frames
frames extruded from Alloy AZ31B. The frames acted
as stiffeners and also contained a groove for an air seal.
Cross sections of similar offset butt joints in two door
assembly designs are shown in Figure 2.46(A) and (B).
The offset lip of the extruded frames facilitated a single-bevel groove butt joint and served as backing for the
weld; the lap joint on the underside was not welded.
Welding conditions are shown in Table 2.37.
Although production quantities were low, mechanized gas tungsten arc welding was used because weld
quality was good and the equipment was available.
Automatic travel was obtained by mounting the welding equipment on the motorized carriage of a cutting
machine. Differences in welding conditions for the two
joints (refer to Table 2.36) were the result of the welding operator’s choice. Both procedures produced satisfactory welds, but the difference in welding speeds
would be significant for large production quantities.
Repair Welding of a Jet Engine Casting
During an aircraft jet engine overhaul, a fluorescentpenetrant inspection revealed a crack near a rib in the
cast AZ92A-T6 compressor housing shown in Figure 2.47.
The crack was 63.5 mm (2.5 in.) long; the thickness of
the section containing the crack ranged from 4.8 mm to
204
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
AWS WELDING HANDBOOK
Table 2.37
Conditions for Automatic Gas Tungsten
Arc Welding of Extruded Door Frames
Joint type
Offset butt
Weld type
Single-bevel groove
Preweld cleaning
Chromic-sulfuric pickle
Welding position
Flat
Preheat
None
Shielding gas
Argon, 8.5 L/min (18 ft3/h) for Joint A;
Argon, 7.5 L/min (16 ft3/h) for Joint B
Electrode
3.2 mm (0.125 in.) diameter EWP
Filler metal
1.6 mm (0.062 in.) diameter ER AZ61A
Torch
Water cooled
Power source
300 A ac (HF-stabilized)
Current (ac)
175 A for Joint A; 135 A for Joint B
Wire feed rate
27.5 mm/s (65 in./min)
Travel speed
8.4 mm/s (20 in./min) for Joint A;
6.3 mm/s (15 in./min) for Joint B
Postweld heat treatment
177°C (350°F) for 1.5 h
RIB
(1 of 16)
h
B
B
t
REPAIR
WELD, L
(A) AZ92A-T6 Housing with Repair Weld
60°
WELD METAL
ro
7.9 mm (0.188 in. to 0.313 in.). Repair welding was
permissible according to specifications. The welding
conditions are shown in Table 2.38.
The component was degreased with vapor to remove
surface grease and dirt and was soaked in a commercial
alkaline paint remover. The crack was then marked
with a felt-tip marker, and the component was stress
relieved at 200°C (400°F) for 2 h. The crack was
removed by slotting the flange through to the periphery.
Each side of the slot was beveled to approximately 30°
from vertical to form a 60° double-V-groove. The area
to be welded was cleaned with an electric brush with
stainless steel wire bristles. The crack was repair welded
using manual GTAW, with no preheating.
The welding procedure was to maintain a lowamperage arc (less than 70 A) directed onto the base
metal while filler metal was deposited on the sides of
the groove, working from the innermost point outward.
After a weld pool formed, the arc was oscillated slightly
while depositing a bead on the sides of the groove. During welding, heat input was adjusted by a foot-operated
current control to maintain a uniform weld pool. After
welding was completed on one side of the slot, the casting was turned over. Excess drop-through and areas of
incomplete joint penetration were removed by grinding.
The underside was then welded using the same procedure as that used for the upper side. After welding, the
casting was stress relieved at 200°C (400°F) for 2 h and
inspected with the fluorescent-penetrant method.
BEFORE WELDING
AFTER WELDING
(B) Section B-B Detail
Notes:
1. Housing height, h = 237 mm (9.33 in.);
diameter, d = 555 mm (21.84 in.).
2. Repair weld length, L, is approximately 64 mm (2.5 in.).
3. Thickness, t = 4.8 mm to 7.9 mm (0.188 in. to 0.313 in.);
root opening, ro = 2.4 mm (0.096 in.).
Source: Adapted from ASM International, 1993, ASM Handbook, Vol. 6, 10th ed., Materials
Park, Ohio: ASM International, p. 781.
Figure 2.47—Repair Welding of a
Compressor Housing in a Jet Aircraft Engine
Solder Repair of Castings
Soldering can be used to repair discontinuities in
magnesium castings, such as local porosity, short-run
pouring defects, pin-holes, cracks, erosion scabs,
incomplete formation of thin walls or profile, and others. An example of local porosity is exhibited in the
magnesium casting shown in Figure 2.48(A). Soldering
filler metals, such as AZn-8Al-4Cu-0.2Zr (proprietary
AWS WELDING HANDBOOK
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
205
Table 2.38
Conditions for Manual Gas Tungsten
Arc Welding of Compressor Housing
Joint design
Butt
Weld type
60° double-V-groove repair
Shielding gas
Argon, 9.4 L/min (20 ft3/h)a
Electrode
1.6 mm (0.062 in.) diameter EWTh-2
Filler metal
1.6 mm (0.062 in.) diameter R AZ101A
Torch
Water cooled
Power source
300 A transformer, with high-frequency
start
Current
Under 70 A, acb
Postweld stress relief
204°C (400°F) for 2 hc
Inspection
Fluorescent penetrant
(A)
a. Also used for backing.
b. Current was regulated by a foot switch.
c. Also preweld.
name TiBr 350) with a melting range of 380°C to
405°C (716°F to 761°F), or Zn-4Al-3Cu-0.2Nb (proprietary name: TiBr 330) with a melting range of 330°C
to 380°C (626°F to 716°F) are suitable for this purpose.46
For this type of application, the surfaces of the workpieces should be prepared by degreasing with acetone
or gasoline or mechanically cleaned with a steel brush
or file. Deep casting defects should be mechanically
abraded with a drill bit, metal wire brush, or a burr
mill. The surface of the workpiece is then heated with a
propane torch to a temperature in the range of 450°C
to 500°C (840°F to 930°F) for soldering with Zn-8Al4Cu-0.2Zr, or 400°C to 450°C (750°F to 840°F) for
soldering with Zn-4Al-3Cu-0.2Nb. When the correct
temperature is reached, the soldering filler metal rod is
inserted into the flame and melted in direct contact with
the hot base metal. The soldering operator uses a rubbing motion of the soldering filler metal rod to flow the
molten soldering filler metal into the base metal to fill
out the casting defects or discontinuities while continuing to heat the base metal. After soldering, the castings
are slowly cooled in air, without a fan or water quench.
After soldering, excess soldering filler metal is removed
from the surface of the casting with a file, metal brush,
or abrasive.
Finally, the repaired magnesium casting is again subjected to a standard phosphate pickling, which deposits
46. Shapiro, A. E., and E. Y. Ivanov, 2007, Healing of Magnesium
Casting Defects by Flux-Free Soldering with Zn-Based Solders, DVS
Berichte, vol. 243, 215–217.
(B)
(C)
Figure 2.48—Repair of Local Porosity on Cast
Ring of Magnesium Alloy AZ91C: (A) Local
Porosity on Cast Ring of Magnesium Alloy AZ91C,
(B) Porosity
Filled with Zn-4Al-3Cu-0.2Nb Soldering Filler
Metal, and (C) Anticorrosive Aluminum-Spray
206
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
a protective coating to prevent atmospheric corrosion.
Aluminum applied by thermal spraying is also suitable
to coat and protect a soldered surface. Figure 2.48(B)
shows an example of a thermal spray deposit on a magnesium casting. The repaired casting is shown in Figure
2.48(C).
SAFE PRACTICES
The scope of this section does not include information on general welding safety, which is provided in
detail in other safety publications, but includes safety
considerations specifically related to the joining of magnesium. A few general sources are listed in this section.
The primary resource for general health and safety
related information is the standard, Safety in Welding,
Cutting, and Allied Processes, approved by the American National Standards Institute and published by the
American Welding Society. This standard can be downloaded from the Internet.47
An important resource is provided by the United
States Department of Labor in Occupational Safety and
Health Standards for General Industry (29 CFR Part
1910, Subpart Q)48 and Occupational Safety and
Health Standards for Construction (29 CFR Part 1926,
Subpart J).49
The American Conference of Governmental Industrial Hygienists (ACGIH) publishes a booklet (updated
annually) on biological exposure indices and threshold
limit values of chemical substances and physical
agents.50
Appendix A of this volume lists safety and health
standards published by the American Welding Society
and safety codes and standards published by related
associations. Facts of publication are included. General
47. American National Standards Institute (ANSI), 2005, Safety in
Welding, Cutting, and Allied Processes, ANSI Z49.1:2005, Miami:
American Welding Society. This publication is also available online at
www.aws.org.
48. Occupational Health and Safety Administration (OSHA) Title
29—Department of Labor. Occupational Safety and Health Standards for General Industry. In Code of Federal Regulations (CFR)
1910, Subpart Q. Washington, D.C.: United States Government Printing Office. www.OSHA.gov.
49. Occupational Safety and Health Administration (OSHA), Safety
and Health Standards for Construction, 29 CFR Part 1910, Subpart J.
Washington, D. C.: Superintendent of Documents, U.S. Government
Printing Office.
50. American Conference of Governmental Industrial Hygienists
(ACGIH), Threshold Limit Values for Chemical Substances and
Physical Agents and Biological Exposure Indices. Cincinnati, Ohio:
American Conference of Governmental Industrial Hygienists. www.
acgih.org.
AWS WELDING HANDBOOK
safety information is summarized in Chapter 17, Volume 1, 9th edition, of the Welding Handbook.51
PRECAUTIONS FOR WELDING
MAGNESIUM
In general, magnesium can be regarded as safe material, as long as it is not heated above the melting point;
however, magnesium chips and powder have the potential to ignite easily. In particular, Mg powder combined
with air can ignite spontaneously. Preventive measures
include limiting as much as possible the amount of Mg
powder brought into the welding area, and ensuring
that there are no open flames close to the work space.
Excess Mg powder should not be mixed with other
materials and should be stored in a sealed container.
It is critical to note that magnesium fires should not
be extinguished with water due to the spontaneous
release of hydrogen, which can result in detonation.
Sand or special foams should be used.
A risk of ignition exists when welding magnesium
alloys thinner than 0.25 mm (0.01 in.); however, the
possibility of ignition is extremely remote when welding
sections thicker than 0.25 mm (0.01 in.). Magnesium
alloy product forms will not ignite in air unless fusion
temperature is reached; then sustained burning will
occur only if the ignition temperature is maintained.
Inert gas shielding during welding prevents ignition of
the weld pool.
Fire can be caused by an accumulation of magnesium
grinding dust or fine machine chips, which can ignite.
Graphite-base (G-1) or proprietary salt-base powders
recommended for extinguishing magnesium fires should
be conveniently located in the work area. Accumulation
of grinding dust on clothing should be avoided. If large
amounts of fine particles, or fines, are produced, they
should be collected in a water-wash dust collector
designed for use with magnesium.
Special precautions pertaining to the handling of wet
magnesium fines must be followed because magnesium
dust in water also presents a hazard. Fine particles of
magnesium can react with water to form hydrogen gas,
which can collect in a bubbly froth on top of the water.
Any inadvertent heat source or spark can cause this
froth to explode. Adequate ventilation and isolation of
wet magnesium from ignition sources (e.g., storage
away from the welding area) are critical to avoiding this
problem.
51. Refer to Chapter 17 in American Welding Society (AWS) Welding
Handbook Committee, 2001, Welding Science and Technology, ed. C.
Jenney and A. O’Brien, vol. 1, Welding Handbook, 9th ed., Miami:
American Welding Society. See Appendix B of this volume for detailed
descriptions of chapter contents for the five volumes of Welding
Handbook, 9th ed.
AWS WELDING HANDBOOK
Machining magnesium for weld joint preparation
also requires special attention and the use of water-free
lubricants. Dry machining of magnesium is preferred,
but a light mineral oil can be used if needed. Magnesium can react with water or water-emulsified oil at elevated temperatures (i.e., during cutting) to form
hydrogen, which can burn and serve to ignite machine
chips. Graphite powder fire retardant should be kept in
the work area. Magnesium chips resulting from
machining should be collected, segregated from other
chips, and stored or disposed of in a safe manner.
Fumes
Welding fumes from commercial magnesium alloys,
except those containing thorium, are not harmful when
the amount of fumes remains below 5 milligrams per
cubic meter ([mg/m3] [5 × 10–6 oz/ft3]). Welders should
avoid direct inhalation of fumes from the thorium-containing alloys because of the presence of alpha radiation
in the airborne particles; the concentration of thorium
in the fumes is sufficiently low so that good ventilation
or local exhaust systems will provide adequate
protection. No external radiation hazard is involved
in the handling of the thorium-containing alloys.
Some solvents, chemical baths, and fluxes used for
cleaning, welding, brazing, or finishing of magnesium
alloys contain chromates, chlorides, fluorides, acids, or
alkalis. Adequate ventilation, protective clothing, and
eye protection should be used when working with these
materials to avoid toxic effects, burns, or other injuries.
Safety precautions are summarized as follows:
1. Ensure proper ventilation of the weld area and
isolation from ignition sources (e.g., open flames);
2. Ensure that protective clothing and eye
protection are used when working with
magnesium products;
3. Ensure that graphite powder fire retardant or
proprietary salt-base powder recommended
for extinguishing a magnesium fire is readily
available in the immediate work area;
4. Use inert gas shielding during welding to prevent
ignition of the weld pool;
5. To the extent possible, limit the amount of
Mg powder brought into the welding area.
Keep excess powder separate from other
materials and stored in a sealed container away
from the welding area;
6. Avoid reaction with water to prevent the
formation of hydrogen gas at elevated
temperatures;
7. If machining is necessary to prepare joints in
magnesium, use dry machining and use a waterfree lubricant if needed; and
8. Collect and segregate magnesium machining
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
207
BIBLIOGRAPHY
Afrin, N., D. Chen, X. Cao, and M. Jahazi. 2008.
Materials science and engineering, A. 472(1-2):
179–186.
American National Standards Institute (ANSI). 2012.
Safety in welding, cutting, and allied processes. ANSI
Z49.1:2012. Miami: American Welding Society.
ASM International. 1979. In Properties and selection:
Nonferrous alloys and pure metals, Vol. 2 of Metals
handbook. 9th ed. Materials Park, Ohio: ASM International.
ASM International. 1993. Welding, brazing, and soldering. Edited by D. Olson, T. A. Siewert, S. Liu, and G.
R. Edwards. Vol. 6 of ASM handbook. 10th ed.
Materials Park, Ohio: ASM International.
ASM International. 1994. Surface engineering. Vol. 5 of
ASM handbook. 10th ed. Materials Park, Ohio:
ASM International.
American Welding Society (AWS) Committee on Brazing and Soldering. 2007. Brazing handbook. 5th ed.
Miami: American Welding Society.
American Welding Society (AWS) Committee on Definitions and Symbols. 2010. Standard welding terms
and definitions, including terms for adhesive bonding, brazing, soldering, thermal cutting, and thermal
spraying. AWS A3.0M/A3.0:2010. Miami: American
Welding Society.
American Welding Society (AWS) Committee on Filler
Metals and Allied Materials. 2006. Specification
for magnesium alloy welding electrodes and rods.
AWS A5.19-92 (R2006). Miami: American Welding
Society.
American Welding Society (AWS) Committee on Filler
Metals and Allied Materials. 2004. Specification for
filler metal for brazing and braze welding. AWS
A5.8M/A5.8:2011. Miami: American Welding Society.
American Welding Society (AWS) Committee on Filler
Metals and Allied Materials. 2003. Specification for
fluxes for brazing and braze welding. AWS A5.31M/
A5.31:2012. Miami: American Welding Society.
American Welding Society (AWS) Committee on Resistance Welding. 2006. Recommended practices for
resistance welding. AWS C1.1M/C1.1:2012. Miami:
American Welding Society.
American Welding Society (AWS) Welding Handbook
Committee. 2001. Welding science and technology.
Edited by C. Jenney and A. O’Brien. Vol. 1 of Welding handbook. 9th ed. Miami: American Welding
Society.
American Welding Society (AWS) Welding Handbook
Committee. 2004. Welding processes, part 1. Edited
by A. O’Brien. Vol. 2 of Welding handbook. 9th ed.
Miami: American Welding Society.
208
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
American Welding Society (AWS) Welding Handbook
Committee. 2007. Welding processes, part 2. Edited
by A. O’Brien and C. Guzman. Vol. 3 of Welding
handbook. 9th ed. Miami: American Welding Society.
Avedesian, M. M., and H. Baker. 1999. Magnesium and
magnesium alloys, ASM Specialty handbook, Materials Park, Ohio: ASM International.
Barnett, M. 2007. Materials science and engineering, A.
464(1-2): 8–16.
Bruni, C., G. Buffa, L. d’Apolito, A. Forcellese, and L.
Fratini. 2009. Sheet metal. eds. B. Shirvani, R.
Clarke, J. Duflou, M. Merklein, F. Micari, and J.
Griffiths, Key engineering materials. ISSN: 16629795, Vol. 410–411.
Busk, R. S. 1987. Magnesium products design. New
York: Dekker Mechanical Engineering.
Campanelli, L.C., U. F. H. Suhuddin, A. I. S. Antonialli,
J. F. dos Santos, N. G. Alcantara, and C. Bolfarini.
2013. Metallurgy and mechanical performance of
AZ31 magnesium alloy friction spot welds. Journal
of materials processing technology. Vol. 213, No. 4.
515–521.
Cao, X., and M. Jahazi, 2007. Use of laser and friction
stir welding for aerospace magnesium alloys. Proceedings, 3rd Int. Conference on Light Metals Technology, eds. K. Sadayappan and M. Sahoo, SaintSauveur, Québec, Canada, 158–163.
Cao, X., and M. Jahazi, 2008. Overview of friction stir
and laser welding techniques for lightweight alloys.
Canadian Welding Association, Journal of materials
processing technology. 19–30.
Cao, X., M. Jahazi, J. P. Immarigeon, and W. Wallace,
2006. A review of laser welding techniques for magnesium alloys, Journal of materials processing technology. 171: 188–204.
Cao, X., M. Xiao, M. Jahazi, and J. P. Immarigeon,
2005. Continuous wave Nd: YAG laser welding of
sand-cast ZE41A-T5 magnesium alloys, Material
manufacturing processes. 20: 987–1004.
Cavaliere, P., and P. D. Marco. 2007. Materials characterization journal. 58(3): 226–232.
Chang, C., X. Du, and J. Huang. 2007. Scripta materialia. 57(3): 209–212.
Charit, I., and R. Mishra. 2005. Acta materialia.
53(15): 4211–4223.
Chowdhury, S., D. Chen, S. Bhole, X. Cao, E. Powidajko, D. Weckman, and Y. Zhou. 2010. Tensile properties and strain-hardening behavior of double-sided
arc welded and friction stir welded AZ31B Magnesium Alloy, Materials science and engineering, Volume 527(12): No. 12. 2952–2961.
Chowdhury, S., D. Chen, S. Bhole, and X. Cao. 2010.
Fatigue. Procedia engineering. 2(1): 825–833.
Commin, L., M. Dumont, J. E. Masse, and L. Barrallier.
2009. Acta materialia. 57(2): 326–334.
AWS WELDING HANDBOOK
Esparza, J. A., W. C. Davis, E. A. Trillo, and L. E. Murr.
2002. Journal of material science letters. 21(12):
917–920.
Esparza J. A., W. C. Davis, and L. E. Murr. 2003. Journal of material science letters. 38(5): 941–952.
Gharacheh, M. A., A. Kokabi, G. Daneshi, B. Shalchi,
and R. Sarrafi. 2006. International journal of
machine tools and manufacture. 46(15): 1983–1987.
Hattingh, D., C. Blignault, T. van Niekerk, and M.
James. 2008. Journal of materials processing technology. 203(1-3): 46–57.
Hsu, C., P. Kao, and N. Ho. 2005. Scripta materialia
53(3): 341–345.
Hütsch, L. L., J. Hilgert, K. Herzberg, J. dos Santos,
and N. Huber. 2012. Advanced engineering materials.
14(9): 762–771.
Johnson, R., and P. Threadgill, eds. 2003. Friction stir
welding of magnesium alloys, Magnesium technology.
TMS.
Kainer, K. 2003. Magnesium alloys and technology. volume 1, Wiley-VCH.
Kainuma S., H. Katsuki, I. Iwai, and M. Kumagai.
2008. International journal of fatigue. 30(5): 870–
876.
Kannan, M. B., W. Dietzel, R. Zeng, R. Zettler, and J.
dos Santos. 2007. Materials science and engineering,
A. 460-461: 243–250.
Kostka, A., R. Coelho, J. dos Santos, and A. Pyzalla.
2009. Scripta materialia. 60(11): 953–956.
Lee, C., J. Huang, and X. Du. 2007. Nanoscale materials for hydrogen storage. Scripta materialia. 56(10):
875–878, viewpoint set no. 42.
Lee, W., Y. Yeon, and S. Jung. 2003. Journal of materials science & technology. 19: 785–790.
Lim, S., S. Kim, C. G. Lee, S. Kim, and C. Yim. 2005.
Metallurgical and materials transactions, A. 36(6):
1609–1612.
Mansoor, B., and A. Ghosh. 2012. Acta materialia.
60(13–14): 5079–5088.
Mishra, R., and Z. Ma. 2005. Materials science and
engineering research. 50(1–2): 1–78.
Mishra, R., and M. Mahoney. 2007. Friction stir welding and processing. ASM International, 1st edition.
Nandan, R., T. DebRoy, and H. Bhadeshia. 2008.
Progress in materials science. 53(6): 980–1023.
Ni, D., D. Wang, A. Feng, G. Yao, and Z. Ma. 2009.
Scripta materialia. 61(6): 568–571.
Padmanaban G., and V. Balasubramanian. 2009. International journal of advanced manufacturing technology. 49: 111–121.
Padmanaban, G., V. Balasubramanian, and J. Sarin
Sundar. 2009. Journal of materials engineering and
performance. 19: 155–165.
Pareek, M., A. Polar, F. Rumiche, and J. Indacochea.
2007. Journal of materials engineering and performance. 16(5): 655–662.
AWS WELDING HANDBOOK
Park, S. H. C., Y. S. Sato, and H. Kokawa. 2003. Journal of materials science. 38(21): 4379–4383.
Park, S. H. C., Y. S. Sato, and H. Kokawa. 2003.
Scripta materialia. 49(2): 161–166.
Park, S. H. C. Y., Sato, and H. Kokawa. 2003. Metallurgical and materials transactions, A. 34(4): 987–
994.
Peaslee, R. L., and R. L. Holdren, 2007, Brazement
design, in American Welding Society (AWS) Committee on Brazing and Soldering, 2007, Brazing handbook, 5th ed. Miami: American Welding Society. 21–
66.
Resistance Welding Manufacturing Alliance (RWMA).
2003. Resistance welding manual. 4th ed. Philadelphia: RWMA.
Rethmeier, M., B. Kleinpeter, and H. Wohlfahrt. 2004.
MIG welding of magnesium alloys—metallographic
aspects. Welding in the world. 48(3/4): 28–33.
Sato, Y. S., S. H. C. Park, A. Matsunaga, A. Honda,
and H. Kokawa. 2005. Journal of materials science.
40(3): 637–642.
Shahri, M. M., and R. Sandström. 2010. International
journal of fatigue. 32(2): 302–309.
Shapiro, A. E. 2005. Brazing magnesium alloys and
magnesium matrix composites. Welding journal.
84(10): 33–43.
Shapiro, A. E., and E. Y. Ivanov. 2007. Healing of magnesium casting defects by flux-free soldering with
Zn-based solders. DVS-Berichte. 243: 215–217.
Shapiro, A. E. 2007. Brazing of magnesium and magnesium m alloys, in American Welding Society (AWS)
Committee on Brazing and Soldering. 2007. Brazing
handbook, 5th ed. Miami: American Welding Society.
497–510.
Shtrikman, M. M. 2008. Welding international. 22(11):
806–815.
Sibley, C. R. 1962. Arc welding of magnesium and magnesium alloys. Bulletin 83. New York: Welding
Research Council.
Skar, J. I., H. Gjestland, L. D. Oosterkamp, and D. L.
Albright. 2004. Magnesium technology. 25–30.
Srinivasan, P. B., R. Zettler, C. Blawert, and W. Dietzel.
2009. Materials characterization. 60(5): 389–396.
Su, P., A. Gerlich, M. Yamamoto, and T. H. North.
2007. Formation and retention of local melted films
in AZ91 friction spot welds. Journal of materials science. 42: 9954–9965.
Suhuddin, U., S. Mironov, Y. Sato, H. Kokawa, and C.
W. Lee. 2009. Acta materialia. 57(18): 5406–5418.
Sun, N., Y. H. Yin., A. Gerlich, and T.H. North. 2007.
Mechanism of cracking in AZ91 friction stir spot
welds. Science and technology of welding and joining.
14(8): 747–752.
Thomas, W., E. Nicholas, J. Needham, M. Murch, P.
Templesmith, and C. Dawes. 1991. Friction stir
welding. Cambridge: TWI.
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
209
Thomas, W. M., C. S. Wiesner, D. J. Marks, and D. G.
Staines. 2009. Science and technology of welding
and joining 14(3): 247–253.
Tsujikawa, M., H. Somekawa, K. Higashi, H. Iwasaki,
T. Hasegawa, and A. Mizuta. 2004. Fatigue of
welded magnesium alloy joints. Materials transactions.
45(2): 419–422.
Vianco, P. T. 1999. Soldering handbook. 3rd ed. Miami:
American Welding Society.
Venkateswarlu, G., D. Devaraju, M. Davidson, B.
Kotiveerachari, and G. Tagore. 2012. Materials &
design. (45): 480–486.
Wang, D., J. Shen, and L. Wang. 2011. Effects of the
types of overlap on the mechanical properties of
FSSW welded AZ series magnesium alloy joints.
International journal of minerals metallurgy and
materials. 19(3): 231–235.
Watanabe, T., and H. Adachi. 2004. Effect of halogen
surface treatment on the ultrasonic weldability and
brazeability of magnesium alloys. Journal of Japan
institute of light metals. 54(5): 182–186.
Watanabe, T., S. Komatsu, and K. Oohara. 2005.
Development of flux and filler metal for brazing
magnesium alloy AZ31B. Welding journal. 84(3):
37-s–40-s.
Wielage, B., and S. Mücklich. 2006. Improving the soldering of magnesium alloys. Welding journal. 85(9):
48–51.
Winzer, N., P. Xu, S. Bender, T. Gross, W. E. S. Unger,
and C. E. Cross. 2009. Stress corrosion cracking of
gas-tungsten arc welds in continuous-cast AZ31 Mg
alloy sheet. Corrosion science. 51(9): 1950–1963.
Wu, G., Y. Fan, H. Gao, C. Zhai, and Y. P. Zhu. 2005.
Materials science and engineering, A. 408(1-2): 255–
263.
Xiao, L., L. Liu, Y. Zhou, and S. Esmaeili. 2010. Resistance-spot-welded AZ31 magnesium alloys, part I:
Dependence of fusion zone microstructures on second-phase particles. Metallurgical and materials
transactions, A. 41(6): 1511–1522.
Xie, G., Z. Ma and L. Geng. 2008. Materials science
and engineering, A. 486(1-2): 49–55.
Xunhong, W., and W. Kuaishe. 2006. Materials science
and engineering, A. 431(1-2): 114–117.
Yamamoto, M., A. Gerlich, T. H. North, and K. Shinozaki. 2007. Cracking in the stir zones of Mg-alloy
friction stir spot welds. Journal of materials science.
42: 7657-7666.
Yamamoto, M., A. Gerlich, T.H. North, and K. Shinozaki. 2007. Mechanism of cracking in AZ91 friction stir spot welds. Science and technology of
welding and joining. 12(3): 208–216.
Yang, J., B. Xiao, D. Wang, and Z. Ma. 2010. Materials
science engineering, A. 527(3): 708–714.
Yuan, W., R. S. Mishra, B. Carlson, R. Verma, and R.
K. Mishra. 2012. Materials flow and microstructural
210
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
evolution during friction stir spot welding of AZ31
magnesium alloy. Materials science and engineering,
A. 543: 200–209.
Yuan, W., R. Mishra, B. Carlson, R. Mishra, R. Verma,
and R. Kubic. 2011. Scripta materialia. 64(6): 580–
583.
Zeng, R. C., J. Chen, W. Dietzel, R. Zettler, J. dos Santos, M. L. Nascimento, and K. U. Kainer. 2009. Corrosion science. 51(8): 1738–1746.
Zhang, B. P., Y. F. Tu, J. Y. Chen, H. L. Zhang, Y. L.
Kang, and H. G. Suzuki. 2007. Journal of materials
processing technology. 184(1-3): 102–107.
SUPPLEMENTARY
READING LIST
Aochi, M., N. Fujii, and K. Yasuda. 2004. Study of the
basic welding characteristics of Mg alloy. Welding
international. 18(12): 944–949.
Aochi, M., N. Fujii, and K. Yasuda. 2004. Study of the
welding procedure for production of Mg alloy joints
for practical use. Welding international. 18(12):
950–955.
Atkins, G., M. Marya, D. L. Olson, and D. Eliezer.
2004. Magnesium-lithium alloy weldability: a microstructural characterization. In Magnesium technology. 2004, 37–41. Edited by A. A. Luo. Warrendale,
Pennsylvania: The Minerals, Metals & Materials
Society.
Ben-Artzy, A., A. Munitz, G. Kohn, B. Bronfin, and A.
Shtechman. 2002. Joining of light hybrid constructions made of magnesium and aluminum alloys. In
Magnesium technology. 2002, 295–302. Edited by
H. I. Kaplan. Warrendale, Pennsylvania: The Minerals, Metals & Materials Society.
Ben-Hamu, G., D. Eliezer, C. E. Cross, and T. Böllinghaus. 2007. The relation between microstructure and
corrosion behavior of GTA welded AZ31B magnesium sheet. Materials science and engineering, A.
452–453: 210–218.
Ben-Artzy, A., I. Makover, I. Dahan, M. Kupiec, Y.
Salah, A. Heler, A. Shtechman, A. Bussiba and Y.
Weinberg. 2002. Light magnesium constructions for
transportation applications. In High performance
materials for cost sensitive applications. 219–226.
Edited by F. H. Froes, E. Chen, R. R. Boyer, E. M.
Taleff, L. Lu, D. L. Zhang, C. M. Ward-Close, and
D. Eliezer. Warrendale, Pennsylvania: The Minerals,
Metals & Materials Society.
Chowdhury, S. M., D. L. Chen, S. D. Bhole, E. Powidajko, D. E. Weckman, and Y. Zhou. 2011. Micro-
AWS WELDING HANDBOOK
structure and mechanical properties of fiber-laserwelded and diode-laser-welded AZ31 magnesium
alloy. Metallurgical and materials transactions, A.
42(7): 1974–1989.
Cross, C. E., P. Xu, N. Winzer, and S. Bender. 2011.
Corrosion and corrosion-fatigue of AZ31 magnesium weldments. Welding in the world 55(7/8): 40–
47.
Emley, E. F. 1957. The metallurgical background to
magnesium alloy welding. British welding journal.
4(7): 307–321.
Emley, E. F. 1966. Welding and other methods of joining. In Principles of magnesium technology, 604–
640. Oxford: Pergamon Press.
Fenn, R. W., and L. F. Lockwood. 1960. Low-temperature properties of welded magnesium alloys. Welding
journal. 39(8): 352-s–356-s.
Juttner, S. 1998. Return of the light alloy brigade.
Welding and metal fabrication. 66(1): 11–15.
Kenyon, D. M. 1964. Arc behavior and its effect on the
tungsten arc welding of magnesium alloys. Journal of
institute of metals. 93: 85–89.
Koeplinger, R. D., and L. F. Lockwood. 1964. Gas
metal-arc spot welding of magnesium. Welding journal.
43(3): 195–201.
Kore, S., J. Imbert, M. J. Worswick, and Y. Zhou. 2009.
Electromagnetic impact welding of Mg to Al sheets.
Science and technology of welding and joining.
14(6): 549–553.
Lathabai, S., K. J. Baarton, D. Harris, P. G. Lloyd, D.
M. Viano, and A. McLean. 2003. Welding and
weldability of AZ31B by gas tungsten arc and laser
beam welding processes. In Magnesium technology.
2003, 157–162. Edited by H. I. Kaplan. Warrendale,
Pennsylvania: The Minerals, Metals & Materials
Society.
Liu, L., L. Xiao, J. C. Feng, Y. H. Tian, S. Q. Zhou, and
Y. Zhou. 2010. Resistance spot welded AZ31 magnesium alloys, part II: Effects of welding current on
microstructure and mechanical properties. Metallurgical and materials transactions, A. 41(10): 2642–
2650.
Liu, L., L. Xiao, J. C. Feng, Y. H. Tian, S. Q. Zhou, and
Y. Zhou. 2010. The mechanisms of resistance spot
welding of magnesium to steel. Metallurgical and
materials transactions, A. 41(10): 2651–2661.
Lockwood, L. F. 1963. Gas metal-arc welding of
AZ31B magnesium alloy sheet. Welding journal.
42(10): 807–818.
Lockwood, L. F. 1965. Automatic gas tungsten arc
welding of magnesium. Welding journal. 44(5): 213s–220-s.
Lockwood, L. F. 1967. Gas-shielded stud welding of
magnesium. Welding journal. 46(4): 168-s–174-s.
Lockwood, L. F. 1970. Pulse-arc welding of magnesium. Welding journal. 49(6): 464–475.
AWS WELDING HANDBOOK
Lockwood, L. F., and P. Klain. 1958. The arc welding of
wrought magnesium-thorium alloys. Welding journal. 37(6): 255-s–64-s.
Marya, M., G. R. Edwards, and D. L. Olson. 2004.
Theoretical models to describe properties of magnesium alloy fusion welds. In Joining of advanced and
specialty materials VI. 130–141. Edited by T. J. Lienert, V. Acoff, J. E. Indacochea, and J. N. DuPont.
Materials Park, Ohio: ASM International.
Portz, A. G., and G. R. Rothgery. 1963. Flash welded
magnesium rings meet space age needs. Welding
design and fabrication. 36(1): 44–45.
Powidajko, R. 2009. Weldability of AZ31B magnesium
sheet by laser welding processes. Master’s thesis,
University of Waterloo, Ontario, Canada. http://uwspace.uwaterloo.ca/bitstream/10012/4757/1/Powidajko_Elliot.pdf.
Stern, A., A. Munitz, and G. Kohn. 2003. Application
of welding technologies for joining of Mg alloys:
Microstructure and mechanical properties. Magnesium technology. 2003, 163–168. Edited by H. I.
Kaplan. Warrendale, Pennsylvania: The Minerals,
Metals & Materials Society.
BRAZING AND SOLDERING
Bobzin, K., E. Lugscheider, F. Ernst, D. Jäger, A. Schlegel, and J. Rösing. 2008. A look at the development
of magnesium-based filler metals. Welding journal.
87(3): 38–40.
Mücklich, S., G. Fritsche and B. Wielage. 2008. Amorphous filler metals offer great potential for joining
magnesium alloys. Welding journal. 87(3): 31–33.
ELECTRON BEAM WELDING
Chi, C. T., C. G. Chao, T. F. Liu, and C. C. Wang. 2008.
Optimal parameters for low and high voltage electron beam welding of AZ series magnesium alloys
and mechanism of weld shape and pore formation.
Science and technology of welding and joining.
13(2): 199–211.
Munitz, A., C. Cotler, H. Shaham, and G. Kohn. 2000.
Electron beam welding of magnesium AZ91D plates.
Welding journal. 79(7): 202-s–208-s.
Su, S. F., J. C. Huang, H. K. Lin, and N. J. Ho. 2002.
Electron-beam welding behavior in Mg-Al-based
alloys. Metallurgical and materials transactions, A.
33(5): 1461–1473.
FATIGUE STRENGTH
Kleinpeter, B., M. Rethmeier, H. Wohlfahrt, and K.
Dilger. 2003. Fatigue strength of welded wrought
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
211
magnesium alloys. In Magnesium: Proceedings of the
6th international conference—magnesium alloys and
their applications. 909–916. Edited by K. U. Kainer.
Weinheim, Germany: Wiley-VCH.
Sonsino, C.M., H. Hanselka, O. Karakas, A. Gulsoz,
M. Vogt, and K. Kilger. 2008. Fatigue design values
for welded joints of the wrought magnesium alloy
AZ31 according to the nominal, structural and notch
stress concepts in comparison to welded steel and
aluminium connections. Welding in the world. 52(5/6):
79–94.
Tsujikawa, M., H. Somekawa, K. Higashi, H. Iwasaki,
T. Hasegawa, and A. Mizuta. 2004. Fatigue of
welded magnesium alloy joints. Materials transactions. 45(2): 419–422.
FRICTION STIR WELDING
Campanelli, L.C., U. F. H. Suhuddin, A. I. S. Antonialli,
J. F. dos Santos, N. G. Alcantara, and C. Bolfarini.
2013. Metallurgy and mechanical performance of
AZ31 magnesium alloy friction spot welds. Journal
of materials processing technology. 213(4): 515–521.
Esparza, J. A., W. C. Davis, and L. E. Murr. 2003.
Microstructure-property studies in friction-stir
welded, thixomolded magnesium alloy AM60. Journal of materials science. 38: 941–952.
Gerlich, A., P. Su, and T. H. North. 2005. Peak temperatures and microstructures in aluminium and magnesium alloy friction stir spot welds. Science and
technology of welding and joining. 10(6): 647–652.
Su, P., A. Gerlich, M. Yamamoto, and T. H. North.
2007. Formation and retention of local melted films
in AZ91 friction spot welds. Journal of materials science. 42: 9954–9965.
Sun, N., Y. H. Yin., A. Gerlich, and T.H. North. 2007.
Mechanism of cracking in AZ91 friction stir spot
welds. Science and technology of welding and joining.
14(8): 747–752.
Wang. D., J. Shen, and L. Wang. 2011. Effects of the
types of overlap on the mechanical properties of
FSSW welded AZ series magnesium alloy joints.
International journal of minerals metallurgy and
materials. 19(3): 231–235.
Yamamoto, M., A. Gerlich, T. H. North, and K. Shinozaki. 2007. Cracking in the stir zones of Mg-alloy
friction stir spot welds. Journal of materials science.
42: 7657–7666.
Yamamoto, M., A. Gerlich, T. H. North, and K. Shinozaki. 2007. Mechanism of cracking in AZ91 friction stir spot welds. Science and technology of
welding and joining. 12(3): 208–216.
Yang, Y. K., H. Dong, H. Cao, Y. A. Chang, and S.
Kou. 2008. Liquation of Mg Alloys in Friction Stir
Spot Welding. Welding journal. 87(7): 167-s–177-s.
212
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
Yuan, W., R. S. Mishra, B. Carlson, R. Verma, and R.K.
Mishra. 2012. Materials flow and microstructural
evolution during friction stir spot welding of AZ31
magnesium alloy. Materials science and engineering,
A. 543: 200–209.
GAS METAL ARC WELDING
Fujie, M., K. Nakata, H. Tong, and M. Ushio. 2003.
MIG arc welding of magnesium alloy. Transactions
of the joining and welding research institute. 32(1):
39–40.
Michailav, V., M. Stadtaus, K. Dilger, and M. Rethmeier. 2005. Numerical MIG-welding simulation of
magnesium alloys. Mathematical modeling of weld
phenomena. 7, 77–89. Edited by H. Cerjak, H. K. D.
H. Bhadeshia, and E. Kozeschnik. Leeds, UK: Maney
Publishing.
Rethmeier, M., S. Wiesner, and H. Wohlfahrt. 2000.
Influences of the static and dynamic strength of
MIG-welded magnesium alloys. Magnesium alloys
and their applications. 200–204. Edited by K. U.
Kainer. Weinheim, Germany: Wiley-VCH.
Wohlfahrt, H., M. Rethmeier, B. Bouaifi, and M.
Schutz. 2003. Metal-inert gas welding of magnesium
alloys. Welding and cutting. 55(2): 80–84.
AWS WELDING HANDBOOK
AZ31 magnesium alloy plates. Welding international. 21(2): 103–109.
Stern, A., and A. Munitz. 1999. Partially melted zone
microstructural characterization from gas tungstenarc bead on plate welds of magnesium AZ91 alloy.
Journal of materials science letters. 18: 853–855.
Sun, D. Q., D. X. Sun, S. Q. Yin, and J. B. Li. 2006.
Microstructure and mechanical properties of tungsten inert gas welded magnesium alloy AZ91D
joints. ISIJ international. 46(8): 1200–1204. https://
www.jstage.jst.go.jp/article/isijinternational/46/8/
46_8_1200/_pdf.
Sun, Z., D. Pan, and J. Wei. 2002. Comparative evaluation of tungsten inert gas and laser welding of AZ31
magnesium alloy. Science and technology of welding
and joining. 7(6): 343–351.
Zhang, Z. D., L. M. Liu, Y. Shen, and L. Wang. 2005.
Welding of magnesium alloys with activating flux.
Science and technology of welding and joining.
10(6): 737–743.
Zhu, T., Z. W. Chen, and W. Gao. 2006. Incipient melting in partially melted zone during arc welding of
AZ91D magnesium alloy. Materials science and engineering, A. 416: 246–252.
Zhu, T., Z. W. Chen, and W. Gao. 2008. Microstructure formation in partially melted zone during gas
tungsten arc welding of AZ91Mg cast alloy. Materials characterization. 59(11): 1550–1558.
GAS TUNGSTEN ARC WELDING
Liang, G., and S. Yuan. 2008. Study on the temperature
measurement of AZ31B magnesium alloy in gas
tungsten arc welding. Materials letters. 62(15):
2282–2284.
Liu, L., and C. Dong. 2006. Gas tungsten-arc filler
welding of AZ31 magnesium alloy. Materials letters.
60(17–18): 2194–2197.
Liu, L. M., D. H. Cai, and Z. D. Zhang. 2007. Gas
tungsten arc welding of magnesium alloy using activated flux-coated wire. Scripta materialia. 57(8):
695–698.
Liu, L. M., Z. D. Zhang, G. Song, and L. Wang. 2007.
Mechanism and microstructure of oxide fluxes for
gas tungsten arc welding of magnesium alloy. Metallurgical and materials transactions, A. 38(3): 649–
658.
Marya, M., G. R. Edwards, and S. Liu. 2004. An investigation on the effects of gases in GTA welding of a
wrought AZ80 magnesium alloy. Welding journal.
83(7): 203-s–212-s.
Munitz, A., C. Cotler, A. Stern, and G. Kohn. 2001.
Mechanical properties and microstructure of gas
tungsten arc welded magnesium AZ91D plates.
Materials science and engineering, A. 302(1): 68–73.
Ninomiya, M., M. Sugamata, and J. Kaneko. 2007.
Mechanical properties of TIG welded joints on heavy
LASER BEAM WELDING
Asahina, T. 2005. Pulsed YAG laser weldability of magnesium alloys. Welding international. 19(1): 23–28.
Cao, X., M. Jahazi, J. P. Immarigeon, and W. Wallace.
2006. A review of laser welding techniques for magnesium alloys. Journal of materials processing technology. 171(2): 188–204.
Gao, M., X. Y. Zeng, B. Tan, and J. C. Feng. 2009.
Study of laser MIG hybrid welded AZ31 magnesium
alloy. Science and technology of welding and joining.
14(4): 274–281.
Liu, L. M., G. Song, and M. L. Zhu. 2008. Low-power
laser/arc hybrid welding behavior in AZ-based Mg
alloys. Metallurgical and materials transactions, A.
39(7): 1702–1711.
Liu, L. M., G. Song, and M. S. Chi. 2005. Laser-tungsten inert gas hybrid welding of dissimilar AZ based
magnesium alloys. Materials science technology.
21(9): 1078–1082.
Liu, L., G. Song, G. Liang, and J. Wang. 2005. Pore formation during hybrid laser-tungsten inert gas arc
welding of magnesium alloy AZ31B—Mechanism
and remedy. Materials science and engineering, A.
390: 76–80.
AWS WELDING HANDBOOK
Liu, L., J. Wang, and G. Song. 2004. Hybrid laser-TIG
welding, laser beam welding and gas tungsten arc
welding AZ31B magnesium alloy. Materials science
and engineering, A. 381(1–2): 129–133.
Marya, M., and G. R. Edwards. 2001. Factors controlling the magnesium weld morphology in deep penetration welding by a CO2 laser. Journal of materials
engineering and performance. 10(4): 435–443.
Pan, L. K., C. C. Wang, Y. C. Hsiao, and K. C. Ho.
2004. Optimization of Nd:YAG laser welding onto
magnesium alloy via Taguchi analysis. Optics and
laser technology. 37(1): 33-42.
Quan, Y. J., Z. H. Chen, X. S. Gong, and Z. H. Yu.
2008. Effects of heat input on microstructure and
tensile properties of laser welded magnesium alloy
AZ31. Materials characterization. 59: 1491–1497.
Quan, Y., Z. Chen, X. Gong, and Z. Yu. 2008. CO2
laser beam welding of dissimilar magnesium-based
alloys. Materials science and engineering, A. 496(1-2):
45–51.
Quan, Y., Z. Chen, Z. Yu, X. Gong, and M. Li. 2008.
Characteristics of laser welded wrought Mg-Al-Mn
alloy. Materials characterization. 59: 1799–1804.
Weisheit, A., R. Galun, and B. L. Mordike. 1998. CO2
laser beam welding of magnesium-based alloys.
Welding journal. 77(4): 149-s–154-s.
Yu, L., K. Nakata, N. Yamamoto, and J. Liao. 2009.
Texture and its effect on mechanical properties in
fiber laser weld of a fine-grained Mg alloy. Materials
letters. 63(11): 870–872.
Zhao, H., and T. DebRoy. 2001. Pore formation during
laser beam welding of die-cast magnesium alloy
AM60B—Mechanism and remedy. Welding journal.
80(8): 204-s–210-s.
Zhu, J., L. Li, and Z. Liu. 2005. CO2 and diode laser
welding of AZ31 magnesium alloy. Applied surface
science. 247: 300–306.
RESISTANCE WELDING
Babu, N. K., S. Brauser, M. Rethmeier, and C. E. Cross.
2012. Characterization of Microstructure and Deformation Behavior of Resistance Spot Welded AZ31
Magnesium Alloy. Materials Science & Engineering,
A. 549: 149–156.
Feng, J. C., Y. R. Wang, and Z. D. Zhang. 2006.
Nugget growth characteristic for AZ31B magnesium
CHAPTER 2—MAGNESIUM AND MAGNESIUM ALLOYS
213
alloy during resistance spot welding. Science and
technology of welding and joining. 11(2): 154–162.
Gould, J. E., and W. Chuko. 2006. Investigating resistance and friction stir welding processes for joining
magnesium. Welding journal. 85(3): 46–53.
Lang, B., D. Q. Sun, G. Z. Li, and X. F. Qin. 2008.
Effects of welding parameters on microstructure and
mechanical properties of resistance spot welded magnesium alloy joints. Science and technology of welding and joining. 13(8): 698–704.
Lang, B., D. Q. Sun, Z. Z. Xuan, and X. F. Qin. 2008.
Hot cracking of resistance spot welded magnesium
alloy. ISIJ international. 48(1): 77–82.
Liu, L., S. Q. Zhou, Y. H. Tian, J. C. Feng, J. P. Jung,
and Y. N. Zhou. 2009. Effects of surface conditions
on resistance spot welding of Mg alloy AZ31. Science and technology of welding and joining. 14(4):
356–361.
Munitz, A., G. Kohn, and C. Cotler. 2002. Resistance
spot welding of Mg-AM50 and Mg-AZ91D alloys.
In Magnesium technology. 303–307. Edited by H. I.
Kaplan. Warrendale, Pennsylvania: The Minerals,
Metals & Materials Society.
Sun, D. Q., B. Lang, D. X. Sun, and J. B. Li. 2007.
Microstructures and mechanical properties of resistance spot welded magnesium alloy joints. Materials
science engineering, A. 460–461: 494–498.
Vaidya, W. V., M. Horstmann, E. Seib, K. Toksoy, and
M. Kocak. 2006. Assessment of fracture and fatigue
crack propagation of laser beam and friction stir
welded aluminum and magnesium alloys. Advanced
engineering materials. 8(5): 399–406.
Wang, Y. R., J. C. Feng, and Z. D. Zhang. 2006. Microstructure characteristics of resistance spot welds of
AZ31 Mg alloy. Science and technology of welding
and joining. 11(5): 555–560.
Wang, Y. R., Z. H. Mo, J. C. Feng, and Z. D. Zhang.
2007. Effect of welding time on microstructure and
tensile shear load in resistance spot welded joints of
AZ31 alloy. Science and technology of welding and
joining. 12(8): 671–676.
Zhang, Z. D., Y. R. Wang, and D. Q. Li. 2007. Expulsion in resistance spot welding of AZ31B magnesium
alloy. Materials science forum. 546–549: 443–446.
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215
AWS WELDING HANDBOOK
CHAPTER
C H A P T E3 R
9
COPPER AND
COPPER ALLOYS
Prepared by the
Welding Handbook
Chapter Committee
on Copper and Copper
Alloys:
K. W. Lachenberg, Co-Chair
Sciaky Inc.
G. R. LaFlamme, Co-Chair
PTR-Precision
Technologies Inc.
D. D. Kautz
Los Alamos National
Laboratory
Welding Handbook
Volume 5 Committee
Member:
J. H. Myers
Weld Inspection and
Consulting Services, Inc.
Contents
Photographs courtesy of SLAC National Accelerator Laboratory, United States Department of Energy
Components of the Linear Accelerator after Electron Beam Welding
Introduction
216
Copper Alloys
217
High-Copper Alloys
221
Welding and
Joining Processes
225
Filler Metals
229
Joint Designs for
Copper Welds
233
Welding Conditions
233
Brazing
253
Soldering
260
Applications
263
Safe Practices
271
Bibliography
272
Supplementary
Reading List
272
216
AWS WELDING HANDBOOK
CHAPTER 3
COPPER AND
COPPER ALLOYS
INTRODUCTION
Among the highly valued properties of copper and
copper alloys are excellent electrical and thermal conductivity, corrosion resistance, metal-to-metal wear
resistance, and a distinctive aesthetic appearance. Copper and copper alloys are important to many industries,
including automotive, communications, electrical and
electronics, refrigeration, transportation, and highenergy physics, and also to the manufacturers of numerous consumer products. Copper is a favored material
used in artistic and architectural applications.
Corrosion resistance, high electrical conductivity,
and low maintenance are especially important when
copper is used in electrical connections. These properties contribute to the most significant use of copper: the
manufacturing of electrical equipment.
Copper is the electrical conductivity standard of the
engineering world, with the rating of 100%, as determined by the International Annealed Copper Standard
(IACS), which was developed by the International Electrotechnical Commission and published in 1913.1 The
electrical conductivity of all materials is compared to
the IACS standard. Some specially processed copper
forms can reach an IACS rating of 103%, which is very
close to the theoretical limit for pure copper.
Copper and many copper alloys have a face-centered
cubic crystal structure, which accounts for the characteristics of good formability and malleability. In pure
form, copper has a density of 8.94 Mg/m3 (milligrams
per cubic meter) (0.32 lb/in.3 [pounds per cubic inch]),
1. At the time this chapter was prepared, referenced codes and other
standards were valid. If a code or other standard is cited without a
date of publication, it is understood that the latest edition of the referenced document applies. If a code or other standard is cited with the
date of publication, the citation refers to that edition only, and it is
understood that any future revisions or amendments to the code are
not included; however, as codes and standards undergo frequent revision, the reader should consult the most recent edition.
about three times that of aluminum. The electrical and
thermal conductivity of copper is slightly lower than
that of silver, but about 1.5 times higher than that of
aluminum.
Copper is resistant to oxidation, water, salt water,
alkaline solutions, and many organic chemicals. Characteristically good corrosion resistance makes copper
alloys ideally suited for water tubing, valves, fittings,
heat exchangers, chemical processing equipment, and
bearings. Copper reacts with sulfur and ammonia compounds; ammonium hydroxide solutions rapidly attack
copper and copper alloys.
The pleasant color, relatively good strength, and
good formability of copper and copper alloys make
them highly favored for architectural applications, such
as roofing and decorative accents. The naturally occurring, greenish, weathered corrosion product—called
patina or verdigris—is often used as a decorative feature. When joining these materials, the patina must be
removed and reapplied after the operation.
Copper and most copper alloys can be joined by
welding, brazing, and soldering.2 The major classes of
copper alloys, the metallurgy and processing of copper,
and how alloying elements affect the joining characteristics of welding, brazing, and soldering are described in
this chapter.
2. Definitions of welding processes and standard welding terms used
in this chapter are from American Welding Society (AWS) Committee
on Definitions and Symbols, 2010, Standard Welding Terms and Definitions, Including Terms for Adhesive Bonding, Brazing, Soldering,
Thermal Cutting and Thermal Spraying, AWS A3.0:2010, Miami:
American Welding Society.
AWS WELDING HANDBOOK
COPPER ALLOYS
Copper easily alloys with many other elements, creating materials with wide-ranging properties and applications. The development and use of some of these
alloy systems date back thousands of years; other alloy
systems have been used only in recent times as the role
of metallurgy has become prominent and metal processing methods have improved.
METALLURGY
Many common metals are alloyed with copper,
mostly within the limits of solid-solution solubility. The
principal alloying elements in copper alloys are aluminum, nickel, silicon, tin, and zinc. Small quantities of
other elements are also added to improve mechanical
properties, corrosion resistance, or machinability to
make them responsive to strengthening heat treatments,
or to deoxidize the alloy.
CLASSIFICATION
Copper and copper alloys are classified into nine
major groups:
1. Copper, with a minimum of 99.3% copper
content;
2. High-copper alloys, with up to 5% of an
alloying element;
3. Copper-zinc alloys (brass);
4. Copper-tin alloys (phosphor bronze);
5. Copper-aluminum alloys (aluminum bronze);
6. Copper-silicon alloys (silicon bronze);
7. Copper-nickel alloys;
8. Copper-nickel-zinc alloys (nickel silvers); and
9. Special alloys.
These alloys are further divided into wrought and
cast categories, as shown in Table 3.1.
The Unified Numbering System (UNS) designates
individual alloys with a letter and a five-digit number.
Copper alloys designated UNS C1XXXX through
C7XXXX are wrought alloys, and C8XXXX through
C9XXXX are cast alloys. Therefore, an alloy manufactured in both a wrought form and cast form can have
two numbers, depending on the method of manufacture. Copper and copper alloys have common names
such as oxygen-free copper, beryllium copper, Muntz
metal, phosphor bronze, and low-fuming bronze. These
common names or trade names are being replaced by
CHAPTER 3—COPPER AND COPPER ALLOYS
217
UNS numbers to provide a common nomenclature for
international usage.
The physical properties of copper alloys that are
important to welding, brazing, and soldering include
the range of melting temperature, coefficient of thermal
expansion, and electrical and thermal conductivity. The
physical properties of some of the most widely used
copper alloys are listed in Table 3.2. This data shows
that when alloying elements are added to copper, the
electrical conductivity and thermal conductivity decrease
drastically. The electrical and thermal conductivity of
an alloy are significant to determining the welding procedures to be used for the alloy.
Small additions of some elements (e.g., iron, silicon,
tin, arsenic, and antimony) improve the corrosion and
erosion resistance of copper alloys. Lead, bismuth, selenium, and tellurium are added to copper alloys to
improve machinability.
Boron, phosphorus, silicon, and lithium are added to
copper as deoxidizers during the melting stage and
refining stage of manufacture. Additions of silver and
cadmium increase the softening temperature of copper.
Additions of cadmium, cobalt, zirconium, chromium,
and beryllium form precipitation-hardening alloys that
increase the strength of copper.
Many commercial copper alloys are described as
single-phase solid solution. Some copper alloys have
two or more microstructural phases. These alloys can
be hardened by precipitation of intermetallic compounds or by quenching at a temperature higher than
the critical transformation temperature, which results in
a martensitic transformation.
In general, solid-solution copper alloys are easily
cold worked, although the force required for cold
working and the rate of work hardening increase as
alloy content increases. Two-phase alloys harden more
rapidly during cold working, but usually have better
hot-working characteristics than the solid-solution metals
of the same alloy system. Ductility decreases and yield
strength increases as the proportion of the second phase
increases.
MAJOR ALLOYING ELEMENTS
The addition of specific elements to an alloy system
is determined by the properties desired in the finished
alloy material. The properties of the metals that can be
produced as a result of alloying additions are presented
in this section.
Aluminum
The copper-aluminum alloys may contain up to 15%
aluminum and may also have additions of iron, nickel,
218
CHAPTER 3—COPPER AND COPPER ALLOYS
AWS WELDING HANDBOOK
Table 3.1
Classification of Copper and Copper Alloys
Category
Description
Range of UNS Numbersa
Wrought Alloysb
Copper
High-copper alloys
Brasses
Leaded brasses
Tin brasses
Phosphor bronzes
Leaded phosphor bronzes
Aluminum bronzes
Silicon bronzes
Miscellaneous brasses
Copper nickels
Nickel silvers
Copper—99.3% minimum
Copper—96% to 99.%
Copper-zinc alloys
Copper-zinc-lead alloys
Copper-zinc-tin alloys
Copper-tin alloys
Copper-tin-lead alloys
Copper-aluminum alloys
Copper-silicon alloys
Copper-zinc alloys
Nickel—3% to 30%
Copper-nickel-zinc alloys
C10100–C15760
C16200–C19750
C20500–C28580
C31200–C38590
C40400–C49080
C50100–C52400
C53200–C54800
C60600–C64400
C64700–C66100
C66400–C69950
C70100–C72950
C73150–C79900
Cast Alloysc
Coppers
High-copper alloys
Red brasses
Semi-red brasses
Yellow brasses
Manganese bronzes
Silicon bronzes and silicon brasses
Tin bronzes
Leaded tin bronzes
Nickel-tin bronzes
Aluminum bronzes
Copper nickels
Nickel silvers
Leaded coppers
Special alloys
Copper—99.3% minimum
Copper—94% to 99.2%
Copper-tin-zinc and copper-tin-zinc-lead alloys
Copper-tin-zinc and copper-tin-zinc-lead alloys
Copper-tin-zinc and copper-tin-zinc-lead alloys
Copper-zinc-iron alloys
Copper-zinc-silicon alloys
Copper-tin alloys
Copper-tin-lead alloys
Copper-tin-nickel alloys
Copper-aluminum-iron and copper-aluminum-iron-nickel alloys
Copper-nickel-iron alloys
Copper-nickel-zinc alloys
Copper-lead alloys
—
C80100–C81200
C81300–C82800
C83300–C83810
C84200–C84800
C85200–C85800
C86100–C86800
C87300–C87900
C90200–C91700
C92200–C94500
C94700–C94900
C95200–C95900
C96200–C96900
C97300–C97800
C98200–C98840
C99300–C99750
a. Refer to ASTM DS56K, Metals and Alloys in the Unified Numbering System (UNS): 12th Ed., 2012, ISBN-13: 978-0-7680-7950-0, ASTM International,
West Conshohocken, Pennsylvania, and SAE International, Warrendale, Pennsylvania.
b. For composition and properties, refer to Standards Handbook, Part 2—Alloy Data, Wrought Copper and Copper Alloy Mill Products, 8th Ed., New York:
Copper Development Association, Inc., 1985.
c. For composition and properties, refer to Standards Handbook, Part 7—Data/Specifications, Cast Copper and Copper Alloy Products, New York: Copper
Development Association, Inc., 1970.
tin, and manganese. The solubility of aluminum in
copper is 7.8%, although this will be slightly increased
with the usual addition of iron. Alloys with less than
8% aluminum are single-phase, with or without additions of iron. When the aluminum content is between
9% and 15%, the system is two-phase and capable of
either a martensitic or a eutectoid transformation.
Increased amounts of aluminum result in greater tensile
strength, yield strength, and hardness of the alloy, but
ductility is reduced. Aluminum forms a refractory oxide
that must be removed before or during welding, brazing,
or soldering.
Arsenic
Arsenic is added to copper alloys to inhibit dezincification corrosion of copper-zinc alloys that are to be
used for service in water. The addition of arsenic to
copper alloys does not cause welding problems, unless
the alloy also contains nickel.
AWS WELDING HANDBOOK
CHAPTER 3—COPPER AND COPPER ALLOYS
219
Table 3.2
Physical Properties of Typical Wrought Copper Alloys
Melting Range
Coefficient of Thermal
Expansion at 20°C–300°C
(68°F–572°F)
Thermal Conductivity
at 20°C (68°F)
Electrical
Conductivity,
% IACS
Alloy
UNS No.
°C
°F
μm/(m·K)
μin./(in.°F)
W/(m·K)
Btu/(ft·h·°F)
Oxygen-free copper
C10200
1066–1088
1948–1991
17.6
9.8
370
214
101
Beryllium copper
C17200
866–982
1590–1800
17.8
9.9
107–130
62–75
22
Commercial bronze
C22000
1021–1043
1870–1910
18.4
10.2
188
109
44
Red brass
C23000
988–1027
1810–1880
18.7
10.4
159
92
37
Cartridge brass
C26000
916–955
1680–1750
20.0
11.1
121
70
28
Phosphor bronze
C51000
955–1049
1750–1920
17.8
9.9
69
40
15
Phosphor bronze
C52400
843–999
1550–1830
18.4
10.2
50
29
11
Aluminum bronze
C61400
1041–1046
1905–1915
16.2
9.0
67
39
14
High-silicon bronze
C65500
971–1027
1780–1880
18.0
10.0
36
21
7
24
Manganese bronze
C67500
866–888
1590–1630
21.2
11.8
105
61
Copper nickel, 10%
C70600
1099–1149
2010–2100
17.1
9.5
38
22
9
Copper nickel, 30%
C71500
1171–1238
2140–2260
16.2
9.0
29
17
4.6
Nickel silver, 65%-15%
C75200
1071–1110
1960–2030
16.2
9.0
33
19
6
Beryllium
The solubility of beryllium in copper is approximately 2% at 870°C (1600°F) and only 0.3% at room
temperature; therefore, beryllium easily forms a supersaturated solution with copper that will precipitate during an age-hardening treatment. Alloys with higher
beryllium content are more easily welded because the
increased beryllium content results in decreased thermal
conductivity and a lower melting point. Beryllium
forms a refractory oxide that must be removed before
welding, brazing, or soldering. Because of the toxic
effects of beryllium-containing fumes, an industrial
hygienist should be consulted before processing these
alloys. (Refer to the Safe Practices section of this chapter.)
Boron
Boron strengthens and deoxidizes copper. Borondeoxidized copper is weldable with matching filler
metals, and other coppers are weldable with boroncontaining filler metals.
Cadmium
The solubility of cadmium in copper is approximately 0.5% at room temperature. The presence of cadmium in copper up to 1.25% does not cause serious
difficulty in fusion welding because it easily evaporates
from copper at the welding temperature. A small
amount of cadmium oxide can form in the weld pool,
but it can be fluxed without difficulty. The cadmiumcopper welding rod is the Class 1 alloy, classified by the
Resistance Welding Manufacturing Alliance (RWMA), a
standing committee of the American Welding Society.3
The small amount of cadmium strengthens pure copper
while maintaining very high conductivity. This combination of properties makes this material ideal for
electrodes used for the resistance welding of highconductivity alloys, such as aluminum. Cadmiumalloyed copper has been largely replaced by an overaged
chromium copper because of federal restrictions regarding the use of heavy metals in manufacturing.
Chromium
The solubility of chromium in copper is approximately 0.55% at 1038°C (1900°F) and less than 0.05%
at room temperature. The phase that forms during age
hardening is almost pure chromium. Chromium coppers can develop a combination of high strength and
good conductivity. Like aluminum and beryllium, chromium can form a refractory oxide on the surface of the
weld pool, so an arc welding process that provides a
3. Resistance Welding Manufacturing Alliance (RWMA), 2003,
Resistance Welding Manual, 4th ed. Miami: Resistance Welding
Manufacturing Alliance. Section 13.4.
220
CHAPTER 3—COPPER AND COPPER ALLOYS
protective atmosphere over the weld pool should be
used. Oxyfuel gas welding is difficult unless special
fluxes are used.
Iron
The solubility of iron in copper is approximately 3%
at 1038°C (1900°F) and less than 0.1% at room temperature. Iron is added to aluminum bronze, manganese
bronze, and copper-nickel alloys to increase strength by
solid-solution and precipitation hardening. Iron
increases resistance to erosion and corrosion of coppernickel alloys. Iron must be kept in solid solution or in
an intermetallic form to obtain the desired corrosion
resistance, particularly in copper-nickel alloys. Iron also
acts as a grain refiner. Iron has little effect on
weldability when used within the specification limits of
commercial alloys.
Lead
Lead is added to copper alloys to improve machinability or to improve bearing properties and pressure
tightness of some cast copper alloys. Lead does not
form a solid solution with copper and is almost completely insoluble (0.06%) in copper at room temperature. Lead is present as pure, discrete particles in these
alloys, which provides the lubricity for machining properties. During solidification, the lead remains liquid at
330°C (620°F). The extreme temperature differential
between the two phases that occurs in leaded copper
alloys makes them hot-short and susceptible to cracking
during fusion welding. Lead is the most detrimental element with respect to the weldability of copper alloys.
Manganese
Manganese is highly soluble in copper. It is used in
proportions of 0.05% to 3.0% in manganese bronze,
deoxidized copper, and copper-silicon alloys. Manganese
additions at levels contained in commercial alloys are
not detrimental to the weldability of copper alloys.
Manganese improves the hot-working characteristics of
multiple-phase copper alloys.
Nickel
Copper and nickel are completely solid soluble in all
proportions. Although copper-nickel alloys are readily
welded, residual elements can lead to embrittlement
and hot cracking. A welding filler metal with a sufficient deoxidizer or desulfurizer should be used when
welding copper nickel so that a residual amount
remains in the solidified weld metal. Manganese is the
most common alloying addition used for this purpose.
AWS WELDING HANDBOOK
Phosphorus
Phosphorus is used as a strengthener and deoxidizer
in certain coppers and copper alloys. Phosphorus is soluble in copper up to 1.7% at the eutectic temperature
of 649°C (1200°F), and approximately 0.4% at room
temperature. When added to copper-zinc alloys, phosphorus inhibits dezincification. The amount of phosphorus that is present in commercially available copper
alloys has no effect on weldability.
Silicon
The solubility of silicon in copper is 5.3% at 816°C
(1500°F) and 3.6% at room temperature. Silicon is
used both as a deoxidizer and as an alloying element to
improve strength, malleability, and ductility. Coppersilicon alloys have good weldability, but are hot-short
at elevated temperatures. Fast cooling should be used
through this hot-short temperature range to prevent
cracking.
Silicon oxide forms on copper-silicon alloys at temperatures as low as 204°C (400°F). This oxide will
interfere with brazing and soldering operations unless a
suitable flux is applied prior to heating.
Tin
The solubility of tin in copper increases rapidly at
high temperatures. At 788°C (1450°F), the solubility of
tin is 13.5%; at room temperature and equilibrium conditions, it is less than 1%. Alloys containing less than
2% tin can be single-phase when cooled rapidly.
Copper-tin alloys tend to be hot-short, which causes
cracking during fusion welding. Tin oxidizes when
exposed to the atmosphere, and this oxide can reduce
weld strength if trapped within the weld metal.
Zinc
Zinc is the most important alloying element in commercially available copper. Zinc is soluble in copper up
to 32.5% at 927°C (1700°F) and 37% at room temperature. A characteristic of all copper-zinc alloys is the
relative ease with which zinc volatilizes from the molten
metal with very slight superheat.
Zinc is also a residual element in aluminum bronze
and copper nickel and can cause porosity or cracking,
or both.
MINOR ALLOYING ELEMENTS
Calcium, magnesium, lithium, sodium, or combinations of these elements are added to copper alloys as
deoxidizers. Very small amounts of these oxidizing ele-
AWS WELDING HANDBOOK
ments may remain in copper alloys after mill processing, but this is seldom a factor in welding.
Antimony, arsenic, phosphorus, bismuth, selenium,
sulfur, and tellurium can cause hot cracking when
alloyed in single-phase aluminum bronze and in coppernickel alloys. The small amount of antimony added to
brasses has little influence on weldability.
Carbon is practically insoluble in copper alloys
unless large amounts of iron, manganese, or other
strong formers of carbide are present. Carbon embrittles copper alloys by precipitating in the grain boundaries as graphite or as a mixed carbide.
EFFECTS OF ALLOYING ELEMENTS ON
JOINING
The weldability of copper and certain high-copper
alloys is significantly affected by high electrical and
high thermal conductivity. Welding heat is rapidly conducted into the base metal and can cause incomplete
fusion in the weldment. Preheating copper alloys will
reduce the welding heat input requirements needed for
good fusion.
Copper alloys are often hardened by mechanical cold
working, and any application of heat tends to soften
these metals. When welded, the heat-affected zone
(HAZ) of the weldment will be softer and weaker than
the adjacent base metal. Hot cracking in the HAZ tends
to occur in metal that has been severely cold-worked.
In practice, there is a time-temperature reaction; therefore, using a minimum preheat and controlling the
interpass temperature can keep softening of the HAZ to
a minimum.
Precipitation hardening in copper alloys is obtained
when copper is alloyed with beryllium, chromium,
boron, nickel-silicon, and zirconium. For optimum
results, components to be precipitation hardened
should be welded in the annealed condition, followed
by the precipitation-hardening heat treatment. Welding,
brazing, or soldering precipitation-hardened alloys can
reduce the mechanical properties of copper alloys due
to overaging.
Copper alloys that have wide liquidus-to-solidus
temperature ranges, such as copper tin and copper
nickel, are susceptible to hot cracking. Because the lowmelting interdendritic liquid solidifies at a lower temperature than the bulk dendrite, shrinkage stresses can
produce interdendritic separation during solidification.
Hot cracking can be minimized by implementing the
following procedures:
1. Reducing restraint during welding,
2. Minimizing heat input and interpass
temperature, and
CHAPTER 3—COPPER AND COPPER ALLOYS
221
3. Reducing the size of the root opening
and increasing the size of the root pass.
Certain elements, such as zinc, cadmium, and phosphorus, have low boiling points. Vaporization of these
elements during welding can result in porosity. Porosity
can be minimized by increasing travel speed and using
filler metal with low percentages of these volatile elements.
Surface oxides on aluminum bronze, beryllium copper, chromium copper, and silicon bronze are difficult
to remove and can present problems when welding,
brazing, or soldering. Surfaces to be joined must be
clean, and special fluxing or shielding methods must be
used to prevent surface oxides from reforming during
the joining operation.
HIGH-COPPER ALLOYS
The purest forms of copper alloys are classified as
pure copper, which contains a minimum of 99.3% copper, and high-copper alloys, which contain up to 5% of
an alloying element. These alloys are usually specified
for applications that require high electrical and thermal
conductivity.
Oxygen-Free Copper
Oxygen-free coppers (UNS C10100–C10800) contain a maximum of 10 ppm oxygen and a minimum
total of 0.01% of other elements. Oxygen-free copper is
produced by melting and casting under a reducing
atmosphere that prevents oxygen contamination. No
deoxidizing agent is introduced in production of this
type of copper, but oxygen can be absorbed from the
atmosphere during heating at high temperatures.
Absorbed oxygen can cause problems during subsequent welding or brazing of the copper.
Oxygen-free copper has mechanical properties similar to those of oxygen-bearing copper, but the microstructure is more uniform. Oxygen-free copper has
excellent ductility and is readily joined by welding,
brazing, and soldering.
Silver can be added to oxygen-free copper to increase
the strength at elevated temperatures without changing
the electrical conductivity. The addition of silver prevents appreciable softening of cold-worked copper during short-term exposure to elevated temperature; silver
also increases the allowable creep stress or provides
resistance to creep rupture over long time periods. The
silver addition does not affect the joining characteristics.
222
CHAPTER 3—COPPER AND COPPER ALLOYS
Oxygen-Bearing Copper
Oxygen-bearing coppers include the electrolytic
tough-pitch grades (UNS C11000–C11900) and firerefined grades (UNS C12500–C13000).
Fire-refined coppers contain varying amounts of
impurities, including antimony, arsenic, bismuth, and
lead. Electrolytic tough-pitch coppers contain minimal
impurities and have more uniform mechanical properties. The residual oxygen content of electrolytic toughpitch copper and fire-refined copper is about the same.
Impurities and residual oxygen can cause porosity and
other discontinuities when these coppers are welded or
brazed.
A copper-cuprous oxide eutectic is distributed as
globules throughout wrought forms of oxygen-bearing
copper. Although this condition does not affect
mechanical properties or electrical and thermal conductivity, it makes the copper susceptible to embrittlement
when heated in the presence of hydrogen. Hydrogen
diffuses rapidly into the hot metal, reduces the oxides,
and forms steam at the grain boundaries. The metal will
rupture when stressed.
When oxygen-bearing coppers are heated to high
temperatures, the copper oxide tends to concentrate in
the grain boundaries, causing major reductions in
strength and ductility. Fusion welding of oxygen-bearing copper is not recommended for structural applications. Embrittlement is less severe when a rapid, solidstate welding process is used, such as friction welding.
Oxygen-bearing copper can be joined by silver brazing
and soft soldering when the appropriate procedures are
used.
AWS WELDING HANDBOOK
welding is not recommended for free-machining coppers because these alloys are hot-short and very susceptible to cracking. Free-machining coppers can be joined
by brazing and soldering.
Precipitation-Hardenable Copper Alloys
The precipitation-hardenable copper alloys include
UNS C15000, C15100, C17000–C18400, and
C64700–C64730. Small amounts of beryllium, chromium, or zirconium can be added to copper to form
alloys that respond to precipitation-hardening heat
treatment to increase mechanical properties. These copper alloys are solution annealed (to a soft condition
about Rockwell Hardness 50 (HRB 50) by heating to
an elevated temperature that puts the alloying elements
into solution. Rapid cooling by water quenching keeps
the alloying elements in solid solution. The workpieces
are then aged at temperatures of 316°C to 482°C
(600°F to 900°F). During aging, a second phase precipitates within the matrix that inhibits plastic deformation, resulting in greatly enhanced mechanical
properties. The solution-annealed alloy can be cold
worked prior to aging to achieve higher strength.
Exposing precipitation-hardened alloys to welding or
brazing temperatures will overage the exposed area.
Overaging softens the alloys by increasing the precipitate size and results in lower mechanical properties.
Mechanical property degradation is dependent on the
temperature and time at temperature. Welding may
overage only the HAZ, but brazing may overage the
entire workpiece.
Phosphorus-Deoxidized Copper
Phosphorus-deoxidized copper (UNS C12000 and
C12300) contains 0.004% to 0.065% residual phosphorus. The electrical conductivity of these coppers
decreases in proportion to the amount of residual phosphorus. Electrical conductivity is about 100% IACS
when the phosphorus content is 0.009, about 85%
IACS when the phosphorus content is 0.02%, and
about 75% IACS when the phosphorus content is
0.04%.
Free-Machining Copper
Free-machining coppers, UNS C14500–C14710,
contain additions of lead, bismuth, tellurium, and selenium. Copper has very low solid-solution solubility for
these elements. Lead disperses throughout the matrix as
fine, discrete particles, while tellurium and sulfur form
hard stringers in the matrix. These inclusions reduce the
ductility of copper, but enhance machinability. Fusion
COPPER-ZINC ALLOYS (BRASS)
Copper alloys in which zinc is the major alloying element are generally classified as brasses (UNS C20500–
C49080, C66400–C69950, and C83300–C86800).
Some copper-zinc alloys have other common names or
trade names, such as commercial bronze, Muntz metal,
manganese bronze, and low-fuming bronze. Other elements are occasionally added to brasses to enhance
particular mechanical or corrosion characteristics. Additions of manganese, tin, iron, silicon, nickel, lead,
or aluminum, singly or collectively, rarely exceed 4%.
Some of the special brasses are identified by the name of
the second alloying element; two examples are aluminum
bronze and tin bronze.
The addition of zinc to copper decreases the melting
temperature, density, electrical and thermal conductivity, and the modulus of elasticity. Additions of zinc
increase the strength, hardness, ductility, and the coefficient of thermal expansion. The hot-working properties
AWS WELDING HANDBOOK
of brass decrease as zinc content, up to about 20%, is
increased.
The color of brass changes with increasing zinc
content, starting as red, followed by gold, on to light
gold, and finally to yellow. When joint appearance is
important, the welding filler metal should match the
brass color.
Most brasses are single-phase, solid-solution copperzinc alloys with good room-temperature ductility.
Brasses containing about 36% or more zinc have two
microstructural phases, alpha and beta. The beta phase
improves the hot-working characteristics of brass, but
has little effect on electrical and thermal conductivity.
For joining considerations, brasses can be divided
into three groups:
1. Low-zinc brasses (zinc content 20% maximum)
that have good weldability;
2. High-zinc brasses (zinc content greater
than 20%) that have only fair weldability; and
3. Leaded brasses that are considered unweldable,
but can be satisfactorily brazed and soldered.
The cast brasses contain from 2% to 41% zinc (UNS
C83300–C85800) but often have one or more additional alloying elements, which may include tin, lead,
nickel, and phosphorus. Cast alloys are generally not as
homogeneous as the wrought products. In addition to
welding complications caused by lead and other alloy
elements, the variation in microstructure can cause
difficulty during welding. Cast alloys without lead
are only marginally weldable, and leaded brasses are
generally not weldable.
Manganese bronzes (UNS C86100–C86800) are
actually high-tensile-strength brasses that contain 22%
to 38% zinc with varying amounts of manganese,
aluminum, iron, and nickel. Manganese bronze is
weldable, provided that it has a low content of lead.
Gas shielded arc welding processes are recommended.
Manganese bronzes can be brazed and soldered with
special fluxes.
COPPER-TIN ALLOYS (PHOSPHOR
BRONZE)
Alloys of copper and tin contain between 1% and
10% tin. These alloys are known as phosphor bronzes
because 0.03% to 0.04% phosphorus is added during
casting as a deoxidizing agent. The wrought alloys are
identified by UNS C50100–C52400. The cast coppertin alloys (UNS C90200–C91700) are similar to the
wrought alloys but often have additions of zinc or
nickel and contain high amounts of tin, up to 20%.
Leaded copper-tin alloys (UNS C92200–C94500) are
also available.
CHAPTER 3—COPPER AND COPPER ALLOYS
223
In the completely homogenized condition, the lowtin alloys are single-phase with a structure similar to
alpha brass. The alloys containing more than 5% tin
are difficult to cast without dendritic segregation and
the formation of a beta phase. During cooling, this beta
phase gives rise to a delta phase, which can cause
embrittlement.
In the wrought form, copper-tin alloys are tough,
hard, and highly resistant to fatigue, particularly in the
cold-worked condition. The phase diagram predicts the
precipitation of a copper-tin compound at room temperature; this, however, is not observed. Some very fine
precipitation can occur during cold working, which
accounts for the very high strength achieved in wrought
material. Electrical and thermal conductivity is low for
the low-tin alloys (less than 4% tin) and very low for
those with high-tin content.
Copper-tin alloys have a narrow plastic range and
must be hot worked at temperatures from 621°C to
677°C (1150°F to 1250°F). Low-tin alloys have the best
hot-working properties.
All of the copper-tin alloys have good cold-working
properties and high strength and hardness in the hardrolled tempers. After cold working, these alloys can be
rendered soft and malleable by annealing at temperatures between 482°C and 760°C (900°F and 1400°F),
depending on the properties desired. In a stressed condition, these alloys are subject to hot cracking. High preheat temperatures, high-heat-input welding, and slow
cooling rates should be avoided.
Leaded copper-tin alloys (UNS C53400 and
C54400) contain 2.0% to 6.0% lead to improve
machinability. Welding of these alloys is not recommended; however, welds can be made in some alloys.
Leaded copper-tin alloys are often two-phase structures, have a wide solidification range, and can be
severely cored unless homogenized. Weldability
decreases as lead content increases. Leaded copper-tin
alloys can be welded (with careful attention to welding
conditions) using the shielded metal arc welding
(SMAW) process. The covered electrode provides the
shielding for this process. Welding processes that are
shielded with inert gas are not recommended because
porosity in the welds will result. These alloys can be
brazed and soldered if not strained while in the hotshort temperature range.
Arc welding of cast leaded copper-tin alloys (UNS
C92200–C94500) is not recommended; but with care,
these alloys can be brazed and soldered.
COPPER-ALUMINUM ALLOYS
(ALUMINUM BRONZE)
Copper-aluminum alloys, the aluminum bronzes
(UNS C60600–C64400 and C95200–C95900), contain
224
CHAPTER 3—COPPER AND COPPER ALLOYS
from 3% to 15% aluminum, with or without varying
amounts of iron, nickel, manganese, and silicon. The
two types of aluminum bronzes are categorized by metallurgical structure and response to heat treatment. The
first type includes the alpha, or single-phase, alloys (less
than 7% aluminum) that cannot be hardened by heat
treatment. The second type includes the two-phase,
alpha-beta alloys. Both types have low electrical and
thermal conductivity that enhance weldability.
The alpha aluminum bronzes are readily weldable
without preheating. Aluminum bronzes with an aluminum content below approximately 8.5% have a tendency to be hot-short, and cracking can occur in the
HAZ of highly stressed weldments.
The single-phase alloy welded with an electrode that
spans the aluminum solubility limit results in the weldment being two-phase at elevated temperature, but has
a higher alpha-beta ratio at room temperature. The
resulting weldment has better hot-working characteristics at elevated temperatures and sufficient strength at
room temperature to match the single-phase (alpha)
base metal. The low content of residual elements in
UNS C61300 improves most welding properties.
Generally, aluminum bronzes that contain from
9.5% to 11.5% aluminum have both alpha-phase and
beta-phase microstructures. These two-phase alloys can
be strengthened by heat treatment to produce a
martensitic-type structure and tempered to obtain the
desired mechanical properties. In many respects, the
microstructures existing after heat treatment are analogous to those found in steels. Hardening is accomplished by quenching in water or oil from 843°C to
1010°C (1550°F to 1850°F), followed by tempering at
temperatures between 427°C and 649°C (800°F and
1200°F). Selection of the specific heat treatment
depends on the composition of the alloy and the desired
mechanical properties.
Two-phase alloys have very high tensile strength
compared to most other copper alloys. As the aluminum content of these alloys increases, ductility
decreases and hardness increases. Alpha-beta alloys
have a plastic range wider than the alpha alloys, and
this contributes to good weldability.
Aluminum bronzes resist oxidation and scaling at
elevated temperatures due to the formation of aluminum oxide on the surface; however, all aluminum oxide
must be removed before welding, brazing, or soldering.
The single-phase aluminum bronzes (UNS C60600,
C61300, and C61400) are produced as wrought alloys
only, although the single-phase nickel aluminum
bronzes (UNS C63200–C95800) are produced both as
castings and wrought products. Duplex aluminum
bronzes are produced in cast and wrought forms and
have similar characteristics. The duplex aluminum
bronzes are temper annealed to resist de-aluminification
in a sea water environment, and unless welding is of a
AWS WELDING HANDBOOK
very minor nature, the workpiece should be tempered
again or annealed after welding.
Nickel-aluminum bronzes contain from 8.5% to
11% aluminum and from 3% to 5% nickel; both have
alpha and kappa phases in the microstructure. Alloys
with aluminum content in the upper end of the range
can contain the eutectoid phase, gamma 2 (γ2), when
cooled slowly from elevated temperature. A temper
anneal at 620°C to 663°C (1150°F to 1225°F), followed by rapid cooling in air is recommended for alloys
that will be exposed to corrosive environments.
Aluminum bronze should not be welded using
nickel-aluminum-bronze filler metal, because this filler
has low ductility and may be susceptible to cracking;
therefore, recommended procedures for welding heavy
sections include the use of a nickel-free filler metal
(ECuAl-A2, ERCuAl-A2) to fill the joint. The ECuAlA2 or ERCuAl-A2 filler metal is recommended for the
root pass and for all but the last two or three cover
passes. The final two or three passes should be made
with a nickel-aluminum bronze filler metal (ECuNiAl,
ERCuNiAl). It should be noted that this procedure
should not be employed if there is any possibility that
the ECuAl-A2 or ERCuAl-A2 weld metal will be
exposed by subsequent drilling, machining, or similar
processing. Nickel-aluminum-bronze weldments should
be temper annealed for service in corrosive environments.
COPPER-SILICON ALLOYS (SILICON
BRONZE)
Copper-silicon alloys (UNS C64700–C66100 and
C87300–C87900), known as silicon bronzes, are industrially important because they have high strength, excellent corrosion resistance, and good weldability. The
wrought alloys (UNS C64700–C66100) contain from
1.5% to 4% silicon and 1.5% or less of zinc, tin, manganese, or iron. With the exception of alloy C87300,
the cast silicon bronze alloys have higher zinc levels
(4% to 30%), which improves castability.
The addition of silicon to copper alloys increases tensile strength, hardness, and the rate of work hardening.
The ductility of silicon bronze alloys decreases with
increased silicon content, up to about 1%. Ductility
then increases to a maximum value at 4% silicon. Electrical and thermal conductivity decreases as the silicon
content increases. Silicon bronzes should be stressrelieved or annealed prior to welding, and should be
slowly heated to the desired temperature. Silicon
bronzes exhibit hot-shortness at elevated temperatures
and should be rapidly cooled through the critical temperature range.
Additions of iron increase tensile strength and hardness. Additions of zinc or tin improve the fluidity of
AWS WELDING HANDBOOK
molten bronze. This also improves the quality of castings and of welds made using oxyfuel gas welding.
COPPER-NICKEL ALLOYS
Commercial copper-nickel alloys (UNS C70100–
C72950 and C96200–C96900) have a nickel content
ranging from 5% to 45%. The copper-nickel alloys
most commonly used in welded fabrications contain
from 10% to 30% nickel and minor alloying elements
such as iron, manganese, or zinc. Resistance to corrosion caused by erosion requires that any addition of
iron should be in solid solution. Thermal processing of
the copper-nickel alloy must be done in a manner that
does not cause precipitation of iron compounds.
The copper-nickel alloys are moderately high in tensile strength, which increases in proportion to nickel
content. These alloys are ductile and relatively tough,
and they are relatively low in electrical and thermal
conductivity.
Like nickel and some nickel alloys, the copper-nickel
alloys are susceptible to lead or sulfur embrittlement.
Phosphorus and sulfur levels in these alloys should be a
maximum of 0.02% to ensure sound welds. Contamination from sulfur-bearing marking crayons or cutting
lubricants can cause cracking during welding.
Most copper-nickel alloys do not contain a deoxidizer, which means that fusion welding requires the
addition of a deoxidized filler metal to avoid porosity.
Special compositions of some copper-nickel alloys that
contain titanium can be obtained. These special alloys
are recommended for the autogenous welding of thin
sheet. Silicon is added to cast alloys for improved fluidity during casting and for added strength of the cast
structure.
CHAPTER 3—COPPER AND COPPER ALLOYS
225
WELDING AND JOINING
PROCESSES
Copper and copper alloys can be joined by welding,
brazing, and soldering processes. The most commonly
used joining processes and applicability ratings for the
major alloy classifications of copper and copper alloys
are summarized in Table 3.3.
FUSION WELDING PROCESSES
Nickel silvers (UNS C73200–C79900 and C97300–
C97800) are produced by adding nickel to copper-zinc
alloys. The addition of silver increases strength and
corrosion resistance, and also makes the metal silvery
in appearance, a feature often used when decorative
or cosmetic enhancement is needed. The welding
metallurgy of these alloys is similar to that of the
brasses. Nickel-silver alloys are classified in two general
types:
Copper and most copper alloys can be joined by arc
welding processes, preferably those that use gas shielding, i.e., gas tungsten arc welding (GTAW), gas metal
arc welding (GMAW), and plasma arc welding (PAW).
Shielded metal arc welding (SMAW) can be used for
noncritical applications.
Argon or helium, or mixtures of the two, are used as
shielding gases for GTAW, GMAW, and PAW. In general, argon is used for manual welding of base metal
that is either less than 3.3 mm (0.13 in.) thick or has
low thermal conductivity, or both. Helium or a mixture
of 75% helium-25% argon is recommended for mechanized welding of thin sections and for the manual welding of thicker sections or alloys having high thermal
conductivity. Small additions of nitrogen or hydrogen
to the argon shielding gas can be used to increase the
effective heat input.
The SMAW process can be used to weld copper
alloys in a range of thicknesses. Covered electrodes for
welding copper alloys are available in standard sizes ranging from 2.4 mm to 4.8 mm (0.94 in. to 0.188 in.).4
Other sizes are available in certain electrode classifications for shielded metal arc welding. (Submerged arc
welding has been used for welding of copper alloys,
although use of this process is not widespread.)
Arc welding should be done in the flat position when
practical; GTAW or SMAW is preferred for welding in
positions other than flat, particularly in the overhead
position. Pulsed gas metal arc welding (GMAW-P) used
with small-diameter electrodes is also suitable for welding some copper alloys in the vertical and overhead
positions. Compared to steel, the thermal conductivity
and thermal expansion are higher in copper and copper
alloys; this results in greater weld distortion in copper
welds than that occurring in comparable welds in steel.
The use of preheat, fixtures, tack welds and proper
welding sequences can minimize distortion or warping.
1. Single-phase alloys containing 65% copper added
to nickel-zinc alloys; and
2. Two-phase (alpha and beta) alloys
4. American Welding Society (AWS) Committee on Filler Metals and
Allied Materials, 2008, Specification for Copper and Copper-Alloy
Electrodes for Shielded Metal Arc Welding, AWS A5.6/A5.6M:2008,
Miami: American Welding Society
COPPER-NICKEL-ZINC ALLOYS (NICKEL
SILVER)
226
CHAPTER 3—COPPER AND COPPER ALLOYS
AWS WELDING HANDBOOK
Table 3.3
Applicable Joining Processes for Copper and Copper Alloys
Shielded
Gas
Gas
Metal
Metal Tungsten
Arc
Arc
Arc
Resistance Solid-State
Welding Welding Welding Welding
Welding
UNS No.
Oxyfuel
Gas
Welding
C11000–
C11900
NR
NR
F
F
NR
Oxygen-Free Copper
C102000
F
NR
G
G
Deoxidized Copper
C12000
C123000
G
NR
E
C17000–
C17500
NR
F
G
Cadmium-Chromium
Copper
C16200
C18200
NR
NR
G
G
NR
F
G
G
F
Red Brass—85%
C23000
F
NR
G
G
F
G
E
E
—
Low Brass—80%
C24000
F
NR
G
G
G
G
E
E
—
Cartridge Brass—70%
C26000
F
NR
F
F
G
G
E
E
—
Leaded Brasses
C31400–
C38590
NR
NR
NR
NR
NR
NR
E
G
—
Phosphor Bronzes
C50100–
C52400
F
F
G
G
G
G
E
E
—
Alloy
ETP Copper
Beryllium Copper
Brazing
Soldering
Electron
Beam
Welding
G
E
G
NR
NR
E
E
E
G
E
NR
E
E
E
G
G
F
F
G
G
F
Copper Nickel—30%
C71500
F
F
G
G
G
G
E
E
F
Copper Nickel—10%
Nickel Silvers
C70600
C75200
F
G
G
NR
E
G
E
G
G
F
G
G
E
E
E
E
G
—
Aluminum Bronzes
C61300
C61400
NR
G
E
E
G
G
F
NR
G
G
F
E
E
G
G
E
G
G
Silicon Bronzes
C65100
C65500
E = Excellent G = Good F = Fair
NR = Not Recommended.
Oxyfuel Gas Welding
Copper and many copper alloys can be welded with
the oxyfuel gas welding (OFW) process, including
repair welding, but this process should be used only for
small, noncritical applications. The relatively low heat
input of the oxyacetylene flame makes welding slow,
compared to arc welding. Higher preheat temperatures
or an auxiliary heat source might be required to compensate for the low heat input, particularly when welding thick sections of copper or when welding alloys
with high thermal conductivity. A welding flux is
required to exclude air from the weld metal at elevated
temperatures, except when welding oxygen-free copper.
Laser Beam Welding
Laser beam welding (LBW) of copper and copper
alloys has limited application, primarily because of the
high reflectivity to the incident laser beam and the high
thermal conductivity of copper and copper alloys. Copper reflects approximately 99% of the incident light
energy of the infrared wave length of a CO2 laser beam.
This is the reason copper is commonly used for mirrors
in CO2 laser beam delivery systems. Reflectivity is temperature dependent; when a material gets hotter, the
absorption of the incident light increases. The high thermal conductivity of copper, however, prevents the
metal from getting hotter, thereby maintaining high
reflectivity.
The use of laser beam systems with shorter wave
lengths has been successful in welding some copper
alloys. Copper has slightly higher absorption of the
incident light of Nd:YAG lasers that have a wavelength
of 1.06 μm. Plating copper with a thin layer of higher
absorptive metal, such as nickel, results in improved
coupling efficiency. New, high-powered solid-state lasers
are better than previous systems because the keyhole
AWS WELDING HANDBOOK
mode of welding can be established; however, welds in
thick copper sections are still difficult to produce, due
to the amount of reflected energy from the copper.
Laser beam welding is a fusion welding process;
therefore, the same considerations pertinent to other
fusion processes apply. Higher susceptibility to cracking
can be encountered with copper alloys with wide liquidus-to-solidus temperature ranges due to the high solidification stresses resulting from the rapid cooling rates
characteristic of laser beam welding.
Electron Beam Welding
Copper and copper alloys can be readily joined by
electron beam welding (EBW). The EBW process has
been successfully applied for welding thin-gage and
thick-gage copper alloys, both in and out of vacuum.
Filler metal can be added to a weld with an auxiliary
welding wire feeder.
CHAPTER 3—COPPER AND COPPER ALLOYS
227
Flash Welding
The flash welding (FW) process produces very good
results on copper and copper alloys. The design of the
equipment must provide accurate control of all welding
conditions, including upset pressure, platen travel,
flash-off rate, current density, and flashing time.
Leaded copper alloys can be flash welded, but the
integrity of the joint depends on the composition of the
alloy. Lead content up to 1.0% is usually not detrimental.
Rapid upsetting at minimum pressure is necessary as
soon as the abutting faces are molten because of the
relatively low melting temperature and narrow plastic
range of copper alloys. Light pressure is usually applied
to the joint before the flashing current is initiated so
that platen motion will begin immediately after flashing
starts. Termination of flashing current is critical. Premature termination of current will result in incomplete
fusion at the weld interface. Excessive flashing will
overheat the metal and result in improper upsetting.
Resistance Spot Welding
High-Frequency Resistance Seam Welding
Many of the copper alloys with lower conductivity
are readily welded using the resistance spot welding
(RSW) process. The ease with which resistance spot
welding produces welds in copper and copper alloys
varies inversely with the electrical and thermal conductivity of the specific alloy.
Spot welds can be made in copper-alloy sheet that
has an electrical conductivity of 30% IACS or less;
these include beryllium copper, many of the brasses and
bronzes, nickel silver, and copper-nickel alloys. Weld
quality becomes less consistent as the electrical conductivity increases. Copper alloys with electrical conductivity higher than 60% cannot be spot welded with
conventional methods. Resistance spot welding of unalloyed copper is not practical.
Electrode force for the resistance spot welding of
copper-alloy sheet is usually set to 50% to 70% of that
used for the same thickness of steel. Welding current is
higher and welding time is shorter than those used for
steel. Tungsten-tipped or molybdenum-tipped RSW
electrodes are preferred because they minimize electrode sticking.
One of the most prominent uses of high-frequency
resistance seam welding (RSEW-HF) is in tube mills for
the manufacturing of copper and copper alloy tubing
from strip. The edges of the joint are resistance heated
to welding temperature, using the “skin effect” with
high-frequency current. The heated edges are forged
together continuously to complete the welded tube.
Resistance Seam Welding
It is difficult to make seam welds in copper alloys
using resistance seam welding (RSEW) because of
excessive shunting of welding current, high thermal
conductivity, and low contact resistance of the electrode. Seam welding is generally not practicable when
the electrical conductivity exceeds 30% IACS; however,
copper alloys that can be spot welded can usually be
seam welded.
SOLID-STATE PROCESSES
Copper is readily welded using solid-state welding
(SSW), a group of processes that produces coalescence
by the application of pressure without melting any of
the joint components. The solid-state processes used for
the welding of copper and copper alloys require various
combinations of temperature, pressure, and deformation to weld the components.
Annealed copper can be joined by cold welding
(CW) at room temperature because of the excellent
malleability of this material. Copper tubing can be
welded and pinched off using commercially available
steel dies. Copper and copper alloys can also be joined
using the friction welding (FRW), diffusion welding
(DFW), and explosion welding (EXW) processes.
Friction Welding
Friction welding (FRW) is a solid-state welding process that produces a coalescence of materials under
compressive force by rotating or moving the workpieces
relative to one another. This produces heat and plastically displaces material from the faying surfaces.
228
CHAPTER 3—COPPER AND COPPER ALLOYS
Although limited in application, the use of friction
welding can result in several advantages when joining
copper and copper alloys: the heat-affected zone is very
narrow, the joint contains no cast-metal microstructure,
and joint properties are excellent.5
Friction welding can be used to join copper alloys to
copper alloys and to join copper alloys to other materials. Brasses and bronzes can be successfully welded to
other brasses and bronzes, but copper is also compatible with many dissimilar materials, including carbon
steel, stainless steel, aluminum, zirconium, titanium,
and silver. In nonstructural applications, other material
systems can be joined to copper and copper alloys.
The friction welding process is very useful for applications in which components or component blanks can
be fastened into the welding equipment. Figure 3.1
shows an oxygen-free high conductivity (OFHC) electrical tab joined to an unalloyed aluminum component
of an electrical connector, with an as-welded blank for
machining and a pinned connector fitting. Joints of this
type are commonly used in electrical applications in
which the more expensive copper material can be
replaced with aluminum. The high-quality joint produced between the copper and aluminum ensures that
no oxide film forms at the interface, which is a problem
with mechanically joined workpieces.
Alloyed aluminum, especially AA4043, can be used
in applications that require the soldering of pins or
welding to pin-type electrical connectors, as shown in
Figure 3.2. The OFHC copper section is readily soldered
5. Refer to American Welding Society (AWS) Welding Handbook
Committee, 2004, Welding Handbook, 9th Ed., Vol. 3, Welding Processes, Chapter 6, Friction Welding.
AWS WELDING HANDBOOK
(A) As Welded, Aluminum-to-Copper Ground
Pin, with Flash on Aluminum Side Only
(B) Reduced Section
Tensile Test
(C) Reduced Section
Bend Test
Figure 3.1—Aluminum-to-Copper Connectors
Figure 3.2—(A) A Ground Pin with an
Inertia Friction-Welded Transition Joint
between 4043 Aluminum and Oxygen-Free
High-Conductivity Copper, (B) Tensile
Test, and (C) Bend Test
AWS WELDING HANDBOOK
to copper, silver, or gold pin connectors and the
AA4043 section is readily welded to other aluminum
alloys in aluminum connectors.
The joint strength and other properties associated
with stainless steel-to-copper and aluminum-to-copper
welds are quite good. Due to the low heat input of friction welding and the low strength of copper, thermally
induced or mechanically induced phase changes are
rare, unless the joint is used in high-temperature applications, where deleterious phases can be created
through diffusion at the interface. Figure 3.3 shows
a copper-to-stainless steel friction weld, a large flash
formed on the copper (right) side of the joint.
Figure 3.4 shows a copper-to-aluminum friction
weld, where a large flash is formed on the aluminum
(left) side of the joint. Figure 3.5 and Figure 3.6 indicate
that the hardness of the base materials and joint areas
remains consistent throughout the workpiece and is
typical of the base metal properties. The weld flash is
consistent with the properties of the materials in these
joints. Much larger flash forms on the copper side when
copper is welded to stainless steel and much larger flash
forms on the aluminum side when aluminum is welded
to copper.
CHAPTER 3—COPPER AND COPPER ALLOYS
229
Note: Large flash is formed on the aluminum (left) side of the joint.
Source: Sahin, M., 2011, Friction Welding of Different Materials, in Proceedings: International Scientific Conference UNITECH 2011 Techniceski Universitet, Gabrovo, Turkey.
Figure 3.4—Copper-to-Aluminum Friction Weld
BRAZING AND SOLDERING
Copper and copper alloys are readily joined by brazing (B) using an appropriate filler metal and flux or a
Note: Flash is formed on the copper (right) side of the joint.
Source: Sahin, M., 2011, Friction Welding of Different Materials, in Proceedings: International Scientific Conference UNITECH 2011,Techniceski Universitet, Gabrovo, Turkey.
Figure 3.3—Copper-to-Stainless Steel
Friction Weld, with Flash on Copper Side
protective atmosphere. Any of the common heating
methods can be used. Certain precautions are required
with specific base metals to avoid embrittlement, cracking, or excessive alloying with the filler metal. Special
fluxes are required when brazing alloys that form
refractory surface oxides.
Copper and most copper alloys are readily joined by
soldering (S) using commercial soldering filler metals.
Most copper alloys are easily fluxed, except those containing elements that form refractory oxides (e.g., beryllium, aluminum, silicon, or chromium). Special fluxes
are required to remove refractory oxides that form on
the surfaces of these alloys.
Soldering is primarily used for electrical connections,
plumbing, and other room-temperature applications.
Soldered joints are not as strong as brazed or welded
joints.
FILLER METALS
Covered electrodes and bare electrode wire and rods
are available for welding copper and copper alloys to
the same metals and to dissimilar metals. These filler
metals are included in the specifications published by
230
CHAPTER 3—COPPER AND COPPER ALLOYS
AWS WELDING HANDBOOK
STAINLESS STEEL (AISI 304)—COPPER
(d = 10 mm – d = 10 mm)
COPPER
STAINLESS STEEL
300
275
250
VICKERS HARDNESS (HV)
225
200
175
150
125
100
75
50
25
0
–4
–3
–2
–1
0
1
2
3
4
HORIZONTAL DISTANCE (mm)
Source: Sahin, M., 2011, Friction Welding of Different Materials, in Proceedings: International Scientific Conference UNITECH 2011,
Techniceski Universitet, Gabrovo, Turkey.
Figure 3.5—Hardness Results on Horizontal Distance of Copper-to-Stainless Steel Welds
the American Welding Society.6, 7 AWS classifications
of filler metals for welding copper and copper alloys are
listed in Table 3.4.
6. American Welding Society, AWS A5.6 Committee on Filler Metals
and Allied Materials, 2008, Specification for Copper and CopperAlloy Electrodes for Shielded Metal Arc Welding, A5.6/A5.6M:2008,
Miami: American Welding Society.
7. American Welding Society, AWS A5.7 Committee on Filler Metals
and Allied Materials, 2007, Specification for Copper and Copper
Alloy Bare Welding Rods and Electrodes, A5.7/A5.7M:2007, Miami:
American Welding Society.\
COPPER FILLER METALS
Bare copper electrodes and rods (ERCu) are generally produced with a minimum copper content of 98%.
The electrical conductivity of ERCu electrodes is 25%
to 40% IACS. These electrodes and rods are used to
weld deoxidized and electrolytic tough-pitch copper
with one of the shielded arc processes: gas metal arc
welding (GMAW), gas tungsten arc welding (GTAW),
or plasma arc welding (PAW). In some cases these electrodes and rods can be used with the oxyfuel gas welding (OFW) process.
Covered electrodes (ECu) for shielded metal arc
welding (SMAW) are designed for welding with direct
AWS WELDING HANDBOOK
CHAPTER 3—COPPER AND COPPER ALLOYS
231
COPPER—ALUMINIUM
(d = 10 mm – d = 10 mm)
COPPER SIDE
ALUMINUM SIDE
150
VICKERS HARDNESS (HV)
125
100
75
50
25
0
–4
–3
–2
–1
0
1
2
3
4
HORIZONTAL DISTANCE (mm)
Source: Sahin, M., 2011, Friction Welding of Different Materials, in Proceedings: International Scientific Conference UNITECH 2011,
Techniceski Universitet, Gabrovo, Turkey.
Figure 3.6—Hardness Results on Horizontal Distance of Copper-to-Aluminum Welds
current electrode positive (DCEP). The required welding current is 30% to 40% higher than that usually
required for carbon steel electrodes of the same diameter.
Copper-Zinc (Brass) Filler Metals
Copper-zinc welding rods are available in the following classifications: RBCuZn-A (naval brass), RBCuZnB (low-fuming brass), and RBCuZn-C (low-fuming
brass). These welding rods are primarily used for the
oxyfuel gas welding of brass and for the braze welding
of copper, bronze, and nickel alloys.
The RBCuZn-A welding rods contain 1% tin to
improve corrosion resistance and strength. Electrical
conductivity of these rods is about 25% IACS, and the
thermal conductivity is about 30% of that of copper.
Welding rods in the RBCuZn-B class contain additions of manganese, iron, and nickel to increase hardness and strength. A small amount of silicon is added to
provide low-fuming characteristics.
The RBCuZn-C welding rods are similar in composition to RBCuZn-B rods, except that they do not contain
nickel. The mechanical properties of as-deposited weld
metal from these rods are similar to those of naval
brass.
It should be noted that copper-zinc filler metals cannot be used as electrodes for arc welding because of the
high zinc content. The zinc vapor would volatilize from
the weld pool, which would result in porous weld
metal.
Copper-Tin (Phosphor-Bronze) Filler
Metals
Copper-tin (phosphor bronze) welding electrodes
and rods include ECuSn-A, ERCuSn-A, and ECuSn-C.
The ECuSn-A composition contains about 5% tin; the
ECuSn-C composition has about 8% tin. Both electrodes are deoxidized with phosphorus. These electrodes can be used for welding bronze, brass, and also
232
CHAPTER 3—COPPER AND COPPER ALLOYS
AWS WELDING HANDBOOK
Table 3.4
Filler Metals for Fusion Welding of Copper Alloys
AWS Classification
Covered Electrodea
Bare Wireb
Common Name
Base Metal Applications
ECu
ERCu
Copper
ECuSi
ERCuSi-A
Silicon bronze
Coppers
Silicon bronzes, brasses
ECuSn-A
ERCuSn-A
Phosphor bronze
Phosphor bronzes, brasses
ECuSn-C
ERCuSn-A
Phosphor bronze
Phosphor bronzes, brasses
ECuNi
ERCuNi
Copper nickel
Copper-nickel alloys
ECuAl-A2
ERCuAl-A1
Aluminum bronze
Aluminum bronzes, brasses
silicon bronzes, manganese bronzes
ERCuAl-A2
—
ECuAl-B
ERCuAl-A3
Aluminum bronze
ECuNiAl
ERCuNiAl
—
Nickel-aluminum bronzes
ECuMnNiAl
ERCuMnNiAl
—
Manganese-nickel-aluminum bronzes
Aluminum bronzes
RBCuZn-A
Naval brass
Brasses, copper
RBCuZn-B
Low-fuming brass
Brasses, manganese bronzes
RBCuZn-C
Low-fuming brass
RBCuZn-D
—
Brasses, manganese bronzes
Nickel silver
a. See AWS A5.6/A5.6M:2008, Specification for Copper and Copper-Alloy Electrodes for Shielded Metal Arc Welding.
b. See AWS A5.7/A5.7M:2007, Specification for Copper and Copper-Alloy Bare Welding Rods and Electrodes, and AWS A5.8/A5.8M:2004, Specification for
Filler Metals for Brazing and Braze Welding.
copper, if the presence of tin in the weld metal is not
objectionable.
The ECuSn-A, ERCuSn-A, and ECuSn-C electrodes
are frequently used for the repair of castings. Rods with
the ERCuSn-A classification can be used with the
GTAW process for joining phosphor bronze. The
ECuSn-C electrodes provide weld metal with better
strength and hardness than the ECuSn-A electrodes and
are preferred for welding high-strength bronzes. Preheat
and interpass temperature of about 203°C (400°F) is
required when welding with these electrodes, especially
when welding heavy copper sections.
per-silicon weld metal is about twice that of ERCu weld
metal. The electrical conductivity is about 6.5% IACS,
and the thermal conductivity is about 8.4% of that of
copper.
Covered electrodes ECuSi are used primarily for
welding copper-zinc alloys using direct current electrode positive (DCEP). This electrode is occasionally
used for welding silicon bronze, copper, and galvanized
steel. The core wire of these covered electrodes contains
about 3% silicon and small amounts of tin and manganese. The mechanical properties of the weld metal are
usually slightly higher than those of copper-silicon base
metal.
Copper-Silicon (Silicon-Bronze) Filler
Metals
Copper-Aluminum (Aluminum-Bronze)
Filler Metals
Copper-silicon (silicon-bronze) electrodes are used in
bare wire form (ERCuSi-A) for GMAW, for GTAW,
and sometimes for OFW. Copper-silicon welding wires
contain from 2.8% to 4.0% silicon, with about 1.5%
manganese, 1.0% tin, and 1.0% zinc. This filler wire is
used for welding silicon bronzes and brasses and to
braze weld galvanized steel. The tensile strength of cop-
ERCuAl-A1 filler metal is an iron-free aluminum
bronze. It is used as a surfacing alloy to produce wearresistant surfaces designed for relatively light loads, for
resistance to corrosive media such as salt water and
brackish water, and for resistance to some commonly
used acids. This alloy is recommended for cladding
applications but not for joining.
AWS WELDING HANDBOOK
CHAPTER 3—COPPER AND COPPER ALLOYS
233
Covered electrodes ECuAl-A2 for SMAW contain
from 6.5% to 9% aluminum. ERCuAl-A2 bare wire
electrodes for GTAW, GMAW, and PAW contain from
8.5% to 11% aluminum. ERCuAl-A2 weld metal has
higher strength than the ECuAl-A2 weld metal. Both of
these filler metals are used for joining aluminum
bronze, silicon bronze, copper-nickel alloys, copperzinc alloys, manganese bronze, and many combinations
of dissimilar metals.
Covered electrodes ECuAl-B contain 7.5% to 10%
aluminum, and produce deposits with higher strength
and hardness than the ERCuAl-A2 electrodes. These
electrodes are used for surfacing applications and for
repair welding of aluminum bronze castings of similar
composition.
Electrodes and rods (ERCuAl-A3) are used for repair
welding of similar compositions of aluminum-bronze
castings using the GMAW and GTAW processes. The
high aluminum content of ERCuAl-A3 electrodes and
rods lessens the tendency for cracking in highly stressed
sections.
Copper-nickel-aluminum electrodes and bare-wire
electrodes (ECuNiAl and ERCuNiAl) are used to join
and repair both wrought and cast nickel-aluminum
bronze materials. These electrodes can be used for
applications requiring good corrosion resistance, and
erosion or cavitation resistance in salt water and brackish water.
Covered electrodes ECuMnNiAl and bare filler
metal ERCuMnNiAl are used to join manganese-nickelaluminum bronzes of similar composition. These electrodes are used in applications requiring resistance to
cavitation, erosion, and corrosion.
steel. The larger groove angles are required to provide
adequate fusion and penetration for copper alloys that
have high thermal conductivity.
Copper-Nickel Filler Metals
Preheat
Copper-nickel covered electrodes, (ECuNi) and bare
electrode wire and rods (ERCuNi) are typically 70%
copper and 30% nickel. These filler metals contain titanium to deoxidize the weld pool and are used for welding all copper-nickel alloys.
The selection of a preheat temperature for a given
application depends on the welding process, the alloy
being welded, the base metal thickness, and to some
extent, the overall mass of the weldment. Welding thin
copper sections requires less preheat than that required
for thick sections; also, using high-energy-density welding processes generally requires less preheat than that
required for low-energy density welding processes. The
GMAW process usually requires less preheat than
GTAW or OFW. When welding conditions are similar,
copper requires higher preheat temperatures than copper alloys because of high thermal conductivity. Aluminum bronze and copper-nickel alloys should not be
preheated.
When preheating is used, the base metal adjacent to
the joint must be heated uniformly to the specified temperature. The temperature should be maintained until
welding of the joint is completed. If welding is interrupted, the joint area should be preheated before welding is resumed.
JOINT DESIGNS FOR
COPPER WELDS
Recommended weld joint designs for copper and
copper alloys are shown in Figure 3.7 and Figure 3.8.
Figure 3.7 shows joint designs that are appropriate for
gas tungsten arc welding (GTAW) and shielded metal
arc welding (SMAW). Figure 3.8 shows joint designs
for gas metal arc welding (GMAW). Joint designs for
copper have larger groove angles than those used for
WELDING CONDITIONS
Prior to welding, joint faces and adjacent surfaces
should be clean and free of contaminants—oil, grease,
dirt, paint, and oxides. Wire brushing is not a suitable
cleaning method for copper alloys that develop a tenacious surface oxide, such as the aluminum bronzes.
These alloys should be cleaned by appropriate chemical
or abrasive methods. Degreasing with a suitable solvent
is also recommended.
HEAT TREATMENT
The relatively high thermal conductivity of copper
and the high-copper alloys results in the rapid conduction of heat from the weld joint into the surrounding
base metal. This makes it difficult to achieve weld penetration and complete fusion. Loss of heat from the weld
area can be minimized by using higher welding current
or using a high-energy-density welding process, such as
electron beam welding or laser beam welding. Preheating the base metal prior to welding is the most commonly used method of counteracting the effects of
thermal conduction.
234
CHAPTER 3—COPPER AND COPPER ALLOYS
1.5T
AWS WELDING HANDBOOK
WELDED FROM
THIS SIDE
0.75T MAX
T
T
(B) Square Groove
(A) Flanged Edge
70°–80°
80°–90°
B to C
B
T
T
C
C to D
(C) Single-V Groove
(D) Double-V Groove
R
15°
C
C
15°
A to B
T
T
R
A to B
A to B
(E) Single-U Groove
Key:
A = 1.6 mm (0.062 in.)
B = 2.4 mm (0.094 in.)
C = 3.2 mm (0.125 in.)
A to B
(F) Double-U Groove
D = 4.0 mm (0.156 in.)
R = 3.2 mm (0.125 in.)
T = thickness
Figure 3.7—Joint Designs for Shielded Metal Arc Welding and Gas Tungsten Arc Welding of Copper
Postweld Heat Treatment
Postweld heat treatment (PWHT) of copper and copper alloys can involve annealing, stress-relieving, or precipitation hardening. The need for PWHT depends on
the base metal composition and the service application
of the weldment. Postweld heat treatment may be
required if the base metal can be strengthened by a heat
treatment or if the service environment can cause stresscorrosion cracking.
Copper alloys that include the high-zinc brasses,
manganese-bronzes, nickel-manganese bronzes, some of
the aluminum bronzes, and nickel silvers are susceptible
to stress-corrosion cracking. Stresses induced during
welding of these alloys can lead to premature failure in
certain corrosive environments. These alloys can be
stress relieved or annealed after welding to reduce
stresses. Copper alloys that respond to precipitation
hardening include some high coppers, some copper-aluminum alloys, and copper-nickel castings containing
beryllium or chromium. If these alloys are not heat
treated, the hardness in the weld area will vary as a
result of aging or overaging caused by the thermal profile of welding conditions.
Stress Relief
Stress relief is performed to reduce stresses induced
by welding to relatively low values without substantially affecting mechanical properties. Stress relief is
AWS WELDING HANDBOOK
CHAPTER 3—COPPER AND COPPER ALLOYS
235
80°–90°
T
B
T
A to B
(A) Square Groove
(B) Single-V Groove
80°–90°
30°
T
B
T
B to C
(C) Double-V Groove
Key:
A = 1.6 mm (0.062 in.)
B = 2.4 mm (0.094 in.)
C = 3.2 mm (0.125 in.)
C
R
(D) Double-U Groove
R = 6.4 mm (0.250 in.)
T = thickness
Figure 3.8—Joint Designs for Gas Metal Arc Welding of Copper
accomplished by heating the weldment to a temperature
that is below the recrystallization temperature of the
base metal. Typical stress-relieving temperatures for
some copper alloys are listed in Table 3.5. Heating time
must be adequate to allow the entire weldment to reach
temperature. The weldment is usually held at the stressrelief temperature for at least one hour and then slowly
cooled. Weldments thicker than 25.4 mm (1 in.) must
be held at temperature for longer periods, usually for 1
hour per 25.4 mm (1 h per 1 in.) of thickness.
Annealing
Annealing is used to reduce stresses and to homogenize weldments made of hardenable copper alloys;
annealing produces a metallurgical structure that will
satisfactorily respond to heat treatment. Annealing is
carried out at temperatures considerably higher than
those used for stress-relieving, as shown in Table 3.6.
Stress relief proceeds rapidly at the annealing temperature. Extending the annealing times or annealing at the
top of the temperature range can cause excessive grain
growth that can reduce tensile strength and can cause
other adverse metallurgical effects.
Table 3.5
Typical Stress-Relieving Temperatures for
Weldments of Copper Alloys
Temperature*
Common Name
Red brass
Admiralty brass
Naval brass
Aluminum bronze
Silicon bronze
Copper-nickel alloys
UNS No.
°C
°F
C23000
C44300–C44500
C46400–C46700
C61400
C65500
C70600–C71500
288
288
260
343
343
538
550
550
500
650
650
1000
*Slowly heat to temperature and hold for at least 1 hour.
Heat Treatable Copper Alloys
Heat-treatable copper alloys of greatest commercial
use are those with the following UNS designations:
C17000, C17200, C17300, C17500, C17510, C18200,
and C15000. These materials can be supplied in any
form or condition specified by the user, and can be
hardened by means of one of the following sequences:
236
CHAPTER 3—COPPER AND COPPER ALLOYS
AWS WELDING HANDBOOK
Table 3.6
Annealing Temperature Ranges for Copper and Copper Alloys
Temperature Range*
Common name
Phosphor-deoxidized copper
UNS No.
°C
°F
C12200
371–649
700–1200
Beryllium copper
C17000, C17200
774–802
1425–1475
1675–1725
Beryllium copper
C17500
913–941
Red brass
C23000
427–732
800–1350
Yellow brass
C27000
427–704
800–1300
Muntz metal
Admiralty
C28000
427–593
800–1100
C44300–C44500
427–593
800–1100
Naval brass
C46400–C46700
427–593
800–1100
Phosphor bronze
C50500–C52400
482–677
900–1250
Aluminum bronze
C61400
607–899
1125–1650
1100–1200
Aluminum bronze
Silicon bronze
Aluminum brass
C62500
593–649
C65100, C65500
482–704
900–1300
C68700
427–593
800–1100
Copper nickel, 10%
C70600
593–816
1100–1500
Copper nickel, 30%
C71500
649–816
1200–1500
Nickel silver
C74500
593–760
1100–1400
*Time at temperature—15 min to 30 min.
1. Solution anneal, then cold work, and then age
harden.
2. Solution anneal, then age harden from the
solution-annealed state without cold working.
The solution-annealing temperature and age-hardening
temperatures vary for each heat-treatable copper alloy,
depending on the chemical composition of the alloy.
When a heat-treatable copper alloy is welded or
brazed (or to a lesser extent, when soldered) the
condition of the mill-supplied material is altered. It is
necessary to heat treat the welded assembly to return
the base metal, the heat-affected zone, and the weld
metal to approximately the mill-supplied condition.
This involves solution annealing, followed by age
hardening. It is usually not feasible to perform any cold
work on a welded assembly after solution annealing.
Solution Annealing. The solution-annealing procedure for beryllium-copper, UNS C17200 alloy (1.9%
beryllium), is to heat the workpiece to 788°C (1450°F).
Depending on the thickness, the workpiece is held at
temperature from 30 minutes to 3 hours. Because
beryllium-copper forms a tenacious and continuous
oxide
surface when heated in air or in an oxidizing
atmosphere, a slightly reducing atmosphere should be
used to produce a clean and bright workpiece after
quenching.
Quenching is critical to avoid any precipitation of
the beryllium intermetallic phase. The use of rapid
water quenching from the solution-anneal temperature
is the best method to ensure retention of beryllium in
solid solution. For weldments or castings that may
crack, quenching in oil or forced air can be used, but
this may result in some precipitation of the beryllium
intermetallic phase.
Age Hardening. Solution-annealed products are soft,
having a hardness of 45 to 85 Rockwell Hardness B
(HRB). Weldments are seldom cold worked after
solution treatment. Hardening is accomplished by
aging the workpiece or weldment in a furnace at a
temperature of 290°C to 400°C (550°F to 750°F) for
about 3 hours. Again, to prevent oxidation, a slightly
reducing atmosphere is preferred. After age hardening,
the workpiece or assembly can be returned to room
temperature in any manner, i.e., furnace cooling, water
quenching, or air quenching. The cooling method is
AWS WELDING HANDBOOK
hardened, will have a hardness of 35 to 40 Rockwell
Hardness C (HRC), depending on thickness.
Other Heat-Treatable Copper Alloys. All beryllium-copper, chromium-copper, and zirconium-copper
alloys can be heat treated in the manner previously
described for beryllium-copper alloy UNS C17200.
Only the temperatures are adjusted to provide optimum
mechanical properties.
FIXTURING
The coefficient of thermal expansion for copper and
copper alloys is about 1.5 times that of steel (refer to
Table 3.2), therefore distortion of copper alloys will be
greater. Appropriate measures for controlling distortion
and warping include clamping thin components to suitable fixtures to position and restrain them, and for
thick sections, applying closely spaced tack welds to
align the joint. The ends of the tack welds should be
tapered to ensure good fusion with the first weld beads.
The root pass of multiple-pass welds should be
rather large to prevent cracking. Fixturing and welding
procedures must be designed to limit restraint of copper
alloys that are prone to hot cracking when highly
restrained.
Backing strips or backing rings are used to control
root penetration (the distance the weld metal extends
into the joint root) and fusion in groove welds. Copper
and copper alloys that have the same or similar chemical composition as the base metal can be used for backing. Removable ceramic backing may also be suitable
for use with copper and copper alloys.
FUSION WELDING OF COPPER
Fusion welding of oxygen-bearing copper is difficult.
The high levels of oxygen and impurities in fire-refined
copper make this material particularly difficult to weld.
Electrolytic tough-pitch copper (UNS C11000) has
somewhat better weldability, but must be welded with
caution. Although preheating and the high heat input
are necessary to counteract the high thermal conductivity of these materials, high heat input parameters lead
to degradation of weld properties. Therefore, the inertgas shielded arc processes are recommended. Solid-state
processes can also be effective for welding these materials.
Oxygen-free copper (UNS C10200) and deoxidized
copper (UNS C12000) should be selected for components to be welded when the best combination of electrical conductivity, mechanical properties, and corrosion
resistance is to be achieved.
Copper is welded with ECu and ERCu filler metals
when the composition of the filler metal is similar to the
CHAPTER 3—COPPER AND COPPER ALLOYS
237
base metal, although other compatible copper filler
metals can be used to obtain the desired properties.
The high thermal conductivity of copper often
requires preheating to achieve complete fusion and adequate joint penetration. Preheating requirements depend
on material thickness, the welding process, and heat
input. Figure 3.9 shows the effects of welding process,
shielding gas, and metal thickness on preheat requirements for welding copper using gas-shielded processes.
Gas Tungsten Arc Welding
Gas tungsten arc welding (GTAW) is best suited for
joining sections of copper up to 3.2 mm (0.125 in.)
thick, but flat-position welding of thicker sections also
can be successfully performed. Pulsed current is helpful
for welding in positions other than flat. (Refer to Figure
3.7 for typical joint designs for GTAW.)
Typical welding conditions for the gas tungsten arc
welding of copper are shown in Table 3.7. (Refer to
Figure 3.10 for illustrations of the joint designs
referenced in Table 3.7).
Shielding Gases. Argon shielding gas is preferred for
the gas tungsten arc welding of copper up to 1.5 mm
(0.06 in.) thick; helium is preferred for welding sections
greater than 1.5 mm (0.06 in.) thick. Compared to
argon, helium produces deeper weld-bead penetration
or permits higher travel speed, or both, at the same
welding current. Figure 3.10 illustrates the differences
in weld-bead penetration in copper when using argon
and helium shielding gases. Helium produces a cleaner,
more fluid weld pool with considerably less risk of
oxide entrapment. Mixtures of argon and helium result
in intermediate welding characteristics. A mixture of
75% helium and 25% argon produces a good balance
between the enhanced weld penetration of helium, and
the easier arc starting and better arc stability of argon.
Welding Technique. Either forehand or backhand
welding can be used for welding copper. Forehand
welding is preferred for all welding positions and
provides a smaller, more uniform bead than that
resulting from backhand welding.
Stringer beads or narrow weave beads should be
used for copper. Wide oscillation of the arc should be
avoided because it exposes each edge of the bead to the
atmosphere. The first bead should penetrate to the root
of the joint and should be sufficiently thick to provide
time for deoxidation of the weld metal and to avoid
cracking of the weld bead.
Welding conditions described in this section should
be used only as a guide for establishing welding
procedures. The high thermal conductivity of copper
precludes recommending welding conditions suitable
238
CHAPTER 3—COPPER AND COPPER ALLOYS
AWS WELDING HANDBOOK
PLATE THICKNESS, mm
4
8
12
16
20
24
1400
1300
700
1200
1100
1000
ON
RG
A
–
ON
AW RG
T
A
G
–
UM
AW
LI
M
E
G
H
–
AW
GM
or
AW
GT
500
400
300
200
900
800
700
600
500
400
PREHEAT TEMPERATURE, °F
PREHEAT TEMPERATURE, °C
600
300
100
200
100
0.125
0.250
0.375
0.5
0.625
0.750
0.875
1
PLATE THICKNESS, in.
Figure 3.9—Effects of Shielded Arc Welding Processes, Shielding Gas,
and Metal Thickness on Preheat Requirements for Welding Copper
all applications. The welding conditions should be
adjusted to produce the desired weld bead shape. Weld
bead shape places a limitation on travel speed. At excessive
speeds, weld beads tend to be highly convex in
shape, causing underfill along the edges and poor fusion
of subsequent weld passes.
Properties of Copper Weld Metal. Typical
mechanical and electrical properties of copper weld
metal are shown in Table 3.8. This data represents
GTAW specimens tested in both the as-welded and
annealed condition.
Gas metal arc welding (GMAW) is a suitable process
for welding copper. A shielding gas mixture of 75%
helium and 25% argon is recommended. Argon is
typically used when welding workpieces up to 6.4
mm
(0.25 in.) thick. The helium-argon mixture is used to
because preheat requirements are lower, joint penetration is better, and filler metal deposition rates are
higher.
Copper electrodes (ERCu) are recommended for the
gas metal arc welding of copper. These electrodes have
the highest conductivity of any copper electrodes and
contain minor alloying elements that improve
weldability. The resulting weld will have lower conductivity than the base metal. Copper-alloy electrodes (copper-silicon and copper-aluminum) can be used to obtain
the desired mechanical properties of the joint if good
electrical or thermal conductivity is not a major requirement. Electrode size will depend on thickness of the
base metal and the joint design.
The filler metal should be deposited by stringer
beads or narrow weave beads using the spray transfer
mode of gas metal arc welding. Wide electrode weaving
can result in oxidation at bead edges. Minimum condi-
AWS WELDING HANDBOOK
CHAPTER 3—COPPER AND COPPER ALLOYS
239
Table 3.7
Typical Conditions for Manual Gas Tungsten Arc Welding of Copper
Metal Thickness,
mm (in.)
Joint
Designa
Shielding
Gas
Tungsten Electrode
Diameter, mm (in.)
Welding Rod
Diameter, mm (in.)
Preheat
Temperature
Welding
Current, Ab
No. of
Passes
0.3–0.8
(0.01–0.03)
1.0–1.8
(0.04–0.07)
2.3–4.8
(0.09–0.19)
6.4
(0.25)
9.6
(0.38)
12.7
(0.5)
16 & up
(0.63 & up)
A
Ar
40–170
1
C
He
100–300
1–2
C
He
250–375
2–3
E
He
300–375
2–3
D
He
350–420
4–6
F
He
—
—
—
—
38°C
(100°F)
93°C
(200°F)
232°C
(450°F)
343°C
(650°F)
399°C min
(750°F min)
1
Ar
—
—
1.6
(0.062)
2.4, 3.2
(0.094, 0.125)
3.2
(0.125)
3.2
(0.125)
3.2
(0.125)
3.2
(0.125)
15–60
B
0.5, 1.0
(0.02, 0.04)
1.0, 1.6
(0.04, 0.062)
2.4
(0.094)
3.2
(0.125)
3.2
(0.125)
3.2, 4.0
(0.125, 0.156)
4.8
(0.188)
400–475
As required
a. See Figure 3.7.
b. Direct current electrode negative (DCEN).
ARGON
1.0 mm
(0.04 in.)
2.0 mm
(0.08 in.)
3.0 mm
(0.12 in.)
3.6 mm
(0.14 in.)
4.6 mm
(0.18 in.)
HELIUM
6.1 mm
(0.24 in.)
4.6 mm
(0.18 in.)
METAL TEMPERATURE
21°C
(70°F)
21°C
(70°F)
93°C
(200°F)
204°C
(400°F)
299°C
(570°F)
399°C
(750°F)
Figure 3.10—Effect of Shielding Gas and Preheat Temperature on
Weld Bead Penetration in Copper when Gas Tungsten Arc Welded
with 300 A dc at a Travel Speed of 3.4 mm/sec (8 in./min)
tions for spray transfer with steady current, copper electrodes, and argon shielding are shown in Table 3.9.
Pulsed current can be used to achieve spray transfer
over a wider range of welding currents.
Several joint designs are suggested for the gas metal
arc welding of copper (refer to Figure 3.8). Typical preheat temperatures and welding conditions are listed in
Table 3.10. This data can be used for guidance in estab-
lishing suitable welding conditions, but conditions for
each application should be substantiated by appropriate
tests. The forehand welding technique should be used in
the flat position. In the vertical position, the progression of welding should be uphill. Using a pulsed current
improves weld bead shape and operability when welding
copper in positions other than flat. Gas metal arc welding of copper should not be done in the overhead position.
240
CHAPTER 3—COPPER AND COPPER ALLOYS
AWS WELDING HANDBOOK
Table 3.8
Typical Properties of Copper Specimens Welded Using Gas Tungsten Arc Welding
Tensile Strength
Test and Conditions
MPa
Impact Strengtha
Elongation,
%
J
ft·lb
Electrical
Conductivity,
% IACS
20–40
20–40
27–54
—
20–40
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
95
83
37
26
Yield Strength
ksi
MPa
ksi
All Weld Metal Test
As-welded
Annealed at 538°C (1000°F)
186–220
186–220
27–32
27–32
As-welded
200–220
29–32
103–138
83–124
15–20
12–18
Transverse Tension Test
69–159
Deposited Metal
Oxygen-free copper
Phosphorous deoxidized copper
Phosphor bronze
Silicon bronze
—
—
—
—
—
—
—
—
—
—
—
—
10–13
Conductivityb
—
—
—
—
a. Charpy keyhole specimens.
b. Copper base metal welded with the given filler metal.
Table 3.9
Approximate Gas Metal Arc Welding Conditions for Spray Transfer
with Copper and Copper Alloy Electrodes and Argon Shielding
Electrode
mm
in.
Minimum*
Welding
Current,
A
0.9
1.1
1.6
0.9
1.1
1.6
0.9
1.1
1.6
1.6
0.035
0.045
0.062
0.035
0.045
0.062
0.035
0.045
0.062
0.062
180
210
310
160
210
280
165
205
270
280
Diameter
Type
ERCu (copper)
ERCuAl-A2 (aluminum bronze)
ERCuSi-A (silicon bronze)
ERCuNi (copper nickel)
Arc
Voltage,
V
mm/s
in./min
kA/mm2
kA/in.2
26
25
26
25
25
26
24
26–27
27–28
26
146
106
63
125
110
78
178
125
80
74
345
250
150
295
260
185
420
295
190
175
0.30
0.21
0.16
0.26
0.21
0.14
0.27
0.20
0.14
0.14
191
134
101
170
134
91
176
131
88
91
Filler Wire Feed
Minimum Current Density
*Direct current electrode positive (DCEP).
Plasma Arc Welding
Shielded Metal Arc Welding
Copper can be welded with the plasma arc welding
(PAW) process using ERCu filler metal. Argon, helium,
or mixtures of the two are used for orifice gas and
shielding gas; the selection depends on the thickness of
the base metal. As with GTAW, arc energy is higher
with helium-rich mixtures. Hydrogen should not be
added to either gas when welding copper.
Copper can be welded using the shielded metal arc
welding (SMAW) process with ECu covered electrodes,
but weld quality is not as good as that obtained with
the gas-shielded welding processes previously described.
Best results with SMAW are obtained when welding
deoxidized copper. The ECu covered electrodes can be
used to weld oxygen-free and tough-pitch coppers, but
AWS WELDING HANDBOOK
CHAPTER 3—COPPER AND COPPER ALLOYS
241
Table 3.10
Typical Conditions for Gas Metal Arc Welding of Various Thicknesses of Copper
Electrode
Metal
Thickness
Joint
Designa
Shielding
Gas
Diameter
Feed
Preheat
Temperature
Welding
Current, Ab
Travel
Speed
Up to 4.8 mm
(up to 0.19 in.)
A
6.4 mm
(0.25 in.)
No. of
Passes
Ar
1.1 mm
(0.045 in.)
76 mm/s–133 mm/s
(180–315 in./min)
38-93°C
(100–200°F)
180–250
6 mm/s–8 mm/s
(14 in./min–20 in./min)
1–2
B
75% He25% Ar
1.6 mm
(0.062 in.)
63 mm/s–89 mm/s
(150–210 in./min)
93°C
(200°F)
250-325
4 mm/s–8 mm/s
(10 in./min–18 in./min)
1–2
9.6 mm
(0.38 in.)
B
75% He25% Ar
1.6 mm
(0.062 in.)
80 mm/s–97 mm/s
(190-230 in./min)
218°C
(425°F)
300-350
2 mm/s–5 mm/s
(6 in./min–12 in./min)
1–3
12.7 mm
(0.50 in.)
C
75% He25% Ar
1.6 mm
(0.062 in.)
89 mm/s–114 mm/s
(210-270 in./min)
316°C
(600°F)
330-400
3 mm/s–6 mm/s
(8 in./min–14 in./min)
2–4
16 mm and up
(0.63 in. and up)
D
75% He25% Ar
1.6 mm
(0.062 in.)
89–114 mm/s
(210–270 in./min)
427°C
(800°F)
330–400
2 mm/s–5 mm/s
(6 in./min–12 in./min)
As
required
16 mm and up
(0.63 in. and up)
D
75% He25% Ar
2.4 mm
(0.094 in.)
63–80 mm/s
(150–190 in./min)
427°C
(800°F)
500–600
3 mm/s–6 mm/s
(8 in./min–14 in./min)
As
required
a. Refer to Figure 3.2.
b. Constant-potential power source; direct current electrode positive (DCEP) using a short arc length that provides steady and quiet operation.
the welded joints will contain porosity and oxide
inclusions.
Copper can be welded with an alloy-covered
electrode, such as ECuSi or ECuSn-A electrodes. These
electrodes are used for the following types of applications:
1. Minor repair of relatively thin copper sections,
2. Fillet-welded joints with limited access, and
3. Welding copper to other metals.
Joint designs should be similar to those used for
GTAW (refer to Figure 3.7). A grooved copper backing
can be used to control the root surface contour.
The size of the electrode should be as large as practical
for the base metal thickness. Welding should be
done with direct current electrode positive (DCEP) of
sufficient amperage to provide good fluidity of the filler
metal. Either a weave or stringer bead technique can
be used to fill the joint. Joints thicker than 3.3 mm
(0.13 in.) should be welded in the flat position, with the
workpieces preheated to a temperature of 260°C (500°F)
or higher.
Oxyfuel Gas Welding
The oxygen-free and deoxidized coppers can be
welded using the oxyfuel gas welding (OFW) process,
but welding travel speed is slower than that of arc welding. For oxyacetylene welding (OAW), ERCu welding
electrodes and appropriate flux are used. To obtain
good fusion, preheat and auxiliary heating are recommended when welding thicknesses greater than 3.3 mm
(0.13 in.).
Type ERCu or ERCuSi filler metal can also be used
for the oxyfuel gas welding of copper, depending on the
desired joint properties. When commercial flux
designed for welding copper alloys is used, the welding
rod and the joint surfaces should be coated with the
flux.
The OFW flame should be neutral when flux is used,
and slightly oxidizing when welding without flux. The
welding tip size should be one to two sizes larger than
the tip used for the same thickness of steel. Typical
welding tip sizes and joint designs for oxyacetylene
welding of copper are shown in Table 3.11.
Backhand welding is generally preferred for the flat
position. The backhand technique can produce thicker
beads with less oxide entrapment than that of beads
produced by forehand welding. Control of the weld
pool is greatly improved when the joint axis is tilted
about 10° to 15° and the direction of welding is uphill.
Long seams should not be tack welded. The initial
root opening should increase along the length of the
joint, with a taper that will close gradually as welding
proceeds along the joint. A general guideline is to
increase the root opening 0.015 units for each unit of
joint length.
Completed weld beads can be cold worked by peening
to relieve welding stresses and increase the weld metal
strength. Peening can be done either while the weld
metal is still warm or after it cools to room temperature.
242
CHAPTER 3—COPPER AND COPPER ALLOYS
AWS WELDING HANDBOOK
Table 3.11
Suggested Joint Designs and Welding Tip Sizes for Oxyacetylene Welding of Copper
Metal Thickness
Root Opening
Welding Tip
Drill Size No.
0
0
55 to 58
—
1.5–2.3
0.06–0.09
55 to 58
—
in.
1.5
0.06
Edge-flange
1.5
0.06
Square-groove
3.3
0.13
Square-groove
2.3–3.3
0.09–0.13
51 to 54
4.8
0.19
60° to 90° single-V-groove
3.3–4.6
0.13–0.18
48 to 50
Auxiliary heating required
6.4
0.25
60° to 90° single-V-groove
3.3–4.6
0.13–0.18
43 to 46
Auxiliary heating required
9.6
0.38
12.7–19.0
0.50–0.75
Joint Design
in.
mm
mm
Remarks
—
60° to 90° single-V-groove
4.6
0.18
38 to 41
Auxiliary heating required
90° double-V-groove
4.6
0.18
38 to 41
Weld both sides simultaneously
in vertical position
Other Processes
The solid-state processes, friction welding (FW) and
cold welding (CW), are effective for welding copper and
copper alloys. High-frequency resistance seam welding
(RSEW-HF) is generally used to weld copper tubing.
WELDING HIGH-ALLOY COPPERS
High-alloy coppers include beryllium copper (UNS
C17000–C17500), cadmium copper (UNS C14300),
chromium copper (UNS C18200), chromium-zirconium
copper (UNS C18150), zirconium copper (UNS C15000),
and nickel-silicon-chromium copper (UNS C18000).
Cadmium copper has good electrical conductivity
and is strengthened by cold working. Beryllium chromium and zirconium copper can be strengthened by a
precipitation-hardening heat treatment, used alone or in
combination with cold working. Nickel-silicon-chromium alloys also are strengthened by precipitation
hardening, used alone or in combination with cold
working.
Welding will soften the HAZ in the precipitationhardened, high-copper alloys by annealing or overaging. The characteristics and condition of each alloy
should be considered when establishing manufacturing
sequences and welding procedures. For maximum properties, beryllium-chromium assemblies and zirconiumcopper assemblies should be welded before either heat
treatment or cold working is applied.
Cadmium Copper and Chromium Copper
Cadmium copper can be joined using the gas
shielded welding processes and also using oxyfuel gas
welding (OFW) and flash welding (FW). The procedures recommended for the shielded arc welding processes and oxyfuel gas welding of copper are good bases
to use for developing welding procedures for cadmiumcopper and chromium-copper alloys. These alloys have
lower electrical and thermal conductivity than pure
copper, and they can be welded at lower preheat temperatures and with lower heat input.
Chromium copper can be welded with the gas
shielded processes and flash welding, but OFW should
not be used because of problems caused by the formation of chromium oxide on weld faces.
Oxyfuel gas welding of cadmium copper requires a
flux that contains sodium fluoride and either fused
borax or boric acid, or both, to dissolve cadmium oxides.
Beryllium Copper
Two types of beryllium copper are available. The
low-beryllium type contains about 0.5% beryllium and
1.5% or 2.5% cobalt and has relatively good electrical
conductivity. The high-beryllium type contains about
2% beryllium and 0.2% cobalt or nickel. It has good
strength in the precipitation-hardened condition but has
low electrical conductivity, about 20% IACS.
High-beryllium copper is more readily welded than
low-beryllium copper. The addition of beryllium to
copper lowers the melting point, increases the fluidity
of the molten metal, and decreases thermal conductivity, all of which contribute to better weldability.
A difficulty common to welding beryllium copper is
the formation of surface oxide. Beryllium forms a tenacious oxide that inhibits wetting and fusion during
welding. Cleanliness of the faying surfaces and surrounding surfaces before and during welding is essential
for good results.
AWS WELDING HANDBOOK
CHAPTER 3—COPPER AND COPPER ALLOYS
Sound welds can be made in the low-beryllium
alloys, but cracking during welding or postweld heat
treatment is often a problem. Low-beryllium copper
can be joined more readily with a filler metal with
higher beryllium content.
When repair welds with high mechanical properties
are required, beryllium-copper components can be
repaired using SMAW with aluminum-bronze electrodes or by GTAW with silicon-bronze filler metal.
Typical conditions used for welding beryllium copper are shown in Table 3.12. This information can be
used as a guide to establishing suitable welding conditions.
Stabilized ac power is preferred for manual GTAW
welding of thin sections of copper (less than 6.4 mm
[0.25 in.]) to take advantage of the surface cleaning
action ac provides. Direct current electrode negative
(DCEN) is recommended for welding heavier sections
and can be used for manual and mechanized GTAW,
provided adequate gas shielding is used to prevent oxidation.
Preheat is not usually required for welding thin sections of 3.3 mm (0.13 in.) and less. Preheat temperatures for alloys with high thermal conductivity should
be those recommended for copper. For the highstrength alloys, preheat temperatures of 149°C to
204°C (300°F to 400°F) are sufficient.
After welding, optimum mechanical properties are
obtained by a solution-annealing heat treatment followed by cold working, if possible, and age hardening,
as the data in Table 3.13 indicate. The characteristics of
243
the weld metal must be considered when planning a
postweld heat treatment if the filler metal composition
is different from that of the base metal.
Components in the precipitation-hardened condition
should not be welded because of the risk of cracking in
the heat-affected zone. Thin sections of copper should
be welded in the solution-annealed condition.
In multiple-pass welding of heavy sections, initial
passes are overaged by the heat of subsequent passes.
Therefore, where multiple-pass welding is required, the
base metal should be in the overaged condition because
it is more stable, metallurgically, in this condition than
in the solution heat-treated condition.
WELDING COPPER-ZINC ALLOYS (BRASS)
Copper-zinc alloys (brass) can be joined by arc welding, oxyfuel gas welding, resistance spot welding, flash
welding, and friction welding processes. The electrical
and thermal conductivity of brass decreases with
increasing zinc content, so the high-zinc brasses require
lower preheat temperatures and lower welding heat
input than low-zinc brasses. Because zinc vaporizes
from molten brass, zinc fumes are a major problem
when welding brasses and are more intense for the
high-zinc brasses. (Refer to the Safe Practices section of
this chapter.) Other alloying elements, such as aluminum and nickel, can slightly increase the tendency for
cracking and increase the formation of oxide. For these
Table 3.12
Typical Conditions for Arc Welding of Beryllium Coppers
GTAW
GMAW
Manual
Variable
Thickness, mm (in.)
Joint design
Preheat temp., °C (°F)
Filler metal diameter, mm (in.)
Automatic
Manual
Alloy C17200
Alloy C17500
Alloy C17200
Alloy C17200
Alloy C17000
3.2 (0.125)
6.4 (0.25)
0.5 (0.020)
2.3 (0.090)
25.4 (1.0)
Ca
Ea
Ba
Ba
Db
21 (70)
149 (300)
21 (70)
21 (70)
149 (300)
3.2 (0.125)
3.2 (0.125)
—
1.6 (0.062)
1.6 (0.062)
Filler metal feed, mm/s (in./min)
—
—
—
—
80–85 (190–200)
Shielding gas
Ar
Ar
Ar
65% Ar-35% He
Ar
Welding power
ACHF
ACHF
DCEN
DCEN
DCEP
Welding current, A
180
225–245
43
150
325–350
Arc voltage, V
—
22–24
12
11.5
29–30
Travel speed, mm/s (in./min)
—
—
11 (27)
8 (20)
—
a. Refer to Figure 3.7.
b. Refer to Figure 3.8.
244
CHAPTER 3—COPPER AND COPPER ALLOYS
AWS WELDING HANDBOOK
Table 3.13
Typical Mechanical Properties of Welded Joints in Beryllium Copper
Tensile Strength
Alloy and Condition*
Yield Strength
MPa
ksi
MPa
ksi
207–228
30–33
C17200 (Cu-2Be)
As-welded
Aged only
Solutioned and aged
414–484
60–70
896–1069
130–155
861–1034
125–150
1034–1207
150–175
1000–1172
145–170
C17500 (Cu-2.5 Co-0.5Be)
As-welded
345–379
50–55
207–310
30–45
Aged only
552–655
80–95
448–586
65–85
Solutioned and aged
689–758
100–110
517–586
75–85
*Welded in the solution heat-treated condition.
reasons, low-zinc brasses have good weldability, highzinc brasses have only fair weldability, and leaded alpha
brasses (64% to 95% copper) are not suitable for welding. Lead makes these copper-zinc alloys very sensitive
to hot cracking. The low-leaded alpha-beta brasses are
weldable under conditions of low restraint, provided
that low weld strength can be accepted.
Gas Tungsten Arc Welding, Brass
The brasses are commonly joined by gas tungsten arc
welding (GTAW) in sections that are up to 9.7 mm
(0.38 in.) thick. Thin brass sheets can be welded without the addition of filler metal, but filler metal is recommended when welding sections thicker than 1.6 mm
(0.062 in.). Phosphor bronze (ERCuSn-A) filler metal
provides a good color match with some brasses, but silicon bronze (ERCuSi-A) filler metals reduce zinc fuming.
Aluminum bronze (ERCuAl-A2) filler metal can be used
to provide good joint strength for high-zinc brasses, but
aluminum bronze filler metal is not effective in controlling zinc fuming, and welds tend to be porous.
V-groove welds with a groove angle of 75° to 90°
should be used to ensure good joint penetration for
thicknesses greater than 4.8 mm (0.188 in.). A preheat
temperature of 93°C to 316°C (200°F to 600°F) should
be used on heavier sections. The preheat temperature
can be lowered for the high-zinc brasses.
Welding procedures can be designed to minimize
zinc fuming by directing the welding arc onto the filler
rod or the weld pool rather than on the base metal. The
base metal is heated to fusion temperature by conduction from the weld pool rather than by direct impingement of the arc.
Gas Metal Arc Welding, Brass
Gas metal arc welding (GMAW) is used primarily to
join relatively thick sections of brass and is suitable for
sections thicker than 3.3 mm (0.13 in.). Zinc fuming is
more severe with GMAW than with GTAW. Argon
shielding is normally used, but helium-argon mixtures
can provide higher heat input. Silicon-bronze (ERCuSiA), phosphor-bronze (ERCuSn-A), or aluminum-bronze
(ERCuAl-A2) bare electrodes are recommended. The
phosphor-bronze electrode will produce weld metal
that has a good color match with most brass, but the
silicon-bronze electrode has better fluidity. The aluminum-bronze electrode is best for welding high-strength
brasses and will produce weldments with strength
equivalent to that of the base metal. V-groove weld
joints with a 60° to 70° groove angle or U-groove joints
are recommended when using aluminum bronze filler
metal.
A preheat in the range of 93°C to 316°C (200°F to
600°F) is recommended for the low-zinc brasses
because of the relatively high thermal conductivity of
these metals. Preheat is not necessary for the gas metal
arc welding of high-zinc brasses, but can be used to
reduce the required welding current, and thus reduce
zinc fuming. During welding, the arc should be directed
on the weld pool to minimize fuming.
Shielded Metal Arc Welding, Brass
Brasses can be welded with the shielded metal arc
welding (SMAW) process using the following covered
electrodes: phosphor bronze (ECuSn-A or ECuSn-C),
silicon bronze (ECuSi), or aluminum bronze (ECuAl-
AWS WELDING HANDBOOK
A2). The selection criteria for covered electrodes are
similar to those previously described for bare electrodes
used with gas metal arc welding (GMAW).
The weldability of brass is not as good with SMAW as
with GMAW, and relatively large groove angles are
needed to achieve good joint penetration and to avoid
slag entrapment. For best results, welding should be done
in the flat position, using a backing of copper or brass.
The preheat and interpass temperature for the low
brasses should be in the range of 204°C to 260°C
(400°F to 500°F), and in the range of 260°C to 371°C
(500°F to 700°F) for the high brasses. Low preheat temperature will result in better mechanical properties of
the weld joint when using phosphor-bronze electrodes.
To deposit stringer beads in the joint, high welding
speed and a welding current in the high area of the recommended range for the electrode should be used. The
arc should be directed on the weld pool to minimize
zinc fuming.
Oxyfuel Gas Welding, Brass
The oxyfuel gas welding (OFW) procedures that are
used for copper are also suitable for the brasses. The
low-alloy brasses are readily joined by OFW; this process is particularly suited for pipe welding because it
can be performed in all welding positions. A siliconbronze (ERCuSi-A) welding rod or one of the brass
welding rods (RBCuZn-A, RBCuZn-B, or RBCuZn-C)
can be used.8, 9 Brass welding rods that contain 38% to
41% zinc develop a significant proportion of the hard,
strong beta phase in the weld metal. This beta phase is
soft and ductile at elevated temperatures, and cracking
is not a problem.
When oxyfuel gas welding is used 0with a neutral or
slightly oxidizing flame, very little zinc oxide appears
on the molten weld metal surfaces. When a strongly
oxidizing flame is used, an oxide film forms on the molten weld metal surface that suppresses evaporation of
zinc, provided that the weld metal is not overheated.
For the oxyfuel gas welding of high-alloy brasses,
RBCuZn-B or RBCuZn-C welding rods are used. These
low-fuming rods have compositions similar to the high
brasses. A flux of AWS classification FB3-C, FB3-D, or
FB3-K is required, and the torch flame should be adjusted
to slightly oxidizing to control fuming.10 Preheating and
an auxiliary heat source may also be necessary.
8. American Welding Society, 2011, Specification for Filler Metals
for Brazing and Braze Welding, A5.8M/A5.8:2011, Miami: American
Welding Society.
9. American Welding Society, 2007, Specification for Copper and
Copper-Alloy Bare Welding Rods and Electrodes, A5.7/A5.7M:2007,
Miami: American Welding Society.
10. American Welding Society, 2012, Specification for Fluxes for
Brazing and Braze Welding, A5.31M/A5.31:2012, Miami: American
Welding Society.
CHAPTER 3—COPPER AND COPPER ALLOYS
245
COPPER-NICKEL-ZINC ALLOYS (NICKEL
SILVER)
Nickel-silver alloys are seldom welded, although
welding of these alloys is similar to welding brass of
comparable zinc content. Nickel silvers are frequently
used in decorative applications in which color match is
important. Zinc-free filler metals that give a good color
match for the gas-shielded arc welding processes are not
available. Gas tungsten arc welding (GTAW) used without the addition of filler metal is usually restricted to
welding thicknesses of 2.4 mm (0.094 in.) or less.
Square-groove joints, butt joints, lap joints, or edge
joints should be used.
Oxyfuel gas welding can be performed using
RBCuZn-D welding rods with a slightly oxidizing flame
for a wide range of thicknesses. An AWS classification
FB3-D brazing flux should be applied to both the joint
area and the welding rod before and during welding.
If SMAW is to be used, manganese-bronze or copper-nickel filler metal will result in a close color match.
Care must be exercised to prevent undercutting,
because the melting points of these alloys are appreciably higher than those of the nickel silvers.
Annealing is recommended prior to welding severely
restrained cold-worked material. Postweld stress relief
is suggested for components subjected to corrosive environments. Preheat is recommended to avoid cracking of
single-phase alloys, which have poor ductility at elevated-temperatures and are susceptible to hot cracking.
Resistance welding is practical because the conductivity of nickel silver is among the lowest of all copper
alloys. Welding machines with low inertia heads and
electronic controls provide best results. Power requirements are usually 125% to 150% less than those used
for comparable thicknesses of steel. The stud welding
(SW) process can be used successfully to join nickel silvers.
COPPER-TIN ALLOYS (PHOSPHOR
BRONZE)
The copper-tin alloys (phosphor bronze) have rather
wide solidification ranges, solidifying with large, weak
dendritic grain structures. Welding procedures are
designed to prevent the tendency of weld cracking. Hot
peening of each layer of multiple-pass welds will reduce
welding stresses and the likelihood of cracking. Welding of leaded copper-tin alloys is not recommended;
however, some leaded alloys can be welded if care is
exercised. Weldability decreases with increasing lead
content. Shielded metal arc welding (SMAW) generally
produces better results on leaded alloys than gas metal
arc welding (GMAW).
246
CHAPTER 3—COPPER AND COPPER ALLOYS
AWS WELDING HANDBOOK
Joint Preparation
A single-V-groove weld should be used to join copper-tin alloys in the thickness range of 4 mm to 13 mm
(0.15 in. to 0.50 in.). The groove angle should be 60° to
70° for GMAW and 90° for SMAW. For greater thicknesses, a single-U-groove weld or double-U-groove weld
with a 6.4 mm (0.25 in.) groove radius and a 70°
groove angle is recommended for good access and
fusion. A square-groove weld can be used for thicknesses less than 3.8 mm (0.15 in.).
Preheat and Postheat, Phosphor Bronze
Phosphor-bronze weld metal tends to flow sluggishly
because it has a wide melting range. Preheating to
177°C to 204°C (350°F to 400°F) and maintaining this
interpass temperature improves metal fluidity when
welding thick sections. The maximum interpass temperature should not exceed 204°C (400°F) to avoid hot
cracking. Preheating is not essential when using
GMAW spray transfer. For maximum weld ductility
and resistance to stress corrosion, postweld heat treatment at 482°C (900°F) is recommended, followed by
rapid cooling to room temperature.
Gas Metal Arc Welding, Phosphor Bronze
Gas metal arc welding (GMAW) is recommended for
joining large phosphor-bronze fabrications and thick
sections using direct current electrode positive (DCEP),
with ERCuSn-A filler metal and argon shielding.
Table 3.14 shows suggested GMAW parameters that
can be used to establish welding procedures for phosphor bronzes. The weld pool should be kept small by
using stringer beads at rather high travel speed. Hot
peening of each layer will reduce welding stresses and
the likelihood of cracking.
Gas Tungsten Arc Welding, Phosphor
Bronze
Gas tungsten arc welding (GTAW) is used primarily
for repair of castings and joining of phosphor-bronze
sheet with ERCuSn-A filler metal. As with GMAW, hot
peening of each layer of weld metal is beneficial. Either
stabilized alternating current or direct current electrode
negative (DCEN) can be used with helium or argon
shielding.
Shielded Metal Arc Welding, Phosphor
Bronze
The shielded metal arc welding (SMAW) process can
be used with phosphor-bronze covered electrodes
(ECuSn-A or ECuSn-C) to weld bronzes of similar
chemical composition. Filler metal should be deposited
as stringer beads, using DCEP to obtain the best
mechanical properties. Postweld annealing at 482°C
(900°F) is not always necessary, but it is recommended
for maximum ductility, particularly if the welded
assembly is to be cold worked. Moisture, both on the
workpiece and in the electrode coverings, must be
strictly avoided. Baking the electrodes at 121°C to
149°C (250°F to 300°F) immediately before use will
Table 3.14
Parameters for Gas Metal Arc Welding of Phosphor Bronze
Joint Design
Metal Thickness
mm
in.
1.5
0.06
Electrode Diametera
Root Opening
Groove Type
Square
Weldingb Current, Arc Voltage,
mm
in.
mm
in.
V
A
1.3
0.05
0.8
0.030
25–26
130–140
3.3
0.13
Square
2.3
0.09
0.9
0.035
26–27
140–160
6.4
0.25
V-groove
1.5
0.06
1.1
0.045
27–28
165–185
12.7
0.50
V-groove
2.3
0.09
1.6
0.062
29–30
315–335
19.0
0.75
Note c
0–2.3
0–0.09
2.0
0.078
31–32
365–385
25.4
1.00
Note c
0–2.3
0–0.09
2.4
0.094
33–34
440–460
a. ERCuSn-A phosphor-bronze electrodes and argon shielding.
b. Direct current electrode positive (DCEP).
c. Double-V-groove or double-U-groove.
AWS WELDING HANDBOOK
reduce the moisture content in the covering to an
acceptable level.
Oxyfuel Gas Welding, Phosphor Bronze
Oxyfuel gas welding (OFW) is not recommended for
joining the phosphor bronzes. The wide heat-affected
zone and the slow cooling rate can result in hot cracking because phosphor bronzes are hot short. In an
emergency, or in the event that arc welding equipment
is not available, OFW with ERCuSn-A welding rods
can be used. If a color match is not essential, braze
welding can be done with an OFW torch and RBCuZn-C
welding rod. A commercial brazing flux and neutral
flame should be used.
CHAPTER 3—COPPER AND COPPER ALLOYS
247
Table 3.15
Suggested Filler Metals
for Arc Welding of Aluminum Bronzes*
UNS No.
SMAW
GTAW or GMAW
C61300
ECuAl-A2
ERCuAl-A2
ECuAl-B
ERCuAl-A2
ECuAl-B
ERCuAl-A3
ECuNiAl
ERCuNiAl
ECuMnNiAl
ERCuMnNiAl
C61400
C61800
C62300
C61900
C62400
C62200
C62500
C63000
C63200
WELDING ALUMINUM BRONZE (COPPERALUMINUM ALLOYS)
Aluminum bronze (copper-aluminum) alloys are
used in many applications, but cracking and oxidation
are common occurrences. Welds in these alloys require
carefully developed parameters to avoid these problems.
Weldability
Single-phase aluminum bronzes containing less than
7% aluminum are hot-short and difficult to weld.
Weldments in these alloys can crack in the heat-affected
zone (HAZ). Single-phase alloys containing more than
8% aluminum and two-phase alloys are considered
weldable when using welding procedures that are
designed to avoid cracking.
The UNS C61300 and C61400 alloys (7% aluminum) are frequently selected for use in heat exchangers,
piping, and vessels. Alloy UNS C61300 is often preferred because of good weldability. Both cast and
wrought alloys with higher aluminum content can be
joined by arc welding. Fluxes do not adequately remove
aluminum oxide from the weld joint, which precludes
the use of oxyfuel gas welding for these alloys.
Filler Metals, Aluminum Bronze
Welding electrodes and filler metals recommended
for joining the weldable aluminum bronzes are shown
in Table 3.15. Typical mechanical properties of weld
metal deposited by arc welding are shown in Table
3.16. Weld metal deposited with GMAW is slightly
stronger and harder than that deposited using SMAW
with covered electrodes. This is attributed to the higher
welding speeds and better shielding typical of GMAW.
C63300
*Also see AWS A5.6/A5.6M:2008, Specification for Copper and CopperAlloy Electrodes for Shielded Metal Arc Welding, and AWS A5.7/
A5.7M:2007, Specification for Copper and Copper-Alloy Bare Welding Rods
and Electrodes.
Joint Design, Aluminum Bronze
For section thicknesses up to and including 3.3 mm
(0.13 in.), square-groove welds are used with a root
opening of up to 75% of the workpiece thickness. For
thicknesses of 3.8 mm to 19 mm (0.15 in. to 0.75 in.), a
single-V-groove weld is used. The groove angle should
be 60° to 70° for GTAW and GMAW, and 90° for
SMAW. A double-V-groove or double-U-groove weld
should be used for section thicknesses greater than
19 mm (0.75 in.). U-groove joints should have a 6.4 mm
(0.25 in.) groove radius.
Preheat
Preheat is often unnecessary when welding the aluminum bronzes. The preheat and interpass temperatures should not exceed 149°C (300°F) for alloys with
less than 10% aluminum, including the nickel-aluminum bronzes. Weldments should be air cooled to room
temperature.
When the aluminum content is from 10% to 13%, a
preheat of 149°C (300°F) and interpass temperature of
about 260°C (500°F) is recommended for thick sections. Rapid air cooling of the weldment is necessary.
Gas Metal Arc Welding, Aluminum Bronze
Gas metal arc welding (GMAW) is suitable for aluminum bronze sections of 4.6 mm (0.18 in.) and
`
248
CHAPTER 3—COPPER AND COPPER ALLOYS
AWS WELDING HANDBOOK
Table 3.16
Typical Mechanical Properties of Aluminum-Bronze Weld Metal
Yield Strengthb
Tensile Strength
Electrodea
MPa
ksi
545
621
717
758
79
90
104
110
MPa
ksi
% Elongation in
50.8 mm (2 in.)
Brinell Hardness,
HBc
35
45
59
67
28
18
22
27
160
207
196
217
35
47
58
56
27
15
25
27
140
177
187
185
Gas Metal Arc Welding
ERCuAl-A2
ERCuAl-A3
ERCuNiAl
ERCuMnNiAl
241
310
407
462
Shielded Metal Arc Welding
ECuAl-A2
ECuAl-B
ECuNiAl
ECuMnNiAl
531
614
683
655
77
89
99
95
241
324
400
386
a. Refer to specifications AWS A5.6/A5.6M:2008 and AWS A5.7/A5.7M:2007 (see Table 3.15 footnote).
b. 0.5% offset.
c. 3000 kg load.
thicker. Argon shielding is used for most joining and
surfacing applications, although a 75% argon-25%
helium mixture is helpful when welding thick sections
requiring increased welding heat and complete penetration. To maintain proper gas coverage, the welding
torch should be tilted 35° to 45° in the forehand direction of travel with an electrode extension of 9.6 mm to
13 mm (0.38 in. to 0.50 in.). When welding in positions
other than the flat position, a pulsed-current power
source or globular type of metal transfer is used. Table
3.17 shows suggested welding parameters for various
electrode sizes. (Refer to Table 3.9 for minimum welding conditions for GMAW spray transfer with ERCuAlA2 electrodes.)
Gas Tungsten Arc Welding, Aluminum
Bronze
Gas tungsten arc welding (GTAW) is recommended
for critical applications, regardless of section thickness,
using either stabilized ac or dc. Alternating current with
argon shielding produces an arc cleaning action during
welding; this removes oxides from the weld interface.
For better penetration or higher travel speed, DCEN
should be used with helium, but also can be used with
argon or a mixture of argon and helium. Preheat is used
only for thick sections welded with GTAW.
Shielded Metal Arc Welding, Aluminum
Bronze
COPPER-SILICON ALLOYS (SILICON
BRONZE)
Shielded metal arc welding (SMAW) of aluminum
bronze is done with covered electrodes (refer to Table
3.15). Direct current electrode positive should be used
with these electrodes. (Refer to Table 3.17 for typical
welding current ranges for aluminum bronze covered
electrodes.) It is recommended that a short arc length
and stringer or weave beads be used. To avoid inclusions, each bead must be thoroughly cleaned of slag
before the next bead is applied. The SMAW process
should be used only when it is inconvenient or uneconomical to use GMAW, because SMAW welding speeds
are significantly lower.
The silicon bronzes are readily weldable. Characteristics of these bronzes that contribute to weldability are
low thermal conductivity, good deoxidation of the weld
metal by the silicon, and the protection afforded by the
resulting slag. Silicon-bronze weld metal has good fluidity, but the molten slag is viscous. Silicon bronzes have
a relatively narrow hot-short temperature range just
below the solidus and must be rapidly cooled through
this critical range to avoid weld cracking.
Heat loss to the surrounding base metal is low, and
high welding speed can be used. Preheat is unnecessary;
interpass temperature should not exceed 93°C (200°F).
AWS WELDING HANDBOOK
CHAPTER 3—COPPER AND COPPER ALLOYS
249
Table 3.17
Typical Operating Parameters for the Arc Welding of Aluminum Bronze
Electrode Size
Gas Metal Arc Welding
in.
Arc Voltage, V
Welding Current, A*
Shielded Metal Arc
Welding Current, A*
0.8
0.030
25–26
130–140
—
0.9
0.035
26–27
140–160
—
mm
1.1
0.045
27–28
165–185
—
1.6
0.188
29–30
315–335
—
2.0
0.078
31–32
365–385
50–70
2.4
0.094
33–34
440–460
60–80
3.2
0.125
—
—
100–120
4.0
0.156
—
—
130–150
4.8
0.062
—
—
170–190
6.4
0.250
—
—
235–255
*Direct current electrode positive (DCEP).
For butt joints, the groove angle of V-groove welds
should be 60° or more. Square-groove welds can be
used to join sections up to 3.3 mm (0.13 in.) thick, with
or without filler metal. Copper backing can be used to
control melt-through.
Gas Tungsten Arc Welding, Silicon Bronze
The silicon bronzes are readily welded in all positions using the GTAW process with ERCuSi-A welding
rods. Aluminum bronze welding rod ERCuAl-A2 can
also be used. Welding is performed with dc using argon
or helium shielding. Welding with ac using argon
shielding has the advantage of arc cleaning action. Typical welding conditions for the gas tungsten arc welding
of silicon bronzes in thicknesses of 1.5 mm to 12.7 mm
(0.06 in. to 0.50 in.) are shown in Table 3.18.
Gas Metal Arc Welding, Silicon Bronze
Gas metal arc welding (GMAW) is used to join sections of silicon bronze that are thicker than 6.4 mm
(0.25 in.). Electrodes ERCuSi-A, argon shielding, and
relatively high travel speeds are used with this process.
When making multiple-pass welds, oxide should be
removed by wire brushing between passes.
Typical welding conditions for the gas metal arc
welding of butt joints are shown in Table 3.19. (Refer to
Table 3.9 for a list of welding conditions necessary for
gas metal arc spray transfer with ERCuSi-A electrodes.)
Table 3.18
Typical Welding Rods and Welding Currents for Gas Tungsten Arc Welding of Silicon Bronze
Thickness
Welding Rod Diameter
mm
in.
1.5
0.06
1.6
0.062
100–130
3.3
0.13
2.4
0.094
130–160
4.8
0.19
3.2
0.125
150–225
6.4
0.25
3.2, 4.8
0.125, 0.188
150–300
12.7
0.50
3.2, 4.8
0.125, 0.188
250–325
*Direct current electrode negative (DCEN) with argon shielding in the flat position.
in.
Welding Current,*
A
mm
0.25
0.25
0.38
0.38
0.38
0.38
0.38
0.50
0.50
0.50
0.50
6.4
6.4
6.4
9.6
9.6
9.6
9.6
9.6
12.7
12.7
12.7
12.7
60° double-V
60° single-V
60° single-V
60° single-V
60° double-V
60° single-V
60° single-V
60° single-V
60° single-V
60° single-V
Square
Square
Groove Type
1.5
3.3
1.5
1.5
1.5
3.3
3.3
1.5
1.5
—
—
—
mm
0.06
0.13
0.06
0.06
0.06
0.13
0.13
0.06
0.06
—
—
—
in.
Root Face
1. Direct current electrode positive (DCEP) and argon shielding.
2. 1.6 mm (0.062 in.) diameter ERCuSi-A electrode.
in.
0.25
mm
Thickness
0
0
0
0
0
0
0
0
0
0
3.3
1.5
mm
0
0
0
0
0
0
0
0
0
0
0.13
0.06
in.
Root Opening
310
2
310
3
310
310
2
1
310
320
1
2
315
3
320
315
2
1
315
1
310
310
1
2
310
310
1
300
3
2
300
300
1
300
2
2
300
300
300
305
300
Welding
Current,1 A
1
1
1
1
1
Pass
No.
26–28
26–28
26
26
26
21
21
21
21
21
26
26
26
26
26
26
26
26
26
26
26
21
26
Arc
Voltage, V
Table 3.19
Typical Conditions for Gas Metal Arc Welding of Silicon Bronze
91
91
91
91
91
129
129
129
129
129
91
91
91
91
91
91
91
91
91
91
91
129
91
mm
215
215
215
215
215
305
305
305
305
305
215
215
215
215
215
215
215
215
215
215
215
305
215
in./min
Electrode Feed 2
5
5
8
5
8
5
5
5
5
5
9
8
7
10
15
7
6
8
9
4
5
6
6
mm/s
13
12
18
12
18
7
13
12
13
12
21
18
16
24
36
16
15
18
21
10
13
15
15
in./min
Travel Speed
250 CHAPTER 3—COPPER AND COPPER ALLOYS
AWS WELDING HANDBOOK
AWS WELDING HANDBOOK
Shielded Metal Arc Welding, Silicon
Bronze
Silicon bronzes can be welded using the shielded
metal arc welding (SMAW) process with ECuAl-A2 or
ECuSi covered electrodes. Square-groove welds are suitable for thicknesses up to 4 mm (0.156 in.); single- or
double-V-groove welds are used for welding thicker
sections.
Welding in the flat position is preferred, but ECuSi
electrodes can be used to weld in the vertical and overhead positions. Preheat is not needed, and the interpass
temperature should not exceed 93°C (200°F). Stringer
beads should be deposited with a welding current near
the middle of the manufacturer’s recommended range
for the electrode size used. A short arc length should be
used, and travel speed should be adjusted to produce a
small weld pool.
Oxyfuel Gas Welding, Silicon Bronze
Oxyfuel gas welding (OFW) should be used to weld
silicon bronze only when arc welding equipment is not
available. If the process is used, welding can be done
with ERCuSi-A welding rod and a suitable flux. A
slightly oxidizing flame should be used. Fixturing
should not unduly restrict movement of the workpieces
during welding, and welding should be performed rapidly. Either forehand or backhand welding can be used;
forehand is preferred for thin sections.
WELDING COPPER-NICKEL ALLOYS
Copper-nickel alloys are readily welded with gas
shielded arc welding processes: shielded metal arc welding (SMAW), gas metal arc welding, (GMAW), gas
tungsten arc welding, (GTAW) submerged arc welding
(SAW), and also the oxyfuel gas welding (OFW) process. Preheat is not required and the interpass temperature should not exceed 177°C (350°F). Surfaces to be
welded should be clean, free of oxides and other contaminants, including sulfur, which can cause intergranular cracking in the HAZ. Recommended filler metals
for welding all grades of copper-nickel alloys are 70Cu30Ni (ERCuNi and ECuNi). If a color match is
required, filler metal of matching composition should
be used.
Gas Tungsten Arc Welding, Copper Nickel
Copper-nickel alloys can be welded in all positions
using the gas tungsten arc welding (GTAW) process.
Direct current electrode negative (DCEN) is recommended, although ac is used for automatic welding if
CHAPTER 3—COPPER AND COPPER ALLOYS
251
arc length is accurately controlled. Manual welding is
usually used to join sheet and plate workpieces up to
6.4 mm (0.25 in.) thick and for tube and pipe. Thicker
sections can be welded with GTAW, but GMAW would
reduce heat input and would be more economical.
Gas tungsten arc welding produces high-quality welds
that meet the stringent acceptance requirements of radiographic testing. Multiple-pass GTAW welds are best
when deposited with a stringer-bead technique with an
arc length of 3.2 mm to 4.7 mm (0.125 in. to 0.188 in.).
Argon or helium can be used for shielding gas, but
argon is generally used to provide improved arc control.
Weld quality and soundness depend on careful attention to arc length and the addition of filler metal. Filler
metal ERCuNi contains titanium, which deoxidizes the
weld and avoids porosity. Autogenous welds or welds
without sufficient filler metal addition may contain
porosity.
Autogenous welds are possible in copper-nickel sheet
up to 1.5 mm (0.06 in.) thick, although weld porosity
can be a problem in the absence of deoxidation from
the filler metal. Close control of arc length is recommended to minimize porosity.
Gas Metal Arc Welding, Copper Nickel
Copper-nickel alloys can be welded with the gas
metal arc welding (GMAW) process using direct current electrode positive (DCEP) with either pulsed spray
transfer or short-circuit transfer. Welding conditions
are shown in Table 3.20. Best results are obtained with
the pulsed spray transfer mode when welding sections
that are 6.4 mm (0.25 in.) thick and greater, using
either steady or pulsed current. Refer to Table 3.9 for
welding conditions for steady current GMAW spray
transfer with a 1.6 mm (0.062 in.) diameter ERCuNi
electrode. Pulsed current is advantageous when joining
thin sections or when welding in positions other than
the flat position.
Although argon is the recommended shielding gas
for most applications, the use of argon-helium mixtures
will result in increased penetration in thick sections.
Proper joint design is important to obtaining complete fusion; V-groove and U-groove joints are recommended for GMAW. A typical V-groove has a 75°
groove angle with a 1.6 mm (0.062 in.) root face and
root opening. A single-V-groove design is satisfactory
for section thicknesses from 7.1 mm to 12.7 mm (0.28
in. to 0.50 in.); for thicknesses greater than 12.7 mm
(0.50 in.), a double-V-groove or U-groove is recommended to reduce distortion. Copper or copper-alloy
backing, or ceramic backing tape can be used with single-V-groove welds to control root surface contour.
Care must be exercised to prevent gas entrapment in the
root pass if weld quality that passes radiographic examination is required.
252
CHAPTER 3—COPPER AND COPPER ALLOYS
AWS WELDING HANDBOOK
Table 3.20
Representative Conditions for Gas Metal Arc Welding of Copper-Nickel Alloy Plate
Electrode Feeda
Thickness
mm
6.4
9.6
12.7
19.0
25.4
over 25.4
in.
0.25
0.38
0.50
0.75
1.0
over 1.0
mm/s
in./min
Arc Voltage,
V
Welding Current,b
A
76–93
85–102
93–102
93–102
93–102
102–110
180–220
200–240
220–240
220–240
220–240
240–260
22–28
22–28
22–28
24–28
26–28
26–28
270–330
300–360
350–400
350–400
350–400
370–420
a. ERCuNi electrode, 1.6 mm (0.062 in.) diameter.
b. Direct current electrode positive (DCEP) and argon shielding.
Shielded Metal Arc Welding, Copper
Nickel
Copper-nickel alloys can be welded with the shielded
metal arc welding (SMAW) process using ECuNi covered electrodes. The electrode diameter for a particular
application should be one size smaller than a comparable steel electrode for a similar steel application.
Copper-nickel weld metal is not as fluid as carbonsteel weld metal. Careful electrode manipulation is
required to produce a good bead contour, and it is
essential to maintain a short arc length. A weave bead is
preferred, with the width of the weave not exceeding
three times the diameter of the electrode core. The
stringer-bead technique can be used for deep-groove
welds. Slag must be thoroughly removed from each
bead before depositing the next bead.
Typical joint designs and welding conditions for
shielded metal arc welding of 6.4 mm (0.25 in.) thick
plate are shown in Table 3.21. Square-groove joints
with a root opening about one half the thickness of the
workpiece can be used on thicknesses of less than 3.2
mm (0.125 in.). For thicker workpieces, V-groove and
U-groove joint designs similar to those recommended
for GMAW should be used.
Oxyfuel Gas Welding, Copper Nickel
Copper-nickel alloys can be welded using oxyfuel gas
welding (OFW), but the use of this process should be
Table 3.21
Typical Conditions for Shielded Metal Arc Welding of
6.4 mm (0.250 in.) Thick, 90% Copper-10% Nickel Alloy Platea
Joint Design
Root Opening
Groove Type
Groove Angle,
Degrees
mm
in.
Flat
Verticalc
Verticalc
Horizontal
Square
Double-V
Fillet
Single-V
—
75–80
80
75–80
3.3
2.3–3.3
0
1.5–3.3
0.13
0.09–0.13
0
0.06–0.13
Flat and overhead
Single-V
75–80
2.3–3.3
0.09–0.13
Welding Position
a.
b.
c.
d.
e.
ECuNi covered electrodes.
Direct current electrode positive (DCEP).
Direction of welding is up.
Backing weld pass. Back gouge before welding the other side (Pass 2).
Back gouge the root of the joint before completing the back weld (Pass 2).
Electrode Size
Weld
Pass
mm
in.
Weldingb
Current, A
1, 2
1, 2
1
d1d
2
e1 e
2
3.2
2.4
2.4
2.4
3.2
3.2
2.4
0.125
0.094
0.094
0.094
0.125
0.125
0.094
115–120
85–90
85
100
100
110–115
95–100
AWS WELDING HANDBOOK
limited to situations in which arc welding equipment is
not available. If OFW is to be used, it should be done
with ERCuNi welding rods and with a soft and slightly
reducing flame. An oxidizing flame will form a cuprous
oxide that will dissolve in the molten metal, reduce corrosion resistance, and cause embrittlement. Preheat is
not recommended. The liberal use of a flux made especially for nickel or copper-nickel alloys is necessary to
protect the welding rod and base metal from oxidation.
Submerged Arc Welding, Copper Nickel
Copper-nickel alloys can be welded with the submerged arc welding (SAW) process. Section thicknesses
greater than 12.7 mm (0.50 in.) are practical; V-groove
and U-groove joint designs similar to those used in
GMAW are satisfactory. Commercially available fluxes
designed for welding copper nickel should be used.
Welding conditions, which vary according to the flux
used, are provided by the flux manufacturer. Careful
attention to bead layer sequence is essential when multiple-pass welds are deposited in a deep groove to ensure
complete fusion while maintaining a flat bead contour.
Welds that pass radiographic testing for quality can be
obtained when SAW is performed correctly.
BRAZING
Brazing is an excellent process for joining copper and
copper alloys. Surface oxides are easily fluxed during
brazing (except refractory oxides on aluminum bronzes
that contain more than 8% aluminum, which require
special techniques). When brazing is selected as the
joining process, the important considerations are brazing temperature, type of loading, joint strength, galvanic corrosion, and interaction between the base and
filler metals at the service temperature.
All of the common brazing processes can be used,
except in special cases, such as resistance or induction
brazing of copper and copper alloys that have high electrical conductivity.11, 12
Lap joints and butt joints can be brazed. The joint
clearance must provide for capillary flow of the selected
brazing filler metal throughout the joint at brazing temperature, and the thermal expansion characteristics of
the alloy must be considered. A joint clearance of 0.025
11. American Welding Society, 2004, Welding Handbook, 9th ed.,
Vol. 2, Miami: American Welding Society.
12. American Welding Society, 2007, Brazing Handbook, 5th ed.,
475–476, Miami: American Welding Society.
CHAPTER 3—COPPER AND COPPER ALLOYS
253
mm to 0.13 mm (0.001 in. to 0.005 in.) will develop the
maximum joint strength and soundness. Larger joint
clearances can be used if reduction in joint strength is
acceptable. When designing a brazed joint for a specific
application, the properties and compatibility of the base
metal-filler metal combination must be properly evaluated, with consideration for the environment in which
the brazed joint will operate.
For electrical conductivity applications, brazing filler
metals generally have low electrical conductivity compared to copper; however, when properly designed, a
brazed joint will not add appreciable resistance to the
circuit. For example, silver filler metal has little effect
on the resistance in properly fitted braze joints with a
joint clearance of 0.08 mm (0.003 in.).
A guide to brazing copper and copper alloys is presented in Table 3.22, which shows filler metals, brazing
atmospheres, fluxes, and recommendations for brazing
various copper materials.
BRAZING FILLER METALS
All of the silver (BAg), copper-phosphorus (BCuP),
gold (BAu), and copper-zinc (RBCuZn) filler metals are
suitable for brazing copper, provided that the liquidus
temperature is sufficiently lower than the melting range
of the base metal.13 The brazing filler metals commonly
used for copper and copper alloys, composition by
weight percent, and brazing temperature ranges are
listed in Table 3.23.
All BAg filler metals can be used with any copper or
copper alloy. The BAu filler metals are used for electronic applications where the vapor pressure of the
brazing filler metal is important. The BCuP filler metals
can be used to braze most copper alloys, including some
copper-nickel alloys containing less than 10% nickel.
Any copper-nickel alloy should be evaluated by an
appropriate brazing test because of the possibility of
creating brittle joints. No flux is required to braze copper with BCuP alloys. Beryllium copper should not be
brazed with a BCuP alloy because it will result in
porous joints with low strength.
When corrosion resistance is not specified, the
RBCuZn filler metals can be used to join the coppers,
copper-nickel, copper-silicon, and copper-tin alloys.
The RBCuZn liquidus temperature is too high for brazing the brasses and nickel silvers. Torch brazing of the
aluminum bronzes facilitates the use of the lower brazing temperature of RBCuZn.
13. American Welding Society, 2011, Specification for Filler Metals
for Brazing and Braze Welding, A5.8/A5.8M:2011, Miami: American
Welding Society.
254
CHAPTER 3—COPPER AND COPPER ALLOYS
AWS WELDING HANDBOOK
Table 3.22
Guide to Brazing Copper and Copper Alloys
Commonly Used
Brazing Filler Metals
AWS Brazing
Atmospheresc
AWS Brazing Flux
Remarks
BCuP-2a, BCuP-3, BCuP-5a, RBCuZn,
BAg-1a, BAg-1, BAg-2, BAg-5, BAg-6,
BAg-18
1, 2, or 5
FB3-A, C, D, E, I, J
Oxygen-bearing coppers should
not be brazed in hydrogencontaining atmospheres.
Material
Coppers
High coppers
BAg-8, BAg-1
FB3-A
—
Red brasses
BAg-1a, BAg-1, BAg-2, BCuP-5, BCup-3,
BAg-5, BAg-6, RBCuZn
1, 2, or 5
Note b
FB3-A, C, D, E, I, J
—
Yellow brasses
BCuP-4, BAg-1a, BAg-1, BAg-5, BAg-6,
BCuP-5, BCuP-3
3, 4, or 5
FB3-A, C, E
Keep brazing cycle short.
Leaded brasses
BAg-1a, BAg-1, BAg-2, BAg-7, BAg-18,
BCuP-5
3, 4, or 5
FB3-A, C, E
Keep brazing cycle short and
stress relieve before brazing.
Tin brasses
BAg-1a, BAg-1, BAg-2, BAg-5, BAg-6,
BCuP-5, BCuP-3 (RBCuZn for low tin)
3, 4, or 5
FB3-A, C, E
Phosphor bronzes
BAg-1a, BAg-1, BAg-2, BCuP-5, BCuP-3,
BAg-5, BAg-6
1, 2, or 5
FB3-A, C, E
Stress relieve before brazing.
Silicon bronzes
BAg-1a, BAg-1, BAg-2
4 or 5
FB3-A, C, E
Stress relieve before brazing.
Abrasive cleaning may be helpful.
Aluminum bronzes
BAg-3, BAg-1a, BAg-1, BAg-2
4 or 5
FB4-A
Copper nickel
BAg-1a, BAg-1, BAg-2, BAg-18, BAg-5,
BCuP-5, BCuP-3
1, 2, or 5
FB3-A, C, E
Stress relieve before brazing.
Nickel silvers
BAg-1a, BAg-1, BAg-2, BAg-5, BAg-6,
BCuP-5, BCuP-3
3, 4, or 5
FB3-A, C, E
Stress relieve before brazing and
heat uniformly.
—
—
a. Protective atmosphere or flux is not required for brazing copper with BCuP fillers.
b. Furnace brazing without flux is possible if the workpieces are nickel plated or copper plated before brazing; follow recommendations for brazing nickel or
copper.
c. Hydrogen, inert gas, or vacuum atmospheres are usually acceptable (AWS Type 7, 9, or 10). Brazing atmospheres are listed below:
AWS Brazing
Atmosphere
Source
Maximum Dew Point
of Incoming Gas
AWS Brazing
Atmosphere
5
6A
6B
6C
7
9
10
1
Combusted fuel gas
(low hydrogen)
Room temp.
2
Combusted fuel gas
(decarburizing)
Room temp.
3
4
Combusted fuel gas, dried
–40°C (–40°F)
–40°C (–40°F)
Combusted fuel gas, dried
(carburizing)
BRAZING FLUXES AND ATMOSPHERES
Flux classifications FB3-A, FB3-C, and FB3-D (refer to
Table 3.22) are suitable for use with BAg and BCuP filler
metals for brazing all copper alloys, except the aluminum
bronzes. A more reactive flux classification FB4-A is used
for aluminum bronzes. Flux classifications FB3-C, FB3D, and FB3-K are required with RBCuZn filler metals
because of the high brazing temperatures required.
Source
Dissociated ammonia
Cryogenic and purified N2+H2
Cryogenic and purified N2+H2+CO
Cryogenic and purified N2
Hydrogen, deoxygenated and dried
Purified inert gas
Vacuum
Maximum Dew Point
of Incoming Gas
–54°C (–65°F)
–68°C (–90°F)
–29°C (–20°F)
–68°C (–90°F)
–59°C (–75°F)
—
—
Combusted fuel gases can be used as an economical
furnace brazing atmosphere for copper and copper
alloys, except for oxygen-bearing copper. Atmospheres
with high-hydrogen content cannot be used when brazing oxygen-bearing copper; the hydrogen diffuses into
the copper, reduces copper oxide, and forms water
vapor that will rupture the copper. Inert gases that have
suitable dew points are also good atmospheres for brazing copper and copper alloys.
AWS WELDING HANDBOOK
CHAPTER 3—COPPER AND COPPER ALLOYS
255
Table 3.23
Commonly Used Brazing Filler Metals for Copper and Copper Alloys*
Brazing Temperature
Range
Composition, wt %
AWS
Classification
BAg-1
UNS
No.
Ag
Cu
Zn
Cd
Sn
Fe
Ni
P
°C
°F
P07450
44–46
14–16
14–18
23–25
—
—
—
—
618–760
1145–1400
1175–1400
BAg-1a
P07500
49–51
14.5–16.5
14.5–18.5
17–19
—
—
—
—
635–760
BAg-2
P07350
34–36
25–27
19–23
17–19
—
—
—
—
702–843
1295–1550
BAg-3
P07501
49–51
14.5–16.5
13.5–17.5
15–17
—
—
2.5–3.5
—
688–816
1270–1500
BAg-5
P07453
44–46
29–31
23–27
—
—
—
—
—
743–843
1370–1550
BAg-6
PO7503
49–51
33–35
14–18
—
—
—
—
—
774–871
1425–1600
BAg-7
PO7563
55–57
21–23
15–19
—
4.5–5.5
—
—
—
652–760
1205–1400
BAg-8
P07720
71–73
Balance
—
—
—
—
—
—
780–899
1435–1650
BAg-18
P07600
59–61
Balance
—
—
9.5–10.5
—
—
—
718–843
1325–1550
BCu-1
C14180
—
99.9 min
—
—
—
—
—
0.75
1093–1149
2000–2100
RBCuZn-A
C47000
—
57–61
Balance
—
0.25–1.0
—
—
—
910–955
1670–1750
RBCuZn-C
C68100
—
56–60
Balance
—
0.8–1.1
0.25–1.2
—
—
910–955
1670–1750
RBCuZn-D
C77300
—
46–50
Balance
—
—
9–11
—
0.25
938–982
1720–1800
BCuP-2
C55181
—
Balance
—
—
—
—
—
7.0–7.5
732–843
1350–1550
BCuP-3
C55281
4.8–5.2
Balance
—
—
—
—
—
5.8–6.2
718–816
1325–1500
BCuP-4
C55283
5.8–6.2
Balance
—
—
—
—
—
7.0–7.5
691–788
1275–1450
BCuP-5
C55284
14.5–15.5
Balance
—
—
—
—
—
4.8–5.2
704–816
1300–1500
*Refer to AWS A5.8/A5.8M:2011, Specification for Filler Metals for Brazing and Braze Welding.
Vacuum is a suitable brazing environment, provided
that neither base metal nor filler metal contain elements
that have high vapor pressures at the brazing temperature. Zinc, phosphorus, and cadmium are examples of
elements that vaporize when heated in vacuum.
SURFACE PREPARATION
the Safe Practices section of this chapter to ensure the
safe use and handling of chemical cleaning agents.
Copper. Effective cleaning procedures for copper are
immersion in cold sulfuric acid, 5% to 15% by volume,
for 1 to 5 minutes, rinsing in cold water followed by a
hot water rinse, and drying in ambient air or by
mechanical air-blasting.
Good wetting and flow of filler metal in brazed
joints can be achieved only when the joint surfaces are
clean and free of oxides, dirt, and other foreign substances. Standard solvent or alkaline degreasing procedures are suitable for cleaning copper base metals.
Mechanical methods can be used to remove surface
oxides, but care should be taken to remove all adverse
films or deposits from the faying surfaces before brazing. Chemical removal of surface oxides requires an
appropriate pickling solution.
Beryllium Copper. The following two steps should
be used to prepare beryllium copper for brazing:
Chemical Cleaning
Chromium-Copper and Copper-Nickel Alloys.
Typical chemical cleaning procedures for several
alloys are described in the following sections. Refer to
1. Immersion in sulfuric acid, 20% by volume, at
71°C to 82°C (160°F to 180°F) until the dark
scale is removed, then rinsing with water, and
2. Dipping in cold 30% nitric acid solution for
15 to 30 seconds, then rinsing with hot water,
and drying in ambient air or by mechanical airblasting.
Chromium-copper and copper-nickel alloys can be
prepared for brazing by immersion in hot sulfuric acid,
5% by volume, for 1 to 5 minutes; rinsing with cold
256
CHAPTER 3—COPPER AND COPPER ALLOYS
followed by a hot-water rinse, and drying in
ambient air or by mechanical air-blasting.
Brass and Nickel Silver. Brass and nickel-silver can
be cleaned by immersion in cold sulfuric acid, 5% by
volume; rinsing in cold water, then rinsing in hot water,
and drying in ambient air or by mechanical air-blasting.
Silicon Bronze. Silicon bronze can be cleaned in a
three-step procedure: first by immersion in hot sulfuric
acid, 5% by volume, then rinsing in cold water, and
immersion in a cold mixture of hydrofluoric acid, 2%
by volume, and sulfuric acid, 5% to 15% by volume,
for 1 to 10 minutes. To complete cleaning, a three-step
procedure is followed: rinsing in cold water, then
rinsing in hot water, and finally, drying in ambient air
or by mechanical air-blasting.
Aluminum Bronze. Tough aluminum oxide can be
removed or loosened from aluminum bronze by immersion in a strong alkali solution of sodium hydroxide
(10 wt %) at 75°C (170°F) for 2 min to 5 min and
cold rinsing. This should be followed by successive
immersions in these two solutions: a cold mixture
of 2% hydrofluoric acid and 3% sulfuric acid for 1
min to 5 min and rinsing in cold water.
To complete the cleaning sequence, the workpiece
should be immersed in a solution of sulfuric acid, 5%
by volume, at 27°C to 49°C (80°F to 120°F) for 1 to 5
minutes, rinsing with cold water, then rinsing with hot
water, and drying in ambient air or by mechanical airblasting.
Copper Plating. It is often recommended that copper
plating be applied to the faces of copper alloys that contain strong oxide-forming elements to simplify brazing
and fluxing requirements. Copper plating should be
about 0.025 mm (0.001 in.) thick for chromium-copper
alloys. Plating of about 0.013 mm (0.0005 in.) thick is
sufficient on beryllium copper, aluminum bronze, and
silicon bronze.
AWS WELDING HANDBOOK
The copper-phosphorus and copper-silver-phosphorus filler metals (BCuP) are considered to be self-fluxing
on copper. A flux is beneficial when brazing massive
copper assemblies when prolonged heating results in
excessive oxidation. During brazing, the filler metal
loses some phosphorus, which results in a slight
increase in the remelt temperature. Brazed joints with
phosphorus-containing filler metal should not be
exposed to sulfurous atmospheres at elevated temperature; exposure for long periods results in corrosive
attack of the joint.
The recommended brazing temperatures should not
be exceeded when using the copper-zinc (RBCuZn)
filler metals; this avoids volatilization of zinc and the
resulting porosity in the joint. When torch brazing, an
oxidizing flame will reduce zinc fuming. The corrosion
resistance of these filler metals is inferior to that of
copper.
A lap joint will develop the full strength of annealed
copper at room temperature when the overlap is at least
three times the thickness of the thinner member. As the
service temperature increases, the strength of the brazing filler metal decreases more rapidly than the strength
of the copper or copper alloy, and failure will eventually occur through the joint. The tensile strength at
room temperature, elevated temperature, and sub-zero
temperature for single-lap joints brazed in copper is
shown in Table 3.24. Typical creep properties for
tough-pitch copper specimens brazed with BAg-1A,
BAg-6, and BCuP-5 filler metals are shown in Figure
3.11. At 25°C and 127°C (77°F and 260°F), failures
occurred in the base metal.
BRAZING OF HIGH-COPPER ALLOYS
Techniques for brazing the high-copper alloys—
beryllium copper, chromium copper, zirconium copper,
and cadmium copper—are described in this section.
Beryllium Copper
BRAZING OXYGEN-FREE COPPER
Oxygen-free, high-conductivity copper and deoxidized copper are readily joined by furnace brazing or
torch brazing. Boron-deoxidized copper is sometimes
preferred when brazing at high temperatures because
grain growth is less pronounced than that of other coppers.
Oxygen-bearing coppers are susceptible to oxide
migration and hydrogen embrittlement at elevated temperatures. These coppers should be furnace brazed in an
inert atmosphere or torch brazed with a neutral or
slightly oxidizing flame.
The surfaces of beryllium copper components must
be cleaned prior to brazing. The oxide scale can be
removed by pickling.
The 2% beryllium copper can be brazed by either of
two methods. The more common procedure involves
simultaneous brazing and solution heat treatment at
788°C (1450°F) in a furnace. The silver-copper eutectic
filler metal, BAg-8, is generally used with AWS classification FB3-A flux. The furnace temperature is quickly
lowered to 760°C (1400°F) to solidify the brazing filler
metal. The brazement is then quenched in cold water,
and finally age hardened at 316°C to 343°C (600°F to
650°F).
AWS WELDING HANDBOOK
CHAPTER 3—COPPER AND COPPER ALLOYS
257
Table 3.24
Tensile Strength of Single-Lap Brazed Joints in Deoxidized Copper*
Tensile Strength
–196°C (–321°F)
Brazing Filler Metal
MPa
BAg-1
BAg-6
22°C (72°F)
ksi
MPa
208
30.1
193
28.0
204°C (400°F)
ksi
MPa
ksi
131
19.0
67
9.7
121
17.6
—
—
BAg-8
170
24.7
121
17.6
—
—
BCuP-2
123
17.9
197
18.6
74
10.7
BCuP-4
150
21.4
132
19.1
—
—
BCup-5
151
21.9
123
17.9
74
10.8
*Specimens were made from 6.4 mm (0.25 in.) thick sheet; joints had an overlap of 3.8 mm (0.15 in.) and no braze fillet.
28
BCuP-5
BAg-1A
24
25°C
(77°F)
150
20
STRESS, MPa
BAg-6
BAg-1A
120
BCuP-5
90
16
127°C
(260°F)
BAg-6
12
8
60
STRESS, ksi
180
{ BAg-1A
BCuP-5
30
BCuP-5
4
BAg-1A
299°C (570°F)
399°C (750°F)
1
10
102
103
0
104
TIME, h
Figure 3.11—Stress-Rupture Strength Curves for Copper Brazed
with Three Filler Metals Using a Plug and Ring Creep Specimen
The second method, used with thin sections that can
be heated rapidly (preferably in one minute or less),
permits brazing beryllium copper at a temperature
below the solution-annealing temperature. The brazement can be precipitation hardened without having to
be solution treated. Fast heating rates can be attained
using an oxyacetylene welding (OAW) torch or by resistance heating. Brazing is satisfactorily performed using
BAg-1 filler metal and Classification FB3-A flux, but
other silver brazing filler metals can be suitable for special applications.
The 0.5% beryllium-copper alloys are solution heat
treated at 927°C (1700°F), quenched in cold water, and
age hardened at 454°C to 482°C (850°F to 900°F). This
alloy can be brazed rapidly with BAg-1 filler metal at
about 649°C (1200°F) after being precipitation hardened,
but the base metal is overaged during brazing, which
results in reduced hardness and strength properties.
258
CHAPTER 3—COPPER AND COPPER ALLOYS
Chromium Copper and Zirconium Copper
Chromium copper and zirconium copper are solution heat treated at 900°C to 1010°C (1650°F to
1850°F), quenched, and age hardened at 482°C
(900°F). Brazing with BAg filler metals and a fluoridetype flux should be performed after a solution heat
treatment and before age hardening. The mechanical
properties of the base metal after brazing and precipitation hardening will be lower than those of the solutiontreated and age-hardened material that has not been
brazed.
The brazing of chromium copper, followed by solution treatment and age hardening, results in near optimum mechanical properties. Distortion caused by
quenching from the solution-anneal temperature should
be evaluated for each application.
Cadmium Copper
Cadmium coppers are brazed in the same manner as
deoxidized copper.
BRAZING COPPER-ZINC ALLOYS (BRASS)
All brasses can be brazed with BAg and BCuP, and
RBCuZn filler metals. AWS class FB3-C flux is used
with BAg and BCuP filler metals; FB3-K is used with
RBCuZn filler metals.
Zinc fuming that occurs at temperatures above
400°C (750°F) can be reduced by fluxing the workpieces before furnace brazing, even when a protective
atmosphere is used. Torch brazing with an oxidizing
flame is also used to reduce zinc fuming. Brasses that
are subject to cracking when heated too rapidly (i.e.,
leaded brasses) should be heated slowly and uniformly
to the brazing temperature. Sharp corners and other
stress raisers that localize thermal strain during heating
should be avoided. Good practice requires heating
workpieces slowly to brazing temperature.
Brasses that contain aluminum or silicon require
cleaning; brazing procedures similar to those used for
aluminum bronze or silicon bronze should be applied.
Lead within the brass can alloy with the brazing filler
metal and cause brittleness, especially when the lead
content exceeds 3%. This can reduce the strength of the
joint. Leaded brasses require complete flux coverage to
prevent the formation of lead oxide or dross and also to
maintain good wetting and flow during brazing.
Stress-relieving before brazing and slow, uniform
heating minimizes the tendency of highly leaded brasses
to crack. Rapid heating to the brazing temperature
should be avoided.
AWS WELDING HANDBOOK
BRAZING COPPER-TIN ALLOYS
(PHOSPHOR BRONZE)
Phosphor bronzes are subject to cracking during
heating when in a stressed condition. Good practices
for successful brazements include the following:
1. Stress relieve or anneal before brazing,
2. Support with suitable fixtures to maintain a
stress-free condition during brazing,
3. Apply flux to completely cover the joint
surfaces, and
4. Use a slow heating cycle.
All of the phosphor bronzes can be brazed with BAg
and BCuP filler metals, although alloys with low tin
content can be brazed with RBCuZn filler metal.
The phosphor bronze components are sometimes
made by compacting and sintering powdered metal.
Before they are brazed, the areas of powdered metal
that separate from the braze joint must be treated to
seal any existing pores that would restrict the penetration of the brazing filler metal. Pores can be sealed by
painting the surface of a powdered metal component
with a colloidal graphite suspension and then baking at
a low temperature, followed by a cleaning procedure.
BRAZING COPPER-ALUMINUM ALLOYS
(ALUMINUM BRONZE)
Aluminum bronze is brazed with BAg brazing filler
metals and AWS Class FB4-A flux. At brazing temperature, refractory aluminum oxide forms on the surfaces
of bronze containing more than 8% aluminum. The
brazing procedures must prevent the formation of aluminum oxide to obtain satisfactory wetting and flow of
filler metal into the joint surfaces. In furnace brazing,
flux should be used in addition to the protective atmosphere.
Copper plating on joint surfaces prevents the formation of aluminum oxide during brazing. Copper-plated
components are brazed using procedures suitable for
brazing copper.
BRAZING COPPER-SILICON ALLOYS
(SILICON BRONZE)
Copper-silicon alloys should be cleaned and then
either coated with flux or copper plated before brazing;
this prevents the formation of refractory silicon oxide
on joint surfaces during brazing. Copper plating is recommended for best results. Mechanical or chemical
cleaning is used to remove oxide contamination from
the joint surfaces. Silver brazing filler metals and AWS
AWS WELDING HANDBOOK
CHAPTER 3—COPPER AND COPPER ALLOYS
Class FB3-C flux are used to braze copper-silicon
alloys.
A flux should be used in combination with a protective atmosphere for furnace brazing. When stressed, silicon bronze is subject to intergranular penetration by
the filler metal and also to hot-shortness. Components
should be stress relieved before brazing, and adequately
supported by fixtures during heating. The brazing temperature should be lower than 760°C (1400°F).
BRAZING COPPER-NICKEL ALLOYS
Copper-nickel alloys are brazed with BAg and BCuP
filler metals, although it should be noted that BCuP
filler metal forms a brittle nickel phosphide when brazing alloys contain more than 10% nickel. The structure
and properties of joints brazed with BCuP filler metal
should be thoroughly evaluated for the intended application. AWS Class FB3-C flux is suitable for most
applications.
The base metal surfaces must be free of sulfur or lead
that could cause cracking during the brazing cycle.
Chemical solvent or alkaline degreasing procedures can
be used to remove grease or oil. Surface oxides can be
removed by either mechanical or chemical cleaning, or
both.
Copper-nickel alloys in a cold-worked condition are
susceptible to intergranular penetration by molten filler
metal. These alloys should be stress relieved before
brazing to prevent cracking.
259
and should be stress relieved before brazing. Nickel silvers have poor thermal conductivity and should be
heated slowly and uniformly to brazing temperature in
the presence of sufficient flux.
BRAZING DISSIMILAR METALS
Dissimilar copper alloys are readily brazed, and copper alloys can also be brazed to other metals, such as
aluminum, steel, stainless steel, and nickel alloys. Suggested brazing filler metals for several dissimilar metal
combinations are shown in Table 3.25.
An example of dissimilar metal brazing is shown in
Figure 3.12, a brazed copper-to-aluminum transition
joint within a heating, ventilation, and air conditioning
(HVAC) system.
BRAZING COPPER-NICKEL-ZINC ALLOYS
(NICKEL SILVER)
Nickel silvers can be brazed using the same filler
metals and procedures as those used for brazing
brasses. If RBCuZn filler metal is used, precautions
should be taken when brazing at relatively high temperatures. When in the stressed condition, these alloys are
subject to intergranular penetration by the filler metal
Photograph courtesy of Bellman Melcor
Figure 3.12—Copper to Aluminum Brazed Joint
Table 3.25
Recommended Filler Metals for Brazing Copper Alloys to Other Metals
Carbon and Low
Alloy Steels
Cast
Iron
Stainless
Steels
Tool
Steels
Nickel
Alloys
Titanium
Alloys
Reactive
Metals
Refractory
Metals
BAg
BAg
BAg
BAg
BAg
BAg
BAg
BAg
BAu
BAu
BAu
BAu
BAu
—
—
—
RBCuZn
RBCuZn
—
RBCuZn
RBCuZn
—
—
—
—
—
—
BNi
—
—
—
—
260
CHAPTER 3—COPPER AND COPPER ALLOYS
SOLDERING
Copper and copper alloys are among the most frequently soldered engineering materials. The degree of
solderability, as shown in Table 3.26, ranges from
excellent to difficult.14 No serious problems arise in soldering most copper alloys, but alloys containing beryllium, silicon, or aluminum require special fluxes to
remove surface oxides. 15
The high thermal conductivity of copper and some
copper alloys requires a high rate of heat input when
localized heating is used.
SOLDERING FILLER METALS
The most widely used soldering filler metals for joining copper and copper alloys are the tin-lead filler metals, although in applications related to drinking water
or food, tin-antimony or tin-silver is used to avoid possible lead contamination. In many modern applications,
tin-lead soldering filler metals have been replaced
because of the hazards associated with lead. Tin readily
alloys and diffuses into copper and copper alloys. Copper alloys accept a certain amount of tin into solid solution, but one or more intermetallic phases (probably
Cu6Sn5) will form when the solid solubility limit is
exceeded. An intermetallic phase, which tends to be
brittle, forms at the faying surfaces of soldered joints.
14. Welding Handbook, 2007, 9th Ed., Volume 2, Chapter 13, Soldering, Miami: American Welding Society.
15. Vianco, P. T., Soldering Handbook, 1999, 3rd Ed., Miami:
American Welding Society.
AWS WELDING HANDBOOK
The thickness of this area should be minimized by
proper selection of process variables and service conditions. As the thickness of the intermetallic layer
increases, the strength of the soldered joint will
decrease, and service at elevated temperatures accelerates this change.
Copper and copper alloys are routinely soldered to
other materials; however, care must be taken for each
application to ensure phase compatibility between the
two base metals and the specific soldering filler alloy.
This is especially true for applications in which the
joints are subjected to temperatures that are above
ambient.
FLUXES
Organic and rosin types of noncorrosive fluxes are
excellent for soldering coppers and can be used with
some success on copper alloys containing tin and zinc,
if the surfaces to be soldered are precleaned. These
fluxes are used for soldering electrical connections and
electronic components. A light coating of flux should be
applied to the precleaned faying surfaces.
The inorganic corrosive fluxes are optional for use
on all the copper alloys, but these fluxes are required on
those alloys that develop refractory surface oxides, such
as silicon bronzes and aluminum bronzes. Aluminum
bronze is especially difficult to solder and requires special fluxes or copper plating. Inorganic chloride fluxes
are useful for soldering the silicon bronzes and copper
nickels.
Oxide films reform quickly on cleaned copper alloys,
so fluxing and soldering should be done immediately
after cleaning. Copper tube systems that are soldered
Table 3.26
Solderability of Copper and Copper Alloys
Base Metal
Solderability
Copper (Includes tough-pitch, oxygen-free, phosphorized, arsenical,
silver-bearing, leaded, tellurium, and selenium copper.)
Excellent. Rosin or other noncorrosive flux is suitable when properly
cleaned.
Copper-tin alloys
Good. Easily soldered with activated rosin and intermediate fluxes.
Copper-zinc alloys
Good. Easily soldered with activated rosin and intermediate fluxes.
Copper-nickel alloys
Good. Easily soldered with intermediate and corrosive fluxes.
Copper-chromium and copper-beryllium, alloys
Good. Require intermediate and corrosive fluxes and precleaning.
Copper-silicon alloys
Fair. Silicon produces refractory oxides that require use of corrosive
fluxes. Should be properly cleaned.
Copper-aluminum alloys
Difficult. High aluminum alloys are soldered with help of very corrosive
fluxes. Precoating may be necessary.
High-tensile manganese bronze
Not recommended. Should be plated to ensure consistent solderability.
AWS WELDING HANDBOOK
with 50% tin-50% lead or 95% tin-5% antimony soldering filler metal require a mildly corrosive liquid flux
or petrolatum pastes containing zinc and ammonium
chlorides. Many liquid fluxes used for plumbing applications are self-cleaning, but there is always a risk that
corrosive attack will continue after the soldering process is completed.
A highly corrosive flux can remove some oxides and
contaminating films, but uncertainty always remains as
to whether uniform cleaning has been achieved and,
again, whether corrosive attack will continue after soldering. Optimum soldering always starts with a clean
surface and a minimum amount of flux.
SURFACE PREPARATION
Chemical solvent or alkaline degreasing and pickling
are suitable for cleaning copper-base metals; mechanical methods are typically used to remove oxides. Chemical removal of oxides requires the use of a proper
pickling solution followed by thorough rinsing. Typical
procedures used for chemical cleaning are the same as
those described previously for brazing.
Copper-Alloy Coatings
Typical coatings used to prepare surfaces of copper
alloys for soldering are tin, lead, tin-lead, nickel, chromium, and silver. Soldering procedures depend on the
characteristics of the coating. Except for chromiumplated copper, none of the coating materials present any
serious soldering difficulty. Before soldering chromiumplated copper, the chromium must be removed from the
joint interfaces; the thermal conductivity of the base
metal must be considered.
Flux Removal
After the joint is soldered, flux residues that can be
harmful to the serviceability of the joint must be
removed. Removal of flux residues is especially important when the joints will be exposed to humid environments. Organic and inorganic flux residues that contain
salts and acids should be removed completely.
Non-activated rosin flux residues can remain on the
soldered joint, unless appearance is important or the
joint area is to be painted or otherwise coated. Activated rosin fluxes are treated in the same manner as
organic fluxes for structural soldering, but these fluxes
should be removed for critical electronic applications.
Zinc-chloride fluxes leave a fused residue that
absorbs water from the atmosphere. The best means for
removal of this residue is thorough washing in a hot solution of 2% concentrated hydrochloric acid (20 ml/L
[2.5 oz/gal]), followed by a hot-water rinse and air-blast
CHAPTER 3—COPPER AND COPPER ALLOYS
261
drying. The acid solution removes the white zinc-oxychloride crust, which is insoluble in water. Complete
removal sometimes requires additional rinsing in hot
water that contains some sodium carbonate (washing
soda), followed by a clear-water rinse. Mechanical scrubbing may also be necessary.
The residues resulting from the organic fluxes are
quite soluble in hot water. Double rinsing is always
advisable. The residues resulting from oily or greasy
paste flux can be removed with an organic solvent. Soldering pastes are emulsions of petroleum jelly and a
water solution of zinc-ammonium chloride. The corrosive chloride residue must be removed from the soldered joint.
When rosin flux residues are to be removed, alcohol
or chlorinated hydrocarbons can be used. Certain rosin
activators are soluble in water but not in organic solvents. Rosin flux residue can be removed using organic
solvents, followed by water rinsing.
MECHANICAL PROPERTIES
The mechanical properties of a soldered joint depend
on composition of the soldering filler metal and a number of process variables. These variables include the
thickness of the filler metal in the joint, the composition
of the base metal, the type of flux, soldering temperature, soldering time, and cooling rate.
Soldered joints are usually designed to be loaded in
shear. Shear strength and creep strength in shear are the
important mechanical properties. For specialized applications, such as automotive radiators, peel strength and
fracture initiation strength can be important, and, in a
few cases, tensile strength can be a factor.
Shear Strength
Shear strength is determined by testing single-lap
joints or double-lap joints in flat specimens or sleevetype cylindrical specimens. Testing is done with a crosshead speed of 25.4 or 2.54 mm/min (1 or 0.1 in./min). The
shear strength of copper joints soldered with tin-lead
soldering filler metals are shown in Figure 3.13. The
maximum shear strength of the joint is obtained with
eutectic composition soldering filler metal (63% tin37% lead). Shear strength may decrease up to 30% if the
joints are aged at room temperature or at moderately
elevated temperature for several weeks prior to testing.
The shear strength of soldered joints decreases with
increasing temperature, as shown in Figure 3.14 for two
soldering filler metals commonly used in copper plumbing applications. Many soldering filler metals remain
ductile at cryogenic temperatures, and strength
increases significantly as the temperature decreases
below room temperature.
CHAPTER 3—COPPER AND COPPER ALLOYS
AWS WELDING HANDBOOK
50
40
30
4
20
SHEAR STRENGTH, ksi
SHEAR STRENGTH, MPa
6
2
10
0
0
20
40
60
80
100
TIN CONTENT, %
Figure 3.13—Shear Strength of Copper Joints Soldered with Tin-Lead Soldering Filler Metals
TEMPERATURE, °C
0
50
100
150
200
60
8
6
40
95% TIN – 5% ANTIMONY
30
4
20
SHEAR STRENGTH, ksi
50
SHEAR STRENGTH, MPa
262
2
10
50% TIN – 50% LEAD
0
0
0
100
200
300
400
TEMPERATURE, °F
Figure 3.14—Shear Strength at Elevated Temperatures for Copper Joints
Soldered with Tin-Antimony and Tin-Lead Soldering Filler Metals
AWS WELDING HANDBOOK
CHAPTER 3—COPPER AND COPPER ALLOYS
Creep Strength
263
Table 3.27
Tensile Strength of Soldered Copper Butt Joints
The creep strength of a soldered joint in shear is considerably less, sometimes below 10%, than the shorttime shear strength of the joint. The creep strength of
copper joints in shear soldered with three soldering
filler alloys are shown in Figure 3.15. The 50% tin50% lead and 95% tin-5%-antimony filler alloys have
about the same short-time shear strength, but the tinantimony solder has much greater long-time creep
strength.
Solder Composition, %
Tensile Strength
Tin
Lead
MPa
ksi
20
80
77.9
11.3
30
70
95.1
13.8
40
60
115.8
16.8
50
50
125.5
18.2
63
37
135.1
19.6
Tensile Strength
Typical tensile strengths of soldered butt joints made
with five compositions of tin-lead soldering filler alloys
are presented in Table 3.27. Soldered joints are much
stronger in tension than in shear. Tensile strength
increases with increasing tin content up to the eutectic
composition. Soldering is not recommended for butt
joints in copper because voids in the filler metal layer
will cause premature failure through the filler metal
when the joint is loaded.
APPLICATIONS
The applications described in this section include the
welding of a copper dipole vacuum chamber for a highenergy accelerator, a seawater distiller for shipboard
installation, copper tubing in a brewery tank, cooling
TEMPERATURE, °C
50
100
CURVE
1
1
2
8
CREEP STRENGTH, MPa
150
200
SOLDERING FILLER METAL
95% TIN – 5% ANTIMONY
95% LEAD – 5% TIN
50% TIN – 50% LEAD
3
6
250
1.2
1.0
0.8
0.6
2
4
0.4
CREEP STRENGTH, ksi
0
1
2
3
0.2
2
3
0
0
0
100
200
300
400
500
TEMPERATURE, °F
Figure 3.15—Creep Strength of Soldered Copper Joints at Elevated Temperature
264
CHAPTER 3—COPPER AND COPPER ALLOYS
AWS WELDING HANDBOOK
fans for electric motors, a large discharge elbow welded
to a motor mount of a centrifugal pump, a water box
for a condenser, and two surfacing applications.
WELDING CONDITIONS AND PROCESES
The same properties that make pure copper a good
choice for an application also make it difficult to
achieve a high degree of precision and accuracy when
welding this material. An example is the controlled
joining of a cooling bar and pump screen to a rectangular copper vacuum chamber while maintaining material
properties and ultrahigh vacuum integrity, described in
the next section.
Pure Copper Dipole Vacuum Chamber for
a High-Energy Accelerator
Electron beam welding (EBW) was used to join components of copper vacuum chambers, called highenergy dipole assemblies, for use in a linear particle
accelerator (LINAC). A linear particle accelerator is an
electrical device that accelerates subatomic particles for
use in applications such as the generation of X-rays in a
hospital and as an injector used with a high-energy synchrotron at a dedicated experimental particle physics
laboratory. The EBW process was used to join a number of system components used on the LINAC. Some of
the welded components were used in the fabrication of
pure copper vacuum chambers that were 1 m (39.4 in.)
long. The interior of these chambers is designed to contain high beam currents, which will generate high heat
and high gas loads.
In this example, the dipole (DIP) chamber was comprised of three oxygen-free high-conductivity (OFHC)
machined copper sub-assemblies: a rectangular vacuum
chamber, a cooling bar, and a screen separator. The
first procedure consisted of welding the cooling bar to
the rectangular chamber. Two penetration welds measuring 12 mm (0.47 in.) were made, one on each side,
with a total workpiece thickness of about 24 mm (0.94
in.) The workpiece was not removed from the tooling
constraints until the tacking and welding cycles were
complete on both sides of the cooling bar. After the
cooling bar sections were welded, the DIP screen separator was welded within the rectangular chamber. Similar to welds in the cooling bar, the DIP screen welds
were made and the tooling constraints were retained
until welds were made on both sides of the screen.
After welding, the completed assembly was ultrasonically tested, revealing 100% consumption of the weld
area for the cooling bar, and 50% to 70% joint consumption without a breakthrough of any weld face in
the DIP screen separator. Figure 3.16 shows a sample
Photographs courtesy of Sciaky Inc.
Figure 3.16—Sample Section of the
Dipole Vacuum Chamber After Welding
BASE
FIXTURE
COOLING BAR
HOLDING
FIXTURE
(A)
(B)
Source: Sciaky Inc.
Figure 3.17—Fixture with Two Positions
of a Moveable Electron Beam Welding Gun
Used to Weld the Dipole Screen Separator
AWS WELDING HANDBOOK
CHAPTER 3—COPPER AND COPPER ALLOYS
265
Table 3.28
Nominal Parameters for Electron Beam Welds in a
Cooling Bar and DIP Screen for a Dipole Chamber Assembly
Welding System: Electron Beam Welding—High Vacuum, 30 kW, 60 kV
Welding power for cooling bar weld
Size of weld
55 kV, 130 mA
12 mm (4.7 in.)
Welding power for DIP screen weld
Size of weld
55 kV, 110 mA
10 mm (3.9 in.)
Welding speed, complete-penetration weld
Size of weld
25.4 mm/sec (60 in./min)
12 mm (4.7 in.)
Welding speed, partial penetration weld
Size of weld
12.7 mm/sec (30 in./min)
10 mm (3.9 in.)
Vacuum level
1.33 ×10–2 Pa (1 × 10–4 torr)
Gun-to-workpiece distance
20.3 cm (8 in.)
Focal spot size of the electron beam
0.6 mm (0.024 in.)
Focus condition for cooling bar, complete-penetration weld
Sharp focus at 12.7 mm (0.5 in.) above surface
Focus condition for DIP screen, partial-penetration weld
Sharp focus at 12.7 mm (0.5 in.) above surface
Beam oscillation—cooling bar weld
Circular 1000 Hz
Beam oscillation—DIP screen weld
Circular 15 Hz
section of the completed assembly. The nominal parameters used to produce these welds are listed in Table 3.28.
The diagrams in Figure 3.17(A) and Figure 3.17(B)
show details of the orientation of the moveable electron
beam gun used to make these welds.
Copper-Nickel Water Box for a Shipboard
Condenser
This example refers to the fabrication of a water box
for a shipboard condenser that cools turbine exhaust
steam. The mechanically formed head was made of
ASTM B402 Type 90/10 copper nickel (C70600), and
the flanges were made of ASTM A285 Grade C carbon
steel. The shielded metal arc welding process was used
with 3.2 mm and 4.0 mm (0.125 in. and 0.156 in.)
diameter ENiCu-7 electrodes. Typical welding current
for 3.2 mm (0.125 in.) diameter electrodes was 90 A
to 130 A, DCEP. When 4.0 mm (0.156 in.) diameter
electrodes were used, welding current was adjusted to
120 A to 170 A. A minimum of 16°C (60°F) preheat
was required, and maximum interpass temperature was
limited to 66°C (150°F).
Seawater Distillers for Shipboard Operation
A submerged-tube shipboard distilling plant that
produces 11 356 L (3000 gal) of fresh water per day is
shown in Figure 3.18. The distilling plant was fabricated from ASTM B171M Type 90/10 copper nickel
(C70600) plate and ASTM B111 tube ranging in thickness from 2.5 mm to 25 mm (0.1 in. to 1 in.).
Copper alloy C70600 was used because of the excellent resistance to seawater corrosion and long-term
dependability of this alloy. It was also important for
this particular distilling plant because it was used
aboard a minesweeper in which the materials must have
low magnetic permeability. This distiller was also economical to operate because waste heat was used to distill the water.
The distilling plant was welded with the GMAW and
GTAW processes using ERCuNi filler metal and argon
shielding gas. Welding parameters are shown in Table
3.29. No preheat was used, but welding was restricted
to a minimum material temperature of 16°C (60°F).
Maximum interpass temperature was 177°C (350°F).
The unit was not postweld heat treated.
266
CHAPTER 3—COPPER AND COPPER ALLOYS
AWS WELDING HANDBOOK
(A) Pretreatment
(B) Distiller
Photographs courtesy of Aqua-Chem, Inc.
Figure 3.18—Two Units of a Seawater Distilling Plant Fabricated with Copper-Nickel Alloy C70600
AWS WELDING HANDBOOK
CHAPTER 3—COPPER AND COPPER ALLOYS
Table 3.29
Welding Parameters for Copper-Nickel
Alloy Seawater Distilling Plant
Gas Tungsten Arc Welding
Current
225 A, DCEN
Gas Metal Arc Welding
Current
250 A, DCEP
Voltage
27 V
267
from aluminum bronze plate and castings, designed to
resist corrosive attack from seawater. Most sections of
the elbow were C61300 plate; the flange rings were
temper-annealed, centrifugal cast C95200 aluminum
bronze. Most of the welds were made using the GMAW
process, although the root passes in complete penetration joints were deposited with GTAW. Welding
parameters are shown in Table 3.30. The elbow and
motor mount were welded at room temperature with a
maximum interpass temperature of 260°C (500°F). No
postweld heat treatment was performed.
Beryllium Copper Toroidal Field Coils
Copper Steam Coils in a Brewery
Beryllium copper combines high strength and good
electrical conductivity; therefore, this alloy was selected
The steam coils inside of a mash cooker in a brewery
are designed for operation at high temperatures in a
highly corrosive atmosphere; periodically, the coils
must be replaced. This example describes the installation of steam coils in a 6.1 m × 4.4 m (20 ft × 14.5 ft)
mash cooker tank. The steam coils are 3.7 m, 3 m, and
2.4 m (12 ft, 10 ft, and 8 ft) in diameter and are encircled inside the mash cooker tank, as shown in Figure
3.19. They are made of B-42/GR-122 copper pipe,
152 mm and 203 mm (6 in. and 8 in.) in diameter with
a wall thickness of 6.35 mm (0.25 in.). The joint design
selected was the J-edge shape; templates were designed
for these.
Off-site welding was limited to components that
could be inserted through the 60.9 cm (24 in.) opening
of the cooker. The use of mechanized orbital welding
solved limited-access problems in many instances.
Cooling Fans for Electric Motors
The cooling fans for explosion-proof electric motors
shown in Figure 3.20 were fabricated from copper
alloys because of the non-magnetic and non-sparking
properties of the alloys. The central hub of each fan is a
centrifugally cast tin-bronze alloy that contains 1.5%
tin and 0.3% phosphorus. The alloy in the conical base,
outer ring, and fins is C61300 aluminum bronze 4.8
mm (0.19 in.). Components were welded with the gas
tungsten arc welding (GTAW) process using argon
shielding gas and ERCuAl-A2 filler metal with a diameter of 2.4 mm (0.094 in.). Direct current electrode negative was used at 135 amperes (A).
Aluminum-Bronze Discharge Elbow for a
Centrifugal Pump
The discharge elbow and motor mount for a vertical
centrifugal pump shown in Figure 3.21 was fabricated
Photograph courtesy of Arc Machines, Inc.
Figure 3.19—Inspection of Welds in Steam Coils
inside a 6.1 m × 4.4 m (20 ft × 14.5 ft)
Mash Cooker in a Brewery
268
CHAPTER 3—COPPER AND COPPER ALLOYS
AWS WELDING HANDBOOK
Table 3.30
Welding Parameters for
Aluminum-Bronze Discharge Elbow
Gas Tungsten Arc Welding
Filler metal
ERCuAl-A2, 2.4 mm or 3.2 mm (0.094 in. or
0.125 in.) diameter
Shielding gas
Helium or argon/helium
Gas flow rate
17 L/min to 19 L/min (35 ft3/hr to 40 ft3/hr)
Current
190 A to 220 A, DCEN
Gas Metal Arc Welding
Filler metal
1.6 mm (0.062 in.) diameter ERCuAl-A2
Shielding gas
Argon
Gas flow rate
21L/min to 26 L/min (45 ft3/hr to 55 ft3/hr)
Current
320 A, DCEP
Voltage
29 V to 32 V
Photograph courtesy of Ampco Metal, Inc.
Figure 3.20—Cooling Fans for Electric
Motors Welded with the GTAW Process
for the fabrication of large conductors, for example, the
welding of toroidal field coils for fusion reactor
research. A conceptual toroidal field coil is shown in
Figure 3.22.
Fabrication of this coil required butt joints in 28 mm
(1.1 in.) thick beryllium-copper plates to form a coil
measuring 6.1 m (20 ft) high by 3.65 m (12 ft) wide.
Butt joints were required to have strength equivalent to
the base metal. The beryllium-copper alloy C17510,
Cu-0.3Be was used. Sample butt joints were prepared
for double-U-groove welds, using the GMAW process.
Filler metal was 1.14 mm (0.045 in.) diameter C17200,
Cu-1.9Be alloy and shielding gas was 75% helium-25%
argon at a flow rate of 47.2 L/min (100 ft 3/hr). Plates
were preheated to 149°C (300°F). Welding parameters
are shown in Table 3.31. Completed welds were
postweld heat treated to develop ultimate tensile
strength of 683 MPa (99 ksi) and yield strength of 586
MPa (85 ksi). Welding, grinding, and machining of
beryllium copper requires special precautions compared
to other copper alloys because beryllium-copper has a
greater potential for health hazards. Testing of the shop
environment is necessary to ensure that fume controls
are adequate to protect workers.
Photograph courtesy of Ampco Metal, Inc.
Figure 3.21—Pump Discharge Elbow
Fabricated with Aluminum Bronze
Copper-Nickel Weld Surfacing
Automatic gas tungsten arc welding with a hot-wire
addition of filler metal was used to clad a carbon steel
flange with copper nickel for use on a shipboard tur-
AWS WELDING HANDBOOK
CHAPTER 3—COPPER AND COPPER ALLOYS
269
3.
(1284 m
.60
ft)
COIL CASE
6.
(2039 m
.95
ft)
1.2
7m
(4.
17
ft)
2.5
(8. 6 m
39
ft)
TOROIDAL
FIELD COIL
Figure 3.22—Toroidal Field Coil and Coil Case
Figure 3.23—GTAW Cladding of a
Steel Flange with Copper-Nickel
Table 3.31
Welding Parameters For Butt Joints in
28 mm (1.1 in.) Thick Beryllium Copper
Wire Feed Speed
Travel Speed
Current
Voltage
Root Pass
Fill Passes
222 mm/s
(525 in./min)
7.6 mm/s
(18 in./min)
390 A, DCEP
30 V
243 mm/s
(575 in./min)
5.1 mm/s
(12 in./min)
430 A, DCEP
30 V
bine condenser. The flange, shown in Figure 3.23, was
made of ASTM A285 Grade C steel and was welded to
a copper-nickel pipe. The first layer of GTAW weld
cladding was nickel (ERNi); the second layer was copper nickel. The copper nickel was deposited with 1.6 mm
(0.062 in.) diameter ERCuNi filler metal. Shielding gas
was 75% helium-25% argon shielding at flow rates of
40 L/min to 45 L/min (85 ft3/hr to 95 ft3/hr). Minimum
preheat temperature was 16°C (60°F); maximum interpass temperature was 66°C (150°F). Gas tungsten arc
welding was used with direct current electrode negative.
Welding parameters are listed in Table 3.32.
Aluminum-Bronze Surfacing
Aluminum-bronze surfacing was applied to the bearing surfaces of a cast steel equalizer crown cushion
using the manual GMAW process.16 An equalizer
crown cushion is a vital part of an electric mining
shovel that is subject to intense wear, impact, and galling. In this example, the size of the workpiece is indicated by its weight: 467 kg (1030 lbs). Aluminum
16. Information on this application was provided by Ampco Metal,
Inc.
270
CHAPTER 3—COPPER AND COPPER ALLOYS
Table 3.32
Welding Parameters For Hot-Wire
GTAW Cladding of a Carbon Steel Flange
Arc amperage
Arc voltage
Hot wire amperage
Wire feed speed
Travel speed
340 A to 370 A
14 V to 16 V
85 A to 105 A (ac)
38 mm/s to 42 mm/s (90 in./min to 100 in./min)
1.5 mm/s to 2.1 mm/s (3.5 in./min to 5.0 in./min)
bronze-bearing surfaces reduce friction and provide
wear resistance.
Filler metal ERCuAl-A2 was used with argon shielding. Welding current was 250 A, direct current electrode positive, and welding voltage was 26 V. The
surfacing welds were deposited in two passes to a thickness of 9.5 mm (0.375 in.).
Welded Copper Plumbing Fittings
For some applications, large-diameter, welded
plumbing fittings have inherent advantages compared
to cast plumbing fittings. Welded fittings can be made
that are lighter in weight and can be formed into more
configurations than cast fittings. Large diameter, phosphorus-deoxidized copper (C12200) fittings are used
for commercial and industrial plumbing, heating, ventilation, and air-conditioning systems. The fitting shown
in Figure 3.24 was welded with the GTAW process
Photograph courtesy of Elkhart Products Corp.
and Copper Development Association
Figure 3.24—Welded Plumbing Fitting
AWS WELDING HANDBOOK
using silicon bronze (ERCuSi-A) filler metal and 50%
argon-50% helium shielding gas. Direct current electrode negative was used at 225 A to 275 A. Welds were
made without preheat or postweld heat treatment.
Phosphorus-Deoxidized Copper Nuclear
Waste Containers
The safe disposal of spent nuclear fuel and high level
radioactive waste for long-term storage (10 000 years)
has been a topic of investigation for many years. One
proposed resolution to the requirements of this project
involved the fabrication of thick-section copper vessels
4.9 m (16.1 ft) high, 0.81 m (2.65 ft) in diameter and
50 mm to 100 mm (2.0 in. to 3.9 in.) thick.
The corrosion properties of copper are suitable for
long-term containment, and it was determined that
electron beam welding (EBW) would meet these longterm requirements. The thermal conductivity of copper
required a concentrated, high-power heat source to
achieve melting, while single-pass, deep-penetration
welds that would limit total heat input and the overheating of container contents were also required. The
double-wall container demonstration component used
for weld development is shown in Figure 3.25.
This successful welding project was not implemented
in the United States; however, the importance of the
venture was that it demonstrated that welds of critical
quality could be made in 2-inch thick copper using
EBW.
Photograph courtesy of PTR-Precision Technologies, Inc.
Figure 3.25—Section of a Double-Wall
High-Integrity Waste Container after Welding
AWS WELDING HANDBOOK
CHAPTER 3—COPPER AND COPPER ALLOYS
271
SAFE PRACTICES
Photograph courtesy of
PTR-Precision Technologies, Inc.
Figure 3.26—Cross Section of Lid-to-Wall
Weld Displaying 44.5 mm (1.75 in.)
Single-Pass Joint Penetration
The outer cylinder was made of phosphorus deoxidized copper 44 mm (1.7 in.) thick; the end cap was
made of copper 51 mm (2.0 in.) thick. A stepped joint
was used to provide a locating feature for the end cap
and backup material to prevent over-penetration of the
joint so that the electron beam does not reach the interior of the container. A depth-to-width aspect ratio of
nearly 30 to 1 was achieved, melting only the material
required to fuse the entire joint and keeping heat input
to a minimum. A cross section of the weld is shown in
Figure 3.26. The ability to rapidly deflect the electron
beam to stabilize the deep vapor keyhole cavity was
instrumental in reducing porosity and root discontinuities to acceptable levels. No porosity or incomplete
fusion was observed within the joint region of these
deep, single-pass welds in copper. Slight intermittent
cold shuts at the root tip were observed, but these were
well below the joint line. The parameters used to perform the weld are shown in Table 3.33.
Table 3.33
Welding Variables—Electron
Beam Deep-Penetration Welding
Welding System: Electron Beam Welding—High Vacuum, 150 kV
Welding power
25 kW (150 kV, 167 mA)
Welding speed
0.38 m/min (15 in./min)
Vacuum level
<1.33 × 10–2 Pa (<10–4 torr)
First weld pass
Sharp surface focus, with beam deflection
Second cosmetic pass
Highly defocused
Copper and a number of alloying elements in copper
alloys (arsenic, beryllium, cadmium, chromium, lead,
manganese, and nickel) have low or very low Permissible Exposure Limits (PELs) as established by the Occupational Safety and Health Administration (OSHA), or
very low Threshold Limit Values (TLVs®) as set by
the American Conference of Governmental Industrial
Hygienists.17
Special ventilation precautions are required when
welding, brazing, soldering, or grinding copper or copper alloys to ensure that the level of contaminants in the
atmosphere is below the limit allowed for worker exposure. These precautions may include local exhaust ventilation or respiratory protection, or both. For proper
procedures, refer to ANSI Z49.1:2012, Safety in Welding, Cutting, and Allied Processes, published by the
American Welding Society. This standard is available
on line at www.aws.org.18
Welding copper alloys that contain appreciable
amounts of beryllium, cadmium, or chromium can
present additional health hazards to welders and others
in the work area. When copper alloys containing these
elements are welded, the user should consult the OSHA
guidelines for the specific element. Exposure to welding
fumes containing these elements can cause adverse or
severe health effects. Refer to Appendix A of this volume for a detailed list of health and safety codes, standards, and related publications.
Workers must be trained in safe practices for handling and mixing acid solutions to prevent injury when
acids are used for cleaning purposes. Proper dilution
and disposal of acid solutions are also required. Work
areas must be properly ventilated and equipped with
safety showers and eyewash stations. Workers must
wear protective clothing and equipment, including eye,
face, and body protection.
Fumes and dust from copper and zinc can cause irritation of the upper respiratory tract, nausea, and metal
fume fever. They can also cause skin irritation, dermatitis, and eye problems. Cadmium and beryllium fumes
are toxic when inhaled.
Fluxes used for welding, brazing, and soldering certain copper alloys may contain fluorides and chlorides.
17. American Conference of Governmental Industrial Hygienists
(ACGIH), TLVs® and BEIs®: Threshold Limit Values for Chemical
Substances and Physical Agents in the Workroom Environment,
Updated annually, Cincinnati: American Conference of Governmental Industrial Hygienists. (Editions of this publication are also available in Greek, Italian, and Spanish.)
18. American National Standards Institute (ANSI), 2012, Safety in
Welding, Cutting, and Allied Processes, ANSI Z49.1:2012, Miami:
American Welding Society. A copy of this standard is available for
download at www.aws.org.
272
CHAPTER 3—COPPER AND COPPER ALLOYS
Fumes from these fluxes can be irritating to the eyes,
nose, throat, and skin. Some fluorine compounds are
toxic.
Furnaces or retorts that use a flammable brazing
atmosphere must be purged of air prior to heating. To
avoid suffocation of personnel, controlled-atmosphere
furnaces must be purged with air before personnel are
permitted to enter them. Specific requirements for
safely when working within enclosed spaces must be
followed.
Good personal hygiene should be practiced, particularly before eating. Food and beverages should not be
stored or consumed in the work area. Contaminated
clothing should be changed. Refer to Welding Handbook, 9th Ed., Vol. 1, Chapter 17 for more information.
BIBLIOGRAPHY
American National Standards Institute (ANSI). 2005.
Safety in welding, cutting, and allied processes. ANSI
Z49.1:2012. Miami: American Welding Society.
American Welding Society (AWS) Committee on Brazing and Soldering. 2007. Brazing handbook. 5th ed.
Miami: American Welding Society.
American Welding Society (AWS) Committee on Definitions and Symbols. 2010. Standard welding terms
and definitions, including terms for adhesive bonding, brazing, soldering, thermal cutting, and thermal
spraying, AWS A3.0M/A3.0:2010. Miami: American
Welding Society.
American Welding Society (AWS) Committee on Filler
Metals and Allied Materials. 2008. Specification for
copper and copper-alloy electrodes for shielded
metal arc welding, AWS A5.6/A5.6M:2008. Miami:
American Welding Society.
American Welding Society (AWS) Committee on Filler
Metals and Allied Materials. 2007. Specification for
copper and copper-alloy bare welding rods and electrodes, AWS A5.7/A5.7M:2007. Miami: American
Welding Society.
American Welding Society (AWS) Committee on Filler
Metals and Allied Materials. 2011. Specification for
filler metals for brazing and braze welding, AWS
A5.8/A5.8M:2011. Miami: American Welding Society.
American Welding Society (AWS) Committee on Filler
Metals and Allied Materials. 2003. Specification for
fluxes for brazing and braze welding, AWS A5.31-92
(R2003). Miami: American Welding Society.
American Welding Society (AWS) Welding Handbook
Committee. 2004. Welding processes, part 1. Edited
by A. O’Brien. Vol. 2 of Welding handbook. 9th ed.
Miami: American Welding Society.
AWS WELDING HANDBOOK
American Welding Society (AWS) Welding Handbook
Committee. 2007. Welding processes, part 2. Edited
by A. O’Brien and C. Guzman. Vol. 3 of Welding
handbook. 9th ed. Miami: American Welding Society.
ASTM International 2007. Standard practice for numbering metals and alloys in the unified numbering
system (UNS). ASTM E527-07. West Conshohocken, Pennsylvania: ASTM International.
Resistance Welding Manufacturing Alliance (RWMA).
2003. Resistance welding manual. 4th ed. Philadelphia: RWMA. Section 13.4.
Vianco, P. T. 1999. Soldering handbook. 3rd ed.
Miami: American Welding Society.
SUPPLEMENTARY
READING LIST
ASM International. 1993. Welding, brazing, and soldering. Edited by D. L. Olson, T. A. Siewert, S. Liu,
and G. R. Edwards. Vol. 6 of ASM handbook. 10th
ed. Materials Park, Ohio: ASM International.
ASM International. 1990. Properties and selection:
Nonferrous alloys and special-purpose materials.
Vol. 2 of ASM handbook. 10th ed. Materials Park,
Ohio: ASM International.
International Nickel Company. 1979. Guide to the
welding of copper-nickel alloys. INCO 4441/178.
New York: International Nickel Company.
WELDING
Brandon, E. 1969. The weldability of oxygen-free,
boron-deoxidized and deoxidized low phosphorus
copper. Welding journal. 48(5): 187-s–194-s.
Bray, R. S., L. J. Lozano, and R. E. Willett. 1969. Metallographic study of weld solidification in copper.
Welding journal. 48(5): 181-s–185-s.
Dawson, R. J. C. 1983. Welding of copper and copper
base alloys. Bulletin 287. New York: Welding
Research Council.
Dimbylow, C. S., and R. J. C. Dawson. 1978. Assessing
the weldability of copper alloys. Welding and metal
fabrication. 46(9): 461–71.
Fisher, S. M., D. Frederick, M. R. Louthan, Jr., and J.
H. Wilson. 1983. The structural integrity of copper
nickel to steel shielded metal arc weldments. Welding
journal. 62(3): 37–43.
Gutierrez, S. H. 1991. Understanding GTA welding of
90/10 copper nickel. Welding journal. 70(5): 76–78.
Hartsell, E. W. 1973. Joining copper and copper alloys.
Welding journal. 52(2): 88–100.
AWS WELDING HANDBOOK
Hashimoto, K., T. Sato, and K. Niwa. 1991. Laser
welding copper and copper alloys. Journal of laser
applications. 3(1): 21–25.
Johnson, L. D. 1970. Some observations on the electron
beam welding of copper. Welding journal. 49(2): 55-s–
60-s.
Kelley, T. J. 1981. Ultrasonic welding of Cu-Ni to steel.
Welding journal. 60(4): 29–31.
Littleton, J., J. Lammas, and M. F. Jordan. 1974. Nitrogen porosity in gas shielded arc welding of copper.
Welding journal. 53(12): 561-s–565-s.
Mustaleski, T. M., R. L. McCaw, and J. E. Sims. 1988.
Electron beam welding of nickel-aluminum bronze.
Welding journal. 67(7): 53–59.
Ruge, J., K. Thomas, C. Eckel, and S. Sundaresan.
1986. Joining of copper to titanium by friction welding. Welding journal. 66(8): 28–31.
Sandor, L. W. 1982. Copper nickel for ship hull constructions—welding and economics. Welding journal. 61(12): 23–30.
Sandor, L. W. 1984. Pulsed GMA spot welding of copper-nickel to steel. Welding journal. 63(6): 35–50.
Savage, W. F., E. F. Nippes, and T. W. Miller. 1976.
Microsegregation in 70Cu-30Ni weld metal. Welding journal. 55(6): 165-s–173-s.
Savage, W. F., E. F. Nippes, and T. W. Miller. 1976.
Microsegregation in partially heated regions of
70Cu-30Ni weldments. Welding journal. 55(7): 181-s–
187-s.
Tumuluru, M., and E. F. Nippes. 1990. Weld ductility
studies of a tin-modified copper nickel alloy. Welding
journal. 69(5): 197-s–204-s.
CHAPTER 3—COPPER AND COPPER ALLOYS
273
Wold, K. 1975. Welding of copper and copper alloys.
Metal progress.108(8): 43–47.
BRAZING
Belkin, E., and P. K. Nagata. 1975. Hydrogen embrittlement of tough pitch copper by brazing. Welding
journal. 54(2): 54-s–62-s.
Chatterjee, S. K., Z. Mingxi, and A. C. Chilton. 1991.
A study of some Cu-Mn-Sn brazing alloys. Welding
journal. 70(5): 118-s–122-s.
Datta, A., A. Rabinkin, and D. Bose. 1984. Rapidly
solidified copper-phosphorus base brazing foils.
Welding journal. 63(10): 14–21.
Gibbay, S. F., F. Dirnfeld, J. Ramon, and H. Z. Wagner. 1990. The mechanism of tough-pitch copper embrittlement by silver brazing alloys. Welding journal.
69 (10): 378-s–381-s.
Jones, T. A., and C. E. Albright. 1984. Laser beam
brazing of small diameter copper wires to laminated
copper circuit boards. Welding journal. 63(12): 34–47.
McFayden, A. A., R. R. Kapoor, and T. W. Eagar.
1990. Effect of second phase particles on direct brazing of alumina dispersion hardened copper. Welding
journal. 69(11): 399-s–407-s.
Mottram, D., A. S. Wronski, and A. C. Chilton. 1986.
Brazing copper to mild and stainless steel using
copper-phosphorus-tin pastes. Welding journal.
65(4): 43–46.
275
AWS WELDING HANDBOOK
CHAPTER
C H A P T E4 R
9
NICKEL AND
COBALT ALLOYS
Prepared by the
Welding Handbook
Chapter Committee
on Nickel and Cobalt
Alloys:
H. J. White, Chair
CB&I
M. L. Caruso
Special Metals Welding
Products Company
R. Collier
VDM Metals USA, LLC
L. D. Paul
Kennametal Stellite
R. R. Pfouts
Wall Colmonoy Corporation
M. X. Yao
VDM Metals USA, LLC
Welding Handbook
Volume 5 Committee
Member:
S. P. Moran
Weir American Hydro
Contents
Introduction
Physical and
Mechanical Properties
Alloy Groups
Surface Preparation
for Welding
Arc Welding
Other Welding
Processes
Fabrication for HighTemperature Service
Weld Cladding
Brazing
Soldering
Thermal Cutting
Applications
Safe Practices
Bibliography
Supplementary
Reading List
Photograph courtesy of PCC Energy Group—Inconel Alloy 625 Surfacing Is Applied to the
Inner Diameter of an API X65 Pipe for Use in the Offshore and Onshore Oil and Gas Industry
276
277
278
289
290
315
323
327
338
342
343
344
347
349
349
276
AWS WELDING HANDBOOK
CHAPTER 4
NICKEL AND
COBALT ALLOYS
INTRODUCTION
Nickel and cobalt alloys provide unique combinations of physical and mechanical properties and exceptional resistance to corrosion attack. If the need for
these extraordinary properties were not critical to a
variety of industrial applications, these alloys probably
would not be manufactured because of high cost.
Nickel and cobalt alloys resist corrosive attack in
various media at temperatures up to 1100°C (2000°F)
and maintain good mechanical strength in both lowtemperature and high-temperature environments. For
use in these demanding service conditions, welds in
nickel and cobalt must duplicate the attributes of the
base metal to a very high degree; thus, conditions for
welding, heat treating, and fabrication procedures must
be established with these attributes included.
High-quality weldments are readily produced in
nickel-base and cobalt-base alloys by commonly used
welding processes, although not all processes are applicable to every alloy. Metallurgical characteristics or the
unavailability of matching or suitable welding filler
metals and fluxes may limit the choice of welding
processes.
Welding procedures for nickel and cobalt alloys are
similar to those used for stainless steel, except that the
molten weld metal is more sluggish, which requires
more accurate placement of the weld metal in the joint.
The thermal expansion characteristics of nickel and
cobalt alloys approximate those of carbon steel but they
are more favorable than those of stainless steel. Warping and distortion during welding is not severe.
The mechanical properties of nickel-base and cobaltbase metals vary, depending on the amount of hot work
or cold work applied to the finished form (sheet, plate,
or tube). Some modifications in the welding procedures
can be made if the base metal is not in the fully
annealed condition.
The properties of welded joints in fully annealed
nickel and cobalt alloys should be similar to those of
the base metals. Post-weld treatment is usually not
needed to maintain or restore corrosion resistance in
most nickel and cobalt alloys.
Welds made in nickel-molybdenum Alloy B
(N10001) and nickel-silicon cast alloys are commonly
solution annealed after welding to restore corrosion
resistance to the heat-affected zone (HAZ).1, 2 Rapid
cooling from the solution annealing temperature is necessary to avoid formation of detrimental metallurgical
phases, which can have an effect on mechanical properties and corrosion resistance.
Filler metals that are more highly alloyed than the
base metals are often used (sometimes in lieu of postweld heat treatment) to fabricate components for service in very aggressive corrosive environments. The
overmatching composition offsets the effects of weld
metal segregation that occurs when a matching composition is used. Examples are the use of nickel-chromium-molybdenum NiCrMo-14 (N06686) filler metal
to weld the super austenitic stainless steel alloys (those
containing 4% to 6% molybdenum) and Alloy C-276
(N10276) base metal. Nickel and nickel-alloy filler
metal designations for welding electrodes for shielded
metal arc welding and bare welding electrodes and rods
1. Welding terms and definitions used throughout this chapter are
from American Welding Society (AWS) Committee on Definitions
and Symbols, 2010, Standard Welding Terms and Definitions,
Including Terms for Adhesive Bonding, Brazing, Soldering, Thermal
Cutting, and Thermal Spraying, AWS A3.0M/A3.0:2010, Miami:
American Welding Society.
2. At the time this chapter was prepared, the referenced codes and
other standards were valid. If a code or other standard is cited without a date of publication, it is understood that the latest edition of the
referenced document applies. If a code or other standard is cited with
the date of publication, the citation refers to that edition only, and it
is understood that any future revisions or amendments to the code are
not included; however, as codes and standards undergo frequent revision, the reader should to consult the most recent edition.
AWS WELDING HANDBOOK
in this chapter are based on American Welding Society
specifications.3, 4
Post-weld heat treatment may be required for precipitation-hardening (also called age hardening) in specific
alloys. Post-weld stress relief may be necessary to avoid
stress-corrosion cracking in applications involving
hydrofluoric acid vapor or certain caustic solutions. For
example, nickel-copper Alloy 400 (N04400) immersed
in hydrofluoric acid is not sensitive to stress-corrosion
cracking, but becomes sensitive when exposed to the
aerated acid or the acid vapors
Most of the commonly used joining processes are
appropriate for nickel and cobalt alloys. The choice of
welding process should be based on the following
parameters:
1. The specific alloy to be welded;
2. Thickness of the base metal;
3. Design requirements of the structure (i.e.,
temperature, pressure, and type of stresses);
4. Welding position;
5. Need for fixtures and positioners; and
6. Service conditions and environment.
PHYSICAL AND MECHANICAL
PROPERTIES
Nickel has a face-centered cubic (FCC) structure up
to the melting point. Nickel can be alloyed with a number of elements without forming detrimental metallurgical phases. Some aspects of nickel are notably similar to
iron, as indicated by the proximity of nickel to iron in
the periodic table. Nickel is only slightly denser than
iron and has similar magnetic and mechanical properties. The crystalline structure of pure nickel, however, is
quite different from that of iron at room temperature.
3. Welding electrodes (e.g., ENiCrMo-14) for shielded metal arc
welding are specified in American Welding Society (AWS) Committee
on Filler Metals and Allied Materials, 2011, Specification for Nickel
and Nickel-Alloy Welding Electrodes for Shielded Metal Arc Welding, AWS A5.11/A511: 2011, Miami: American Welding Society.
Bare welding electrodes and rods (ERNiCrMo-14) are specified in
American Welding Society (AWS) Committee on Filler Metals and
Allied Materials, 2011, Specification for Nickel and Nickel-Alloy
Bare Welding Electrodes and Rods, AWS A5.14/A514M:2011,
Miami: American Welding Society. In usages that may apply with
either product form, the E or ER prefix may be omitted (e.g., filler
metal NiCrMo-14).
4. Base metal and alloy identifications in this chapter are based on
descriptions from Standard Practice for Numbering Metals and
Alloys in the Unified Numbering System (UNS), ASTM E527-07. The
UNS numbers appear parenthetically following identification numbers, e.g., Alloy 686 (N06686). Refer to Table 4.2.
CHAPTER 4—NICKEL AND COBALT ALLOYS
277
Therefore, the metallurgy of nickel and nickel alloys
differ from those of iron alloys.
Cobalt, unlike nickel, exhibits two crystallographic
forms and undergoes a transition from the FCC structure at temperatures higher than 417°C (782°F) to a
hexagonal close-packed (HCP) structure at temperatures lower than 417°C (782°F). On cooling, the transformation, which involves the coalescence of stacking
faults, is extremely sluggish, and at room temperature
the metal is typically in the metastable FCC form.
At room temperature, the transformation is easily
triggered by mechanical stress. The addition of certain
elements, such as nickel, iron, and carbon (within the
solubility range), suppresses the transformation temperature and stabilizes the FCC form. Conversely, additions of chromium, molybdenum, tungsten, and silicon
have the opposite effect. In the solution-annealed condition, wrought cobalt alloys exhibit the FCC structure.
With the exception of Alloy 188 (R30188), which is
FCC stable, the various cobalt alloys are metastable at
room temperature and tend to transform to the HCP
structure under the action of mechanical stress or during heat treatment (at temperatures below the transformation temperature).
Typical physical and mechanical properties for pure
nickel and pure cobalt are noted in Table 4.1.
Because nickel is readily soluble with a number of
other metals, many different commercial alloys are
available. Nickel and copper have complete solid solubility. Iron and cobalt are soluble in nickel to a very
high degree. The limit of solubility of chromium in
nickel is 35% to 40% and in molybdenum is about
20%. Additions of the major alloying elements—
copper, chromium, molybdenum, iron, and cobalt—
have no adverse effect on weldability, and in most
cases, additions of these elements have a beneficial
effect on weldability. In general, commercially pure
nickel and nickel-copper alloys have similar weldability.
Most of the other nickel alloys respond to welding in
the same way as stainless steel alloys.
Like austenitic stainless steels, nickel alloys have one
crystalline structure up to the melting point. Because
the nickel alloys do not undergo a phase change, the
grain size of the base metal or weld metal cannot be
refined by heat treatment alone. The grain size can be
reduced only by hot working or cold working, such as
rolling or forging, followed by an appropriate annealing treatment. The nominal chemical composition of
typical nickel alloys are provided in Table 4.2. Table
4.3 provides this information for cobalt alloys. Table
4.4(A) lists physical and mechanical properties of various nickel alloys in metric units; Table 4.4(B) lists U. S.
Customary units.
Relatively few cast and wrought cobalt alloys are
available in forms that can be easily fabricated. The
cobalt alloys that are commonly welded typically con-
278
CHAPTER 4—NICKEL AND COBALT ALLOYS
AWS WELDING HANDBOOK
Table 4.1
Physical and Mechanical Properties of Pure Nickel and Pure Cobalt
Property
Units
Nickel
Cobalt
Density
g/cm3 (lb/in.3)
8.902 (0.321)
8.85 (0.320)
Melting Point
°C (°F)
1453 (2647)
1493 (2719)
Coefficient of thermal expansion
μm/(m·°C) [μin./(in.·°F)]
13.3 (7.4)
13.8 (7.7)
Thermal conductivity
W/(m·K) [Btu/(hr·ft·°F]
92 (53)
69 (40)
Electrical resistivity
μΩ·cm (Ω/cir mil/ft)
6.8 (41)
5.3 (32)
Modulus of elasticity in tension
kPa (psi)
207 × 106 (30 × 106)
211 × 106 (30.6 x 106)
Tensile Strength, annealed
MPa (ksi)
317 (46)**
800–875 (116–127)*
Yield strength, 0.2% offset
MPa (ksi)
59 (8.6)**
305–345 (44–50)*
Elongation in 51 mm (2 in.)
percent
30**
15–30*
*Vacuum melted, hot worked and annealed between 800°C–1000°C (1470°F–1830°F). Air melted materials are less ductile.
**Annealed. Suitable hot rolling, annealing and cold work can yield tensile strengths as high as 1103 MPa (160 ksi).
Source: ASM Specialty Handbook—Nickel, Cobalt, and their Alloys.
tain two or more of the elements nickel, chromium,
tungsten, and molybdenum. The weldability of these
alloys is generally good.
In relatively small amounts, alloying elements, such
as manganese, silicon, niobium, carbon, aluminum, and
titanium, are not detrimental to the welding of nickel or
cobalt alloys. When a small percentage of elements (i.e.,
aluminum or titanium) are added to facilitate precipitation hardening, it is imperative to provide good shielding of the weld zone to limit the formation of oxides.
The weldability of nickel alloys and cobalt alloys can
be affected by residual elements, such as sulfur, lead,
zirconium, boron, phosphorous, and bismuth. These
elements are practically insoluble in nickel and cobalt
alloys, and can undergo eutectic reactions that can
cause hot cracking during solidification of the weld. All
commercially important nickel and cobalt alloys have
specification limits governing some of the elements that
are difficult to control. Boron and zirconium, in very
small amounts, can be added to certain alloys to
improve high-temperature performance, however, weldability is diminished when such additions are made. The
adverse effects of sulfur on ductility can be controlled
by the addition of small amounts of magnesium to
wrought product forms and to filler metals.
When using covered electrodes in shielded metal arc
welding (SMAW), the loss of magnesium across the arc
is so great that small amounts of magnesium recovered
in the weld metal is ineffective in offsetting the adverse
effects of sulfur. Under these circumstances, control of
sulfur is accomplished by adding manganese and niobium, which can be recovered in substantially greater
amounts than the amount that can be recovered from
magnesium.
Fusion welds made without the addition of filler
metal in nickel, nickel-copper alloys, and nickel-molybdenum alloys can develop porosity if the welds are contaminated by oxygen, nitrogen, or carbon monoxide.
Porosity can be prevented by using a matching filler
metal. The titanium and other gas-stabilizing elements
present in the filler metal combine with gas contaminants to prevent porosity. Typically, the weld-metal
composition differs from the base-metal composition to
improve weldability.
Mechanized or automatic welding processes are recommended for autogenous welding, but only under
closely controlled conditions. It is generally advisable to
add filler metal, even if in small amounts, because weld
quality is more predictable with additives in the filler
metal wire that fix, stabilize, or control gas and residual
elements.
ALLOY GROUPS
The various nickel and cobalt alloys (refer to Table
4.1 through Table 4.5) can be classified into the
following four groups:
1.
2.
3.
4.
Solid-solution-strengthened alloys,
Cast alloys,
Precipitation-hardenable alloys, and
Dispersion-strengthened alloys.
In addition to the four groups, the iron-base alloys
described in Table 4.5 contain large percentages of
three elements: nickel, cobalt, and chromium, or in
AWS WELDING HANDBOOK
CHAPTER 4—NICKEL AND COBALT ALLOYS
279
Table 4.2
Nominal Chemical Composition of Typical Nickel Alloys
Alloya
UNS
Number
Composition, wt %
Nib
C
Cr
Mo
Fe
Co
Cu
Al
Ti
Nbc
Mn
Si
W
B
Other
—
Commercially Pure Nickels
200
N02200
99.5
0.08
—
—
0.2
—
0.1
—
—
—
0.2
0.2
—
—
201
N02201
99.5
0.01
—
—
0.2
—
0.1
—
—
—
0.2
0.2
—
—
205
N02205
99.5
0.08
—
—
0.1
—
0.08
—
0.03
—
0.2
0.08
—
—
—
0.05Mg
Solid-Solution Alloys
400
N04400
66.5
0.2
—
—
1.2
—
31.5
404
N04404
54.5
0.08
—
—
0.2
—
44
R-405
N04405
66.5
0.2
—
—
1.2
—
X
N06002
47
0.10
22
9
18
NICR 80
N06003
76
0.1
20
—
1
NICR 60
N06004
57
0.1
16
—
bal.
G
N06007
44
0.1
22
6.5
C-22
N06022
56
0.010d
22
602CA
N06025
63
0.20
25
13
—
—
—
—
1
0.2
—
—
0.03
—
—
0.05
0.05
—
—
—
—
31.5
—
—
—
0.1
0.02
—
—
—
1.5
—
—
—
—
1
1
0.6
—
—
—
—
—
—
—
2
1
—
—
—
—
—
—
—
—
1
1
—
—
—
20
2.5
2
—
—
2
1.5
1
1
—
3
2.5d
—
—
—
—
0.5d
0.08d
3
—
0.35Vd
9
—
0.10d 2.1
0.08Y, 0.07Zr
15
5d
2
—
2d
—
—
0.4d
1.5d
0.3d
—
—
0.1d
0.5d
—
—
—
1.5d
1.5d
1d
2.5
—
—
—
—
0.5d
0.6d
—
—
—
0.25
—
—
0.5d
0.10d
—
—
—
0.15
G-30
N06030
43
0.03d
30
5.5
G-35
N06035
bal
0.05d
33
8
59
N06059
59
0.01d
23
16
IN 102
N06102
68
0.06
15
3
7
—
—
0.4
0.6
3
—
3
0.005
0.03Zr, 0.02Mg
C-2000
N06200
bal
0.01d
23
16
3d
—
1.6
0.5d
—
—
0.5
0.08d
—
—
—
230
N06230
57
0.10
22
2
3d
5d
—
0.3
—
—
0.5
0.4
14
RA 333
N06333
45
0.05
25
3
—
—
—
1
1.5
1.2
3
—
—
C-4
N06455
65
0.01d
16
15.5
3d
2d
—
—
—
—
1d
0.08d
—
—
—
600
N06600
76
0.08
15.5
—
8
—
0.2
—
—
—
0.5
0.2
—
—
—
14
3
601
N06601
60.5
0.05
23
—
617
N06617
52
0.07
22
9
18
1.5
—
0.015d 0.02La
—
—
1.4
—
—
0.5
0.2
—
—
—
12.5
—
1.2
0.3
—
0.5
0.5
—
—
—
622
N06622
59
0.005
20.5
14.2
2.3
—
—
—
—
—
—
3.2
—
—
625
N06625
61
0.05
21.5
9
2.5
—
—
0.2
—
0.2
3.6
0.2
0.2
—
—
—
S
N06635
67
0.02d
16
15
3d
2d
—
0.25
—
—
0.5
0.4
1d
16.3
0.015d 0.02La
686
N06686
58
0.005
20.5
1.5
—
—
—
—
—
—
—
3.8
—
—
690
N06690
60
0.02
30
—
9
—
—
—
—
—
0.5d
0.5d
—
—
—
G-3
N06985
44
0.015d
22
7
19.5
5d
2.5
—
—
0.5d
1d
1d
1.5d
—
—
825
N08825
42
0.03
21.5
3
30
—
2.25 0.1
0.9
—
0.5
0.25
—
—
—
B
N10001
61
0.05
1
28
5
2.5
—
—
—
—
1
1
—
—
—
N
N10003
70
0.06
7
16.5
5
—
—
—
—
—
0.8
0.5
—
—
—
W
N10004
60
0.12
5
24.5
5.5
2.5
—
—
—
—
1
1
—
—
C-276
N10276
57
0.01d
15.5
16
5
2.5d
—
—
0.7d
—
1d
0.08d
4
—
B-2
N10665
69
0.01d
1d
28
2d
1d
—
—
—
—
1d
0.1d
—
—
—
B-3
N10675
65d
0.01d
1.5
3d
—
0.5d
0.2d
—
3d
0.1d
3d
—
—
HR-160
N12160
37
0.05
28
1.0d
2d
—
—
0.5
1d
0.5
2.75
1d
—
—
301
N03301
96.5
0.15
—
—
0.3
0.6
—
0.25
0.5
—
—
—
1.5
28.5
29
0.13 4.4
(Continued)
—
0.35Vd
280
CHAPTER 4—NICKEL AND COBALT ALLOYS
AWS WELDING HANDBOOK
Table 4.2 (Continued)
Nominal Chemical Composition of Typical Nickel Alloys
Alloya
UNS
Number
Composition, wt %
Nib
C
Cr
Mo
Fe
Co
Cu
Al
Ti
Nbc
Mn
Si
W
B
Other
—
0.08
0.2
—
—
—
Precipitation-Hardenable Alloys
K-500
66.5
0.10
—
—
1
Waspaloy N07001
58
0.08
19.5
R-41
N07041
55
0.10
19
4
—
10
1
80A
N07080
76
0.06
19.5
—
90
N07090
59
0.07
282
N07208
57
0.06
19.5
20
214
N07214
75
0.10
16
M 252
N07252
C-263
N07263
55
0.15
20
50
0.06
20
5.8
U-500
713Ce
N07500
54
0.08
18
4
718
N07713
74
0.12
12.5
N07718
52.5
0.04
19
725
N07725
73
0.02
15.5
740
N07740
bal
0.03
X750
N07750
73
0.04
706
N09706
41.5
901
N09901
C 902
N09902
945
242
IN
100e
N05500
29.5
2.7
0.6
13.5
—
1.3
3
—
—
—
—
0.006
10
—
1.5
3
—
0.05
0.1
—
0.005
—
—
—
1.6
2.4
—
0.3
0.3
—
0.006
0.06Zr
—
—
16.5
—
1.5
2.5
—
0.3
0.3
—
0.003
0.06Zr
8.5
1.5d
10
—
1.5
2.1
—
0.3d
0.15d
—
0.005
—
3
—
—
4.5
—
—
0.5d
0.2d
—
0.01d
—
10
—
1
2.6
—
0.5
0.5
—
0.005
0.7d
20
0.2d
0.5
2.2
—
0.6d
0.4d
—
0.005d
—
18.5
—
2.9
2.9
—
0.5
0.5
—
0.006
0.05Zr
4
—
—
—
6
0.8
2
—
—
—
0.012
0.10Zr
3
18.5
—
—
0.5
0.9
5.1
0.2
0.2
—
—
—
—
2.5
—
—
0.7
2.5
1.0
—
—
—
—
—
25
0.5
0.7
20
—
0.9
1.8
2.0
0.3
0.5
—
—
—
15.5
—
7
—
—
0.7
2.5
1
0.5
0.2
—
—
—
0.03
16
—
40
—
—
0.2
1.8
2.9
0.2
0.2
—
—
—
42.5
0.05
12.5
—
36
6
—
0.2
2.8
—
0.1
0.1
—
0.015
—
42.2
0.03
5.3
—
48.5
—
—
0.6
2.6
—
0.4
0.5
—
—
—
N09945
50
0.02
22.5
3.5
—
—
2.5
0.4
1.5
3
0.5
0.25
—
—
—
N10242
65
0.03
8
25
2d
1d
0.5d
0.5d
—
—
0.8d
0.8d
—
0.006d
N13100
60
0.18
10
3
—
—
5.5
4.7
—
—
—
—
0.014
10
15
0.06Zr
—
—
0.01Y, 0.1Zrd
—
—
0.06Zr,1.0V
Dispersion-Strengthened Alloys
TD Nickel N03260
98
—
—
—
—
—
—
—
—
—
—
—
—
—
2 Th O2
TD NICR
78
—
20
—
—
—
—
—
—
—
—
—
—
—
2 Th O2
N07754
a. Several of these designations are registered trade names; some designations relate to portions of a trade name. These and similar alloys may be known by
other designations and trade names. Designations with UNS numbers in the N07XXX series are age hardenable.
b. Includes small amount of cobalt, if cobalt content is not specified.
c. Includes tantalum (Nb+Ta).
d. Maximum value.
e. Casting alloys.
some instances, they may contain only two of these elements. The weldability characteristics of the iron-base
alloys containing chromium closely resemble those of
the heat-resisting grades of nickel and cobalt alloys.
Figure 4.1 shows a comparison of the stress-rupture
strength of iron-nickel-chromium Alloy 800HT
(N08811) and the filler metals ERNiCrCoMo-1
(N06617) and ENiCrCoMo-1 (W86117). Although the
compositions of these filler metals do not match the
base metal, the strength gained by overmatching makes
them good choices for service at high temperatures.
These filler metals also provide better resistance to oxidation at the elevated temperature than the base metal.
At exposure temperatures lower than 760°C (1400°F),
other filler metals, such as ERNiCr-3 (N06082) and
ENiCrFe-2 (W86133) are recommended. This example
is typical of many recommendations for filler metals
when service conditions are determining factors.
AWS WELDING HANDBOOK
CHAPTER 4—NICKEL AND COBALT ALLOYS
281
Table 4.3
Nominal Chemical Compositions of Typical Cobalt Alloys
Composition, wt %
Alloya
UNS
Number
C
Ni
Cr
Co
W
Ta
Mo
Al
Ti
Fe
Mn
Si
B
Zr
Other
—
—
3b
1.5
0.5
—
—
—
0.08 La
Wrought Alloys
L-605
R30605
0.1
10
20
Bal
15
—
—
188
R30188
0.1
22
22
Bal
—
—
—
—
3b
1.2
0.4
—
—
MP 35N
R30035
0.05
35
20
35
—
—
10
—
—
—
—
—
—
—
—
S-816
R30816
0.38
20
20
Bal
4
—
4
—
—
4
1.2
0.4
—
—
4 Nb
54Co-26Cr
R31233
0.06
9
26
Bal
2
—
5
—
—
3
0.8
0.3
—
—
0.08 N
14
Cast Alloys
27
Bal
—
—
5.5
—
—
2b
—
—
—
—
10.5
25.5
Bal
7.5
—
—
—
—
—
0.75
0.75
—
—
—
10
29
Bal
7.5
—
—
—
—
1
—
—
0.01
—
—
—
21
Bal
11
—
—
—
—
2
0.25
0.25
—
—
2 Nb
—
21.5
Bal
10
9
—
—
—
—
—
—
0.005
0.2
—
23.5
Bal
7
3.5
—
—
2
—
—
—
—
0.5
—
26
54
2
—
5
—
—
3
0.8
0.3
—
—
—
21
R30021
0.25
2.5
X-40
R30031
0.5
FSX-414
—
0.25
WI 52
—
0.45
MAR-M 302
—
0.85
MAR-M 509
—
0.6
10
R31233
0.06
9
ULTIMET
a. Several of these designations are registered trade names; some designations relate to portions of a trade name. These and similar alloys may be known by
other designations and trade names.
b. Maximum.
SOLID-SOLUTION-STRENGTHENED
ALLOYS
All nickel alloys are strengthened by solid solution.
Additions of aluminum, chromium, cobalt, copper,
iron, molybdenum, titanium, tungsten, and vanadium
contribute to solid-solution strengthening. Of these,
aluminum, chromium, molybdenum, and tungsten contribute substantially to solid-solution strengthening; the
others have less effect. Molybdenum and tungsten
improve strength at elevated temperatures.5
Pure Nickel
Nickel 200 (N02200) and the low-carbon version,
Nickel 201 (N02201), are most widely used when welding is involved. Nickel 201 is preferred for applications
5. Refer to Chapter 4, Welding Metallurgy, of American Welding
Society (AWS) Welding Handbook Committee, 2001, Welding Science
and Technology, ed. C. Jenney and A. O’Brien, vol. 1, Welding Handbook, 9th ed., Miami: American Welding Society. See Appendix B of
this volume for a detailed description of chapter contents of the five
volumes of Welding Handbook, 9th ed.
that will be exposed to service temperatures higher than
315°C (600°F) because it provides increased resistance
to graphitization at elevated temperatures. Graphitization is the result of excess carbon precipitation that
occurs intergranularly in the temperature range of
315°C to 760°C (600°F to 1400°F) when Nickel 200 is
held in this range for an extended time. Nickel 200 and
Nickel 201 are most often used to fabricate equipment
for food processing and the handling of caustics, and for
items such as drums for shipping chemicals, laboratory
crucibles, and electrical and electronic components.
Nickel-Copper Alloys
Nickel and copper alloys form a continuous series of
solid solutions with face-centered cubic crystal structures.
The principal alloys in this group are Alloy 400
(N04400) and the free-machining version of it, R-405
(N04405). These alloys provide high strength and
toughness and are industrially important primarily
because of resistance to corrosion. They have excellent
resistance to sea water or brackish water, chlorinated
solvents, glass-etching agents, sulfuric acids, and many
other acids and alkalis.
282
CHAPTER 4—NICKEL AND COBALT ALLOYS
AWS WELDING HANDBOOK
Table 4.4(A)
Typical Physical and Mechanical Properties of Nickel Alloys
(Metric Units)
Alloy
HR-120
200
201
400
R-405
K-500
502
X
G
602CA
G-30
G-35
A59
C-2000
600
601
625
Waspaloy
R-41
282
C-263
U-500
713C
718
740
X-750
20Cb3
800
825
706
901
945
B
N
W
242
C-276
B-3
HR-160
a.
b.
c.
d.
e.
UNS
Number
Density,
kg/m3
Melting
Range,
°C
N00820
N02200
N02201
N04400
N04405
N05500
N05502
N06002
N06007
N06025
N06030
N06035
N06059
N06200
N06600
N06601
N06625
N07001
N07041
N07208
N07263
N07500
N07713
N07718
N07740
N07750
N08020
N08800
N08825
N09706
N09901
N09945
N10001
N10003
N10004
N10242
N10276
N10675
N12160
8070
8885
8885
8830
8830
8470
8442
8221
8304
7900
8220
8220
8600
8500
8415
8055
8442
8193
8249
8290
8400
8027
7916
8193
8050
8248
8083
7944
8138
8055
8221
8200
9245
8858
8996
9050
8941
9220
8080
1300
1435–1446
1435–1446
1298–1348
1298–1348
1315–1348
1315–1348
1260–1354
1260–1343
1370–1400
—
1332–1361
1310–1360
1328–1358
1354–1412
1301–1367
1287–1348
1402–1413
1315–1371
1300–1375
1300–1360
1301–1393
1260–1287
1260–1336
1288–1362
1393–1426
1370–1425
1357–1385
1371–1398
1334–1370
—
1270–11377
1301–1368
1301–1398
1315
1290–1375
1265–1343
1370–1418
1293–1370
Heat-treated condition
93°C
As cast
149°C
Limiting property: heat treated and aged
Coefficient
of Thermal
Thermal
Expansion at Conductivity
21°C–93°C,
at 21°C,
μm/(m·°C)
W/(m·K)
14.3
13.3
13.3
13.9
13.9
13.7
13.7
13.9
13.5
11.9
12.8
12.3
11.9
12.4
13.3
13.7
12.8
12.2
11.9
12.1
10.7
12.2
10.6
13.0
12
12.6
14.9
14.2
14.0
14.0
13.0
14.19
10.1
11.5
11.3
10.8
11.3
10.6
13
11.4
70
79
20
20
16
16
8
13
11
10.2
10
10
9.1
14
12
9
12
11d
10.3
11
12
19b
11
10
11
—
11
10
12
—
10.9
11
11
—
11.3
11
11.2
10.9
Electrical
Resistivity
at 21°C,
μΩ·cm
105.2
9.5
7.6
51.0
51.0
61.5
61.5
118.3
—
118
116
118
126
128
103.0
120.5
129.0
126.5
136.3
126.1
115
120.2
—
124.9
117
121.5
103.9
98.9
112.7
98.4
110.0
110
134.8
138.8
—
122
129.5
137
111.2
Tensile
Modulus
of Elasticity,
21°C, GPa
197
204
207
179
179
179
179
197
192
215
202
204
210
207
207
206
207
211
215
213
223
214
206
205
221
214
193
196
193
210
193
195
179
216
—
229
205
216
211
Tensile
Yield
Strength
Strength
at Room
at Room,
Temperature, Temperature,
MPa
MPa
735
469
379
552
552
965a
896
786
710
721
690
745
670
786
621
738
896
1276a
1103a
1152a
1034
1213a
848c
1310a
1169a
1172a
621
621
621
1207a
1207
1034e
834
793
848
1330a
834
860
767
375
172
138
276
241
621a
586
359
386
348
317
348
330
400
276
338
483
793a
827a
705a
620
758a
738c
1103a
721a
758a
276
276
276
1000a
896
862e
393
310
365
868a
400
420
314
AWS WELDING HANDBOOK
CHAPTER 4—NICKEL AND COBALT ALLOYS
283
Table 4.4(B)
Typical Physical and Mechanical Properties of Nickel Alloys
(U.S. Customary Units)
Alloy
HR-120
200
201
400
R-405
K-500
502
X
G
602CA
G-30
G-35
59
C-2000
600
601
625
Waspaloy
R-41
282
C-263
U-500
713C
718
740
X-750
20Cb3
800
825
706
901
945
B
N
W
242
C-276
B-3
HR-160
a.
b.
c.
d.
e.
UNS
Number
Density,
lb/cu. in.
Melting
Range,
°F
N00820
N02200
N02201
N04400
N04405
N05500
N05502
N06002
N06007
N06025
N06030
N06035
N06059
N06200
N06600
N06601
N06625
N07001
N07041
N07208
N07263
N07500
N07713
N07718
N07740
N07750
N08020
N08800
N08825
N09706
N09901
N09945
N10001
N10003
N10004
N10242
N10276
N10675
N12160
0.291
0.321
0.321
0.319
0.319
0.306
0.305
0.297
0.300
0.285
0.297
0.297
0.311
0.307
0.304
0.291
0.305
0.296
0.298
0.299
0.302
0.290
0.286
0.296
0.291
0.298
0.292
0.287
0.294
0.291
0.297
0.296
0.334
0.320
0.325
0.327
0.323
0.333
0.292
2375
2615–2635
2615–2635
2370–2460
2370–2460
2400–2460
2400–2460
2300–2470
2300–2450
2500–2550
—
2430–2482
2390–2480
2422–2476
2470–2575
2374–2494
2350–2460
2556–2576
2400–2500
2370–2510
2370–2480
2375–2540
2300–2350
2300–2437
2350–2484
2540–2600
2498–2597
2475–2525
2500–2550
2434–2499
—
2317–2510
2375–2495
2375–2550
2400
2350–2510
2310–2450
2500–2585
2360–2500
Heat-treated condition
At 200°F
As cast
At 300°F
Limiting property: heat treated and aged
Coefficient
of Thermal
Thermal
Electrical
Expansion at Conductivity Resistivity
70°F–200°F,
at 70°F,
at 70°F,
μin./(in.·°F) Btu/(ft·h·°F) Ω cir mil/ft
7.95
7.4
7.4
7.7
7.7
7.6
7.6
7.7
7.5
6.6
7.1
6.8
6.6
6.9
7.4
7.6
7.1
6.8
6.6
6.7
6.0
6.8
5.9
7.2
6.8
7.0
8.3
7.9
7.8
7.8
7.2
7.9
5.6
6.4
6.3
6
6.3
5.7
7.2
6.5
43
46
13
13
10
10
5
8
8
5.9
5.8
7
5.3
9
7
6
8
7d
6
7
8
12b
6
6.1
7
—
7
6
7
—
7.59
7
7
—
6.3
6
6.5
6.25
497
57
46
307
307
370
370
712
—
710
548.4
558
758
607.2
620
725
776
761
820
596.4
692
723
—
751
702.7
731
625
595
678
592
662
663
811
835
—
576
779
645.6
525.6
Tensile
Modulus
of Elasticity,
70°F, 106 psi
28.6
29.6
30.0
26.0
26.0
26.0
26.0
28.6
27.8
31.2
29.3
29.6
30.5
30
30.0
29.9
30.0
30.6
31.2
31.5
32.3
31.0
29.9
29.8
32
31.0
28.0
28.5
28.0
30.4
28.0
28.3
25.9
31.3
—
28.6
29.8
31.4
30.6
Tensile
Yield
Strength
Strength
at Room
at Room
Temperature, Temperature,
ksi
ksi
106
68
55
80
80
140a
130
114
103
105
103
102
97
105
90
107
130
185a
160a
164a
150a
176a
123c
190a
169.5a
170a
90
90
90
175a
175
150e
121
115
123
187.4a
121
125
112
50
25
20
40
35
90a
85
52
56
50
49
50
48
46.3
40
49
70
115a
120a
101a
90a
110a
107c
160a
104.5a
110a
40
40
40
145a
130
125e
57
45
53
122.4a
58
60.6
51
284
CHAPTER 4—NICKEL AND COBALT ALLOYS
AWS WELDING HANDBOOK
Table 4.5
Highly Alloyed Iron-Base Nickel Alloys
Nominal Composition, wt %
Alloya
UNS
Number
Nib
Cr
Co
Fe
Mo
Ti
W
Nbc
Al
C
Other
0.1
0.05
0.6Si, 0.004B, 0.7Mn, 0.2N
Solid-Solution Alloys
33
2.5e
—
2.5e
0.7
—
36
2.5
—
—
0.5
—
0.04
3.5 Cu,1 Mn, 0.5 Si
—
33
6.5
—
—
—
0.25
0.015e
1.2 Cu, 0.20N
—
45.1
—
—
—
—
—
0.05
—
21.0
—
45.7
—
0.40
—
—
0.40
0.05
—
20.5
—
46.3
—
1.13
—
—
—
0.05
—
32.5
21.0
—
44.8
—
0.75
—
—
0.58
0.35
—
33.0
21.0
—
45.8
—
0.50
—
—
0.50
0.08
N08926
25
20
—
45
6.5
—
—
—
—
0.02e
1.0 Cu, 0.20 N
33
R20033
31
33
—
32
1.2
—
—
—
—
0.015e
0.8 Cu, 0.5N
N-155
R30155
20.0
21.0
20.0
32.2
3.00
—
2.50
1.0
—
0.15
0.15 N
556
R30556
21.0
22.0
20.0
29.0
3.00
—
2.50
0.1
0.30
0.10
0.5 Ta, 0.02 La
19-9 DL
S63198
9.0
19.0
—
66.8
1.25
0.30
1.25
0.4
—
0.30
1.10 Mn, 0.60 Si
A-286
S66286
26.0
15.0
—
55.2
1.25
2.00
—
—
0.02
0.04
—
903
N19903
38.0
—
15.0
41.0
0.10
1.40
—
3.0
0.70
0.04
—
HR-120
N00820
37
25
20Cb3d
N08020
35
20
31
N08031
31
28
RA330
N08330
36.0
19.0
800
N08800
32.5
801
N08801
32.0
802
N08802
800HT
N08811
926
3e
—
Precipitation Hardenable
a. Several of these designations are registered trade names; some designations relate to portions of a trade name. These and similar alloys may be known by
other designations and trade names.
b. Includes small amount of cobalt, if cobalt content is not specified.
c. Includes tantalum, if tantalum content is not specified.
d. While niobium (Nb) is the preferred designation for the 41st element and is used as a column heading in the table, the abbreviation for the element’s alternate designation, columbium (Cb), is retained in this alloy designation until such time as the alloy designation is changed.
e. Maximum composition.
Nickel-copper alloys are readily joined by welding,
brazing, and soldering when recommended practices
are followed. Welding filler metals designed to improve
strength and to eliminate porosity in the weld metal differ somewhat in chemical composition. Welding without the addition of filler metal is not recommended for
use with manual gas tungsten arc welding (GTAW). A
few automatic or mechanized welding procedures do
not require the addition of filler metal.
Welding filler metals applicable to this alloy group
are also widely used in the welding of copper alloys.6
Nickel-Chromium Alloys
The nickel-chromium alloy group includes Alloys
600 (N06600), 601 (N06601), 602CA (N06025),
6. Refer to Chapter 3, Copper and Copper Alloys, in this volume.
690 (N06690), 214 (N07214), 230 (N06230), G-30
(N06030), and RA-333 (N06333).
Alloy 600 (the most commonly used nickel alloy) has
good corrosion resistance and good strength at elevated
temperatures. Alloy 600 is resistant to chloride-ion
stress-corrosion cracking, and it provides excellent
properties at room temperature and in cryogenic service. Alloy 690, with 30% chromium, has even better
resistance to stress-corrosion cracking.
Alloy 230, a nickel-chromium-tungsten-molybdenum
alloy, has excellent high-temperature strength and resistance to oxidizing and nitriding environments. Alloys
RA-333, 601, 602CA, and 214 provide outstanding
resistance to oxidation and scaling at temperatures up
to 1200°C (2200°F). These alloys extend the temperature range beyond that achieved with the nickel-chromium Alloy 600 by the addition of aluminum: 1.4% to
Alloy 601, 2.1% to Alloy 602CA, and 4.5% to Alloy
214.
AWS WELDING HANDBOOK
CHAPTER 4—NICKEL AND COBALT ALLOYS
285
100
760°C (1400°F)
100
STRESS, ksi
STRESS, MPa
10
982°C (1800°F)
10
1
ERNiCrCoMo-1 FILLER METAL (AWS A5.14/A5.14M)
ENiCrCoMo-1 FILLER METAL (AWS A5.11/A5.11M)
WROUGHT Fe-Ni-Cr ALLOY 800HT BASE METAL (UNS N08811)
1
100
1000
10 000
RUPTURE LIFE, h
Figure 4.1—Stress-Rupture Values of Selected Alloys at High Temperatures
Alloy G-30 with 30% chromium and Alloy 31 with
28% chromium provide superior corrosion resistance
to commercial phosphoric acids and similar highly oxidizing acids.
Filler metals NiCrMo-11 (G-30) and NiCrMo-13
(Alloy 59 [N06059]) are widely used to impart corrosion resistance when welding base metal alloys containing molybdenum.
Alloy 617 (N06617) is a nickel-chromium-cobaltmolybdenum-base metal combination that provides
metallurgical stability, strength, and oxidation resis-
tance at high temperatures. This alloy also provides corrosion resistance in aqueous environments.
The corresponding NiCrCoMo-1 filler metals used
for welding Alloy 617 base metal are also used to weld
other base metals intended for service in severe environments. For example, Alloy 800 base metal intended for
service in the 820°C to 1150°C (1500°F to 2100°F)
range is welded almost exclusively with NiCrCoMo-1
filler metal. Other filler metals can be used, but the
supplier should be consulted regarding specific service
conditions and suitability of such use. In general,
286
CHAPTER 4—NICKEL AND COBALT ALLOYS
weldability is outstanding for all of the nickel-chromium base metals.
Nickel-Iron-Chromium Alloys
Base metal Alloys 800 (N08800), 800HT (N08811),
825 (N08825), 20Cb3 (N08020), N-155 (R30155),
HR-120 (N08120), and 556 (R30556) are included in
the nickel-iron-chromium alloy group. Alloys 800,
800HT, N-155, HR-120, and 556 are generally preferred for high-temperature applications because they
provide strength at high-temperatures and resistance to
oxidation and carburization. Alloys 825 and 20Cb3 are
used in corrosive environments below 540°C (1000°F)
because they are resistant to reducing acids, HCl,
HsSO4, and also to chloride-ion stress-corrosion cracking.
Nickel-Iron-Chromium-Molybdenum
Alloys
Alloys 926 (N08926), 31 (N08031), and AL6XN
(N08367) are included in the nickel-iron-chromiummolybdenum alloy group. These alloys are used in corrosive environments where traditional stainless steels
are not adequate. All of these alloys are generally
welded with higher alloyed filler metals to maintain the
corrosion resistance of the welds.
Typically, nickel-chromium-molybdenum alloys (59
[N06059], C-276, C-22 [N06022]), 686CPT [N06686],
C-2000 [N06200], and 625 [N06625]) are used as weld
filler materials for the nickel-iron-chromium-molybdenum alloy category because they inherently provide
greater corrosion resistance.
Nickel-Molybdenum Alloys
The principal alloys in the nickel-molybdenum group
are Alloys B (N06004), B-2 (N10665), B-3 (N10675),
N (N10003), 242 (N10242), and W (N10004). These
alloys contain 16% to 28% molybdenum and smaller
amounts of chromium and iron. They are used primarily
for corrosion resistance and are not commonly used for
elevated-temperature service. They are readily weldable.
Alloys B, B-2, and B-3 have good resistance to
hydrochloric acid and other acids. Alloy N was developed for resistance to molten fluoride salts. Alloy W is
used in welding filler metals (NiMo-3 [N10004]) to
impart good corrosion and oxidation resistance.
Nickel-Chromium-Molybdenum Alloys
Included in the nickel-chromium-molybdenum base
metal group are Alloys C-22 (N06022), C-276 (N10276),
AWS WELDING HANDBOOK
59 (N06059), C-2000, G (N06007), S (N06003), X
(N06002), 622 (N06022), and 686 (N06686). They are
designed primarily for corrosion resistance at room
temperature and also for resistance to oxidizing and
reducing atmospheres. Alloy 625 has additions of 9%
molybdenum and 4% niobium, which enhance strength
and corrosion resistance at room temperature and high
temperature. Alloys X and S are widely used for hightemperature applications. All of these alloys have good
weldability, and filler metals suitable for welding them
are available.
Cobalt-Chromium-Nickel-Tungsten Alloys
The most notable alloys in the cobalt-chromiumnickel-tungsten base metal group are L-605 (R30605),
188, S-816 (R30816), and the 54Co-26Cr alloy
(R31233).
The loss in ductility that occurs with some cobalt
alloys in the temperature range of 650°C to 980°C
(1200°F to 1800°F) is characteristic of high-alloy compositions. This characteristic is believed to be associated
with the precipitation of carbides and intermetallic
compounds, which adversely affects resistance to cracking. The combination of minimum joint restraint and
low-energy input during welding makes welding possible with predictable results.
Contamination by molten copper will cause basemetal cracking in all of these alloys. Because the
wrought form of cobalt alloys is typically sheet, the use
of copper backing bars must be evaluated carefully.
Sometimes copper backing bars are nickel plated or
chromium plated, or an austenitic stainless steel backing bar is substituted for copper, although with a resultant loss in thermal conductivity.
CAST ALLOYS
In addition to the wrought form, some nickel alloys
are designed specifically for casting. The nominal chemical composition of several ASTM nickel-base casting
alloys are listed in Table 4.6. Refer to Table 4.3 for a
list of cobalt-base cast alloys.
Casting alloys, like wrought alloys, can be strengthened by solid-solution or precipitation-hardening methods. Precipitation-hardening alloys high in aluminum
content, such as Alloy 713C (N07713), will harden
during slow cooling in the mold and are generally considered unweldable by fusion processes; however, castings with surface defects and damage incurred during
service are frequently repaired by arc welding. It should
be understood that repair by fusion welding requires an
evaluation of the convenience of welding and the possibility of compromising cast strength and ductility during
welding.
AWS WELDING HANDBOOK
CHAPTER 4—NICKEL AND COBALT ALLOYS
287
Table 4.6
Nominal Chemical Composition of Standard ASTM Nickel Casting Alloys
Composition, wt %
Alloy
UNS
Number
Ni
C
Cr
Mo
Fe
Th
Al
Ti
Cu
Mn*
Si*
W
ASTM A 297-79*
HW
N08001
60
0.5
12
—
25
—
—
—
—
2.0
2.5
—
HX
N06006
66
0.5
17
—
15
—
—
—
—
2.0
2.5
—
CY-40
N06040
72
0.4*
16
—
—
—
—
—
1.5
3.0
—
ASTM A 494-79
11*
CW-12M-1
N30002
55
0.12*
16.5
17
6
—
—
—
—
1.0
1.0
4.5
CZ-100
N02100
95
1.0*
—
—
3*
—
—
—
1.25*
1.5
2.0
—
M-35-1
N24135
68
0.35*
—
—
3.5*
—
—
—
1.5
1.25
—
N-12M-1
N30012
65
0.12*
—
28
5
—
—
—
1.0
1.0
—
30
—
*Maximum.
Most nickel and cobalt cast alloys contain significant
amounts of silicon to improve fluidity and facilitate
casting. Most of these cast alloys are weldable by conventional means, but as the silicon content increases,
sensitivity to weld cracking also increases. This sensitivity can be avoided by using welding techniques that
minimize base metal dilution.
Nickel castings that are considered unweldable by
arc welding can be welded with the oxyacetylene process using a high preheating temperature.
Cast nickel alloys containing 30% copper are considered unweldable when the silicon exceeds 2% because
these alloys are sensitive to cracking; however, when
weldable-grade castings are specified, weldability is
quite good, and the resulting welds will pass pressure
tests and routine weld-metal inspections, such as radiographic examination and liquid-penetrant testing.
Cast cobalt alloys are used in the manufacture of gas
turbines and for other applications in which high
strength and good resistance to oxidation and sulfidation are needed. Refer to Table 4.3 for the composition
of some of these alloys. It should be noted that the silicon level of cast cobalt alloys is quite low, and weldability is considered good.
PRECIPITATION-HARDENING ALLOYS
The precipitation-hardening (age-hardening) alloys
are strengthened by controlled heating, which precipitates a second phase from a supersaturated solution.
Precipitation occurs on reheating a solution-treated and
quenched alloy to an appropriate temperature for a
specified time. Each alloy has an optimum thermal cycle
in which it achieves maximum strength in the finished
and aged condition. Some cast alloys age directly while
the solidified casting cools in the mold.
From a strengthening standpoint, the most important phase is the ordered face-centered cubic gamma
prime phase, which is based on the compound Ni3Al.
This phase has a high solubility for titanium and niobium; consequently, the composition will vary with the
base-metal composition and temperature of formation.
Aluminum has the greatest hardening potential, but this
is stabilized by titanium and niobium. Niobium
improves weldability, as it has the greatest effect on
decreasing the aging rate.
These alloys are normally welded in the solutiontreated (soft) condition. During welding, some portion
of the HAZ reaches the aging temperature range. As the
weld metal solidifies, the aging HAZ becomes subjected
to welding stresses. Under certain postweld combinations of temperature and stress, the HAZ of the weld
can crack. This is known as strain-age cracking. Alloys
that are high in aluminum content are the most prone
to this type of cracking. The problem is less severe when
niobium, which retards the aging action, is substituted
for a significant portion of the aluminum. Consequently, the HAZ of the weld can remain sufficiently
ductile and can yield during heat treatment to relieve
high welding stresses without rupture. The relative
weldability of several precipitation-hardening alloys is
shown in Figure 4.2. When weldability is a concern,
718 (NiFeCr-2) filler metal is usually selected.
288
CHAPTER 4—NICKEL AND COBALT ALLOYS
AWS WELDING HANDBOOK
ALLOY 713 C
6
IN 100
5
K-500
DE
IN G
IT Y
3
DA
WE
L
INC
RE
AS
2
1
CR
EA
WE
SIN
LD
G
AB
ILI
TY
4
U-500
B IL
ALUMINUM, %
301
R-41
80A
M252
718
WASPALOY
X-750
0
0
1
2
3
4
5
6
TITANIUM, %
Figure 4.2—Relationship between Estimated Weldability of
Precipitation-Hardening Nickel Alloys and the Aluminum and Titanium Content
Nickel-Copper Alloys
Nickel-Chromium Alloys
The principal alloy in the nickel-copper group is
K-500 (N05500). Strict attention to heat-treating procedures must be followed to avoid strain-age cracking.
The corrosion resistance of nickel-copper alloys is similar to the solid-solution Alloy 400. Alloy K-500 has
been in commercial existence for more than 50 years
and is routinely welded, using proper care, with the
GTAW process. Weld metal properties resulting from
the use of filler metals of matching composition seldom
develop 100% joint efficiency, thus a typical consideration by the designer is to locate the weld in an area of
low stress. Filler metal ERNiFeCr-2 (Alloy 718
[N07718]) has also been used to join this alloy, but an
evaluation of the service environment and the differing
aging temperatures between Alloy 718 and Alloy K-500
must be made. The base metal supplier should be consulted for applicable recommendations.
The nickel-chromium age-hardening alloys are
strengthened by either an aluminum-titanium reaction
or an aluminum-titanium-niobium reaction. Chromium, ranging from about 13% to 20%, is added to
ensure good high-temperature oxidation resistance.
Principal alloys in the aluminum-titanium group
that are difficult to weld include Alloys 713C (casting),
X-750 (N07750), U-500 (N07500), R-41 (N07041),
282 (N07208) 80A (N07080), 751 (N07751), and
Waspalloy (N07001). Alloys 718 and 706 (N09706)
are highly weldable because of the more sluggish
strengthening reaction of the aluminum-titaniumniobium alloying system. Examples of some of the highintegrity applications for these alloys are gas turbine
components, aircraft and spacecraft components, and
automotive parts, such as valves, in which the strengthto-weight relationship is important.
AWS WELDING HANDBOOK
CHAPTER 4—NICKEL AND COBALT ALLOYS
289
Nickel-Iron-Chromium Alloys
The principal alloy in the nickel-iron-chromium
group is Alloy 901 (N09901). The weldability of this
alloy is similar to Alloy X-750; however, most applications are in forgings that require little welding. When
welding is required, it is necessary to take the same precautions as those observed for other aluminum-titaniumhardened alloys to avoid strain-age cracking.
DISPERSION-STRENGTHENED NICKEL
Nickel and nickel-chromium alloys can be strengthened to very high levels by the uniform dispersion of
very fine refractory thorium oxide (ThO2) particles
throughout the alloy matrix, using powder metallurgy
techniques during the manufacture of the alloy. When
these metals are welded by fusion welding, the oxide
particles agglomerate during solidification. This
destroys the original strengthening brought about by
dispersion within the matrix and causes the deposited
weld metal to be significantly weaker than the base
metal. The high strength of these base metals can be
retained with processes that do not involve melting the
base metal. The base metal supplier should be consulted
for recommendations for specific welding conditions.
SURFACE PREPARATION
FOR WELDING
Cleanliness is the single most important requirement
for successful welding of nickel and cobalt alloys. At
high temperatures, these alloys are susceptible to
embrittlement caused by low-melting-point substances,
such as remnants of materials used in manufacturing
processes. A clean surface before welding is a prerequisite for all of the processes described in this chapter.
Nickel alloys and cobalt alloys are embrittled by sulfur, phosphorus, and metals with low melting points,
such as lead, zinc, and tin. Frequent sources of contamination are lead hammers, solders, and wheels or belts
that can be carriers of these materials. Detrimental elements are often present in oils, paint, marking crayons,
cutting fluids, and shop dirt.
Figure 4.3 shows an example of cracking in Nickel
200 sheet that was improperly cleaned with a contaminated rag prior to welding. When such embrittlement
occurs, the alloy is destroyed and cannot be reclaimed
by any kind of treatment. The contaminated area must
be removed mechanically, or by thermal cutting at a
Figure 4.3—Cracking from Sulfur
Contamination in the Heat-Affected
Zone of a Weld in Nickel Sheet
point not adjacent to the cracked area; then the surface
must be thoroughly cleaned before welding.
Many cases of contamination have been reported
when weldments in service must be repaired or modified by welding. It is particularly important that adequate attention be given to cleaning before applying
heat from any source. Chemicals used for processing
during prior service can also be sources of contamination. Figure 4.4 shows an example of sulfur and lead
embrittlement in nickel-copper Alloy 400 installed in a
vessel that had been used to process fatty acids. The
specimen was removed from the tank, which had been
previously lined with lead but was not properly cleaned
before the installation of a nickel-copper Alloy 400 lining.
The depth of attack varies with the type and level of
concentration of the embrittling element, the base
metal, the heating time, and the temperature. Nickel
200, for example, is easily embrittled, whereas ironnickel-chromium Alloy 800 is less sensitive to embrittlement. This information provides little remedy, however,
and the fundamental rule when welding nickel and
cobalt alloys is the following: unless proven harmless,
all foreign material must be considered harmful in the
presence of heat.
The use of copper backing bars when welding
cobalt-alloy sheet requires special attention. Contamination by even a minute amount of molten copper will
lead to liquid-metal stress-cracking in cobalt-base metals. For example, a small amount of copper inadvertently transferred onto the surface of a sheet from a
backing bar will cause severe cracking when melted by
the heat of welding. This can be prevented by plating
the backing bar with nickel or chromium, using a stain-
290
CHAPTER 4—NICKEL AND COBALT ALLOYS
Figure 4.4—Combined Effects of Sulfur and Lead
Contamination of a Weld in Nickel Sheet in a
Specimen Removed from a Fatty-Acid
Tank Previously Lined with Lead
AWS WELDING HANDBOOK
A process chemical such as a caustic that has been in
contact with the base metal for an extended period of
time can become embedded and require grinding, abrasive blasting, or swabbing with a 10 volume percent
(vol %) hydrochloric acid solution, followed by a thorough water wash. Safety precautions noted on the
safety data sheet (SDS) provided by the manufacturers
of solvents and other cleaners must be consulted and
followed during use of the products.
The rough surface, or skin, of castings can contain
sand (silica) that must be removed prior to welding.
Chipping, grinding, and machining are the most common methods of removal of skin from the surface of the
casting.
ARC WELDING
less steel backing bar, or using commercially available
pastes, tapes or ceramic backing products.
To prepare all of these alloys for welding, oxides
formed by previous thermal procedures must be thoroughly removed from the surfaces of the workpieces
because they inhibit wetting and fusion of the base
metal with the weld metal. The presence of oxides can
cause weld inclusions and poor weld bead contour
because the oxides melt at a much higher temperature
than either the base metal or the filler metal.
If wire brushes are used for cleaning weld beads, the
brush should be made of austenitic stainless steel or a
nickel alloy; however, brushes will not remove tenacious oxides such as those that occur on welds in the
age-hardening alloys. These oxides must be removed by
grinding with an aluminum oxide or silicon carbide
wheel. Carbide deburring tools are also successfully
used for oxide removal.
If a workpiece will not be subsequently reheated, a
cleaned area extending 51 mm (2 in.) from the joint on
each side will usually be sufficient to prevent damage
from contamination by foreign materials. The cleaned
area should include the edges of the workpiece.
The method used for removal of foreign materials
prior to welding or heat treating depends on the nature
of the foreign materials. Shop dirt, marking crayons
and ink, and materials with an oil or grease base can be
removed by vapor degreasing or by swabbing with suitable solvents. Paint and other materials not soluble in
degreasing solvents can require the use of alkaline
cleaners or special proprietary compounds. If alkaline
cleaners containing sodium sesquisilicate or sodium carbonate are used, they must be completely removed prior
to welding. Wire brushing will not remove all of the residue; spraying or scrubbing with hot water is required.
Nickel and cobalt alloys are weldable by the arc
welding processes commonly used for steel and other
base metals. Welded joints can be produced to stringent
quality requirements in the precipitation-hardening and
the solid-solution groups.
As noted in Table 4.7, the shielded metal arc welding
(SMAW), gas metal arc welding (GMAW), gas tungsten
arc welding (GTAW), and plasma arc welding (PAW)
processes are commonly used for welding solid-solution
nickel alloys. The precipitation-hardening nickel and
cobalt alloys are welded with the GTAW and PAW processes. The flux cored arc welding (FCAW) process is
used, but less frequently than the other arc processes.
The following processes are not applicable to the
welding of precipitation-hardening alloys—shielded
metal arc welding, gas metal arc welding, and submerged arc welding—because covered electrodes for
these precipitation-hardening alloys dramatically
reduce the mechanical properties of the weld and make
the weld susceptible to interbead slag adhesion. The
submerged arc welding process results in high heat
input, to which most of the precipitation-hardening
alloys are sensitive.
Heat Input Limitations
High heat input during welding can produce detrimental changes in nickel and cobalt alloys. Some degree
of annealing and grain growth will take place in the
heat-affected zone. The heat input of the welding process and the preheat and interpass temperatures will
determine the extent of these changes.
High heat input can cause excessive constitutional
liquation, carbide precipitation, or other harmful metallurgical phenomena, which can result in cracking or
loss of corrosion resistance.
AWS WELDING HANDBOOK
CHAPTER 4—NICKEL AND COBALT ALLOYS
Table 4.7
Arc Welding Processes Applicable to Some of the Nickel and Cobalt Alloys
Processb
Alloya
UNS Number
SMAW
GTAW, PAW
GMAW
SAW
FCAW
X
X
—
X
X
—
X
—
Commercially Pure Nickel
200
N02200
X
X
201
N02201
X
X
Solid-Solution Nickel Alloys (Fine
400
Grain) c
N04400
X
X
X
404
N04404
X
X
X
X
—
R-405
N04405
X
X
X
—
—
X
N06002
X
X
X
—
X
NICR 80
N06003
X
X
—
—
—
NICR 60
N06004
X
X
—
—
—
—
G
N06007
X
X
X
—
C-22
N06022
X
X
X
—
—
G-30
N06030
—
X
X
—
—
G-35
N06035
X
X
X
—
—
59
N06059
X
X
X
X
—
C-2000
N06200
X
X
X
—
—
RA 333
N06333
—
X
—
—
—
600
N06600
X
X
X
X
X
—
601
N06601
X
X
X
X
617
N06617
X
X
X
X
X
926
N08926
X
X
X
X
—
625
N06625
X
X
X
X
X
B
N10001
X
X
X
—
—
C
N10002
X
X
X
—
—
N
N10003
X
X
—
—
—
242
N10242
—
X
X
—
—
B-3
N10675
X
X
X
—
—
HR-160
N12160
—
X
X
—
—
C-276
R20033
X
X
X
X
X
Precipitation-Hardenable Nickel Alloys
K-500
N05500
—
X
—
—
—
Waspaloy
N07001
—
X
—
—
—
R-41
N07041
—
X
—
—
—
80A
N07080
—
X
—
—
—
90
N07090
—
X
—
—
—
282
N07208
—
X
—
—
—
M 252
N07252
—
X
—
—
—
C-263
N07263
—
X
—
—
—
U-500
N07500
—
X
—
—
—
(Continued)
291
292
CHAPTER 4—NICKEL AND COBALT ALLOYS
AWS WELDING HANDBOOK
Table 4.7 (Continued)
Arc Welding Processes Applicable to Some of the Nickel and Cobalt Alloys
Processb
Alloya
UNS Number
SMAW
GTAW, PAW
GMAW
SAW
FCAW
Precipitation-Hardenable Nickel Alloys (Continued)
718
N07718
—
X
—
—
—
—
740
N07740
—
X
—
—
X-750
N07750
—
X
—
—
—
20Cb3
N08020
X
X
X
X
—
602CA
N08031
X
X
X
—
—
HR-120
N08120
—
X
X
—
—
800
N08800
X
X
X
X
X
825
N08825
X
X
X
—
—
706
N09706
—
X
—
—
—
901
N09901
—
X
—
—
—
188
R30188
—
X
—
—
L-605
R30605
X
X
X
—
—
ULTIMET
R31233
X
X
—
—
—
Cobalt Alloys
X
a. Several of these designations are registered trade names; some designations relate to portions of a trade name. These and similar alloys may be known by
other designations and trade names. Designations with UNS numbers in the N07XXX series are age hardenable.
b. SMAW—Shielded metal arc welding
GTAW—Gas tungsten arc welding
PAW—Plasma arc welding
GMAW—Gas metal arc welding
SAW—Submerged arc welding
FCAW—Flux cored arc welding
c. Fine grain is ASTM Number 5 or finer. See Table 4.8 for recommended processes for coarse-grain base metals.
The grain size of the base metal also must be considered when choosing the proper welding process and
technique. Coarser grain size increases the tendency for
underbead cracking because the boundary area has a
higher level of carbides and other intermetallic compounds that promote liquation cracking. Table 4.8
illustrates that a process with low heat input must be
used for welding most of the nickel-base alloys with
coarse grain size.
When problems occur, the welding procedure should
be modified to decrease the heat input. The use of
stringer beads and the alteration of bead shape are two
examples of procedure modifications that may be
employed.
If inadequate inert-gas protection is encountered
when using the high-heat-input or if a high preheat/interpass temperature is allowed, a heavy oxide film may
form on the weld face. The oxide will change a normally
smooth weld surface into a rough surface that is difficult
to clean and inspect. The oxide causes subsequent weld
beads to be more susceptible to oxide inclusions.
Corrosion Resistance
The corrosion resistance of many alloys is not
adversely affected by welding. Filler metals are usually
selected to be close in chemical composition to that of
the base metal or overmatched with respect to corrosion resistance compared to the base metal. The resulting weld metal exhibits comparable corrosion resistance
in most environments. For service in most media, the
corrosion resistance of the weld metal must be similar
to that of the base metal.
The corrosion resistance of some base metals,
however, is adversely affected by welding heat in the
heat-affected zone (the zone adjacent to the weld). For
example, nickel-molybdenum and nickel-silicon alloys
require a postweld annealing treatment followed by a
AWS WELDING HANDBOOK
CHAPTER 4—NICKEL AND COBALT ALLOYS
293
Table 4.8
Effect of Grain Size on Recommended Welding Processesa
Alloy
Grain Sizeb
Gas Metal Arcc
Electron Beam
Gas Tungsten Arc
Shielded Metal Arc
FCAW
X
X
X
X
600
Fine
X
Coarse
—
—
X
X
—
617
Fine
X
X
X
X
X
Coarse
—
—
—
X
—
Fine
X
X
X
X
X
Coarse
—
—
X
X
—
Fine
—
X
X
X
—
Coarse
—
—
—
X
—
718
Fine
—
X
X
X
—
Coarse
—
—
—
X
—
800
Fine
X
X
X
X
—
Coarse
—
X
X
X
—
Fine
X
X
X
X
—
Coarse
—
—
X
X
—
625
706
AISI Type 316 Steel
AISI Type 347 Steel
Fine
X
X
X
X
—
Coarse
—
—
X
X
—
a. Processes marked X are recommended.
b. Fine grain is smaller than ASTM Number 5; coarse grain is ASTM Number 5 or larger.
c. Spray transfer.
rapid quench to restore corrosion resistance in the HAZ
of the weld. For most alloys, postweld thermal treatments are not typically needed to restore corrosion
resistance after welding.
Like some austenitic stainless steels, the nickel-chromium, nickel-iron-chromium, and nickel-iron-chromiummolybdenum alloys can exhibit carbide precipitation in
the HAZ of the weld; but in most environments, this
type of sensitization does not impair corrosion resistance in nickel-base alloys as it does in austenitic stainless steels. Many alloys are stabilized by additions of
titanium or niobium to prevent corrosion in the HAZ.
Although postweld heat treatments are usually not
required, there are notable exceptions for specific service environments. For example, fusion-welded nickelchromium-iron Alloy 600, used for caustic service, and
nickel-copper Alloy 400, used for hydrofluoric acid
service, require a postweld stress relief to avoid stresscorrosion cracking when in service.
strengthened alloys. These alloys can be welded in all
positions and have the same weldability characteristics
as steel. Welding techniques similar to those used in
making high-quality welds in stainless steel are used to
weld nickel and solid-solution-strengthened alloys. Less
depth of fusion and relatively sluggish molten weld
metal is typical of these metals and may make it necessary to vary the technique slightly, as previously noted. 7
Conversely, shielded metal arc welding is seldom
used to weld precipitation-hardening alloys. The alloying elements that contribute to precipitation hardening
are difficult to transfer across the welding arc. Better
welds are obtained by using gas tungsten arc welding
(GTAW) or plasma arc welding (PAW) for structures or
assemblies that are fabricated from these precipitationhardening alloys.
If shielded metal arc welding is to be used to weld
these alloys, interpass bead cleaning to remove oxides is
critical to making a sound weld. Joint efficiencies in
SHIELDED METAL ARC WELDING
7. Refer to Chapter 2 of American Welding Society (AWS) Welding
Handbook Committee, 2004, Welding Processes, Part 1, ed. A.
O’Brien, vol. 2, Welding Handbook, 9th ed., Miami: American Welding Society. See Appendix B of this volume for a detailed description
of chapter contents of the five volumes of Welding Handbook, 9th ed.
Shielded metal arc welding (SMAW) is the primary
process used for welding nickel and solid-solution-
294
CHAPTER 4—NICKEL AND COBALT ALLOYS
AWS WELDING HANDBOOK
shielded metal arc welds will be significantly lower than
those achieved with the gas tungsten arc welding process.
dency to form slag inclusions. It is important that a
short arc length be consistently maintained.
When welding must be done in the vertical, overhead, or horizontal position, it is necessary to use lower
current than that required for the flat position, and the
electrode diameter should be sufficiently small to provide proper control of the weld pool. For vertical welding, the electrode should be held at approximately 90°
to the joint and at a work angle of 0°. Uphill welding is
generally recommended for best results. Overhead welding is similar to vertical welding except that a slightly
shorter arc and lower current (a reduction of 5 amperes
[A] to 15 A) are used.
For square-groove and V-groove welds, the electrode
should be held perpendicular to the joint, but when
welding U-groove joints, the electrode should be held at
a work angle of about 30°. This will result in proper
fusion with the groove faces. The work angle should be
40° to 45° for fillet welding. Joint designs for submerged arc welding are shown in Figure 4.5.
Electrode Position and Manipulation
Molten weld metal in nickel and nickel alloys is less
fluid than molten steel weld metal. The viscosity of
nickel weld metal impedes wetting of the groove faces
and spreading. Thus, the filler metal must be placed in
the joint with more accuracy than that required for steel
filler metal, and some electrode oscillation (weaving) is
necessary to produce a desirable bead contour.
When possible, welding should be done in the flat
position for ease of welding and to achieve higher deposition rates. The electrode position should be at a drag
angle of 20° and a work angle of 0°. This position facilitates control of the molten flux and minimizes the ten-
30°–35°
30°–35°
B
A
A
A
(A) Butt
(C) Single-V-Groove
(B) Single-V-Groove
15°
15°
10°
C
R
50°
A
R
A
A
B to C
(D) Single-U-Groove
Key:
A = 3.2 mm (0.125 in.)
B = 6.4 mm (0.250 in.)
(E) Double-U-Groove
(F) Compound-Angle-Groove
C = 9.5 mm (0.375 in.)
R, radius = 4.8 mm to 7.9 mm (0.188 in. to 0.312 in.)
Figure 4.5—Joint Designs for Submerged Arc Welding
AWS WELDING HANDBOOK
Welding Techniques and Procedures
Because nickel-alloy weld metal does not spread or
flow easily, it must be placed where required by means
of oscillation. This improves fluidity in the weld pool.
The width of the oscillation will depend on factors such
as joint design, welding position, and type of electrode.
For example, pure nickel weld metal is somewhat more
sluggish in the molten state than nickel-chromium alloy
weld metal; thus, the width of oscillation will differ. If
oscillation is used, however, it should not be wider than
three times the diameter of the electrode core wire.
Beads that are too wide are prone to slag inclusions; a
large weld pool leads to poor bead shape and possible
disruption of the gas shield around the arc. Poor shielding
can result in contamination of the weld metal.
There should be no evidence of spatter. If excessive
spatter occurs, it usually indicates that one or more of
the following conditions exist:
1. The arc is too long,
2. The amperage is too high,
3. The polarity is not direct current electrode
positive (DCEP), or
4. The electrode coating has absorbed moisture.
Excessive spatter can also be caused by magnetic arc
blow, which can occur, for example, when using nickelchromium electrodes to weld 9% nickel steel.
The use of higher amperage to overcome poor
fluidity can lead to the following adverse conditions:
1.
2.
3.
4.
Electrode overheating,
Reduced arc stability,
Spalling of the electrode coating, and
Porosity in the weld.
When the welding arc is terminated for any reason,
the arc length should be shortened slightly and,
simultaneously, the travel speed should be increased to
reduce the size of the weld pool. This practice lowers the
possibility of crater cracking as the weld cools, eliminates
the relatively large rolled leading edge associated with
large weld craters, and prepares the way for restarting
the arc.
The manner in which the restart is made, after any
grinding necessary to remove crater cracking, has a
significant influence on the soundness of the weld in the
restart area. A reverse start, or T start, is recommended.
The arc is started at the leading edge of the crater and
carried back to the extreme rear of the crater at a normal
drag-bead speed. The direction is then reversed,
oscillation is started, and the weld is continued. This
restart method has the following advantages:
CHAPTER 4—NICKEL AND COBALT ALLOYS
295
1. The correct arc length can be established in the
groove away from the unwelded joint,
2. Some preheat is applied to the relatively cold
weld crater,
3. The first drops of quenched or rapidly cooled
filler metal are placed so that they are remelted
after the T is completed, and
4. Normal weld progression can begin.
The potential for porosity to form in the weld metal
is minimized when this restart technique is used. Many
welding procedures require that weld craters be ground
out or deburred prior to arc restart. In any case, the
reverse restart or T restart technique should be used.
Another commonly used restart technique involves
placing the restart metal (apt to be porous) where it can
readily be removed by grinding. The restart is made 13
mm to 25 mm (0.5 in. to 1 in.) behind the weld crater
on top of the previous weld bead. The arc strike bead is
later ground until it is level with the rest of the bead.
This technique is often used when welds must meet
stringent radiographic inspection standards. The
technique produces high-quality welds but requires
less welder skill than the T restart technique. Starting
tabs can also be employed so that the portion of the
weld to be used contains no arc strikes.
These general procedures are suitable for all alloys,
but may need slight modifications to suit the characteristics of individual alloys. Commercially pure nickel,
for example, is less fluid than the solid-solution alloys
and requires careful attention to accurate filler metal
placement in the joint.
Stringer beads are recommended for the nickelmolybdenum alloys. If an oscillation technique is used,
the weave is restricted to 1.5 times the diameter of the
electrode core wire. Welding in a position other than
the flat position is not recommended for the nickelmolybdenum alloys. Porosity in the initial arc start can
be a problem with nickel-molybdenum electrodes. This
can be eliminated by using a starting tab for arc
starting. The best practice is to grind all arc starts and
stops to expose sound metal. Start and stop areas that
have been ground can be tested with liquid penetrant
to verify the soundness of the weld.
GAS TUNGSTEN ARC WELDING
Gas tungsten arc welding (GTAW) is widely used in
the welding of nickel and cobalt alloys, especially for
the following applications or conditions:
1. Welding thin base metal,
2. Depositing root passes when the joint will not be
back-welded,
296
CHAPTER 4—NICKEL AND COBALT ALLOYS
3. Welding when the back side of the joint is
inaccessible, or
4. Avoiding detrimental flux residues
resulting from the use of coated electrodes.
The GTAW and plasma arc welding (PAW)
processes are also the preferred joining processes for
welding the precipitation-hardening alloys (refer to Table
Shielding Gases
The recommended shielding gas is argon, or an
argon-helium mixture. Additions of oxygen, carbon
dioxide, and nitrogen should be avoided, as these gases
can cause porosity in the weld or accelerated erosion of
the tungsten electrode. Small quantities of hydrogen
(about 2% to 5%) can be added to argon for singlepass welds. The addition of hydrogen produces a hotter
arc and a smoother bead surface in single-pass welds;
however, hydrogen may cause porosity in multiple-pass
welds in some alloys.
Shielding gas has an influence on arc characteristics,
depth of fusion, and shape of the weld bead. The choice
of shielding gas should be verified during development
of weld procedure specification/ procedure qualification
records. For manual GTAW welds, the shielding gas is
usually argon. For mechanized welding of thin base
metal without filler metal, helium and argon-helium
mixtures have definite advantages over argon: improved
soundness of welds in nickel and nickel-copper alloys
and an increase of up to 40% in welding speed. If a
problem is encountered, it is best to add filler metal.
When helium is used, the arc voltage required for a
given arc length is about 40% greater than that used for
welds made with 100% argon; consequently, the heat
input is greater. Because welding speed is a function of
heat input, the hotter arc permits greater speed. Arc initiation in helium is more difficult when the current is
below 60 A. Thus, for small workpieces and very thin
base metal, argon shielding is a better choice. In some
cases, a high-frequency current can be imposed to aid in
initiation and maintenance of the arc when shielded in
helium.
Electrodes
Either pure tungsten or tungsten alloyed with thorium, cerium, or lanthanum can be used. A 2% thoriated electrode will give good results for most gas
tungsten arc welding. The thoriated electrodes yield
longer life, resulting from low vaporization of the elec8. Refer to Chapter 3 of American Welding Society (AWS) Welding
Handbook Committee, 2004, Welding Processes, Part 1, ed. A.
O’Brien, vol. 2, Welding Handbook, 9th ed., Miami: American Welding Society. See Appendix B of this volume for a detailed description
of chapter contents of the five volumes of Welding Handbook, 9th ed.
AWS WELDING HANDBOOK
trode and cooler operation; however, due to the health
and safety concerns associated with thorium, lanthanum-doped and cerium-doped tungsten electrodes are
commonly used. It is important to avoid overheating
the electrode through the use of excessive current.
If thoriated electrodes are used, a high-efficiency
dust-collection system should be used to capture particles generated during grinding of electrodes or airborne
dust resulting from housekeeping activity. Proper disposal of dust and spent electrodes must be in accordance with local, state and federal regulations. For
more information, refer to Safety and Health Fact Sheet
#27, Thoriated Tungsten Electrodes.9
Arc stability is best when the tungsten electrode is
ground to a flattened point. Cone angles of 30° to 60°
with a small, flat apex are generally used. Periodic
reconditioning of the electrode is required due to the
deterioration of the electrode during welding. The
geometry of the point should be designed for the particular application and can vary from sharp to flat. With
higher amperages, the use of a larger-diameter flat area
is often desirable. The shape of the electrode has an
effect on the depth of fusion and bead width when all
other welding conditions are controlled. Thus, the configuration of the electrode point should be described in
the welding procedure specification.
Welding Current
The polarity recommended for both manual and
mechanized welding is direct current electrode negative
(DCEN). Features of the welding machine often include
a high-frequency circuit to enhance arc initiation and
also a current-decay unit to gradually decrease the size
of the weld crater when breaking the arc. Alternating
current (ac) can be used for mechanized welding if the
arc length is closely controlled. Superimposed high-frequency power is required with conventional sine wave
ac for arc stabilization. High-frequency power is also
useful with direct current to initiate the arc.
Touch arc starting can cause tungsten contamination
of the weld metal. Also, inadvertent dipping of the
tungsten electrode into the weld pool can cause contamination of the electrode. If contamination occurs, the
electrode should be cleaned or broken past the point of
contamination, and reshaped.
The use of high-frequency arc starting allows the
welder to select the starting point of the weld before the
welding current starts, eliminating the possibility of arc
strikes on the base metal. Similarly, an abrupt break of
the welding arc can lead to a porous, rough, or cracked
weld crater. The current-decay function of the welding
9. American Welding Society (AWS) Safety and Health Committee
Safety and Health Fact Sheet #27, Thoriated Tungsten Electrodes,
2003, available at http://www.aws.org/technical/facts/.
AWS WELDING HANDBOOK
CHAPTER 4—NICKEL AND COBALT ALLOYS
machine gradually lowers the current before the arc is
broken to reduce the size of the weld pool and to complete the bead smoothly; similar results can be accomplished by increasing travel speed just prior to breaking
the arc. Examples of proper arc stopping and restarting
techniques are illustrated in Figure 4.6.
TRAVEL UP GROOVE
FACE AND STOP ARC
AT EDGE OF GROOVE
FUSED
INSERT
UNFUSED
INSERT
(A) Technique for Stopping Arc
19 mm
(0.750 in.)
UNFUSED
INSERT
297
Bare Welding Electrodes and Rods
Bare welding electrodes and rods are generally similar to the base metals with which they are used. A weld
is essentially a casting with an inherent dendritic structure different from the relatively uniform grain size of
the wrought base metal. Considering this structure,
adjustments in chemical composition are frequently
made to bring the base metal and weld metal properties
into closer conformity. Alloying of the filler metal is
also done to promote resistance to porosity formation
and hot cracking caused by high temperatures in the
weld pool, which is brought about by high localized arc
current. Also, deliberate over-alloying is frequently
done to make the filler metal tolerant to dilution by
other metals, as is necessary in the nickel cladding of
carbon steel and in the welding of many dissimilar
metal combinations. For GTAW, direct current-electrode negative (DCEN) is used. High-purity grades of
either argon or helium (or a combination of the two)
are used as the shielding gas.
The inherent reduction in stress-rupture ductility
imposed by the dendritic structure of the weld metal
can be offset, to some extent, by varying the chemical
composition. Likewise, the fatigue resistance of the cast
structure is lower than that of base metal with the same
chemical composition. Thus, as with any alloy group
intended for use under special service conditions, the
difference between the weld metal and the base metal
requires laboratory analysis by qualified personnel.
(Refer to Figure 4.1, which illustrates the need for
changes in the filler metal to accommodate anticipated
service temperature changes.) The chemistry of the filler
metal can be adjusted to ensure that joint efficiency at
any designated service temperature is optimum.
Welding Technique and Procedure
DIRECTION
OF TRAVEL
STRIKE ARC
(B) Technique for Restarting Welding
after Stopping Arc
Figure 4.6—Techniques for Stopping
and Restarting the Welding Arc
The welding torch should be held with the work
angle at 0° and the travel angle at nearly 0°. If the drag
angle is more than 35°, air may be drawn into the
shielding gas, which causes porosity in the weld metal
of some nickel alloys.
The electrode extension beyond the gas nozzle
should be short but appropriate for the joint design. For
example, a maximum of 5 mm (0.20 in.) is used for
butt joints in thin base metal, whereas up to 13 mm
(0.5 in.) may be required for some fillet welds.
The shortest possible arc length must be maintained
when filler metal is not added. The arc length should
not exceed 1.3 mm (0.050 in.); 0.5 mm (0.020 in.) is
preferable. Figure 4.7 illustrates the effect of arc length
on the soundness of welds in nickel-copper Alloy 400,
made without the addition of filler metal.
298
CHAPTER 4—NICKEL AND COBALT ALLOYS
Figure 4.7—Effect of Arc Length
on Autogenous Gas Tungsten
Arc Welds in a Nickel-Copper Alloy:
(A) Sound Weld Made with Correct Arc Length;
(B) Porous Weld Caused by Excessive Arc Length
An adequate quantity of shielding gas must be delivered to the weld zone at all times during welding, and it
must be delivered with very little turbulence. A shielding gas flow rate as low as 4 liters per minute (L/min)
(8 cubic feet per hour [ft3/h]) has been used on thin
base metal and as high as 14 L/min (30 ft3/h) for thicker
base metal. To minimize turbulence, gas nozzles should
be large enough to deliver the shielding gas to the weld
zone at low velocity. The use of a shielding gas flow
rate that is too high can increase turbulence and
can result in undesirable weld pool cooling. Special
nozzles, such as a gas lens, are designed to minimize
turbulence.
Filler metals contain elements that improve resistance to cracking and control of porosity; thus, optimum benefit from these elements is obtained when the
weld bead contains at least 50% filler metal. The weld
pool should be kept still; agitation of the weld pool by
the welding arc should be avoided.
The hot end of the filler metal should be kept within
the gas shield to avoid oxidation of the hot tip. Filler
metal should be added at the leading edge of the weld
pool to avoid contact with the tungsten electrode.
Shielding of the weld root surface (back side of the
joint) is usually required. If a complete-joint-penetration weld is made with the root surface exposed to air,
the weld metal on the root reinforcement side will be
oxidized and porous. Shielding of the weld root can be
provided with inert gas dams (in pipe), grooved backing
bars, or a backing flux (in plate). If flux is used, it
should be of a thick consistency, applied in a heavy layer,
and allowed to dry thoroughly prior to welding. Figure
4.8 shows a radiograph of a weld with a high level of
porosity caused by welding while using insufficiently
dried flux. As a matter of good practice, all flux should
be removed after the weld is completed, as most welding fluxes are highly corrosive at elevated temperatures.
AWS WELDING HANDBOOK
Figure 4.8—Porosity Caused by Wet Backing Flux
in a Gas Tungsten Arc Weld in Nickel-Copper
Square-groove welds can be made in base metal up
to 2.5 mm (0.10 in.) thick in a single pass. In addition
to using the proper arc length, the travel speed should
be adjusted so that the weld pool is elliptically shaped; a
teardrop-shaped weld pool caused by excessive travel
speed is prone to centerline cracking during solidification. Travel speed also has an effect on porosity in some
alloys. In general, porosity will be at a minimum within
some range of welding speed determined by trial welds.
In summary, all solid-solution alloys except high-silicon casting alloys are readily weldable with the GTAW
process. Commercially pure nickel and nickel-copper
alloys require extra care, as described, to prevent porosity in welds made without filler metal. Filler metals normally contain deoxidizing elements to inhibit porosity.
Therefore, filler metal additions are generally the best
means of avoiding porosity when welding the solidsolution alloys. Nickel alloys containing chromium are less
prone to weld-metal porosity. The chromium-containing
filler metals also contain other alloying additions to
overcome tendencies toward hot cracking.
Welding Precipitation-Hardening Alloys
The gas tungsten arc welding process is most widely
used for welding the precipitation-hardening alloys
because it provides excellent protection against oxidation and loss of hardening elements. When matching
filler metal is used, the mechanical properties of GTAW
welds will be somewhat higher than those of welds
made with gas metal arc welding (GMAW). Compared
to the GMAW process, hot-cracking tendencies in
boron-containing alloys are reduced with GTAW. A
special precaution must be observed when the base
metal contains high amounts of aluminum and titanium. During welding, some of the aluminum and titanium form refractory oxides on the surface of the weld
AWS WELDING HANDBOOK
bead. In multiple-pass welds, these oxides must be
removed before the next weld bead is made. Otherwise,
because of the high melting points of these refractory
oxides, they will become oxide inclusions in the weld.
Figure 4.9 shows oxide stringers in Alloy X-750 resulting from poor bead cleaning before subsequent passes
were made.
The two systems of precipitation-hardening alloys
are the nickel-aluminum-titanium system, in Alloy
X-750, and the nickel-niobium-aluminum-titanium
system, in Alloy 718. Both alloy systems have good weldability. The significant difference between the two
systems is the time required for precipitation to occur.
The nickel-aluminum-titanium system responds rapidly
to precipitation-hardening temperatures. The nickelniobium-aluminum-titanium system responds slowly,
which improves the weldability of these alloys. The
delayed precipitation reaction enables the alloys to be
aged directly after welding, without annealing, and it
lessens the possibility of base-metal cracking.
When cracking occurs in the aluminum-titanium
system, the adverse results can be severe. Figure 4.10
illustrates a failure in Alloy X-750 plate that is 51 mm
(2 in.) thick and welded in the age-hardened condition
and re-aged after welding without intermediate stress
relief. The failure could have been avoided by changing
the fabrication sequence to the following:
1.
2.
3.
4.
Annealing the base metal,
Welding,
Stress relieving, and
Aging.
Figure 4.9—Oxide Stringers in Alloy X-750 Weld
Resulting from Inadequate Removal of
Refractory Oxides from Weld Face
before Depositing the Next Bead
CHAPTER 4—NICKEL AND COBALT ALLOYS
299
Figure 4.10—Failure in a Weld in Alloy
X-750 Plate (51 mm [2 in.] Thick) Caused
by Welding in the Aged Condition
Heating and cooling rates are also critical. The rule
for welding these alloys is that they must be given an
appropriate postweld heat treatment before they are
precipitation hardened. Rapid heating through the precipitation-hardening range is important. The supplier of
the base metal should be consulted before a welding
procedure is confirmed so that very precise instructions
can be provided to fabrication personnel. In both
systems, heat input during welding should be held at
a moderately low level to obtain the highest joint
efficiency.
Strain-Age Cracking
Most precipitation-hardening alloys are subject to
strain-age cracking, but this type of cracking can be
prevented by strictly adhering to the requirements of
correct joint design, welding procedure, and heat-treating. Strain-age cracking is seldom a problem in the niobium-aluminum-titanium system, but there have been
reports of cracking of base metal when it is welded in
the aged condition and subsequently re-aged under
highly restrained conditions. From the viewpoint of
optimum properties, this is an unusual and unfavorable
procedure, but sometimes is necessitated by the complexity of assemblies that were built in stages. It should
be recognized that highly weldable alloys can crack if
they are part of a complex sequential assembly.
Strain-age cracking in precipitation-hardening nickel
alloys is the result of residual stresses that exceed the
yield point of the material. High residual stresses are
developed during the aging process and are increased
further by forming, machining, and welding. Most precipitation-hardening alloys are subject to strain-age
cracking; however, alloys containing niobium have a
greater resistance to cracking because of the slow hardening response of the niobium precipitate than the aluminum-titanium precipitate.
300
CHAPTER 4—NICKEL AND COBALT ALLOYS
With careful adherence to proven heat treatment and
welding procedures, various alloys are routinely welded
and are used in thousands of industrial applications.
(Refer to Figure 4.2, which shows the relative
weldability of several alloys.)
The need for the management and reduction of residual
stresses is related to the fact that a rapid decrease in the
ductility of certain alloys at the aging temperature does
not readily permit plastic flow to occur.
During the thermal hardening treatment, an overall
contraction of volume occurs. Welding stresses, coupled
with this contraction, increase the tendency for strainage cracking. Solution annealing after welding will
relieve welding stresses and thereby decrease the potential
for strain-age cracking. As previously mentioned,
however, it is important to rapidly heat the weldment
through the hardening temperature range to decrease
precipitation reactions. Placing the welded assembly
into a furnace preheated to the annealing temperature
(or above) is a good first step, but the rate of heating is
related to the complexity of the welded assembly, the
overall mass of the assembly, and how it is supported in
the furnace.
Several techniques can be used to lower
welding stresses, including the following:
1. Application of a suitable preheat,
2. Fixturing of the workpieces prior to welding,
3. Welding the joint with an appropriate
bead sequence,
4. Annealing at some intermediate stage, and
5. Controlling heat input to deliberately control the
metallurgy of the alloy.
For example, one metallurgical treatment is to overage
the workpieces prior to welding. This treatment is
designed to precipitate the hardening constituent. This
treatment adversely affects the final hardness and yield
strength of the alloy; nevertheless the joint can be
welded because residual welding stresses are lower, and
further aging cannot occur. This treatment is used with
alloys containing relatively large amounts of aluminum
and titanium, such as Alloy U-500 (refer to Figure 4.2).
Welding of precipitation-hardened components
should be avoided when possible. Welding in this
condition will result in re-solutioning and overaging in
the heat-affected zone (HAZ), and consequently, a
degradation in properties. A postweld heat treatment
is then necessary to restore the properties in this zone.
In alloys with high percentages of aluminum and
titanium, cracking will occur immediately—as soon
as the component is exposed to the aging temperature
as it is being heated to the annealing temperature.
In summary, the welding of precipitation-hardening
alloys requires sound metallurgical knowledge of the
base metal of the workpieces and an understanding of
AWS WELDING HANDBOOK
the procedures for assembly, welding, and fabrication
that are designed to take advantage of the best obtainable properties of the base metal and weld metal.
GAS METAL ARC WELDING
Gas metal arc welding (GMAW) can be used to weld
all of the solid-solution nickel alloys except high-silicon
castings, but this process is an inferior choice for welding many of the age-hardening alloys.10
The dominant mode of GMAW metal transfer is
spray transfer, but short-circuiting transfer and pulsedspray welding are also widely employed. Spray transfer
of filler metal is more economical than the short-circuiting transfer because it uses higher welding currents and
can be used with large-diameter filler metal, but the
pulsed spray method of metal transfer offers advantage
of welder control of the arc in out-of-position welding
by using small-diameter welding filler metal and lower
currents while maintaining peak welding currents in the
spray transfer range. Both methods are widely used in
the production of low-dilution weld cladding to
increase corrosion resistance on base metals, such as
carbon steels and low alloy steels.
The globular transfer mode of GMAW can also be used,
but is seldom employed in nickel alloys because it creates
an erratic depth of fusion and an uneven contour of the
weld beads. This is conducive to forming discontinuities.
Shielding Gases
The protective atmosphere for GMAW is usually provided by argon or argon mixed with helium. The optimum shielding gas is specific to the type of metal transfer
used. Good results are obtained with pure argon when
using spray transfer and globular transfer. The addition of
helium has been found to be beneficial; however, it should
be noted that increasing the helium content leads to progressively wider and flatter beads and less depth of fusion.
When used alone, helium creates an unsteady arc
and excessive spatter. The addition of oxygen or carbon
dioxide, while commonly used with some base metals,
is generally avoided when welding nickel and cobalt
alloys because of the risk of producing an oxidized surface, porosity, and irregular bead faces. Some active
gases that contain carbon dioxide are used in certain
cases, but these must be qualified and used with caution.
Gas flow rates for GMAW range from 12 L/min to
47 L/min (25 ft3/h to 100 ft3/h), depending on joint
10. Refer to Chapter 4 of American Welding Society (AWS) Welding
Handbook Committee, 2004, Welding Processes, Part 1, ed. A.
O’Brien, vol. 2, Welding Handbook, 9th ed., Miami: American Welding
Society. See Appendix B of this volume for a detailed description of
chapter contents of the five volumes of Welding Handbook, 9th ed.
AWS WELDING HANDBOOK
design, welding position, nozzle size, and whether a
trailing shield is used.
When short-circuiting gas metal arc welding is used,
argon with helium produces the best results. Argon
used alone provides a favorable pinch effect, but it can
also produce excessively convex weld beads, which can
lead to incomplete-fusion discontinuities. With helium
added to argon, the weld bead is flatter with good wetting, which reduces the possibility of incomplete fusion
between weld beads.
Gas flow rates for short-circuiting transfer welding
range from 12 L/min to 21 L/min (25 ft3/h to 45 ft3/h).
As the percentage of helium is increased, the gas flow
rate must also be increased to provide adequate weld
protection.
The size of the gas nozzle can have important effects
on welding conditions. For example, when using a
mixture of 50% argon-50% helium at a gas flow rate
of 19 L/min (40 ft3/h), with a gas nozzle 9.5 mm
(0.375 in.) in diameter, the maximum current is about
120 A before weld bead oxidation begins to occur. When
the nozzle diameter is increased to 16 mm (0.625 in.), a
current of 170 A can be used before weld bead oxidation begins to occur. Thus, delivering the shielding gas
to the weld pool at low velocity is important.
When pulsed-spray welding is used, argon with an
addition of helium provides the best results. Good
results have been obtained with argon and 15% to 30%
helium. The flow rate should be at least 12 L/min to
21 L/min (25 ft3/h to 45 ft3/h). Excessive gas flow rates
can interfere with the stability of the arc.
Filler Metals
Filler metals for the GMAW process are generally
similar to the base metals with which they are used. It
should be recognized, however, that a weld is essentially a casting with an inherent dendritic structure, and
does not have the relatively uniform grain size of
wrought base metal. Therefore, adjustments in chemical
composition are frequently made to bring the base
metal and weld metal properties into closer agreement.
Alloying of the filler metal is also done to resist porosity
formation and hot cracking that can result from the
high localized arc current which causes high weld pool
temperatures. Also, deliberate over-alloying is frequently done to make the filler metal tolerant to dilution by other metals, as necessary in nickel cladding on
carbon steel and in many kinds of dissimilar metal
welding.
The inherent reduction in stress-rupture ductility
imposed by the dendritic structure of a weld can be offset to some extent by varying the chemical composition.
Likewise, the fatigue resistance of cast structures is
lower than that of base metal with the same chemical
composition. Thus, as with any alloy group when spe-
CHAPTER 4—NICKEL AND COBALT ALLOYS
301
cial service conditions apply, the difference in properties of a weld and the base metal requires laboratory
analysis by metallurgists or engineers. (Refer to Figure
4.1, which illustrates a classic point: changes in filler
metal are needed as the anticipated service temperature
changes, so that joint efficiency at any designated service temperature is optimum.)
Welding Current
The recommended polarity for the GMAW process is
direct current electrode positive (DCEP), with electrode
diameters of 0.9 mm (0.035 in.), 1.1 mm (0.045 in.), and
1.6 mm (0.062 in.). The specific size depends on the mode
of metal transfer and the thickness of the base metal.
Constant-potential power sources are normally used,
but constant-current units have been used in special
cases. For short-circuiting transfer, the power source
must have separate slope and secondary inductance
controls.
Modern power sources (thyristor, invertor, and transistor-controlled) have facilitated the adjustment of
welding conditions using pulsed frequencies (pulsedarc) in which the pulse parameters are linked to the
electrode feed speed control. In more highly developed
equipment, all the welding conditions, pulse current,
pulse duration, background current, and pulse frequency, are included in this control system. The capability of these power sources, in addition to the use of
microprocessors and computer-controlled welding in
critical applications, can achieve cost savings by using
solid welding wire instead of the more costly tubular
welding wire.
The use of tubular wire is limited when welding
nickel and cobalt alloys. The improved power sources
use solid welding wire; they have automatic controls
that produce a welding arc with little or no spatter, and
incomplete joint penetration can be avoided. Figure
4.11 is an illustration of automatic controls.
Welding Techniques and Procedures
Typical conditions for spray, pulsed spray, and
short-circuiting transfer modes for GMAW are shown
in Table 4.9. This data can provide guidance for the
development of appropriate welding procedures.
Best results are obtained with the welding gun at
both the work angle and travel angle of 0°, consistent
with good visibility of the arc and good shielding. The
arc length should be adjusted so that spatter is minimal,
but an excessively long arc will be difficult to control.
Incomplete fusion can easily occur if the manipulation of the welding gun is not correct when using the
short-circuiting metal transfer mode. The gun should be
advanced at a rate that will keep the arc in contact with
the base metal but not the weld pool. Multiple-pass
302
AMPS (CURRENT)
CHAPTER 4—NICKEL AND COBALT ALLOYS
AWS WELDING HANDBOOK
PEAK
CURRENT
BACKGROUND
CURRENT
The welding wire and contact tube must be kept
clean. Dust and dirt carried into the contact tube can
cause erratic wire feeding. The contact tube should be
cleaned periodically and the spool of welding wire
should be covered when not in use.
PLASMA ARC WELDING
TUNE
Figure 4.11—Wave Form Produced by
Pulsed-Arc Gas Metal Arc Welding Machine
with Automatic Control of Pulse Current,
Background Current, and Pause Time
welding, which produces highly convex beads, may
increase the tendency for incomplete fusion.
Oscillating gun manipulation for pulsed GMAW is
similar to that used for the electrode in SMAW. A slight
pause is needed at the limits of the weave to reduce the
tendency to produce undercut.
The plasma arc welding process employs a constricted arc between a nonconsumable electrode and
the weld pool (transferred arc) or between the electrode and the constricting nozzle (nonconstricted arc).
Shielding is obtained from the ionized gas issuing from
the torch, which may be supplemented by an auxiliary
source of shielding. The process is used without the
application of pressure.
Nickel and cobalt alloys can be readily joined using
the plasma arc welding (PAW) process. The constricted
arc permits greater depth of fusion than that obtainable with the GTAW process, although the welding
procedures for both processes are similar. Squaregroove welds can be made in base metal up to about
8 mm (0.3 in.) thick with a single pass when the keyhole technique is used. Thin base metal can be welded
Table 4.9
Typical Conditions for Gas Metal Arc Welding of Nickel Alloys
Electrode
Base Metal
Alloya
UNS
Number
200
400
600
N02200
N04400
N06600
200
400
600
200
400
600
G
C-4
B-2
Diameter
AWS
Classificationb
mm
in.
ERNi-1
ERNiCu-7
ERNiCr-3
1.6
1.6
1.6
0.062
0.062
0.062
N02200
N04400
N06600
ERNi-1
ERNiCu-7
ERNiCr-3
1.1
1.1
1.1
0.045
0.045
0.045
N02200
N04400
N06600
N06007
N06455
N10665
ERNi-1
ERNiCu-7
ERNiCr-3
ERNiCrMo-1
ERNiCrMo-7
ERNiMo-7
0.9
0.9
0.9
1.6
1.6
1.6
0.035
0.035
0.035
0.062
0.062
0.062
Melting Rate
mm/s
in./min
Arc Voltage
Shielding
Gas
Welding
Position
Average
Peakc
Welding
Current, A
Ar
Ar
Ar
Flat
Flat
Flat
29–31
28–31
28–30
NA
NA
NA
375
290
265
Ar or Ar-He
Ar or Ar-He
Ar or Ar-He
Vertical
Vertical
Vertical
21–22
21–22
20–22
46
40
44
150
110
90–120
Ar-He
Ar-He
Ar-He
Ar-He
Ar-He
Ar-He
Vertical
Vertical
Vertical
Flat
Flat
Flat
20–21
16–18
16–18
25
25
25
NA
NA
NA
NA
NA
NA
160
130–135
120–130
160
180
175
Spray Transfer
87
85
85
205
200
200
Pulsed Spray Transfer
68
59
59
160
140
140
Short Circuiting Transfer
152
360
116–123 275–290
114–123 270–290
—
—
—
—
78
185
a. Several of these designations are registered trade names; some designations relate to portions of a trade name. These and similar alloys may be known by
other designations and trade names.
b. See AWS A5.14/A5.14M:2011, Specification for Nickel and Nickel-Alloy Bare Welding Electrodes and Rods.
c. NA = Not Applicable.
AWS WELDING HANDBOOK
303
CHAPTER 4—NICKEL AND COBALT ALLOYS
with lower current (i.e., similar to GTAW). Base metal
thicker than 8 mm (0.3 in.) can be welded using groove
weld joint designs similar to those shown in Figure 4.5.
(Refer also to Figure 4.14.) The first pass can be made
with a keyhole weld and the succeeding passes with
GTAW or another welding process. The root face
should be about 5 mm (0.20 in.) wide for PAW, compared to 2 mm (0.08 in.) for GTAW.11
Special techniques are required for keyhole welds in
thicknesses of 3 mm (0.12 in.) and greater. Increased
orifice gas flow and upslope of the welding current is
required to initiate the keyhole; decreased orifice flow
and downslope of these conditions is needed to fill the
keyhole cavity at the end of the weld bead.
Argon or argon-hydrogen mixtures are normally recommended for the orifice gas and shielding gas. Adding
hydrogen to argon increases the arc energy for keyhole
welding and high-speed autogenous welding. Additions
up to 15 vol % can be used, but these additions should
be made with care because hydrogen can cause porosity
in the weld metal. Therefore, the gas mixture for a specific application should be determined by appropriate tests.
Typical welding conditions used for autogenous
plasma arc keyhole welds in four nickel alloys are listed
in Table 4.10. Other conditions can also produce
acceptable welds and should be evaluated by appropriate tests prior to production to ensure reliability.
11. Refer to Chapter 7 of American Welding Society (AWS) Welding
Handbook Committee, 2004, Welding Processes, Part 1, ed. A.
O’Brien, vol. 2, Welding Handbook, 9th ed., Miami: American Welding
Society. See Appendix B of this volume for a detailed description of
chapter contents of the five volumes of Welding Handbook, 9th ed.
FLUX CORED ARC WELDING
Flux cored arc welding (FCAW) is an arc welding
process that uses an arc between a continuous filler
metal electrode and the weld pool. The process is used
with shielding gas from a flux contained within the
tubular electrode, with or without additional shielding
from an externally supplied gas, and without the application of pressure.
In the late 2000s, several new FCAW formulations
were approved by the American Welding Society for use
in welding nickel alloys.12 Since that approval, many of
these are widely used in industries that weld large nickel
alloy assemblies, including the electric power, chemical,
and petroleum industries.
The alloy systems that are generally supported
include NiCr, NiCrMo, NiCrFe, and NiCrMn. More
details on these alloys are included in the latest edition
of AWS A5.34/A5.34M, Specification for Nickel Alloy
Electrodes for Flux Cored Arc Welding. The shielding
used for these alloys, in addition to the flux, is argon
with 5% to 25% carbon dioxide.
The use of these formulations resulted in much
higher deposition rates, in many cases, 2 to 3 times
higher than those achieved with the use of traditional
SMAW and GMAW consumables. These filler materials,
approved in AWS A5.34, allow for welding in all positions, although some of the first applications were for
overhead and vertical welding, where the consumables
12. Refer to Chapter 5, Flux Cored Arc Welding in Welding Processes, Part 1, Volume. 2 of the Welding Handbook, 9th edition.
Table 4.10
Typical Conditions for Autogenous Plasma Arc Welding of Nickel Alloys with Keyhole Welding
Thickness
Alloy
Nickel (UNS N02200)
mm
in.
Orifice Gas Flow*
L/min
ft3/h
Shielding Gas Flow
L/min
ft3/h
Welding
Current,
A
Arc
Voltage,
V
Travel Speed
mm/s
in./min
3.2
0.125
5
10
21
45
160
31.0
8
20
6.0
0.235
5
10
21
45
245
31.5
6
14
7.3
0.287
5
10
21
45
250
31.5
4
10
67Ni-32 Cu (UNS N04400)
6.4
0.250
6
12.5
21
45
210
31.0
6
14
76Ni-16 Cr-8 Fe (UNS N06600)
5.0
0.195
6
12.5
21
45
155
31.0
7
17
6.6
0.260
6
12.5
21
45
210
31.0
7
17
3.2
0.125
5
10
21
45
115
31.0
8
18
5.8
0.230
6
12.5
21
45
185
31.5
7
17
8.3
0.325
7
14.0
21
45
270
31.5
5
11
46Fe-33 Ni-21Cr (UNS N08800)
*Orifice diameter: 3.5 mm (0.136 in.).
Orifice and shielding gas: Ar-5 vol % H2.
Root shielding gas: Argon.
304
CHAPTER 4—NICKEL AND COBALT ALLOYS
AWS WELDING HANDBOOK
It should be noted that the SAW process is seldom
used to weld cobalt alloys and precipitation-hardening
alloys, and it is not recommended for joining thick
nickel-molybdenum alloys. The high heat input and
slow cooling rate of the welds result in low weld ductility and loss of corrosion resistance due to the changes in
chemical composition caused by flux reactions.
Fluxes
Photograph courtesy of Böhler Thyssen Welding USA, Inc.
Figure 4.12—Profile of a Flux Cored Arc Weld
performed much better than those developed for other
welding processes. The flux addition tends to improve
joint penetration and appearance, as shown in Figure
4.12. The weld appearance and shape are good in this
fillet welding application.
SUBMERGED ARC WELDING
Submerged arc welding (SAW) can be used to weld
several solid-solution nickel alloys. Appropriate filler
metals and fluxes are available. The high deposition
rate provided by this process makes it an efficient
method for joining thick base metal. Compared to other
arc welding processes, bead surfaces are smoother, slag
is self-peeling (if the flux has been properly selected),
and there is less discomfort for the welding operator.13
The double-U groove is the preferred design for all
joints that permit its use. It can be completed in less
time, with less filler metal and flux, and results in lower
residual stress. Refer to Figure 4.5 for joint designs for
submerged arc welding.
13. Refer to Chapter 6 of American Welding Society (AWS) Welding
Handbook Committee, 2004, Welding Processes, Part 1, ed. A.
O’Brien, vol. 2, Welding Handbook, 9th ed., Miami: American Welding Society. See Appendix B of this volume for a detailed description
of chapter contents of the five volumes of Welding Handbook, 9th ed.
Submerged arc welding fluxes designed for use with
specific welding electrodes are available for several
nickel alloys. In addition to protecting the weld pool
from atmospheric contamination, the fluxes provide arc
stability and contribute important properties to the
weld metal. Fluxes used to weld carbon steels and stainless steel are invariably unsuitable for welding nickel
alloys.
The flux cover should be minimal; it should be only
sufficient to prevent the arc from breaking through. An
excessive flux cover can cause deformed weld beads.
Slag is easily removed and should be discarded, but
unfused flux can be reclaimed. To maintain consistency
in the flux particle size, however, reclaimed flux should
be mixed with an equal amount of new flux.
Submerged arc welding fluxes are chemical mixtures
that can absorb moisture. Storage in a dry area and
resealing previously opened containers are standard practice. Flux that has absorbed moisture can be reclaimed
by heating. The flux manufacturer should be consulted
regarding the recommended reclamation procedure.
Filler Metals
Submerged arc welding employs the same filler metals as those used with the gas tungsten arc welding and
gas metal arc welding processes. The chemical composition of the weld metal will be somewhat different
because additions are made to the flux to allow the use
of higher current and larger-diameter welding filler
metals.
Welding electrodes used for joining nickel alloys are
usually smaller in diameter than those used to weld carbon steels. For example, the maximum diameter used to
weld plate is 2.4 mm (0.094 in.), whereas 1.1 mm
(0.045 in.) has been used to weld sheet. Table 4.11 provides deposition rates and polarity for two` filler metal
and flux combinations. Table 4.12 shows typical welding conditions for three alloy and flux combinations.
Welding Current
Direct current electrode negative (DCEN) or direct
current electrode positive (DCEP) can be used for submerged arc welding. The preferred polarity for groove
joints is DCEP because it yields flatter beads and provides greater depth of fusion and depth of penetration
AWS WELDING HANDBOOK
CHAPTER 4—NICKEL AND COBALT ALLOYS
305
Table 4.11
Deposition Rates for Submerged Arc Welding for Specific Filler Metal and Flux Combinations
Wire Diameter
Filler Metal and Flux
ERNiCr-3 with Flux 4*
ERNiCu-7 with Flux 5*
mm
Deposition Rate
in.
Polarity
kg/h
lb/h
1.6
0.063
DCEN
7.3–8.2
16–18
1.6
0.063
DCEP
6.4–7.7
14–17
2.4
0.094
DCEN
9.1–9.5
20–21
2.4
0.094
DCEP
7.3–7.7
16–17
1.6
0.063
DCEN
7.3–7.7
16–17
1.6
0.063
DCEP
6.4–7.3
14–16
2.4
0.094
DCEN
9.1–9.5
20–21
2.4
0.094
DCEP
7.3–7.7
16–17
*Proprietary flux from Special Metals Corporation. Weight of flux consumed is approximately equal to weight of filler metal.
Table 4.12
Typical Conditions for Submerged Arc Welding for Specific Alloy and Flux Combinations
ERNiCr-3 with Flux 4a
ERNi-1 with Flux 6a
ERNiCu-7 with Flux 5a
Base Metal
Nickel 200
Ni-Cu alloy 400
Ni-Cr-Fe alloy 600b
Filler Metal Diameter, mm (in.)
1.6 (0.063)
1.6 (0.063)
1.6 or 2.4 (0.063 or 0.094)
22–25 (0.875–1.0)
Parameter
Electrode Extension, mm (in.)
22–25 (0.875–1.0)
22–25 (0.875–1.0)
Power Source
DC, Constant Voltage
DC, Constant Voltage
DC, Constant Voltage
Polarity
DCEP
DCEP
DCEP
Current, A
250
260–280
250 with 1.6 mm (0.063 in.) wire
250–300 with 2.4 mm (0.094 in.) wire
Voltage, V
28–30
30–33
30–33
Travel Speed, mm/min (in./min)
10–12 (250–300)
8–11 (200–280)
8–11 (200–280)
Joint Restraint
Full
Full
Full
a. Proprietary flux from Inco Special Metals Corporation.
b. The conditions also apply to iron-nickel-chromium Alloy 800.
at low voltage (30 volts [V] to 33 V). For weld surfacing,
DCEN is frequently used because it yields higher deposition rates, and lessens depth of penetration and depth
of fusion. This reduces the amount of dilution from the
base metal; however, DCEN requires a deeper flux
cover because of increased flux consumption.
Welding Technique and Procedure
Typical chemical compositions of the weld metal in
butt joints are listed in Table 4.13. The samples were
produced by SAW. The difference in chemical composition at various levels is partially related to dilution from
the base metal and elements consumed from the flux.
Slag inclusions are always a possibility during any welding involving flux. Slag inclusions can be controlled by
appropriate joint design (refer to Figure 4.5) and proper
placement of weld beads. Figure 4.13 illustrates weld
bead placement in a butt joint in nickel-chromium-iron
Alloy 600, 76 mm (3 in.) thick.
The weld interface can vary from flat to slightly convex. Concave beads have produced centerline cracking
in highly restrained joints. The number of weld beads
and the bead contour are most effectively controlled by
adjustments in voltage and travel speed.
Fully restrained welds in Alloy 600 plate, 150 mm
(6 in.) thick, using ERNiCr-3 filler metal and Flux 4
306
CHAPTER 4—NICKEL AND COBALT ALLOYS
AWS WELDING HANDBOOK
Table 4.13
Chemical Composition of Weld-Metal Sample from Welds in Butt Joints, wt %
Filler Metal and Flux
Base
Material
Ni
C
Mn
Fe
S
Si
Cu
Cr
Ti
Others
ERNiCu-7 with Flux 5*
ERNiCr-3 with Flux 4*
Alloy 400
Alloy 600
Bal.
Bal.
0.06
0.07
5.0
3.21
3.5
1.75
0.013
0.006
0.90
0.40
26.0
—
—
19.25
0.48
0.17
—
Nb + Ta = 3.39
*Proprietary flux from Inco Alloys International, Inc.
have been made and stringently tested for use in nuclear
power applications.
The chemical composition of the weld deposit
remains virtually constant throughout such joints, with
no increase in chemical elements arising from an accumulation of the flux components. Table 4.14 shows the
composition at various levels (intervals of approximately 13 mm [0.5 in.]) of weld metal from the joint
(refer to Figure 4.13), beginning at the top of the joint
progressing downward toward the weld root.
FILLER METALS AND FLUXES
Figure 4.13—Bead Placement into Joint in
Alloy 600 (76 mm [3 in.] Thick) Welded with
1.6 mm (0.062 in.) Diameter ERNiCr-3
Filler Metal and Submerged Arc Flux 4
In most cases, the composition of weld metal resulting from a shielded metal arc welding (SMAW) electrode used during welding resembles that of the base
metal with which it is used. Invariably, however, the
chemical composition of the weld metal will have been
adjusted to satisfy weldability requirements; usually
with additions to control porosity, enhance resistance
to microcracking, or improve mechanical properties.
Covered electrodes usually have additions of deoxidizing ingredients such as titanium, manganese, and
niobium. Filler metal is almost universally selected
Table 4.14
Chemical Composition of Weld Metal at Various Levels* of a Joint in
Alloy 600 (76 mm [3 in.] Thick) Welded with ERNiCr-3 and SAW Flux 4, wt %
Element
Nickel
Chromium
Niobium
Iron
Silicon
Carbon
Sulfur
Level 1
Level 2
Level 3
Level 4
Level 5
Level 6
73.6
18.1
3.61
0.86
0.44
0.05
0.003
73.5
18.0
3.71
0.87
0.44
0.05
0.003
73.6
18.1
3.59
0.88
0.43
0.05
0.003
73.5
18.0
3.67
0.88
0.43
0.05
0.003
73.7
18.1
3.50
0.87
0.44
0.05
0.003
73.6
18.0
3.60
1.00
0.44
0.05
0.003
*Refer to Figure 4.13. Approximately 13 mm (0.5 in.) intervals in a joint 76 mm (3 in.) thick.
AWS WELDING HANDBOOK
according to Specification for Nickel and Nickel Alloy
Welding Electrodes for Shielded Metal Arc Welding,
AWS A5.11.14 Sometimes military specifications apply,
such as the MIL-E-22200 series, which are prepared by
the United States Department of Defense.
Covered Electrode Formulations
The chemical, physical, and mechanical properties of
weld deposit are considerations that are involved in the
formulation of covered electrodes. The electrode formulator uses various chemicals to enhance the conditions
present in the welding arc environment. Alkali metals
have low ionization voltages, making ionization more
predictable and arc starting easier. A second chemical
means of stabilizing a welding arc is to add compounds
that increase emission. Refractory oxides are the best
additives for this purpose.
Nickel electrodes must be formulated to compensate
for the sluggish nature of the molten metal and the
relatively high ionization potential of the elements in
the core of the electrode. The basic functions of the
electrode coating are to provide the following conditions:
1. Atmospheric protection from nitrogen and oxygen;
2. Arc stabilization;
3. Flux that will provide chemicals that react with
oxygen to form solid metal oxides which
either become part of the slag or go into solid
solution;
4. Slag that has high fluidity, wets and spreads
vigorously, and adheres well to the weld face
but does not result in unacceptable undercut;
and
5. Slag that is easily removed when cool.
The expression “different but not difficult” can be
Covered Electrode Groups
Covered electrodes for nickel are divided into five
alloy groups: nickel, nickel-copper, nickel-chromiumiron, nickel-molybdenum, and nickel-chromiummolybdenum. Each group contains one or more electrode classification based on the composition of undiluted weld metal. Table 4.15 lists the weld metal
composition of the various commercially available covered electrodes.
Covered electrodes are generally designed for use
with direct current electrode positive (DCEP), i.e., electrode positive and workpiece negative. Each electrode
14. American Welding Society (AWS) Committee on Filler Metals
and Allied Materials, 2010, Specification for Nickel and Nickel-Alloy
Welding Electrodes for Shielded Metal Arc Welding, ISBN 978-087171-769-6, Miami: American Welding Society.
CHAPTER 4—NICKEL AND COBALT ALLOYS
307
type and diameter has an optimum current setting in
which it has good arcing characteristics; outside of this
range, the arc becomes unstable, the electrode overheats, the covering spalls, or excessive spatter is
encountered. The current density for a given welded
joint, however, is influenced by base-metal thickness,
welding position, type of backing, tightness of clamping, and joint design. Table 4.16 shows approximate
current settings for three alloy groups for flat-position
welding. It should be noted that current ranges vary by
manufacturer.
The recommended amperage ranges are typically
available from the manufacturer of the electrodes.
These ranges should be used as guidelines. Records of
actual welding conditions should be developed during
weld procedure specification and procedure qualification by use of the same electrode, base metal type and
thickness, and the welding position that will be used in
production. When welding conditions have been established, it is important to adhere to the recommended
current range.
Covered electrodes should be left in the original
sealed, moisture-resistant containers in a dry storage
area prior to use. All opened containers should be
stored in a cabinet with a desiccant, or held at a temperature difference of 6°C to 8°C (10°F to 15°F) above the
highest expected ambient temperature. Electrodes that
have absorbed moisture can be reclaimed by baking
in an oven according to the recommendations of the
manufacturer.
Bare Rods and Electrodes
Bare nickel-alloy rods and electrodes are divided into
five groups, as are coated electrodes, although there are
more classifications in most groups of bare filler metals.
They are designed to weld base metals of the same composition using gas tungsten arc welding (GTAW), gas
metal arc welding (GMAW), plasma arc welding
(PAW), and submerged arc welding (SAW). These processes are not applicable to all alloys (refer to Table
4.7). The properties of some filler metal compositions
are balanced (i.e., allowance is made for dilution) so
they can be applied to surfaces that have less corrosion
resistance or can be used to join dissimilar metals (i.e.,
allowance is made for dilution). Also, because of the
high arc current and high temperatures of the weld
pool, filler metals are alloyed to resist the formation of
porosity and the tendency for hot cracking of the weld.
The compositional change is primarily achieved by
the addition of elements such as titanium, manganese,
and niobium. Frequently, the percentage of the major
elements in the filler metal can be higher than that of
the base metal; this composition is designed to diminish
the effects of dilution when applying surfacing to base
metals with less corrosion resistance than the surfacing
0.10
W86172
W84190
W86132
W86133
W86182
W86134
W86152
W86094
W86095
W86025
W86155
W86045
W80001
W80004
ENiCr-4
ENiCu-7
ENiCrFe-1
ENiCrFe-2
ENiCrFe-3
ENiCrFe-4
ENiCrFe-7g
ENiCrFe-9
ENiCrFe-10
ENiCrFe-12
ENiCrFe-13h
ENiCrFeSi-1
ENiMo-1
ENiMo-3
0.12
0.05
to
0.20
0.07
0.10
to
0.25
0.05
0.20
0.15
0.05
0.20
0.10
0.10
0.08
0.15
C
0.10
AWS
UNS
Classification Numberc
ENi-1
W82141
1.0
1.0
2.5
1.0
1.0
to
4.5
1.0
to
3.5
1.0
1.0
to
3.5
5.0
to
9.5
1.0
to
3.5
5.0
3.5
4.0
1.5
Mn
0.75
21.0
to
25.0
4.0
to
7.0
4.0
to
7.0
0.04
0.04
0.04
0.020
0.04
0.02
12.00
8.0
to
11.0
Rem
0.02
0.03
0.03
0.03
0.03
0.03
0.02
0.02
P
0.03
7.0
to
12.0
12.00
12.00
10.00
12.0
11.0
2.5
1.0
Fe
0.75
0.03
0.03
0.03
0.015
0.02
0.015
0.015
0.015
0.02
0.015
0.02
0.015
0.015
0.02
S
0.02
1.0
2.5
to
3.0
1.0
0.75
1.0
0.75
0.75
0.75
1.0
1.0
0.75
0.75
1.5
1.0
Si
1.25
Rem
Rem
52.0
to
62.0
Rem
Rem
55.0
min.
55.0
min.
Rem
60.0
min.
59.0
min.
62.0
min.
62.0
to
69.0
62.0
min.
Rem
Nid
92.0
min.
(Continued)
0.50
0.50
0.30
0.30
0.20
0.50
0.50
0.50
0.50
0.50
0.50
0.50
Rem
0.25
Cu
0.25
2.5
2.5
1.0
0.10
1.0
—
—
(e)
—
(e)
(e)
—
—
—
Co
—
—
—
0.30
1.5
to
2.2
0.50
—
—
0.50
—
—
—
—
0.75
—
Al
1.0
Weight-Percent a, b
—
—
—
0.10
to
0.40
0.50
—
—
0.50
—
1.0
—
—
1.0
Ti
1.0
to
4.0
—
2.5
to
5.5
13.0
to
17.0
13.0
to
17.0
13.0
to
17.0
13.0
to
17.0
28.0
to
31.5
12.0
to
17.0
13.0
to
17.0
24.0
to
26.0
28.5
to
31.0
26.0
to
29.0
1.0
48.0
to
52.0
—
Cr
—
—
—
2.1
to
4.0
—
1.5
to
4.0f
0.5
to
3.0f
1.0
to
2.5f
1.0
to
3.5
1.0
to
2.5
0.5
to
3.0
1.0
to
3.5
—
1.0
to
2.5
—
Nb(Cb)
plus
Ta
—
Table 4.15
Chemical Composition Requirements for Nickel-Base Welding Filler Metal
26.0
to
30.0
23.0
to
27.0
3.0
to
5.0
—
2.5
to
5.5
1.0
to
3.5
—
1.0
to
3.5
0.5
0.60
0.60
—
—
1.0
1.0
—
—
1.5
to
3.5
—
—
—
1.5
—
—
—
—
—
—
—
—
—
—
—
W
—
—
—
—
0.5
to
2.5
—
—
—
V
—
—
—
Mo
—
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
Other
Elements
Total
0.50
308 CHAPTER 4—NICKEL AND COBALT ALLOYS
AWS WELDING HANDBOOK
0.10
W80008
W80009
W80675
W80629
W86007
W86002
W86112
W80276
W80002
W86620
W86455
W86985
W86022
W86030
ENiMo-8
ENiMo-9
ENiMo-10
ENiMo-11
ENiCrMo-1
ENiCrMo-2
ENiCrMo-3
ENiCrMo-4
ENiCrMo-5
ENiCrMo-6
ENiCrMo-7
ENiCrMo-9
ENiCrMo-10
ENiCrMo-11
0.03
0.02
0.02
0.015
0.10
0.10
0.02
0.05
to
0.15
0.10
0.05
0.02
0.02
0.10
C
0.02
AWS
UNS
Classification Numberc
ENiMo-7
W80665
1.5
1.0
1.0
2.0
to
4.0
1.5
1.0
1.0
1.0
1.0
to
2.0
1.0
2.5
2.0
1.5
1.5
Mn
1.75
18.0
to
21.0
2.0
to
6.0
13.0
to
17.0
3.0
4.0
to
7.0
4.0
to
7.0
10.0
1.0
to
3.0
2.0
to
5.0
18.0
to
21.0
17.0
to
20.0
7.0
7.0
10.0
Fe
2.25
0.015
0.02
0.04
0.03
0.03
0.02
0.03
0.04
0.04
0.03
0.03
0.03
0.04
0.04
0.02
0.03
0.04
0.03
0.03
0.03
0.04
0.04
0.03
0.015
0.015
S
0.03
0.04
0.02
0.02
P
0.04
1.0
0.2
1.0
0.2
1.0
1.0
0.2
0.75
1.0
1.0
0.2
0.2
0.75
0.75
Si
0.2
2.5
5.0
Rem
5.0
2.0
—
2.5
2.5
0.50
to
2.50
(e)
2.5
1.0
3.0
—
—
Co
1.0
Rem
Rem
Rem
55.0
min.
Rem
Rem
55.0
min.
Rem
Rem
Rem
Rem
62.0
min.
60.0
min.
Nid
Rem
—
—
—
—
—
—
—
—
—
—
0.70
—
—
—
—
—
—
—
—
0.3
—
—
—
Ti
—
0.1
to
0.5
—
—
—
—
Al
—
1.0
to
3.0
0.5
to
1.5
21.0
to
23.5
20.5
to
23.0
20.0
to
23.0
14.5
to
16.5
14.5
to
16.5
12.0
to
17.0
14.0
to
18.0
21.0
to
23.5
20.0
to
22.5
28.0
to
31.5
0.5
to
3.5
—
Cr
1.0
0.3
to
1.5
—
0.5
0.5
to
2.0
—
—
3.15
to
4.15
—
1.75
to
2.50
—
0.5
—
—
—
Nb(Cb)
plus
Ta
—
Mo
26.0
to
30.0
17.0
to
20.0
18.0
to
22.0
27.0
to
32.0
26.0
to
30.0
5.5
to
7.5
8.0
to
10.0
8.0
to
10.0
15.0
to
17.0
15.0
to
17.0
5.0
to
9.0
14.0
to
17.0
6.0
to
8.0
12.5
to
14.5
4.0
to
6.0
—
—
—
0.35
—
—
—
0.35
0.35
2.5
to
3.5
1.5
to
4.0
1.5
3.0
to
4.5
3.0
to
4.5
1.0
to
2.0
0.5
0.2
to
1.0
—
—
—
1.0
—
—
—
2.0
to
4.0
2.0
to
4.0
3.0
W
1.0
—
V
—
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
Other
Elements
Total
0.50
CHAPTER 4—NICKEL AND COBALT ALLOYS
(Continued)
1.0
to
2.4
1.5
to
2.5
0.50
0.50
0.50
0.50
0.50
0.50
1.5
to
2.5
0.50
0.5
0.3
to
1.3
0.50
0.50
Cu
0.50
Weight-Percent a, b
Table 4.15 (Continued)
Chemical Composition Requirements for Nickel-Base Welding Filler Metal
AWS WELDING HANDBOOK
309
0.05
0.05
to
0.15
0.05
to
0.10
W86686
W86200
W86650
W86058
W86035
ENiCrMo-14
ENiCrMo-17
ENiCrMo-18
ENiCrMo-19 i
ENiCrMo-22
ENiCrCoMo-1 W86117
0.02
0.03
0.020
0.02
0.03
5.0
0.3
to
2.5
0.3
to
1.0
3.0
0.030
0.03
0.03
0.030
0.02
0.015
P
0.03
2.00
12.0
to
15.0
1.5
3.0
5.0
1.5
Fe
5.0
0.50
1.5
0.7
0.5
1.0
1.0
Mn
2.2
0.015
0.015
0.015
0.02
0.02
0.015
0.02
0.01
S
0.02
0.25
to
0.75
0.75
0.60
0.2
0.6
0.2
0.25
0.2
Si
0.7
0.50
0.50
0.30
0.5
1.3
to
1.9
0.3
0.50
0.50
Cu
0.50
Rem
Rem
Rem
Rem
Rem
Rem
Rem
Rem
Nid
Rem
9.0
to
15.0
5.0
1.00
0.3
1.0
2.0
—
—
Co
—
0.10
—
—
0.50
0.20
—
—
—
0.25
—
Ti
—
0.40
0.4
0.5
—
—
—
Al
—
Cr
20.5
to
22.5
22.0
to
24.0
19.0
to
23.0
22.0
to
24.0
19.0
to
22.0
20.0
to
23.0
32.25
to
34.25
21.0
to
26.0
20.0
to
24.0
—
1.0
0.50
—
0.3
—
—
Nb(Cb)
plus
Ta
1.0
to
2.8
—
Mo
8.8
to
10.0
15.0
to
16.5
15.0
to
17.0
15.0
to
17.0
10.0
to
13.0
19.0
to
21.0
7.6
to
9.0
8.0
to
10.0
1.0
to
3.0
13.0
to
15.0
—
—
—
0.60
1.0
to
2.0
0.3
3.0
to
4.4
—
—
W
—
0.20
—
0.15
—
—
—
V
—
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
Other
Elements
Total
0.50
a. The weld metal shall be analyzed for the specific elements for which values are shown in this table. If the presence of other elements is indicated in the course of the work, the amount of those
elements shall be determined to ensure that their total does not exceed the limit specified for “Other Elements, Total” in the last column of the table.
b. Single values are maximum, except where otherwise specified. Rem = remainder.
c. ASTM DS-56/SAE-1086, Metals & Alloys in the Unified Numbering System.
d. Includes incidental cobalt. Rem = remainder.
e. Cobalt—0.12 maximum, when specified by the purchaser.
f. Tantalum—0.30 maximum, when specified by the purchaser.
g. Boron is 0.005% maximum and Zr is 0.020% maximum when specified by purchaser.
h. B is 0.003% max. and Zr is 0.020% max.
i. UNS number formerly was W86040.
j. N = 0.02 to 0.15.
Source: Adapted from American Welding Society (AWS) Committee on Filler Metals and Allied Materials, 2010, AWS A5.11/A5.11M:2010, Specification for Nickel and Nickel-Alloy Welding Electrodes
for Shielded Metal Arc Welding, Miami: American Welding Society, Table 1.
ENiCrWMo-1 W86231
0.02
W86059
ENiCrMo-13
0.02
C
0.03
AWS
UNS
Classification Numberc
ENiCrMo-12 W86032h
Weight-Percent a, b
Table 4.15 (Continued)
Chemical Composition Requirements for Nickel-Base Welding Filler Metal
310 CHAPTER 4—NICKEL AND COBALT ALLOYS
AWS WELDING HANDBOOK
AWS WELDING HANDBOOK
CHAPTER 4—NICKEL AND COBALT ALLOYS
311
Table 4.16
Approximate Current Settings for Nickel-Base Covered Electrodesa
Nickel-Copper Alloys
Base-Metal
mm
Nickel Alloys
Thicknessb
in.
Base-Metal
Current, A
Ni-Cr-Fe and Fe-Ni-Cr Alloys
Thicknessb
mm
in.
Base-Metal Thicknessb
Current, A
mm
in.
Current, A
Electrode Diameter = 2.4 mm (0.094 in.)
1.57
0.062
50
1.57
0.062
75
≥1.57
1.98
0.078
55
1.98
0.078
80
—
—
—
2.36
0.094
60
≥2.36
≥0.094
85
—
—
—
≥2.77
≥0.109
60
—
—
—
—
—
—
≥0.062
60
Electrode Diameter = 3.2 mm (0.125 in.)
2.77
0.109
65
2.77
0.109
105
2.77
0.109
75
3.18
0.125
75
≥3.18
≥0.125
105
3.18
0.125
75
3.56
0.141
85
—
—
—
—
—
—
≥3.96
≥0.156
95
—
—
—
≥3.96
≥0.156
80
Electrode Diameter = 4.0 mm (0.156 in.)
3.18
0.125
100
3.56
0.141
110
3.56
0.141
130
—
—
—
3.96
0.156
115
3.96
0.156
135
—
—
—
—
—
≥4.75
≥0.188
150
≥4.75
150
—
—
—
—
≥6.35
≥0.250
3.18
0.125
—
110
—
—
≥0.188
—
—
105
—
Electrode Diameter = 4.8 mm (0.188 in.)
—
9.53
≥12.7
—
—
6.35
0.250
180
—
0.375
170
≥9.53
≥0.375
200
≥9.53
≥0.500
190
—
—
—
—
—
≥0.375
—
—
140
—
a. Selection of electrode diameter should be based on joint design. For example, smaller diameters than those listed for material 3.18 mm (0.125 in.) and
greater in thickness may be necessary for the first passes in the bottom of a groove joint.
b. For base-metal thicknesses less than 1.57 mm (0.062 in.), the amperage should be the minimum at which arc control can be maintained for all three electrode
groups shown.
material. This composition also accommodates the
welding of dissimilar metals.
Precipitation-hardening weld metals will normally
respond to the aging treatment used for the base metal;
however, the response of the weld metal usually will
not be as pronounced as that of the base metal and the
strength of the weld joint will be somewhat lower than
that of the base metal after aging.
Precipitation-hardening base alloys can be welded
with dissimilar filler metals that will minimize processing difficulties. For example, Alloy R-41 is commonly
welded with ERNiCrMo-3 or ERNiMo-3 filler metals.
As a result, the strength is significantly lower than that
of the base metal. The usual remedy for this deficiency
is to locate the weldment in an area of low stress.
For GMAW, the proper electrode diameter depends
on the thickness of the base metal and the mode of
metal transfer. For spray, pulsed spray, and globular
transfer, electrode diameters ranging from 0.89 mm to
2.36 mm (0.035 in. to 0.093 in.) are used. With shortcircuiting transfer, diameters of 1.14 mm (0.045 in.) or
smaller are usually required.
Fluxes
Fluxes are available for the submerged arc welding
of many of the nickel alloys. In addition to protecting
312
CHAPTER 4—NICKEL AND COBALT ALLOYS
AWS WELDING HANDBOOK
the molten metal from atmospheric contamination,
fluxes provide arc stability and contribute important
properties to the weld metal. Therefore, the filler metal
and the flux must be compatible, and both must be
compatible with the base metal. An incorrect selection
of flux can cause excessive slag adherence, weld cracking, inclusions, poor bead contour, and detrimental
changes in the composition of the weld metal. Fluxes
used for carbon steel and stainless steel are not suitable
for use with nickel alloys and cobalt alloys.
JOINT DESIGN
Various joint designs for butt joints in nickel and
cobalt alloys are shown in Figure 4.14. The first consideration in designing joints for these alloys is to ensure
proper accessibility. The root opening must be sufficiently sized to permit the electrode, filler metal, or
torch to reach the bottom of the joint. In addition to
accessibility, the characteristics of the weld metal produced in nickel and cobalt alloys must be considered.
E MAX.
E to G
BACKING
WELD
A to C
TEMPORARY
BACKING BAR
60°–80°
B to D
60°–80°
F to K
G to K
A to E
TEMPORARY
BACKING BAR
60°–80°
BACKING
WELD
C
A to E
C
15°–30°
D to E
D
J to M
J to L
A to E
Key:
A =
B =
C =
D =
E =
0 mm (0 in.)
0.8 mm (0.031 in.)
1.6 mm (0.062 in.)
2.4 mm (0.094 in.)
3.2 mm (0.125 in.)
R
F
G
H
J
=
=
=
=
4.8 mm (0.188 in.)
6.4 mm (0.250 in.)
7.9 mm (0.312 in.)
12.77 mm (0.500 in.)
K
L
M
R
=
=
=
=
BACKING
WELD
A to E
15.9 mm (0.625 in.)
31.8 mm (1.250 in.)
50.8 mm (2 in.)
4.7 mm to 7.9 mm (0.188 in. to 0.312 in.)
Figure 4.14—Suggested Designs for Arc Welded Butt Joints in Nickel Alloys and Cobalt Alloys
AWS WELDING HANDBOOK
CHAPTER 4—NICKEL AND COBALT ALLOYS
First, the most significant characteristic of these
alloys is the sluggish nature of molten weld metal. It
does not spread easily, thus requiring accurate metal
placement within the joint by the welder. Wide groove
angles are used.
Second, the force of the arc results in a greater reduction of the depth of fusion in nickel and cobalt alloys
than, for example, in carbon steel. The reduced depth
of fusion requires the use of a narrow root face.
Increases in amperage will not significantly increase the
depth of fusion. Figure 4.15 illustrates depth of fusion
for different materials welded at the same current setting.
313
Groove Welds
Beveling is not usually required for groove welds in
base metal thicknesses of 2.36 mm (0.093 in.) or less.
For thicknesses greater than 2.36 mm (0.093 in.), a Vgroove or U-groove weld should be used, or the joint
should be welded from both sides. Otherwise, incomplete joint penetration will result, leading to crevices
and voids that become vulnerable points for accelerated
corrosion in the root of the joint. It is generally the side
that is inaccessible that must withstand corrosion.
Notches can also act as potential stress raisers. Welds
with complete joint penetration usually are required
because many of the nickel and cobalt alloys are used in
elevated temperature service and in severely corrosive
media.
Root Passes
When the back side of the weld is inaccessible, gas
tungsten arc welding should be used for the root pass.
The GTAW process produces the smoothest bead contour. Inserts are commonly employed to provide a good
filler metal dilution of 50%. (Refer to Figure 4.6.)
(A) Low-Carbon Steel
Joint Designs for Submerged Arc Welding
The double-U groove is the preferred design for
all submerged arc welded joints that permits its
use. This design results in lower residual stress, it
can be completed in less time than other groove welds,
and it requires less filler metal. (Refer to Figure 4.5
for suggested groove joint designs for submerged arc
welding.)
(B) Type 304 Stainless Steel
(C) Alloy 600
Figure 4.15—Cross Section Showing Depth of
Fusion in Three Base Metals Using the
Same Welding Conditions
Joint Designs for Gas Metal Arc Welding
The joint designs for GMAW are the same as those
used for SAW (refer to Figure 4.5), with two important
modifications: for the GMAW globular, spray, and
pulsed-arc welding modes, the root radius should be
decreased by about 50% and the groove angle should
be increased to as much as double those noted for SAW.
With the GMAW process, the use of high amperage
with small-diameter welding wires produces high arc
force, which is not easily deflected. Consequently, the
joint design must permit the arc to be directed at all
areas to be fused, i.e., U-groove joints should have a
bevel angle of 30°. This will permit proper manipulation
of the arc to obtain good fusion with the groove faces.
In consideration of proper access and the special
characteristics of nickel and cobalt alloy (e.g., reduced
spreading of weld metal and reduced depth of fusion),
314
CHAPTER 4—NICKEL AND COBALT ALLOYS
AWS WELDING HANDBOOK
corner joints and lap joints can be used when high
stresses are not anticipated in service. It is especially
important, however, to avoid using corner joints or lap
joints for use in high-temperature service or under thermal or mechanical cycling (fatigue) conditions.
Butt joints, in which stresses act axially, are preferred to corner and lap joints, in which stresses are
eccentric. In some configurations, butt joints are not
practical and it is necessary to use corner joints or
lap joints. When corner joints are used, a weld
with complete joint penetration must be made. In
most cases, a fillet weld on the inside corner will be
required.
(A) Incorrect Arrangement
CLAMPING
FIXTURE
POSITIONERS AND FIXTURES
Clamps, fixtures, or positioners can reduce the cost
of welding and ensure the consistent production of
high-quality welds in thin nickel or cobalt alloy sheet
and strip. Proper fixturing and clamping will facilitate
welding by holding the workpieces firmly, and rapidly
dissipating heat from the joint area. This minimizes
buckling and maintains alignment. An autogenous weld
can be subjected to compressive stress as it cools, thus
reducing the tendency toward cracking and increasing
weld reinforcement where it may be needed. Figure
4.16 illustrates an appropriate joint design and the
correct arrangement of fixtures for increasing weld
reinforcement.
Because the coefficient of thermal expansion of
nickel alloys does not differ greatly from that of lowcarbon steel, similar amounts of clamping pressure
will be needed. Table 4.17 shows comparative coefficients of thermal expansion for select nickel alloys, carbon steels, stainless steels and copper alloys. The
clamping pressure should not be excessive, but should
be only enough to maintain alignment. High-pressure
clamping is sometimes necessary, for example, when
the GTAW process is used to make arc seam welds in
thin base metal.
Preheating is not usually required or recommended,
although if the base metal is cold, heating to about
16°C (61°F) or higher will help to eliminate condensed
moisture that could cause weld porosity. Preheating is
not necessarily detrimental, but grain growth will occur
if cold-worked base metal is brought above the recrystallization temperature.
In most cases, the interpass and preheat temperatures
should be kept low to avoid overheating the base metal.
A maximum temperature of 90°C (194°F) is recommended for some corrosion-resistant alloys. Cooling
methods used to reduce preheat and interpass temperatures should be chosen with care to avoid inadvertent
introduction of contaminants. Examples of contami-
10°–15°
(B) Correct Arrangement
(C) Completed Weld
Figure 4.16—Basic Arrangement of Clamping
to Provide Weld Reinforcement
in Thin Nickel-Base Metals
Table 4.17
Coefficients of Thermal Expansion
for Select Materials
Coefficients of Thermal Expansion*
Alloy
μm/m/°C
μin./in./°F
200
13.0
7.2
400
13.0
7.2
600
11.5
6.4
800
14.4
8.0
SAE 1020 Steel
12.1
6.7
Stainless 304
17.3
9.6
Stainless 347
16.6
9.2
90-10 Cu-Ni
17.1
9.5
*At temperature range 0°C to 100°C (32°F to 212°F).
AWS WELDING HANDBOOK
nants include traces of oil from compressed air lines or
mineral deposits from a water spray.
CHAPTER 4—NICKEL AND COBALT ALLOYS
315
atmosphere. This can cause porosity in the weld metal.
The hot end of the filler metal rod should be kept
within the flame envelope to minimize oxidation.
Fluxes
OTHER WELDING PROCESSES
Welding processes used to weld nickel and cobalt
alloys are selected according to the application, the type
of nickel or cobalt alloys involved, and production
requirements. Each of the processes described in this
section, including oxyacetylene welding (OAW), resistance welding (RW), electron beam welding (EBW),
and laser beam welding (LBW), can provide advantages
to specific applications.
OXYACETYLENE WELDING
Oxyacetylene welding can be used to weld commercially pure nickel and some solution-strengthened nickel
alloys. Welds can be made in all positions. The oxyacetylene flame produces a sufficiently high temperature for
these welds; however, OAW should be used only in situations when arc welding equipment is not available.
The oxyacetylene welding process is still widely used
to apply nickel and cobalt alloys to dissimilar metal
weldments that require resistance to abrasion and wear.15
Flame Adjustment
The torch tip should be large enough to provide a
soft low-velocity flame. A harsh high-velocity flame
should be avoided. For the weld cladding of steel with
nickel and cobalt alloys, the tip usually should be the
same size or one size larger than the size recommended
for the same thickness of steel.
The welding torch should be adjusted with excess
acetylene to produce a slightly reducing flame. When
chromium-bearing alloys are welded, the flame should
not be excessively reducing because the weld metal
might absorb carbon.
During welding, the weld pool should be kept quiet
with the cone of the flame just touching the surface.
Agitation of the molten metal should be avoided, as this
action can result in the loss of the deoxidizing elements
or can expose the molten weld metal to the surrounding
15. Refer to Chapter 11 of American Welding Society (AWS) Welding Handbook Committee, 2004, Welding Processes, Part 1, ed. A.
O’Brien, vol. 2, Welding Handbook, 9th ed., Miami: American Welding Society. See Appendix B of this volume for a detailed description
of chapter contents of the five volumes of Welding Handbook, 9th ed.
Commercially pure nickel can be welded without
flux, but flux is required for welding nickel-copper,
nickel-chromium, and nickel-iron-chromium alloys.
The following flux mixture can be used for solutionstrengthened nickel-copper alloys: 60% barium
fluoride, 16% calcium fluoride, 15% barium chloride,
5% gum arabic, and 4% sodium fluoride.
Nickel-chromium and nickel-iron-chromium alloys
can be fluxed with a mixture of one part sodium
fluoride and two parts calcium fluoride with 3%
hematite (red iron oxide). A suitable wetting agent is
added to this mixture.16
Precipitation-hardening nickel-copper alloys can
be fluxed with a water slurry made of one part lithium
fluoride and two parts of either the nickel-copper alloy
flux composition or the nickel-chromium and nickeliron-chromium flux composition. The flux is mixed
with water to produce a thin slurry. It should be applied
to both sides of the joint and to the filler metal rod and
then allowed to dry before welding is started. Borax
must not be used as a flux when welding nickel alloys
because it can result in the formation of an undesirable
brittle eutectic in the weld.
After welding, flux residue must be removed from
the joint if the weldment will be used in high-temperature service. Molten flux remaining on the weldment
will corrode the base metal after an extended period.
Unfused flux can be washed off with hot water. Fused
flux is not soluble in water and must be removed
mechanically by grit blasting or grinding.
Nickel Alloys. Oxyacetylene welding is the only
recommended joining process for high-silicon casting
alloys. The welding procedures are similar to those
used for cast iron. The composition of the filler metal
rod should be the same as that of the base metal. A
U-groove weld with a 45° bevel angle should be used
for base metal that is greater than 13 mm (0.5 in.)
thick.
With the exception of the nickel-copper alloy, the
precipitation-hardening alloys should not generally be
welded by the OAW process because the hardening
elements are easily oxidized and fluxed away during
welding.
The OAW process is not recommended for joining
low-carbon nickel and nickel alloys, nickel-molybdenum
16. Examples of wetting agents are Photoflo by Kodak, Duponol ME
by DuPont, or commercial detergents.
316
CHAPTER 4—NICKEL AND COBALT ALLOYS
alloys, and nickel-chromium-molybdenum alloys. These
base metals can readily absorb carbon from the
flame, and this will reduce corrosion resistance and
high-temperature service properties.
Cobalt Alloys. Wrought cobalt alloys are usually low
in carbon. Like the low-carbon nickel alloys, wrought
cobalt alloys can absorb carbon during welding, which
will alter the properties of the alloys. Cobalt hardfacing
alloys, however, are high in carbon and are often
deposited with the oxyacetylene process.
RESISTANCE WELDING PROCESSES
Resistance welding (RW), including resistance spot
welding (RSW), resistance seam welding (RSEW), projection welding (PW) and flash welding (FW), can be
used to join nickel and cobalt alloys.17 These alloys are
readily welded to nickel and cobalt and to other metallurgically compatible metals. The electrical resistivity of
the alloys ranges from about 9.5 micro-ohm/centimeter
(μΩ·cm) (57 ohm circular mil per foot [Ω·cir mil/ft]) for
commercially pure nickel to 129 μΩ·cm (776 Ω·cir mil/
ft) for a resistance-heated nickel alloy. Welding current
requirements are lower for the high-resistance alloys,
but electrode force requirements increase because of the
high strength of these alloys at elevated temperatures.
For good electrical contact, the surfaces of the workpieces must be clean. All oxide, oil, grease, and other
foreign matter must be removed by acceptable cleaning
methods. Chemical pickling is the best method for
oxide removal.
AWS WELDING HANDBOOK
ments of the base metal properties. In most instances,
several combinations of welding parameters can
produce similar and acceptable results.
Equipment. Nickel and cobalt alloys can be welded
successfully on almost all types of conventional RSW
equipment. The equipment must provide accurate control of welding current, weld time, and electrode force.
Each of these values can vary within a range without
appreciably affecting weld quality; however, it is
prudent to have sufficient control over these variables
to obtain reproducible results after the optimum
values have been obtained for a given application.
Upslope controls will help prevent expulsion. Dual
electrode force systems are sometimes used to provide
a high forging force when welding high-strength,
high-temperature alloys. No significant changes in
welding characteristics or static weld properties can
be attributed to the use of any specific type of RSW
equipment.
For most applications, the restricted-electrode design
shown in Figure 4.17 is preferred. Truncated electrodes
or electrodes with radius faces of 125 mm or 200 mm
(5 in. or 8 in.) are sometimes used for metal thicknesses
in the range of 1.5 mm to 3 mm (0.06 in. to 0.13 in.).
Larger nuggets and correspondingly higher shear
strength can be obtained with these electrode shapes.
Electrodes. Group A, Classes 1, 2, and 3 electrode
alloys, classified by the Resistance Welding Manufac-
Resistance Spot Welding
Resistance spot welding can be used to join nickel
and cobalt alloys in much the same manner as other
metals. In many respects, RSW is easier for these alloys.
The joint configurations involved and the relatively
short welding time tend to preclude contamination
from the atmosphere. As a result, auxiliary shielding is
not usually needed during RSW.
The thermal and electrical conductivity and the
mechanical properties of the alloys vary, depending on
the composition and condition (annealed, thermal, or
other) of the specific alloy. Welding parameters for
RSW, therefore, are adjusted according to the require17. Refer to Chapters 1-3 of American Welding Society (AWS) Welding Handbook Committee, 2004, Welding Processes, Part 2, ed. A.
O’Brien and C. Guzman, vol. 3, Welding Handbook, 9th ed., Miami:
American Welding Society. See Appendix B of this volume for a
detailed description of chapter contents of the five volumes of Welding
Handbook, 9th ed.
FACE RADIUS
10°–30°
FACE DIAMETER
Figure 4.17—Restricted-Dome Electrode
Design for Resistance Spot Welding
AWS WELDING HANDBOOK
turing Alliance (RWMA) are recommended.18 Class 1
and Class 2 alloys are best for low-resistivity alloys and
for thin sheets to minimize the tendency for electrode
sticking. Class 3 electrodes are recommended for hightemperature alloys to minimize mushrooming that can
occur with high electrode forces and relatively long
weld times.
Welding Conditions. Resistance spot welding
parameters for multiple layers of nickel alloys are primarily determined by the total thickness of the layers,
and to a rather large extent, by the functions of the
welding machine to be used. Similar welding conditions
can be suitable for making welds in the same total
thickness when the number of layers differs significantly. For any given thickness or total aggregation,
however, various combinations of welding current,
time, and electrode force can produce similar welds.
Other conditions, including electrode size and shape,
are important for controlling characteristics such as
metal expulsion, sheet indentation, and sheet separation. Upslope, downslope, and forging force can be
used for some high-strength, high-temperature alloys to
control the heating rate and the soundness of the weld
nugget.
Nickel and cobalt alloys that have properties similar
to steel respond to resistance spot welding in a manner
similar to steel. The high-nickel and high-cobalt alloys
are generally harder and stronger than low-carbon
steel, particularly at elevated temperatures; therefore
higher electrode forces are required during spot welding. The time of current flow should be as short as possible, but sufficiently long to promote gradual buildup
of the welding heat. Welding current should be set
somewhat above the value that produces a weak weld,
but below the setting that causes expulsion of the weld
metal. Current upslope is an asset for control in this
respect.
Suitable conditions for the spot welding of annealed
nickel alloys with a single-phase welding machine are
noted in Table 4.18; Table 4.19 shows typical conditions for spot welding with a three-phase converter
welding machine. A forging force is sometimes applied
near the end of the weld time to consolidate the weld
nugget. For some alloys, forging force can be applied
during a postheating impulse.
Precipitation-hardening alloys are best welded when
in the solution-annealed condition. Settings similar to
those used for comparable solid-solution alloys should
be used; however, high electrode force and low welding
current must be used to compensate for the high-temperature strength and high electrical resistance of these
18. Resistance Welding Manufacturing Alliance (RWMA), 2003,
Resistance Welding Manual. Philadelphia: Resistance Welding Manufacturing Alliance. (RWMA is associated with the American Welding
Society.)
CHAPTER 4—NICKEL AND COBALT ALLOYS
317
alloys. The weld nuggets will be about the same size as
those in the solid-solution alloys, but shear strength will
be higher in the welded condition. Subsequent precipitation hardening will increase shear strength by about
50%. Cracking will generally occur when these alloys
are welded in the hardened condition. To avoid strainage cracking, postweld solution annealing, followed by
precipitation hardening, is recommended.
Some cracking can occur during spot welding of
some precipitation-hardening alloys if insufficient electrode force is used. If higher electrode force does not
overcome cracking, increasing the weld time or lowering the welding current will help. Welding machines
with low-inertia heads and slope control of the current
are preferred.
Resistance Seam Welding
Resistance seam welding (RSEW) is generally used to
join sheet thicknesses ranging from 0.05 mm to 3.2 mm
(0.002 in. to 0.125 in.). Circular electrode alloys classified in Resistance Welding Manufacturing Alliance
(RWMA) Group A, Class 1 or 2 are used. Individual
overlapping spots are created by coordinating the welding time and electrode wheel rotation. The circular electrodes can be rotated continuously or intermittently.
Continuous seam welding imposes limitations on the
weld cycle variations that can be used. For example, a
forging force cannot be applied during continuous seam
welding, but it can be used with intermittent motion.
High-strength alloys, such as Alloys X and X-750, are
usually welded with forging force and intermittent
drive.
Suggested conditions for the seam welding of nickel
alloys with continuous motion are provided in Table
4.20. Table 4.21 shows conditions for welding Alloy X
when using intermittent motion and forging force. The
force must be high to consolidate the weld nugget,
which will prevent cracking and porosity.
Projection Welding
Projection welding (PW) requires die-formed projections, similar to those used for steel, in one or both
workpieces. The workpieces are usually die-formed for
high-production operations. Nickel and cobalt alloys
are rarely joined by PW because production requirements are normally low.
Welding conditions for PW of nickel and cobalt
alloys are influenced by the thickness and shape of the
workpieces. Generally, higher electrode forces and
longer weld times than those used for steels are required
because of the higher strength of nickel and cobalt
alloys at elevated temperatures.
0.093
0.125
0.010
0.015
0.021
0.031
0.062
2.362
3.175
0.254
0.381
0.533
0.787
1.574
254
152
152
152
152
76
76
76
76
76
76
76
76
76
76
76
76
76
76
76
mm
Radius
a. Two equal thicknesses.
b. Restricted dome electrode design.
0.063
1.600
0.063
1.600
0.031
0.031
0.787
0.021
0.021
0.533
0.787
0.125
3.175
0.533
0.094
2.387
0.093
0.063
1.600
0.125
0.031
0.787
3.175
0.021
0.533
2.362
in.
mm
Thicknessa
5.59
7.87
10
4.83
4.06
4.06
11.18
9.65
7.87
4.83
4.06
12.7
9.65
7.87
4.83
4.83
9.65
7.87
6.35
4.83
4.06
mm
6
6
6
6
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
in.
in.
0.31
0.22
0.19
0.16
0.16
0.44
0.38
0.31
0.19
0.16
0.50
0.38
0.31
0.19
0.19
0.38
0.31
0.25
0.19
0.16
Diameter
Electrode Faceb
lb
3300
2300
1720
900
370
20
12
5000
2760
2700
700
300
30
20
12
12
12
5270
3870
2070
700
300
30
20
12
12
12
19 571
7784
3336
1779
1334
4400
1750
750
400
300
14
8
6
4
2
73Ni-16Cr-7 Fe-3Ti Alloy (UNS N07750)
23 441
17 214
9207
3114
1334
76Ni-16Cr-8 Fe Alloy (UNS N06600)
22 241
12 277
12 010
3114
1334
6
4
4
Weld Time,
cycles
(60 Hz)
67Ni-32Cu Alloy (UNS N04400)
14 679
10 231
7651
4003
1646
Nickel (UNS N02200)
N
Electrode Force
16.4
9.9
7.5
7.4
7.3
20.1
15.0
12.0
6.7
4.0
30.0
22.6
15.3
10.5
6.2
31.0
26.4
21.6
15.4
78.8
Welding
Current,
kA
7.37
4.32
3.56
2.79
2.79
11.18
9.40
7.87
4.57
3.05
11.94
9.40
7.87
4.32
3.30
9.40
7.87
6.35
4.57
3.05
mm
0.29
0.17
0.14
0.11
0.11
0.44
0.37
0.31
0.18
0.12
0.47
0.37
0.31
0.17
0.13
0.37
0.31
0.25
0.18
0.12
in.
Nugget Diameter
Table 4.18
Typical Conditions for Spot Welding Annealed Nickel Alloys with Single-Phase Machines
28 468
19 572
12 233
4092
2424
26 022
17 259
9163
3759
2002
24 910
16 014
10 676
3381
1557
N
6400
4400
2750
920
545
5850
3880
2060
845
450
5600
3600
2400
760
350
lb
Minimum
Shear Strength
318 CHAPTER 4—NICKEL AND COBALT ALLOYS
AWS WELDING HANDBOOK
0.093
0.125
0.025
0.031
0.043
0.062
0.093
2.362
3.175
0.635
0.787
1.092
1.575
2.362
203
203
127
127
76
305
229
178
127
127
76
mm
Radius
8
8
5
5
3
12
9
7
5
5
3
in
11.18
7.87
6.35
6.35
5.59
12.7
11.18
7.87
6.35
6.35
4.83
mm
0.44
0.31
0.25
0.25
0.22
0.50
0.44
0.31
0.25
0.25
0.19
in.
Diameter
Weld
Pulse
5000
3800
2200
1600
800
400
65
39
21
17
13
13
10
9
10
8
6
6
67Ni-32Cu Alloy (UNS N04400)
N
22 241
15 569
12 010
9786
8896
5000
3500
2700
2200
2000
9
53
35
23
10
8
8
5
9
8
1
1
1
1
1
1
1
1
1
1
1
Interpulse
Time, cycles (60 Hz)
73Ni-16Cr-7Fe-3Ti Alloy (UNS N07750)
22 241
16 903
9786
7117
3559
1779
lb
Electrode Force
a. Maximum thickness of multiple layers should not exceed four times this thickness. Maximum ratio for unequal thicknesses is 3 to 1.
b. Restricted dome electrode design.
0.043
0.062
0.030
0.762
1.574
0.018
0.457
1.092
in.
mm
Thicknessa
Electrode Faceb
15.0
11.4
8.1
6.8
6.0
31.0
22.5
14.5
11.5
8.5
4.3
Welding
Current,
kA
9.40
6.35
5.08
4.57
4.06
12.19
10.16
8.13
6.60
4.57
4.32
mm
0.37
0.25
0.20
0.18
0.16
0.48
0.40
0.32
0.26
0.18
0.17
in.
Nugget Diameter
25 355
14 679
8007
5115
4003
31 138
24 020
9119
7784
4003
1779
N
5700
3300
1800
1150
900
7000
5400
2050
1750
900
400
lb
Minimum
Shear Strength
Table 4.19
Typical Conditions for Spot Welding Annealed Nickel Alloys with Three-Phase Frequency Converter Machines
AWS WELDING HANDBOOK
CHAPTER 4—NICKEL AND COBALT ALLOYS
319
320
CHAPTER 4—NICKEL AND COBALT ALLOYS
AWS WELDING HANDBOOK
Table 4.20
Typical Conditions for Seam Welding Annealed Nickel Alloys
with Single-Phase Machines with Continuous Motion
Electrode Face
Thickness*
mm
in.
Width
mm
Electrode
Force
Radius
in.
mm
in.
N
Time, cycles
(60 Hz)
lb
Heat
Cool
Welding
Current,
kA
Welding Speed
Width of Nugget
mm/s
in./min
mm
in.
67Ni-32Cu Alloy (UNS N04400)
0.254
0.010
4.06
0.16
76
3
890
200
1
3
5.3
31.7
75
2.29
0.09
0.396
0.015
4.06
0.16
152
6
1334
300
1
3
7.6
31.7
75
2.54
0.10
0.533
0.021
4.83
0.19
152
6
2224
500
2
6
8.7
16.1
38
3.81
0.15
0.787
0.031
4.83
0.19
152
6
3114
700
4
12
10.0
8.0
19
3.81
0.15
1.574
0.062
9.65
0.38
152
6
11 120
2500
8
12
19.0
8.5
20
4.32
0.17
0.254
0.010
3.30
0.13
76
3
1779
0.396
0.015
3.30
0.13
76
3
0.533
0.021
4.06
0.16
76
3
0.787
0.031
4.83
0.19
76
1.574
0.062
4.83
0.19
152
73Ni-16Cr-7Fe-3Ti Alloy (UNS N07750)
400
1
3
3.6
19.0
45
2.79
0.11
3114
700
2
4
3.9
15.2
36
3.05
0.12
6227
1400
3
6
8.0
12.7
30
3.56
0.14
3
10 230
2300
4
8
8.5
12.7
30
4.32
0.17
6
17 792
4000
8
16
10.3
5.1
12
4.57
0.18
*Maximum thickness of multiple layers should not exceed four times this thickness. Maximum ratio for unequal thicknesses is 3 to 1.
Table 4.21
Seam Welding of 47Ni-22Cr-18Fe-9Mo Alloy (UNS N06002)
with Intermittent Motion and Forging Force
Thicknessa
Electrode Force
Electrodeb
Face Width
Weld
N
Weld Times, cycles
(60 Hz)
Forge
mm
in.
mm
in.
lb
N
lb
Total
0.762
0.030
4.83
0.19
6672
1500
—
—
1.600
0.063
7.87
0.31
8896
2000
17 792
4000
2.387
0.094
9.65
0.38
20 016
4500
20 016
4500
46
Forge
time,
cycles
(60 Hz)
Welding
Current,
kA
Spots
per
25.4 mm
(1 in.)
Heat
Cool
10
10
—
—
20.5
14
94
10
2
15
21.5
10
10
2
25
33.0
8
a. Two equal thicknesses.
b. RWMA Class 3 copper alloy wheel, 305 mm (12 in.) diameter, flat face, 15° double bevel.
Flash Welding
Flash welding can be used to join nickel-to-nickel
and cobalt-to-cobalt alloys and to dissimilar metals.
Flash welding is well adapted to the high-strength, heattreatable alloys for two reasons. First, molten metal is
not retained in the joint. Second, the hot metal at the
joint is upset. The upsetting action can improve the
ductility of the heat-affected zone.
The welding machine capacity required to weld
nickel and nickel alloys does not differ greatly from that
required for steel. This is especially true for transformer
capacity. The upset force needed for making flash welds
in nickel alloys is higher than that required for steel.
Joint designs for the flash welding of nickel and
cobalt alloys are similar to those used for other metals.
Flat, sheared, or saw-cut edges and pinch-cut rod or
wire ends are satisfactory for welding. Sometimes the
edges of thick base metal are slightly beveled. The overall shortening of the workpieces due to metal lost during welding should be considered in the design to
AWS WELDING HANDBOOK
CHAPTER 4—NICKEL AND COBALT ALLOYS
ensure that finished workpieces will be the proper
length.
Welding Conditions. The flash welding conditions
that are of greatest importance are flashing current,
speed, time, upset pressure, and distance. With strict
control of these conditions, the molten metal at the
weld interface will be forced out of the joint, and the
metal at the weld interface will be at the proper temperature for welding.
Generally, high flashing speeds and short flashing
times are used to minimize weld contamination. Parabolic flashing is more beneficial than linear flashing
because maximum joint efficiency can be obtained with
a minimum of metal loss.
Flash welding conditions vary with the size of the
welding machine and the application. Table 4.22 shows
typical conditions for the flash welding of a 6.3 mm and
9.5 mm (0.25 in. and 0.375 in.) diameter rod of several
nickel alloys.
Welding current is determined by adjusting the transformer tap setting of the machine. Because nickel alloys
have higher strength at elevated temperatures than
steel, higher force is required to upset and extrude all
the molten metal from the joint. The current flow and
time held during the upsetting stage is critical. If the
time is too long, the joint can overheat and oxidize. If
the time is too short, the plasticity of the metal will not
permit sufficient upsetting force to expel the molten
metal from the joint. A properly made flash weld does
not contain any cast metal.
321
ELECTRON BEAM WELDING
The electron beam welding (EBW) process can be
used to join all nickel and cobalt alloys that can be successfully joined by conventional arc welding processes.19 Because of the low heat input typical of this
process, it can be suitable for joining some alloys that
are considered difficult to weld with arc processes. In
general, the joint efficiency of electron beam welds will
equal or exceed that of GTAW.
Welding in vacuum provides excellent protection
against atmospheric contamination. Porosity can be a
problem when welding some alloys at high welding
speeds because dissolved gases do not have time to
escape to the surface of the weld pool. Weaving of the
beam to slightly agitate the weld pool can help the gases
escape and thus reduce porosity.
Hot cracking in the heat-affected zone may be a
problem, particularly when welding some of the thick
base metal alloys. The use of a cosmetic weld pass (second pass) to provide a good profile or face contour may
aggravate the problem because of the high restraint
imposed by the first weld pass. In this case, cracking is
prone to occur in the heat-affected zone of the cosmetic
weld bead.
19. Refer to Chapter 13, of American Welding Society (AWS) Welding Handbook Committee, 2007, Welding Processes, Part 2, ed. A.
O’Brien and C. Guzman, vol. 3, Welding Handbook, 9th ed., Miami:
American Welding Society. See Appendix B of this volume for
detailed descriptions of chapter contents of the five volumes of Welding
Handbook.
Table 4.22
Typical Conditions for Flash Welding Nickel Alloy Rodsa
Diameterb
Metal
Nickel
67Ni-32Cu
66Ni-30Cu-3Al
76Ni-16Cr-8Fe
UNS
Number
mm
N02200
N04400
N05500
N06600
Upset
Energy Input
in.
Upset Current
Time, s
mm
in.
W·h
Joint
Efficiency, %
6.35
0.25
1.5
3.17
0.125
7740
2.15
89
9.52
0.375
2.5
3.68
0.145
17 530
4.87
98
6.35
0.25
1.5
3.17
0.125
6950
1.93
97
9.52
0.375
2.5
3.68
0.145
19 980
5.55
95
6.35
0.25
1.5
3.17
0.125
7270
2.02
94
9.52
0.375
2.5
3.68
0.145
17 240
4.79
100
6.35
0.25
1.5
3.17
0.125
7740
2.15
92
9.52
0.375
2.5
3.68
0.145
18 680
5.19
96
a. Flash-off equals 11.2 mm (0.442 in.) and flashing time equals 25 seconds in all cases.
b. Ends tapered with 110° included angle.
J
322
CHAPTER 4—NICKEL AND COBALT ALLOYS
(A) Cosmetic Pass Penetrates to
Point B (3x, Reduced 65%)
AWS WELDING HANDBOOK
(B) Microcrack in Area A of the Heat-Affected
Zone at the Weld Interface (50x, Reduced 83%)
Figure 4.18—Photomacrographs of an Electron Beam Weld in
45 mm (1.75 in.) Thick Ni-19Cr-19Fe-5Nb-3Mo Alloy (N07718)
An example of this type of cracking is shown in Figure 4.18. The high degree of restraint imposed by the
thick base metal on the narrow heat-affected zone
can produce high tensile stress during cooling. Microcracking can readily take place, particularly if the alloy
tends to be hot short (a condition that occurs when the
metal reaches a temperature close to the melting point,
and then becomes susceptible to cracking as the weld
solidifies and cools.
An obvious solution to this problem is to use a welding procedure that does not require a cosmetic pass.
The addition of filler metal and subsequent mechanical
finishing can be used to achieve the appropriate result.
As required for arc welding, the base metal should be
in the annealed condition for electron beam welding.
With precipitation-hardening alloys, the weldment
should be solution treated and aged for optimum
strength properties; however, distortion of the weldment
must be considered when specifying a heat treatment.
Welding conditions for electron beam welding
depend on the composition and thickness of the base
metal, and also on the type of welding equipment. For a
given thickness of base metal, various combinations of
accelerating voltage, beam current, and travel speed can
produce satisfactory welds.
LASER BEAM WELDING
Laser beam welding (LBW) is a welding process that
produces coalescence with the heat from a laser beam
that impinges on the joint and is used for joining various
AWS WELDING HANDBOOK
nickel alloys.20 This process is usually conducted in an
open atmosphere using suitable gas shielding, i.e.,
argon or helium, to protect the weld area from oxidation. Several nickel alloys in thicknesses ranging from
0.3 mm to 10 mm (0.01 in. to 0.39 in.) have been
welded with various laser beam systems. The cross
sections of a laser-beam welded joint and the metallurgical characteristics are similar to those of electron
beam welds.
FABRICATION FOR HIGHTEMPERATURE SERVICE
Nickel alloys are used extensively in fabricated
equipment intended for high-temperature service. This
demanding service atmosphere brings out the inherent
weaknesses in welds characteristic of cast nickels that
possess a coarse dendritic structure. Thus, the resistance
to heat and fatigue of these welds is inferior, and the
long-term stress-rupture properties are generally not as
good as those of the relatively uniform-grained base
metals of wrought metal forms, e.g., sheet, plate, pipe,
and forgings. (Refer to Figure 4.1 for an illustration of
how such deficiencies can be handled by weld metal
selection at specific temperatures, even though the weld
metal composition may vary radically from the basemetal composition.) Consideration of the service environment is necessary when developing welding conditions for nickel alloys to be used in a high-temperature
service environment.
DESIGN REQUIREMENTS
The designer of weldments intended for high-temperature service should carefully select a weld metal composition that overmatches the base metal composition
in stress-rupture strength (refer to Figure 4.1). Additionally, the designer should be aware that the as-cast
weld metal should be protected from the effects of high
stresses by placing the welds in areas of minimal stress.
For example, a horizontally positioned pipe with a longitudinal weld should be positioned so that the weld
can be located at the top rather than at the bottom. The
20. Refer to Chapter 14 of American Welding Society (AWS) Welding Handbook Committee, 2007, Welding Processes, Part 2, ed. A.
O’Brien and C. Guzman, vol. 3, Welding Handbook, 9th ed., Miami:
American Welding Society. See Appendix B of this volume for a
detailed description of chapter contents of the five volumes of Welding
Handbook, 9th ed.
CHAPTER 4—NICKEL AND COBALT ALLOYS
323
top location places the weld in an area of compression
as the pipe sags when exposed to high temperature.
To minimize the effects of thermal and mechanical
fatigue, welds should be located in known areas of low
stress. Corners and areas where shape or dimensional
changes occur are invariably points of stress concentration and should not contain welded joints. Butt joints
are preferred because the stresses act axially rather than
eccentrically, which is typical in corner and lap joints.
Figure 4.19(A) shows a vulnerable weld location, and
Figure 4.19(B) shows a recommended design that will
allow the weld to perform as well as the base metal.
Such designs are initially costly, but often they are the
only means of achieving service life of the weld equivalent to that of the base metal.
If relocation of the joint is not possible, a completejoint-penetration weld should be used; a back weld
should be used if the joint root is accessible.
WELDING PROCEDURES
As a fundamental rule, welds should be made with
complete joint penetration. If the design permits, no
unfused areas should be left in the joint. Thermalfatigue failures can often be traced to incompletejoint-penetration welds that create stress concentrations. Figure 4.20 shows fatigue failure emanating
from an incomplete-joint-penetration weld in a heattreating basket.
Several designs that facilitate complete joint penetration are shown in Figure 4.21. The techniques used for
these designs are the following:
1. Beveling and root opening,
2. Root opening with round forms, and
3. Continuous weld all around.
In some applications of nickel-chromium-iron alloy
(N06600) and nickel-chromium-iron-aluminum alloy
(N06601), such as the repair welding of metal container
baskets used in carburization of steel parts, failure of
the weld over a period of time is a foregone conclusion.
In those instances, because the base metal is still viable,
a maintenance welding schedule should be introduced
to repair welds at appropriate service intervals. (Refer
to Figure 4.19 for an example of a weld failure that can
be repaired.)
If welds must be placed in areas where changes in
workpiece size or direction occur, carefully executed
welding procedures are required to minimize the inherent
higher stress concentrations. For example, it is
important to avoid undercutting, incomplete joint penetration, weld craters, and excessive weld reinforcement.
If complete joint penetration in rod or bar stock cannot
be attained, the weld should be continuous and the
324
CHAPTER 4—NICKEL AND COBALT ALLOYS
AWS WELDING HANDBOOK
MAXIMUM
STRESS
AREA WELD
VULNERABLE
(A) Poor Designs
EXTRUDED- WELDED
WALL
FITTING
FLANGE
MAXIMUM
STRESS
AREA WELD
RELOCATED
(B) Good Designs
Figure 4.19—Joint Designs for High-Temperature Service
Figure 4.20—Cross Section of Incomplete Joint
Penetration of a Weld in a Heat-Treating Basket
AWS WELDING HANDBOOK
CHAPTER 4—NICKEL AND COBALT ALLOYS
325
BEVELING
ROOT
OPENING
T-JOINT
ROOT
OPENING
SIDE BUTT JOINT
(A) Complete Joint Penetration Designs
LAP T-JOINT
CROSSOVER JOINT
(B) Weld-All-Around Techniques
Figure 4.21—Rod and Bar Joint Designs for High-Temperature Service
joint sealed so that none of the process atmosphere (a
corrodent) can enter to attack the root side of the weld.
The lapped T-joint and crossover joint designs previously illustrated (refer to Figure 4.20[B]) can be used.
Welds in heat-treating fixtures fabricated of round or
flat stock should blend smoothly into the base metal
without undercut. When fixtures are subject to many
heating and quenching cycles, wrap-around joints or
loosely fitted riveted joints are sometimes used to provide some freedom of movement.
WELDING SLAG
Welding slag and spatter are highly corrosive at elevated temperature, and great care must be taken to
ensure complete removal. Figure 4.22(A) shows the
inside of a tubular furnace operating at red heat in
which the slag was not removed. Corrosion through the
entire weld cross section occurs rapidly. Figure 4.22(B)
illustrates how catastrophic slag corrosion can be while
the surrounding base metal remains unaffected.
Welding slag becomes increasingly fluid in oxidizing
environments and then aggressively attacks the weld
and adjacent base metal.