DESIGN OF WELD JOINTS
&
WELDING ERRORS
ME 473 WELDING TECHNOLOGY
Instructor: Yrd.Doç.Dr. Oğuzhan Yılmaz
Department of Mechanical Engineering
The University of Gaziantep
Welding Technology
Design of Weld Joints and Welds
Five basic joints are used for bringing two members together
for welding:
1: Butt joint: a joint between two members aligned approximately in the
same plane.
2: Corner joint: a joint between two members located approximately at
right angles to each other in the form of an L.
3: T-joint: a joint between two members located approximately at right
angles to each other in the form of a T.
4: Lap joint: a joint between two overlapping members located in
parallel.
5: Edge joint: a joint between the edges of two or more parallel or
nearly parallel members.
When more than two members are brought together, the joint is a
combination of one of the five basic joint. The most popular joint is cross
or cruciform.
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Welding Technology
Five basic joints types
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Welding Technology
Weld Types
There are eight seperate and distinct welds:
Fillet weld:
weld:
This is the most commonly used weld. The fillet weld is so named because of its
cross-sectional shape. Simple and cheap to assemble & weld.
The fillet is regarded as being on the joint and is defined as a weld of
approximately triangular cross section joining of two surfaces approximately at
right angles to each other.
Toe
Weld face
Toe
Root
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Welding Technology
Weld Types
Groove weld:
weld:
This is the second most popular weld.
It is defined as a weld made in the groove between two members to be joined.
The groove weld is regarded as being in the joint.
There are 7 main basic groove weld designs, and they can be used as single or
double welds.
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Welding Technology
Weld Types
Back or backing weld:
This is a special weld made on the back side or root side of a previous weld.
The root of the original weld is gouged, chipped, or ground to sound metal
before backing weld is made. This will improve the quality of the weld joint by
assuring complete penetration.
Plug or slot welds:
These are made using prepared holes. They are considered together since the
welding symbol to specify them is the same.
If the hole is round , it is plug weld; if it is elongated, it is a slot weld.
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Welding Technology
Weld types
Spot or Projection welds:
These welds can be applied by different welding processes, which change the
actual weld; Resistance welding, electron beam welding, laser welding etc.
Seam welds:
This weld in cross section looks similar to a spot weld.
The weld geometry is influenced by the welding process employed.
Electron beam welding, laser, arc welding etc.
Stud weld:
This is a special type of a weld produced by a stud welding process, used for
joining a metal stud or similar part to a wokpiece.
Surfacing weld:
This weld is composed of one or more stringer or weave beads deposited on
base metal as an unbroken surface.
It is not used to make a joint.
It is used to build up surface dimensions, or provide protection of the base metal
from a hostile environment.
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Welding Technology
Weld types: Weld symbols
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Welding Technology
Weld types: Weld symbols
• A field welded fillet weld is required
on both sides of the “T” joint.
• The solid triangle (or flag) indicates
the weld is to be made in the field.
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Welding Technology
Weld types: Weld terminology
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Welding Technology
Weld types: Welding symbols
COMBINED WELDING SYMBOLS
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WELDING ERRORS
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Welding Technology
Welding errors & failures
Lack of Fusion
Lack of fusion occurs when there is no fusion between the weld
metal and the surfaces of the base metal.
Lack of fusion is caused by:
Too low current
Too high welding speed
Incorrect torch/gun angle
Incorrect angle preparation
There is no efficient non-destructive method. Visual inspection can
be used during welding and with bend test.
Also ultrasonic testing, liquid penetrant test or magnetic particle
testing methods can be applicable.
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Welding Technology
Welding errors and failures: Lack of Fusion
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Welding Technology
Welding errors and failures: Incomplete penetration
This type of defect is found in any of three
ways:
When the weld bead does not penetrate the
entire thickness of the base plate.
When two opposing weld beads do not
interpenetrate.
When the weld bead does not penetrate the toe
of a fillet weld but only bridges across it.
Welding current has the greatest effect on
penetration.
Incomplete penetration is usually caused by the
use of too low a welding current and can be
eliminated by simply increasing the amperage.
Other causes can be the use of too slow a
travel speed and an incorrect torch angle. Both
will allow the molten weld metal to roll in front of
the arc, acting as a cushion to prevent
penetration. The arc must be kept on the
leading edge of the weld puddle
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This type of defect can be easily
detected by visual inspection.
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Welding Technology
Welding errors and failures: Undercutting
Undercutting is a defect that appears as a groove
in the parent metal directly along the edges of the
weld.
It is most common in lap fillet welds, but can also
be encountered in fillet and butt joints.
This type of defect is most commonly caused by
improper welding parameters; particularly the travel
speed and arc voltage.
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Welding Technology
Welding errors and failures: Porosity
Porosity is the result of gas entrapment
in the solidifying metal.
Porosity can take many shapes on a
radiograph but often appears as dark
round or irregular spots or specks
appearing singularly, in clusters, or in
rows.
Sometimes, porosity is elongated and
may appear to have a tail. This is the
result of gas attempting to escape while
the metal is still in a liquid state and is
called wormhole porosity.
All porosity is a void in the material and it
will have a higher radiographic density
than the surrounding area.
wormhole porosity
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Welding Technology
Welding errors and failures: Inclusion
Solid inclusions are normally expected to be
a subsurface type of defect and would
include any foreign material entrapped in
the deposited weld metal.
The most common type of solid inclusion is
a slag inclusion defined as nonmetallic solid
material entrapped in weld metal or between
weld metal and base metal.
Slag
inclusion
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Welding Technology
Welding errors and failures: Weld cracks
A crack is a fracture-type discontinuity characterized by a sharp tip and high ratio
of length and width to opening displacement.
Cracks are perhaps the most serious of the defects that occur in the welds or weld
joints in weldments.
Cracks are considered dangerous because they create a serious reduction in
strength.
They can propagate and cause sudden failure. They are most serious when impact
loading and cold-temperature service are involed.
There are many types of cracks:
Surface cracks
Transverse cracks:
Longitudinal carcks:
Creater cracks:
Toe cracks
Underbead cracks
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Welding Technology
Welding errors and failures: Weld cracks
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Welding Technology
Welding errors and failures: Distortion
Most of the welding processes involve heat. High temperature heat is largely
responsible for welding distortion, warpage, and stresses.
When metal is heated it expands, and it expands in all directions.
Welding-distortion or deformation or warping of weldments during welding is a
natural outcome of intrinsic non-uniform heating and cooling of the joint.
Distortion is the result of the action of internal stresses which are produced while
welding, and remain in the part after heating is removed, as briefly explained in the
following.
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Welding Technology
Welding errors and failures: other errors
UNDERFILL
OVERLAP
SPATTER
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UNACCEPTABEL WELD
PROFILES
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End of the chapter….
&
End of the term…
Thank you
YOU ARE ALL NOW ‘WELDING SPECIALISTs’,
SPECIALISTs’, AREN’T YOU?
ALL THE BEST…
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