Fusion-Welding and Solid State
Welding Processes
Team 6:
Christopher Chavez
Steve De La Torre
David Jaw
Matthew Witkowski
November 23, 2005
ME260L
Topics:
General Safety
General Welding
OxyFuel Welding
Arc Welding
Solid-State Welding
Processes
Electron-beam Welding
(EBW)
Oxyfuel Cutting
Arc Cutting
Resistance Welding
General Welding Safety:
Every year approximately 500K Welding Accidents occur
Occupational Safety & Health Administration (OSHA)
•Standard 1910 Welding, Cutting and Brazing
Installation of equipment
Environmental Controls
Exposure Limits (Fumes, Vapor, and Time)
Operation and Maintenance
Common Accidents
•Flash and Retinal Burns
•Vapor Hazards
•Electric Shock
•Fires or Flammable accidents
General Welding Safety:
Personal Protective
Equipment (PPE)
Welder is properly
grounded
Adequate ventilation
Work in a Firesafe
zone
First-Aid kit
General Characteristics of Fusion Welding Processes:
Process Description
•Welding is the process by which 2 metal parts are joined
by melting the parts (application of heat) at the points of
contact. Most frequently used methods are Oxy-Fuel and
Electric Arc welding.
•There are more than 80 different types of welding
operation in commercial use.
General Characteristics of Fusion Welding Processes:
General Characteristics of Fusion Welding Processes:
TABLE 27.1
Joining process
Shielded metal-arc
Operation
Manual
Submerged arc
Automatic
Gas metal-arc
Semiautomatic
or automatic
Manual or
automatic
Semiautomatic
or automatic
Manual
Gas tungsten-arc
Flux-cored arc
Oxyfuel
Electron-beam,
Semiautomatic
Laser-beam
or automatic
* 1, highest; 5, lowest.
Advantage
Portable and
flexible
High
deposition
Most metals
Most metals
High
deposition
Portable and
flexible
Most metals
Skill level
required
High
Welding
position
All
Current
type
ac, dc
Distortion
1 to 2
Cost of
equipment
Low
Low to
medium
Low to
high
Low to
high
Low to
high
High
Flat and
horizontal
All
ac, dc
1 to 2
Medium
dc
2 to 3
All
ac, dc
2 to 3
Medium to
high
Medium
All
dc
1 to 3
Medium
All
—
2 to 4
Low
Medium
to high
All
—
3 to 5
High
*
OxyFuel or OxyAcetylene Gas Welding:
OxyFuel Gas Welding is a term used to describe any
welding process that uses a fuel gas with Oxygen.
The oxy-acetylene flame is made by mixing oxygen and
acetylene gases in a special welding torch or blowpipe,
producing, when burned, a heat of 6,300 degrees, which is
more than twice the melting temperature of the common
metals.
 Oxygen and acetylene (typically), to produce the flames.
 Filler Metals which may be added to the joints while molten
in order to give the weld sufficient strength and proper form
Chemical powders, called fluxes, which assist in the flow of
metal and in doing away with many of the impurities and
other objectionable features.
OxyFuel Gas Welding:
Torch Practice. The actual work of welding and cutting
requires preliminary preparation in the form of heat treatment
for the metals, including preheating, annealing and tempering
Oxygen, the gas which supports the rapid combustion of the
acetylene in the torch flame, is one of the elements of the air.
The equipment used for oxyacetylene welding consists of a
source of oxygen and a source of acetylene from a portable
or stationary outfit, along with a cutting attachment or a
separate cutting torch.
OxyFuel Gas Welding:
This apparatus used in
gas welding consists
basically of a torch, two
pressure regulators and twin
flexible hoses.
The regulators are
attached to the fuel and to
the oxygen sources. The
regulators are attached to
the tanks and drops the
pressure from about 21000
kPa (3000 lbf/in² = 200 atm)
to a lower pressure for the
torch.
OxyFuel Gas Welding:
(a) General view of and
(b) Cross-section of a torch
used in oxyacetylene
welding. The acetylene
valve is opened first; the
gas is lit with a spark
lighter or a pilot light;
then the oxygen valve is
opened and the flame
adjusted.
(c) Basic equipment used in
oxyfuel-gas welding. all
threads on acetylene
fittings are left-handed,
whereas those for
oxygen are right-handed.
Oxygen regulators are
usually painted green,
acetylene regulators red.
OxyFuel Gas Welding:
 Filler Metals
• Filler rods or Wire, Copper
alloy filler rods and fluxes
enable the joining of many
base metals. They are
especially useful on
steel and cast iron.
 Flux
• The flux is to retard
oxidation of the surface of
the parts being welding by
generating a gaseous
shield
OxyFuel Gas Welding:
Flames
•Neutral flame
•Welding is generally carried out
using the neutral flame setting which
has equal quantities of oxygen and
acetylene.
•Oxidizing Flame
•The oxidising flame is obtained by
increasing just the oxygen flow rate
•Carburizing Flame
•The carburising flame is achieved by
increasing acetylene flow in relation
to oxygen flow.
OxyFuel Gas Welding:
OxyFuel Gas Welding:
Arc Welding Process:
The term arc welding applies to a large
and varied group of processes that use an
electric arc as the source of heat to melt
and join metals. In arc welding processes,
the joining of metals, or weld, is produced
by the extreme heat of an electric arc
drawn between an electrode and the
workpiece, or between two electrodes.
Metal Electrodes. In bare metal-arc
welding, the arc is drawn between a bare
or lightly coated consumable electrode
and the workpiece. Filler metal is obtained
from the electrode.
Arc Welding Process:
Various Types of Arc Welding
•Nonconsumable-electrode or Gas Tungsten Arc
•GTAW or tungsten inert gas (TIG) welding, is a manual
welding process that uses a non-consumable electrode made
of tungsten, an inert or semi-inert gas mixture, and a separate
filler material. Especially useful for welding thin materials such
as Stainless Steel and light metals.
•Used on Bicycle, aircraft and naval applications.
•Plasma Arc
•PAW is an extension of the GTAW process. The arc is formed
between an electrode (which is usually but not always made of
a sintered tungsten) and the workpiece. The key difference
from GTAW is that in PAW, by positioning the electrode within
the body of the torch, the plasma arc can be separated from
the shielding gas envelope.
Arc Welding Process:
•Gas Tungsten Arc
The gas tungsten-arc welding process, formerly known as
TIG (for tungsten inert gas) welding.
Equipment for gas tungsten-arc welding
operations. Source: American Welding
Society.
Arc Welding Process:
•Plasma Arc
Two types of plasma-arc welding processes: (a) transferred, (b)
nontransferred. Deep and narrow welds can be made by this process at
high welding speeds.
Arc Welding Process:
•Electrodes for Arc Welding
•Electrodes are identified by numbers and letters or by color code
•Dimensions are in the range of 6 to 8 inches in length 1/16 to
5/16 in diameter.
•Classified by strength, current and type of coating.
•www.AWS.org
•A free information web site on any and all welding processes,
procedures, equipments etc…
Arc Welding Process:
•Shielding Metal Arc
•The arc is drawn between a covered consumable metal electrode and
workpiece.
•The electrode covering is a source of arc stabilizers, gases to exclude
air, metals to alloy the weld, and slags to support and protect the weld.
• Shielding is obtained from the decomposition of the electrode covering.
• Pressure is not used and filler metal is obtained from the electrode.
• Shielded metal arc welding electrodes are available to weld carbon and
low alloy steels; stainless steels; cast iron; aluminum, copper, and nickel,
and their alloys
Arc Welding Process:
•Shielding Metal Arc
Schematic illustration of the shielded metal-arc
welding process. About 50% of all large-scale
industrial welding operations use this process.
Schematic illustration of the shielded metal-arc
welding operations (also known as stick welding,
because the electrode is in the shape of a stick).
Arc Welding Process:
•Gas Metal Arc
•In this process, coalescence is produced by heating metals with an arc
between a continuous filler metal (consumable) electrode and the
workpiece.
•The arc, electrode tip and molten weld metal are shielded from the
atmosphere by a gas.
•Shielding is obtained entirely from an externally supplied inert gas, gas
mixture, or a mixture o f a gas and a flux.
•The electrode wire for MIG welding is continuously fed into the arc and
deposited as weld metal.
•Wire diameters 0.05 to 0.06 in. (0.13 to 0.15 cm) are average. Because
of the small sizes of the electrode and high currents used in MIG welding,
the melting rates of the electrodes are very high.
•All commercially important metals such as carbon steel, stainless steel,
aluminum, and copper can be welded with this process in all positions by
choosing the appropriate shielding gas, electrode, and welding
conditions.
Arc Welding Process:
•Submerged-Arc
•Basically, in submerged arc welding, the end of a continuous bare wire
electrode is inserted into a mound of flux that covers the area or joint to
be welded. An arc is initiated, causing the base metal, electrode, and flux
in the immediate vicinity to melt. The electrode is advanced in the
direction of welding and mechanically fed into the arc, while flux is
steadily added. The melted base metal and filler metal flow together to
form a molten pool in the joint. At the same time, the melted flux floats to
the surface to form a protective slag cover.
Arc Welding Process:
•Submerged-Arc
Schematic illustration of the submerged-arc welding process and equipment. The
unfused flux is recovered and reused. Source: American Welding Society.
Arc Welding Process:
Electron-beam Welding (EBW)
-heat generated by high
velocity narrow-beam
electrons
-the kinetic energy of the
electrons is converted
into heat
• Almost any metal can
be welded by this
process
• Depth-to-width ratios
range between 10
and 30
• Distortion and
shrinkage are minimal
• Weld quality is good
and of very high purity
Laser-beam Welding (LBW)
• High-power laser beam as the source of heat
which produces a fusion weld
• Deep-penetrating capability
• Laser beam is pulsed
for spot welding thin
materials
• Continuous laser
beam is used for
deep welds on thick
materials
Advantages of LBW over EBW
• A vacuum is not required
• Process is easier because
laser beams can be shaped
and manipulated
• Do not generate x-rays
• Quality is better: less tendency
for incomplete fusion, porosity,
and distortion
Cutting
Oxyfuel-gas and Arc Cutting
Oxyfuel-gas Cutting (OFC)
• The heat source is used
to remove material
instead of weld it
• Preheat the workpiece
with fuel gas
• The higher the carbon
content of the steel, the
higher the preheating
temperature
• Cutting takes place
after the oxidation
(burning) of the steel
Underwater Cutting
• Torches
create a
blanket of
compressed
air between
the flame
and the
surrounding
water
Arc Cutting
• Air carbon-arc
cutting (CAC-A)
– A carbon electrode
is used, and the
molten metal is
blown away by a
high-velocity air jet
Plasma-arc cutting (PAC)
-Produces the highest temperatures
-used for rapid cutting of nonferrous and
stainless-steel plates
• 3 distinct zones in a weld joint
1. Base metal
2. Heat-affected zone
3. Weld metal
Heat-affected zone (HAZ)
• Within the base metal
• The properties and microstructure of the HAZ depend on
the rate of heat input and cooling and the temperature to
which this zone was raised
Weld Quality
• Porosity
– Caused by gases released during melting of the weld
area but trapped during solidification
– Chemical reactions during welding
– Contaminants
Slag Inclusions
• Compounds such as oxides, fluxes, and electrodecoating materials trapped in the weld zone
Incomplete fusion and penetration
• Incomplete fusion produces poor weld beads
• Incomplete penetration occurs when the depth of the
welded joint is insufficient
Underfilling, Undercutting, and Overlapping
Cracks
• Types of cracks: longitudinal, transverse, crater,
underbead, and toe cracks
• Lamellar Tears develop because of shrinkage of the
restrained components of the structure during cooling
• Residual Stresses caused by expansion and
contraction of the weld area during heating and cooling
Weld Testing
• Destructive testing
– Tension test: longitudinal and transverse tension tests
are performed on specimens removed from actual
welded joints
– Tension-shear test: used so the shear strength of the
weld metal and the location of fracture can be
determined
– Bend Test: determines the ductility and strength of
welded joints
– Fracture toughness test: use impact testing
techniques
Fracture toughness test
Non-destructive testing techniques
-Visual
-Radiographic (x-rays)
-Magnetic-particle
-Liquid-penetrant
-Ultrasonic
Used instead of destructive for critical applications
where weld failure can be catastrophic
Joint Design and Process Selection
Select a type of weld and joint that is most practical for your application
Solid-State Welding
Processes
Introduction
• Solid-State Welding – a process in which joining
takes place without fusion at the interface of the
two parts to be welded.
• Involves one or more of the following
phenomena:
Diffusion
Pressure
Relative Interfacial Movements
Cold Welding
• Pressure is applied to the work pieces
throw dies or rolls
• Can be used to join small work pieces
made of soft ductile metals
• Example: Wire stock and electrical
connections
Roll Bonding
• Pressure is applied
through a pair of rolls
• This process can be
carried out at high
temperatures
Ultrasonic Welding
• The faying surfaces of the two components are
subjected to a static normal force and oscillating
shearing stresses.
• Frequency of oscillation is generally between
10kHz and 75kHz
• The shearing stresses cause plastic deformation
at the interface of the two components.
• The temperature generated in the weld zone is
usually in the range of one-third to one-half of
the melting point.
Friction Welding
• Heat required for welding is generated
from friction.
• One of the work piece components
remains stationary while the other is
places in a chuck and rotated at high
speed.
Resistance Welding
• Resistance Welding- process in which heat
required for welding is produced by means of
electrical resistance across the two components
being joined
• Advantages not requiring consumable
electrodes, shielding gases, or flux.
• Similar or dissimilar materials can be joined
• Resistance welding require specialized
machinery. Mostly Computer Controlled
Resistance Spot Welding
• Resistance Spot Welding
the tips of two opposing
solid, cylindrical touch a
lap joint and resistance
heating produces a spot
weld.
• Advantages limited work
piece deformation, high
production rates, easy
automation, and no
required filler materials
• Simplest and most
commonly used of the
resistance welding
processes.
• Widely used in fabricating
sheet-metal parts.
• Weld strength is
significantly lower than
with other welding
methods, making the
process suitable for only
certain applications
• Different machines for specific
tasks
• Rocker-arm type typically for
smaller parts
• Press-type used for larger
work pieces
Resistance Seam Welding
• Similar to spot welding with electrodes being
replaced by wheels or rollers.
• Continuous AC power supply is used.
• Able to create
continuous seam that
is liquid tight
• Roll spot welding
current applied
intermittently to create
series of welds.
• Process used in
making cans,
mufflers, gasoline
tanks.
High-Frequency resistance welding
• Process similar to seam welding except with
high frequency current.
• High frequency current used is up to 450 kHz
• Used in making tubing, I-beams, wheel rims.
Resistance projection welding
• In resistance projection
welding high electrical
resistance is developed
by embossing one or
more projections.
• Produces many welds in
one pass, prolongs
electrode life, capable of
welding metals of
different thicknesses.
Flash Welding
• Flash Welding also referred to
as flash butt welding, heat is
generated by the arc created
by two members, when proper
temperature is reached force is
applied and weld is formed by
plastic deformation of the joint.
• This process produces high
quality welds.
• Used in end in end joining,
joining sheets of metal, this is
the process used for creating
most rings.
Stud Welding
• Stud welding similar to flash welding however used with a metal
stud and a smaller part, often a rod.
• A ceramic ferrule in order to concentrate heat and prevent
oxidation.
• Used in automobile construction, electrical panels and building
construction.
Explosion Welding
• Explosive welding is a
solid state welding
process, which uses a
controlled explosive
detonation to force two
metals together at high
pressure
• The resultant composite
system is joined with a
durable, metallurgical
bond.
(a)
(b)
(c)
(d)
Diffusion Bonding
• Process in which the
strength of the bond
results primarily from
diffusion and secondly
from deformation of the
surfaces.
• Bonded interface will
essentially have the same
physical and mechanical
properties as the base
metal.
●Radiation light shielding
mask for a KEK accelerator
Diffusion bonding of Cu and Al
Diffusion bonding/Superplastic forming
• Sheet metal structures
can be formed by
combing diffusion
bonding and super plastic
forming.
• First diffusion bonded and
expanded in a mold.
• Used in aircraft and
aerospace applications.
3.
Resistance Spot Welding is known for its:
a.
Limited work piece deformation
Questions:
b.
High production rate and easy
automation
1.
c.
No need for filler metals
d.
All of above
What is one type of PPE is
required for Welding?
2.
a.
Eye Protection
b.
Hearing Protection
c.
Lent free Gloves
a.
Steel
d.
Respirator
b.
Aluminum
c.
None of the above
4.
What best describes “A Neutral
Oxyfuel cutting is used
Flame” in a Oxy-Fuel welding
process?
a.
5.
Solid State Welding involves healing
Equal amount of oxygen and
material to a molten state
acetylene
a.
True
b.
More oxygen than acetylene
b.
False
c.
More acetylene than oxygen
References:
1.
2.
3.
4.
http://fabfacts.com/articles/arc_welding.php?PHPSESSID=f3bb1649
4f14431b12c945e574eae3d4
http://en.wikipedia.org/wiki/Welding
http://www.aussieweld.com.au/index.htm
http://www.answers.com/main/ntquery?method=4&dsid=2222&dekey
=Welding&gwp=8&curtab=2222_1&linktext=welding