Team
Group 6 -Joining processes and Equipment»Cedric Turcotte
»Gavin Kurey
»David Barboza
»Marcos Gonzales
»Kevin Archibeque
Date:04/12/2006
Presentation Overview
Chapters
Chap. 30: Fusion Welding Processes
Chap. 31: Solid-State Welding Processes
Ch.30 sections 1-4
Fusion-Welding Processes:
•What is welding?
•Oxyfuel-Gas Welding
•Arc-Welding (Nonconsumable Electrode)
•Arc-Welding (Consumable Electrode)
Ch.30 sections 1-4
Introduction to Welding:
•Partial melting/fusion of two members along a joint
•Fusion welding – fusing material by means of heat
•Fillers
•Considerations
•Limitations
Ch.30 sections 1-4
Oxyfuel-Gas Welding (OFW):
•Any welding process using a fuel gas with
oxygen to make a flame
•Developed in the early 1900
•The flame produced is the source of heat
•Common fuel gasses are propane, acetylene
•Oxyacetylene-gas welding is the most
common variant
•Flame temperatures of 6000F
Ch.30 sections 1-4
OFW Continued, Flame types and Fillers:
•Oxygen to Gas Ratio
•Neutral (1:1) (oxidation risk!)
•Reducing (less oxygen, less combustion) – low heat applications
•Oxidizing (more oxygen) –only in copper applications
•Filler rod or Wire
•Flux
•Pressure-gas Welding
Ch.30 sections 1-4
Arc-Welding (Nonconsumable Electrode):
•Heat required for fusion is obtained from electricity
•An electric arc is produced between the workpiece and an electrode
•AC or DC power supplies
•Polarity
•Gas Tungsten Arc Welding - GTAW (TIG)
•Plasma Arc Welding - PAW
•Atomic Hydrogen Welding - AHW
Ch.30 sections 1-4
Gas Tungsten Arc Welding
(GTAW):
•Formerly TIG Welding
•No flux, uses an inert gas (Argon, Helium,
etc)
•Filler Rod
•DC @ 200A or AC @ 500A (Best for
aluminum)
•Can weld a variety of metals
•Contaminated Electrode problems
•Excellent surface finish and weld quality
•Portable
•Versatile
Ch.30 sections 1-4
Plasma Arc Welding (PAW):
•Developed in the 1960’s
•Temperatures exceeding 60,000F
•Ionized hot gas containing equal shares of electrons and ions
•Highly Concentrated
•Filler fed into the arc, like GTAW
•Shielding gas like Argon, Helium, etc
•Transferred Arc, Nontransferred methods
•Deep, Narrow Welds
•Great stability
•Low thermal distortion
Ch.30 sections 1-4
Ch.30 sections 1-4
Atomic Hydrogen Welding (AHW):
•Arc generated between two tungsten electrodes inside a hydrogen
atmosphere
•Arc is maintained seperately from the work piece
•Temperatures of 11000F
•Diatomic Hydrogen molecules breakdown under the heat of the arc and
recombine when they hit the workpiece, releasing energy.
Ch.30 sections 1-4
Arc-Welding (Consumable Electrode):
•Again, the heat necessary for fusion is derived from electrical energy
•Electrode is consumed as process occurs (a filler)
•Shielded metal arc welding (SMAW)
•Submerged arc welding (SAW)
•Gas metal arc welding (GMAW) (MIG)
•Flux core arc welding (FCAW)
•Electrogas welding (EGW)
•Electroslag welding (ESW)
Ch.30 sections 1-4
Shielded metal arc welding (SMAW):
•Oldest, simplest, most versatile welding process
•50% of all industrial and maintenance welding
•Stick welding
•Simple equipment
•SLAG!
Ch.30 sections 1-4
Submerged Arc Welding
(SAW):
•Weld arc is shielded by granular flux
•Flux could be lime, silica, manganese
oxide, etc
•Flux is fed to the weld via gravitational
feed hopper
•Flux can be reused
Ch.30 sections 1-4
Gas Metal Arc Welding (GMAW):
•Commonly known as MIG Welding
•Developed in the 1950’s
•Uses a shielding gas (Argon, Helium, CO2, etc)
•Cosumable bare wire is fed through torch
•Multiple weld passes are easily accomplished
•Low temperatures
•Easy to handle, very common
•Ferrous and non-ferrous metals
•Versatile, rapid, easy to learn!
Ch.30 sections 1-4
Flux-cored Arc Welding
•Very similar to GMAW
•Wire filled with a flux
•Flux/slag is easily removed
•Very versatile
•Common steel welding process
•Alloying can be accomplished
•Easy Automation
Ch.30 sections 1-4
Electrogas welding (EGW):
•A machine welding process
•Vertical welding in one pass
•Butt joints (edge to edge)
•Flux-cored or shielding gas
•Industrial applications
•Reliable
Ch.30 sections 1-4
Electroslag Welding (ESW):
•Similar in application to EGW
•Arc is between machine and work piece
•Flux is added/melted by arc
•Arc is only “on” at the outset of the welding pass
•Not strictly an arc-welding process
•Excellent penetration
•Good for thick pieces
•Many industrial apps
Electrode for Arc Welding
Electrode for Arc Welding
Electrodes are consumable and classified
according to:
•Strength of the deposited weld metal
•Current (AC / DC)
•Type of coating
Identified by numbers and letters, or color code
if they are to small to imprint.
Electrode for Arc Welding
Typical coated-electrode dimensions:
–From 6’’ to 18’’ in length;
–From 1/16 to 5/16 in diameter.
Electrodes are sold by weight.
Selection and recommendations found in
supplier literature or reference handbooks.
Electrode for Arc Welding
Electrode for Arc Welding
TABLE 27.2
The prefix “E” designates arc welding electrode.
The first two digits of four-digit numbers and the first three digits of five-digit numbers
indicate minimum tensile strength:
E60XX 60,000
psi minimum tensile strength
E70XX 70,000
psi minimum tensile strength
E110XX 110,000
psi minimum tensile strength
The next-to-last digit indicates position:
EXX1X
All positions
EXX2X
Flat position and horizontal fillets
The last two digits together indicate the type of covering and the current to be used.
The suffix (Example: EXXXX-A1) indicates the approximate alloy in the weld deposit:
—A1
0.5% Mo
—B1
0.5% Cr, 0.5% Mo
—B2
1.25% Cr, 0.5% Mo
—B3
2.25% Cr, 1% Mo
—B4
2% Cr, 0.5% Mo
—B5
0.5% Cr, 1% Mo
—C1
2.5% Ni
—C2
3.25% Ni
—C3
1% Ni, 0.35% Mo, 0.15% Cr
—D1 and D2
0.25–0.45% Mo, 1.75% Mn
—G
0.5% min. Ni, 0.3% min. Cr, 0.2% min. Mo, 0.1%min. V,
1% min. Mn (only one element required)
Electrode Coating
Outside coating made of silicate binders and
powdered materials (oxides, carbonates, fluorides, metal
alloys, and cellulose)
Functions
Stabilize the arc
Generate gases to act as a sheild against surrounding atmosphere.
Control rate at which the electrode melts
Acts as flux to protect against formation of oxides, nitrides, and inclusions
Add alloying elements to the melt zone, enhance the properties of joint.
Electrode Coating
Coating
Main electrode
Electrode Coating
Flux coating (slag) must be remove after each
pass to ensure a good weld.
Should not be remove too quickly, let the joint cool down a little first.
Electron-Beam Welding
Electron-Beam Welding
Heat is generated by high velocity narrowbeam electrons. The kinetic energy of the
electrons is converted in heat as they strike
workpiece.
Usually performed in a vacuum. The greater
the vacuum, the greater the penetration.
Electron-Beam Welding
Electron-Beam Welding
Electron beam welding (EBW)
EBW-HV: High vacuum
EBW-MV: Medium vacuum
EBW-NV: No vacuum
Electron-Beam Welding
Properties:
Workpiece can range from foil to 6’’ plate;
Depth to width ratio between 10 and 30;
Capacities or EBW guns range up to 100kW;
No flux, filler or shielding gas required;
Smaller heat affected zone;
Good quality weld;
Generates X-rays, hence periodic maintenance and monitoring
Weld speed as high as 40ft/min
Ex: Aircraft, missile, nuclear component, gears and shafts.
Laser-Beam Welding
Laser-Beam Welding
Laser-beam welding (LBW) utilizes a laser
beam as the heat source.
- Beam can be focused onto small area, it than has high energy for deeppenetrating capability.
- This process is suitable for welding deep in narrow joints with depth-towidth ratio raging from 4 to 10.
- Power level up to 100kW.
- Welding speed up to 250ft/min
- Can weld foil up to 1’’ plate
In automotive industry, it’s mostly use for welding transmission components
Laser-Beam Welding
Advantages of LBW over EBW
– No vacuum required;
– Laser beam can be shaped, manipulated and focused.
Easily automated;
– Do no generate X-rays;
– Better quality weld. Less tendency for incomplete fusion,
spatter, porosity ans distortion.
Laser-Beam Welding
Gillette Sensor razor cartridge
Made with Nd:YAG laser
Up to 3 million welds/hour
7 identical weld points/blade
Laser-Beam Welding
Comparison: LBW or EBW a) over arc welding b)
Cutting
Cutting (oxyfuel-gas)
A piece of material can be separated into two
or more parts with various contours by
removing a narrow zone in the workpiece.
Other then mechanical means, heat source
can be provided by torches, electric arcs, or
lasers.
Cutting (oxyfuel-gas)
Oxyfuel-gas cutting (torch)
•Similar to oxyfuel welding, but heat is now used to remove matter;
•Suitable particularly for steels;
•Heat is provided by reactions mainly from oxygen and iron. The heat
generated is often not sufficient to cut steels. The workpiece therefore has
to be preheated;
•Higher the carbon concentration, higher cutting temperature required;
•Cutting is obtain by the oxidation of the steel (burning, rusting);
•Cutting thickness depends on gases used. Up to 2’ with some cases;
•Process can be automated with multi-cutting piece.
Cutting (oxyfuel-gas)
200 mm thick plate
Cutting (oxyfuel-gas)
None traditional
pattern cutting made
possible by
automation.
Cutting (oxyfuel-gas)
This process
generates a kerf
(wave pattern similar to that
produce by saws)
Kerf range from 0.06’’ to
0.4’’
Cutting (arc cutting)
Based on same principale as arc welding
Leave a heat-affected zone that have to be
taken into account.
Cutting (arc cutting)
In Air Carbon-Arc Cutting (CAC-A)
•Carbon electrode is used;
•Air is used to blow molten metal away, hence doesn’t have to be oxidize;
•Noisy process;
•Hazardous due to blown molten metal.
Cutting (arc cutting)
Plasma-arc cutting (PAC)
•Highest cutting temperature;
•Used for rapid cutting of stainless steel
and nonferrous plates;
•Higher cutting productivity then oxyfuelgas cutting;
•Most popular process utilizing
programmable controllers;
Cutting (arc cutting)
CNC plasma
cutting system ->
Plasma cutter
Cutting (arc cutting)
Electron beams and Lasers
•Use for accurate cutting;
•Better surface finish;
•Kerf is narrower.
Weld joint, quality, and Testing
Weld Joint
• Three distinct zones in weld joint:
1)Base metal
2)Heat-affected zone
3)Weld metal
• Weld joint used without a filler is called autogenous.
Solidification of weld
• The solidification process is similar to casting and begins with the
formation of columnar grains
• These are relatively long and form parallel to heat flow therefore lie
parallel to the plane of the two components welded
Solidification of weld
• Grain structure and size depend on the specific metal alloy, the welding
technique, and type of filler metal.
• The weld begins in a molten state; has a cast structure  Cooled slowly
 Hoarse grains  Low strength, toughness, and ductility
Solidification of weld
• The resulting structure depends on the particular alloy, it’s composition,
and the thermal cycling to which the joint is subjected.
• Preheating general weld area prior to welding can control cooling rates
• Without preheating, heat produced during welding dissipates rapidly
through rest of parts being joined
Weld Quality
Weld Quality
Some things that could cause Discontinuities,
weaknesses in weld
• Thermal cycling and microstructural changes
• Inadequate or careless application
• Poor training
• Porosity
• Slag inclusions
• Incomplete fusion penetration
• The Weld profile
• Cracks
• Tears
Weld Quality
Overlap & Undercut
Porosity
• Gases released during melting of the weld area but trapped during
solidification
• Chemical reactions
• Contaminants
Weld Quality
Underfill, Crack & Incomplete fusion
Slag Inclusions
• Oxides, fluxes and electrode-coating materials that are trapped in the
weld zone
Weld Quality
Residual Stress
• Distortion, warping, and buckling of the welded parts
• Stress-corrosion cracking
• If portion of welded structure is removed from sawing or machining
• Reduced fatigue life of the welded structure
Testing of welds
Types of tests:
• Tension
• Tension-shear
• Bend
• Fracture toughness
• Corrosion and creep
Joint Design
• Product should minimize number of welds
• Weld locations should be selected to avoid excessive stresses and joining
locations
• Components should fit properly prior to welding
• Weld bead size should be kept to a minimum to conserve weld metal
Joint Design
Things to think about when welding:
Weld Quality
Chapter 31 Intro
•Solid State Welding- Jointing at the interface
without fusion.
•Solid State Bonding- Involves one of the
following phenomena:
•Diffusion- Transfer of atoms across an interface.
•Pressure- Plastic Deformation occurs at the interface.
•Relative Interfacial Movements- Movements of the
contacting surfaces occur
Cold Welding
•Pressure is applied to
the pieces through
dies or rolls.
•The interface is
de-greased, wirebrushed and wiped
to remove oxide
smudges.
Cold Welding
•It is preferred the mating parts be ductile
•A weak and brittle joint occurs when two
dissimilar metals are joined.
•Applications: Wire Stock and Electrical
Connections
Roll Bonding
•A pair of rolls apply pressure to the material to
form a weld.
•Can be applied for both Cold and Hot temps.
•Used to combine two different metals in order
to obtain a metal suitable for different
applications.
Roll Bonding
•Process used in making U.S. quarters, which
is made up of two outer layers of 75%Cu25%Ni(Cupronickel) and a middle section
of pure copper.
Ultrasonic Welding
Ultrasonic Welding
•The two components are subjected to a static
normal force and a oscillating shearing stress.
•The shearing stress is applied at the tip of a
transducer.
Ultrasonic Welding
•The shearing stress breaks
up oxide films and
contaminants to allow
for a strong bond.
•Melting nor fusion take place
•The temperature generated is
in the range of 1/3 to 1/2
of the melting point of the
metals joined
Ultrasonic Welding
•Joining of thermoplastics- Melting does take
place due to the lower melting
temperature of plastics.
•Applications: Bimetallic strips, plastics,
packaging with foils, and lap welding of
sheet, foil, and thin wire.
•Moderate skill is required.
Friction Welding
Friction Welding
•Friction at the interface of the joining
components create enough heat to join
the pieces.
•One work piece is stationary while the other is
rotated at a high constant speed.
Friction Welding
•The two members are brought together by an
axial force.
•Once sufficient contact is established the
rotating member is stopped and axial force is
increased.
Friction Welding
•The pressure at the interface and the resulting
friction produce enough heat for a strong
joint to form.
•The Weld Zone depends on the following:
•Amount of heat generated
•Thermal Conductivity of the materials
•Mechanical properties of the materials at elevated
temperatures.
•The shape of the welded joint depends on the
rotational speed and axial pressure.
Inertia Friction Welding
•The heat is supplied by the KE of a flywheel.
•As friction slows the flywheel, the axial force is
increased.
Inertia Friction Welding
•The weld is complete when the wheel comes
to a stop.
•The timing for this sequence is extremely
important in order to produce a good
quality weld.
Linear Friction Welding
•The interface of the components is subjected
to a linear reciprocating motion.
Linear Friction Welding
•This process is capable of welding square or
rectangular components as well as round
parts made out of metal and plastics.
Linear Friction Welding
•One part is moved across the face of the other
part using a balanced reciprocating
mechanism.
Friction Stir Welding
•A third body is rubbed against the surfaces to
be joined.
•A rotating non-consumable probe is plunged
into the joint.
Friction Stir Welding
•The contact pressures cause frictional
heating, raising the temperature to 230o to
260oC
•The probe at the tip of the tool forces heating
and mixing of the material at the joint.
Friction Stir Welding
•Successful applications have
been used for Aluminum,
Copper, Steel and Titanium.
•Developments may be made in
uses for polymers and composite
materials.
•Used in the fields of aerospace,
automotive, shipbuilding, and
military.
Friction Stir Welding
•Advantages:
•High Quality
•Minimal pores
•Uniform material structure
•Low distortion
•Little microstructural changes
•No shielding gases
•No surface cleaning required
•Thickness of weld in a single pass ranges from
1mm to 50mm
Explosion Welding
•An explosive is used to provide the pressure
to join the components together.
•The explosive is attached to the flyer plate
which strikes the mating component to
produce a wavy interface.
Explosion Welding
•The impact mechanically interlocks the two
surfaces, which causes pressure welding by
plastic deformation.
•The bond strength is very high.
Explosion Welding
•The explosive may be a flexible plastic sheet
or cord or in a granulated or liquid form
which is cast or pressed over the flyer
plate.
• Plates can be as large as 6m X 2m.
•Pipes can also be joined to the holes of
header plates by placing the explosive
inside the tube, and when detonated the
pipe expands joining the pieces together.
Diffusion Bonding
•Achieved by movement of atoms across the
interface (diffusion).
•Temperatures are usually half of the absolute
melting temperature.
Diffusion Bonding
•The bond interface usually has the same
physical and mechanical properties as the
base metal.
•The strength depends on the pressure,
temperature, time of contact and cleanliness.
•Electroplating the surface or applying a filler
metal will increase the strength of the
bond.
•The parts are usually heated in a furnace or
by electrical resistance.
Diffusion Bonding
•Method used by blacksmiths when the made
filled gold (gold over copper)
•Used for reactive metals and composite
materials such as metal-matrix composites.
•Generally used for complex parts in low
quantities, but is now automated for
moderate-volume production.
•Equipment cost is in the range of $3 to $6 per
mm2
Diffusion Bonding/
Super plastic Forming
•
•
Combines diffusion bonding with super
plastic forming to fabricate sheet-metal
structures.
The Process:
1. The sheet metal is diffusion bonded
2. Formed into a die with stop-offs
3. The stop-off regions are expanded in a mold by air.
•
These structures have high stiffness to
weight ratio
Diffusion Bonding/
Super plastic Forming
Diffusion Bonding/
Super plastic Forming
•Useful in aerospace and aircraft applications
•First developed in the 1970s, currently more
advanced for titanium structure
•Ti-6Al-4V and 7475-T6 are commonly used for
the titanium structures.
•Various other alloys are used for aerospace
applications.
Economics of Welding
Operations
•Costs in welding and joining processes
depend on such factors as:
•Equipment Capacity
•Level of automation
•Labor skill required
•Weld quality
•Production Rate
•Preparation Required
Economics of Welding
Operations
•Welding and Joining Costs:
–High- brazing and fasteners
•They require hole-making operations and fastener cost
–Intermediate- arc welding, riveting, adhesive
bonding
–Low- resistance welding, seaming, and crimping
•They are simple to perform and automate
Economics of Welding
Operations
•Equipment Costs for Welding:
–High- ($100,000-$200,000) Electron-Beam and
Laser-Beam Welding
–Intermediate- ($5,000-$50,000) Spot, Submerged
Arc, Gas Metal-Arc, Gas Tungsten Arc, FluxCored Arc, Electro-gas, Electro-slag, Plasma
Arc, and Ultrasonic Welding
–Low- ($1,000+) Shielded Metal-Arc and OxyfuelGas Welding
Economics of Welding
Operations
•Labor Costs are usually higher in welding
compared to other metalworking
operations due to operation skill, welding
time and preparation required.
•In robotic controlled welding the welding time
is 80% of the overall time; whereas in
manual welding only 30% of the overall
time is spent welding.
Economics of Welding
Operations
•Labor Costs–High to Intermediate- Oxyfuel-Gas Welding and
Shielded Metal-Arc Welding
–High to Low- Electron-Beam and Laser-Beam
Welding and Flux-Cored Arc Welding
–Intermediate to Low- Submerged Arc Welding
31.5 Resistive Welding
Definition: Resistance welding covers a number of
processes in which the heat necessary is produced
by electrical current being passed through the
materials being welded.
Spot Welding
Two metals sheets are clamped together and current
is sent through the metal sheets.
Typically spot welds are characterized by a small
round discoloration and depression.
Spot Welding
This is called the weld nugget.
They are used extensively
in industry especially
automotive manufacture.
Spot Welding
Testing Spot Welds
4 types of spot weld tests.
Tension test: most common because it is cheap and
easy
Cross-Tension test:
Twist test:
Both are good at finding flaws,
cracks and porosity in the weld
area
Peel test: Commonly used for thin sheets.
Testing Spot Welds
Seam Welding
Resistance Seam Welding (RSW) uses two wheels
instead of two electrode probes to create a long
single weld.
The two sheets of metal
are passed through the
wheels while electrical
current is applied.
Seam Welding
High- Frequency
Resistance Welding
This is similar to seam welding except high electrical
frequency (up to 450 KHz) is used.
Typically it is used to create butt welded tubing.
Projection Welding
Resistance Projection Welding (RPW)
One of the metal sheets have one or more projections
embossed into it and causes weld nuggets to form at
those points.
After enough heat is created then the sheets are
pressed together.
Projection Welding
Flash welding
Flash Welding (FW)
This is sometimes referred to as flash butt welding
Heat is generated from the arc as the two pieces
make contact.
When sufficient heat is created the ends of the two
pieces of metal are pressed together.
Stud Welding
Stud Welding (SW)
A small part, typically a threaded rod, hanger or
handle acts as one of the electrodes.
The metal sheet acts as the other electrode and after
enough heat is generate the stud is pressed until a
sufficient weld is created.
Percussion Welding
Percussion Welding uses a capacitor to provide
electrical current instead of a transformer.
The advantage is that localized heat is created
making this type of welding ideal for parts that are
next to heat sensitive areas such as electronic
assemblies.
References
Manufacturing Engineering and Technology, Fifth edition, Serope
Kalpakjian & Steven R. Schmid.
Picture from web site related to the book & Internet.