TUNGSTEN INERT
GAS (TIG)
Fatkhy Baridwan
International Welding Engineer & International
Welding Technologist
International Welding Engineer & International
Welding Technologist
Power Source and Circuit
Equipment
Torch Configuration
Gas Flow Rate Control
Gas Flow Rate Control
Arc Configuration
Effects of Polarity
Current Characteristic
Arc Characteristic
Arc Characteristic
TIG Welding Process
ACHF or Balanced AC
DCSP
DCRP
Arc Starting and
Operation
With High frequency, the arc starts
without touching the workpiece. Strike on
starting block when the electrode is
thouroughly heated. Re-ignite arc in the
joint. This reduce tungsten inclusions at
start of the weld. Hod at starting point
until weld pool is established. Add filler
metal at leading edge of pool, but to one
side of centerline
Hot arc forms puddle
Same as AC but
immediately. Strike arc on touch electrode to
work within weld width
work
to avoid marking work.
Runout tabs or striking
plates are often desirable.
Use of high frequency to
strike arc is
recommended
Stability
Smooth arcing: no snapping or cracking
sounds (argon)
Stable in helium
Stable (argon)
Arc Characteristic
Arc Characteristic
TIG Welding Process
ACHF or Balanced AC
DCSP
DCRP
Instability: electrode
contamination
Oxides resulting from contact of hot electrode with Same as AC
air of from contact with oxides or metal in weld
pool causes arc instability. Dress or cut off tip or
replace electrode
Same as AC
Electrode too large
May result in unstable arc and excessive bead width. Same as AC
Use smalles electrode that will carry current
Same as AC
Excessive arc length
Result: unstable arc; shorten arc length
Same as AC
Same as AC
Narrow joints
May cause arc to jump from side to side; widen
groove where possible or bring electrode closer to
work piece
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Arc Characteristic
Arc Characteristic
TIG Welding Process
ACHF or Balanced AC
DCSP
DCRP
Arc Length
Maintain short arc (about equal to electrode
diameter, approximately 1/8 in. if arc too
long, root penetration will not be complete,
particularly in fillet welding; possible
undercutting, excessive bead width, and also
poor weld contour may result.
Short, about 1/16 in
Long, about 3/8 to
¼ in
Breaking the arc
Gradually reduce arc length or current to
minimize weld craters. Continue adding filler
at the same time where applicable. Snap
torcjh to horizontal position to break arc.
Same as AC
Same aa AC
Tungsten Electrode Selection
Guide to selecting a tungste electrode based on amperage range
*Figure copied from “Guidelines to Gas Tungsten Arc Welding (GTAW)”
Consumables
• Electrode
• Gas
• Filler Metal
Tungsten Electrode
Electrode Selection
Electrode Tip Shape
Tungsten Tip Preparation
Tungsten Tip Preparation
TIG Shielding Gases
 Argon
 Helium
 Argon/Helium Mixtures
TIG Shielding Gases
Argon
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Good arc starting
Good cleaning action
Good arc stability
Focused arc cone
Lower arc voltages
10-30 CFH flow rates
Helium
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Faster travel speeds
Increased penetration
Difficult arc starting
Less cleaning action
Less low amp stability
Flared arc cone
Higher arc voltages
Higher flow rates (2x)
Higher cost than argon
TIG Shielding Gases
Argon/Helium Mixtures
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Improved travel speeds over pure argon
Improved penetration over pure argon
Cleaning properties closer to pure argon
Improved arc starting over pure helium
Improved arc stability over pure helium
Arc cone shape more focused than pure helium
Arc voltages between pure argon and pure helium
Higher flow rates than pure argon
Costs higher than pure argon
Welding Parameters
*Figure copied from “TIG Handbook”
Welding Parameters
*Figure copied from “TIG Handbook”
Welding Parameters
*Figure copied from “TIG Handbook”
Welding Parameters
*Figure copied from “TIG Handbook”
Welding Parameters
*Figure copied from “TIG Handbook”
Techniques for Basic Weld Joints
Arc Length
 Arc length normally one electrode
diameter, when AC welding with a
balled end electrode
 When DC welding with a pointed
electrode, arc length may be much
less than electrode diameter
30
*Figure copied from “TIG Handbook”
Techniques for Basic Weld Joints
Gas Cup Size
 Inside diameter of gas cup should
be at least three times the tungsten
diameter to provide adequate
shielding gas coverage
 Picture on right shows example of
gas cup size and torch position
1-Workpiece, 2-Work clamp, 3-Torch, 4-Filler rod, 5-Gas cup,
6-Tungsten electrode
*Figure copied from “TIG Handbook”
Techniques for Basic Weld Joints
Electrode Extension
 Refers to distance the tungsten extends out beyond the gas cup
 May vary from flush with the gas cup to no more than the inside diameter
of the gas cup
 Longer the extension, the more likely it may contact something by accident
 General rule would be to start with an extension of one electrode diameter
Techniques for Basic Weld Joints
Arc Starting with High Frequency
 Torch position on left shows recommended
method of starting the arc with high
frequency when the torch is held manually
 By resting gas cup on base metal there is little
danger of touching the electrode to the work
 After arc is initiated, torch can be raised to
proper welding angle
33
*Figure copied from “TIG Handbook”
Techniques for Basic Weld Joints
Manual
Torch
Movement
*Figure copied from “TIG Handbook”
Techniques for Basic Weld Joints
Manual Torch Movement
 Torch and filler rod must be moved progressively and smoothly
so the weld pool, the hot filler rod end, and the solidifying weld
are not exposed to air that will contaminate the weld metal area
or heat affected zone
 When arc is turned off, postflow of shielding gas should shield
the weld pool, electrode, and hot end of the filler rod
Techniques for Basic Weld Joints
Butt Weld and Stringer Bead
 Be sure to center weld pool on
adjoining edges
 When finishing a butt weld, torch
angle may be decreased to aid in
filling the crater
Torch and rod position for welding the butt weld and stringer bead
*Figure copied from “TIG Handbook”
Techniques for Basic Weld Joints
Lap Joint
 Pool is formed so that the edge of the
overlapping piece and the flat surface of
the second piece flow together
 Torch angle is important because the
edge will become molten before the flat
surface
 Enough filler metal must be added to fill
the joint as illustrated on the right
Torch and rod position for welding the lap joint
*Figure copied from “TIG Handbook”
Techniques for Basic Weld Joints
T-Joint
 Edge will heat up and melt sooner
 Torch angle illustrated will direct more heat
onto the flat surface
 Electrode may need to be extended further
beyond the cup in order to hold a short arc
Torch and rod position for welding the T-joint
*Figure copied from “TIG Handbook”
Techniques for Basic Weld Joints
Corner Joint
 Both edges of the adjoining pieces
should be melted and the pool kept
on the joint centerline
 Sufficient filler metal is necessary to
create a convex bead as shown
Torch and rod position for welding the corner joint
*Figure copied from “TIG Handbook”
Typical Problem
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Lack of Fusion
Undercut
Porosity
Weld Graininess
Crater Cracking
Discoloration on Stainless Steel
Sugaring / Curly Root on Stainless Steel
Lack of Fusion or Poor Penetration
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When there is no fusion between the weld metal and base
metal surface
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Common cause :
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Improper fit-up
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Improper feeding the filler a rod
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Too long arc length
Undercut
 Joint is not properly filled in and cause groove
section by consuming part of base material
 Common cause :
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Too high current welding
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Poor welding techniques
Porosity
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When gases trapped in the weld metal or along
the surface
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Common cause :
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Dirty surface workpiece,
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Inadequate gas flow,
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Too fast travel speed
Weld Graininess
 Common cause :
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Too high current
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Dirty workpiece surface
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Wrong type of filler metal
Ideal Aluminum Weld
Grainy Aluminum Weld
Crater Cracking
 Common cause :
 Instantly dropping the weld power
 Removing the filler rod too quickly
 Mitigation and solution :
 Use proper welding technique
 Continue to feed the filler rod
while slowly reducing current at
the end to fill in the crater
Discoloration on Stainless Steel
 Common Cause : Overheating
 Affects a material’s color and degrades its
corrosion resistance and strength
 Nothing can be done for correction
 Prevention:
 Reduce amperage
 Increase travel speed slightly
 Shorten the arc length
 Use pulsed current
Sugaring / Curly Root on Stainless Steel
 Common Cause
 Weld exposed to air
 No / lack coverage of backing gas
Health and Safety Issues
We Will Cover the following
 Electric Shock
 Fumes and gas
 Arc Rays
 Gas
Safety
 Electric shock can kill.
 Always wear dry insulating gloves
 Insulate yourself from work and ground
 Do not touch live electrical parts
 Keep all panels and covers securely in place
 Fumes and gases can be hazardous to your health.
 Keep your head out of the fumes
 Ventilate area, or use breathing device
Safety
 Welding can cause fire or explosion.
 Do not weld near flammable material
 Watch for fire; keep extinguisher nearby
 Do not locate unit over combustible surfaces
 Do not weld on closed containers
 Arc rays can burn eyes and skin; Noise can damage hearing.
 Wear welding helmet with correct shade of filter
 Wear correct eye, ear, and body protection
Safety
Information from ANSI Z 49.1:2005
Safety
 Hot parts can cause injury.
 Allow cooling period before touching welded metal
 Wear protective gloves and clothing
 Magnetic fields from high currents can affect pacemaker
operation.
 Flying metal can injure eyes.
 Welding, chipping, wire brushing, and grinding cause sparks and
flying metal; wear approved safety glasses with side shields
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Safety
 Welding current can damage electronic parts
in vehicles.
 Disconnect both battery cables before welding
on a vehicle
 Place work clamp as close to the weld as
possible
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Advantages
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Welds more metals and metal alloys than any other process
High quality and precision
Pin point control
Aesthetic weld beads
No sparks or spatter
No flux or slag
No smoke or fumes
Disadvantages
 Less economical than consumable electrode processes for sections thicker than
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3/8 inch
Lowest deposition rate of all arc processes
Tungsten inclusions
Higher operator skill Required
Brighter UV rays than other processes
Slower travel speeds than other processes
Equipment costs tend to be higher than other processes