1. GTAW (TIG)

2. Definition
Gas Tungsten Arc Welding (GTAW) is an arc welding process that uses a non consumable tungsten electrode to establish the arc and gas from a cylinder to provide shielding. The filler metal is supplied by a manual rod.
Also called Tungsten Inert Gas (TIG) welding. 2

3. Machine Functions Store and provide shielding gas at the correct rate
Provide desired welding current
Variable current control
Store and circulate water through the torch (watered cooled)
Semiautomatic control

4. Machine Nomenclature Torch Power switch AC balance control Mode switch
Digital Amp meter
Output (Amp) control
Cylinder
Flow meter
Roto meter
Flow control valve
Regulator
Post flow timer
Pulse frequency control
Polarity switch
Output connector
Remote pedal
Ground clamp
Remote receptacle
Explain the function(s) of each one of these controls/parts.

5. Torch Nomenclature Cap Collet Torch body Collet body Gas orifice Cup
Electrode
What is the function of each part?
How are GTAW torches cooled?

6. Introduction
How does the GTAW process meet the three requirements of arc welding?
Heat
Shielding
Filler metal
GTAW
Heat = electric arc
Shielding = gas from cylinder
Filler metal = manual rod

7. Hazards Associated with GTAW
Hot metal Harmful rays Fumes High frequency RF Flying objects Loud Noise
What is the best management practices for these hazards?
Hot metal Gloves, pliers
Harmful rays Correct shade of lens, not exposed skin
Fumes Ventilation
High frequency Warning signs
Flying objects Safety glasses
Loud noise Appropriate hearing protection

8. Heat
The heat produced by an electric arc between the nonconsumable tungsten and the metal is sufficient to melt the base metal and the filler rod.
What determines the amount of heat produced by the electric arc?
Amount of current
amperage
For the TIG welding process, is the current adjusted by changing the amperage or the voltage?

9. Heat – Currents Three common currents: DC- DC+ AC--HF
Note: many power supplies have the option of pulsed current for better puddle control.
Non contact starting.
Why is HF (high frequency) used with AC?

10. Heat – Current - Polarity
For the best welds, and ease of welding, the correct current must be used for the metal being welded.

11. Heat - Tungsten
The tungsten electrode is nonconsumable and is used to form the arc between the torch and the metal.
Different alloys of tungsten are available. ID
% Alloy
Color
Characteristic
EWP
100 % Tungsten
Green
Good arc stability with AC
EWTh-2
2 % Thorium
Red
Better Arc with DC
EWZr-1
1 % Zirconium
Brown
AC when high weld quality is required
EWCe-2
2 % Cerium
Orange
Better starting, higher current
2% lanthanum/black
EWLa-2
2 % Lanthanum
Black
50% greater current capacity with AC
Which alloy/color should be used when welding thicker aluminum with AC?

12. Heat – Tungsten - Preparation
The shape of the tungsten electrode end must be appropriate for the current being used. AC
Hemispheric or balled end no more than 1.5 times the electrode diameter. Grinder lines parallel with electrode.
DC-
Needle point for very thin metal, blunt point for thicker metal. Taper = 2 to 2-1/2 times the diameter.
What does it mean if the end of the electrode appears dull?
What does it mean if the end of the electrode is blue or blackened?
Excessive current was used
Insufficient postflow shielding
one second per 10 amps of welding current
How long should the the shielding gas flow after the welding has stopped?

13. Heat – Tungsten - Size Diameter (in) Gas Cup Inside Dia. DC-
(Ce, Th % La) AC
(Pure)
0.040
#5 (3/8 in)
15 – 80
20 – 60
0.060 (1/16 in)
50 – 100
70 – 150
0.093 (3/16 in)
#8 (1/2 in)
150 – 250
140 – 235
0.125 (1/8 in)
250 – 400
150 – 200

14. Shielding How is the flow of the shielding gas controlled?
In the GTAW process shielding is supplied from a cylinder.
How is the flow of the shielding gas controlled?
For best results the shielding gas must be appropriate for the type and thickness of metal.
Flow meter
112 ft3
How much gas (ft3) will each gallon of liquid argon produce?

15. Filler Metal What are three important characteristics of GTAW rods?
A welding rod is used to fill in the joint. Most common type is 36 inch rods that are fed into the weld pool by hand.
What are three important characteristics of GTAW rods?
Material must be compatible with welding metal
Diameter must be appropriate for thickness of metal
Must be clean and free from oxidation

16. AWS GTAW Aluminum Filler Rods
Aluminum Alloy
Filler Rod
1100
ER1100
2014-T6
ER4043
2219-T81
ER2319
3003
ER1100
5005
ER5356

17. Process

18. Preparation for Welding
Three (3) steps in preparing to weld:
Safety check
Metal preparation
Set up machine

19. Preparation - Safety
Check the machine, cables, torch and ground clamp.
Insure the helmet is in good condition and the correct shade of lens.
Cover all exposed skin.

20. Preparation – Metal – Aluminum
Contamination is the biggest problem when welding aluminum with the GTAW process.
The metal must be cleaned with a stainless steel wire brush.
The brush can only be used to clean aluminum.
Must clean the adjoining faces and the back edge
Insure the filler rod is clean also.

21. Preparation - Machine Attach the GTAW torch to the output connector.
Attach the remote control pedal to the remote receptacle.
Position the polarity switch on AC.
Turn on the machine.
Insure the torch is not grounded
Set the mode switch to TIG
Set the amperage.
150 amp maximum for air cooled torch.
Set the AC balance control.
Set the pulse control.
Set the postflow timer.

22. Preparation – Machine - Torch
If the torch has been used to weld carbon steel or stainless steel then the cup and electrode must be replaced.
The tungsten electrode must be clean and the correct shape.
The torch cup must be clean
The electrode must be set with the correct stickout.

23. Welding aluminum

24. Aluminum Amperage ACHF
Setting Amperage
Aluminum is a good conductor of heat. Aluminum melts at a lower temperature that steel.
Aluminum Amperage ACHF
Thickness
Joint
Tungsten electrode diameter
Filler rod diameter
Amperage
Gas
Type
CFH
1/8 in
Butt
3/32 – 1/8 in
3/32 in
Argon 20
Lap
Corner
Fillet
3/16 in
1/8 – 5/32 in
190 – 240
1/4 in
5/32 – 3/16 in 25
250 – 320

25. Troubleshooting GTAW
Troubleshooting is the process of determining the cause of a problem.
Assumes the welder is in proper working order.
Requires gathering information and a logical thought process.

26. Troubleshooting - 1 Problem Cause Excessive electrode consumption
Inadequate gas flow
DCEP electrode
Excessive current density
Tungsten oxidation during cooling
What would you do to remedy these causes?

27. Troubleshooting - 2 Problem Cause Aluminum contamination of electrode
Electrode contacting filler rod
Electrode contacting metal
What would you do to remedy these causes?

28. Troubleshooting - 3 Problem Cause Weld porosity and dark color
Condensation in system
Atmospheric contamination
Contaminated filler metal
What should be done to remedy these causes?
Contaminated base metal

29. Troubleshooting - 4 Problem Cause Yellow powder or smoke on cup
Insufficient gas flow
Atmospheric contamination
Inadequate post flow
What should be done to remedy these causes?
Incorrect shielding gas
Incorrect tungsten size or cup size

30. References