The document discusses gas tungsten arc welding (GTAW), also known as tungsten inert gas (TIG) welding. It describes the principle of using an arc between a tungsten electrode and the base metal to melt and join materials. Inert shielding gases like argon are used to protect the weld area. GTAW can be used to weld materials like aluminum, stainless steel, and mild steel. It is well-suited for thin materials and high quality welds but has lower deposition rates than other welding processes. Electrode selection, filler metals, power supplies, safety procedures, and other aspects of the GTAW process are also outlined.

1. GAS TUNGSTEN ARC
WELDING
Prepared By
Parth Dasadiya
14BME133D
12/16/2017 1

2. Content
 Introduction
 Principle of Operation
 Application
 Limitation
 Arc Polarity
 Rectification and cleaning Action with Alternating Current
 Power Supplies
 Electrode selection
 Shielding gas
 Filer metals for GTAW
 GTAW Welding Procedures
 Safety
12/16/2017 2

3. Introduction
• Gas tungsten arc welding process was developed in 1930 when need
to weld magnesium.
• GTAW process is also known as TIG process
• Weld pool temperature can approach 25000C
• TIG is use to weld mild steel, aluminum
and stainless steel
12/16/2017 3

4. • Arc is established between the end of tungsten electrode and the
parent metal at the joint line
• Inert Gas use Argon, helium and Mixture
• Argon use because Low cost, Smooth Operation and Greater
Density
Principle of Operation
12/16/2017 4

5. Applications
Aerospace Industries uses lite metals (aluminum and its alloy) thin
sheet and need high quality welding so TIG is more suitable for it
Fuel pipe A320 airbus
12/16/2017 5

6. Application
TIG in Bicycle Industry
In bicycle industry TIG is Frequently employed to weld small-diameter and
thin-wall tubing welding
12/16/2017 6

7. Application
well suited for welding thin sheet and foil of all weldable metals
because it can control very low amperages (2 to 5 A) require for
thin thickness
Tube and pipe assembly
12/16/2017 7

8. Limitation
Lower deposition rates than consumable electrode arc welding
processes
Less economical than consumable electrode arc welding for thick
sections greater than 9.5 mm (0.38 in.)
In steel Welding operation, TIG is slower and the most costly one
Lower melting point material we can not weld by this method
12/16/2017 8

9. Arc Polarity
• The GTAW process can be operated in three different modes:
electrode negative (straight polarity)
electrode positive (reverse polarity),
or alternating current
12/16/2017 9

10. 12/16/2017 10

11. Rectification and Cleaning Action with
Alternating Current
Maximum Cleaning is desired, Electrode positive is favoured.
Maximum heat is desired, Electrode negative is favored.12/16/2017 11

12. Power Supplies
12/16/2017 12

13. Electrode selection
Depends on…
• Material weld
• Electrode material
• Size
• Tip angle (30 to 1200
) smaller is (5 to 300
)
• Electrode holder
• nozzle
12/16/2017 13

14. Shielding gas
• The original GTAW process used helium as the shielding gas for
welding magnesium and aluminum. Today argon is the predominant
shielding gas.
• Mixtures of the two are sometimes used for specific situations.
Argon is the least expensive of the inert gases used for shielding
• Argon has a low ionization potential (2.52 ∗ 10−18
J, or 15.7eV)
• Argon is approximately 1.4 times heavier than air, so it displaces air,
resulting in excellent shielding of the molten weld pool.
12/16/2017 14

15. Shielding gas
Helium has an ionization potential of 3.92 ∗ 10−18J (24.5 eV)
• which results in more difficult arc initiation and requires operation
at a higher arc voltage and hence higher heat input for a given
current.
• This higher heat input can be very beneficial when welding copper,
aluminum, and other high-conductivity materials.
• Helium shielding used with direct current electrode negative is very
effective for welding thick aluminum.
12/16/2017 15

16. Shielding gas
Gas Purity Most materials can be welded using a welding-grade torch
gas with a purity of 99.995% or 50 ppm impurities.
• some reactive materials (for example, titanium, molybdenum, and
tantalum) require that the contaminant level be less than 50 ppm.
• This may require certified gas purity or the use of gas filters and
purifiers.
12/16/2017 16

17. Filer metals for GTAW
• When we want to weld high thickness then need to add filler metal
• Properly designed and prepared, lap welds, butt welds, and edge
welds on material thinner than 2 mm may be autogenously welded
without filler-metal additions.
• Autogenous welding of aluminum and magnesium is not generally
recommended because there is a possibility of cracking, especially
crater cracking.
• The filler metal normally cold added. may also be added by hot wire
addition with automatic applications
12/16/2017 17

18. Filler metal selection
12/16/2017 18

19. GTAW Welding Procedures
• Type and thickness of material
• Service requirement
• Joint design
• Position in which weld will be made
• Cleanliness of material to be welded
• Filler metal required if the weld is not
• autogenous
• Filler-metal diameter
• Tungsten type and diameter
• End shape of tungsten and end diameter
• Current type and amperes
• Arc voltage
• Composition of shielding gas
• Gas cup diameter
• Shielding gas flow rate12/16/2017 19

20. Safety when using GTAW
• There are three basic safety documents, and all personnel, welders,
and supervisors alike should understand and be familiar with the
safe practices discussed in these documents. These documents are
• “Safety in Welding and Cutting,” ANSIZ49.1 (Ref 8)
• “Fire Prevention in the Use of Welding and Cutting Processes,”
ANSI Z49.2 (Ref 8)
• “Safe Handling of Compressed Gases in Containers,” 11th ed.,
Compressed Gas Association (CGA) P-1 (Ref 9)
12/16/2017 20

21. Possible Hazards
• Electrical shock
• Fumes and gases
• Arc radiation
• Fire and explosion
12/16/2017 21

22. Referances
• ASM handbook volume06A
• wikipedia.org/wiki/Gas_tungsten_arc_welding
12/16/2017 22

23. 12/16/2017 23