Tungsten Inert Gas Welding(TIG) or Gas Tungsten Arc Welding (GTAW)
A non-consumable tungsten electrode is employed in this technique, which is surrounded by an inert shielding gas.
The tungsten electrode and the molten metal weld pool are shielded from contamination by the shielding gas.
Argon, helium, or their mixes are the most common shielding gases.
Materials used in electrodes
Tungsten or tungsten alloys (thoriated tungsten or zirconiated tungsten) can be used as electrode materials.
The oxides of thorium and zirconium assist the electrodes keep their shape at the tip for longer periods of time, making electron emission easier.
In comparison to pure tungsten electrodes, alloy-tungsten electrodes have a larger current carrying capacity, create a more stable arc, and are more resistant to contamination.
Sizes range from 0.5 to 10 mm.
Tungsten has a relatively low wear rate due to its high melting point (3410 C).
Source of electric power
TIG welding can be done using both AC and DC power sources.
Cast iron, copper, copper alloys, nickel and stainless steel, and titanium are best welded with DC (straight polarity).
Aluminium, magnesium, and their alloys are welded using DC reverse polarity (DCRP) or AC. DCRP enhances weld quality by removing oxide coating from magnesium and aluminium.
Welding voltage ranges from 20 to 40 volts, with weld current ranging from 100 to 500 amperes.
Gases that are inert
- Argon is the first element.
- The element helium
- Mixtures of argon and helium
- Hydrogen-argon mixtures.
Nozzle Tig
The size of the nozzle or shield (the opening of the shroud around the electrode) to be used is determined by the geometry of the groove to be welded and the desired gas flow rate.
The gas flow rate is determined by the position and size of the weld.
A high gas consumption will cause turbulence in the weld metal pool, resulting in porous welds.
Inert gas shielded arc welding does not require the use of fluxes due to the use of shielding gases.
However, for thicker portions, it may be necessary to provide a flux to protect the root side of the joint.
Advantages
- The costs of operation are modest.
- Weld quality is excellent.
- Because the filler metal is not transmitted over the arc gap, there is no spatter (unwanted microscopic droplets of weld metal). As a result, no post-welding grinding or polishing is required. When welding in difficult-to-reach areas, this is a critical characteristic.
- Because the welds created are so clean, there is no need for a separate cleaning operation.
- Welding can be done on a range of metals (both ferrous and non-ferrous), particularly aluminium, magnesium, titanium, and refractory metals. The method is especially well suited to welding high alloyed metals when weld quality is critical.
Limtations
- The tungsten electrode must not come into contact with the work metal because tungsten may be deposited.
- This technique has a hard time welding cast iron, wrought iron, and lead.
- Steel welding is a slower and more expensive method than consumable electrode arc welding.
Application
- Rather than welding bigger workpieces, the method is best suited for high-quality welding of thinner workpieces.
- Aluminium, magnesium, and stainless steel are commonly welded using this method.
