**TIG Welding or Gas tungsten arc welding (GTAW) **is a process in which the joining of metals is produced by heating with an arc between a tungsten (non-consumable) electrode and the work. A shielding gas is used, normally argon. TIG welding is normally done with a pure tungsten or tungsten alloy rod, but multiple electrodes are sometimes used. The heated weld zone, molten metal, and tungsten electrode are shielded from the atmosphere by a covering of inert gas fed through the electrode holder. Filler metal may or may not be added. A weld is made by applying the arc so that the touching work piece and filler metal are melted and joined as the weld metal solidifies. This process is similar to other arc welding processes in that the heat is generated by an arc between a non-consumable electrode and the work piece, but the equipment and electrode type distinguish TIG welding from other arc welding processes.
TIG welding is most commonly used to weld thin sections of stainless steel and non-ferrous metals such as aluminum, magnesium, and copper alloys. TIG welding enable much greater control over the weld than competing processes such as shielded metal arc welding and gas metal arc welding, allowing for stronger, higher quality welds.
When TIG welding a short arc length is maintained while preventing contact between the electrode and the work piece. TIG welding normally requires two hands, because most applications require that filler metal be manually fed into the weld pool with one hand while manipulating the TIG welding torch in the other.
TIG Welding Shielding Gas
As with other welding processes such as gas metal arc (GMAW) welding or Metal Inert Gas (MIG) welding, shielding gases are necessary in TIG welding in order to protect the welding area from atmospheric gases such as nitrogen and oxygen, which can cause fusion defects, porosity, and weld metal embrittlement, if they come in contact with the electrode, the arc, or the welding metal. The shielding gas also transfers heat from the tungsten electrode to the metal, and it helps start and maintain a stable arc.
The selection of a TIG welding shielding gas depends on several factors, including the type of material being welded, joint design, and desired final weld appearance. Argon is the most commonly used shielding gas for TIG welding, because it helps prevent defects due to a varying arc length, a smoother and quieter arc, and easier arc initiation. Another common shielding gas, helium, is most often used to increase the weld penetration in a joint, to increase the welding speed, and to weld metals with high heat conductivity, such as copper and aluminum.