TIG welding (Tungsten Inert Gas, GTAW in American terminology, process 141 of ISO 4063) is an arc welding process in which the electric arc strikes between a refractory tungsten electrode, which does not melt, and the workpiece. The weld pool is shielded from the air by an inert gas, usually argon, sometimes mixed with helium. Filler metal, where needed, is added separately as a rod.
The welder sets the current, often with a foot pedal, and guides the torch with one hand while the other feeds the filler. Steel, stainless steel, copper and titanium are welded with direct current. For aluminium, alternating current is essential: it breaks up the alumina layer, which melts at a much higher temperature than the metal. The torch is air- or water-cooled. The process also exists in an automated version, notably for orbital welding of tubes. It is slow but highly controllable: the weld is clean, spatter-free and neat in appearance, with great weld integrity.
TIG is particularly suited to thin sections, visible parts and leak-tight or high-specification welds: sanitary and food-industry pipework in stainless steel, pharmaceutical, aerospace, parts in aluminium alloy or titanium, root passes on pipework. It is less productive and costlier per metre than MIG-MAG welding, which is preferred for medium thicknesses and long runs. The guide TIG, MIG and MAG welding compares them, and the welding and plate fabrication page describes the capability.
In a quote request. State the material and grade, the thicknesses, the joint type (butt, fillet, lap) and the length of welds. Specify the level of requirement: ISO 5817 quality level (B, C or D) for steel and stainless steel, inspections to be carried out (visual, dye penetrant, radiography), welder qualification and finishing (pickling, passivation, polishing).