TIG (GTAW)

During TIG welding the supplied inert gas protects the electrode, the light arc and the weld pool from the atmosphere. Usually argon or an argon-helium mix is used as a shielding gas. Depending on the material, additives are also added by hand or supplied mechanically with a special cold wire supply unit; these are melted in the light arc before the weld pool. Stainless steel is often welded without the addition of additives; the material is connected by means of fusion. This process uses a highly intensive light arc that can be guided extremely stably. Experienced TIG welders find this procedure very easy to handle and, if a mechanical wire supply unit is used, it is highly convenient and in some cases develops highly unhealthy fumes, the danger which is usually not recognized because they are not visible. It is suitable for creating high-quality welds. The process is practically spatter-free and almost no scaling is created on the material. TIG welding is suitable for manual, mechanized and automated processes, and is often used in constrained working positions.

TIG welding is highly suited for welding austenitic CrNi steels because, thanks to its favourable viscosity, the upper beads are very smooth and the lower sides of the roots are flat. Steel, copper, titanium and nickel are usually TIG welded using DC current with a negative electrode. In contrast, aluminium, magnesium and their alloys are TIG welded under AC current. In particular this tears the oxide skin that forms on the surface of the aluminium that is a prerequisite for permanently stable welds.