Gas tungsten arc welding (GTAW) is commonly known as tungsten inert gas
welding (TIG), however since some
process variations utilize active (other than inert) shielding gases, the
correct technical term is GTAW.
In this process a non-consumable tungsten electrode is used and the electric
arc occurs between this electrode and the work. Filler
usage is optional; a weld when no external filler metal is used it is known as
an autogenous weld. The molten weld and the arc zone are protected from
atmospheric contamination by a shielding gas (usually, but not always, an inert
gas such as argon). A constant current welding power supply produces energy
which is conducted across the arc through a column of highly ionized gas and
metal vapours known as a plasma.