DC is generally used to weld exotic material like stainless steel, nickel alloys, copper, titanium and critical welds that must be flawless such as aircraft engine parts. The primary gas used is argon and in some applications an argon/helium mixture or pure helium is used. TIG welding offers the user the greatest amount of flexibility to weld the widest range of material and thickness and types. DC TIG welding is also the cleanest weld with no sparks or spatter.
TIG welding methods are classified according to the welding current to DC TIG and AC TIG for direct current and alternating current, respectively. TIG welding power sources are suitable for both current types (AC/DC) or for only DC welding.
AC/DC must be used in aluminium welding.
If current mixed of both direct and alternating current is used in TIG welding, the method is called MIX TIG welding. It is a particularly useful method when welding aluminium materials of different thicknesses together.
In Pulse TIG welding, the power source pulses the welding current, which reduces the heat effect affecting the material being welded. This is useful particularly when welding thin materials in which the TIG heat input is great. Pulse welding also improves the manageability of the molten weld pool and the penetration.