Tungsten Inert Gas welding (TIG), formally known as ‘heliarc welding’, was developed to weld non-ferrous metals like magnesium. The American Welding Society (AWS) refers to it as Gas Tungsten Arc Welding (GTAW). Magnesium has found its way into all types of racing in the form of wheels, engine blocks, transmission cases and many other components because of its strength and light weight properties. Magnesium is considered a flammable metal, so there has to be a highly controlled process in order to weld it. This is after all, the same metal found in the Space Shuttle’s solid rocket boosters. A powder form of it was used in the paint on the Hindenburg, which ultimately accelerated its catastrophic demise in a massive fireball.
The Constant Current (CC) type of welding machine became the standard form of power supply for TIG, and was already in use for stick welding, also known as Shielded Metal Arc Welding (SMAW) by the AWS, the simplest form of welding. Gas Metal Arc Welding (GMAW), sometimes referred to by its sub-types, Metal Inert Gas (MIG) welding and Metal Active Gas (MAG) welding, uses Constant Voltage (CV). With a CC machine, the current stays constant, usually between 60 and 80 volts, whereas with MIG welding, the current changes with wire speed. High quality welding machines gave us the ability to control the sine waves of electricity coming out of our machines in order to make extremely beautiful welds. New advances in TIG welding processes have given rise to ‘Pulse TIG’ where there is a background current and a peek current. The frequency of the pulse is controllable in order to aid in those perfect “dime stack” welds that are so desirable in appearance.
The TIG process also allows for an ‘autogenous weld’ (where no filler metal is needed). This can never be done with an MIG process because the electrode is consumable and is used as the filler metal. These are some of the reasons that the controllable aspect of TIG welding makes it very desirable for many applications. Unfortunately, it takes a very high level of skill to make TIG quality welds because TIG welding typically has a slower disposition rate than that of the MIG process. MIG welding excels in high disposition rates and less skill is required to master the process.