Arc-welding processes include a multitude of variations including MIG (GMAW) welding, TIG (GTAW) welding, Flux-cored (FCAW) welding, Submerged Arc Welding (SAW), Shielded Metal Arc Welding (SMAW), and Micro-Plasma Arc Welding. As the name suggests, arc-welding processes use an electric arc formed under controlled conditions to generate heat. Arc welding processes typically produce a fusion weld where the parts being welded are partially consumed in the weld metal. Sometimes, filler metal wire is used to add material to the weld to make the weld metal of a desired chemistry.
Even though there are differences between the many arc welding processes, there are many similarities as well. In most arc-welding processes (except non-transferred plasma), the arc is drawn between the electrode and the parts to be welded and hence the parts have to be conductive. The arc creates intense heat that has the power to melt metals and alloys. Electricity is conducted through the arc by the conductive plasma that constitutes the arc. The arc can be initiated by contact with the part or by use of a high voltage pulse that acts like a starter flame. If the melt pool is exposed to the atmosphere, it will pick up oxygen, nitrogen, water vapor (Hydrogen), which can be detrimental. Pickup of contamination is avoided, or at least significantly reduced, by providing a shielding gas or molten slag (SAW). In addition to shielding, the gas is also selected to produce to stable arc for that particular application.