Gas metal arc welding (GMAW) is a fusion welding process, which uses an electrical arc as the source of energy that causes the metal fusion to occur. The electrode used in gas metal arc welding is also the filler metal consumable. An external shielding gas is used to protect the molten weld puddle.
Gas metal arc welding uses a continuously fed metal wire to serve as both the filler material and the electrode. It is similar to shielded metal arc welding in that the electrode is also the filler metal, but gas metal arc welding differs from shielded metal arc welding because the electrode is continuously fed. When the metal wire comes into contact with the work piece, an electrical arc is initiated. This electrical arc causes the wire and the base material to melt. The melted wire is then transferred across the arc and into the molten base material. To prevent atmospheric contamination of the weld pool, an external shielding gas is dispersed around the weld while in its molten state.
A wide variety of materials can be welded with gas metal arc welding, with carbon steel perhaps the most popular. Other materials include, but are not limited to, aluminum, stainless steel, titanium and tool steel. Special wire feeding and shielding gas equipment may be required to weld some of these materials.
Gas metal arc welding has several advantages over other fusion welding processes. In general, faster travel speeds are possible with gas metal arc welding when compared with gas tungsten arc welding or shielded metal arc welding. Furthermore, gas metal arc welding does not leave a slag on top of the solidified weld, unlike shielded metal arc welding or flux-cored arc welding. For less critical applications, gas metal arc welding also requires less operator skill than most other welding processes. Gas metal arc welding is very automation-friendly.