Welding is an inevitable part of the sheet metal machining, and the quality of welding has crucial impact on durability and safety of the sheet metal products. There are many common welding methods used during the process of sheet metal machining and production, all of which are classified by the characteristics of the welding process. In normal conditions, CO2 protection welding, argon arc welding, aluminum welding (T.I.G. welding), and resistance welding are used.