There are two types of DC welding machines: One is the installation of rectifying originals on the basis of AC motors, and the other is DC generators. DC welding machines mainly weld non-ferrous metals and pig iron. AC welding machine is mainly welded steel plate. Argon arc welding machine, carbon dioxide protection welding machine, high frequency welding machine, flash butt welding machine. The argon arc welding machine and the carbon dioxide protection welding machine can mainly weld thin sheets and colored gold layers below 2 mm. Flash butt welding machine mainly butt joints and other objects such as copper and aluminum, high frequency at the main welding plant welded pipe.