The Resistance welding also called spot welding or by its also known RW nomenclature, refers to a set of welding processes that use pressure and heat, and they use the current flow to heat the material to its plastic state, The main characteristic is that the resistance welding process creates "coalescence or fusion" without the use of any component such as cast iron or material applied to it.

To have a basic understanding of Resistance welding (projection welding), you need to know from the beginning, can be attributed to the discovery in 1864, to the english physicist James Prescott Joule which made the electric current flow through a copper filament, and I create a certain amount of resistance, which eventually generates heating, that generated so much heat to solder a copper coil and it will stay attached to carbon.

Resistance spot welding refers to a method of using electric current through the weldment and the resistance heat generated at the contact as a heat source to locally heat the weldment, and at the same time pressurize the flash welding method. When electric resistance welding, no filler metal is required, the productivity is high, the deformation of the weldment is small, and it is easy to realize automation. 

Resistance seam weldingis a method of using electric current flowing through the contact surface and adjacent areas of the workpiece to heat it to a molten or plastic state to form a metal bond. There are four main methods of resistance projection welding, namely spot welding, seam welding, projection welding and butt welding.