The process of resistance welding involves
- developing electrical resistance in the parts of the joint to bring them into a plastic state and
- applying pressure on the parts to make the joint
Two copper electrodes are connected to an electric circuit of low resistance. The parts to be welded are placed between the electrodes. When current is allowed to pass through the electrodes, high electrical resistance is developed at the joint. Because of the resistance, heat is generated at the joint. The metal parts reach plastic state at this high temperature.
At this point, pressure is applied by means of either mechanical or hydrulic or pneumatic power source to make the joint. Current is provided by a suitable A.C. transformer. Resistance welding is useful in welding sheet metal, bars and pipes.