Three welding processes

　　Three types of welding processes:

　　Electric Resistance Welding: During ERW, a high frequency electrical current is transmitted to the material by means of copper sliding contacts so that the abutting edges initiate fusion as they come into contact.

　　Longitudinal Submerged Arc Welding: In LSAW, the butt joint of the pipe is welded in at least two phases, one of which is on the inside of the pipe. The welds are made by heating with an electrode arc between the bare metal electrodes. Pressure is not used. Filler metal for the welds is obtained from the electrodes.

　　Spiral Submerged Arc Welding: Spiral SAW allows large diameter pipes to be produced from narrower plates or skelps. During this process, the weld pool is protected against oxidation by a flux produced from the electrode fed separately onto the weld.