Flash Butt Welding
This process is an extension of resistance butt welding. The parts to be joined are gripped in the clamps and their interfaces are gradually brought into contact to complete the secondary circuit. When the welding voltage of up to about 10 volt is applied at the clamps, current flows through the initial points of contact causing them to melt. The platen on which the movable clamp is mounted is moving forward, fresh contacts are made and then there is a continuous flashing of sparks. Flashing is allowed to continue until the surfaces to be joined are uniformly heated or molten. At that point extra pressure is applied to the moving platen so that the tubes are forged together and the molten metal is expelled and weld joint is achieved. The process is used for joining of boiler economiser tubes, rails, hanger rods, etc. The process was also employed for welding of cross - country pipelines in Russia.