When two(2) wires which are charged with electricity, are made to contact with each other, they crackled with sparks.
The flash-butt welding is a welding method which harnesses this heat of which sparks generate, to melt and to weld metals.
The potential between two(2) poles of transformer is 12 volts and the current is about 1,000 amperes. The touched faces which should be welded, are melted in a moment with this electricty which has higher current with lower voltage. The touched faces are touched and untouched untill all parts of touched faces should be melted uniformly. Then welded parts are pressed and a pressure welding should be done with large pressure (12 kg/mm2).