| 摘要 |
Electric resistance heating easily occurs in a contact side by heating a welding side in advance before applying a large amount of electric current to the welding side to promote the electric resistance heating of the contact side for melting the contact side by supplying a large amount of current to a part of a metal plate in contact with when two metal plates, which are overlapped, are spot-welded. For achieving the above purpose, a spot welding electrode tip which is made of the existing copper material is changed as a form of a cylindrical welding electrode tip, and an auxiliary heating electrode which is a cylindrical form surrounds a cylindrical welding electrode tip by using a tungsten-based ferrous iron metallic material with the high electrical resistance value in the circumference. Moreover, the cylindrical auxiliary heating electrode is protruding little more than the cylindrical welding electrode tip while being supported by a spring. A welding plate is instantaneously heated by applying electric current since the cylindrical auxiliary heating electrode is in contact with the welding plate in advance before the cylindrical welding electrode tip is in contact with the welding plate. Spot welding is completed by forming a cylindrical nugget in a contact side of a welding metal by continuously applying a large amount of electric current, which is caused by a cylindrical welding electrode tip which is in contact with the welding metal plate, to a welding metal plate. |
