RESISTANCE WELDING METHOD FOR BAR STEEL

PROBLEM TO BE SOLVED: To provide a resistance welding method for bar steel by which a welded part of bar steel having excellent hardness and toughness can be formed without shifting the welded part to a quenched state and without requiring any tempering process. SOLUTION: The resistance welding method for bar steel incldues a welding step of applying the welding current of the predetermined value to the welded part of bar steel to be welded, and a gradually cooling step of gradually cooling the welded part by performing heat input control on the welded part so that the welded part in a rapidly heated state is not rapidly cooled into a quenched state. The welded part of bar steel in the rapidly heated state is gradually cooled by performing the heat input control while not waiting for any structural change in the welded part of bar steel caused by the rapid cooling for quenching after the welding step. It is confirmed that the desired strength and toughness of the obtained welded part are ensured by gradually cooling the welded part of bar steel in a rapidly heated state by the heat input control. Any control for rapid cooling (quenching) and for tempering becomes unnecessary, and the production control is facilitated. Since the tempering time becomes unnecessary, the productivity of the resistance welding work of bar steel is also enhanced. COPYRIGHT: (C)2009,JPO&INPIT