METHOD FOR IMPROVING FATIGUE STRENGTH IN SPOT WELD ZONE OF HIGH TENSION STEEL SHEET

摘要

PROBLEM TO BE SOLVED: To increase the fatigue strength of a spot weld zone by decreasing the residual tensile stress of the surroundings of the weld zone. SOLUTION: Steel sheets 1 are subjected to spot welding under a pressure by electrodes 2, and by temporary energizing to the electrodes 2 after spot welding, the spot weld zone is made to generate heat to temper it, and the residual tensile stress of the surroundings of the spot weld zone is decreased by the increase of a pressure force by the electrodes 2.