| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a method for producing a projection weld joint which improves the static strength of a joint part, that is, torque peeling strength and indentation peeling strength, and which also presents the occurrence of cracks while securing favorable weldability. <P>SOLUTION: When a projection weld joint is produced by projection-welding a nut 2 having a prescribed component composition, and a high-strength steel sheet 1 having a tensile strength of 750-1,600 MPa, a thickness of 0.8-3.0 mm and a carbon equivalent Ceq of 0.22-0.50%, immediately after executing main energization with pressuring force of electrode EF and energization time Wt, by executing succeeding energization with succeeding energization electric current POC1 and succeeding energization time POt1 and afterwards holding with electrode holding time Ht, the ratio of the area SJ of a joining part A of the nut 2 and the high-strength steel sheet 1 to the area SR of the nominal diameter portion of the nut 2 satisfies the formula ä0.7≤SJ/SR≤1.5}, and each maximum value of Vickers hardness in the joining part A and a heat-affected zone B is controlled not to exceed 550 Hv. <P>COPYRIGHT: (C)2013,JPO&INPIT</p> |
