PREDICTION METHOD OF CROSS TENSILE STRENGTH IN SPOT WELDING OF QUENCHED STEEL PLATE, AND SPOT WELDING METHOD USING THE SAME

摘要

PROBLEM TO BE SOLVED: To allow a cross tensile strength CTS to exceed a set value by evaluating the influence on the CTS of a softened part generated in a heat-affected zone in spot welding of a quenched steel plate, and by predicting the CTS from welding conditions.;SOLUTION: (A) Before the main welding, (a1) the quenched steel plate is spot-welded with various energization conditions, and the softening amount ΔHv of the softened part and the CTS of a welded joint are measured, (a2) a temperature history of the welding heat-affected zone is calculated, and a tempering parameter λ is calculated from the temperature history to find the relation between the tempering parameter λ and the softening amount ΔHv, (a3) the softening degree N is calculated from the softening amount ΔHv to find the relation between the CTS and the softening degree N. (B) During the main welding, (b1) the tempering parameter λ is calculated from the energization conditions of the set main welding, (b2) the softening amount ΔHv is found from the tempering parameter λ, (b3) the softening degree N is found from the softening amount ΔHv, and (b4) the CTS of the spot-welded joint is found when welding is performed with the energization conditions set from the softening degree N.;COPYRIGHT: (C)2013,JPO&INPIT