SPOT WELDING METHOD.

摘要

Provided is a spot welding method in which variation in a reduction in hardness that is caused by tempering is minimized and high delayed fracture resistance characteristics are stably obtained by: using two-step conduction to perform spot welding of a high-strength steel plate that comprises 0.15 mass% or more of carbon and that has a tensile strength of 980 MPa or more; setting the ratio (I2/I1) of the current (I1) of the first conduction step and the current (I2) of the second conduction step to 0.5-0.8; setting the time (tc) of a cooling step to be within a range of 0.8×tmin to 2.5×tmin, said range being calculated in accordance with the thickness (H) of the steel plate using a formula (0.2×H2); setting the conduction time (t2) of the second conduction step to be within a range of 0.7×tmin to 2.5×tmin; and welding from the cooling step onward using an applied pressure that is greater than the applied pressure that is used until the first conduction step.