Spot-welding method for high-strength steel sheets with excellent fatigue strength characteristics of welds

摘要

PROBLEM TO BE SOLVED: To provide a spot welding method for a high strength steel sheet capable of obtaining a high fatigue strength at the welding part. SOLUTION: By using a method of adjusting the electrode pressurizing force in spot welding within a prescribed range in accordance with the electrode tip diameter, using the high strength steel sheet whose tensile strength TS is within a range of 430-1300 MPa as a material to be welded, a method of adjusting the electrode holding time after the spot welding within a prescribed range, and a method using a working inductive transformation type compound tissue steel containing residual austenite in ferrite as the material to be welded, and making use of the volume expansion of the martensite transformation, residual stresses are generated in the welding part to enhance the fatigue strength of a spot welding joint, in the spot welding method for the high strength steel sheet.