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The increased usage of high-strength, cold-rolled steels has revealed differences in spot welding characteristics between the thin, high strength steels and the plain carbon steels commonly used in the automotive industries. The response of four, 275 MPa yield strength, cold-rolled steels to a variety of spot welding schedules was determined through an evaluation of mechanical property and fracture appearance tests. The results of this study were compared to various weld quality evaluation criteria and suggestions for a revised criteria were proposed.

Mechanical properties and welding characteristics of a commercial, dual-phase, low-carbon, cold-rolled steel are described. The new steel, HI-FORM 80d, exhibits a total elongation of about 24% as produced and develops a yield strength of about 625 MPa (91 ksi) in a formed and paint-baked part. Property uniformity is excellent and the weldability essentially equivalent to an AISI 1006 steel. In addition, the aging response of HI-FORM 80d is such that yield strengths near 550 MPa (80 ksi) can be achieved with strains of less than 2% and lower paint-bake temperatures than are currently in use.