Resistance spot welding of steel and aluminium sheet using insert metal sheet

The present paper reports the resistance spot welding of steel and aluminiu m sheets using aluminium clad steel sheets as insert metals. Intermetallic compound layers were formed in the weld zones in direct spot welding of ste el sheets to aluminium sheets. Thus, the strength of these joints rc as low er than that of aluminium to aluminium joints. Intermetallic compound layer s were also formed at the steel/aluminium interfaces of the insert metal in welding of steel to aluminium using an insert mt tal sheet. However, the s trength of these joints was of the same order as that of the aluminium join ts. The fracture mode of these joints varied with the welding current. The suitable welding current for steel to aluminium joints varied between the v alues suitable for steel to steel and aluminium to aluminium joints. The fa tigue strength of joints using insert metals was somewhat lower than that o f the aluminium joints.