The present paper reports the resistance spot welding of steel and aluminium sheets using aluminium clad steel sheets as insert metals. Intermetallic compound layers were formed in the weld zones in direct spot welding of steel sheets to aluminium sheets. Thus, the strength of these joints was lower than that of aluminium to aluminium joints. Intermetallic compound layers were also formed at the steel/aluminium interfaces of the insert metal in welding of steel to aluminium using an insert metal sheet. However, the strength of these joints was of the same order as that of the aluminium joints. The fracture mode of these joints varied with the welding current. The suitable welding current for steel to aluminium joints varied between the values suitable for steel to steel and aluminium to aluminium joints. The fatigue strength of joints using insert metals was somewhat lower than that of the aluminium joints.

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Factors influencing spot-weldability of steel to aluminium with an intermediate layer of aluminium clad steel: Dissimilar metal joining of steel to aluminium with intermediate layer (Report 2), Welding International, 10:12, 943-954, Summary: This paper deals with the resistance spot weldability of steel to aluminium alloy using an intermediate layer of aluminium clad steel. Five types of clad sheet with various steel/aluminium thickness ratios were produced by hot rolling. The mechanical properties of the clad sheet changed with the thickness ratio and ranged between those of steel and:those of aluminium sheet. The peel strength of the steel/aluminium interfaces was greater than 25 N/mm.Materials used in spot welding were 0.8 mm thick EDDQ steel sheet, three types of 1.0 mm thick aluminium alloy sheet and the clad sheet mentioned above. Spotweldability, including suitable welding current, nugget diameter, tensile shear strength and thickness of the intermetallic compound layer formed at the interface of the clad sheets, changed with the thickness ratio of the clad sheet. From these results, it was concluded that spotweldability was affected by the thickness ratio of the clad sheets.Spot-weldability was also affected by the alloying elements in the aluminium alloy sheet. Tensile shear strength and nugget diameter varied in various types of aluminium alloy sheet.

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