Experimental Study of Dissimilar Double Pulse Resistance Spot Welded Austenitic Stainless Steel and Weathering Steel

The aim of this study is to prevent thermal cracking in the fusion zone of dissimilar resistance spot weld, which arises due to the electrical and thermal conductivity differences of austenitic steel and weathering steel. Therefore, dissimilar double pulse resistance spot welding experiments were carried out on 4-mm-thick 301LN austenitic stainless steel and 09CuPCrNi weathering steel sheets. The first low-current pulse was used for prewelding, and the second high-current pulse was used for weld generation under a high electrode force. Under these conditions, satisfactory welds that met the welding criterion without thermal cracks or central shrinkage cavities were obtained. In the fusion zone of the double pulse weld, the phases present were lath martensite, δ-ferrite, austenite and phosphorus-rich eutectic. There was a small amount of austenite in this zone, and the eutectic appeared at the grain boundaries. The failure mode of the double pulse weld was pull-out fracture. Finally, the load-bearing capacity of the double pulse weld was 35% greater than that of the single pulse weld.