Abstract: The experiments of resistance spot welding for AISI 430 Ferritic stainless steel sheet with 1.2mm thickness was carried out by using the robot DC servo spot welding system. The effect of the welding current on the mechanical properties, the nugget diameter, the microstructure, the micro-hardness and the failure mode were researched. The results show that with the increase of welding current, the strength of the joint increases. When the current reaches 10kA, the splashing phenomenon occurs in spot welding, and it leads to the decrease of joint strength. The joint nugget region consists of coarse ferrite with a small amount of martensite and carbide precipitates. The hardness of the nugget area is higher than that of the base metal zone and heat affected zone. Joints mainly occur button fracture when the nugget diameter is more than 4.8mm. When the nugget diameter is less than 4.8mm, it is interfacial fracture, and usually is brittle fracture.

Key words: resistance spot welding, process parameters, ferrite, 430 stainless steel, failure mode