Dissimilar Welding of ferrite and austenite stainless steels using resistant spot welding

The effect of welding parameters (electric current and time) on microstructure and hardness of dissimilar resistant spot welding of ۳۰۴ with ۴۳۰ stainless steel sheets was investigated. ۳ different welding time of ۰.۴, ۰.۸, and ۱.۲ s and ۳ different electric currents of ۲۵۰۰, ۳۷۵۰ and ۵۰۰۰ A were applied. After welding the specimens were cut and prepared for microscopy studies and hardness ones. The heat of welding zone affects the adjust zone called heat affected zone. The grain size of this zone rose up to ۸ times larger than the base metal (۶.۱ to ۴۷ μm).The results also showed that the increment of welding time enlarge the grain size of this to a wider extent. The hardness of heat affected zone in the side of ۳۰۴ steel decreased from around ۲۶۰ HV to almost ۲۲۵ HV. However, in the same zone of ۴۳۰ alloy, the hardness increase as the distance with the welding zone decrease, which is the result of the formation of carbides.

Keywords:

dissimilar welding , stainless steel , resistant spot welding , microstructure , hardness