Effects of Strain Hardening on the Fatigue Strength of Cold Rolling 301L Stainless Steel Resistance Spot Welding Joint

Two kinds of standard resistance spot welding fatigue specimens were respectively prepared from 1.5 mm thick domestic and imported commercial grades of cold rolled 301L stainless steel with different strain hardening degrees,by adopting the same resistance spot welding procedure parameters.Fatigue test and microstructure analysis on the two kinds of spot welding specimens were performed.The fatigue limit of the higher strain hardening domestic specimen was lower.There was folding deformation on the edge of spot welding joint of domestic specimen.Recrystallized microstructure and strain hardening microstructure were simultaneously found in the same area,which resulted in not only structural stress concentration but also the one resulting from non-uniform texture.Therefore,folding deformation and stress concentration are the main reasons of fatigue limit decrease.