INFLUENCE OF PROCESS PARAMETERS ON STRENGTH OF RESISTANCE SPOT WELDMENT OF AUSTENITIC STAINLESS STEEL

Abstract

In the present investigations, the effect of major process parameters of resistance spot welding i.e. welding current and weld time on the strength of the joint has been studied under different stress conditions for 0.3 mm, 0.52 mm, 0.66 mm and 0.72 mm thick austenitic stainless steel sheets (Grade 304). Weld quality was assessed 'by means of tensile-shear, cross-tension and fatigue tests. In each case, separate tests were made for each variable. In each event, failure load was recorded. It was found that failure load increases with increase in welding current and weld time both for tensile-shear and cross-tension tests. By using these results, the ductility ratio of the spot welds was determined for all cases and it was found that ductility ratio decreses with increasing welding current. It is a common recommendation that welds should be made just below initial expulsion because expulsion welds are undesirable and weak. But it was found that weld strength improves under expulsion conditions due to considerable growth in weld nugget size. it was found that weld nugget •.size increases with increasing welding current. Fati,.e test was also performed to determine the fatigue life of the joint. It was found very low because of the notch arround the periphery of weld nugget between the sheets.