Evaluation of Dynamic Resistance as Quality Criterion for Resistance Spot Welding

Abstract

Resistance spot welding is being used extensively in the automobile electrical and consumer goods industries in our country. With high quality coupled with low cost demanded by many industries, it is important to adapt resistance welding controllers for assuring quality of spot welded joints. The present paper examines the dynamic resistance behaviour during resistance spot welding of low carbon steel and austenitic stainless steel with a view to study the applicability of dynamic resistance based controllers Low carbon steel sheet of 1 mm and austenitic stainless steel sheet of 0.5 mm were used for spot welding trials and tensile shear test is used for evaluation of joint quality. Nugget diameter and indentation were again measured. The details of instrumentation system for dynamic resistance measurement and method of computation are being discussed. Dynamic resistance values are computed for every weld trial and parameters such as current pressure and time are varied to study its influence on be: i dynamic resistance as well as tensile shear strength. It was found that there is good correlation between tensile shear load, nugget diameter and indentation with the percentage drop in dynamic resistance. This work suggests that the percentage drop in dynamic resistance can be used as criteria for ensuring the quality of the spot welded steel joints.