Studies on the influence of process parameters on the AISI 316L resistance spot-welded specimens

Resistance spot welding (RSW) is a popular welding process employed for joining sheet metals typically in automobile and aerospace industries. RSW is conventional but not obsolete as it addresses the desirable characteristics of energy efficiency, narrow heat-affected zone (HAZ), simplicity, and automation that make it the first choice of manufacturers. In recent days, there is a perpetual demand for spot welding owing to its suitability for joining components especially in biomedical applications. Austenitic stainless steel of grade AISI 316L, a biocompatible material with extraordinary features and global suitability, caters to several industrial dimensions. In this research paper, an attempt is made to experimentally investigate the quality of the weld prepared by resistance spot welding of austenitic stainless steel type 316L of equal thickness (2.0 + 2.0 mm). Experimental trials based on design of experiments (DOE) are conducted by varying the process parameters such as electrode tip diameter, welding current, and heating time and subsequently measure the nugget size and shape which governs the strength and bond integrity of the resistance spot welds. Subsequently, a coupled structural-thermo-electric analysis is performed to analyse the transient temperature field for predicting the nugget formation during RSW of 316L stainless sheet using a 2D axisymmetric finite element (FE) model. FE-based model of RSW process is developed using ANSYS Parametric Design Language (APDL) module available in FE package, ANSYS. Thermo-physical interactions like heat transfer through the Joule effect, the effect of latent heat of fusion, and the thermal and electrical contact conductance are considered while developing the FE-based model. A good coherence is achieved between numerical predictions of nugget shape and experimental spot-welded results. Finally, the welded specimens are subjected to destructive testing and metallurgical characterizations to evaluate its strength and quality.