Optimization of Resistance Spot Welding Parameters in a Shop Floor Environment to Achieve Desired Spot Size in Low Carbon Steel Sheet

Resistance Spot Welding (RSW) is widely employed in automotive, electronics, furniture, Coach building and package industries. Although various spot weld methods, such as Friction Stir Spot Welding, MIG Spot welding, Laser Spot welding and Ultrasonic Spot welding are in use, Resistance spot welding is a versatile and easy method to adopt in simple fabrication shop. It is well known that various factors significantly influence the spot size and its quality. Designers, while selecting RSW process are particularly interested in fixing the appropriate spot size and pitch distance for a specific application. Against the above background, this study has been carried out to arrive at desired spot size by varying the parameters using a simple shop-floor spot welder which is readily available in any fabrication shop. Three levels of power input, three levels of welding current time and many levels of weld cycle time have been adopted for 2mm thick low carbon steel sheet of IS 513 grade. A novel technique has been developed to apply adequate torque to shear the spot weld joint without any damage or distortion. Spot size has been determined by using vernier and profile projector. The nugget quality has been examined using optical microscope at different magnifications. The bond strength of the spot weld has been determined by tensile shear test. By adopting this simple technique, it is possible to achieve desired spot size which is defect free and having excellent penetration. Keywords: Low carbon steel sheet, Resistance Spot welding, Nugget size, welding parameters, macro & micro examination.