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1. Introduction
Resistance spot welding (RSW) is a commonly applied technique to join the sheets in the manufacturing industry (Aslanlar, 2006), where the weld is made by a combination of heat, pressure and time (Hayat, 2012). Spot welding might be performed physically, mechanically or by a dedicated spot welding machine. It is the most prevailing joining system for thin sheets in vehicle production in view of its minimal effort, fast (short preparing time), great computerization and has awesome potential for joining sheets in the car business. The required low voltage (5–20 V) and high current force (2000–15,000 An) is gotten from the transformer and weight is acquired from the technician, water-powered and pneumatic equipment.
In spot welding, overlapped workpieces are placed between electrodes, trailed by heat using current momentum for a short time cycle. There are three phases in making spot welds, where, first, the electrodes are united with the job and force is used before the supply of current, and the third stage is the hold time where the current is turned off (Babu et al., 2012). The value of current varies from 3,000 A to 100,100 A for a few seconds, depending upon the material characteristics and thickness. The contact portion is heated, and metal of that area changes to molten state due to movement of current through the electrode and workpiece. An attempt has been made to investigate the mechanical properties of the lap joint in resistance spot welding. The optimization of process parameters was done to achieve a higher surface finish. Neystani et al. (2019) attempted to contemplate the effects of RSW parameters on the mechanical properties for dissimilar joining of Fe-Cu-C and low carbon steel. The result of the Taguchi method showed that preheat current, preheat time, hold time, welding current and welding time were the main parameters, which affected the welding strength. The maximum hardness and maximum strength of joint were observed as 735 HW and 5.75 KN, respectively. The application of low welding current and high preheat current increased the hard zone width. Essoussi et al. (2019) investigated the mechanical performance and microstructure of RSW of AISI 1000 series steel (FS) and AISI 304 stainless steel (ASS). The best tensile shear strength was observed in homogeneous ASS/ASS.