Effect of Welding Parameter on the Nugget Overlap and Nugget Formation in Resistance Seam Welding of Secondary Coated Steels

The use of flexi-fuel in automotive fuel tanks is gaining prominence globally for reducing the dependency on fossil fuels and sustainability. Hence, coated steel with improved corrosion resistance is required to accommodate the ethanol-blended fuel. In this study, secondary coated steels over the primary hot dip galvanized steel (HD-GA) were evaluated to understand the weldability of the coating. Welding parameters such as welding current and welding speed for a constant pressure were varied to generate the weld lobe. Based on the developed weld lobe, the weld ON and cool cycle effect with respect to welding speeds was evaluated to understand the nugget formation and overlap. Insufficient heat input resulted in a lack of fusion and joint with coating entrapment, while beyond the threshold heat input, a nugget with complete fusion and no coating entrapment was observed. It was also observed that higher welding speed played a critical role in reducing the liquid metal embrittlement in coated steel. In contrast, lower welding speeds helped produce nuggets with good overlap, resulting in a leak-proof joint. The study provides a correlation between all the welding parameters, such as welding current, welding ON and cool time, welding speed, and welding pressure on the weld quality.