Robust Schedules for Spot Welding Zinc-Coated Advanced High-Strength Automotive Steels
Spot welding is the prominent joining process for assembling steels in vehicles. Spot weldability is measured in terms of weld lobes. A wider (robust) lobe represents better weldability. Unfortunately, recently developed advanced high-strength steels (AHSS) exhibit poor spot weldability (narrow weld lobes) with conventional weld schedules. The present work is thus aimed to develop a robust spot welding schedule for selected AHSS combinations.
Weld lobes were plotted with upsloping pulse, single pulse and multiple pulse weld schedules. Nugget growth study for zinc coated Dual Phase (DP) 600 was conducted. Fast nugget growth in DP600 steels was controlled by interrupting the heat input during a weld pulse. An enhanced weld schedule consisting of two pulses with reduced current on the second pulse was designed. It was found that the first pulse removed zinc and the second pulse controlled the nugget growth. The enhanced weld schedule showed a considerable increase in the lobe width over the conventional weld schedule for DP600 steels.