Effects of Transformer Tap Settings on the Resistance Spot Weldability of Hot-Dipped Galvanized Steel: Nugget Development Studies

This paper is a continuation of previous work on the effects of tap setting and percent heat on the weldability of galvanized steel. A previous work dealt with changes in current range behavior. This paper considers changes in nugget development. Six separate tap settings were selected for study corresponding to a range of off-times in the current wave form at expulsion. Welds were then made at each tap setting for increasing weld times and sectioned metallographically. It was found that the change in off-time led to significant changes in the morphology, size and rate of weld growth. These results were explained in some degree through changes in the mechanism of resistance heating for various off-times.