Non-destructive methodology for parameterization of Burn-Zinc in the resistance spot welding process

Galvanized steels are used in large quantities, mainly in the automotive industry, for their corrosion resistance and low cost. In this industrial sector, these materials are normally welded by the spot welding process. Because galvanized steels have a zinc-based covering layer, welding is normally carried out using a technique called the Burn-Zinc technique, to minimize the harmful effects of the zinc on this material, during the welding cycle. In this context, this work studied a non-destructive method, with the aim of finding suitable removal of this layer of zinc, on the basis of the signals generated by a sensor that records the electrode displacement during the phases of the spot welding process, taking the reading for the thermal expansion of the galvanized steel sheet as a basis. Thus, physical simulation experiments were undertaken, varying the current and the cycle time of the preheating phase. The Burn-Zinc responses generated by the sensor and the visual analyses by attribute were shown as graphs via an operating envelope. The evidence showed that the signal from electrode displacement proved to be an efficient non-destructive method for determining suitable Burn-Zinc parameters in the spot welding process for galvanized steel sheet.