EVALUATION OF ZINC IN LASER BEAM BRAZE WELDING OF GALVANIZED STEEL SHEETS

Abstract

For more than a decade, the automotive industry has employed the laser welding-brazing process in the manufacturing of vehicle bodies, where the quality of the brazed seam is an important requirement, especially when exposed to the customer. One aspect that compromises the quality of the seam is the presence of zinc in the coating of galvanized steel sheets. In this context, a comparative study was conducted between two wire feeding methods in laser welding-brazing (pulling and pushing) to mitigate the presence of zinc in the brazed seam region and to evaluate the thickness of the iron-silicon intermetallic layer, which can impact the mechanical strength of the joint. A single laser beam was used for the welding-brazing, with silicon-copper wire addition and two sheet thicknesses. Scanning electron microscopy analyses with attached EDS showed that, despite the low detection, for the thinner sheet, there is a difference in the amount of zinc in the fused zone between the feeding techniques. Additionally, EDS mapping confirmed the presence of an intermetallic layer composed of iron and silicon, whose thickness is greater for the pushing wire addition method, considering the higher heat input compared to the pulling method.