Numerical simulation of large spot laser + MIG arc brazing–fusion welding of Al alloy to galvanized steel

Abstract

A finite element model was developed to investigate the thermal process of large spot laser+MIG arc brazing–fusion welding. The laser was treated as a Gaussian plane heat source, the MIG arc was performed as a modified double ellipse Gaussian plane heat source, in which the arc distortion was taken into consideration and the overheated droplet was treated as a uniform body heat source. The calculated weld bead geometry and heat-affected width of zinc coating had good agreement with experimental results. The temperature field, especially for the brazed interface, showed non-uniform and asymmetric distribution. The thermal cycles at brazed interface had obvious bimodal characteristic at arc center and laser spot center and the high-temperature zone at the brazed interface was widened duo to the introduction of laser beam compared with conventional MIG brazing–fusion welding. A fundamental processing window was determined based on the founded model to satisfy a certain energy condition, in which the Al alloy was fully penetrated and steel plate was not melted.