Effect of activating flux on laser penetration welding performance of galvanized steel

To study the feasvhibility of activating welding technique in increasing the width of low-power pulsed laser penetration weld joint and to improve the efficiency of low-power laser welding while reducing cost, theoretical analysis and experimental verification are conducted in this study to determine the effects of activating flux Cr2O3 on the welding performance of DC56D galvanized steel plate for a vehicle body. Research data on the variation in weld width, joint microstructure, mechanical properties, distribution of elements, and corrosion resistance are acquired. Results indicate that activating flux can effectively increase the YAG laser energy absorption of the steel plate and melting of parent metals, thus increasing the weld width. Although the joint microstructure is dominated by refined isometric crystals and columnar crystals, the heat-affected zone expands slightly because of the activating flux. No evident diffusion and segregation of active elements are observed in the weld joint. The involvement of activating flux does not change the relative contents and distribution of chemical components of the weld. The welded test piece with activating flux is superior to that without activating flux in terms of tensile strength, microhardness, and corrosion resistance, indicating that the addition of activating flux effectively improves the performance of low-power laser penetration welding test pieces.