The effect of arc position on laser-arc hybrid welding of 12-mm-thick high strength bainitic steel

More attentions have been paid on humping characteristic in single pass high energy density welding of medium or thick plate in recent years. In this paper, the hump phenomenon of the weld root is observed by laser-leading laser-arc hybrid welding of 12 mm-thick steel plate. Combining with the surface molten pool flow behavior, force mechanism of force analyzed, the hump formation process can be divided into pool pooling stage, pool sagging growth stage, and the solidification stage. It is proved that the balance between gravity and surface tension of the molten pool is the main reason for the formation of hump. Furthermore, the arc-leading laser-arc hybrid welding process was realized to obtain single-pass welding joint without hump defects. In view of comparing and discussing the droplet transition feature, electrical parameters, and exerted force under the optimal process of arc-leading and laser-leading, we had a better understanding of reasons why the arc-leading inhibits the formation of hump, and proved that the arc-leading electrical parameters are more stable.