Numerical analysis of weld bead formation process in the dissimilar material fiber laser welding

The weld bead formation process is closely related to welding materials because of the thermophysical properties involved. In this paper, a 3D numerical calculation model to explore the weld bead formation process in fiber laser welding of dissimilar materials is presented. The formed welded joint during the fiber laser welding of dissimilar materials shows characteristics that are different from that during the welding of the same material. The differences in the thermophysical properties between the materials are taken into consideration in the developed model. By means of comparison with the laser welding of the same material, the corresponding formation characteristics of a dissimilar weld bead are analyzed in terms of temperature distribution, molten metal flow, and thermophysical properties based on numerical simulation results. Due to the differences in the thermophysical properties, the weld bead, the temperature field, and the flow field are asymmetric in the laser welding of dissimilar materials. The moving processes of the two sides of the molten pool are extracted and discussed. The influence of an asymmetrical flow field on both sides of the molten pool is the critical factor accounting for the generation of asymmetric behaviors in the dissimilar material fiber laser welding. The proposed method in this paper can be utilized to provide guidance for revealing the weld formation process in dissimilar laser welding and to obtain weldment with high quality in practical welding.