Influence of weld bead geometry on thermal deformation in laser micro-welding

In this study, the thermal deformation of thin stainless steel sheet was investigated in the bead-on-plate welding by using a singlemode fiber laser with a Galvano scanning system. The numerical simulation was developed to calculate the temperature and stress fields, and its deformation characteristics were discussed. It was suggested that the specimen firstly deformed downward in the same direction of laser irradiation, and then deformed in the reversed direction after laser scanning. The final deformation angle in the negative direction, which is concave shape from the view direction of laser irradiation, was generated under the welding mode of conduction and quasi-penetration for 50 μm thickness sheet. On the other hand, the positive angle of final deformation angle was obtained under full-penetration welding mode, and the extreme small distortion could be achieved by the proper weld bead geometry in micro-welding of thin sheet. It was also confirmed that the similar weld bead geometry was resulted in both quasipenetration and full-penetration welding mode for 20 μm thickness sheet, but the final deformation angle tendency was different in 50 μm and 20 μm specimen thickness. It was clarified that the welding deformation was influenced not only by weld bead geometry but also by specimen thickness.