Laser beam welding is a very efficient process for joining copper pins in electric drives, which are referred to as hairpins. The occurrence of pores reduces the conducting cross-sectional area, which increases the electric resistance and further impairs the tensile strength of the joint.
The present work compares different welding strategies regarding the formation of pores and spatters during welding cu-hairpins. The welding strategy was varied by different geometries of the scan contour, different beam shapes and an adaptive line energy. Different beam shapes were realized using a two-in-one beam delivery fiber and using a civan laser. In order to capture the formation of pores, the processing zone was observed by means of X-ray imaging at the IFSW in Stuttgart and at Petra III at Desy in Hamburg. The formation of spatters was observed using a high-speed camera. With the observation it was possible to separately determine the influence of scan contour and beam shape on the formation of pores and spatters. Finally, these findings were applied to identify beneficial welding strategies to reduce the formation of pores and spatters. Furthermore, tensile testing proves the increase of the tensile strength of the hairpins, which were welded with the optimized welding strategies.