Increase of the Reproducibility of Joints Welded with Magnetic Pulse Technology Using Graded Surface Topographies

The reproducibility of individual welding methods depends to large extents on the material properties. This is especially the case for impact welding as tests have shown that the surface properties influence the joint formation. With the aim to influence the formation and position of the lower curve of the welding process window, this paper focuses on how the surface topography influences an asymmetrical impact. Additionally, relevant process parameters (e.g. collision speed, collision angle, jet formation) will be included and disturbance contours that are placed transversely to the collision vector will be examined. A high-speed camera was used to measure the collision speed as well as the collision angle. The specific surface topographies were created using belt grinding (cutting with geometrically undefined edges) and laser ablation (non-cutting process, local vaporization of materials through pulsed laser beams). The tests exemplarily show a strong correlation between the surface geometries and the joint. The disturbance contours that were introduced transversely to the collision vector shift the lower weld seam boundary, whereas a reduction of the discharge energy leads to a relative strength of the joint of 1.0. In sum, this paper offers fundamental insights into the mechanisms of the joint formation when using magnetic pulse welding and shows the influence of the surface topographies on the conflict between relevant procedural parameters and the possibility to shift the lower procedural window.