P 1029 – Determination of properties of the welding result between aluminum and steel by magnetic pulse welding
The joining of aluminium-steel-connections in constructions for transportation is mainly realized with mechanical joining-technologies and adhesive bonding. Alternatively to conventional processes, Magnetic Pulse Technology (MPT) can be used. Previous developments in Magnetic Pulse Welding (MPW) were focused on aluminium-copperconnections, here, low alloyed mechanical properties do not exist or exist in an insufficient quality. However, this is the case for unalloyed steel-aluminiumconnections. Based on the state of the art, selected steel-aluminium- connections were analyzed regarding their weldability. Additionally, a surface treatment was used to improve the potential of this process. High-strength and ultra-high-strength steel-alloys were welded to aluminium-alloys belonging to the 5xnn-, 6xnn- and 7xnn-series. After investigating the basical feasibility of different steel-aluminium- connections, statistically significant series of tests were welded and analyzed. Furthermore, the influence of production variations and tolerances as well as reasons for statistic variations of the mechanical strength properties were explored. As a result, methods for increasing the welding seam quality could be developed. It could be pointed out that especially the welding seam area represents an indicator for the joining quality. Compared to the conclusions of corrosion testing and fatigue strength testing, it is primarily weld irregularities that can influence the welding seam strength. In summary, the results show the verification of the fatigue strength of Magnetic Pulse Welding with a high corrosion resistance. Combined with the state of the art, metallographic analyzes confirm the existence of intermetallic phases. However, these phases can only be detected locally and at the beginning of the welding seam. Due to this, negative effects of the detected phases are not on hand. Therefore, the high potential of Magnetic Pulse Welding with steel-aluminium- connections can be confirmed with a high reproducibility.
The results of this research enable a custom-designed dimensioning of a welded connection with regards to the materials.