During the last decades one of the main challenge in the automotive field has been weight reduction to satisfy the EU's demands concerning fuel consumption and environmental aspects. Consequently, various materials are being considered. Using different materials for different automotive parts requires advanced joining techniques. The present work deals with the most frequently used joining technique, namely resistance spot welding. Additionally, laser welding is being considered, since it is obvious that this technique is being used for more and more parts.
Since the welds of the dissimilar joints have to fulfill demands concerning formability, corrosion resistance and fatigue, the overall goal of this investigation is to find the best welding or joining parameters to achieve optimal joint performance in terms of structural integrity and part requirement.
The steel grades involved in creating dissimilar joints are two austenitic stainless steel grades (EN 1.4301 (304) and EN 1.4318 (301LN)) and three ferritic non-stainless grades (ZStE340, DP600 and St14) with various thicknesses. The corresponding laser and spot welding parameters, microstructures, hardness mappings and mechanical properties were recorded. In laser as well as in spot welding the weld or nugget became fully martensitic. Correspondingly, the hardness clearly increased. The influence of the welding speed for laser welding and the welding current and post welding heat treatment (PWHT) during spot welding was investigated.