In shipbuilding, thick dissimilar joints of steel and aluminum are in great demand to reduce the weight and the center of gravity of the ship. On the one hand, the dissimilar joints lead to reduction in CO₂-emissions as result of lower fuel consumption and on the other hand to higher ship stability. The joining process used for manufacturing yachts employs an explosive welded adapter to join both dissimilar parts. However, manufacturing of these adapters is complex, time-consuming and costly. Furthermore, these adapters have an oversized thickness, depending on the material thickness of the steel and the aluminum alloy, in order to achieve the required seam strength. There is a high interest for an efficient alternative.


In this investigation, high-power laser beam welding processes are developed for joining steel S355 (t = 5 mm) with aluminum alloy AA6082 (t = 10 mm) in lap configuration with two intersecting laser beams and additional material. Within this framework, a laser beam source with a maximum output power of P_L = 6 kW is used. Previous studies demonstrated an improvement in mechanical and metallurgical properties of the joints by using iron powder. This approach is now expanded by two intersecting laser beams to create an undercut with the aim of further improving of the weld seam properties. As shown in metallographic analysis and cross tension tests, the approach leads to an increase of the weld seam quality. As one result, the cross tension force F_C can be increased from 7 kN to 12 kN.