STRENGTH ANALYSIS OF LASER BEAM WELDED STEEL - ALUMINIUM JOINTS FOR MARITIME LIGHT WEIGHT APPLICATIONS

The application of a laser beam welding process to join steel to aluminium using a high-power laser is demonstrated to provide a joining process for semi-manufactured steel-aluminium products for the maritime industry. On the basis of lap joints made of S355 steel (t = 5 mm) and the aluminium alloy EN AW-6082 T651 (t = 8 mm), the feasibility of joining dissimilar materials is shown. To date, a combination of steel and aluminium is well known to have a low weldability due to the differing physiochemical properties of the two materials and the formation of intermetallic phases. The weld seam quality and strength greatly depends on the amount of intermetallic phases within the joint and the local weld geometry, so that different process parameters are investigated within the welding process development. Quasistatic investigations on lap joints and adapter specimens, with up to six weld seams, show an increase of the tensile shear strength for optimised parameters and for an increased number of weld seams. The dependency of the quality of the weld on the major geometrical parameters, weld width and penetration depth, is moreover shown by the fatigue strength of lap joints. Promising fatigue test results on adapter specimens emphasise the potential for applying steel-aluminium laser welds in ship design in the future.