Joining technology and mechanical properties of laser-beam welded joints with martensitic chromium steels

Investigations were undertaken on welding of press-hardened martensitic stainless steels in similar joints as well as in combination with state-of-the-art and modern steel grades. Parameter development was conducted for square-butt and lap joint configuration aiming at the production of defect-free welds. In order to homogenise the mechanical properties of the weld area, a heat treatment has been developed and applied successfully. Tests on load capacity of lap joints have been carried out under quasi-static and dynamic loading using the LWF-KS2 concept. Emphasis is laid on the investigation of contour welds. Especially for the chromium steel a strong dependence on the load angle was detected. Heat treatment led to a significant improvement of strength and ductility. Independent of heat treatment and seam weld shape, uni-directional fatigue testing of lap joints shows similar endurable load amplitudes. The critical location of failure is the intersection of the fused zone with the joint plane.