GAP TOLERANT JOINING OF 22MNB5 STEEL BY LASER HYBRID WELDING WITH BEAM OSCILLATION AND LASER BRAZING WITH TWO LASER BEAMS

摘要

High strength steel is increasingly being used in welded automotive structures. For joining, challenges arise from air gaps which are difficult to compensate by clamping due to the high stiffness of the components. This paper gives an overview of two different approaches for joining press hardened 22MnB5 material with air gap. A laser-GMA hybrid welding process was developed that utilizes a 1 kW single mode fiber laser to stabilize the arc at high welding speed of 6 m/min. It was demonstrated that a lateral beam oscillation was beneficial for the stability of the process and the quality of the joint, and that fillet welds in overlap joints were capable of bridging 0.8 mm of air gap. In an attempt to identify a joining process with even lower heat input, laser brazing with copper based filler material was applied to the same joint configuration. In this case, the base material was preheated by a second laser beam of low intensity to improve wetting. The feasibility of the novel brazing process was demonstrated, and a process speed of 4 m/min and the bridging of an air gap of 0.8 mm were achieved.