Innovative hybrid welding process for structural steelwork engineering—Laser submerged arc hybrid welding

The welding of thick metal sheets has become increasingly important for structural steelwork engineering applications (e.g., pipe- or crane building). Nowadays, welding tasks are performed using a time-consuming conventional submerged arc welding process. Here, a large number of welding passes are necessary, which leads to a thermally induced distortion. Therefore, there is a high demand for a welding process which allows a cost-effective welding of thick metal sheets. By the development of a laser beam submerged-arc hybrid welding process (LUPuS), a technique is created which combines the high penetration depth of the laser with the high thermal efficiency of the submerged arc process. This leads to synergy effects which predestine LUPuS for the given welding task. Earlier projects have shown a general feasibility of LUPuS. Steel plates with thicknesses of up to 50 mm have been joined without any welding issues using the double-sided single pass technique. However, different results of the notch impact test in the laser beam-dominated and submerged arc-dominated welding areas are noticeable. This contribution will demonstrate the effect on the mechanical-technological properties in the different welding seam areas by changing the flux and the wire of the submerged arc welding process. In order to investigate these properties, impact strength tests have been performed. Moreover, the dynamic behavior of the molten pool was studied. Furthermore, the results of the investigation of the weld metal structure are presented.