The effect of laser beam wobbling mode in welding process for structural steels

A laser welding process using a 30-kW fiber laser with scanning mode optics is investigated in the paper. Welding is conducted in two ways: constant laser beam trajectory and wobbling trajectory with the use of lower speed and power. The main goal was to investigate the influence of the second wobbling laser welding pass on microstructure and mechanical properties of structural steel. The following parameters were monitored: visual control and mechanical properties (microhardness, three-point bend, and Charpy impact V-notch test); metallographic analysis and 2D and 3D computer tomography (CT) were also done. The results show that after the second welding pass, with wobbling trajectory of laser beam, middle and cap parts of the seam have a lower microhardness, in relation to the root part. It can be explained by annealing influence of the second wobbling pass at weld metal.