Study on laser-MAG hybrid weaving welding characteristics for high-strength steel

Abstract

To improve the inhomogeneous morphology and porosity defects of the laser-MAG hybrid welds, laser-MAG synchronized weaving welding and scanning laser-MAG hybrid welding were developed for the bead on plate welding of high-strength steel. Based on the mechanical motion of robot, the laser beam and arc torch synchronized weaving were realized during the laser-MAG synchronized weaving welding process. With respect to scanning laser-MAG hybrid welding, only laser beam weaving was performed using the scan head. The influences of weaving frequency on the weld formation and porosity defects were investigated. The mechanical properties, including the ultimate tensile strength and impact toughness, were comparatively discussed. The results indicate that the desired homogeneity and continuity of weld morphology could be obtained under the condition that the weaving frequency was no less than 6 Hz. Scanning laser-MAG hybrid welding is an alternative technique for weaving welding compared to laser-MAG synchronized weaving welding. The weld penetration decreased with the increasing weaving frequency. The maximum reduction of weld penetration was about 43.7% compared to that of laser-MAG hybrid welding. The optimal weaving frequency for the porosity defects suppression was 20 Hz. The welds of scanning laser-MAG hybrid welding with the weaving frequency of 20 Hz possessed better impact toughness, increased by about 31.4% than that of laser-MAG hybrid welding. The weld porosity defects were suppressed due to the stirring effect of laser beam to the molten pool. The formation of staggered columnar crystal in the weld prevented the crack propagation successfully during the impact testing process.