Study On Laser-MAG Hybrid Weaving Welding Characteristics

Laser-MAG hybrid welding is widely applied in the welding of thick plate,because of its characteristics of large penetration and high efficiency. Because itconsists of the heat source of laser and arc, the morphoglogy of weld is “wine-glass”type, in which upper part is wide but lower part is narrow,. This type of morphologycauses large size inhomogeneity. Because the weld pool of laser is deep and narrow,it is easy to produce blowhole defects.So the laser-MAG hybrid weaving welding was put forward. In order to realizethe bead welding, this paper established two sets of welding system, laser-MAGhybrid weaving welding and weaving laser-MAG hybrid welding. The processproperties was studied comparetively. The effect of weaving parametres on weldingappearance and welding stability was analyzed and optimization of processparametres was determined. From the aspect of porosity and microstructure, theeffect of agitation of laser to welding pool was further studied.Based on the motion of mechanical arm, the laser-MAG hybrid weavingwelding was established with the maximum weaving frequency of6Hz. Laser-MAGhybrid weaving welding could reduce the size inhomogeneity effectively, while thepenetraion was decreased. In order to make the welding cross-section morphlogysymmetrical, the weaving frequency was not less than6Hz under the welding speedof1m/min. However, the limit of weaving frequency of machanical arm limisted theavalible range of parametres. In the process of arc weaving, the change of wire stemlength influenced the stability of drop transiton behavior.Based on programmale focusing lens, weaving laser-MAG hybrid welding wasestablished, with the maximum frequency of80Hz. Weaving laser-MAG hybridwelding could reduce the size inhomogeneity effectively, while the penetration wasdecreased. The improvement of weaving frequency expanded the scope of availabelparametres. In the welding process, the arc shape of pulse MAG was not changed, aswell as the drop transition. When the weaving frequency was larger than6Hz, theappearance was not changed with the increase of weaving frequency, while thepenetration was decreased shapely with the increase of weaving amplitude.The opposition of columnar crystal was avoid since the change of weldappearance, which avoid the impurity elements segregation. The weaving frequency of10~20Hz reduced the number of porosity significantly. The stirring of laser to thewelding pool changed the growth angle of columnar crystal. The effect of stirringwas too strong when the weaving frequency was over40Hz, which increased thenumber of porosity and make the columnar crystal fragmentation. The reheating ofweld made the martensite tempered martensite. The effect of laser stirring had alittle influence on the tensile strength, but increased the impact toughness of weld by30%.