Study On Laser-MIG Hybrid Welding Process For Medium Thinkness Plate Of 304 Stainless Steel

Laser-MIG hybrid welding is a novel,high efficiency,high quality,and energy-saving welding method.The bridging ability,metallurgical properties and microstructure of the weld are improved by utilizing the advantages of MIG filling wire.Compared with single laser welding and arc welding,it is more adaptable and much more often used in the welding of medium-thick plates.However,due to the introduction of the arc heat source,the tunable welding parameters are far more than a single welding method.When the welding parameters are selected improperly,welding defects still occur,and the parameters are difficult to control and optimize.Therefore,aim at medium-thick plate iron and steel materials,it is a hot issue in the field of welding to study the influence of process parameters on the quality of laser-MIG hybrid welded joints.This project selected 5mm thick 304 stainless steel plate,and used laser-MIG hybrid welding platform to bead and butt welding experiment.The macroscopic morphology and microstructure change of the weld under several welding methods were studied.The interaction mechanism of laser and arc was studied.The influence of laser and arc energy matching on the penetrating ability and forming of the weld was studied.And the influence of process parameters on the formation,porosity and mechanical properties of the weld were studied.During the experiment,it was found that:?1?The interaction between the laser and the arc includes two mechanisms:the preheating of the arc and the interaction between the plasmas.The composite effect of the laser and the arc is finally manifested by enhancing the melting efficiency of the hybrid welding,thereby improving the bridging capability,the penetrating ability,the forming ability and properties of the hybrid welding.?2?Regulating the energy ratio between laser and arc affects the penetrating ability and weld surface formability of the hybrid weld by changing the energy superposition state of the heat source and the interaction effect between the laser and the arc.At each laser power,there is an optimum energy ratio that makes the weld fully penetration and forming best,in which the optimal energy ratio will decrease with the increase of laser power.?3?By analyzing the influence of process parameters on the quality of welded joints,the optimum parameters for butt welding of 5mm thick 304 stainless steel are:laser-arc distance D_LA=1mm,defocusing amount D_ef=-1mm,laser power P_L=4.3kW,arc power P_A=3.0kW,welding speed v=1.8m/min,wire feed speed V=5.0m/min.?4?In the laser-MIG hybrid welding process,the mechanical agitation and post-heat treatment produced by the arc will affect the distribution of the temperature field,electromagnetic field and flow field of the molten pool,so that different areas of the weld have different morphology and size of microstructure and microhardness.The grain size in the upper area of the weld is smaller than the middle area and the lower area of the weld,and the microhardness value tends to increase along the depth of the weld.