| At present,5083 aluminum alloy is widely used in aerospace,high-speed trains,LNG vessels and cars and so on.In this dissertation,laser-MIG hybrid welding of 5083 aluminum alloy process stability and its forming defects has been researched.The paper discussed the welding parameters on the stability of the welding process and weld forming,at the same time,under the condition of penetration,the influence of welding parameters and groove parameters on the internal porosity defects in butt weld was explored.Finally,a good welded joint was obtained by optimizing the parameters,and the microstructure and mechanical properties of the joint were analyzed.In this paper,based on two kinds of droplet transition,the influence of welding parameters on the process stability and formation of the weld is explored,the results show: Under the two droplet transfer conditions,with the increase of laser power and distance between the heat sources,the stability of the welding process and the formation of the weld become better and then deteriorate.With the increase of the welding speed,the stability of the welding process and the formation of the weld become worse.The laser power should be matched with the welding speed.When the welding speed is low,the smaller laser power can maintain the stability of the welding process,too large laser power will reduce the stability of the welding process,and result in poor weld formation;When the welding speed is high,the smaller laser power cannot maintain the stable combustion of the arc.By contrast,when the welding speed is <2m/min,the laser power is about 2000W-4000 W is proper of short circuit transition.When in spray transition,the welding speed should be lower than 3m/min,the proper laser power is about 2000W-4000 W.Larger laser power or higher welding speed are difficult to ensure the stability of the welding process.When other process parameters are selected properly,the case of short circuit transition,the distance between the heat sources of 3mm is more reasonable choice,the case of droplet transfer,the distance between the heat sources in the 1-5mm range can be selected,in other words,the process window is larger.In addition,from the forming point of view,when the welding process is stable,the weld formation is good,at the same time,under any parameter conditions,the weld forming of short-circuit transition is worse than the spray transition,so the actual welding should choose the spray transition.Secondly,the effects of welding parameters(laser power,welding speed,the distance between heat sources)and groove parameters(bevel angle,butt gap)on the internal porosity defects of 6mm thick 5083 aluminum alloy butt weld were studied.The results show: Increasing the laser power the upper porosity will not change(0.2 %-0.3 %),the lower porosity increase and the average pore size will increase.Increasing the welding speed the upper porosity will not change basically(0.1 %-0.3 %),and the lower porosity and the average pore size will both decrease and then increase.When the distance between the heat source is 3mm,the porosity and the average pore size are the smallest.When the distance between the heat sources is 1mm,5mm,7mm,the porosity of the upper weld seam increases with the increase of the diatance,but the total porosity and average pore size not change basically.The upper porosity,the lower porosity,the total porosity and the average pore size decrease with the increase of the bevel angle.Reasonable butt gap can effectively reduce the weld porosity and porosity average size,when the butt gap is 0.6-0.9mm range,porosity has been less than 0.8%.The experimental laser power 3200 W,welding speed 1.5m / min,the distance between the heat source 3mm,bevel angle 30 °,butt gap 0.9mm,can be obtained less porosity defects welded joints.Finally,using the above parameters,the 6mm thick 5083 aluminum alloy laser-MIG hybrid welding joint was obtained and the microstructure and mechanical properties of the welded joint was analyzed.The results show,the upper part has coarse grains,the center is equiaxed,columnar crystal features are not obvious of the weld edge;the bottom part has lower heat input,so the grain is smaller than the upper part,the center is equiaxed,the edge is columnar crystal.The weld zone hardness is slightly lower than the base metal,the upper part of the weld hardness slightly lower than the weld,EDS results show that,changes in the hardness of welded joints mainly associated with the loss of Mg elements.Tensile test shows that: the tensile strength of welded joints is about 90.8% of the base metal,the elongation is about 81.9% of the base metal.Tensile fracture of specimens was observed by SEM.A large number of dimples were found,which showed obvious ductile fracture characteristics. |
