Study On MIG Welding Process Of Aluminum Alloy 5083、6082 Used In Railway Vehicles

The manufacture of lightweight high-speed train was a long-term goal for domestic and international designers and users.Without any doubt,aluminum alloy was one of the preferred options.Aluminum alloy with lightweight,high strength and corrosion resistance features now has become the main material of high-speed train body.Aluminum alloys 6082 and 5083 were widely used in high-speed train bodies.With good quality and high productivity,MIG welding was the main welding method of aluminum alloy material for high speed train.In this paper,Butt joints of aluminum alloys 6082 and 5083 were prepared by the MIG one-side welding with back formation.The effects of welding parameters on weld formation were studied.With the rise of welding current,the weld width and reinforcement of aluminum alloy 6082 and 5083 increased.With the rise of the welding voltage,the width of the welded joint increased and the weld reinforcement increased slightly.With the rise of the welding speed,the weld scale patterns became sparser,and the width and reinforcement of weld joint decreased.With the decrease of argon flow rate,the welding spatter increased.The width and reinforcement of the weld remained approximately constant.When the flow rate of argon was 5L / min,the welding seam was badly shaped and had not scale patterns.Effects of the welding parameters on the microstructures and properties of welded joints were systematically studied.The phases of aluminum alloy 6082 and 5083 weld metal are mainly α-Al+Mg2Si and α-Al,respectively.The weld bead of the two joints was composed of cystiform-dendritic.The coarse columnar grains mainly exited near the fusion line.With the increase of welding current,the tensile strength of aluminum alloy 6082 and 5083 decreased but the fracture elongation of aluminum alloy 6082 joint increased and the elongation of aluminum alloy 5083 joint decreased.With the increase of welding voltage,the tensile strength of aluminum alloy 6082 and 5083 joints remained approximately stable and the elongation of the joints decreased.With the increase of welding speed,the tensile strength and elongation of aluminum alloy 6082 and 5083 joints increased firstly and then decreased,and the width of HAZ was decreasing.When the welding speed was 50 cm / min,the tensile strength and elongation of aluminum alloy 6082 were 210.35 MPa and 6.01%,respectively.When the welding speed was 37 cm / min,the tensile strength and elongation of aluminum alloy 5083 were 272.52 MPa and 16.29%,respectively.When the argon flow rate was 5L/min,the tensile strength and elongation decreased significantly.When the argon flow rate was 10-20L/min,the tensile strength and elongation remained stable.The fracture occurred in heat affected zone(HAZ)of aluminum alloy 6082 joints,which belonged to ductile fracture.And there were a lot of dimples in the fracture.The fracture of aluminum alloy 5083 welded joints was located in the weld fusion zone and along the fusion line.And there were a large number of uniform equiaxed dimples,of which the size is larger and deeper than that of aluminum alloy 6082 joints.The bending and tensile properties of 5083 aluminum alloy joints are better than those of the 6082 joints.The porosity of the weld was detected by X-ray and the porosity content was quantified.The porosity of the weld increased with the increase of the absolute humidity.The susceptibility of aluminum alloy 6082 welded joints to porosity was higher than that of 5083 welded joints.With the increase of the porosity,the tensile strength and elongation of the 6082 joint remained approximately constant,but the front and back bending angle were reduced by 74.4% and 64.4%,respectively.And the bending capacity of the joints deteriorated.The tensile strength and elongation of the joints decreased by 4.4% and 15.7%,respectively.But the bending capacity of the 5083 joints was hardly affected.The thermal cracking sensitivity of aluminum alloy welding was evaluated by the modified fishbone test method.It was found that the environmental humidity had no effect on the hot cracking of aluminum alloy welding.The thermal cracking susceptibility of the 6082 and 5083 welds were 42.38% and 30.39%,respectively.The crystal cracks and liquefied cracks occurred in the weld of aluminum alloy 6082.The crystal cracks of aluminum alloy 5083 were found in the weld.