Research On The Process Of Thick 7A52 Aluminum Alloy By Laser-MIG Hybrid Welding

In view of traditional arc welding high-strength thick plate aluminum alloy,multi-layer and multi-bead welding mode leads to large amount of groove filling,long clearance between layers and low welding efficiency.In this paper,the method of "laser-MIG hybrid welding bottom +MIG cover" is proposed to achieve high efficiency welding of 20mm thick 7A52 aluminum alloy.Using laser-MIG hybrid welding 14mm realized the penetrating depth of fusion,and then using MIG single bead cover swing welding,which achieve the welding of high quality and efficiency.First,the laser-MIG hybrid welding plate surfacing method is used to study the relationship between the laser power and the process parameters.It is found that the laser preposition is better than the laser after the laser welding.When the current is 170A,compared with 6kW and 8kW,the weld penetration is large when the laser power is 7kW,but the weld formation is poor,while the weld formation is better and the depth of the weld is larger when 6kW.When the power is 6kW,the penetration of melting is maximum relative to 180A and 200A,when the current is 190A.Compared to positive defocus,the penetration of negative defocus is larger.When the negative defocus is-4mm,the penetration is the largest.The experimental study of perforated welding process was carried out by laser-MIG hybrid welding,and several different cover methods were studied and compared.The test results show that the groove is in the form of "10mm" groove with a blunt edge of Y,and the arc welding current is 190A,the laser power is 6kW,the distance between light wires is 3mm,the defocus quantity is-4mm,and the welding speed is 90cm/min.The MIG swing welding is applied to cosmetic welding.The welding current is 240A,the swing pendulum length is 4mm,the swing amplitude is 6mm,and the welding speed is 20cm/min.The welding seam with full penetration and the appearance of the cover surface is obtained.Compared with the traditional MIG multi-channel multi-channel welding efficiency,the efficiency is increased by 263%.At last,the micro hardness and tensile strength of the joint were measured.The hardness of the welded joint is less than that of the base metal.the hardness of the base metal is 110HV.The hardness of the weld zone in the laser zone is 81HV.The hardness of the weld zone in the arc zone is 75HV.The hardness of the cover area is 67HV.The average tensile strength of the base metal is 475MPa.The extension rate is 14.45%.The fracture form is ductile fracture.The tensile strength of the cover area is 260MPa?The extension rate is 4.54%.When the welding speed is 90cm/min,the tensile strength of bottom welding is the highest.The average tensile strength is 317MPa,which is 66.7%of the base metal.The extension rate is 3.71%.The fracture form is ductile-brittle fracture.The arc region has a better toughness than the laser zone.The heat affected zone in the laser zone of the weld is dendrite,and the narrow width is about 77?m.The microstructure of the fusion zone is not uniform,the width of the side near the heat affected zone is very narrow,and the grain is a fine equiaxed crystal.The other side near the weld zone is a columnar dendrite,which grows towards the center of the weld and grows opposite to the weld.The microstructure of the weld zone is equiaxed crystal.With the increase of the welding speed,the grain size of the weld heat affected zone,the fusion zone and the weld zone decreased.The grain size of the heat affected zone decreases and the width is narrower.The number of precipitates in grain boundary and crystal decreases,and the size is smaller.There are similar structures in the arc region and the laser region,but the grain of the arc is larger.The heat affected zone of the arc zone is wider.The size of the grain in the weld is more uniform.From the laser region to the arc region,the content of Mg increases gradually and the Zn decreases gradually.The composition segregation occurs at the grain boundary,and the content of Mg and Zn increases.The content of Zn in the stoma of the process is much higher than that of the metallurgical pores.