Research On Process Characteristics And Optomization Of A7N01 Aluminum Alloy Laser-MIG Hybrid Welding

A7N01 aluminum alloy is Al-Zn-Mg series high-strength aluminum alloy with low density and high strength.Loss is conducive to promoting the realization of the "dual carbon" goal.The traditional welding method has large heat input and low welding efficiency.The laser-arc hybrid welding method combines the advantages of laser welding and arc welding,and has the advantages of fast welding speed,small heat input,and large weld depth-to-width ratio.Ideal method for aluminum alloy welding.In recent years,with the continuous development of technology,the maximum output power of fiber lasers and disk lasers can be as high as 100,000 watts under the premise of ensuring beam quality,which provides realistic and feasible conditions for high-power laser welding.Therefore,studying the influence of laser power on the characteristics of laser-MIG hybrid welding of aluminum alloys can provide a theoretical basis for the research of high-power laser hybrid welding technology.Optimizing the process parameters of laser-MIG hybrid welding is of great significance to improve the quality of weld formation and welding efficiency.In this paper,high-speed camera and NI data acquisition system are used to study the effect of laser power on welding characteristics such as arc parameters,droplet transfer behavior,and keyhole behavior in the process of aluminum alloy laser-MIG hybrid welding.As the laser power increases from 4 k W to 5.5 k W,the compression effect of the laser on the arc and the thermal radiation effect of the metal vapor on the electrode wire are enhanced,resulting in a decrease in the peak current of the arc,an increase in the peak voltage,and an increase in the arc length.When the power is greater than 4 k W,the short-circuit transition of the droplet can be avoided,but when the laser power is increased to 5.5 k W,the metal vapor force plays a dominant role in hindering the droplet transition,making the droplet transition difficult,and the transition form of two pulses and one droplet appears.,reduce the droplet transition stability;the effect of metal vapor on the keyhole wall is the main reason for the generation of spatter above the keyhole wall during the hybrid welding process.The weld penetration obtained during the welding process is stable,and the weld porosity is smaller.Appropriate laser power is the key to obtaining a stable welding process and high-quality welds.The response surface method was used to model and analyze the effect of process parameters on the porosity of the butt weld of 12 mm thick A7N01 aluminum alloy thick plate.speed.As the laser power or wire feeding speed increases,the porosity of the weld increases.Taking the welding seam porosity <3 % as the optimization target,the optimal parameters predicted by the model are selected as follows: the laser power is 4.6 k W,the wire feeding speed is 7.2 m/min,and the welding speed is 18.48 mm/s.The obtained welding seam porosity and the predicted value fitted well.On the basis of the bottoming weld,the appropriate capping parameters were selected to obtain a well-formed butt joint.In addition,three-pass welded joints were obtained by low-power laser-MIG hybrid welding.Compared with the three-pass welded joint,the heat input of the two-pass welded joint with high-power laser priming is reduced by 43.83 %,and the welding efficiency is increased by49.56 %.The distribution of microstructure in A7N01 aluminum alloy laser-MIG composite welded joint is uneven,the weld zone is equiaxed grain,the fusion zone is columnar grain and fine equiaxed grain,and the structure of heat affected zone is similar to the base metal,both of which are fibrous structure.The microhardness distribution in the welded joint is not uniform,the hardness of the base metal is the highest,followed by the heat-affected zone,and the hardness of the weld zone is the lowest.The hardness of the weld zone of the two-pass welding joint is higher than that of the three-pass welding joint,and the width of the heat-affected zone is only 1/2 of the width of the heat-affected zone of the three-pass welding,but there is no significant difference in the hardness of the two-pass welding.The tensile fractures of the two-pass and three-pass welded joints occurred in the weld zone,and the average tensile strengths were 244 MPa and 262 MPa,which reached 69.71 % and74.86 % of the base metal,respectively.