| As a relatively new welding method,double-pulse MIG welding can realize stable,continuous and reliable heat input to thin aluminum alloy due to its unique current adjustment method,which can significantly improve welding quality and efficiency.However,due to the characteristics of aluminum alloy materials that are more sensitive to welding pores,the problem of welding pore defects has been difficult to solve.In this project,double-pulse MIG welding butt test of 6082 aluminum alloy sheet with a thickness of 3mm is carried out to analyze the influence of welding heat input,arc behavior,and droplet transfer on the formation of pores,and to optimize the welding process for the purpose of suppressing the formation of pores.The main contents of the research are as follows:1)Through experiments and simulations,the number,size and distribution of pores near the surface and cross section of the weld under different welding heat input are analyzed.The influence of the inherent melting point temperature of the aluminum alloy sheet and the temperature difference of the molten pool on the formation of pores is studied,and the optimal heat input interval for restraining the formation of pores is given.2)Observe the arc behavior of single-pulse MIG welding and double-pulse MIG welding at different stages through comparative experiments,and analyze the effect of the difference between the two on the formation of pores.In the double-pulse MIG welding process,due to the blessing of the strong and weak pulse groups and the stable arc shape,the bubble escape speed is accelerated and the molten pool is effectively protected,reducing the entry of external impurities.Therefore,its porosity formation rate is lower than that of single pulse MIG welding.3)Changes in welding current,welding voltage and other parameters during the welding process will cause the transition of the droplet.Different forms of droplet transition will have different effects on the final formation of stomata.Multi-pulse one drop and one-pulse multiple drops will cause severe hydrogen absorption and large splashes of the molten droplets,resulting in higher porosity,and droplet transitions in one pulse.The bottom weld has the smallest porosity.4)Finally,an orthogonal experiment was carried out with the purpose of optimizing parameters to suppress the formation of pores,and the influence of four factors(strong pulse average current,weak pulse average current,welding speed,welding position)on the formation of pores in double pulse MIG welding of aluminum alloy Through the analysis of the range of the test results,the main and secondary relationships of the influence of these four factors on stomatal formation were obtained.Finally,the optimal process parameters are determined as the average current of strong pulse is 120A,the average current of weak pulse is 75 A,the welding speed is 500mm/min,and the welding position is flat welding.The weld seam has beautiful fish scales,the welding process is stable,the effect of suppressing pores is the best,and the repeatability is strong.Figure[57]Table[13]Reference[80]... |
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