| The low-frequency oscillating laser welding technology is improved on the basis of traditional laser welding technology.Although the traditional laser welding technology has been developed for nearly thirty years,b ecause of the uniqueness of aluminum alloy,there are still many problems in the application of laser welding on aluminum and its alloys.For example,the welding process is not smooth,the defects(weld holes,cracks,collapses)are common,and the strength of the joint is not ideal.In contrast,the aluminum alloy weld produced by the oscillating laser welding is well formed and the comprehensive performance is improved.Moreover,on the basis of maintaining the advantages of narrow heat affected zone,co ncentrated energy density and small deformation,the oscillation laser welding technology increase s the area of energy,and reduces the requirement of the laser on the clamping precision of the workpiece.To make welding technology meet the needs of modern industry,welding is more reliable.However,the technology of the oscillating laser welding has just started soon,and the technology is still not mature enough.At present,there are f ew simulation and Experimental research on the oscillation laser welding.Therefore,the numerical simulation and experimental study on 2mm 7075-T6 aluminum alloy sheet are carried out in this paper.First,the heat transfer model of 7075-T6 aluminum alloy low-frequency oscillation laser welding is established.The welding process was simulated by ANSYS software and the welding temperature field was obtained.The temperature field obtained by conventional laser welding and oscillation welding at the same laser power and welding speed is compared.It is found that the peak te mperature of the latter is lower than that of the former.Besides the characteristics of the peak temperature change with time of the former are that it continuous rise until getting the quasi-steady-state peak temperature,but that of the latter are that it regularly decreases by a certain value and then continues to rise.When the quasi-steady state reaches,the peak temperature is also stable.In addition,the heating rate of the latter is also lower than the former.Subsequently,the effects of laser o scillation frequency,oscillation amplitude,laser power and welding speed on the welding temperature distribution were studied,and the appropriate welding process parameter range was determined.Secondly,the low-frequency oscillating laser butt welding experiment of 7075-T6 aluminum alloy was carried out.The effect of Ar gas flow,laser oscillation frequency,oscillation amplitude,laser power and welding speed on weld formation was studied in depth.Under the condition of controlling the other process parameters unchanged,the laser power is 1500 W,the welding speed is 1400mm/min,the laser oscillation frequency is 10 Hz,the oscillation amplitude is 0.5mm,the weld forming is the best.The tensile strength test based on orthogonal test was carried out,and the optimum combination of process parameters was obtained.The joint strength of the welded joint under the combination of the parameters was 369.85 MPa.The metallographic microstructure of welds obtained by conventional laser welding and oscillating laser welding with the same laser power and welding speed were compared and observed.The grain of the weld zone is a fine equiaxed grain,and the grain of the metallographic structure in the fusion region is also small,and the grain in the former fusion region grows along the direction of the fusion line.The direction of grain growth in the fusion line region is not uniform,and the grain is more refined than the former.Finally,the simulated weld pool width and the profile of fusion line profile are basically consistent with the experimental results.The correctness of the lowfrequency oscillation laser heat transfer model established in this paper is verified. |
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