Numerical Simulation Of Laser Oscillating Welding Of Aluminum Alloy

High frequency oscillating of laser beam could influence the temperature distribution and melt flow in molten pool of laser welding, which was in favor of the improving of weld morphologies and the avoiding of metallurgical defects. However, the research about laser oscillating welding is few, and no researches have been addressed on its numerical simulation. In this study, the effects of oscillating parameters on temperature field and melt flow in the molten pool of laser oscillating welding of AA6061 aluminum alloy were studied by means of numerical simulation. The main findings are listed as follows.Based on the theory of computational fluid dynamics, thermal transfer mode of keyhole and energy distribution of oscillating laser beam, a numerical model of AA6061 of oscillating laser welding had been established. By comparing the data of the size of the weld fusion line, it was found that the model had a high simulation accuracy and the maximum error did not exceed to 14%.Comparing to molten pool of no-oscillatory laser welding, the peak temperature of the molten pool was reduced by high frequency oscillating of laser beam and the rise rate of temperature of molten pool was dropped about 30%. Besides, high frequency oscillating of laser beam could reduce the longitudinal temperature gradients and hardly change the transverse temperature gradients, therefore increased the uniformity of temperature distribution of molten pool. In the case of given typical parameters, the peak temperature decreased linearly from 5000 K to 3873 K as the oscillation frequency was increased from 0Hz to 200 Hz. Relatively speaking, the influence of the oscillation amplitude on the peak temperature of the molten pool was more pronounced. For instance, when it increased from 0mm to 2mm, the peak temperature dropped to 2052 K from 5000 K.Oscillation of the laser beam could enhance the vortex velocity and the convection velocity of the molten pool greatly. The vortex centers of transverse and cycle oscillatory scanning laser welding were increased to 2 and 3 from 1 when laser beam did not oscillate. In the case of given parameters, the maximum vortex velocity of transverse oscillation increased form 0.019m/s of no-oscillating to 0.086m/s and the maximum convection velocity increased from 0.0089m/s of no-oscillating to 0.023m/s of transverse oscillation. Secondly, the increases of oscillating frequency and amplitude could both enhance the vortex velocity and the convection velocity. When the frequency changed from 0Hz to 200 Hz, the maximum vortex velocity of cycle oscillatory laser welding enhanced linearly from 0.019m/s to 0.18m/s, which was nearly 10 times to no-oscillatory laser welding, and the maximum convection velocity increased from 0.0089m/s linearly to 0.156m/s. When the amplitude changed from 0mm to 2.0mm, the maximum vortex velocity increased to 0.12m/s, which was 12.1 times faster than that of no-oscillatory laser welding.