The Investigation On The “∞” Shaped Laser Scanning Welding Of Aluminum Alloy In High-Speed Train By Numerical Simulation

Aluminum alloy was widely used in the manufacture of highspeed trains as a kind of lightweight alloy material.However,in the laser welding process,low-boiling point elements such as Mg and Zn contained in aluminum alloy were easily evaporated,resulting in the formation of weld porosity defects.The mechanical properties of the joint were seriously affected.“∞” shaped laser scanning welding of 6061 aluminum alloy was deeply studied to reduce the porosity defects of aluminum alloy laser welding in this article.The effect of “∞” shaped laser scanning welding on weld porosity defects was analyzed.The inhibition mechanism of “∞” shaped laser scanning welding on weld porosity defects was revealed.The relationship between the characteristics of energy distribution and behavior of the molten pool and the forming characteristics of weld was obtained.The main work of the article was given as follows:(1)Welding experiments of conventional laser welding and “∞”shaped laser scanning welding of aluminum alloy were carried out by establishing the laser welding experiment platform.The inhibition effect of “∞” shaped laser scanning welding on weld porosity defects was analyzed.The influence law of scanning amplitude and scanning frequency on weld porosity defects was obtained.The results showed that the “∞”shaped laser scanning welding was beneficial to inhibit the formation of weld porosity defects.The inhibition effect on weld porosity defects of increasing scanning amplitude and scanning frequency was obvious.(2)The dynamics models of molten pool in conventional laser welding and “∞” shaped laser scanning welding were established.Based on the results of numerical simulation,the process of conventional laser welding and the “∞” shaped laser scanning welding process under different scanning amplitudes and scanning frequencies were deeply studied.The behavior characteristics of temperature field and flow field in the molten pool were analyzed.The inhibition mechanism of “∞” shaped laser scanning welding on weld porosity defects was revealed.It was found that the molten metal of molten pool in the “∞” shaped laser scanning welding exhibited the characteristic of multi-eddy current,which was beneficial to reduce the weld porosity defects.With the increase of scanning amplitude and scanning frequency,the stability of molten pool was improved,which created the condition for improving the quality of weld formation.(3)The energy distribution characteristics of molten pool in the conventional laser welding and “∞” shaped laser scanning welding were analyzed.The influence law of different scanning amplitudes and scanning frequencies on the energy distribution in the molten pool was studied.The relationship between the characteristics of energy distribution and behavior of the molten pool and the forming characteristics of weld was obtained.It was found that the variation of the energy distribution of the molten pool was consistent with the variation of the molten pool behavior and the forming characteristics of weld under different scanning amplitudes and scanning frequencies.Increasing the scanning amplitude or scanning frequency within a certain range could make the energy distribution of molten pool uniform,which provided the conditions for stable molten pool behavior and good weld formation.