Numerical Analysis On Arc And Weld Pool Dynamic Behavoir By Rotating Laser +GMAW Hybrid Welding Of Aluminum Alloy

Rotating laser + GMAW hybrid welding is one of the ideal choice to effectively make up for the shortcomings of traditional hybrid welding,improve the stirring effect of the laser on the molten pool,and expand the range of laser heat source.Defects are effectively suppressed,such as pores,humps,undercuts,cracks,etc..At the same time,it improve the quality of the joint.However,the laser rotation makes the physical characteristics of the heat source,the dynamic behavior of the keyholes and the molten pool more complicated than the conventional hybrid welding.Rotating laser hybrid welding process optimization is relatively difficult,which in turn affects the reliability and stability of the welding quality.At present,researchers mainly focus on experimental research,but it is difficult to explain the internal mechanism.Therefore,in this paper,using numerical simulation to study the rotating laser +GMAW hybrid welding.And analyze the effect of rotating laser on the arc plasma dynamic behavior,dynamic changes of small holes and fluid flow in molten pool.It will lay a solid foundation for the optimization and practical application of aluminum alloy rotating laser +GMAW hybrid welding process.Dynamic behavior and the molten pool fluid flow of the rotating laser + GMAW hybrid welding is very complicated.At the first step of the research,the theory of heat transfer,optics,electromagnetic and fluid dynamics are all taken into account.In this paper,the numerical analysis model of the arc dynamic behavior of the rotating laser + GMAW and the numerical analysis model of the fluid flow in the molten pool has been established.The dynamic behavior of the arc and the fluid flow in the molten pool are simulated separately,and the thermal characteristics of the molten pool are analyzed based on the arc simulation results.Based on the arc dynamic numerical model of rotating laser hybrid welding,the effects of laser on the temperature,flow velocity,pressure,potential distribution,different joints,different rotation radii and different frequencies are studied.The results show that the maximum arc temperature corresponding to the four positions A,B,C,and D is 14590 K,14593K,14589 K,and 14598 K respectively,due to the continuous change of the laser position.The range of the electric potential is very small;as the laser rotation frequency increases,the laser action time on a certain position of the workpiece decreases,however,the area of the laser action area becomes larger,the metal vapor concentration increases,resulting in an increase in arc temperature.When the rotation frequency is 10 Hz,20Hz,and 30 Hz,the maximum arc temperature is 13809 K,14593K,and 14963 K,respectively,meanwhile the flow velocity and pressure of the arc plasma increase.As the radius of rotation increases,the laser has a wider range of action,but the laser rotation speed becomes faster.So the action time of the laser on the workpiece is reduced,the metal vapor concentration is reduced,which causes the arc temperature to decrease.The maximum temperature is 14890 K,14590K,and13876 K when the radius of rotation is 0.5mm,1.0mm,and 1.5mm.The flow velocity and pressure of the arc plasma are also corresponding reduction.In T joints,the maximum temperature of the arc is 13562 K at a rotation frequency of 0 Hz.While at 20 Hz,the maximum temperature of the arc is reduced to 13059 K,which is about 1000 K lower than that of the butt joint.In the T joint,the arc space is narrower,the arc deviates to the left of the welding wire axis.So the temperature,velocity,and the pressure decrease.Based on the numerical model of fluid flow in the molten pool of rotating laser welding,the effect of laser on the temperature and velocity of the fluid in the molten pool at different joints and different frequencies is studied.The results show that in the butt joint,the surface of the molten pool fluctuates violently,and a wavy weld is formed at the bottom of the molten pool.The size of the keyholes is constantly changing.As the rotation frequency increases from 0 Hz to 20 Hz,the maximum keyhole diameter on the upper surface of the molten pool increases from 2.1 mm to 3.4 mm,and the fluid flow velocity also increases from 1.9 m / s to3.5 m/s.In the T joint,the influence on the fluid movement in the molten pool is enhanced,and the fluctuation degree on the upper surface of the molten pool is low.But the size of the keyholes in the cross section becomes larger,the maximum diameter and depth are 1.6mm and 2.8mm.As the rotation frequency increases from 0Hz to 20 Hz,the flow velocity is increased from 2.5m/s to 4.5m/s,and the maximum diameter and depth are 1.6mm and 2.8mm.Because the laser constantly stirs the molten pool,the fluid flow velocity in the molten pool is increased,and the bubbles in the molten pool are easy merging with keyholes.It is conducive to the escape of air bubbles and suppresses the occurrence of pore defects.While it will improve the spreadability of liquid metal and conducive to suppressing the occurrence of undercut defects.