Numerical Simulation And Experimental Study Of High Power Laser Welding Under Side Gas Flow

Laser welding has the advantages of large ratio between weld depth and width,small heat impact zone,fast welding speed,and suitable for flexible manufacturing.It is widely used in railway construction,automotive manufacturing,aerospace engineering and other industries.Compared with low-power laser welding,high-power laser welding(greater than 5 k W)has a greater energy density,and can achieve highefficiency welding of medium-thick components(greater than 4 mm),which has great development potential and research significance.The increase of laser power in high power laser welding makes welding quality and mechanical properties more difficult to control.Compared to low power laser welding,welding defects are more likely to occur in high power laser welding process.The side gas flow can change the flow behavior of liquid metal in the melting pool and the area of keyhole opening,which can be used to improve the quality of high-power laser welding.In this paper,the mechanism of heat transfer and mass transfer during the three-phase transition in high power laser welding process under the effect of side gas flow is studied by numerical simulation and experiments study.Analyzing the mechanism of the influence of the side gas flow on the high power laser welding process is of great significance for obtaining good welding quality.Numerical simulation and experimental study on the correlation between welding quality and dynamic behavior of 316 L stainless steel laser welding under the effect of side gas flow are carried out.The results are as follows:(1)A mathematical model of high power laser welding under side gas flow is established.The 3D combined heat source model is adapted according to the keyhole depth obtained in real time in the simulation,and the incident laser energy attenuation effect under the action of particles in the plume is considered in the model,and the connection between the laser input energy and the height of the steam feather is established.At the same time,the improved PLIC-VOF method is used to realize the real-time tracking of the free interface of the keyhole,so as to realize the accurate calculation of the recoil pressure.(2)The numerical simulation of the 316 L stainless steel high power laser welding under the side gas flow was carried out,and it was found that the changes of the process parameters of the side gas flow will affect the dynamic behavior of the welding pool,the morphology characteristics of the metal vapor/plasma,the internal temperature of the melting pool,the morphology of the keyhole,and its vibration.Then the mechanism of the influence of the side gas flow on the high power laser welding process is revealed.(3)The experiment study of the influence of side gas flow on high power laser welding process of 316 L stainless steel was carried out.Changing the flow rate,transverse distance and nozzle height of the side gas flow,the influence of the weld morphology and mechanical properties of the welding joint were observed and analyzed.Finally,the optimal process parameters of side gas flow were obtained.