Numerical Simulation And Experiment Study On Flow Behavior Of Molten Pool In Dual-beam Laser Welding

Laser welding technology is widely used in the field of material processing.Due to the advantages of small heat-affected zone,high welding accuracy and automation,and fast welding speed,it makes a great progress in automobile manufacturing,aerospace,deep water and other fields.However,in practical applications,it is often restricted due to problems such as high assembly precision requirements and sharp fluctuations in the keyhole and molten pool during welding.The previous studies indicated that dual-beam laser welding can effectively solve the above problems,for example,by adjusting the energy ratio,beam distance and arrangement of the two beams,which greatly improves the flexibility of the welding process while ensuring the welding efficiency.However,due to the interaction between the two beams in the welding process,the flow behavior of the molten pool and the morphology of the keyholes are more complex.At present,the research on the flow behavior of molten pool in dual-beam laser welding is not comprehensive.Experimental research cannot obtain all the information on the behavior of the molten pool and keyhole during the welding process,and there are only few numerical simulation studies.Therefore,it cannot effectively guide the dual-beam laser welding process and quality control.Aiming at the mentioned situation,this paper studied the flow behavior of the molten pool during the double-beam laser welding of stainless steel through a combination of experiment and numerical simulation,and analyzed the influence of the beam distance on the double-beam laser welding process.The results are as follows:(1)The numerical model of dual-beam laser welding is established,in which the adaptive heat source model takes into account the influence of real-time change of the depth of the keyholes on the welding heat input under the simultaneous work of two beams,and at the same time the evolution process of the dual-beam laser welding keyhole wall was taken into account,by the CLSVOF method combining the method of VOF and LEVEL SET.So the free interface is accurately tracked,thereby the recoil pressure and surface tension were accurately applied at the keyhole wall,which lays the foundation for the study of the molten pool flow behavior of double-beam laser welding.(2)The dual-beam energy field analysis and the numerical simulation of steel dual-beam laser welding under different beam distance were carried out.It was found that the disturbance in the molten pool between two keyholes exists along the depth of the keyhole;the beam distance would significantly affect the shape and stability of the molten pool and keyholes,the molten pool temperature distribution and the flow behavior during dual-beam laser welding process.And the influence of beam distance on the dual-beam laser welding process was summarized.(3)The experiment of steel dual-beam laser welding under different beam distance was carried out.The effects of beam distance on the flow behavior and stability of the molten pool were analyzed by high-speed cameras under different positions,then combined with the observation of the weld morphology,the correlation among the beam distance,molten pool flow behavior and the weld morphology was established.