| Laser welding has been widely applied in equipment manufacturing,aerospace,ship,automobile and so on due to the advantage of high power density,low heat input,wonderful welding efficiency.With the higher strategic demand for high service performance equipment,the research and application of high-power laser welding(usually greater than 5000W)for thick-wall and complicated structural component in the equipment is becoming increasingly urgent.However,compared with the low power laser welding,high-power laser welding is demanding on the welding conditions and the processing window is narrow,hence it's easy to get large thermal deformation,severe welding defects,the significant microstructure heterogeneity of weld appearance and poor mechanical properties.The weld appearance has a crucial effect on the quality and mechanical properties of the joint and is closely related to the dynamic behavior of molten pool in high-power laser welding.Additionally,the 316 L stainless steel is widely used in high service performance equipment as the advantage of strong corrosion resistance,excellent high temperature strength,good work hardening characteristics and weak magnetic in solid solution state.Therefore,this paper conducted the numerical simulation and experimental study on the correlation between the weld appearance and the dynamic behavior of molten pool in 316 L stainless steel high-power laser welding.As follows are the major achievements:Firstly,a numerical model describing the dynamic behavior of molten pool in highpower laser welding was established.In this model,the self-consistent hybrid heat source is adopted to deal with the laser heat input,the enthalpy porosity method was used to deal with the melting and solidification,the VOF method coupling with Level Set method was used to track the interface.Then the numerical simulation of the dynamic behavior of molten pool in high-power laser welding is achieved.Secondly,this paper studied the dynamic behavior of molten pool in 316 L stainless steel high-power laser welding through numerical simulation.And the three typical kinds of weld appearance in 316 L stainless steel high-power laser welding were found and summarized.In order to study the reason for the formation of different weld appearances,the differences in the dynamic behavior of molten pool with different weld appearance were studied and the reasons were analyzed to reveal the correlation between the weld appearance and the dynamic behavior of molten pool in 316 L stainless steel high-power laser welding.Finally,the paper carried out the experimental study on 316 L stainless steel highpower laser welding.The accuracy of the numerical model was verified and the prediction of weld appearance was realized by comparing the experimental results of the weld appearance and the dynamic behavior of molten pool with the simulated results in high-power laser welding.Besides,the process distribution of weld appearance in 316 L stainless steel high-power laser welding was studied to provide the reference for the control of the weld appearance in high-power laser welding. |
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