| Compared with single laser welding and single arc welding, laser+GMAW hybrid welding shows great advantages in both welding efficiency and weld quality. Through synergy effect, the hybrid welding can realize the process performance of "1+1>2". The dynamics of weld pool and keyhole in laser+GMAW hybrid welding play a dominant role in affecting the weld quality. Therefore, developing a numerical model and simulating the dynamics of keyhole and welding pool is becoming more and more urgent and important for getting deep insight into the process mechanism research and optimizing the process parameters in hybrid welding.Based on the process characteristics of hybrid welding, the thermal and mechanical effects of laser, gas metal arc and droplets are analyzed. Through considering the effects of laser power, arc power, droplet heat and recoil pressure, as well as surface tension, arc pressure, gravity, buoyancy, different treatment for laser keyhole, gas metal arc and droplets are made, respectively. Taking the interaction between laser and arc into account, a model for laser+GMAW hybrid welding is established.By means of 2nd-development of ANSYS FLUENT, the finite volume method (FVM) is used for the discretization and the volume of fluid (VOF) method is used to track the keyhole wall. The PISO algorithm is used for the solution. The formation, growth and maintenance of keyhole are numerically simulated, and the dynamic variation of keyhole is analyzed. The geometric characteristics of weld pool are depicted and the fluid flow and thermal field in hybrid weld pool are quantitatively calculated. Through depicting the process of keyhole collapse, the reason and the escape track of pore in weld pool are analyzed. The model shows good agreement with the experiment data in the fluid flow and fusion line. |
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