The Combined Effects Of Magnetic Field And Active Agent On The Morphology Of Molten Pool

It is difficult to use the experimental method to test the molten pool,because the pool is small, the temperature is high, and the experimental conditions are limited. Numerical simulation method can provide complete temperature field, flow field and other information for welding process, it can help to understand the welding process and realize the control of the welding process. In order to study the molten pool behaviors under the combined effects of magnetic field and active agent, the paper established a three dimensional transient mathematical model for TIG welding of magnesium alloy under the action of a moving heat source. The processing method of source terms, boundary conditions, mesh method and thermo-physical performance parameters of material were given. Using fluent software and its secondary development functions, temperature field and flow field of magnesium alloy molten pool were simulated under the effects of single magnetic field, single active agent and the combined effects of magnetic field and active agent respectively. Then use experiments verified the accuracy of simulation results.The simulation results showed that under the effects of magnetic field the liquid metal in the molten pool was a directional rotation movement. The rotation direction was related to the magnetic field direction. The temperature field and flow field of the molten pool were asymmetric distribution. Under the effects of active agent the liquid metal in the molten pool flowed from the edge of the molten pool to the center of the molten pool, lead to the high temperature liquid metal scoured the bottom of the molten pool and increased the penetration. Under the combined effects of direct current magnetic field and active agent, the liquid metal in the molten pool was a spiral downward movement. When the magnetic induction intensity reached 0.04 T, the liquid metal was changed into a directional rotation movement by a spiral downward movement. With the increase of the magnetic induction intensity, the maximum temperature of the molten pool decreased, the maximum speed increased, the penetration decreased and the weld width increased. Under the combined effects of alternate magnetic field and active agent, the liquid metal in the molten pool was a periodic and intermittent movement. The fluid flow velocity was high during the magnetic field,the fluid flow velocity was low during the period of magnetic field. Compared to the direct current magnetic field, the asymmetric degree of temperature field and flow field was decreased under the alternate magnetic field.The weld morphology obtained by the actual welding experiment was in good agreement with numerical simulation results, which showed that the model established in this paper was reasonable and could reflected the temperature distribution in the welding process. Tracer atom experiment results and the simulation results didn’t match. So it couldn’t verify the flow patterns of the molten pool and requires further study.