Research On Electromagnetic Separation And Heat Transfer Characteristics Of Titanium-silicon Alloys

The preparation of high silicon titanium silicon alloy by metal thermal reduction of high titanium blast furnace slag is a potential method for treating slag accumulation,but the prepared alloy has the problems of narrow application range and low dosage.In order to broaden its application,this paper proposes to prepare silicon and titanium silicon alloys by electromagnetic directional solidification of high silicon titanium silicon alloy.In the process of electromagnetic directional solidification,it is found that the convection diffusion and temperature distribution of the melt have an important effect on the separation of primary Si and Ti-Si alloy in Ti-Si based alloys.This paper takes Ti-89 wt.%Si alloy melt as the research object of electromagnetic directional solidification.Based on the basic control equation of electromagnetic field,a two-dimensional axisymmetric finite element model of electromagnetic field-flow field-heat field coupling in the electromagnetic directional solidification process of alloy melt was established.The electromagnetic directional solidification process of Ti-89 wt.%Si alloy melt was simulated by COMSOL Multiphysics 5.4 commercial software.The effects of pulling-down rate(v),power(p),current frequency(f)and crucible size(d)on the separation of silicon phase and alloy were studied by numerical simulation.The simulation results showed that when the pulling-down rate was 10?m/s,the convective diffusion ability of the melt was strong,and the composition distribution of the melt was more uniform.Moreover,the cooling rate of the melt was the smallest,which provided favorable conditions for the absorption of silicon atoms or clusters at the solidification front during crystal growth.With the increased of power from 3.8 kW to 5.4 kW,the backflow phenomenon in the melt surface was weakened.When the power was 5.4 kW,the electromagnetic stirring effect of the melt was the strongest,which was beneficial to the enrichment of silicon phase.When the frequency of the high-frequency induction furnace increased from 15k Hz to 50 k Hz,the rate of axial rotation of the melt decreased,and due to the skin effect,the axial downward rotation flow in the melt transforms into the axial upward and downward rotation flow.When the current frequency was 15 k Hz,the electromagnetic stirring effect generated in the melt was the best,the average flow rate of the melt reaches the maximum,and the silicon atoms were enriched to the solidification front,which was conducive to the nucleation and growth of primary silicon.With the increase of crucible size,the flow rate in the melt increased,and the electromagnetic stirring effect improved.However,due to the skin effect,the axial rotation flow mode in the melt changes.The electromagnetic separation process was studied by experiments,and the experimental results showed that higher pulling-down rate(v)was not conducive to the separation and enrichment of primary silicon.When the drawing speed was 50?m/s,the Si+Ti Si₂phase in the silicon enrichment layer gradually increased,resulting in the enrichment effect of silicon was weakened,and the content was reduced to 88.04%.With the increase of power,the number of Ti-Si eutectic alloy phases in the silicon enrichment layer decreased slightly during the melt solidification.When the power was 5.4 kW,the silicon content in the silicon enrichment layer reached 95.84%,and the enrichment effect was the best at this time.