| Titanium and its alloy are with good properties such as low density, high strength, high heat resistance and high corrosion resistance. At present, the main procedure to prepare ferrous titanium is remelting method, which takes titanium scraps as raw material. With high cost, this method is difficult to apply in China. In recent years, aluminothermic reduction method is widely used to prepare ferrous titanium. However, this method has many disadvantages such as high oxygen and impurity content, low reduction rate and so on, which severely limits the application of aluminothermic reduction method. Aiming at the disadvantages such as high oxygen content and difficulties in judge the Al-0 balance of the ferrous titanium, this essay studied the aluminothermic reduction process of ferrous titanium production by thermodynamic and experimental study based on coexistence theory and SHS method. In detail:Firstly, based on ion and molecule coexistence theory, a thermodynamic model for calculating the mass action concentrations of structural units in different temperatures and contents of CaO-Al2O3-TiO2 slags has been developed. By using the calculated mass action concentration, a viscosity estimation model for calculating the viscosity of CaO-Al2O3-TiO2 slags based on measured viscosity and the Arrhenius equation has also been developed, indicating the relationship between mass action concentration and the viscosity. The result showed that the calculated viscosities shows a reliable agreement with the measured ones, especially in the low viscosity area(<1Pa·s), indicating the fact that the coexistence theory can reflect the actual constructions of molten slags.Secondly, based on molten metal coexistence theory, models for calculating the mass action concentration of structural units in Ti-O, Ti-Al-O, Ti-Fe-O, Ti-Al-O-Fe melts has also been developed. According to the calculated results, a thermodynamic balance system was established based on the relationship between the Gibbs free energy and the Ti-Al-O-Fe melts composition. The results indicate:The aluminothermic reduction process is a substep reaction process; the restrictive factors are the TiO-Ti3O and TiO-Ti converting reaction. In Ti-O melt the balance O content is 12% according to the aluminothermic reduction. However, when Al dissolved in the melts, the balanced O content can decline from 7% to 4% with the Al content increased from 5% to 25%. And a similar coefficient action was also found when Fe dissolved in the melt; the balanced O content can also decline from 9% to 4% with the Fe content increased from 10% to 50%. The coefficient factor of mixture of Fe-Al was also studied in this essay. The results showed that in a Ti-Al-O-Fe melt with 1%Al-25%Fe content, the balanced O content can reach 7%, otherwise, in a 25%Al-25%Fe melt, the balanced O content can reach less than 1%, indicating the deoxidation reaction can reach a relatively sufficient state.Thirdly, according to the thermodynamic calculated result, using rutile, ferric oxide and other additives as raw material, the ferrous titanium was prepared by SHS method, the results indicated:KClO3 can accelerate slag-metal separation, but it can also increase the the Al content. When the additive amount of Al was higher than the calculated value, the Al content increased obviously from 8% to 10%, indicating that the extra additive Al showed a kind of metallicity, rather than reducibility. The additive of CaO can also accelerate slag-metal separation, but an overmuch additive of CaO can lead high heat absorption. |
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