首页|Effect of slag composition on kinetic behavior of deep deoxidation of 5 wt.％Si high-silicon austenitic stainless steel
Effect of slag composition on kinetic behavior of deep deoxidation of 5 wt.％Si high-silicon austenitic stainless steel
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Based on a thermodynamic study of 5 wt.％Si high-silicon austenitic stainless steel(SS-5Si)smelting using CaF2-CaO-Al2O3-MgO-SiO2 slag to obtain a low oxygen content of less than 10 x 10-4 wt.％,a kinetic mass transfer model for deep deoxidation was established through laboratory studies,and the effects of slag components and temperature on deoxidation during the slag-steel reaction process of SS-5Si were systematically studied.The experimental data verified the accuracy of the model predictions.The results showed that the final oxygen content in the steel at 1873 K was mainly controlled by the oxygen content derived from the activity of SiO2 regulated by the[Si]-[O]equilibrium reaction in the slag system;in particular,when the slag basicity R(R=w(CaO)/w(SiO2),where w(CaO)and w(SiO2)are the contents of CaO and SiO2 in the slag,respectively)is 3,the A12O3 content in the slag needs to be less than 2.7％.The mass transfer rate equation for the kinetics of the deoxidation reaction revealed that the mass transfer of oxygen in the liquid metal is the rate-controlling step under different slag conditions at 1873 K,and the oxygen transfer coefficient kom increases with increasing the slag basicity from 4.0 × 10-6 m s-1(R=1)to 4.3 × 10-5 m s-1(R=3).kOm values at R=2 and R=3 are almost the same,indicating that high slag basicity has little effect.The integral of the mass transfer rate equation for the deoxidation reaction of SS-5Si under different slag conditions is obtained.The total oxygen content of the molten steel decreases with increasing basicity from an initial content of 22 × 10-4 to 3.2 × 10-4 wt.％(R=3),consistent with the change in kO,m with slag basicity.At R=2,the slag-steel reaction takes 15 min to reach equilibrium(w[O]=5.5 × 10-4 wt.％),whereas at R=3,the slag-steel reaction takes 30 min to reach equilibrium(w[O]=3.2 × 10-4 wt.％).Considering the depth of deoxidation and reaction time of SS-5Si smelting,it is recommended the slag basicity be controlled at approximately 2.Similarly,the effect of temperature on the deep deoxidation of SS-5Si was studied.
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