Effect of Ce2O3 on melting behavior of CaF2-CaO-Al2O3-MgO for electroslag remelting slag
Currently,the reduction of rare earth slag by Electroslag Remelting(ESR)represents an effective approach for incorporating rare earth elements.However,the addition of rare earth oxides will inevitably change the melting properties of the slag system,which in turn affects the smoothness of the ESR process and the quality of the rare earth steel.Based on the Ion and Molecule Coexistence Theory(IMCT),a thermodynamic model of the CaF2-CaO-Al2O3-MgO-Ce2O3 quinary slag has been established.From a thermodynamic perspective,the influence rule of each component in the slag on the activity of Ce2O3 has been analyzed.The melting points of slag systems with dif-ferent Ce2O3 contents and w((CaO))/w((Al2O3))(C/A ratios)were determined using the hemisphere method.In conjunction with SEM-EDS and XRD,the slag system's phase composition and microstructure were tested and ana-lyzed.The results show that an increase in the C/A,MgO,and Ce2O3 levels can boost the activity of Ce2O3 in the slag at a temperature of 1 873 K,with the order of influence being Ce2O3＞C/A＞MgO.When w((Ce2O3))≥18%,w((MgO))≥4%,and C/A≥1.1,the Ce element in the steel no longer burns out.As the addition of Ce2O3 increases from 0 to 24%,the slag melting point first decreases and then increases,and a small amount of Ce2O3 can promote a decrease in the melting point of the rare earth slag.However,excessive Ce2O3 will lead to the formation of many high-melting-point phases(2CeAlO3)in the slag,thereby increasing the melting point of the rare earth slag.As the C/A increases from 1.1 to 1.4,the slag melting point shows a decreasing trend.The primary reason for the decrease in the melting point of the rare earth slag is the reduction of high-melting-point phases.The equilibrium Ce content measured in the experiment differs only slightly from the theoretical calculation,and the trend of change is consistent.The slag-metal equilibrium tests confirmed that w((Ce2O3))of 18%to 20%can reduce Ce burnout,fur-ther proving that the thermodynamic calculation model and the range of the quinary slag obtained from this model are correct.The optimal slag to inhibit the burnout of rare earth elements is determined to be w((CaF2))/w((Al2O3))= 1.4,w((Ce2O3))= 18%-20%,w((MgO))= 4%-5%,and w((CaF2))= 50%-60%.This provides theo-retical guidance for the ESR of rare earth slag.
electroslag remelting slagCe2O3theory of coexistence of ions and moleculesCe burning lossmelt-ing point
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