A Structurally Based Viscosity Model for Oxide Melts
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RODUCTION
VISCOSITY is an important physical property of oxide melts since it plays a significant role in the fields of pyrometallurgy, ceramics, glassmaking, geological research, etc. For instance, in steelmaking, reliable viscosities are needed for good process control in (i) the blast furnace, (ii) for foaming in the BOS process, (iii) for the successful separation of metal and slag, and (iv) for the continuous casting process where the slag acts as a lubricant. Furthermore, viscosity is sometimes considered to be a reasonable measure of the slag structure since viscosity is very sensitive to changes in structure. The importance of the viscosity is reflected in the numerous models[1–10] which have been proposed for the estimation of the viscosities of molten oxide melts. However, the compositional ranges of these viscosity models tend to be limited. Good estimates of the viscosities can be obtained when applied to the specific slag systems, but good estimates cannot be obtained for all slag systems. For instance, the Riboud,[1] NPL,[3] and modified Iida model[6] provide reasonable estimates for mold fluxes,[11] but are less effective when applied to other slag systems. A structurally based viscosity model has been proposed in our previous articles.[12–17] The model provides good descriptions of the viscosity over wide ranges of composition and temperature. In the current study, the viscosity model is extended to slags containing Fe2O3 and P2O5. Furthermore, the model has been applied to viscosity
GUO-HUA ZHANG, Lecturer, and KUO-CHIH CHOU, Professor, are with the State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, Beijing, P.R. China, and also with the School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing. Contact e-mail: [email protected] KEN MILLS, Professor, is with the Department of Materials, Imperial College, London SW7 2AZ, U.K. Manuscript submitted April 12, 2013. METALLURGICAL AND MATERIALS TRANSACTIONS B
estimations of various industrial slag systems covering a vast compositional range, which are used in the following processes: the blast furnace, oxygen steelmaking, ladle refining, the continuous casting of steel, coal gasification, and electroslag remelting (ESR). The performance of the model in calculating viscosities for these systems will also be discussed.
II.
MODEL
Details of the model have been given elsewhere.[12–17] Only a brief description of the model will be given here. The temperature dependence of the viscosity is frequently represented by the Arrhenius equation: ln g ¼ ln A þ E=RT;
½1
where g is the viscosity, (dPas); A is the pre-exponential factor, (dPas); E is the activation energy (J/mol); R is the gas constant, 8.314 J/(mol K); and T is the absolute temperature, K. The model makes use of the temperature compensation effect which relates the preexponential factor (A) to the activation energy (E) as shown in Eq. [2]: ln A ¼ kðE 572516Þ 17:47:
½2
In order to maintain the self-consistency of the mo
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