Equilibrium interphase distribution of chromium depending upon stainless steel slag temperature and basicity

Abstract

With the aim of studying the occurrence of chromium reduction during argon-oxygen refining using boron oxide as a flux, thermodynamic modelling of the equilibrium interfacial distribution of chromium between slag of the oxide system CaO–SiO₂–(3–6%)B₂O₃–12%Cr₂O₃–3%Al₂O₃–8%MgO in the range of basicity 1.0–2.5 and metal depending on temperature, boron oxide content, and basicity is performed. Modelling results are shown as diagrams of the dependence of the equilibrium interphase distribution of chromium on slag composition at 1600 and 1700 °C. It is found that an increase in slag basicity from 1.0 to 2.5 at 1600 and 1700 °C leads in the range of boron oxide content studied to a decrease in the interfacial distribution coefficient of chromium from 60.0 · 10⁻³ to 1.5 · 10⁻³ and as a result an increase in the degree of chromium reduction from 91 to 99.5%. An increase in metal temperature and boron oxide content have little effect on chromium reduction. The influence of basicity of the slags studied on the chromium reduction process may be qualitatively explained from the perspective of phases formed within slags and thermodynamics of chromium reduction reactions with aluminum and silicon. Experimental studies confirm results of thermodynamic modeling.