The main diluent for chromium-containing slags is CaF2. However, fluorspar disadvantages make it necessary to search for a replacement. As a substitute, boron oxide allows to improve slag physical properties and environmental situation. The paper presents the experimental study results of the chemical composition and temperature influence on viscosity of slags of CaO–SiO2–Cr2O3 system containing 8% MgO, 3% Al2O3 and 6% B2O3. It was found that a slag free of chromium oxide with basicity of 1.0 has a sufficiently high fluidity of 0.2–0.6 Pa·s in a wide temperature range of 1200–1350°C, due to high concentration of low-melting phases, reaching 22%, and only 11 % high-melting. A slag with 18% Cr2O3 and the same basicity retains a low viscosity of 0.1–1.0 Pa·s but at higher temperature of 1450–1570 °C due to increase in high-melting compound content to 27%. The viscosity of a slag with basicity of 2.5 without chromium oxide is 0.07–1.0 Pa·s in a narrow temperature range of 1650–1700°C and 0.14–1.0 Pa·s for a ‘shorter’ slag with 18% Cr2O3 and same basicity in even narrower range of 1650–1670°C. These slags have the highest high-melting phase content of about 50%.
By means of theoretical and experimental studies it is shown that it is possible to reduction cerium from the slags of the CaO–SiO2–Ce2O3 system containing 15%Al2O3 and 8 % MgO, by aluminum dissolved in metal, at temperatures of 1550 and 1650°C. The results of mathematical modeling are presented graphically as ‘composition – equilibrium content of cerium in metal’ diagrams. It is found that depending on temperature of metal, basicity of slag and the content of cerium oxide, from 0.055 to 16 ppm cerium passes into metal containing 0.06 % of carbon, 0.25 % of silicon and 0.055 % of aluminium. Positive influence of the temperature factor, basicity of slags and the content of cerium oxide in a studied range of chemical composition on process of cerium reduction is explained from the perspective of phase structure of formed slags and thermodynamics of reactions of cerium reduction. The possibility of reduction of cerium from slags of CaO–SiO2–Ce2O3 system, containing 15 % Al2O3 and 8 % MgO, has been experimentally confirmed. It has been shown that at basicity of 5 and 4 % of Ce2O3 in slag up to 16 ppm cerium passes into metal during 10 minutes exposure.
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