Influence of additives on properties of high-carbon ferrochrome slag

Abstract

Industrial slags produced by high-carbon ferrochrome are a material of complex composition consisting of an oxide part (Cr2O3 , CaO, MgO, FeO, SiO2 , Al2O3 ) and “entangled” metal prills (Crmet ). In order to increase the degree of chromium utilization and reduce losses in the form of metal prills, we conducted the laboratory experiments to study changes in properties of the slag produced by high-carbon ferrochrome through the use of effective and affordable fluxing materials: expanded clay, calcium borate and refined ferrochrome slag. The effect of fluxing additives in the form of expanded clay, calcium borate and slag from the production of low-carbon ferrochrome on the properties of high-carbon ferrochrome slag was studied. Addition of up to 8 % of expanded clay and low-carbon ferrochrome slag leads to a stable decrease in the softening temperatures of the final slags. The greatest intensity of decrease in the softening temperature is observed when calcium borate is injected in an amount of 6 ‒ 10 %. The greatest effect on reducing softening temperatures is exerted by the addition of 10 % calcium borate when introducing high-carbon ferrochrome into the slag, while the temperature of softening beginning decreases by 262 °С, and the temperature of softening end – by 135 °С. All the studied fluxing additives have a positive effect on reduction degree of the residual concentration of metallic chromium in the slag. The most intense decrease in the content of Crmet in the slag is observed with the introduction of 2 % of fluxing materials. The best values for the residual content of 0.7 ‒ 0.8 % Crmet were achieved using 4 % of low-carbon ferrochrome slag and calcium borate. When using expanded clay, an additive in the amount of 10 % is required to achieve such indicators of Crmet . In general, the effectiveness of using the studied fluxing materials to increase the degree of chromium extraction in the production of high-carbon ferrochrome is shown, its content in the slag is reduced by 84 %.