Direct Microalloying of Steel with Cerium under Slags of СаО–SiO₂–Ce₂O₃–15% Al₂O₃–8% MgO System with Additional Reducing Agents

An assessment of the possibility of steel direct microalloying with cerium was performed using thermodynamic modeling of cerium reduction from slags of CaO–SiO₂–Ce₂O₃ system containing 15% Al₂O₃ and 8% МgO, additional additives of reducing agents (aluminum or ferrosilicon-aluminum), at temperatures of 1550 and 1650°C using the HSC 6.1 Chemistry (Outokumpu) software package. Depending on the additional additives of aluminum or ferrosilicon-aluminum, metal temperature, slag basicity and content of cerium oxide, 0.228 to 40.5 ppm of cerium transfers into the metal. With an additional additive of aluminum from slag (Y₁) containing 1.0% of cerium oxide, 0.228 ppm of cerium is transferred to the metal at 1550°C. An increase in the system temperature to 1650°C is accompanied by a slight increase in cerium content, reaching no more than 0.323 ppm. When added to ferrosilicon-aluminum metal, cerium content in the metal is higher and amounts to 0.402 and 0.566 ppm at 1550 and 1650°C, respectively. When concentration of cerium oxide in the slag (Y₂) increases to 7.0%, more significant increase in cerium content in the metal is observed, reaching in temperature range of 1550–1650°C, 1.65–2.31 ppm with aluminum additives and 2.90–4.05 ppm with ferrosilicon-aluminum additives. The most noticeable increase in cerium content in the metal is observed with an increase in slag basicity. During formation of slags with basicity of 2–3, containing 1–7% Ce₂O₃, the equilibrium concentration of cerium in the metal varies from 0.5 to 4 ppm with aluminum additives and 1–7 ppm with ferrosilicon-aluminum additives at 1550°C. Slags transfer to the increased (up to 3–5) basicity is accompanied by an increase in the equilibrium content of cerium in the metal to 4–12 ppm with aluminum additives and 7–20 ppm with ferrosilicon-aluminum additives at Ce₂O₃ content of 3–7% and, as a result, an increase in efficiency of cerium reduction process.