Abstract: In order to study the LF refining slag system suitable for high cleanliness and high carbon steel， the influence of refining slag alkalinity （R），（CaO）/（Al₂O₃） on the melting point of the refined slag was calculated by FactSage thermodynamic software， and the most suitable refining slag composition was obtained. According to the thermodynamically calculated refining slag composition， the calcium-aluminum ratio of the original slag system was reduced， and the optimized slag composition was used for the 65Mn steel industrial test. The results show that the optimized refining slag components mass fraction are CaO 52%-58%， Al₂O₃ 28%-33%， SiO₂ 8%-12%， MgO 5%-7%， R=4-7， （CaO）/（Al₂O₃）=1.5-2. Using this slag system for industrial tests，（T.O） can reach 7×10^-6-13×10^-6 after LF process （T.O） can reach 6×10^-6-12×10^-6 after RH process. The mass fraction of dissolved oxygen in the basically controllable steel is within 10×10^-6， The Class B thin inclusion grades in the 65Mn steel coil are not more than 1 grade， which meets the requirement of high quality steel.

Key words: 65Mn Steel, LF, Refining Slag, Total Oxygen, Thermodynamic Calculation

摘要： 为了研究适合高洁净度高碳钢的LF精炼渣渣系，通过FactSage热力学软件计算精炼渣碱度（R）、（CaO）/（Al₂O₃）对精炼渣熔点的影响，得出最合适的精炼渣成分。根据热力学计算的精炼渣成分，降低原有渣系的钙铝比，并将优化的渣系成分用于65Mn钢工业试验。结果表明：优化后的精炼渣系成分质量分数为CaO52%～58%、Al₂O₃28%～33%、SiO₂8%～12%、MgO5%～7%、R=4～7、（CaO）/（Al₂O₃）=1.5～2；使用该渣系进行工业试验，LF出站时的（T.O）可达7×10^-6～13×10^-6，RH出站时的（T.O）可达6×10^-6～12×10^-6；钢中全氧质量分数基本可控制在10×10^-6内；65Mn钢卷中的B类细系夹杂均不大于1级，达到高级优质钢要求。

关键词: 65Mn钢, LF, 精炼渣系, 全氧, 热力学计算