Abstract: The composition of macro inclusion in 20MnTiB steel and 45 steel melting by 70 t EAF-LF-CC flow sheet at Egang and ingredient of mold powder and refractory material for concasting process have been analyzed,and it is obtained that the macro inclusion of steel is a composite inclusion which mainly consists of Al₂O₃,MgO,CaO,Na₂O and SiO₂. With improving technology measures including white refining time ≥10 min,controllingAl_s./Al_t,≥85%,after feoding Ca- Si wire soft argon stirring time ≥7 min,controlling immersion depth of ladle nozzle ≥200 mm and immersion depth of im- mersion nozzle 80～130 mm,and using quality refractory materials,the qualified steel rate for macro inclusion examination increased to 99.77%～100% from original 90.96%~95.31%.

Key words: EAF-LF-CC, Macro Structure, Inclusion, Technology Control

摘要： 分析了鄂钢70 t EAF-LF-CC流程生产的20MnTiB钢和45钢低倍夹杂物的成分以及结晶器保护渣和 连铸工艺耐火材料的组成，得出钢的低倍夹杂主要是由Al₂0₃、Mg0、CaO、Na₂O、SiO₂组成的复合夹杂物。通过改进工艺：白渣精炼时间≥10 min,控制Al_s./Al_t≥85%,喂Ca-Si线后软吹氩≥7 min,控制钢包水口插人深度≥200 mm,浸人式水口插人深度80～130 mm,采用优质耐火材料等措施，使低倍夹杂物检验合格率由90.96%～95.31% 提高到99.77%～100%。

关键词: EAF-LF-CC,  , 低倍组织, 夹杂物, 工艺控制