单项选择题
A.开始通电B.通电15分钟后C.熔炼后期D.出钢
A.废钢熔化B.脱硫C.脱磷D.脱碳
A.CaO﹒6Al2O3B.CaO﹒2Al2O3C.3CaO﹒6Al2O3D.12CaO﹒7Al2O3