In ??tore Steel steelworks steel is casted on a three strand continuous casting machine. Lining of tundish is mainly made from a magnesia based material. Tundish cover powder is based on alumina and silica. It also contains aluminum and carbon.During casting, the composition of cover slag is constantly changing. When steel in casted in sequences the change in cover slag composition depends on the amount of CaO rich ladle slag. The composition of tundish cover slag at the end of the casting sequence lies in the area of gehlenite (2CaO?·Al2O3?·SiO2) in ternary phase diagram CaO?·Al2O3?·SiO2.The result of the reaction between melted steel, refractory material and tundish cover slag are enstatite (MgO?·SiO2) and monticellite (CaO?·MgO?·SiO2). Merwinite (3CaO?·MgO?·SiO2) is formed in the end of the casting sequence because of high basicity of the gehlenite based tundish cover slag.Clogging on the inner side of submerged entry nozzles (SEN) are made of calcium aluminates (CaO?·2Al2O3) and spinel (MgO, MnO)?·Al2O3. Only when steel is casted in sequence composition changes in tundish cover slag and clogging occurs.
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