Hot Corrosion of Slag Line in Plaster of Tundish in Continuous Casting of Steel

Plasters are produced from a light refractory material, mainly MgO (M.P. 2800ºC), a binder, and a void forming substance for insulating purposes. Different oxides from the slag penetrate into these voids and provide low melting-point phases such as rhodonite (MnSiO3) (1290ºC), tephorite (Mn2SiO4) (1345ºC), merwinite (Ca3MgSi2O8) (1575ºC), monticellite (CaMgSiO4) (1490ºC), and enstatite (MgSiO3) (1560ºC). XRF, XRD, and microanalysis by EDX were used to investigate and evaluate the penetration of different oxides to distances below the slag-plaster interface. Results show that SiO2 and MnO are the most deteriorating while alumina and calcite are the least harmful. It is suggested that rice husk cover on melt, which is rich in SiO2, be replaced with insulating powders rich in Al2O3 and CaO, and that slag basicity be increased in order to decrease the slag line hot corrosion of plaster.