Effect of the Tundish Gunning Materials on the Steel Cleanliness

To clarify the interaction mechanism between distinct tundish gunning materials (GM) and liquid steel, two kinds of gunning materials, namely MgO, Al2O3 GM, were tested. SEM, EDS, XRD and chemical analysis were carried out for steel and GM to investigate the change of chemical composition of steel in contact with GM and the interface microstructure between steel and GM after high temperature holding experiments. The steel cleanliness in terms of inclusion number density, size and size distribution was evaluated. It was found that the reducible component, low-melting-point phases and the pores in GM were passageway for steel penetration. The Al2O3 GM was less prone to steel penetration due to its poor wetting and the dense transition layer. MgO GM provided more oxygen and showed a stronger oxidizing capacity due to its higher content of reducible oxides (10.5 wt.% SiO2+2 wt.% Fe2O3). The use of Al2O3 GM resulted in an improved steel cleanliness and consequently could be a promising refractory in the tundish lining.