Abstract

  To clarify the interaction mechanism between MgO and Al2O3 based tundish gunning materials (GM) and liquid steel. 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 impurities, low-melting-point phases and the pores in GM were passageway for steel penetration. Quartz and hematite in gunning materials are reduced by the dissolved Al, Ti, Mn and Si in molten steel, and then liquid steel penetrated into the sites where they located, resulting in steel infiltration. The pores and low melting point phases in gunning materials also provided the passageway for steel infiltration. The steel infiltration damaged the integrity of gunning materials, as a result, the refractory materials particles fell into liquid steel to become large-sized inclusions. 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 oxide impurities (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 for the tundish lining.