Influence of calcium aluminate flux on reoxidation behaviour of molten steel during continuous casting process

Abstract

It is an important issue to prevent molten steel in tundish from being reoxidized during the continuous casting process for improving the cleanliness of steel products. Rice husk ash (RHA) is an excellent insulation powder to prevent heat loss of the molten steel in the tundish. The addition of RHA increases the silica activity in the molten slag layer, which can cause reoxidation of molten steel. Therefore, the effect of calcium aluminate-based flux (CA-flux) on reoxidation behaviour was investigated with different ratios of CA-flux to RHA + CA-flux (=RCA). The silicon and oxygen pick-up, which is caused by the self-dissociation of silica at the slag/metal interface was suppressed with an increasing RCA, and hence the number of inclusions formed by reoxidation in the molten steel was reduced at high RCA. The evolution of inclusions with different RCA was investigated by comparing experimental results with predictions from a refractory-slag-metal-inclusion (ReSMI) multiphase reaction simulation. Finally, the inclusion formation behaviour in tundish was investigated using a ReSMI simulation with different RCA and including the temperature drop of the steel melts in the ladle during casting.