Influence of compositional change in tundish flux on the reoxidation of molten steel

Abstract

The reoxidation in tundish can be occurred not only due to the contamination of molten steel from the air but also due to the slag-metal reaction, e.g. the reduction of silica in slag layer by aluminum in molten steel. This is highly important in the aluminum-killed steels. The silica in tundish slag generally originates from the carried-over ladle slag as well as the rice husk which was covered for the purpose of thermal insulation. Hence, we investigated the influence of the amount of the rice husk, which can affect the composition of tundish slag, on the interfacial reaction between tundish slag and molten steel at 1823K. The Al content in molten steel rapidly decreased within 10 min while the Si content continuously increased throughout the entire reaction time, 60 min. This was originated from the fact that Si was continuously transferred from tundish flux by the slag-metal reaction as well as by the dissociation of silica under condition of high activity of SiO2 in tundish slag. Furthermore, an increase in the activity of SiO2 in tundish slag by addition of rice husk resulted in the acceleration of the corrosion of MgO refractory, which affecting the thermophysical properties of tundish slag.