Abstract
The influence of steel grade on the oxidation rate of molten steel in tundish was studied by conducting oxidation experiments on the Ti and Ti-Al deoxidized molten steel and comparing the obtained oxidation rates with that of the Al deoxidized molten steel as measured in a previous report. In the still state, the oxidation rate of the Ti deoxidized molten steel is faster than those of the Ti-Al deoxidized molten steel and the Al deoxidized molten steel, showing dependence on the steel grade. This means that in the still state, while the oxidation rates of the Ti-Al and Al deoxidized molten steel are controlled by the mass transfer of oxygen in the oxide film, the oxidation rate of the Ti deoxidized molten steel is controlled by the mass transfer of O2 gas in the gas phase because the surface is not covered with oxide films. In addition, in the stirred state, the oxidation rates of the Ti and Ti-Al deoxidized molten steel become faster than that of the Al deoxidized molten steel in the region where the O2 gas partial pressure exceeds 10 kPa. This dependence on the steel grade can be explained by the mechanism of accelerating the mass transfer in the gas phase due to active iron evaporation in the Ti and Ti-Al deoxidized molten steel, in which the surface disturbance is larger than that in the Al deoxidized molten steel.
