Desiliconization rate of molten high carbon iron by slags containing FeO

The oxidation rates of silicon in molten high carbon iron by synthetic slags containing FeO, pure FeO and LD slag were examined at 1300 to approximately 1500 °C. The results were analyzed with a coupled reaction model. The oxidation rate of silicon was more rapid with higher FeO content in slag, because the interfacial oxygen activity and the transport rate in slag were increased with increasing FeO content in slag. For the LD slag, the silicon oxidation proceeded simultaneously with the reduction of MnO in slag, whereas the dephosphorization of the metal was not observed with this slag. As an oxide CO was more thermodynamically stable than silica under the present experimental conditions, but the oxidation of silicon proceeded prior to the decarburization at the early stage of reaction. This result suggested that the decarburization was controlled by the chemical reaction, while the oxidation of silicon was controlled by the mass transfer. After the silicon was oxidized to certain contents, which were depended on the experimental conditions, the decarburization predominantly proceeded. This behavior was well explained by the coupled reaction model. The analysis of experimental results with reaction model suggested that the oxidation rate of silicon was controlled by the transport rate of FeO in slag.