Structure and Viscosity of Molten CaO-SiO 2 -Fe x O Slag During the Early Period of Basic Oxygen Steelmaking

According to the composition variation during the initial period of basic oxygen steelmaking, ice-quenched samples of the CaO-SiO2-FexO system were prepared, and the viscosity and structure of molten slag were further analyzed by a rotary viscometer and Raman spectroscopy, respectively. The results showed that Si4+ existed as Q0, Q1, Q2 and Q3 units. The O2− ions led to the depolymerization of [SiO4] tetrahedrons from Q3 to Q0 units with increasing Ca/Fe ratio. For Fe3+ cations, two types of [FeO4] tetrahedron and [FeO6] octahedron coexisted in the molten slag, and coordination of Fe3+ transformed from tetrahedron to octahedron with the Ca/Fe ratio increasing to 3.18. Viscosity of molten slag showed a continuous decrease because of the simpler network. Moreover, to clarify the viscosity-structure relationship, the viscosity estimation equation applied to the CaO-SiO2-FexO-based system was established in terms of the deconvolution result of the melt structure.