Structure and Viscosity of Molten CaO-SiO2-FexO 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-Fe_xO 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-Fe_xO-based system was established in terms of the deconvolution result of the melt structure.