Viscosity-Structure Relationship in the CaO-SiO2-MnO-CaF2 Slag for the Production of Manganese Ferroalloys

The viscosity of the CaO-SiO₂-xMnO-yCaF₂ slags (C/S=1.0; x=10, 40%; y=0 to 15%) was measured to clarify the effect of CaF₂ on the viscous flow of molten slags at high temperatures. Furthermore, the Raman spectra of the quenched glass samples were quantitatively analyzed to investigate the structural role of CaF₂ in a depolymerization of silicate networks. The critical temperature of the slags abruptly increased at 15%CaF₂, which was confirmed to originate from a crystallization of cuspidine using XRD analysis. The viscosity of the slags continuously decreased by CaF₂ addition in the 10%MnO system, whereas the viscosity of the 40%MnO system was not significantly affected by CaF₂ addition. The effect of CaF₂ on the viscosity of the slags was quantitatively analyzed using micro-Raman spectra of quenched glass samples accompanying with a concept of silicate polymerization index, Q3/Q2 ratio. A polymerization index continuously decreased with increasing content of CaF₂ in the 10%MnO system, whereas it was not affected by CaF₂ in the 40%MnO system. Consequently, the bulk thermophysical property of the CaO-SiO₂-MnO-CaF₂ slags was quantitatively correlated to the structural information.