Interfacial Tension between Molten Iron and CaO-SiO₂ Based Fluxes^*

Abstract

Flux-metal interfacial tension has been examined by X-ray photography of a metal drop melted in a molten flux. The experiments were carried out at 1 580°C using a zirconia crucible with low solubility in the fluxes. The systems used in the investigation were as follows:
Metal phase: Fe-O alloy, oxygen content in the alloys varied from 0.002 to 0.070 mass%.
Flux phase: Ternary system: CaO-SiO₂-M_x(F, O)_y, where M_x(F, O)_y represents NaF, CaF₂, Al₂O₃, Na₂O, MgO, Li₂O or ZrO₂ and concentrations varied from 2 to 40 mass%. Multicomponent system: CaO-SiO₂-Al₂O₃-Fe₂O₃-Na₂O-NaF-CaF₂-MgO-Li₂O-ZrO₂.
The interfacial tension was observed to increase with increasing NaF, CaF₂, Na₂O, MgO or Li₂O contents, while only minor changes in the values were observed with varying Al₂O₃ or ZrO₂ contents in CaO-SiO₂ or CaO-SiO₂-Al₂O₃ systems. The interfacial tensions between flux and molten iron decreased with increasing oxygen activity in iron,

γ=γ₀-0.324 ln(1+116a_O)