The Effect of Oxygen Content in Molten Iron on the Interfacial Tension between Molten Iron and Slag

Abstract

The interfacial tension between molten iron and slag was measured by the sessile drop method with the transmission X-ray technique. Oxygen in iron remarkably decreased the surface tension of iron melt and the interfacial tension at the slag-metal boundary. It suggests that the oxygen dissolved in molten iron acts as a surface active solute at the slag-metal interface. Consequently, the interfacial tension depended, in most part, on the oxygen content in iron melt, but the composition of the slag had a minor effect on the interfacial tension.
In order to clear the effect of slag composition on the interfacial tension, experimental results were discussed in terms of Δσ(=σ_m-σ_ms) that indicated the difference between the surface and the interfacial tension at a constant content of sufrace active solute in iron melt. The values of Δσ decreased with increasing silica content in slags. The difference between oxygen and sulfur in molten iron as a surface active solute is that Δσ for oxygen is approximately constant at a constant content of silica in slags, while for sulfur it depends not only on the silica content but also on the sulfur content in molten iron. Therefore, it will be concluded that sulfur in molten iron and silica in molten slags decrease the interaction between slag and iron melt.
The work of adhesion between molten iron and slag, W_ad. (=σ_m+σ_s-σ_ms) depends on the slag composition. The values of W_ad. for the fluoride slag-iron system were smaller than that for the oxide slag-iron system. The values for the later system decreased with increasing silica content in slags.