Effect of Al2O3 and MgO on Interfacial Tension Between Calcium Silicate-Based Melts and a Solid Steel Substrate

The effect of Al2O3 and MgO on the interfacial tension between the molten CaOSiO2-based slag and solid steel at 1773?K was studied. The interfacial tension of molten slags slightly increased with increasing Al2O3, but no significant change of interfacial tension was observed with higher MgO. Fourier transform infrared (FTIR) of as-quenched slag samples indicated the slag structure to polymerize with Al2O3 additions, but depolymerize with MgO additions. Further detailed studies of the slag surface using X-ray photoelectron spectroscopy (XPS) showed the fraction of free oxygen ions to decrease with higher Al2O3 but remained constant at higher MgO. The results suggested that interfacial tension decreases not only with the depolymerization of the melt, but also with an increase in the free oxygen ions at the molten slag/solid steel interface.