Interfacial tension between molten iron and CaO-SiO2-MgO-Al2O3-FeO slag system

The interfacial tension of the CaO-Al 2 O 3 -SiO 2 -MgO-FeO slags with liquid iron at 1550°C was investigated using a synchrotron X-ray beam source. The interfacial tensions of molten slag with liquid iron increased continuously with increasing CaO/SiO 2 ratio for both CaO-SiO 2 -MgO and CaO-SiO 2 -Al 2 O 3 -MgO slag systems. However, the contents of MgO and Al 2 O 3 exceeded the saturation limit and the apparent interfacial tension decreased markedly. This decrease was attributed to formation of a solid phase at or near the interface: MgO particles for MgO saturation and MgAl 2 O 4 particles for Al 2 O 3 saturation. It was found to be oxygen in iron that exerts a dominating influence on the interfacial tension. Its influence was so dominant that all other compositional effects were insignificant. The effect of oxygen was quantitatively determined by employing the Gibbs adsorption and Langmuir isotherms.