In the first part of the present study, the relation between the dimension free critical capillary number Ca* and the material number Λ are introduced as a stability criteria for slag entrainment at the steel/slag interface. With the knowledge of thermophysical properties of the immiscible liquids in contact, critical values of Ca* for slag entrainment as a function of Λ could be estimated. The interfacial tension was investigated at 1823 K for carbon and Cr–Ni steels in contact with ternary slags containing CaO, SiO2, Al2O3, MgO and TiO2 using the drop weight method. The apparent interfacial tension of CaO–SiO2–TiO2 slag systems in contact with Cr–Ni steel decreases with increasing TiO2 content and was found to be influenced by interfacial area change during droplet formation at the capillary exit, slag composition and reactions at the steel/slag interface. Minimum values of interfacial tension, observed during measurements, increase the possibility for slag entrainment in the continuous casting mould.
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