The viscosities of the industrial basic oxygen furnace (BOF) slag with varying compositions of MgO, Al₂O₃, TiO₂, and MnO were continuously measured at a temperature range between 1400 and 1700 °C using the rotating bob method. Three characteristic temperatures for the melting behavior of the BOF slag were investigated using a high-temperature microscope. The solid fraction of the slag was calculated by FactSage 7.2 using the FTOxid database. General observations from the experimental data show that the increase in MgO tends to increase viscosity. However, Al₂O₃, TiO₂, and MnO decrease viscosity up to a certain level, and beyond that, they also increase the viscosity. The measured values of the viscosity of BOF slags were compared and discussed with known data from the literature. Finally, the activation energy of BOF slags with different compositions of MgO, Al₂O₃, TiO₂, and MnO was calculated in the temperature range of industrial operations.

Thermo-physical properties of the liquid metals and alloys play an essential role in modeling and controlling metallurgical processes. In particular, surface tension of metals has a strong impact on wetting various surfaces. Boron is added in numerous iron-based alloys as micro-alloying component. In existing literature, there is no general agreement with the effect of boron on the surface tension. The present study focuses on investigations of boron micro-alloying on the surface tension of iron and CrMnNi alloys by the maximum bubble pressure method (MBP). In contrast to other techniques, maximum bubble pressure technique is less affected by the evaporation of surface-active elements and the purity of the atmosphere around the sample. Measurement of the surface tension was accomplished before and after in situ addition of boron to the molten metal phase. Samples were molten in ZrO₂ and Al₂O₃ crucibles and yttria-PSZ capillaries were used for the experiments. Measurements were carried out at 1550 °C in argon atmosphere and argon as bubbles formation media. Results of the experiments indicate a minor effect of boron on the surface tension of liquid iron. Effect of boron on the surface tension of steels is discussed in the context of other surface-active elements present.