The viscosities of the industrial and synthetic iron blast furnace slags have been measured using a custom designed rotating bob apparatus. This advanced apparatus enables control of the gas atmosphere and rapid quenching of the samples on completion of the viscosity measurements. The experiments were carried out using Mo spindle and crucible under ultra-high purity Ar flow. The microstructures and phase compositions of the quenched slag samples were determined by Electron Probe X-ray Microanalysis (EPMA) after the viscosity measurements.
It was found that the viscosities of the industrial slags are lower than those of the corresponding synthetic slags made from pure Al₂O₃, CaO, MgO and SiO₂. The difference in viscosities between industrial slags and synthetic slags will provide useful indications when applying the results of the synthetic slags to the real iron blast furnace slags. The activation energy of both industrial and synthetic slags is 174 kJ/mol and increases with decreasing MgO concentration. Replacement of (CaO+SiO₂) or CaO by MgO can decrease the slag viscosity. The viscosity of iron blast furnace slag at 1500°C can be estimated by V = 0.005+0.0262[SiO₂]+0.0184[Al₂O₃]–0.0172[CaO]–0.0244[MgO] which is derived from the present and previous data.