Viscosity Estimation of TiO2-Bearing Blast Furnace Slag with High Al2O3 at 1500 °C

Slag compositions are significant for the viscosity of blast furnace slag. An improved Urbain model (IUM) was proposed by introducing R5 ((X(CaO) + X(MgO) + 2X(TiO2))/(2X(SiO2) + 3X(Al2O3))) and N (X(MgO)/3X(Al2O3)) as the model parameters. By comparing IUM with other models, the model parameters of R5 and N are more reasonable and suitable for TiO2-bearing blast furnace slag, and IUM for predicting viscosity has a higher precision, and its relative error is only 10%. The viscosity isolines of the CaO–SiO2–15%Al2O3–MgO–2.5% TiO2 system were plotted, and the results show that the viscosity center of the slag is between Rw2 (w(CaO)/w(SiO2)) = 0.77–1.39 and Nw (w(MgO)/w(Al2O3)) = 0–1.37, the value of the viscosity center is 0.3 Pa·s, the viscosity increases gradually from the center to the outside, and the viscosity of the slag gradually decreases with the increase in Nw and Rw2. Furthermore, FTIR (Fourier Transform Infrared Spectroscopy) analysis was carried out in order to understand the mechanism between the slag structure and viscosity. With the increase in Nw and Rw2, the peak values of the symmetrical stretching vibration of non-bridging oxygen in the Si–O tetrahedral structure of slag decrease, and the slag structures depolymerize, which leads to the decrease in the viscosity of the slag.