2017 Volume 57 Issue 6 Pages 978-982
The viscosity of CaO–SiO2–MgO–Al2O3 slags (CaO/SiO2=1.0, 14–17 mass% Al2O3, 5–15 mass% MgO) was measured to analyze the effect of MgO and Al2O3. The infrared spectra was employed to analyze the ionic structure of the slag. The viscosity of CaO-SiO2-MgO-17% Al2O3 slags decreases with the increase of MgO content which is in the range of 5%–10 mass%. However, the dependence relationship is reversed when MgO content is over 10 mass%. The viscosity of CaO-SiO2-10 mass% MgO–Al2O3 slags and CaO-SiO2-11% MgO–Al2O3 slags exhibits the minimum value at 16 mass% Al2O3, which may contribute to the amphiprotic properties of Al2O3. The above phenomenon can also be verified by the infrared spectra. Simultaneously, in order to make the blast furnace working smoothly, the viscosity value of the slag is below 1.0 Pa·s commonly. Thus, we define the temperature of the slag with a viscosity value of 1.0 Pa·s as “Critical Temperature (CT)”. And, the effect of MgO and Al2O3 content on CT is also studied by the phase diagram. We can conclude that the fall of the CT can be owe to the simplified network structure at the MgO content from 5 mass% to 10 mass%, while the rise may be because of the appearance of solid phase at the MgO content from 10 mass% to 15 mass%.