Phase Equilibria of the MnO–SiO2–Al2O3–MnS System
Abstract:Phase equilibria of the MnO–SiO2–MnS system in the temperature range of 1185°–1400°C and the MnS solubility in the MnO–SiO2–Al2O3–MnS system at 1200°C under low oxygen partial pressure have been experimentally investigated using equilibration/quenching technique followed by electron probe X-ray microanalysis and X-ray diffraction analysis. Based on the experimental results, polythermal projection of the MnO–SiO2–MnS system was estimated. The system has two ternary eutectic points; namely, one at 1173°± 3°C where phases of MnS, MnO, “A” (67.0 mass% MnO–23.6 mass% SiO2–9.4 mass% MnS), and liquid coexist, and the other at 1187°± 3°C where phases of MnS, Mn2SiO4, MnSiO3, and liquid coexist. All invariant reactions observed above were discussed. The ternary compound “B” containing 74.4 mass% MnO–22.0 mass% SiO2–3.6 mass% MnS was observed at 1300°C. In the MnO–SiO2–Al2O3–MnS system, the MnS solubility is strongly affected by Al2O3 content and also the MnO/SiO2 ratio. The solubility increased as MnO/SiO2 ratio increased at a constant Al2O3 content and decreased as Al2O3 content increased at a constant MnO/SiO2 ratio. In addition, depending on the Al2O3 content and MnO/SiO2 ratio, the liquid phase is possibly saturated with not only MnS but also other solid oxide phases. In view of inclusion utilization for free-cutting steel, it might have an advantage to decrease the Al2O3 content and increase the MnO/SiO2 ratio.
Document Type: Research Article
Affiliations: Graduate Institute of Ferrous Technology (GIFT), Pohang University of Science and Technology (POSTECH), Pohang 790-784, Korea
Publication date: July 1, 2010