Transition of Blast Furnace Slag from Silicate Based to Aluminate Based: Density and Surface Tension
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INTRODUCTION
THE density and surface tension of molten slag are important and fundamental thermophysical properties that have a significant effect on industrial applications. Furthermore, the phase separation, dripping behavior, slag foaming, and slag-metal reactions in the blast furnace (BF) ironmaking process are likely influenced by the density and surface tension. For example, Hino et al.[1] found that the density and the surface tension of slag melts have significant influence on the dripping behavior of molten slag from reduced iron. Typically, the Al2O3 content of a BF type slag is less than 15 mass pct.[2] However, the huge global demand for steel products and the lower availability of
ZHIMING YAN, ZHENGDE PANG, XUEWEI LV, and CHENGUANG BAI are with the College of Materials Science and Engineering, Chongqing University, 174 Shazheng Street, Shapingba District, Chongqing, 400044 China. XUEWEI LV is with the College of Materials Science and Engineering, Chongqing University and also with the State Key Laboratory of Mechanical Transmissions, Chongqing University, 174 Shazheng Street, Shapingba District, Chongqing 400044, China. Contact email: [email protected] Manuscript submitted December 8, 2017.
METALLURGICAL AND MATERIALS TRANSACTIONS B
high-quality raw materials for the ironmaking process result in the increased use of low-cost and low-grade iron ores, such as high Al2O3 ore. The slag is converted from silicate based to aluminate based as a result of changes in the composition of the iron ore.[3] Thus, as a sequence of the previous studies,[3–5] the density and surface tension of high alumina slag are the subject of the present work. Many studies have been conducted on the density and surface tension of binary and ternary oxide systems, such as CaO-SiO2 and CaO-SiO2-Al2O3, and the results obtained by various methods are presented in the Slag Atlas.[6] For CaO-SiO2-Al2O3-MgO-(TiO2) slags, especially those high in Al2O3, the literature data are limited. Moreover, the bulk properties, such as viscosity, have been discussed in relation to the structure.[7,8] However, few researchers have examined the density and surface tension in conjunction with structural analysis. Similarly, the contribution of Al3+ species on the density and surface tension of the melts is poorly understood. In the present work, the effect of the Al2O3 content and Al2O3 M SiO2 substitution on the density and surface tension of the CaO-SiO2-Al2O3-9 mass pct MgO-1 mass pct TiO2 slag system was measured at elevated temperatures using the Archimedean method and the maximum bubble pressure (MBP)
technique,[6,9–11] respectively. The mechanism of the changes in density and surface tension with the composition was considered from the viewpoint of the polymerization degree of the structure and the types of oxygen species in the melts.
II.
EXPERIMENTAL
A. Materials CaO-SiO2-Al2O3-9 mass pct MgO-1 mass pct TiO2 slags were employed for the density and the surface tension measurements. The slags were prepared from pure grade reagents (CaO, SiO2, Al2O
