Computational Insight into the Thermal Conductivity of CaO-SiO 2 -Al 2 O 3 -MgO-Na 2 O Melts
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THE mold fluxes are synthetic silicate slags constituted by complex mixtures of oxides, fluxes, and carbonaceous materials, which play essential roles in the steelmaking process.[1] For instance, in the continuous casting process, powders melt on the top of the steel to form the melt slags in the mold. The melt slags flow into the meniscus and form films between the solidified steel and copper mold to control the heat transfer and lubrication in the mold. As one of the most basic silicate slags, the CaO-SiO2-Al2O3-MgO-Na2O (CSAMN) system has been extensively studied and widely used in the mold flux. Accumulated evidence suggested that the longitudinal cracking problems can be alleviated by reducing heat transfer between the mold and shell. This is due to thermal imbalance between the austenite and ferrite phases, especially in casting high strength steel.[2,3] Thermal
ZHE WANG, GUANGHUA WEN, WENBO JIANG, and PING TANG are with the College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China and also with the State Key Laboratory of Mechanical Transmission, Chongqing University, Chongqing 400044, China. Contact e-mails: [email protected], [email protected] SHUHENG HUANG is with the College of Bioengineering, Chongqing University, Chongqing 400044, China. Manuscript submitted March 23, 2020.
METALLURGICAL AND MATERIALS TRANSACTIONS B
conductivity of melt layers has been regarded as the critical indicator for controlling the heat transfer around the meniscus, which has the maximum heat flux. Therefore, understanding the influence mechanism of the thermal conductivity of mold flux is of great significance for controlling the heat transfer at the meniscus. To date, comparatively little work has been attempted to explore the effect of components on the thermal conductivity of silicate melts. Kang and Morita[4] tested the thermal conductivity of the molten CaO-SiO2-Al2O3 (CSA) system using the transient hot-wire method and pointed out that the thermal conductivity of the CSA system decreased with the increasing CaO/SiO2 (C/S) mole ratio. Based on the front-heating front-detecting laser flash method, Hasegawa et al.[5] determined the thermal conductivity of CaO-SiO2-Na2O-Al2O3 melts. It turned out that the thermal conductivity of this system increases with the increase of the Al2O3/SiO2 (A/S) mole ratio. In addition, the lack of measurement standards of the thermal conductivity results in a large divergence of measured values among these research studies.[6] In spite of these exploratory studies, much of the detail of the CSAMN thermal conductivity still remains unclear. With the development of molecular simulation techniques, an improved understanding of the structure of the silicate would be beneficial for exploring the mechanism of heat transfer. Sørensen et al.[7] analyzed the thermal conductivity of lithium borate glasses at 300 K using the experimental methods and classical molecular
dynamics (MD) simulations. It turned out that the increase in the coordination number of boron increases th
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