Shear-thinning behavior of the CaO–SiO₂–CaF₂–Si₃N₄ system mold flux and its practical application

Ying Xu¹，Zhi-peng Yuan²，Li-guang Zhu²，Yi-hua Han²，Xing-juan Wang²

1. Hebei Provincial Key Laboratory of Inorganic Nonmetallic Materials, College of Materials Science and Engineering, North China University of Science and Technology2. Key Laboratory for Advanced Metallurgy Technology, Hebei Provincial High-Quality Steel Continuous Casting Engineering Technology Research Center, College of Metallurgy & Energy, North China University of Science and Technology

摘 要：Satisfying the mold-flux performance requirements for high-speed continuous casting necessitates the development of a new non-Newtonian-fluid mold flux with shear-thinning behavior, i.e., a mold flux whose viscosity is relatively high under lower shear rates and relatively low under higher shear rates. In this work, a mold flux that exhibits shear-thinning behavior was developed by adding different amounts of Si₃N₄ to the CaO–SiO₂–CaF₂ mold flux. The shear-thinning behavior was investigated using a rotational viscometer. In addition, the microstructure of the newly prepared slags was studied by high-temperature Raman spectroscopy and X-ray photoelectron spectroscopy. The results showed that the mechanism of shear-thinning was attributable to a temporary viscosity loss caused by the one-way shear stress, whereas the corresponding magnitude of shear-thinning was closely related to the degree of polymerization（DP）. Finally, the non-Newtonian fluid mold flux was used for laboratory casting tests, which revealed that the mold flux could reduce slag entrapment and positively affect the continuous casting optimization.

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