Effect of Al2O3 substituting SiO2 on the basic properties of high TiO2 mold slags

WANG Wenhong; WANG Jun; QIAO Qi; SHI Weining; YANG Bei; ZHANG Xubin; HE Shengping

doi:10.13228/j.boyuan.issn1005-4006.20240009

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Continuous Casting ›› 2024, Vol. 43 ›› Issue (3) : 87-94. DOI: 10.13228/j.boyuan.issn1005-4006.20240009

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Effect of Al₂O₃ substituting SiO₂ on the basic properties of high TiO₂ mold slags

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Abstract

Aiming at the problem of TiO₂ increase and slag denaturation caused by steel-slag reaction in traditional mold slags for the casting of high titanium steel. In this study, rotational viscosity measurement, hemisphere point measurement, FactSage thermodynamic calculation and in-situ crystallization observation are conducted. The effect of Al₂O₃ substituting SiO₂ on the flow, melting and crystallization characteristics of the mold slags of high titanium steel after reaction was studied in order to regulate the properties of the TiO₂-containing mold slags through the change of composition. Results show that when the TiO₂ content in the slag is 12%, and the Al₂O₃ content increases from 0% to 12%, the viscosity of the slag increases from 0.14 Pa·s to 1.34 Pa·s, and the melting temperature of the slag increases from 1 095 ℃ to 1 172 ℃. The activation energy of viscous flow increased from 128.4 kJ/mol to 389.1 kJ/mol. When Al₂O₃ replaces SiO₂ from 0% to 10%, the binary alkalinity of the slag also increases from 0.72 to 1.0. The initial crystallization phase of the slag calculated by thermodynamics is CaTiO₃, followed by the precipitation phase is cuspidine. When Al₂O₃ replaces SiO₂ at 12%, the basicity rises to 1.08, and then the precipitated phase changes to NCA2. When the Al₂O₃ content is 4%-12%, the crystalline phase in the air-cooled slag detected by XRD is CaTiO₃. When Al₂O₃ in slag increases from 0% to 12%, the complete crystallization temperature increases from 728 ℃ to 1 214 ℃. Therefore, in the TiO₂-containing mold slag discussed in this study, the replacement of SiO₂ by Al₂O₃ will cause a significant increase in the viscosity, melting point and crystallization properties of the mold slag. In order to ensure the lubrication of the mold slag on the slab during the continuous casting, the content of Al₂O₃ in the slag should be decreased when the traditional calcium-silicon mold slag is used to cast high titanium steel. The content of Al₂O₃ in the slag should be increased to enhance the control of the heat transfer of the slag.

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high titanium steel / mold slag / Al₂O₃ substituting SiO₂ / viscosity / crystallization

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WANG Wenhong, WANG Jun, QIAO Qi, et al. Effect of Al₂O₃ substituting SiO₂ on the basic properties of high TiO₂ mold slags[J]. Continuous Casting, 2024, 43(3): 87-94 https://doi.org/10.13228/j.boyuan.issn1005-4006.20240009

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