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<p>During actual continuous casting process, the mold flux is subject to dynamic atmospheres comprising oxygen-enriched (simulated by air), micro-oxygen (simulated by N<sub>2</sub>), and oxygen-free (simulated by CO<sub>2</sub>) environments, which profoundly influencing the reaction behavior between carbon and mold flux. This study systematically investigated the thermal behavior, phase evolution, reaction mechanisms, and heat transfer properties of mold flux containing carbon materials under air, N<sub>2</sub>, and CO<sub>2</sub> atmospheres using TG-DSC, XRD, SEM–EDS, LFA and UV–Vis-NIR. Mass loss occurred in four distinct stages, with significant discrepancies observed between 673–1273 K and 1273–1673 K. Specifically, mass losses in air were 17.92% and 2.4%, whereas in N<sub>2</sub>, they were 7.61% and 10.75%, and in CO<sub>2</sub>, 12.25% and 9.05%. These variations are attributed to atmosphere-dependent carbon reactions, including combustion, melting loss, and carbon-slag interactions. XRD analysis indicated that residual carbon inhibits the formation of nepheline and suppresses the crystallization behavior of gehlenite in N<sub>2</sub> and cuspidine in CO<sub>2</sub>. It is because the kinetics of crystallization are suppressed. Carbon accumulates primarily on the surface of mold flux, hindering slag fusion and leading to distinct morphologies at 1273 K: molten in air, particulate in N<sub>2</sub>, and semi-molten in CO<sub>2</sub>. The atmosphere also influenced the fluorine distribution. Furthermore, residual carbon considerably reduced thermal conductivity especially between 873–1273 K, N<sub>2</sub> and CO<sub>2</sub> atmospheres yielded values as low as 0.699 and 0.701 W m<sup>-1</sup> K<sup>-1</sup>, respectively, due to higher carbon retention. Within the 500–2500 nm range, samples in N<sub>2</sub> (1.057–1.208) and in CO<sub>2</sub> (0.803–1.206) exhibited significantly higher absorbance, both exceeding 0.8, while those in air remains at 0.181–0.382, indicating a reduction in radiative heat transfer performance. These findings demonstrate that atmosphere selection and residual carbon content critically affect slag phase structure and heat transfer properties, providing valuable insights for the design of mold fluxes with tailored thermal performance.</p>

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Influence of high temperature reaction of carbon-containing materials in different atmospheres on the structure and heat transfer of mold flux

  • 期刊论文

  • 发表日期：

    2026年7月30日

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  • Shaopeng Gu,
  • Liang Yu,
  • Yu Wan,
  • Jingmeng Dong,
  • Jinhu Wu,
  • Mingming Chen

摘要

During actual continuous casting process, the mold flux is subject to dynamic atmospheres comprising oxygen-enriched (simulated by air), micro-oxygen (simulated by N2), and oxygen-free (simulated by CO2) environments, which profoundly influencing the reaction behavior between carbon and mold flux. This study systematically investigated the thermal behavior, phase evolution, reaction mechanisms, and heat transfer properties of mold flux containing carbon materials under air, N2, and CO2 atmospheres using TG-DSC, XRD, SEM–EDS, LFA and UV–Vis-NIR. Mass loss occurred in four distinct stages, with significant discrepancies observed between 673–1273 K and 1273–1673 K. Specifically, mass losses in air were 17.92% and 2.4%, whereas in N2, they were 7.61% and 10.75%, and in CO2, 12.25% and 9.05%. These variations are attributed to atmosphere-dependent carbon reactions, including combustion, melting loss, and carbon-slag interactions. XRD analysis indicated that residual carbon inhibits the formation of nepheline and suppresses the crystallization behavior of gehlenite in N2 and cuspidine in CO2. It is because the kinetics of crystallization are suppressed. Carbon accumulates primarily on the surface of mold flux, hindering slag fusion and leading to distinct morphologies at 1273 K: molten in air, particulate in N2, and semi-molten in CO2. The atmosphere also influenced the fluorine distribution. Furthermore, residual carbon considerably reduced thermal conductivity especially between 873–1273 K, N2 and CO2 atmospheres yielded values as low as 0.699 and 0.701 W m-1 K-1, respectively, due to higher carbon retention. Within the 500–2500 nm range, samples in N2 (1.057–1.208) and in CO2 (0.803–1.206) exhibited significantly higher absorbance, both exceeding 0.8, while those in air remains at 0.181–0.382, indicating a reduction in radiative heat transfer performance. These findings demonstrate that atmosphere selection and residual carbon content critically affect slag phase structure and heat transfer properties, providing valuable insights for the design of mold fluxes with tailored thermal performance.