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<p>With the gradual reduction in high-quality iron ore resources, the global steel industry faces long-term challenges. For example, the continuous increase in the Al<sub>2</sub>O<sub>3</sub> content of iron ore has led to a decrease in the metallurgical performance of sinter and fluctuations in slag properties. Considering calcium ferrite (CF) and composite CF (silico-ferrite of calcium and aluminum, SFCA) play a crucial role as a binding phase in high-alkalinity sinter and exhibit excellent physical strength and metallurgical performance, we propose incorporating excess Al<sub>2</sub>O<sub>3</sub> into SFCA to form a new binding phase with excellent properties for high-quality sinter preparation. In the synthesis of high-Al<sub>2</sub>O<sub>3</sub> SFCA, two high-Al<sub>2</sub>O<sub>3</sub> phases were identified as types A (Al<sub>1.2</sub>Ca<sub>2.8</sub>Fe<sub>8.7</sub>O<sub>20</sub>Si<sub>0.8</sub>) and B (Ca<sub>4</sub>Al<sub>4.18</sub>Fe<sub>1.82</sub>Si<sub>6</sub>O<sub>26</sub>). Results show that type A SFCA sample had a higher cell density (4.13 g/cm<sup>3</sup>) and longer Fe–O bond length (2.2193 Å) than type B (3.46 g/cm<sup>3</sup> and 1.9415 Å), with a significantly greater lattice oxygen concentration (7.86% vs. 1.85%), which demonstrates advantages in strength and reducibility. Type A SFCA sample contained a lower proportion of silicates, was predominantly composed of SFCA, and exhibited minimal porosity. Melting point and viscosity simulation tests indicate that type A SFCA sample formed a liquid phase at 880°C with a viscosity range of 0–0.35 Pa·s, which is notably lower than that of type B SFCA sample (1220°C and 0–20 Pa·s). This finding suggests that type A SFCA sample has a low initial melting temperature and viscosity, which facilitates increasing liquid-phase generation and improving flow properties. Such a condition enhances the adhesion to surrounding ore particles. Compressive strength tests reveal that type A SFCA sample (36.83–42.48 MPa) considerably outperformed type B SFCA sample (5.98–12.79 MPa) and traditional sinter (5.02–13.68 MPa). In addition, at 900°C, type A SFCA sample achieved a final reducibility of 0.89, which surpassed that of type B SFCA sample (0.83). In summary, type A SFCA sample demonstrates superior structural, thermophysical, and metallurgical properties, which highlights its promising potential for industrial applications.</p>

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High-alumina type calcium ferrite: A new mineral phase for low-carbon ironmaking in the future

  • 期刊论文

  • 发表日期：

    2025年10月10日

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  • Rende Chang,
  • Chengyi Ding,
  • Feng Jiang,
  • Hongming Long,
  • Xuewei Lü,
  • Tiejun Chun,
  • Xiaoqing Xu,
  • Zhiming Yan,
  • Yue Sun,
  • Wei Lü

摘要

With the gradual reduction in high-quality iron ore resources, the global steel industry faces long-term challenges. For example, the continuous increase in the Al2O3 content of iron ore has led to a decrease in the metallurgical performance of sinter and fluctuations in slag properties. Considering calcium ferrite (CF) and composite CF (silico-ferrite of calcium and aluminum, SFCA) play a crucial role as a binding phase in high-alkalinity sinter and exhibit excellent physical strength and metallurgical performance, we propose incorporating excess Al2O3 into SFCA to form a new binding phase with excellent properties for high-quality sinter preparation. In the synthesis of high-Al2O3 SFCA, two high-Al2O3 phases were identified as types A (Al1.2Ca2.8Fe8.7O20Si0.8) and B (Ca4Al4.18Fe1.82Si6O26). Results show that type A SFCA sample had a higher cell density (4.13 g/cm3) and longer Fe–O bond length (2.2193 Å) than type B (3.46 g/cm3 and 1.9415 Å), with a significantly greater lattice oxygen concentration (7.86% vs. 1.85%), which demonstrates advantages in strength and reducibility. Type A SFCA sample contained a lower proportion of silicates, was predominantly composed of SFCA, and exhibited minimal porosity. Melting point and viscosity simulation tests indicate that type A SFCA sample formed a liquid phase at 880°C with a viscosity range of 0–0.35 Pa·s, which is notably lower than that of type B SFCA sample (1220°C and 0–20 Pa·s). This finding suggests that type A SFCA sample has a low initial melting temperature and viscosity, which facilitates increasing liquid-phase generation and improving flow properties. Such a condition enhances the adhesion to surrounding ore particles. Compressive strength tests reveal that type A SFCA sample (36.83–42.48 MPa) considerably outperformed type B SFCA sample (5.98–12.79 MPa) and traditional sinter (5.02–13.68 MPa). In addition, at 900°C, type A SFCA sample achieved a final reducibility of 0.89, which surpassed that of type B SFCA sample (0.83). In summary, type A SFCA sample demonstrates superior structural, thermophysical, and metallurgical properties, which highlights its promising potential for industrial applications.