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<p>Alumina spinel refractories (MgAl<sub>2</sub>O<sub>4</sub>) are widely utilized in the steel industry due to their superior resistance to molten metals compared to alumina refractories. This study examines the effects of incorporating calcium oxide (CaO) and magnesium oxide (MgO) at varying concentrations on the microstructure and mechanical properties of castable alumina refractories at different temperatures. Samples containing 0%, 5%, 10%, and 15% CaO and MgO were prepared and heated at temperatures of 110, 750, 1150, and 1400&#xa0;°C. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed for phase and microstructural analysis. The cold compressive strength (CCS) increased from 110&#xa0;MPa (0% CaO/MgO) to 211&#xa0;MPa at 5% CaO and 5% MgO (CM0505) due to the enhanced formation of the spinel phase. However, increasing the CaO content beyond 5% led to a decrease in strength to 168&#xa0;MPa (10% CaO/MgO) and 150&#xa0;MPa (15% CaO/MgO) at 1400&#xa0;°C. This reduction is attributed to the formation of weaker calcium aluminate (CA, CA<sub>2</sub>) phases and increased porosity. These findings emphasize the optimal composition of 5% CaO and 5% MgO, which yields the highest CCS and improved microstructural stability. This study can provide insight into optimizing the composition of alumina refractories to enhance their mechanical strength and thermal resistance for high-temperature applications.</p>

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The effect of CaO and MgO on the mechanical and microstructure properties of castable alumina refractories

  • 期刊论文

  • 发表日期：

    2026年4月15日

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  • Kamran Ashrafian,
  • M. R. Nilforoushan,
  • Ibrahim Sharifi

摘要

Alumina spinel refractories (MgAl2O4) are widely utilized in the steel industry due to their superior resistance to molten metals compared to alumina refractories. This study examines the effects of incorporating calcium oxide (CaO) and magnesium oxide (MgO) at varying concentrations on the microstructure and mechanical properties of castable alumina refractories at different temperatures. Samples containing 0%, 5%, 10%, and 15% CaO and MgO were prepared and heated at temperatures of 110, 750, 1150, and 1400 °C. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed for phase and microstructural analysis. The cold compressive strength (CCS) increased from 110 MPa (0% CaO/MgO) to 211 MPa at 5% CaO and 5% MgO (CM0505) due to the enhanced formation of the spinel phase. However, increasing the CaO content beyond 5% led to a decrease in strength to 168 MPa (10% CaO/MgO) and 150 MPa (15% CaO/MgO) at 1400 °C. This reduction is attributed to the formation of weaker calcium aluminate (CA, CA2) phases and increased porosity. These findings emphasize the optimal composition of 5% CaO and 5% MgO, which yields the highest CCS and improved microstructural stability. This study can provide insight into optimizing the composition of alumina refractories to enhance their mechanical strength and thermal resistance for high-temperature applications.