Corundum bricks refer to refractory bricks with an alumina content of more than 85%. According to the production process, they can be divided into sintered corundum bricks and electrically fused corundum bricks. Chromium corundum refractory bricks are high-grade refractory materials made by introducing Cr₂O₃ into the corundum matrix and then forming and sintering at high temperatures. They also include two types: casting and sintering. Both materials are widely used in high-temperature industries, but there are significant differences in their performance characteristics.
Comparison of high-temperature performance
The refractory temperature of chromium corundum refractory bricks is higher than 1790℃, and the melting point softening temperature exceeds 1700℃. In contrast, the operating temperature of pure corundum refractory bricks is generally around 1600℃. Thus, the high-temperature performance of chromium corundum bricks is significantly better than that of pure corundum bricks, making them more suitable for extreme high-temperature environments.
Mechanical performance differences
In terms of the compressive strength at room temperature, aluminous refractory bricks typically range from 70 to 100 MPa, while the compressive strength of chromaxial refractory bricks at room temperature is greater than 150 MPa, significantly higher than that of aluminous bricks. This difference stems from the solid-phase reaction during the firing process: when the two types of bricks are fired, solid solutions of Al₂O₃-Cr₂O₃ are formed between the particles and between the particles and the fine powder. This solid solution firmly connects the components, thereby significantly enhancing the mechanical strength of the products.
Thermal shock stability analysis
The thermal shock stability of chromite bricks is negatively correlated with the content of Cr₂O₃. That is, chromite bricks with a lower content of Cr₂O₃ have better thermal shock stability than those with a higher content. In industrial applications, the content of Cr₂O₃ in chromite bricks is usually controlled within the range of 12% - 20%. Especially for the AKZ type chromite bricks produced by adding a small amount of phase change modifiers, they not only maintain excellent high-temperature performance but also have more outstanding thermal shock stability.
Resistance to slag erosion
During actual use, the two materials exhibited significantly different erosion resistance characteristics. Corundum refractory bricks are prone to slag erosion. Slag can completely penetrate into the interior of the brick and seep through the pore channels to the surface, resulting in a brownish deteriorated layer on the surface of the brick. In contrast, chrome corundum bricks are almost not eroded by slag. The boundary between the brick and the slag is clear, and the slag penetrates very little into the interior. Both in terms of chemical melting erosion resistance to gasifying slag and in terms of erosion resistance, chrome corundum bricks are significantly superior to corundum bricks.
Application Areas and Selection Suggestions
1. Chromium corundum bricks are mainly used in areas with harsh conditions such as glass kiln linings, iron water pre-treatment devices, waste incinerators, and gasification furnace linings.
2. Corundum bricks are widely used in cracking furnaces and conversion furnaces in the petrochemical and fertilizer industries, as well as in various high-temperature kiln linings in the metallurgical industry such as steel furnaces and blast furnaces.
Both products have their own advantages: Chromium corundum bricks perform better in terms of high-temperature resistance and erosion resistance; corundum bricks have cost advantages. In actual engineering applications, the selection of corundum bricks should be made based on specific operating temperatures and economic requirements, and in appropriate positions and temperature ranges, to achieve the optimal balance between performance and cost.
