What material is high-alumina brick made of? What is the refractory temperature of high-alumina brick?
Publish Time:
2023-07-11
I. What is high-alumina brick made of?
High-alumina brick is a type of refractory material, and the main component of this refractory brick is Al2O3. High-alumina refractory bricks, i.e., aluminosilicate refractory products with a content of more than 48% of aluminum oxide (Al2O3), are made from bauxite or other raw materials with higher alumina content through molding and calcination. If the Al2O3 content is higher than 90%, it is called corundum brick.
Due to different resources, national standards are not completely consistent. For example, European countries stipulate that the lower limit of Al2O3 content for high-alumina refractory materials is 42%. In China, high-alumina bricks are usually divided into three grades according to the Al2O3 content: Grade Ⅰ - Al2O3 content > 75%; Grade Ⅱ - Al2O3 content is 60-75%; Grade Ⅲ - Al2O3 content is 48-60%.
It can also be classified according to its mineral composition, generally divided into five categories: low mullite (sillimanite), mullite, mullite-corundum, corundum-mullite, and corundum.
II. What is the refractory temperature of high-alumina brick?
The refractory temperature of high-alumina brick is not fixed and needs to be determined according to its alumina content.
1. If the alumina content exceeds 75%, it belongs to Grade 1 high-alumina brick, and the refractory temperature is between 1700 and 1800 degrees.
2. If the alumina content is between 60% and 75%, it belongs to Grade 2 refractory brick, and the refractory temperature is between 1600 and 1700 degrees.
3. If the alumina content is between 48% and 60%, it belongs to Grade 3 refractory brick, and the refractory temperature is between 1500 and 1600 degrees.
III. Characteristics of high-alumina brick
1. Refractoriness
The refractoriness of high-alumina brick is higher than that of clay brick and semi-silica brick, reaching 1750-1790℃, belonging to high-grade refractory materials.
2. Load softening temperature
Because the Al2O3 content is high and the amount of impurities is low in high-alumina products, less easily fusible glass is formed, so the load softening temperature is higher than that of clay bricks. However, because the mullite crystals have not formed a network structure, the load softening temperature is still not as high as that of silica bricks.
3. Slag resistance
High-alumina bricks contain more Al2O3 and are close to neutral refractory materials. They can resist the erosion of acidic and alkaline slags. Because they contain SiO2, their resistance to alkaline slag is weaker than their resistance to acidic slag.
IV. Uses of high-alumina brick
High-alumina bricks are mainly used for building blast furnaces, hot blast stoves, electric furnace roofs, blowers, reverberatory furnaces, and rotary kiln linings. In addition, high-alumina bricks are also widely used as regenerative checker bricks for open-hearth furnaces, stoppers for casting systems, and tuyere bricks. However, the price of high-alumina bricks is higher than that of clay bricks, so high-alumina bricks should not be used where clay bricks can meet the requirements.
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