High alumina bricks are aluminum silicate refractory products containing more than 48% aluminum oxide (A203). If the content of A203 is higher than 90%, it is called corundum brick, because the standards of different countries are not completely consistent due to different resources. For example, European countries have stipulated that the lower limit of Al203 content for high-aluminum refractories is 42%. In China, according to the content of Al203 in high alumina bricks, it is usually divided into three grades: Class I—A1203 content>75%; Class II—A203 content of 60-75%; Class III—A1203 content of 48-60%.
A neutral refractory with an alumina content of more than 48%. It is formed by forming and calcining alumite or other raw materials with higher alumina content. High thermal stability, tolerance above 1770℃, good slag resistance, used for the lining of steel-making electric furnaces, glass melting furnaces, cement rotary furnaces, etc.
High-load, soft, low-creep high-alumina bricks are high-grade refractory materials made of special grade bauxite, fused corundum, and fused mullite as the main raw materials. This product has the advantages of small high-temperature creep, strong corrosion resistance, and good thermal shock stability. It is suitable for large and medium-sized hot blast stoves. It opens up the next step for the localization of high-quality and high-grade imported refractories in my country's new hot blast stoves. The road to success has been included in the national "Spark Plan" project.
According to different resource conditions and product requirements, the following types of raw materials can be used. High alumina bricks made of hydrated alumina minerals (monohydrate, gibbsite, etc.)
High alumina bauxite which is the main composition: sillimanite group minerals (including kyanite, andalusite, sillimanite, etc.) artificial synthetic elements, such as industrial oxidation residue, synthetic mullite, fused corundum, etc. China High Bauxite is rich in resources and excellent in texture. The production areas are mainly distributed in Shanxi, Henan, Hebei, Guizhou, Shandong and other places. The high bauxite produced is mainly monohydrate (α-AI203·H20) and kaolinite A mixture of two minerals.
Characteristic
a. Refractoriness The refractoriness of high alumina bricks is higher than that of clay bricks and semi-silica bricks, reaching 1750-1790℃ and belongs to advanced refractory materials. To
b. Load softening temperature, because high aluminum products have high A1203, less impurities and less fusible glass, so the load softening temperature is higher than clay bricks, but because mullite crystals do not form a network structure, the load is softened The temperature is still not as high as silica bricks.
c. There are more A1203 in the slag-resistant high alumina brick, which is close to the neutral pre-fire material, and can resist the invasion of acidic slag and alkaline slag. Since the total contains Si02, the resistance to alkali is better than that of acid slag The ability is weaker.
Craftsmanship
The production process of high alumina bricks and multi-clinker clay bricks is similar, the difference is that the proportion of clinker in the ingredients is higher, which can be as high as 90-95%. The clinker needs to be sorted and sieved to remove iron before crushing, and the firing temperature The strand height is generally 1500-1600℃ when high alumina bricks such as I and II are fired in a tunnel kiln. Production practice in China has proved that before crushing, high-aluminum clinker is strictly sorted and classified, and stored in tiers. The use of bauxite clinker and combined clay fine grinding method can improve product quality.
Purpose
Mainly used for lining of blast furnaces, hot blast furnaces, electric furnace tops, blast furnaces, reverberatory furnaces, and rotary kilns. In addition: high-alumina bricks are also widely used as open-hearth regenerative checker bricks, plugs and nozzle bricks for pouring systems. However, the price of high alumina bricks is higher than that of sticky bricks, so it is not necessary to use high alumina bricks where clay bricks can meet the requirements.
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