Aluminosilicate Refractory Products

Aluminosilicate Refractory Products

 

refractories containing mainly alumina (A12O3) and silica (SiO2).

These products are obtained by roasting aluminosilicates at high temperatures in the region of 1250°-1450°C (up to 1750°C if aluminosilicates have a high content of alumina). The high temperature ensures transformation of the raw materials into the desired products. Aluminosilicate refractory products are divided into semiacidic (up to 28 percent A12O3, 65− 85 percent Si02), fireclay composite (28− 45 percent Al2O3), and high alumina-content composite (above 45 percent A12O3).

The first two groups are made of alumina and kaolin, mixed with pulverized fireclay. Quartz, usually in the form of sand, may be added to the semiacidic products. Fireclay products, which are based on kaolin, are known as kaolinic, while products containing more than 70 percent fireclay are called mnogoshamotnye (high fireclay content products). The high alumina-content products are obtained from rocks containing more than 45 percent A12O3 and also from artificial materials—technical alumina, electrocorundum. They are classified as follows: mullito-silica (45− 62 percent Al2O3), mullitic (62–72 percent), mullito-corundum (72–90 percent), and corundum composite (over 90 percent).

Refractory products of aluminum slilicates are made by compressing semidry powders (humidity content 6–9 percent) in mechanical or hydraulic presses. Some articles, especially those having a complicated shape, are made from powders of 17–22 percent humidity. They are roasted in industrial furnaces, mostly continuous tube furnaces. Products are of different shapes and sizes: bricks of simple form, plates, tubes, small and large articles of complicated shapes, and others.

Properties of aluminosilicate refractory products vary quite widely (see Table 1), depending on the raw material and finishing treatment.

Aluminosilicate refractory products are used for walls or linings of blast furnaces, crucibles for pouring steel into molds, cupola furnaces, fire-boxes, open-hearth furnaces (mainly outside), and flues, and in furnaces for bakeout of lime and cement and for melting of glass, as well as in other heating furnaces. These products are relatively wear-resistant, as far as acidic slags are concerned, and support heating-cooling cycles well. But they are less resistant toward basic slags. Products with high alumina content can be used for higher temperatures—for example, mullitic up to 1500–1600°C and corundum composite up to 1700–1800°C. Resistance to slags increases with alumina content. The most resistant against aggressive molten solutions are products of mullitic and of corundum composite.

Aluminosilicate refractory products constitute about 70 percent of all refractory articles produced.

REFERENCES

Poluboiarinov, D. N., V. L. Balkevich, and R. Ia. Popil’skii. Vysokoglinozemistye keramicheskie i ogneupornye materialy. Moscow, 1960.
Tekhnologiia keramiki i ogneuporov, 3rd ed. Edited by P. P. Budnikov. Moscow, 1962.
Ogneupornoe proizvodstvo: Spravochnik, vols. 1–2. Edited by D. I.Gavrish. Moscow, 1965.

N. IA. GOSIN and A. K. KARKLIT

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