Usage of Alumina

Minerals containing Alumina represent some 15% of the earth’s crust. It is therefore an abundant material and virtually inexhaustable, unlike raw materials for many alloys developed for special applications. The combination of high thermal conductivity, low thermal expansion and high compressive strength leads to good thermal shock resistance, so Alumina is suited to furnace use as crucibles, tubes and thermocouple sheaths. High purity Alumina can be used up to 1700C and is gas tight up to 1300C. Few chemicals attack Alumina. Alumina also shows good electrical insulation at high temperatures, good wear resistance and high hardness, making it suitable for components such as ball valves, piston pumps and deep drawing tools.

Alumina tubes provide high strength at high temperatures and can be used for external winding of heating wire elements in applications exceeding 1550-1600°C. The tubes are manufactured from 99.7% recrystallized alumina, and are acid resistant, impervious and gas-tight. However, alumina is more susceptible to thermal shocks and consequently its use must be avoided in high thermal shock applications.

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