White fused aluminum oxide of low expansion

The thermal expansion coefficient of white fused aluminum oxide is related to its quality. High quality white fused aluminum oxide is of lower thermal expansion coefficient. Low sodium WFA is featured with high Aluminu oxide content, high corundum phrase, low Na2O. It has a lower expansion rate than normal WFA even at high temperatures.

Normally, the thermal expansion coefficient of white fused alumina is 6.82 ×10^-6/℃ at a temperature of 1000 ° C.  And it increases with increasing temperature. However, for some usages that have strict requirements for material volume expansion, the thermal expansion coefficient should be as low as possible. The low sodium WFA produced by our company can greatly increase the proportion of alpha phase in the material. At the same time, the refractory temperature increases, the coefficient of thermal expansion decreases, and the stability improves. That feature is important especially for precision ceramic firing materials and investment casting. High temperature volume stability is beneficial for the dimensional accuracy of precision ceramics and precision castings. 

In the process of investment casting(lost foam process), refractory material for making shell  has to get high refractoriness and good volume stability. White fused aluminum with low expansion can replace zircon sand.