White fused alumina (also known as white corundum, white fused aluminum oxide, electro fused alumina )is a crystal of high purity Al2O3. Natural corundum is a gem formed by the crystallization of Al2O3, the fused corundum used for Industrial applications is generally artificially synthesized.
There are two types of white fused alumina commonly used in casting coatings:
- White fused alumina: The content of Al2O3 is greater than 97%. White corundum is made from high purity alumina powder after being crushed and washed, smelted in an arc at a high temperature of over 2000 degrees, and then cooled. After crushing, shaping, and magnetic separation Deironing, sieving into various particle sizes. Usually, -200mesh,-300 meshes can be used for casting coatings. The melting point is 2250 degrees and the refractoriness is 1900 degrees.
- Brown fused alumina: Al2O3 content is greater than 92%. Brown fused alumina is made by mixing bauxite with high alumina content into carbon materials such as anthracite or coke and iron filings and smelting in an electric arc furnace. The melting point and refractoriness are similar to those of white fused alumina.
In foundry coatings, white fused alumina is more widely used, mainly due to the high purity of Al2O3 and small quality fluctuations, while brown fused alumina has a wide range of index control, which is easy to cause quality fluctuations, which affects the refractoriness and would cause sticking sand on castings.
White fused alumina is a kind of refractory material with very high refractoriness, suitable for coating of large steel castings, especially alloy steel castings. The characteristics of white fused alumina include the following features:
l High refractoriness, can reach above 1800 degrees
l Good chemical stability
l It has strong resistance to acids and alkalis, and does not change in oxidants, reducing agents and various metal liquids. Aluminum, manganese, iron and silicon do not react with it, so it is more suitable for alloy steel castings.
l It is weakly alkaline or neutral at high temperature.
It can be seen that, as a high purity alumina refractory material, white fused alumina can be widely used in lost foam casting coatings, precision casting coatings and other fields.
