High-alumina bricks are a type of shaped refractory material produced by firing refractory clay or other refractory raw materials at high temperatures; they belong to the aluminosilicate product family. Refractory bricks are inorganic non-metallic materials available in various types, including high-alumina, clay, magnesia, corundum, mullite, and silicon carbide bricks. Due to their superior refractory properties, high-alumina bricks are widely used among the various types of refractory bricks. According to standards for high-alumina refractory materials, the Al₂O₃ content is the key classification criterion. Specifically, high-alumina bricks are categorized into three grades: Grade I (Al₂O₃ content > 75%), Grade II (Al₂O₃ content between 60% and 75%), and Grade III (Al₂O₃ content between 48% and 60%).
As a type of refractory material, high-alumina bricks are primarily composed of Al₂O₃. Compared to clay bricks and semi-silica bricks, high-alumina bricks exhibit higher refractoriness and are thus classified as high-grade refractory materials. Their high Al₂O₃ content gives them near-neutral characteristics, enabling effective resistance to erosion by both acidic and basic slags. However, it is worth noting that despite containing SiO₂, their resistance to basic slag is slightly inferior to their resistance to acidic slag. Based on Al₂O₃ content, high-alumina bricks can be further subdivided into grades such as 55, 65, 75, and 80.
High-alumina bricks are classified into various grades based on their Al₂O₃ (aluminum oxide) content. Among them, corundum bricks-with an aluminum content of 90% or higher-represent the highest tier of high-alumina bricks. "Special grade" high-alumina bricks contain at least 85% aluminum, while Grade I bricks contain over 75%; Grade II and Grade III bricks contain at least 65% and 55% aluminum, respectively. These different grades offer varying refractory properties to meet diverse industrial requirements. High-alumina bricks are a type of aluminosilicate refractory product characterized by an aluminum oxide (Al₂O₃) content exceeding 48%. When the Al₂O₃ content reaches 90% or higher, they are classified as corundum bricks-a variety of high-alumina brick that offers exceptional refractory performance. It is worth noting that standards for high-alumina bricks may vary across countries due to differences in available resources.
For instance, in European countries, the minimum Al₂O₃ content for high-alumina refractory materials is set at 42%. In China, however, high-alumina bricks are typically categorized into three grades: Grade I bricks contain over 75% Al₂O₃; Grade II bricks contain between 60% and 75% Al₂O₃; and Grade III bricks contain between 48% and 60% Al₂O₃.