In high-temperature industries such as steel smelting, cement production, and glass manufacturing, refractory bricks, as the foundation for kiln linings, silently endure the scorching heat and chemical erosion of temperatures exceeding thousands of degrees Celsius. They are not a single material, but a vast family. So, how many types of fire bricks are there? They can be classified in various ways. But if classified by chemical and mineral composition, they can be mainly divided into the following categories:
1. Silica-based refractory bricks
First, there are silica-based refractory bricks, primarily composed of silica. These are highly acidic, with a refractoriness of 1690-1730℃, perfectly resisting the erosion of acidic slag, and are therefore commonly found in acidic environments such as coke ovens and glass melting furnaces. However, their weakness lies in their poor resistance to rapid heating and cooling. And their vulnerability to corrosion from alkaline substances.
2. Aluminosilicate fire bricks
Second, there are aluminosilicate fire bricks, primarily composed of alumina. This is the most widely used group of refractory bricks, which are further categorized based on alumina content, ranging from clay brick (Al₂O₃ 30%-48%), high-alumina brick (Al₂O₃ >48%) to corundum brick (Al₂O₃ >90%). Higher alumina content results in better refractoriness, erosion resistance, and structural strength, making them suitable for critical components such as boilers and blast furnace hot blast stoves.
3. Basic refractory bricks
Furthermore, there are basic refractory bricks with magnesia as their core, such as magnesia brick and magnesia-chrome brick. These are alkaline and have excellent resistance to alkaline slag, acting as “guardians” of steelmaking converters, electric arc furnaces, and non-ferrous metal smelting furnaces. However, their susceptibility to hydration requires them to be kept dry during storage and construction.
4. Carbonaceous refractory bricks
In addition, there are distinctive carbonaceous refractory bricks (such as carbon brick and graphite brick), indispensable in blast furnace hearts and calcium carbide furnaces due to their excellent thermal conductivity, high-temperature resistance, and impermeability; and highly dense, high-performance zirconium and chromium-based special brick, which often plays a role under more demanding specific operating conditions.
In summary, there are many types of refractory bricks, each with unique chemical properties and physical characteristics. From acidic silica bricks to basic magnesia bricks, and then to neutral carbon bricks. They together constitute the “golden shield” of modern industry. Choosing which type to use is not arbitrary; it requires engineers to precisely match the materials according to the furnace temperature, atmosphere, and corrosive media, much like preparing a reagent, in order to build the most robust “Great Wall of Flames.”