How are high-alumina refractories made from bauxite and kaolinitic clay?

High-alumina refractories are produced using a mixture of bauxite—a material containing aluminum hydroxide—and kaolinitic clays. To create these refractories, the raw materials are roasted, a process that transforms them into a mixture of synthetic alumina and mullite, an aluminosilicate mineral.1

The manufacturing process for these clay-based refractories generally follows methods similar to those used for traditional ceramics. The materials are typically formed into pre-shaped bricks using techniques such as press forming or extrusion. Once formed, the ware is dried and fired in long tunnel kilns. This firing process induces partial vitrification, or glass formation, which acts as a liquid-sintering process to bind the particles together.2

These refractories are defined by an alumina content ranging between 50 and 87.5 percent. They are valued for their robustness at high temperatures, volume stability, and abrasion resistance, making them suitable for use in environments such as blast furnaces and liquid-steel ladles.1