Characteristics of mullite refractories

Mullite refractories refer to refractories made of synthetic mullite as the main raw material and mullite as the main crystal phase. The production process of refractories is similar to that of high alumina products. The process points that need to be paid attention to are: accurate batching (particle gradation, ratio of aggregate and fine powder), uniform mixing, high-pressure molding, and full sintering. Firing temperature: when sintered mullite is used as aggregate

1550 ~ 1600 ℃; >1700 ℃ when using fused mullite as aggregate.

The chemical formula of mullite is 3AlO3 2SiO2, which is AI2O3-SiO2

The only stable compound in the binary system. Its melting point is (1890±90) °C, and it is crystallized with an orthorhombic crystal structure. The crystal structure is developed in the direction of the aluminum-oxygen octahedron sharing AlO6 parallel to the C axis, and the lateral direction is (Si, Al)O4 tetrahedron and AlO6 octahedron. A chain-like silicate mineral phase is connected by a shared edge. With the increase of Al3+ content, more oxygen vacancies will be generated in the crystal lattice, so mullite is an unsaturated network structure with the ordered distribution of alumina; its structure has large voids and is relatively loose.

Mullite is the raw material of high-grade refractories, with extremely low carbon residue, low porosity, low impurity content, high flexural strength, the high softening temperature under load, and high strength. Mullite has excellent thermal shock resistance and wears resistance. Its performance is widely used in glass kiln body lining bricks, mullite bricks, and hot blast stove bricks in large-scale smelting blast furnaces.