I. Classification by Application and Shape
1. Mullite Castings
Properties: Mullite is used as a filler or main component and is produced by casting. It is suitable for lining furnaces with complex shapes (e.g., curved surfaces).
Applications: Lining of high-temperature equipment such as metallurgical furnaces, cement kilns, and glass furnaces.
2. Properties of Mullite Ceramic Products:
The main crystal phase is mullite.
Mullite is divided into ordinary mullite porcelain (with an impure glass phase) and high-purity mullite porcelain (without a glass phase).
The flexural strength of high-purity products reaches 570 MPa at 1300 °C, and the impact toughness is improved by 1.6 times. Applications: High-temperature furnace equipment (trays, shelves), thermocouple protection tubes, crucibles, etc.
II. Density Classification
1. Light Mullite Bricks:
High porosity (low density)
Low thermal conductivity, excellent energy savings
Manufacturing Process:
Additive firing (main process): After firing, sawdust/polystyrene is added to form pores.
Foaming Process: Liquid foam, created using a blowing agent, is poured in. Complex but high-quality process.
Applications: Insulating layer for hot-air furnaces, glass crucibles, ceramic tunnel kilns, etc.
2. Heavy mullite bricks
Properties:
High density (bulk density ≥ 2.65 g/cm³)
Fire resistance > 1790 °C
Fire resistance under load 1600–1700 °C
Excellent thermal shock resistance
Classification:
Sintered mullite bricks: Mainly made of high-alumina clinker, high strength
Fused mullite bricks: Produced by the electric smelting process, large particles, excellent thermal resistance
Applications: Furnace linings with direct flame contact (oil cracking furnaces, metallurgical blast furnaces, etc.)
III. Classification by Operating Temperature Type 1350:
Heat-resistant basic type Type 1450:
For medium and high temperatures Type 1550:
High-temperature type (Al₂O₃ content 71.8%–77.3%)
IV. Classification of Composite Materials
1. Mullite-Corundum Material
Combines the high hardness of corundum with the heat resistance of mullite.
Applications: Ladle covers, desulfurization gun linings
2. Mullite-Silicon Carbide Material
Silicon carbide improves wear resistance and thermal conductivity.
Applications: Highly stressed furnace parts
3. Mullite-Magnesium-Aluminum-Spinel Material
Spinel introduces microcracks into the structure, significantly improving heat resistance.
*Summary of Key Benefits
With its high heat resistance of over 1800°C, it is suitable for industries such as metallurgy, ceramics, glass, and cement.
With its extremely low coefficient of thermal expansion (4.5 × 10⁻⁶/℃), it is suitable for high-temperature precision parts.
Excellent heat resistance (rapid cooling and rapid heating up to 100 times). Suitable for parts such as furnace doors and viewing windows.
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