Mullite refractory clay is a high-performance refractory material with mullite (3Al₂O₃·2SiO₂) as the main crystal phase, with excellent high-temperature stability, thermal shock resistance and chemical corrosion resistance.
1. Main characteristics of mullite refractory clay
High refractoriness: usually above 1750℃, even 1800℃ (depending on purity).
Low thermal expansion coefficient: excellent thermal shock resistance, able to withstand rapid cooling and heating.
Chemical inertness: resistant to acid, alkali and molten metal corrosion.
High mechanical strength: maintains good structural strength at high temperatures.
2. Composition and structure of mullite refractory clay
Main components: Al₂O₃ (50%~75%) and SiO₂ (25%~45%), which are formed into mullite crystals through high-temperature sintering.
Impact influence: impurities such as Fe₂O₃ and CaO will reduce the refractory performance and the content needs to be controlled.
3. Preparation process of mullite refractory clay
Raw material selection: kaolin, bauxite or a mixture of synthetic alumina and silica.
Sintering process: calcined at 1500~1700℃ to promote mullite reaction:
Molding method: pressing, casting or extrusion.
4. Application fields of mullite refractory clay
Metallurgical industry: furnace lining, ladle lining, iron ditch refractory materials.
Ceramic industry: kiln furniture (shed, sagger), high-temperature kiln lining.
Glass industry: regenerator checker bricks of glass melting furnace.
Chemical industry: high-temperature reaction vessel, catalyst carrier.
5. Advantages and limitations of mullite refractory clay
Advantages: lower cost than pure alumina refractory materials. Good high-temperature volume stability, not easy to crack.
Limitations: may soften at ultra-high temperatures (>1800℃). The sintering process needs to be carefully controlled to obtain high-purity mullite.
6. Common types of mullite refractory clay
Natural mullite clay: obtained by calcining high-alumina bauxite, with a mullite content of about 60%~70%.
Synthetic mullite: synthesized from chemically pure Al₂O₃ and SiO₂, with a higher purity (>90%).