Properties, types and applications of sintered corundum in refractory materials
I. Performance characteristics of sintered corundum
Sintered corundum is a refractory clinker made of Al2O3 (γ-Al2O3) which is formed and then fired at high temperatures ranging from 1750 to 1900 °C. Its main characteristics:
- High fire resistance: The fire resistance of sintered corundum is more than 1800 °C and the melting point is 2040-2050 °C, so it can withstand very high temperatures. High strength: Due to the formation of α-Al2O3 crystals after high-temperature sintering and the presence of a large number of closed pores inside, the strength of sintered corundum is very high and the single grain strength is high.
- Excellent thermal shock resistance: The closed-cell internal structure provides improved thermal shock resistance and is stable at high temperatures.
- Corrosion resistance: Except for hydrofluoric acid and phosphoric acid, sintered corundum does not react with most alkalis and mineral acids and has excellent corrosion resistance. - High thermal conductivity: Excellent electrical properties at high temperatures.
- Good volume stability: Without any additives, sintered corundum has high purity, good volume stability and extremely low shrinkage after firing.
2. Types of sintered corundum The following types of sintered corundum are mainly distinguished:
- Ordinary sintered corundum: Made from calcined alumina, powdered into balls or hollow parts and sintered at high temperatures.
- Lightweight sintered corundum: It is a porous refractory material with a core-shell structure made of sintered transition aluminum oxide using foam technology. The pores of this porous corundum are mostly closed, and the density can be controlled by adjusting the amount of foaming agent.
- Microporous sintered corundum: It has numerous intra- and intercrystalline pores with sizes in the micrometer range, but its chemical composition is the same as that of sintered lamellar corundum. The pores of microporous sintered corundum give it a low bulk density, low thermal conductivity, and high strength. - Dense sintered corundum: A new type of high-density sintered corundum. Compared with ordinary sintered flake corundum, dense sintered corundum has a higher bulk density, lower apparent porosity, and better wear resistance and corrosion resistance.
- Sintered titanium corundum: It is a special type of corundum obtained by mixing TiO2 with aluminum oxide, then molding and sintering it at high temperature. Since the lattice constants of Al2O3 and TiO2 are close to each other, the substitution of Ti4+ by Al3+ is limited, which leads to lattice deformation and activates it, thereby greatly improving the sintering activity and reducing the sintering temperature. Sintered titanium corundum has high mechanical strength and excellent ballistic resistance.
3. Application of sintered corundum in refractory materials. Due to its excellent properties, sintered corundum finds wide application in the field of refractory materials.
- Sliding nozzle: Sintered corundum has good strength and thermal shock resistance, and is therefore an ideal material for sliding nozzles. - Die casting materials: Lightweight sintered corundum and microporous sintered corundum can significantly reduce thermal conductivity and improve thermal shock resistance due to their porous structure, which makes them suitable as die casting materials.
- Finished parts: The high fire resistance and wear resistance of sintered corundum make it the material of choice for finished parts. - Other refractory products: Refractory products with high requirements for corrosion resistance, such as: sliding plates, three-piece parts, air-permeable stones, casting materials for ladle impact zones, etc., the use of dense sintered corundum can greatly improve the service life and safety factor.
Due to its excellent performance properties and versatility, sintered corundum provides a wide range of applications in the field of refractory materials. With the continuous technological progress and continuous market expansion, the application fields of sintered corundum will continue to expand.
HOME