What is the performance of high alumina castables in high-temperature environments?

The performance of high aluminum castables is excellent in high temperature environments, and its core advantages stem from high aluminum content (usually Al ₂ O3 ≥ 55%) and optimized material design. The specific performance characteristics and mechanisms are as follows:

1、 High temperature stability and fire resistance

refractoriness

The fire resistance of high alumina castables is generally ≥ 1700 ℃, and some corundum based formulas (Al ₂ O3 ≥ 90%) can reach above 1780 ℃. The high melting point (>2000 ℃) of high alumina clinker and corundum aggregate is the basis for high temperature stability.

Load softening temperature

The load softening temperature with a deformation of 4% is usually between 1400~1600 ℃, which is better than ordinary clay based castables (such as low cement high alumina castables with a load softening temperature of 1500~1550 ℃).

2、 High temperature strength and creep resistance performance

mechanical strength

The compressive strength at room temperature is 30~80MPa, and after heat treatment at 1400 ℃, the high-temperature flexural strength still maintains 3~15MPa.

Ceramic bonding (such as mullite phase) is formed at high temperatures, and the strength increases instead of decreasing with increasing temperature.

Creep resistance

At 1400 ℃ and 0.2MPa load, the creep rate is less than 1.0% after 50 hours, thanks to the low melting phase and dense structure.

3、 Thermal shock resistance

Resistant to sudden temperature changes

It can withstand more than 30 cycles of water cooling at 1100 ℃ due to its low thermal expansion coefficient (5.0~7.0 × 10 ⁻⁶/℃) and microcrack toughening mechanism.

Volume stability

After burning, the rate of linear change is ≤± 0.5% (1600 ℃) to avoid high-temperature shrinkage cracking.

4、 Chemical resistance and wear resistance

Anti slag erosion

High Al ₂ O3 content (especially ≥ 75%) has strong resistance to acidic slag, and adding chromium oxide micro powder (Cr ₂ O3) can enhance the ability to resist alkaline erosion.

wear resistance

The room temperature wear amount is ≤ 10 cm ³ (ASTM704C standard), and the wear resistance is enhanced by silicon carbide or corundum aggregates. It is suitable for high wear parts such as cement kiln coal injection pipes.

5、 Thermal properties

thermal conductivity

At 1000 ℃, the thermal conductivity is 1.5~2.5 W/(m · K), balancing insulation and heat conduction requirements.

Adiabatic property

Low porosity (visible porosity<20%) reduces heat loss and is suitable for high-temperature energy-saving equipment.

6、 Technological development trends

Low cement/non cement: using binders such as silica sol and polyaluminum oxalate to reduce CaO content and improve high-temperature performance.

Nano modification: Nano alumina refines grain boundaries, improves sintering and thermal shock resistance.