Composition

• Corundum-mullite brick: Synthesized from corundum (α-Al2O3) and mullite (3Al2O3·2SiO2), typically with added fine phases to optimize thermal shock resistance.

• 95% alumina brick: ≥95 wt% Al2O3 with corundum as the primary phase; very low silica content, minimal glassy phase; sometimes bonded by ceramic or phosphate systems.

Key properties

• Corundum-mullite brick:
• Strength and refractoriness: High hot strength and refractoriness, suitable for 1600–1700°C service, depending on grade and atmosphere.
• Thermal shock: Better thermal shock resistance than pure corundum bricks, thanks to mullite’s lower thermal expansion and crack-deflection behavior.
• Wear/slag resistance: Good erosion resistance; silica-bearing mullite may reduce resistance in strongly basic slags compared to high-alumina.

• 95% alumina brick:
• Strength and refractoriness: Very high refractoriness and hot modulus of rupture; excellent creep resistance at elevated temperatures.
• Thermal shock: Generally inferior to corundum-mullite due to higher elastic modulus and thermal expansion.
• Wear/slag resistance: Outstanding abrasion resistance and chemical resistance in neutral/acidic environments; typically better against basic slags than mullite-bearing bricks with higher SiO2.

Thermal behavior

• Corundum-mullite: Lower thermal conductivity than pure corundum grades of similar density; better resistance to thermal cycling, reducing spalling risk in intermittent operations.

• 95% alumina: Higher thermal conductivity and elastic modulus; excels under steady high-temperature loads, less forgiving under frequent heat-up/cool-down cycles.

Typical applications

• Corundum-mullite brick:
• Burner blocks, kiln furniture supports, hot-face linings where thermal shock and moderate slag exposure coexist.
• Glass, ceramics, petrochemical equipment zones with repeated cycling or flame impingement.

• 95% alumina brick:
• High-wear, high-load, high-temperature zones such as furnace hearths, slide gates/ladles (as shapes), riser/impact areas, cement/lime transition zones with neutral/basic slags.

Selection guidance

• Choose corundum-mullite brick when:
• Thermal shock resistance is critical, temperature cycles are frequent, or there is mixed mechanical and thermal stress.
• Slightly lower thermal conductivity and better spall resistance improve lifetime.

• Choose 95% alumina brick when:
• Maximum hot strength, creep resistance, and abrasion resistance are required under steady high temperatures.
• Chemical environment favors very high Al2O3 with minimal silica (neutral to basic conditions).

Cost and processing

• Corundum-mullite: Often more cost-effective for shock-prone zones; microstructure engineered for crack tolerance.

• 95% alumina: Typically higher material cost due to premium tabular/fused alumina content and tighter impurity control; best ROI in severe service hot-face locations.

Quick comparison table

• Composition: Corundum + mullite vs ≥95% Al2O3 corundum.

• Thermal shock: Corundum-mullite better; 95% alumina lower.

• Hot strength/creep: 95% alumina higher; corundum-mullite high but lower than 95% alumina.

• Slag/chemical: 95% alumina stronger in neutral/basic; corundum-mullite good but watch basic slags.

• Wear/abrasion: 95% alumina generally superior.

• Best use: Cycling/flame zones (corundum-mullite) vs high-load, steady high-T, high-wear zones (95% alumina).