High Alumina Brick

High Alumina Bricks are dense refractory bricks with Al₂O₃ content ≥48%, engineered for high-temperature industrial furnaces and kilns. With refractoriness of 1770–1850°C, cold compressive strength ≥39 MPa, and strong resistance to molten slag erosion, high alumina bricks are the most widely used refractory lining material in steel blast furnaces, cement rotary kilns, non-ferrous metal smelters, and waste incineration plants. They are manufactured by pressing high-purity bauxite and clay blends, then firing at 1400–1800°C in tunnel kilns to form a dense mullite-corundum crystalline structure.

Grades & Technical Specifications

High Alumina Bricks are classified by alumina content into standard grades. Each grade is defined by a distinct mineral phase composition — mullite (3Al₂O₃·2SiO₂) at lower grades, corundum (α-Al₂O₃) at higher grades — which determines refractoriness, slag resistance, and mechanical strength. The table below lists the full physicochemical parameters for grades SK-36 through SK-42, manufactured to GB/T 2988 standard.

Higher alumina grades (SK-40, SK-42) develop corundum as the primary crystalline phase, providing superior refractoriness under load and slag corrosion resistance. Lower grades (SK-36, SK-37) retain mullite-dominant structures that offer excellent thermal shock resistance at moderate temperatures.

Grade Selection Guide

Selecting the correct grade requires matching the brick's refractoriness, slag resistance, and thermal shock resistance to the specific furnace zone and process chemistry. The guide below maps common industrial applications to the recommended grades.

High Alumina Bricks vs Other Refractory Bricks

High Alumina Bricks occupy the mid-to-high temperature range of the refractory brick spectrum. The comparison below shows how they differ from fireclay bricks (lower temperature) and silica bricks (glass furnace specialty) in key performance parameters.

High Alumina Bricks are the most versatile refractory bricks for furnaces operating at 1400–1700°C. Fireclay bricks suit lower-temperature zones (≤1400°C) where cost is the primary concern. Silica bricks are specialized for glass furnaces and coke ovens where their excellent thermal shock resistance above 600°C and compatibility with acidic glass melt are required.

Industrial Applications

High Alumina Bricks are used across all major high-temperature industries. The application notes below specify the recommended grade and key performance factor for each industry.

Steel Industry

Blast furnaces, hot blast stoves, steel ladles, and tundishes require refractory linings that withstand 1500–1800°C temperatures and molten iron/slag erosion. SK-40 and SK-42 grades with corundum phase structure provide the highest slag corrosion resistance for blast furnace bosh and steel ladle working linings. For hot blast stove domes and upper checkers, SK-38 offers excellent creep resistance at constant thermal load. Highland's high alumina refractory bricks have extended blast furnace lining life by up to 40% for European steel clients through dense mullite-corundum structures that resist slag penetration.

Cement & Lime Industry

Cement rotary kiln burning zones (1600–1750°C) face severe alkaline clinker corrosion and thermal cycling. SK-38 and SK-40 grades form a stable coating with burnt clinker that protects the brick from direct chemical attack. Transition zones with rapid temperature swings use SK-36 and SK-37 grades that maintain thermal shock resistance. Highland provides custom-shaped alumina lining bricks for irregular kiln sections, eliminating the need for costly equipment modification — a Southeast Asian cement client saved $50,000 in modification costs using tailored brick dimensions.

Non-Ferrous Metal Industry

Copper and aluminum smelters (1200–1600°C) deal with corrosive multi-metal slags that cause rapid lining degradation. SK-38 and SK-40 grades blended with anti-corrosion additives achieve 50% higher acid/alkali resistance than standard alumina bricks. The dense corundum structure resists both chemical corrosion and thermal shock from batch charging. A South American aluminum smelter reported a 35% reduction in lining failure rates after switching to Highland's high-purity high alumina fire bricks, cutting annual maintenance costs by $20,000.

Waste-to-Energy & Incineration

Waste incinerators (800–1200°C) face acidic flue gases and alkali salt deposits that erode furnace linings. SK-36 grade with low apparent porosity (≤24%) blocks gas infiltration and resists acid condensation. Service life of 18–24 months is achievable with proper grade selection and installation, compared to 6–8 months for standard fireclay bricks. A European waste-to-energy plant reduced replacement frequency from twice yearly to once every two years using Highland's low-porosity high alumina bricks.

Glass & Ceramics

Glass tank regenerators and ceramic kilns use SK-38 high alumina bricks for alkali vapor resistance and thermal cycling stability. For direct contact with molten glass, fused-cast AZS blocks are recommended instead — high alumina bricks serve in backup and regenerator zones where alkali vapor, not molten glass, is the primary corrosive agent.

Production Process & Quality Control

Highland Refractory manufactures high alumina bricks through a controlled six-stage process under ISO 9001:2015 certification:

1. Raw material inspection: High-purity Chinese bauxite (Al₂O₃ ≥85%) is tested for alumina content, iron oxide, and alkali impurities before acceptance. Clay binders are checked for plasticity and firing shrinkage.
2. Batching & mixing: Calibrated raw material ratios are blended in weight-controlled batches. Particle size distribution is engineered for optimal packing density — coarse, medium, and fine fractions are combined to minimize porosity.
3. Forming: Hydraulic presses (400–1000 ton capacity) compact the batch at 150–250 MPa. SK-40 and SK-42 grades require higher pressing pressure to achieve target bulk density. Standard and custom-shaped molds produce bricks to specified dimensions.
4. Drying: Green bricks are dried at 110–150°C for 24–48 hours to remove mechanical moisture. Drying shrinkage is monitored to prevent cracking.
5. Firing: Bricks are fired in tunnel kilns at 1400–1800°C depending on grade. Soaking time at peak temperature ensures complete mullite and corundum phase formation. Firing atmosphere is controlled to prevent oxidation of iron-bearing impurities.
6. Testing & sorting: Every batch undergoes cold crushing strength, apparent porosity, bulk density, and reheat linear change testing. Bricks are sorted by dimensional tolerance (±1mm standard, ±0.5mm precision). Full test certificates accompany each shipment.

This process ensures consistent quality across all grades — refractoriness ≥1770°C, cold crushing strength ≥39 MPa, and reheat linear change within +0.1 ~ −0.5% (1400°C×2h) for standard SK-36 grade. Higher grades exceed these minimums as specified in the technical table above.

Standard & Custom Sizes

Highland supplies high alumina bricks in both standard and custom dimensions:

• Standard straight brick: 230 × 114 × 65 mm — compatible with most conventional furnaces
• Large straight brick: 230 × 114 × 75 mm, 250 × 123 × 65 mm
• Wedge bricks: For cylindrical furnace walls (rotary kilns, ladles) — specify inner/outer radius
• Arch bricks: For furnace roofs and arches — specify span and rise
• Custom shapes: Provide kiln structure drawings — we adjust dimensions, thickness, edge angles, and special features (holes, grooves, chamfers) to match your equipment

Custom-shaped bricks eliminate the need for equipment modification during relining. Tolerance: ±1 mm on standard bricks, ±0.5 mm on precision-ground bricks for gas-tight joints.

Packaging & Shipping

• Packaging: 5-layer corrugated cartons (20–25 bricks per carton) on 1200×1000 mm IPPC-compliant pallets, wrapped with stretch film. Fragile grades (insulating bricks) receive additional moisture-proof liners and foam padding.
• Export shipping: 20ft / 40ft containers with 15 cm spacing between pallets for ventilation. Desiccant bags and shipping marks applied per destination requirements.
• Loading & unloading: Forkifts with rubber pads to prevent edge damage. Damage rate ≤0.5%.
• Documentation: Commercial invoice, packing list, certificate of origin, and ISO/CE test certificates provided for customs clearance.
• After-sales: Free replacement for transit damage (photo verification within 24 hours). Real-time shipment tracking. 24-hour response for urgent orders.

Highland Refractory has supplied high alumina bricks to steel plants, cement plants, and smelters in over 40 countries since 1990. With a 1,100-person workforce and complete production lines, we deliver standard orders in 35–60 days and custom-shaped orders in 45–75 days. ISO 9001:2015 certified, CE-compliant for European markets.

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