AZS Brick

AZS bricks, one of the fused cast brick, also known as electrofused AZS refractories, are named after their three primary oxide components in order of concentration – Alumina (Al2O3), Zirconia (ZrO2), and Silica (SiO2). The abbreviations A, Z, and S are taken from the first letters.

The numbers denote the percentages of Zirconia and Alumina. For example:

• AZS-33 refers to 33% ZrO2 electrofused refractory
• AZS-36 denotes 36% ZrO2 electrofused brick
• AZS-41 indicates 41% ZrO2 electrofused lining material

Higher Zirconia and Alumina contents impart improved corrosion resistance and thermal shock protection. But they also increase cost. The optimal AZS grade depends on the glass type, furnace design, and operating conditions. Proper brick selection maximizes service life and cost efficiency.

Raw Material of AZS Brick

AZS refractories are categorized by zirconia content into 33#, 36#, and 41# grades.

Key raw materials for quality electrofused AZS bricks include:

• High purity alumina (Al2O3 > 98.5%)
• Zircon sand (ZrO2 > 65.6%)
• Desiliconized zircon (ZrO2 > 85%)
• Soda ash (Na2CO3 ≥ 99%)
• Boron sand (B2O3 ≥ 37%)
• Rare earth oxides (Y2O3 ≥ 45%)

Equal parts alumina and zircon sand produce ~33% ZrO2 AZS-33. Higher zirconia AZS-36 and AZS-41 require desiliconized zircon addition. This also improves AZS-33 properties.

Alumina is derived by refining bauxite ores to remove silicates, iron, titanium and other oxides, achieving very high purity levels above 98% Al2O3.

Desiliconized zircon is produced by smelting zircon concentrates with carbon in an electric arc furnace to reduce silica.

Zircon, also called zirconium silicate, contains 67.1% ZrO2 and 32.9% SiO2. Its high 2550°C melting point, low expansion, and chemical resistance to liquids and acids make it ideal for AZS bricks.

Manufacturer Process of AZS Refractory Brick

1. Raw Materials Preparation: High purity raw materials like alumina, zirconia, silica and binders are weighed and mixed in proper proportions.
2. Forming: The powder mix is formed into desired shapes (usually bricks) by methods like uniaxial or isostatic pressing.
3. Drying: The shaped bricks are dried initially at 110-120°C to remove moisture.
4. Firing: The dried bricks are fired at high temperatures ranging from 1600-1750°C to sinter them. This results in densification and development of desired properties.
5. Cooling: The fired bricks are cooled slowly to room temperature to prevent development of cracks.
6. Finishing: The cooled bricks may be machined to specified dimensions and finishes if required.
7. Quality Checks: The finished AZS bricks are checked for properties like density, strength, microstructure etc.
8. Packing & Dispatch: Finally the checked bricks are packed and dispatched to customers.

Casting Processes for Electrofused AZS Bricks

• Conventional Casting – Uses risers and pours directly into molds, resulting in normal shrinkage cavities, typically used on furnace tops.
• Tilted Casting – Employs angled (30-35°) pouring to concentrate shrinkage to one end, leaving the other extremely dense. Common for pool walls.
• Near Non-shrinkage Casting – Vertical casting into oversized molds, then removing the top shrinkage section after annealing, creating high density. Also utilized for walls.
• Non-shrinkage Casting – Similar to near non-shrinkage technique but eliminates all shrinkage cavities. Used for walls and superstructure parts like throats.

Key advantages of directional solidification via tilted casting are minimized voids and maximized corrosion resistance. Near non-shrinkage and non-shrinkage processes further enhance density and durability through optimized mold design and post-casting machining.

Related articles:

1. Boosting Lifespan of AZS Refractory in Glass Furnace: Full Guide
2. Sintered vs Electrofused AZS Refractories: What’s the Key Differences