Zirconia Corundum Bricks (AZS Bricks): Composition, Properties and Applications

1. What Are Zirconia Corundum Bricks?

Zirconia corundum bricks, also known as AZS bricks, are electrofused refractory products made from alumina ( \((Al_{2} O_{3})\) , zirconia \((ZrO_{2})\) and a small amount of silica \((SiO_{2})\) by electric-arc melting. With their high zirconia content, they combine excellent resistance to glass-melt attack with high-temperature performance, making them the core refractory material for zones in direct contact with molten glass, such as the tank walls, tank bottom and throat of glass melting furnaces.

2. Composition and Phase Structure

Zirconia corundum bricks consist mainly of corundum (α-Al \((\alpha-Al_{2} O_{3})\) , baddeleyite \((ZrO_{2})\) ) and a small glassy phase. Zirconia provides extremely high resistance to glass-melt attack and is the key component determining brick life; the glassy phase fills the space between grains and exudes at melting temperature to fill pores, further reducing apparent porosity and increasing density.

3. Common Grades

Based on zirconia content, several grades are available, most commonly AZS33, AZS36 and AZS41. AZS33 contains about 33% \(ZrO_{2}\) , offers good cost-performance and is used in general furnace zones. AZS36 contains about 36% \(ZrO_{2}\) , provides balanced overall performance and is the most widely used. AZS41 contains about 41% \(ZrO_{2}\) , delivers the strongest corrosion resistance and is used in critical zones such as tank walls and the throat. The higher the grade, the better the corrosion resistance and the higher the cost; selection should match the working conditions and expected life.

4. Core Properties

Zirconia corundum bricks show excellent resistance to attack by glass melt and alkali vapor, which is key to extending furnace life. They have high high-temperature strength and resistance to mechanical wash-out, a dense structure with low porosity and strong penetration resistance, and remain physically and chemically stable above 1400 °C. Their glass-phase exudation behavior promotes self-densification and lowers the corrosion rate.

5. Main Applications

Zirconia corundum bricks are widely used for tank wall blocks, tank-bottom paving, the throat, the doghouse, electrode blocks and regenerator checker bricks of glass melting furnaces, and are also suitable for high-temperature furnace linings in the ceramics and metallurgical industries.

6. Selection and Support

Selection should determine the grade and brick profile according to the glass type, furnace temperature, contact zone and expected furnace life. It is recommended that a professional manufacturer provide working-condition analysis, brick-profile design and installation plans, ensuring precise brick dimensions and proper annealing for safe and longterm operation.