1. Introduction to AZS bricks
AZS bricks (Alumina-Zirconia-Silica, i.e. alumina-zirconia-silica refractory materials) are the core refractory materials for key parts of glass kilns (such as melting pools, flow holes, and kiln sills). They are widely used due to their excellent resistance to glass liquid erosion.
- Main ingredients:
- Al₂O₃ (alumina) 45-50%
- ZrO₂ (zirconia) 30-41%
- SiO₂ (silicon dioxide) 11-15%
- Classification: According to the ZrO₂ content, they are divided into 33# (33% ZrO₂), 36# (36% ZrO₂), 41# (41% ZrO₂). The higher the zirconium content, the stronger the erosion resistance, but the higher the cost.
2. Core characteristics of AZS bricks
(1) Corrosion resistance
- ZrO2 reacts with glass liquid at high temperature to form a high-viscosity zirconium layer, which significantly slows down the erosion rate.
- It is especially suitable for highly corrosive melting environments such as soda-lime glass and borosilicate glass.
(2) High temperature resistance
- The softening temperature is ≥1700℃, and it can withstand the glass melting temperature of 1500-1600℃ for a long time.
(3) Thermal shock resistance
- Due to the phase change toughening effect of ZrO₂, AZS bricks have better thermal shock stability than ordinary high-alumina bricks.
(4) Glass phase seepage problem
- SiO₂ in AZS bricks will form a glass phase at high temperature, which may cause seepage on the brick surface (need to be controlled by optimizing the sintering process).
3. Application of AZS bricks in glass kilns
(1) Key application areas
Melting pool wall: 41# AZS, directly in contact with high-temperature glass liquid, the strongest erosion
Flow hole/kiln sill: 36# AZS, withstand high-velocity glass liquid scouring
Feeding port: 33# AZS, large temperature fluctuation, need to take into account cost
(2) Masonry precautions
- Expansion joint design: AZS bricks have a high thermal expansion coefficient (about 0.8%), and 1-1.5mm expansion joints need to be reserved.
- Avoid direct contact with alkaline refractory materials (such as magnesia bricks), which are prone to chemical reactions.
4. AZS brick selection and life-span influencing factors
(1) Selection principles
- High zirconium content (41#): used in areas with the most severe erosion (such as near the electrodes of electric melting furnaces).
- Medium zirconium content (36#): the best cost-effectiveness, suitable for most pool walls.
- Low zirconium content (33#): used in low temperature or secondary areas.
(2) Key factors for life
- Glass type: lead glass erosion > soda-lime glass > borosilicate glass.
- Furnace temperature: the erosion rate may double for every 50°C increase.
- Operating process: frequent furnace shutdowns or temperature fluctuations will accelerate brick peeling.
5. Common problems and solutions of AZS bricks
(1) Glass phase seepage
- Phenomenon: A bright layer appears on the surface of the brick, which may cause bubbles in the glass liquid.
- Solution: Use low glass phase seepage AZS bricks (such as the French SEPR ER series).
(2) Horizontal cracks
- Cause: Too fast heating or cooling stress concentration.
- Prevention: Strictly follow the oven curve to increase the temperature (recommended ≤5℃/h to 1200℃).
(3) Uneven erosion
- Countermeasures: Regularly rotate the pool wall bricks (such as 90° every 2 years) to extend the overall life.
6. Future development trends
- Chromium-free: Traditional AZS bricks contain a small amount of Cr₂O₃ (carcinogen), and environmentally friendly chrome-free AZS bricks (such as ZrO₂-Al₂O₃ composite bricks) are the research and development direction.
- Long life design: Improve corrosion resistance through nano coating or gradient structure (such as ZrO₂ outer layer + Al₂O₃ inner layer).
Conclusion
The performance of AZS bricks directly determines the life and production efficiency of glass kilns. The selection needs to comprehensively consider factors such as glass composition, furnace structure, and budget. It is recommended to communicate in depth with refractory suppliers and conduct laboratory erosion simulation tests when necessary.
Wechat Us 
