Curious about how high-temperature calcined brown fused alumina achieves its unique characteristics? Let’s unravel the details of the production process that transforms standard brown fused alumina into its superior, calcined version. This journey involves precise control of heat, chemical reactions, and innovative kilns.

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Production Process: Converting Brown to Blue

High-temperature calcined brown fused alumina is produced by heating high-quality brown fused alumina to 1300°C. The goal is to convert β-Al2O3 into α-Al2O3 crystals and dissolve Ti2O3 into the α-Al2O3, forming TiO2 nuclei. The resulting blue hue from this transformation gives the material its name, blue-fired fused alumina.

The calcination process can be divided into two main stages based on temperature:

1. 0℃ to 900℃: At these temperatures, TiO2 crystals develop slowly due to their small growth coefficient.
2. 900℃ to 1300℃: At higher temperatures, Ti2O3 quickly dissolves into the α-Al2O3 crystals and reacts with O2 to form TiO2. The TiO2 encapsulates the α-Al2O3 grains. TiO2 nuclei grow to 0.015-0.15μm, scattering blue light while absorbing other wavelengths, creating the blue color.

Interested in understanding the chemistry behind this transformation? Learn more here about the process.

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Calcination Methods: Shuttle and Tunnel Kilns

There are various ways to calcine brown fused alumina:

1. Shuttle Kiln: An intermittent firing kiln, similar to a matchbox in structure. The kiln car moves back and forth, giving it the name “shuttle kiln.” This kiln is known for its flexibility and the ability to accommodate a wide range of products. However, because it operates intermittently, it experiences significant heat loss. Newer, energy-efficient designs have improved this issue.
2. Tunnel Kiln: A long, linear tunnel with fixed walls and an arched roof. Kiln cars run on tracks at the bottom. The firing equipment creates a high-temperature zone in the middle. Hot gases flow toward the kiln head while preheating incoming products. Cold air cools the products at the back of the kiln, and warm air is used for drying green bodies.

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Shuttle or tunnel kiln? Here’s a comparison to help you choose the best for your needs.

Calcination Precautions

Maintaining a consistent temperature for 5-6 hours stabilizes the abrasive’s properties before cooling. The temperature curve must be reasonable to avoid rapid heating or cooling, which could damage the abrasive’s toughness. After calcination, the material undergoes cooling, loosening, particle removal, air washing, magnetic separation, and screening to meet the desired grain size distribution.

Advantages of High-Temperature Calcined Brown Fused Alumina

High-temperature calcined brown fused alumina provides these benefits:

1. Improved Magnetic Induction: The abrasives transition from weak to strong magnetic induction, making it easier to remove magnetic substances.
2. Enhanced Hydrophilicity: Hydrophilicity improves by 2-3 times.
3. Improved Recovery: High temperatures repair cracks caused by heavy-load crushing.
4. Increased Bonding Strength: Sintering vaporizes impurities on the abrasive surface, increasing bonding strength.
5. Improved Durability: High-temperature abrasives are 40% more durable than standard brown fused alumina.

Curious how these advantages translate to better performance? Find out how it can benefit your business.

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Conclusion

High-temperature calcined brown fused alumina is produced through a complex process that transforms its properties to enhance its performance. Understanding its production helps us appreciate its superior quality, making it a prime choice for high-quality abrasive applications.