silica bricks

Silica bricks will expand at high temperatures, which is one of their inherent physical properties. Depending on the use conditions and environment, the expansion properties of silica bricks will affect their use in the furnace.

1. Expansion properties

Expansion point: During the baking process, silica bricks will have four crystal transformation points at 117℃, 163℃, 180~270℃ and 573℃. Among them, the volume expansion caused by quartz is the largest between 180~270℃.
Expansion range: The maximum expansion of silica bricks occurs between 100~300℃, and the expansion before 300℃ is about 70%~75% of the total expansion.

2. Thermal stability

Thermal shock stability: The biggest disadvantage of silica bricks is low thermal shock stability and low refractoriness, generally between 1690~1730℃, which limits its application range to a certain extent.
Performance at low temperatures: When the working temperature is lower than 600~700℃, the volume change of silica bricks is large, the resistance to rapid cooling and heating is poor, and the thermal stability is not good. If the coke oven works at this temperature for a long time, the masonry will easily crack and break.

3. Precautions for use

Temperature control: In order to prevent the silica bricks from being damaged due to excessive temperature fluctuations during use, it is necessary to strictly control the temperature changes in the furnace and avoid frequent rapid cooling and heating.
Repair method: If the silica bricks have undergone obvious expansion and deformation at high temperatures, it is recommended to inspect and evaluate them after cooling. If the deformation is serious, new silica bricks may need to be replaced.

4. Advantages of zero-expansion silica bricks

Thermal shock stability: Zero-expansion silica bricks have good thermal shock stability and a thermal expansion rate close to zero. After more than 30 cycles of water cooling at 1100 degrees Celsius, the products have no dimensional changes, no deformation, and no cracking. Repair operations can be carried out directly at high temperatures without stopping the furnace.
High temperature performance: The load softening temperature of zero-expansion silica bricks is high, reaching 1680℃. The chemical properties are good and stable at high temperatures. After the glass kiln is repaired, there is no impurity pollution, no erosion and peeling, and it is reliable for long-term use.

Conclusion

Silica bricks will expand at high temperatures, and this expansion may cause deformation of the brick body. If the deformation is not serious, it can continue to be used after cooling; but if the deformation is serious, it is recommended to replace new silica bricks. Zero expansion silica bricks are more suitable for use in high temperature and frequent temperature change environments due to their good thermal shock stability and near-zero thermal expansion rate.

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