Silica bricks are refractory products primarily composed of silicon dioxide, with a content exceeding 93%. They are made from quartzite as the raw material, mixed with a small amount of mineralizing agents, and fired at high temperatures. Their mineral composition consists of coexisting phases, including tridymite, cristobalite, a small amount of residual quartz, and glassy material formed at high temperatures.
Silica bricks are acidic refractory materials, highly resistant to erosion by acidic slag, but they are prone to severe erosion by alkaline slag. They are easily damaged by the action of oxides such as Al2O3, K2O, and Na2O. They exhibit good resistance to oxides like CaO, FeO, and Fe2O3.
High deformation temperature under load is an excellent characteristic of silicon bricks, which fluctuates between 1640°C and 1680°C, close to the melting points of quartz (1670°C) and tridymite (1713°C). During re-firing, irreversible volume expansion occurs due to the continued transformation of quartz residue within the bricks. In the range above 300°C to near the melting point (quartz or tridymite), the volume of silicon bricks remains stable. When heated to 1450°C during use, there is approximately a 1.5% to 2.2% overall volume expansion, which ensures tight joints and guarantees good airtightness and structural strength of the masonry.
The significant drawback of silicon bricks is their low thermal shock resistance (about 1-4 cycles in water exchange), followed by insufficient refractoriness (generally between 1690-1730°C), which greatly limits their range of application.
Silica bricks are primarily used in coke ovens, glass melting furnaces, acid steelmaking furnaces, and other thermal equipment.
When using silicon bricks, please note the following two points:
(1) Silicon-based products experience sudden expansion due to crystal phase transformation at temperatures of 200-300℃ and 573℃, so it is not advisable to heat up too quickly below 600℃ during the drying process. Additionally, avoid sharp temperature changes when cooling down below 600℃.
(2) Avoid contact with alkaline slag as much as possible.
