Silica brick is a refractory product with silica as the main component and its content is more than 93%. It uses quartzite as raw material, adds a small amount of mineralizer, and is fired at high temperature. Its mineral composition is a complex structure of tridymite, cristobalite, a small amount of residual quartz and vitreous formed at high temperature.

Silica brick is an acidic refractory material, which is easily damaged by oxides such as Al2O3, Na2O2, K2O, etc. The high deformation temperature under load is an excellent characteristic of silica brick, which is close to the melting point of tridymite and cristobalite (1670 ° C, 1713 ° C), and fluctuates between 1640 and 1680 ° C.

When the silica brick is sintered again, irreversible volume expansion will occur due to the continuous transformation of the quartz remaining in the brick. Above 300 ℃ to close to the melting point (tridymite or cristobalite), the volume of silica brick is stable, and when heated to 1450 ℃, about 1.5%～2.2% of the total volume expansion, this expansion will Make the masonry joints close to ensure that the masonry body has good air tightness and structural strength.

The biggest disadvantage of silica bricks is poor thermal shock stability (about 1 to 4 times of heat exchange in water), followed by low refractoriness, generally between 1690 and 1730 ° C), which makes its application range subject to a larger limited.

Silica brick for glass kiln is a siliceous refractory product mainly used in tridymite for building high temperature parts of glass kiln. Silica bricks for glass kilns should have the following characteristics.

① The high temperature volume is stable, and the furnace body will not change due to temperature fluctuations. Due to the high softening temperature and low creep rate of silica brick, the glass kiln can keep the furnace body without deformation at 1600°C, and the structure is stable.

② No pollution to glass liquid. The main component of silica brick is SiO2, and if there is a block or surface melting drop during use, it will not affect the quality of the glass liquid.

③ Resistant to chemical attack. The silica brick of the upper structure is eroded by the gas containing R2O in the glass batch, and a smooth metamorphic layer is formed on the surface, which reduces the erosion rate and plays a protective role.

④ Small bulk density. The weight of the furnace body can be reduced.

Appearance is also specified in the standard as follows.

①When a crack crosses an edge, only one edge is allowed to cross, and cross-edge cracks are not combined for calculation.

② The length of the cracks on the silica bricks parallel to the working surface shall not be greater than 1/5 of the length of the common edge between the cracked surface and the working surface.

③ For spalling, bricks with a unit weight not greater than 20kg shall be assessed according to the crack index of the working face; bricks with a single weight not greater than 20kg shall be assessed according to the cracks on the non-working face.

④ For bricks with a single weight greater than 40kg, the technical conditions shall be agreed upon by both parties.