Silica Bricks for Sale
Refractory bricks with SiO2 content above 93% are called silica bricks. It is made of quartz stone as raw material, after crushing, adding an appropriate amount of binder, mineralizer, and part of siliceous clinker, after mixing, forming and drying, it is calcined in a kiln at 1400-1430℃. Rongsheng Silica Bricks for Sale as acidic refractory materials and have good resistance to acid corrosion. It has good thermal conductivity and high softening temperature under load, generally above 1620℃.
Raw Materials for Silica Bricks
- Raw material: silica or quartz sand.
- Binder: Lime milk or sulfite pulp waste liquid.
- Mineralizer: iron powder.
- Silica clinker: waste silica brick powder.
- Packaging of high-quality silica bricks: steel frame packaging, wooden box packaging, wooden pallet packaging, etc. The packaging of silica bricks can be made according to customer requirements.
The thermal conductivity of silica bricks increases with the increase of operating temperature, without residual shrinkage. In the oven process, the volume of silica brick increases with the increase of temperature. Therefore, silica bricks are ideal refractory products for coke ovens. Important parts of modern large and medium-sized coke ovens, such as the combustion chamber, chute and regenerator, are all built with silica bricks.
Uses of High-quality Silica Bricks
Silica bricks are classified into coke oven silica bricks, hot blast stove silica bricks, electric furnace silica bricks, and glass kiln silica bricks. According to the shape, it is divided into standard type, general type, and special type. Silica refractory bricks are characterized by strong resistance to acid slag erosion, high load softening temperature (1640～1670℃), good thermal shock resistance, and stable volume under high temperatures for long-term use. Mainly used for the coke oven carbonization chamber and combustion chamber partition wall, glass tank kiln roof and breast wall, acid steel furnace lining, etc. The development direction is high-silicon, high-density silicon bricks. Silica products composed of silica and other raw materials, such as chromium silica bricks, silicon carbide-silicon bricks, etc.
The Technical Performance of Silica Bricks
In the oven process, the maximum expansion of the silicon brick occurs between 100-300℃, and the expansion before 300℃ is about 70%-75% of the total expansion. The reason is that SiO2 has four crystal form transformation points of 117℃, 163℃, 180-270℃, and 573℃ during the oven process. Among them, the volume expansion caused by cristobalite is the largest between 180-270℃.
The key to determining the thermal stability of silica bricks for sale is true density. The true density is one of the important signs to determine its quartz conversion. The lower the true density of the silica brick, the more complete the quartz conversion, and the smaller the residual expansion during the oven process.
Among the silicon bricks, the true density of tridymite crystals is the smallest. The linear expansion rate is small, the thermal stability is better than cristobalite and quartz, the slag corrosion resistance is strong, the thermal conductivity is good, and the load softening temperature is high. It is the most stable form of quartz. Among the well-fired silica bricks, tridymite has the highest content, accounting for 50%-80%. Cristobalite comes next, accounting for only 10%-30%. The content of the quartz and glass phase fluctuates between 5% and 15%.
Appearance Requirements of Silica Bricks
The silica bricks produced in my country are divided into three grades: GZ-95, GZ-94, and GZ-93 according to physical and chemical indicators.
For the appearance of silica bricks, the relevant regulations are as follows:
- The crack is allowed to cross an edge. Cracks are allowed to cross two edges on the surface of irregular and special-shaped bricks with a side width less than 50mm.
- The depth of the missing corners of the pad and supporting bricks is not more than 10mm, the depth of the missing edges is not more than 8mm, and the diameter of the molten hole is not more than 10mm.
- For transverse cracks with a width of 0.11~0.50mm on the brick surface, the length is allowed to be no more than 50mm.
For the cross-section spallation of silica bricks, the relevant requirements are:
- The open-hearth furnace roof tiles are not allowed to have cross-section cracks;
- When the crack width of other bricks is not more than 0.1mm, the length is not limited;
- When the spall width of other bricks is 0.11~0.25mm, the length is not more than 50mm;
- When the spall width of other bricks is 0.26~0.50mm, the length is not more than 30mm;
- When the crack width of other bricks is greater than 0.5mm, it is not allowed;
- When the section cracks extend to the surface of the bricks, they are not allowed.
Except for the silica bricks for the top of the open hearth, the technical conditions of the bricks with a single weight of more than 15kg shall be negotiated by the supplier and the buyer.
What are the types and causes of cracks in silica bricks?
During the use of silica bricks for sale, when the working temperature is lower than 600-700℃, the volume of the silica bricks will change greatly, the performance of resisting rapid cooling and heating will be poor, and the thermal stability will not be good. If the coke oven is operated at this temperature for a long time, the masonry is easily broken and damaged.
In the process of making silicon bricks, like most sintered refractory bricks, Rongsheng silica bricks are produced by the semi-dry method and fired in a tunnel kiln. It is one of the main reasons for the increase of its scrap rate due to cracks in the production process.
Types and causes of silica brick cracks
The cracks of silica brick products can be divided into surface cracks and internal cracks, the latter is also called spalling. Surface cracks are divided into transverse cracks, longitudinal cracks, and network cracks. Silica brick is made of the compact body by semi-dry material press molding method. The cracks generated along the pressing direction of the bricks are transverse cracks, and the cracks generated perpendicular to the pressing direction of the bricks are vertical cracks. The surface of the silicon brick product is composed of several cracks, which are distributed in the form of spider webs, that is, web cracks.
Generally, for a standard silica brick, the pressing direction of the green body is generally the thickness direction. The molding process of silica brick products is essentially a process of making the particles in the blank dense and expelling air to form a compact body. After the brick is pressed and formed, it has the advantages of high density, high strength, small drying shrinkage and firing shrinkage, and easy control of product size. However, when the press molding process is not properly controlled, layered cracks perpendicular to the pressing direction will be formed during the pressing process. Therefore, the layered cracks inside the silicon brick, or spalling for short, are also longitudinal cracks.
Large spalls can be detected as soon as the bricks are formed or after the bricks have dried. However, the tiny spalls in the bricks can only be clearly detected after firing when the silicon bricks continue to expand with the action of thermal stress during the firing process. Silicon bricks containing crack defects, especially spalling, are prone to breakage, which can not be used and reduces the yield of silicon brick products.
Rongsheng Silica Bricks for Sale
Rongsheng is an experienced refractory manufacturer. Rongsheng’s refractory materials products have been sold to more than 60 countries and regions all over the world. Rongsheng’s silica bricks, fused silica brick, magnesia bricks, and high alumina bricks and other refractory brick products satisfy customers both in terms of product quality and product service. For more information about the sales of Rongsheng silicon bricks, please leave your specific needs on our page, or contact us directly by email.