Silica Bricks

La description

Introduction 
Silica Bricks (also called silica refractory brick or silicate firebrick) are made of silica sand material, and the content of SiO2 is more than *4%. The Al2O3 content is lower than 1.0%, and the apparent porosity is under *2%. Silica bricks belong to acid refractory bricks, which have an excellent ability to resist acid slag and acid erosion. Silica bricks have good strength at high temperatures, high refractoriness under a load of about ********0℃, and a high softening point with temperature. Additionally, silica bricks are highly dense and have good heat conduction. The refractoriness can reach up to ***0°C, making them ideal high-temperature furnace construction materials. They are normally used in the iron & steel industry, and the super grade will be the necessary refractories in the glass industry.
 
The silica refractories are manufactured in multiple asymmetric shapes, which are normally keyed or interlocked with each other by means of tongues and grooves. Silica brick is widely used in the bottoms and walls of coke ovens.
Features
Silica refractories consist mainly of silicon dioxide (SiO2). They also contain calcium compounds formed from calcium hydroxide, which is used as a bonding agent.
The fired silica brick contains the crystalline SiO2 modifications cristobalite, tridymite, and some residual quartz. During the firing process, the lime reacts with the finest quartzite components to form wollastonite (CaO•SiO2). The matrix also contains very small quantities of calcium ferrite, hematite, magnetite, calcium olivine, and hedenbergite [calcium ferrous silicate,【CaFe(SiO3)2】, which are formed from impurities. These crystalline phases are the reason for the discoloration and spot formation on the fired bricks.
The transformed coarse grain generally consists of cristobalite, a proportion of residual quartz corresponding to the degree of transformation, and very little tridymite, whereas the fine-grained matrix is enriched with tridymite, glass, and wollastonite. The density of a fired silica brick is lowest when the degree of transformation is farthest advanced and attains the value of 2.*3 g/cm3 with complete transformation.
Porperties

• Good corrosion resistance to acid slag.
• Refractoriness of silica brick is not quite high, about ********0℃.
• Good stability under high temperatures.
• Poor thermal resistance performance.
• Good air tightness.
• True density of 2.*5g/cm³.
• Total volume expansion of 1.5~2.2% at the temperature of ***0℃.