The Working Temperature of Silica Insulation Bricks

Silica insulation brick is a type of insulating brick with a SiO2 content of more than 91%. It is made of silica stones. Besides good insulation properties, it maintains the properties of silica bricks such as high softening temperature under load and volume expansion during the heating process which can improve the integrity of the furnaces. 

The silica insulation brick is made of crushed silica stones as the raw material with addition of waste silica bricks, mineral agents and combustion materials. The raw materials are mixed into mortar by adding water and then molded by hand or machine. The bricks are dried until the residual moisture content is less than 0.5% and then loaded into the kiln and fired. In order to prevent cracks caused by the drastic volume expansion caused by the crystalline transformation of SiO2, the temperature should be risen slowly. 

 

The Chinese Metallurgical Industry standard has the following requirements for the bricks: bulk density≦1.2g/cm3, Cold Crushing Strength≦3.43MPa, refractoriness≥1670℃, softening temperature under load (0.098MPa)≥1560℃, SiO2≥91%. 

 

Silica insulation brick is used under 1560℃ and should not directly contact corrosive gases. Since silica dust has great harm to health and has more complex manufacturing process than that of fireclay insulation brick or high alumina insulation brick, it accounts a small proportion of the total production of insulating bricks.