Fire Bricks

Refractory brick is a ceramic material that is normally used in high temperature
environments because of its lack of flammability and because it is a decent insulator
which reduces the amount of energy loss. Refractory brick is typically comprised of
aluminium oxides and silica.

High Temperature Application:
The silica fire bricks that line steel-making furnaces are used at temperatures up to 3,000 °F (1,649 °C), which would melt many other types of ceramic, and in fact part of the silica firebrick liquefies. High-temperature Reusable Surface Insulation (HRSI), a material with the same composition, was used in the insulating tiles of the Space Shuttle.Non-ferrous metallurgical processes use basic refractory bricks because the slags used in these processes readily dissolve the “acidic” silica bricks. The most common basic refractory bricks used in smelting non-ferrous metal concentrates are “chrome-magnesite” or “magnesite-chrome” bricks (depending on the relative ratios of magnesite and chromite ores used in their manufacture).

Lower Temperature Application:
A range of other materials find use as firebricks for lower temperature applications, Magnesium oxide is often used as a lining for furnaces. Silica bricks are the most common type of bricks used for the inner lining of furnaces and incinerators. As the inner lining is usually of sacrificial nature, fire bricks of higher alumina content may be employed to lengthen the duration between re-linings. Very often cracks can be seen in this sacrificial inner lining shortly after being put into operation. They revealed more expansion joints should have been put in the first place, but these now become expansion joints themselves and are of no concern as long as structural integrity is not affected. Silicon carbide, with high abrasive strength, is a popular material for hearths of incinerators and cremators. Common red clay brick may be used for chimneys and wood-fired ovens.