A fire brick is a molded rectangular block of clay that has been baked and treated to be heat resistant. Refractory applications such as fireplace and furnace lining are some of the uses for fire bricks. Refractory bricks are capable of sustaining intense heat without fusion. Fire brick usually contains aluminum oxide and silicon dioxide. The manufacturing process involves baking the bricks in high temperatures to create a vitrified ceramic product.
Heavy, dense fire brick products are made with fire clay, which contains a suitable content ratio of silica and alumina. These materials last for a very long time and are used in residential, commercial, and industrial furnace and firebox applications. Many industrial uses require specific properties, such as thermal conductivity or porosity, that must adhere to certain specifications. Fire brick properties can be adjusted by adding or adjusting the amount of refractory materials.
Ordinary dense clay fire bricks absorb and retain heat. Lightweight insulating fire bricks have low thermal conductivity and do not absorb heat well. These products are much softer and incorporate tiny air pockets that exhibit insulating properties. Insulating fire bricks maintain the refractory properties and can withstand very high temperatures; they are widely used in electric and gas fired kilns.
Refractory products are available in the form of bricks and in a wide variety of shapes and sizes. Precast types are manufactured for ferrous and nonferrous metal foundries. The steel, iron, and aluminum industries use refractory materials in the production of metal products. Castable products can be pumped and sprayed for various applications requiring thermal properties. Patching and repair products are made for boilers and furnaces to maintain the longest life possible.
Refractory and fire clay mortar are often used to join fire brick together. Ordinary Portland cement mortar is also used, but common mortar cannot withstand extreme temperatures; as a result, many building codes require the use of refractory mortar. Medium duty and high duty brick and mortar products are available for commercial and industrial applications. Patching and bonding mortars are also available in many forms including caulking tubes.
The many uses of fire brick products make them a versatile and indispensable product. The manufacturing of steel and aluminum require dense refractory products. Kilns are thermally insulated brick chambers used for firing and drying clay and ceramic products. Everything from pizza ovens to fireplaces make use of refractory fire bricks. Even the thermal shield on the space shuttle is a refractory fire brick product.