Fire brick
Encyclopedia
A fire brick, firebrick, or refractory brick is a block of refractory
ceramic
material used in lining furnace
s, kiln
s, fireboxes, and fireplace
s. A refractory brick
is built primarily to withstand high temperature, but will also usually have a low thermal conductivity
for greater energy efficiency. Usually dense firebricks are used in applications with extreme mechanical, chemical, or thermal stresses, such as the inside of a wood-fired kiln or a furnace, which is subject to abrasion from wood
, fluxing from ash or slag, and high temperatures. In other, less harsh situations, such as a natural gas
fired kiln
, more porous bricks are a better choice. They are weaker, but they are much lighter, easier to form, and insulate far better than dense bricks. In any case, firebricks should not spall
under rapid temperature change, and their strength should hold up well during rapid temperature changes.
, and for special purposes may also be glazed. There are two standard size of fire-brick; one is 9 × 4½ × 3 in. (230 mm × 115 mm × 75 mm) and the other is 9" × 4½" × 2½". Also available are firebrick "splits" which are half the thickness and are often used to line wood stoves and fireplace inserts. The dimensions of a split are usually 9" × 4½" × 1¼". In the United States
, fire bricks were made at the now-defunct Evens & Howard Fire Brick Company
in Saint Louis, Missouri, and shipped to diverse locations around the nation as well as Canada. Here is a description of the plant circa 1904:
or alumina and 50% silicon dioxide
or silica. They can also be made of chamotte
and other materials. For bricks of extreme refractory character, the aluminium oxide content can be as high as 50-80% (with correspondingly less silica), and silicon carbide
may also be present.
firebricks that line steel
-making furnace
s are used at temperatures up to 1650°C (3000°F), which would melt many other types of ceramic, and in fact part of the silica firebrick liquefies. HRSI, a material with the same composition, is used to make the insulating tiles of the space shuttle
.
applications. Magnesium oxide
is often used as a lining for furnace
s. Common red clay brick are used for chimneys and wood-fired ovens.
Refraction (metallurgy)
In metallurgy, refraction is a property of metals that indicates their ability to withstand heat. Metals with a high degree of refraction are referred to as refractory. These metals derive their high melting points from their strong intermolecular forces...
ceramic
Ceramic
A ceramic is an inorganic, nonmetallic solid prepared by the action of heat and subsequent cooling. Ceramic materials may have a crystalline or partly crystalline structure, or may be amorphous...
material used in lining furnace
Furnace
A furnace is a device used for heating. The name derives from Latin fornax, oven.In American English and Canadian English, the term furnace on its own is generally used to describe household heating systems based on a central furnace , and sometimes as a synonym for kiln, a device used in the...
s, kiln
Kiln
A kiln is a thermally insulated chamber, or oven, in which a controlled temperature regime is produced. Uses include the hardening, burning or drying of materials...
s, fireboxes, and fireplace
Fireplace
A fireplace is an architectural structure to contain a fire for heating and, especially historically, for cooking. A fire is contained in a firebox or firepit; a chimney or other flue allows gas and particulate exhaust to escape...
s. A refractory brick
Brick
A brick is a block of ceramic material used in masonry construction, usually laid using various kinds of mortar. It has been regarded as one of the longest lasting and strongest building materials used throughout history.-History:...
is built primarily to withstand high temperature, but will also usually have a low thermal conductivity
Thermal conductivity
In physics, thermal conductivity, k, is the property of a material's ability to conduct heat. It appears primarily in Fourier's Law for heat conduction....
for greater energy efficiency. Usually dense firebricks are used in applications with extreme mechanical, chemical, or thermal stresses, such as the inside of a wood-fired kiln or a furnace, which is subject to abrasion from wood
Wood
Wood is a hard, fibrous tissue found in many trees. It has been used for hundreds of thousands of years for both fuel and as a construction material. It is an organic material, a natural composite of cellulose fibers embedded in a matrix of lignin which resists compression...
, fluxing from ash or slag, and high temperatures. In other, less harsh situations, such as a natural gas
Natural gas
Natural gas is a naturally occurring gas mixture consisting primarily of methane, typically with 0–20% higher hydrocarbons . It is found associated with other hydrocarbon fuel, in coal beds, as methane clathrates, and is an important fuel source and a major feedstock for fertilizers.Most natural...
fired kiln
Kiln
A kiln is a thermally insulated chamber, or oven, in which a controlled temperature regime is produced. Uses include the hardening, burning or drying of materials...
, more porous bricks are a better choice. They are weaker, but they are much lighter, easier to form, and insulate far better than dense bricks. In any case, firebricks should not spall
Spall
Spall are flakes of a material that are broken off a larger solid body and can be produced by a variety of mechanisms, including as a result of projectile impact, corrosion, weathering, cavitation, or excessive rolling pressure...
under rapid temperature change, and their strength should hold up well during rapid temperature changes.
Manufacture
In the making of firebrick, fireclay is baked in the kiln until it is partly vitrifiedGlass transition
The liquid-glass transition is the reversible transition in amorphous materials from a hard and relatively brittle state into a molten or rubber-like state. An amorphous solid that exhibits a glass transition is called a glass...
, and for special purposes may also be glazed. There are two standard size of fire-brick; one is 9 × 4½ × 3 in. (230 mm × 115 mm × 75 mm) and the other is 9" × 4½" × 2½". Also available are firebrick "splits" which are half the thickness and are often used to line wood stoves and fireplace inserts. The dimensions of a split are usually 9" × 4½" × 1¼". In the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, fire bricks were made at the now-defunct Evens & Howard Fire Brick Company
Evens & Howard Fire Brick Co.
The Evens & Howard Fire Brick Company was a manufacturer of fire bricks in St. Louis, Missouri, USA. It was founded formally in 1855 as the Cheltenham Fireclay Works and achieved sales as far away as Quebec and Africa. One source dates the beginning of the company back to 1837 but under different...
in Saint Louis, Missouri, and shipped to diverse locations around the nation as well as Canada. Here is a description of the plant circa 1904:
Composition
Fire bricks usually contain 30-40% aluminium oxideAluminium oxide
Aluminium oxide is an amphoteric oxide with the chemical formula 23. It is commonly referred to as alumina, or corundum in its crystalline form, as well as many other names, reflecting its widespread occurrence in nature and industry...
or alumina and 50% silicon dioxide
Silicon dioxide
The chemical compound silicon dioxide, also known as silica , is an oxide of silicon with the chemical formula '. It has been known for its hardness since antiquity...
or silica. They can also be made of chamotte
Grog (clay)
Grog, also known as firesand and chamotte, is a ceramic raw material. It has high percentage of silica and alumina. It can be produced by firing selected fire clays to high temperature before grinding and screening to specific particle sizes. It can also be produced from pitchers...
and other materials. For bricks of extreme refractory character, the aluminium oxide content can be as high as 50-80% (with correspondingly less silica), and silicon carbide
Silicon carbide
Silicon carbide , also known as carborundum, is a compound of silicon and carbon with chemical formula SiC. It occurs in nature as the extremely rare mineral moissanite. Silicon carbide powder has been mass-produced since 1893 for use as an abrasive...
may also be present.
High temperature applications
The silicaSilicon dioxide
The chemical compound silicon dioxide, also known as silica , is an oxide of silicon with the chemical formula '. It has been known for its hardness since antiquity...
firebricks that line steel
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...
-making furnace
Furnace
A furnace is a device used for heating. The name derives from Latin fornax, oven.In American English and Canadian English, the term furnace on its own is generally used to describe household heating systems based on a central furnace , and sometimes as a synonym for kiln, a device used in the...
s are used at temperatures up to 1650°C (3000°F), which would melt many other types of ceramic, and in fact part of the silica firebrick liquefies. HRSI, a material with the same composition, is used to make the insulating tiles of the space shuttle
Space Shuttle
The Space Shuttle was a manned orbital rocket and spacecraft system operated by NASA on 135 missions from 1981 to 2011. The system combined rocket launch, orbital spacecraft, and re-entry spaceplane with modular add-ons...
.
Lower temperature applications
A range of other materials find use as firebricks for lower temperatureTemperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
applications. Magnesium oxide
Magnesium oxide
Magnesium oxide , or magnesia, is a white hygroscopic solid mineral that occurs naturally as periclase and is a source of magnesium . It has an empirical formula of and consists of a lattice of Mg2+ ions and O2– ions held together by ionic bonds...
is often used as a lining for furnace
Furnace
A furnace is a device used for heating. The name derives from Latin fornax, oven.In American English and Canadian English, the term furnace on its own is generally used to describe household heating systems based on a central furnace , and sometimes as a synonym for kiln, a device used in the...
s. Common red clay brick are used for chimneys and wood-fired ovens.