The term refractory refers to the quality of a material to retain its strength at high temperatures. Temperature is a physical property of a system that underlies the common notions of hot and cold something that is hotter generally has the greater temperature ASTM C71 defines refractories as "non metallic materials having those chemical and physical properties that made them applicable for structures, or as components of systems, that are exposed to enviroments above 1000 °F (538 °C)"¹.

Refractory materials are used in linings for furnaces, kilns, incinerators and reactors. A furnace is a device used for Heating The name derives from Latin fornax, Oven. Kilns are thermally insulated chambers or Ovens in which controlled temperature regimes are produced Incineration is a waste treatment technology that involves the Combustion of organic materials and/or substances They are also used to make crucibles. A crucible is a cup-shaped piece of laboratory object Laboratory equipment used to contain Chemical compounds when heating them to very high Temperatures

Refractory materials

Refractory materials must be chemically and physically stable at high temperatures. Depending of the operating environment they need to be resistant to thermal shock, be chemically inert, and/or have specific values of thermal conductivity and coefficient of thermal expansion. Thermal shock is the name given to cracking as a result of rapid temperature change In English to be inert is to be in a state of doing little or nothing In Physics, thermal conductivity, k is the property of a material that indicates its ability to conduct Heat. Thermal Expansion is the tendency of matter to change in Volume in response to a change in temperature

The oxides of aluminium (alumina), silicon (silica) and magnesium (magnesia) are the most important materials used in the manufacturing of refractories. An oxide is a Chemical compound containing at least one Oxygen atom as well as at least one other element WikipediaNaming Silicon (ˈsɪlɪkən or /ˈsɪlɪkɒn/ silicium is the Chemical element that has the symbol Si and Atomic number 14 The Chemical compound silicon dioxide, also known as silica or silox (from the Latin " Silex " is an Oxide Magnesium (mægˈniːziəm is a Chemical element with the symbol Mg, Atomic number 12 Atomic weight 24 Magnesium oxide, or magnesia, is a white solid Mineral that occurs naturally as Periclase and is a source Another oxide usually found in refractories is the oxide of calcium (lime). Calcium (ˈkælsiəm is the Chemical element with the symbol Ca and Atomic number 20 Lime is a general term for various naturally occurring Minerals and materials derived from them in which Carbonates Oxides and Hydroxides of Fireclays are also widely used in the manufacture of refractories.

Refractories must be chosen according to the conditions they will face. Some applications required some special refractory materials. Zirconia is used when the material must withstand extremely high temperatures. Zirconia redirects here For the Sailor Moon character see Dead Moon Circus. Silicon carbide and carbon are two other refractory materials used in some very severe temperature conditions, but they cannot be used in contact with oxygen, as they will oxidize and burn. Silicon carbide ( is a compound of Silicon and Carbon bonded together to form Ceramics but it also occurs in nature as the extremely rare mineral Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6

Types of refractories

Acidic refractories cannot be used in a basic environment and basic refractories cannot be used in acidic environment because they will be corroded. In Computer science, ACID ( Atomicity Consistency Isolation Durability) is a set of properties that guarantee that Database transactions are In Chemistry, a base is most commonly thought of as an aqueous substance that can accept Protons This refers to the Brønsted-Lowry theory of acids and Zircon, fireclay and silica are acidic, dolomite and magnesite are basic and alumina, chromite, silicon carbide, carbon and mullite are neutral. Dolomite (ˈdɒləmaɪt is the name of a Sedimentary Carbonate rock and a Mineral, both composed Chromite is iron magnesium chromium oxide (Fe MgCr2O4 It is an Oxide Mineral belonging to the Spinel group Mullite, or porcelainite, is a rare Clay Mineral with the chemical composition Al 6 Si 2 O 13 Refractory metals are also frequently used. Refractory metals are a class of Metals that are extraordinarily resistant to Heat and Wear.

Refractory materials are used extensively in the metals industries, along with glass melting and other heat treatment operations.

There are two common forms of refractories, bricks or monolithics. Bricks are pre-sintered forms which can hold their shape. Monolithics are loose material which can be formed into complex shapes, or sprayed into place, and have to be sintered before use. Sintering is a method for making objects from powder, by heating the material (below its Melting point - solid state sintering until its particles adhere

Refractory Anchorage

Anti-abrasion refractory attached to pipes, chambers, etc, will require anchorage systems such as wire formed anchors or hexmetal to support the refractory linings.

Refractory heat-up

Usually, refractories require special heat-up techniques to insure that their performance will be attained as designed, and to avoid thermal shock and drying stresses until the operational status is achieved. After building of a new refractory-lined industrial furnace or equipment or refractory maintenance or relining of existing equipment a necessary step is the start-up of the operation which usually

References

¹ ASTM Volume 15. 01 Refractories; Activated Carbon, Advanced Ceramics

See also

• Furnace

External links

• The Refractories Institute
• Causeway Steel Products - Reafractory Anchorage Systems