Refractory

Refractory

A refractory is a material that retains its strength at high temperatures. 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 environments above 1000 °F (538 °C)". [ASTM Volume 15.01 "Refractories; Activated Carbon, Advanced Ceramics"]

Refractory materials are used in linings for furnaces, kilns, incinerators and reactors. They are also used to make crucibles.

Refractory materials

Refractory materials must be chemically and physically stable at high temperatures. Depending on the operating environment, they need to be resistant to thermal shock, be chemically inert, and/or have specific values of thermal conductivity and of the coefficient of thermal expansion.

The oxides of aluminium (alumina), silicon (silica) and magnesium (magnesia) are the most important materials used in the manufacturing of refractories. Another oxide usually found in refractories is the oxide of calcium (lime). Fireclays are also widely used in the manufacture of refractories.

Refractories must be chosen according to the conditions they will face. Some applications require special refractory materials. Zirconia is used when the material must withstand extremely high temperatures. 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.

Types of refractories

Acidic refractories cannot be used in a basic environment and basic refractories cannot be used in an acidic environment because they will be corroded. Zircon, fireclay and silica are acidic, dolomite and magnesite are basic and alumina, chromite, silicon carbide, carbon and mullite are neutral. Refractory metals are also frequently used.

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

There are two common forms of refractories, bricks and monolithics. Bricks (also known as firebrick) 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. Castable refractory cement is also commonly used.

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.

ee also

*Furnace
*Masonry oven
*Refraction (metallurgy)

References

External links

* [http://www.refractoriesinstitute.org/ The Refractories Institute]


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  • Refractory — Re*frac to*ry ( r?), a. [L. refractorius, fr. refringere: cf. F. refractaire. See {Refract}.] 1. Obstinate in disobedience; contumacious; stubborn; unmanageable; as, a refractory child; a refractory beast. [1913 Webster] Raging appetites that are …   The Collaborative International Dictionary of English

  • Refractory — Re*frac to*ry, n. 1. A refractory person. Bp. Hall. [1913 Webster] 2. Refractoriness. [Obs.] Jer. TAylor. [1913 Webster] 3. OPottery) A piece of ware covered with a vaporable flux and placed in a kiln, to communicate a glaze to the other articles …   The Collaborative International Dictionary of English

  • refractory — [ri frak′tər ē] adj. [altered < obs. refractary < L refractarius < refractus: see REFRACT] 1. hard to manage; stubborn; obstinate: said of a person or animal 2. resistant to heat; hard to melt or work: said of ores or metals 3. a) not… …   English World dictionary

  • Refractory — Refractory. См. Огнеупор. (Источник: «Металлы и сплавы. Справочник.» Под редакцией Ю.П. Солнцева; НПО Профессионал , НПО Мир и семья ; Санкт Петербург, 2003 г.) …   Словарь металлургических терминов

  • refractory — index contumacious, difficult, disobedient, disorderly, fractious, froward, hostile, incorrigible, ind …   Law dictionary

  • refractory — stubborn, obstinate, perverse, 1610s (earlier refractorious, 1550s), from L. refractarius obstinate …   Etymology dictionary

  • refractory — recalcitrant, intractable, ungovernable, *unruly, headstrong, willful Analogous words: *contrary, perverse, froward, wayward: *insubordinate, rebellious, contumacious Antonyms: malleable: amenable (sense 2) …   New Dictionary of Synonyms

  • refractory — ► ADJECTIVE 1) formal stubborn or unmanageable. 2) Medicine not yielding to treatment. 3) technical heat resistant; hard to melt or fuse. DERIVATIVES refractoriness noun. ORIGIN Latin refractarius stubborn …   English terms dictionary

  • refractory — refractorily, adv. refractoriness, n. /ri frak teuh ree/, adj., n., pl. refractories. adj. 1. hard or impossible to manage; stubbornly disobedient: a refractory child. 2. resisting ordinary methods of treatment. 3. difficult to fuse, reduce, or… …   Universalium

  • Refractory — Not yielding (at least not yielding readily) to treatment. * * * 1. Resistant to treatment, as of a disease. SYN: intractable (1), obstinate (2). 2. SYN: obstinate (1). [L. refractarius, fr. refringo, pp. fractus, to break in pieces] * * *… …   Medical dictionary

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