What are the main characteristics of materiaux refractaire?

Posted by sophiamilller on August 27th, 2013

Refractory products are special products that can withstand the action of high temperatures. These products are used mainly to achieve metallurgical melting furnaces (for obtaining iron and other specific products). Materiaux refractaire are materials which, regardless of their composition, are very resistant at temperatures higher than 1450 degrees Celsius. Some refractaire materials are composed of a single chemical element, such as the following metals: tungsten, platinum, chrome; non-metals such as carbon under the form of graphite; others under the form of refractory alloys such as refractory steels with high content of chromium and tungsten.

The more diverse and used materiaux refractaire are those made of oxide, oxide compounds and mixtures of oxidizing compounds, such as silicon dioxide, aluminium trioxide, magnesium oxide, calcium oxide, chromium oxide, zirconium dioxide, all in crystalline, stabilized structures. A newer category or refractory materials is based on inorganic compounds such as nitrides, carbides, etc.

As a presentation form, some refractaire materials are shaped in the form of blocks, bricks, pipes, rods, or various complex shapes, while others are in the form of bulk materials and / or granular materials which mixed with water or other liquids are applied in several layers or forms, then poured and paved, and then hardened at normal temperature or after a suitable heat treatment.

From the definition of refractory materials, the notion of super refractory materials is derived. They are the refractory materials that are used at temperatures higher than 1600-1700°C, that have great mechanical strength, higher density and melting temperatures higher than 1900-2000°C. Semi refractory materials are materials that can be used only at temperatures from 800 to 1000 degrees Celsius.

Depending on the refractory materials used, the following materials can be obtained: aluminous silicate, chromate, silica, aluminous materials. For example, for the last type, people used as refractory materials rocks or minerals containing aluminium and bauxite (sedimentary rock), kaolin (mineral) for which they used fireclay as a binder material (which is different from simple clay, used mainly in the usual pottery industry).

Refractory materials cannot be used in operation at temperatures equal to their refractoriness. The operating temperature is usually tens or hundreds degrees lower that the refractoriness of the product, depending on the nature, properties and conditions of use of those refractory products.  Thus, under the influence of the tasks faced, meaning the mechanical and chemical actions as well as the temperature, the refractory materials begin to soften and lose their strength at temperatures much lower than their refractoriness.

Refractory materials must withstand the thermal, mechanical and chemical processes that occur during various thermal processes within aggregates and still keep their basic properties, with no important changes. In general, in practice, there is one predominant action of factors of destruction. The action of slag sometimes determines the softening of the refractory material and the loss of its resistance; sometimes contraction due to changes of network decreases its thermal stability (a thermal shock).

There are specialized producers who deal with these materiaux refractaire. All the characteristics of refractaire products can be seen on their websites and those who are interested in buying them can find out all they need to know.