Refractory is an adjective that comes from the Latin word refractarius . The dictionary of the Royal Spanish Academy (RAE) mentions different meanings of the term: the first refers to the individual who rejects the fulfillment of an obligation or a duty.
Someone refractory, therefore, shows rebellion to comply with a command or to accept a different thought than his. For example: "The player was refractory to the instructions of his coach and was replaced before the end of the first half" , "The mayor is refractory to journalistic inquiries: that is why he prefers not to dialogue with the press" , "The young man Refractory, he insulted the policemen before being arrested ” .
The refractory materials, moreover, are those which have a good resistance to the fire, it is to support its action without being altered. These are materials that tolerate high temperatures without going into decomposition or modifying their properties.
Although there is no precise definition that indicates when a material can be classified as refractory, it is generally considered that it is if it is able to tolerate temperatures above 1100ºC without undergoing deformation.
The lime, the silica, the alumina and magnesium oxide are some of the refractories. This means that these materials have a low thermal conductivity, resist thermal shocks and do not expand at high temperatures.
Due to their characteristics, refractory materials are used to line incinerators and furnaces and for the manufacture of crucibles.
Firebrick
Refractory brick is known as a class of ceramic material that has a number of very particular characteristics that make it especially versatile for use in industry. It has smooth faces, a feature that makes it less adherent to mortar, and this makes it more resistant to abrasion and high temperatures. Mortar, on the other hand, is a compound used to glue stones, concrete blocks, bricks and other construction elements.Firebrick is quite expensive, but it compensates the economic investment with its thermal properties. Today, it is used for lining boilers, rotary kilns, grills and acceleration pots, for example, and to adhere them to each other refractory earth is used; It is worth mentioning that cement can make the joint more firm, and therefore can be added to the mixture, which has a similar appearance to clay.
Handling a firebrick is more complicated than a regular one, as it can generate an explosion if not combined with the right materials. As with refractory earth, this type of brick is a very good heat container, that is, it has the ability to conserve the temperature to which it is exposed throughout the different processes it goes through.
The percentage of alumina concentration that is used in the manufacture of a firebrick (which can be as low as 36% and as high as 99%) directly influences its resistance to high temperatures. Another material that can be used is silica, and this decision in conjunction with the percentage of alumina results in the quality of the final product. If you do not want to subject it to widely varying temperatures, it does not need to contain much alumina.
For the lining of furnaces that are used to melt steel, a refractory silicon dioxide brick is used, which usually begins to liquefy when the temperature exceeds 1650 ° C. Its manufacture requires exposing the components to low pressures and burning them at extremely high temperatures.