Refractory

When refractory materials are referred to in the art in general ceramic products and materials with an operating temperature of about 600 ° C. According to the definition (DIN 51 060), however, only materials with a pyrometric cone equivalent larger SK 17, which corresponds to about 1500 ° C to designate as fireproof. This temperature limit has no technical relevance, but is duty-free and legally relevant mining.

The major components of inorganic non-metallic materials (ceramics and glass, glass ceramics, glass fibers and mineral fibers ), the oxides of silica, alumina, magnesium oxide, calcium oxide, zirconium oxide and chromium oxide. In addition, carbon (C) and silicon carbide (SiC ), are important components. You also have to count on their high melting points and their chemical resistance to many slags and melts to the refractory materials the so-called refractory metals (molybdenum, tungsten ) and the platinum group metals (precious metals ) and their alloys.

Specifically, the following definition would be: Refraktärwerkstoffe are metallic and ceramic materials for application temperatures (from 300 ° C) above 600 ° C (there is no generally accepted definition! ) To about 1700 ° C, which are in direct thermal contact with a high temperature process (eg: melting metals or glass; firing ceramics ) and its subsequent and secondary thermal processes ( forming, heat treatment, ..) are available.

Main purpose of the refractory materials are so furnace linings in the iron and steel, glass, aluminum, cement and ceramic industry and shaping tools in these industries. Here in the selection of suitable materials for a process not only the temperature plays an important role but also the atmosphere, the minimum temporal stability or operational capability, chemical resistance, mechanical strength, the achievable inter alia m.

Production

The production of the high-temperature- resistant materials will depend on the class of materials ( ceramics, metal, composite material ), but is also determined by the material properties required for the intended purpose of use significantly. It actually come all production processes for the production of refractory materials are used that are specific to the particular group of materials. In ceramics, these are, inter alia, pressing, casting, stamping, enamel cast iron and metals, for example, alloying, rolling, or melting.

Economic data

Worldwide in 1997 about 17.8 million tonnes, and production of refractory materials, while it only slightly in 2001 were still more than twelve million tons. In Germany, the production fell from refractory materials of about 1.6 million tonnes in 1980 to just under one million tons in 2004.

Although the need for refractory metals and PGM is increasing worldwide, but this increase is not due to applications in the refractory sector due but due to other application areas. Currently (2005) t of molybdenum per year produced about 140,000 worldwide, about 40,000 tons of tungsten and about 120 tonnes of platinum ( from primary production ) and about 100 tonnes of other PGM.

The price for a ton of refractory material or the main raw material ( in 2005 ) that are listed in its order of magnitude for some materials. In the platinum group metals, the price is determined by the daily stock exchange, where the other materials primarily by the demand for individual commodities, but which are used en masse in other industries:

Use behavior

The "problem " of all Refraktärwerkstoffe is that they are, despite their relative insensitivity to the environment and the high temperature, a more or less severe wear. The food and service life of refractory products is between a few days and many years. This is dependent on the temperature in the application, the chemical resistance to the surrounding media with the high temperatures of the material properties or by the operation of the aggregates.

"Refractory " products in daily life

Many products of daily life are not fireproof but tolerates warmth, heat resistant, resistant to thermal shock or fire-retardant, but are referred to as " refractory" in common parlance and in advertising. A well-known example is " refractory " glass (formerly called Pyrex, a borosilicate glass, and now mostly glass-ceramics ).

The lining of stoves ( fireclay), the viewing window (usually a glass-ceramic ) of the furnaces, the materials of tile stoves are examples of refractory materials in daily use.

Industrial use

In addition to traditional refractory bricks and mixes a range of thermal insulation products such as fire bricks and high temperature wool have been developed in recent decades.