The definition of refractory materials varies from country to country:
according to the international standards published by ISO, refractory materials refer to inorganic non-metallic materials with a refractoriness of at least 1500 ℃;
In China, refractory materials are inorganic non-metallic materials with a refractoriness of not less than 1580 ℃. metallic material. At present, some specific materials, such as mold slag for steelmaking, have a refractoriness of only 1200 °C, but they are traditionally called refractory materials.
Refractory materials are used to make furnaces, kilns, waste incinerators, nuclear reactors, crucibles, molds. Today, the steel industry uses about 70% of the refractories produced.
Refractory
Refractory materials must remain chemically and physically stable at high temperatures. Depending on the operating environment, they must resist thermal shock, be chemically inert, or have a specific range of thermal conductivity and coefficient of thermal expansion and contraction.
Alumina, silica, and magnesia are the most important raw materials in the manufacture of refractory materials. Two other common raw materials are calcium (lime) oxides and refractory clay.
Some specific applications require special refractories. Zirconium dioxide is used to make materials that can withstand very high temperatures. In addition, silicon carbide and carbon (graphite) are used to make materials that can withstand very intense high temperatures, but they cannot be exposed to oxygen because they will burn through a redox reaction.
Binary compounds (eg tungsten carbide, boron nitride) can be very resistant to high temperatures. Hafnium carbide is the most temperature-resistant binary compound known, with a melting point of 3890 °C. The ternary compound of tantalum hafnium carbide has the highest known melting point (4215 °C).
Type of Refractory Materials
There are many types of refractory materials, and there are many classification methods.
According to the degree of refractoriness, it is divided into:
Ordinary refractories (1580～1770℃) (such as refractory clay)
Advanced refractories (1770～2000℃) (such as chromite)
Super grade refractory (above 2000℃) (such as zirconium dioxide)
According to chemical properties, it can be divided into:
Acid refractory
Neutral refractory
Alkaline refractory
There are also refractory materials for special occasions.
