Refractoriness refers to the temperature at which the refractory castable cone sample can resist the effect of high temperature without softening and melting when there is no load. Refractory castables and high-temperature skills appeared together, roughly originating in the middle of the Bronze Age. During the Eastern Han Dynasty, clay refractory castables have been used as kiln materials and saggers for porcelain burning. At the beginning of the 20th Century, refractory castables developed towards high-purity, high-density and ultra-high temperature products. At the same time, monolithic refractory castables and refractory fibers appeared without firing and low energy consumption. Today, with the development of orchard energy skills, space skills, and new resource skills, refractory castables with comprehensive and high-quality functions such as high temperature resistance, erosion resistance, thermal vibration resistance, and erosion resistance have been used.
Composition and application of refractory castables: There are many varieties of refractory castables. Usually, they are divided into conventional refractory castables (1580～1770℃), advanced refractory castables (1770～2000℃) and top refractory castables (2000 ℃ above); According to chemical characteristics, it is divided into acidic refractory castables, neutral refractory castables and alkaline refractory castables. In addition, there are refractory castables for special events.
Acidic refractory castables use compound silicon as an important component, and silica bricks and clay bricks are commonly used. Silica brick is a siliceous product containing more than 93% of compound silicon. The raw materials used are silica, waste silica bricks, etc., with strong resistance to acid slag corrosion, high temperature softening under load, and no reduction in volume after repeated calcination, or even slight expansion; However, it is easily corroded by alkaline slag and has poor thermal shock resistance. Silica bricks are mainly used in thermal facilities such as coke ovens, glass melting furnaces, and acid steelmaking furnaces. Clay bricks use refractory clay as an important raw material and contain 30% to 46% of compound aluminum. They are weakly acidic refractory castables, have good thermal vibration resistance, and have corrosion resistance to acid slag, and are widely used.
Neutral refractory castables are mainly composed of aluminum, chromium or carbon. The corundum product containing more than 95% aluminum is a high-quality refractory castable with a wide range of functions. Chromium bricks with compound chromium as an important component have good corrosion resistance to steel slag, but have poor thermal vibration resistance and low temperature during high-temperature loading. Carbon refractory castables include carbon bricks, graphite products and silicon carbide products. They have very low thermal expansion parameters, high thermal conductivity, good heat resistance The slag is warm and light. It is deeply used as a high-temperature furnace lining material, and also as an autoclave lining for petroleum and chemical industries.
Alkaline refractory castables use compound magnesium and compound calcium as important components, and magnesia bricks are commonly used. Magnesium bricks containing more than 80% to 85% of combined magnesium have very, very good resistance to alkaline slag and iron slag, and have a higher refractoriness than clay bricks and silica bricks. It is mainly used for open hearth furnaces, oxygen blowing converters, electric furnaces, non-ferrous metal metallurgical facilities and some high-temperature facilities.
The refractory castables used in special occasions include high-temperature compound materials, such as compound aluminum, compound lanthanum, compound beryllium, compound calcium, compound zirconium, etc., and refractory oxide materials, such as carbides, nitrides, borides, silicides and sulfides High-temperature composite materials, including metal porcelain, high-temperature inorganic coatings and fiber-reinforced porcelain.