Why can refractory brick fire resistant
1. A raw material analysis
Refractory brick production and manufacturing raw materials are generally natural ore, such as bauxite, silica, magnesite and other raw materials after processing and manufacturing of different properties of refractory brick, such as alumina-silicon refractory brick, silica refractory brick and magnesia refractory brick three kinds.
The main component of alumina is alumina, which is hydrated alumina containing impurities. It is a kind of earthy mineral, insoluble in water, soluble in sulfuric acid, sodium hydroxide solution. Mainly used for smelting aluminum, and the production of refractory materials, because of high bauxite clinker refractories up to 1780℃, strong chemical stability, good physical properties. Ultra high temperature refractory zirconium fused alumina brick can be produced by purifying bauxite at high temperature to produce a kind of corundum main crystal phase with alumina content more than 90%.
The raw material of silica refractory brick is silica and the main component is SiO2. The higher the content, the higher the refractoriness. The most harmful impurities are AL2O3, K2O, Na2o and so on. The production of silica brick is made of natural silica as raw material, plus an appropriate amount of mineralizing agent, to promote the quartz in the body to transform into scale quartz. Slow firing at 1350~1430℃ in reducing atmosphere. It has high temperature strength. The softening temperature under load is 1620℃.
Magnesite is the main raw material for making magnesia refractory brick. Its basic composition is MgO, and magnesium oxide has high fire resistance and insulation performance. The high temperature burning above 1000℃ can be converted to crystal, rising to 1500-2000 ℃ into sintered magnesia, and then broken to a certain size or powder can be made into magnesia brick or magnesia ramming material, magnesia refractory brick is alkaline refractory brick, alkali slag has strong resistance, but can not resist the erosion of acid slag, refractoriness above 2000℃, However, its softening point under load is only 1500℃, and its thermal shock stability is poor.
2. belong to inorganic nonmetallic materials
Inorganic non-metallic materials and organic high polymer material and the metal material and listed as the three major common inorganic metal materials of features are: high crushing strength, high hardness, high temperature resistant, fight corrode, moreover in corrosion resistant ceramic, refractory materials on the thermal insulation performance has its outstanding characteristics of these are for metal materials and polymer materials can not be compared. But compared with metal materials, it has low fracture strength and lack of ductility. Compared with polymer materials, the density is higher and the manufacturing process is complicated.
3. forming and sintering
Refractory brick production process is through mineral crushing – raw material mixing – mechanism forming – high temperature firing process finally produces a high temperature resistant products, which the body in the high temperature tunnel kiln sintering temperature will be higher than the softening temperature of its products under the load sintering temperature in general above 1500℃. Fireproof above 1770℃. High temperature resistance is good. Refractory brick is mainly used for furnaces lining steel – making electric furnace, glass furnace, cement converter and so on.
Refractory bricks can resist high temperature for three reasons mainly rely on ①the high refractoriness of raw materials minerals used in refractory bricks. ② As inorganic non-metallic material, the level of raw material determines the level of its use. ③ The finished body is subjected to high temperature above 1500℃ in the high-temperature tunnel kiln, so the refractory brick can resist high temperature and is suitable for the lining of high-temperature kiln.