Refractories are generally divided into two types, unshaped refractories and shaped refractories. Unshaped refractories usually refer to castables, which are mixed powder particles composed of a variety of aggregates or aggregates and one or more binders. When used, they must be mixed with one or more liquids to be evenly mixed. Strong liquidity. Shaped refractory materials generally refer to refractory bricks, the shape of which has standard rules, and it can also be temporarily processed as needed when building and cutting.
Refractory bricks are referred to as fire bricks. Refractory made of refractory clay or other refractory materials. Pale yellow or brown. It is mainly used for building smelting furnaces and can withstand high temperatures of 1,580℃-1,770℃. Also called firebrick. A refractory material with a certain shape and size. According to the preparation process, it can be divided into fired bricks, non-fired bricks, fused bricks (fused cast bricks), refractory and heat insulation bricks; according to the shape and size, it can be divided into standard bricks, ordinary bricks, special-shaped bricks, etc. It can be used as high-temperature building materials and structural materials for building kilns and various thermal equipment, and can withstand various physical and chemical changes and mechanical effects at high temperatures. For example, refractory clay bricks, high alumina bricks, silica bricks, magnesia bricks, etc.
Characteristic
- Chemical composition: the main components determine the quality and characteristics of the refractory material
- Bulk density: unit volume weight, high density, indicating good compactness, the strength may be high, but the thermal conductivity may be large. 3. Apparent porosity: no specific requirements, but as a manufacturer, the obvious pores must be strictly controlled.
- Load softening temperature: also called high temperature load starting deformation temperature, this parameter is very important, marking the material’s resistance to high temperature
- Thermal shock resistance: the ability to resist sudden changes in temperature without being destroyed
- Compressive strength: the maximum pressure ability to withstand (normal temperature)
- Flexural strength: the ability to withstand shear pressure
- Linear change rate: It is also called reburning line change or residual line change, which refers to the change in volume expansion and contraction in the same temperature change every time. If each expansion and contraction is the same, we define such a linear change rate as 0
Classification
According to the different components of refractory bricks, they can be divided into five categories, namely: silica-alumina refractory bricks, alkaline refractory bricks, carbon-containing refractory bricks, zirconium-containing refractory bricks, and heat-insulating refractory bricks. Any stove is not only built with one kind of refractory bricks, it needs a combination of different refractory bricks. The components of these five types of refractory bricks are introduced in detail below.Silica-aluminum refractory brick
1. Silica-alumina Refractory Brick Series
Silica-alumina refractory bricks, based on the phase diagram of the AL2O3-SiO2 binary system, mainly include the following.
(1) Silica brick refers to refractory bricks containing more than 29.3% SiO, and is the main variety of acid refractory bricks. It is mainly used for building coke ovens, and also used for the vaults and other load-bearing parts of thermal kilns for various glass, ceramics, carbon calciners, and refractory bricks. It is also used in the high-temperature load-bearing parts of hot blast stoves, but not Used in thermal equipment below 600°C and with large temperature fluctuations.
(2) Clay bricks. Clay bricks are mainly composed of mullite (25%-50%), glass phase (25%-60%), cristobalite and quartz (up to 30%). Usually hard clay is used as the raw material, the mature material is pre-calcined, and then mixed with soft clay, which is shaped by semi-dry or plastic method, and the temperature is 1300～1400 C to burn clay brick products. You can also add a small amount of water glass, cement and other binders to make unburned products and amorphous materials. It is a refractory brick commonly used in blast furnaces, hot blast stoves, heating furnaces, power boilers, lime kilns, rotary kilns, ceramics and refractory brick firing kilns.
(3) High alumina refractory bricks. The mineral composition of high alumina refractory bricks is corundum, mullite and glass phase. Its content depends on the ratio of AL2O3/SiO2 and the type and quantity of impurities. The refractory bricks can be classified according to the content of AL2O3. The raw materials are high alumina bauxite and sillimanite natural ores, as well as those mixed with fused corundum, sintered alumina, synthetic mullite, and clinker calcined with alumina and clay in different proportions. It is mostly produced by sintering method. But the products also include fused cast bricks, fused grain bricks, unburned bricks and unshaped refractory bricks. High alumina refractory bricks are widely used in the steel industry, non-ferrous metal industry and other industries.
(4) Corundum refractory bricks. Corundum bricks refer to a refractory brick with an AL2O3 content of not less than 90% and corundum as the main phase. It can be divided into sintered corundum bricks and fused corundum bricks.
2. Alkaline Series Refractory Bricks
Alkaline refractory bricks refer to refractory products with alkaline oxides such as Mg0 and CaO as the main components. The main varieties are as follows:
(1) Magnesia refractory bricks refer to refractory bricks with magnesite as the raw material, periclase as the main crystal phase, and MgO content above 80%-85%. Its products are divided into two categories: metallurgical magnesia and magnesia products. Depending on the chemical composition and use, there are Martin sand, ordinary metallurgical magnesia, ordinary magnesia brick, magnesia silica brick, magnesia alumina brick, magnesia calcium brick, magnesia carbon brick and other varieties. Magnesia refractory brick is the most important product among alkaline refractory bricks. It has high refractoriness and good resistance to alkaline slag and iron slag. It is an important high-grade refractory brick. Mainly used in open hearth, oxygen converter, electric furnace and non-ferrous metal smelting.
(2) Dolomite brick is an alkaline refractory brick produced with dolomite as the main raw material. It is widely used in alkaline converters, and can also be used as the inner lining of some refining ladle outside the furnace.
(3) Forsterite refractory brick is a kind of refractory brick with forsterite 2MgO·SiO2 as the main composition. It is mainly used for checker bricks in open hearth regenerators, bricks for ingots, furnace bottoms of heating furnaces, and also has a good use effect in copper smelting furnaces.
3. Carbon-containing Refractory Bricks
Carbon-containing refractory bricks are made of carbon or carbon compounds. Refractory brick products containing different forms of carbon as the main component are mainly divided into the following categories:
(1) Carbon brick is a high-temperature neutral refractory brick product made of carbonaceous materials as the main raw material and adding an appropriate amount of binder. Carbon bricks are widely used in masonry blast furnace bottom, hearth, hearth and lower part of the furnace body. It can increase the continuous operation time of the blast furnace and prolong the service life. In addition, carbon bricks are also widely used in the electrochemical industry, chemical industry, petrochemical industry, electroplating industry, ferroalloy industrial furnaces (or equipment linings), acid, lye tank linings and pipelines, and smelting of non-ferrous metals (such as Lead, aluminum, tin, etc.) furnace lining.
(2) Graphite refractory products are refractory materials made of natural graphite as raw material and clay as a binder. Such products include graphite clay crucibles, distillation tanks, plug bricks for cast steel, nozzle bricks and steel bucket lining bricks. Among them, graphite clay crucibles for steelmaking and smelting of non-ferrous metals are the most produced and widely used.
(3) Silicon carbide refractory products are advanced refractory materials produced with silicon carbide (SiC) as raw materials. It has good wear resistance and corrosion resistance, high temperature strength, high thermal conductivity, low linear expansion coefficient and good thermal shock resistance. In iron and steel smelting, it can be used for ladle lining, nozzle, plug, blast furnace bottom and hearth, tapping trough, converter and electric furnace tapping, heating furnace without water cooling slide rail, etc. In the smelting of non-ferrous metals (zinc, copper, aluminum, etc.), it is widely used in stills, distillation tower trays, side walls of electrolytic cells, molten metal pipelines, suction pumps, and melting metal crucibles. In the silicate industry, it is widely used as slats and muffle materials for various kilns, such as muffle furnace linings and saggers. In the chemical industry, it is mostly used in oil and gas generators, organic waste calciners, petroleum gasifiers and desulfurization furnaces. In addition, it can be used as rocket nozzles and high temperature gas turbine blades in space technology.
4. Zirconium-containing Refractory Bricks
Zirconium-containing Refractory Bricks. It belongs to an acidic material and is a product made from natural zircon sand (ZrSiO2). Zirconium refractory bricks are different from silicon-aluminum refractory bricks and carbon-containing refractory bricks. It has good slag resistance, low thermal expansion rate, thermal conductivity decreases with increasing temperature, high load softening temperature, and high wear resistance. With good thermal shock resistance, it has become an important material in various industrial fields. With the development of continuous casting and vacuum degassing technology in the metallurgical industry, zircon refractory bricks are more and more widely used, mainly in the following categories:
(1) Zircon bricks, in the steelmaking process, use the tapping degassing method, and zircon refractories have good corrosion resistance and thermal shock resistance to slag and molten steel, and are suitable for decompression It is widely used in the metallurgical industry to build degassing steel drum lining, and also used as stainless steel steel drum lining, continuous casting steel drum lining, casting bricks, plug bricks, sleeve bricks And high temperature induction furnace lining, etc. Zircon refractory bricks have high resistance to acid slag and glass, so they are also widely used in severely damaged parts of glass kilns for smelting the most active glass. Zircon refractories also have the property of not being penetrated by metal aluminum, aluminum oxide and its molten slag, so it has also obtained good effects on the furnace bottom of aluminum smelting.
(2) AZS fused bricks are also called fused zirconia corundum bricks. With the development of the glass industry, AZS fused bricks have become a necessary refractory material for the key parts of the glass furnace. It resists the corrosiveness of molten glass.
(3) AZS re-sintered fused bricks are mainly used to build the bottom and walls of glass kilns and thermal equipment such as heat storage checker bricks.
(4) Zirconium mullite fused bricks, which are characterized by dense crystal structure, high load softening temperature, good thermal shock resistance, high mechanical strength at room temperature and high temperature, good wear resistance, and good thermal conductivity. And it has excellent resistance to slag erosion. This kind of product has a wide range of uses, such as the discharge port of metallurgical heating furnace, soaking furnace, calcium carbide furnace, and the wall of glass melting furnace, etc., and the use effect is very good.
5. Insulation Refractory Bricks
Insulation refractory bricks. Refers to refractories with high porosity, low bulk density and low thermal conductivity. Thermal insulation refractories are also called lightweight refractories. It includes the following categories:
(1) High-aluminum heat-insulating lightweight refractory bricks. It is a heat-insulating lightweight refractory brick with bauxite as the main AL2O3 content of not less than 48%. The production process adopts the foam method or the burn-out addition method. High-aluminum heat-insulating lightweight refractory bricks can be used to build heat-insulating layers and parts that are not corroded and scoured by strong high-temperature molten materials. When in direct contact with the flame, the surface contact temperature of general high-aluminum heat-insulating refractory bricks shall not be higher than 1350℃. Mullite heat-insulating refractory bricks can directly contact the flame, and have the characteristics of high temperature resistance, high strength, and significant energy-saving effect. It is suitable for the lining of pyrolysis furnace, hot air furnace, ceramic roller kiln, electric porcelain drawer kiln and various resistance furnaces.
(2) Clay-based heat-insulating lightweight refractory bricks are heat-insulating refractory bricks with 30% to 48% AL2O3 content made of refractory clay as the main raw material. The production process adopts the burn-out adding character method and the foam method. Using refractory clay, floating beads, and refractory clay clinker as raw materials, adding binders and sawdust, batching, mixing, molding, drying, and firing to obtain a product with a bulk density of 0.3～1.5g/cm3 . The output of clay insulating bricks accounts for more than half of the total output of insulating refractory bricks.
(3) Diatomite heat-insulating lightweight refractory bricks are heat-insulating refractory products made of diatomite as the main raw material. It is mainly used in the thermal insulation layer below 900°C. The Chinese standard (GB 3996-1983) divides diatomite heat insulation products into GG-0.7a, GG-0.7b, GG-0.6, GG-0.5a, GG-0.5b and GG-0.4 according to their bulk density. Kind of grades.
(4) Floating bead bricks are heat-insulating refractory products made of floating beads as the main raw material. Floating beads are hollow aluminum silicate glass beads floated from fly ash from thermal power plants. It has light body, thin wall, hollow, smooth surface, high temperature resistance and good heat insulation performance. Utilizing these excellent characteristics of floating beads, a lightweight heat-insulating refractory material with excellent heat preservation performance can be manufactured. The production of floating bead bricks can be formed by a semi-dry method.