Classification of refractory bricks

Oct 24, 2023

According to the different compositions of refractory bricks, they can be divided into five categories, namely: silicon-alumina series refractory bricks, alkaline series refractory bricks, carbon-containing refractory bricks, zirconium-containing refractory bricks, and insulating refractory bricks. Any stove is not built with only one kind of refractory bricks, but requires the use of different refractory bricks in conjunction with each other. The following is a detailed introduction to the components of these five categories of refractory bricks.

1. Silicon-aluminum refractory bricks, it is reported, are based on the AL2O3-SiO2 binary system phase diagram as the basic theory, and mainly include the following types.

(1) Silica brick refers to refractory bricks containing more than 93% SiO2, which is the main variety of acid refractory bricks. It is mainly used for building coke ovens, and is also used in the vaults and other load-bearing parts of thermal kilns of various glass, ceramic, carbon calciners, and refractory bricks. It is also used in high-temperature load-bearing parts of hot blast furnaces, but it is not suitable for use in Used in thermal equipment with temperatures below 600°C and large temperature fluctuations.

(2) Clay bricks. Clay bricks are mainly composed of mullite (25% to 50%), glass phase (25% to 60%), cristobalite and quartz (up to 30%). Usually hard clay is used as the raw material, and the clinker is pre-calcinated, and then mixed with soft clay, formed by a semi-dry method or a plastic method, and fired at a temperature of 1300 to 1400 C to produce clay brick products. You can also add a small amount of water glass, cement and other binding agents to make unfired products and amorphous materials. It is a commonly used refractory brick in blast furnaces, hot blast furnaces, 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 phases. Their content depends on the AL2O3/SiO2 ratio and the type and quantity of impurities. Refractory bricks can be graded according to the AL2O3 content. The raw materials are high-alumina bauxite and sillimanite natural ores, which are also 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 granular bricks, unfired 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 that use magnesia as raw material, periclase as the main crystal phase, and an MgO content of more than 80% to 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 bricks, magnesia silica bricks, magnesia aluminum bricks, magnesia calcium bricks, magnesia carbon bricks and other varieties. Magnesia refractory bricks are the most important products among alkaline refractory bricks. They have high refractory resistance and good resistance to alkaline slag and iron slag. They are an important high-grade refractory brick. Mainly used in open hearth furnaces, oxygen converters, electric furnaces 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 lining of some refining packages outside the furnace.

(3) Forsterite refractory brick is a refractory brick mainly composed of forsterite 2MgO·SiO2. It is mainly used for open-hearth furnace checker bricks, ingot casting bricks, heating furnace bottoms, and also has good results in copper-smelting furnaces.

3. Carbon-containing refractory bricks.

Carbon-containing refractory bricks refer to refractory brick products made of carbon or carbon compounds, with different forms of carbon as the main component. They are mainly divided into the following categories.

(1) Carbon bricks are high-temperature resistant neutral refractory brick products made of carbonaceous materials as the main raw material and an appropriate amount of binder added. Carbon bricks are widely used in the construction of blast furnace bottoms, hearths, bosses and lower parts of the furnace shafts. It can improve the continuous operation time of the blast furnace and extend its service life. In addition, carbon bricks are also widely used in electrochemical industry, chemical industry, petrochemical industry, electroplating industry, ferroalloy industrial furnaces (or linings of equipment), acid and alkali tank linings and pipelines, and smelting non-ferrous metals (such as Lead, aluminum, tin, etc.) furnace lining.

(2) Graphite refractory products are refractory materials made from natural graphite as raw material and clay as binder. Such products include graphite clay crucibles, distillation tanks, plug bricks for cast steel, nozzle bricks and steel drum lining bricks. Among them, graphite clay crucibles for steelmaking and non-ferrous metals are the most produced and widely used.

(3) Silicon carbide refractory products are advanced refractory materials produced from silicon carbide (SiC). It has good wear resistance and corrosion resistance, high high temperature strength, high thermal conductivity, small linear expansion coefficient and good thermal shock resistance. In terms of steel smelting, it can be used in ladle linings, nozzles, plugs, blast furnace bottoms and bosses, tap troughs, converter and electric furnace tap openings, water-cooled slide rails in heating furnaces, etc. In the smelting of non-ferrous metals (zinc, copper, aluminum, etc.), it is widely used in distillers, distillation tower trays, electrolytic cell side walls, molten metal pipelines, suction pumps, and smelting metal crucibles. In the silicate industry, it is widely used as shed plates and flameproof 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, in space technology, it can be used as rocket nozzles and high-temperature gas turbine blades.

4. Zirconium-containing refractory bricks.

It is an acidic material and is a product made from natural zircon sand (ZrSiO2). Zirconium refractory bricks are different from silicon-alumina series refractory bricks and carbon-containing series refractory bricks. They have good slag resistance, small thermal expansion rate, thermal conductivity decreases with the increase of temperature, high load softening temperature and high wear resistance. It has good thermal shock resistance and 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 increasingly used in the following categories.

(1) Zircon bricks, in the steelmaking process, use the tapping degassing method, and zircon refractory materials 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 for masonry degassing steel drum linings, stainless steel drum linings, continuous casting steel drum linings, sprue bricks, plug bricks, and sleeve bricks. As well as high-temperature induction furnace linings, etc. Zircon refractory bricks are highly resistant to acidic slag and glass and are therefore also widely used in severely damaged areas of glass kilns where the most reactive glasses are smelted. Zircon refractory material also has the property of not being penetrated by metal aluminum, aluminum oxides and slag, so it also achieves good results on the furnace floor of aluminum smelting.

(2) AZS fused bricks, also known as fused zirconium corundum bricks. With the development of the glass industry, AZS fused bricks have become a necessary refractory material for key parts of glass furnaces. It is highly resistant to the erosion of liquid glass.

(3) AZS resintered fused bricks are mainly used for building the bottom and walls of glass tank kilns and thermal equipment such as heat storage checker bricks.

(4) Zirconium mullite fused bricks, which are characterized by dense crystal structure, high softening temperature under load, good thermal shock resistance, high mechanical strength at normal and high temperatures, 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. It is used in the discharge port of metallurgical heating furnaces, soaking furnaces, calcium carbide furnaces, glass melting furnace walls, etc., with good results.

5. Insulating refractory bricks.

It refers to refractory materials with high porosity, low volume density and low thermal conductivity. Insulating refractory materials are also called lightweight refractory materials. It includes the following categories.

(1) High-aluminum insulating lightweight refractory bricks. It is an insulating lightweight refractory brick with bauxite as the main content and an AL2O3 content of not less than 48%. The production process adopts foam method, and can also use burnout additive method. High-aluminum insulating lightweight refractory bricks can be used to build thermal insulation layers and areas that are not subject to strong erosion and erosion by high-temperature molten materials. When in direct contact with flames, the surface contact temperature of general high-aluminum insulating refractory bricks shall not be higher than 1350°C. Mullite insulating refractory bricks can be directly exposed to flames and have the characteristics of high temperature resistance, high strength and significant energy saving effect. Suitable for lining of pyrolysis furnaces, hot blast furnaces, ceramic roller kilns, electric porcelain drawer kilns and various resistance furnaces.

(2) Clay insulating lightweight refractory bricks are insulating refractory bricks with an AL2O3 content of 30% to 48% made of refractory clay as the main raw material. Its production process adopts burnout additive method and foam method. Using refractory clay, floating beads and refractory clay clinker as raw materials, adding binder and sawdust, through batching, mixing, shaping, drying and firing, a product with a bulk density of 0. 3 to 1. 5 g/cm3 is produced. . The output of clay insulation bricks accounts for more than half of the total output of insulating refractory bricks.

Chinese standards (GB 3994-1983) classify clay insulation bricks into NG-1.5, NG-1.3a, NG-1.3b, NG-1.0, NG-0.9, NG-0.8, NG-0.7, NG according to volume density. -0.6, NG-0.5, NG-0.4 10 grades.

(3) Diatomite insulating lightweight refractory bricks are insulating refractory products made of diatomite as the main raw material. It is mainly used in heat insulation layers below 900°C.

Chinese standards (GB 3996-1983) divide diatomite insulation products into GG-0.7a, GG-0.7b, GG-0.6, GG-0.5a, GG-0.5b and GG-0.46 according to volume density. Kind of brand.

(4) Floating beads bricks are heat-insulating and refractory products made of floating beads as the main raw material. Floating beads are hollow aluminum silicate glass beads floated from fly ash in thermal power plants. It is light, thin-walled, hollow, smooth in surface, resistant to high temperatures and has good thermal insulation properties. Using these excellent properties of floating beads, lightweight heat-insulating refractory materials with excellent thermal insulation properties can be produced. Semi-dry molding can be used to produce floating bead bricks.

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