The main types of abrasive
Brown fused alumina
Brown corundum is a kind of brown artificial corundum made of bauxite by arc furnace smelting.Because of its high hardness (HV = 200 kg / 1800-2 was), good toughness and high melting point (800 ~ 000 ℃), therefore, can make grinding materials, brown fused alumina is the main chemical composition of Al, O, and its content is 95.00% ~ 97.00%.Is the most basic abrasive.It is widely used because of its good grinding performance, wide application range and low price.The appearance of brown corundum abrasive is brown sand grains, as fine as powder.Product identification is usually done by physical testing and chemical analysis.Brown corundum abrasive is suitable for processing carbon steel, alloy steel, malleable cast iron, hard bronze and other materials.
White fused alumina
White corundum is a kind of high purity corundum crystal which is made from aluminum oxide powder through high temperature melting and recrystallization in arc furnace.White color, hence the name of white corundum.The main ingredients are Al and O3, and the content is more than 98.5%.It has good chemical stability, slightly higher hardness than brown corundum (HV= 2 200-2 300 kg/mm'), and lower toughness than brown corundum.During grinding, the abrasive particles easily crumble.It is suitable for grinding hardened steel, high carbon steel, high - speed steel and thin - walled parts.Due to its fine blade structure, alundum is suitable for surface grinding.The appearance of white corundum abrasive is mainly white, and the coarse grain is bluish white.Product identification should be done by chemical analysis.The chemical composition of alundum and alundum is the same, but the density, crystalline form and petrographic composition are different.White corundum has a glassy appearance, is bright and reflective, and aluminum oxide does not have these features.The density of aluminum oxide powder was 3.55~3.80 g/cm3 and that of white corundum was 3.98 g/cm3.
Monocrystalline corundum is composed of monocrystals, which are made from bauxite, pyrite, anthracite and iron shavings.No single crystal can be observed by the naked eye in appearance, only by petrographic analysis.The content of Al.O of single crystal corundum is above 98%, its hardness (HV=2 300~2 400 kg/mm2) and toughness are higher than that of white corundum. The particles are spherical and most of them are isoaxial crystals.The appearance characteristic of monocrystalline corundum abrasive is that the sand surface is oily and has resin luster.This is because monocrystalline corundum has been pickling in the manufacturing process.Monocrystalline corundum has a light rose color, but sometimes it is similar to white corundum or light gray.The quality of single crystal corundum should be determined by chemical analysis and rock facies.Single crystal corundum can be used to process steel with high toughness and hardness, such as stainless steel and high vanadium and high speed steel.However, the single crystal corundum produces H,S gas and waste water in the manufacturing process, which seriously pollutes the environment.The yield of single crystal corundum is low, so the unit power consumption is about 50% higher than that of brown corundum, which is almost equal to that of white corundum.As a result, production is now largely halted at home and abroad.
The raw material and smelting process of micro-crystal corundum are similar to that of brown corundum, and its chemical composition is basically consistent with that of brown corundum. The main difference between the two is that the micro-crystal corundum will smelt the good corundum liquid in the electric furnace and adopts rapid cooling, so that the crystal size of corundum is small and the crystal size of 50~280um can be obtained.Because of the microcrystallization results, its strength is higher than that of brown corundum.The appearance of micronized corundum abrasive is the same as that of brown corundum.Chemical analysis is used for product identification.Its identification with brown corundum depends on its crystal size.Microcrystal corundum is suitable for grinding stainless steel, carbon steel, bearing steel, nodular cast iron and other materials, and can also be used for heavy duty grinding and precision grinding.
Chrome corundum is also made of aluminum oxide powder, in which 0.5%~2.0% chromium oxide is added to aluminum oxide powder.Chrome corundum in rose red, toughness than white corundum high, hardness similar to white corundum.Rose red is chrome corundum abrasive, the main appearance features.This red becomes lighter as the granularity becomes finer.Grinding tools made of chrome corundum are also rose red.The application range of chrome corundum in the grinding process is similar to that of white corundum, but the durability of the grinding tool and the roughness of the workpiece surface are slightly better than that of white corundum.
(bauxite) sintered corundum
High grade bauxite as raw material, not through the arc furnace smelting, but grinding bauxite to 3um into thin, die - cast broken body, high temperature into.Sintered corundum is characterized by good toughness, but not as hard as brown corundum.Often cylindrical, but can also be made into irregular sand.The main components of sintered corundum are A1,0, and the content is above 86%, followed by Fe(, and Si(, and the color is similar to that of microcrystalline corundum.Sintered corundum is a real microcrystalline artificial corundum.Its crystal size is around 5um.The appearance of sintered rigid E is the same as that of microcrystal corundum, but the acute Angle of its sand is not as sharp as that of microcrystal corundum.There are more equiareform grains in its particle size composition than any other kind of corundum.
Zirconium corundum is a compound oxide of alumina and oxide.It is made of aluminum-vanadium soil (or alumina powder), mianying sand, anthracite and iron shavings.It is a microcrystalline structure supported by the coarse grains of A1 and O3 in the base of ZrO, AlO and eutectic tissue.This kind of abrasive is gray-white, with great toughness, high strength and good abrasion resistance.In the rough grinding, rough grinding and heavy duty grinding of steel, the wrong corundum has the advantages of high grinding efficiency, good roughness, not easy to burn the workpiece, not difficult to block the surface of grinding wheel, and is suitable for heavy duty grinding, heat resistant alloy steel, cobalt alloy and austenite stainless steel.
Black corundum is also made by smelting bauxite in an electric arc furnace without fully reducing the impurities in bauxite.Typical black, the chemical composition of corundum is Al,0>77%, and also contains about 10% Fe203. This kind of abrasive is black, with certain toughness and lower hardness than brown corundum.Because black corundum is often used for polishing, so it is also known as polishing sand or polishing powder.
Black silicon carbide
Black silicon carbide is made from quartz sand, petroleum coke, wood chips and other materials in the resistance furnace.It is called black silicon carbide because of its blue color.Its chemical composition is mainly silicon carbide (98% of SiC>), containing a small amount of impurities (free carbon, free silicon, SiO2,Fe,O3).Impurity content <2%.High hardness (HV=3 100~3 300 kg/mm2), low toughness, mostly used in grinding or cutting non-iron materials with low tensile strength, such as nonferrous metals, wood, leather, plastics, stone, silicate materials (glass, ceramics, concrete, refractories, etc.) and cast iron.Because of its resistance to high temperature, chemical corrosion and thermal shock, it is widely used as a quality refractory.
Green silicon carbide
Green silicon carbide is made from quartz sand, petroleum coke, wood chips, salt and other raw materials in the resistance furnace.Because its color is green and get a name.The chemical composition is 99% of SiC> and the impurity is less than 1%.The hardness of green silicon carbide is very high (HV= 3,200 ~ 3,400 kg/mm2), and its high temperature hardness is slightly higher than that of black silicon carbide.Green silicon carbide is mainly used for processing non-ferrous materials with high hardness and brittleness, such as hard alloy and optical glass, etc., and is also used for making silicon carbon bar.
The appearance of boron carbide is black.Its hardness is higher than that of silicon carbide (HV= 5,000 kg/mm2).Because it is easily oxidized and decomposed at high temperature, it is not used to make grinding tools, but can be used separately, such as grinding or polishing high hard materials, such as artificial blue gem watch glass.