Corundum Overview:
Corundum, the name originated in India, is a mineralogical name. There are three main variants of corundum Al2O3, namely α-Al2O3, β-Al2O3 and γ-Al2O3. In gemology, the conditions of gemstones are called Ruby (Ruby) and Sapphire (Sapphire). Myanmar, Sri Lanka, Thailand, Vietnam and Cambodia are the world's most important suppliers of high-quality ruby and sapphire. Other producing countries are China, Australia, the United States, Tanzania and so on. Corundum is second only to diamond in hardness.
Main uses of corundum:
Because of its excellent high-temperature properties and mechanical strength, corundum is widely used in many industrial fields such as metallurgy, machinery, chemical industry, electronics, aviation and national defense. Its main uses are described below.
1, due to high temperature resistance, corrosion resistance, high strength and other properties, it is used as a sliding gate for pouring steel, smelting rare metal, special alloy, high purity metal, glass wire drawing, making laser glass crucible and vessels; Various high temperature furnaces, such as refractory materials, ceramics, linings (walls and pipes) of ironmaking blast furnaces; Physical and chemical utensils, spark plugs, heat resistant and oxidation resistant coating. Low silicon sintered corundum brick with SiO2 less than 0.5% is the special lining of carbon black, boron chemical industry, fertilizer, synthetic ammonia reactor and vaporization furnace.
2, due to the characteristics of high hardness, good wear resistance, high strength, in the chemical system, used as a variety of reaction vessels and pipelines, chemical pump components; For mechanical parts, various molds, such as wire drawing die, extrusion pencil core die mouth, etc.; For cutting tools, abrasives, bulletproof materials, human joints, sealing grinding rings, etc.
3, due to high temperature insulation, it is used as a thermocouple wire tube and protective tube, atomic reactor with good insulation, coupled with little loss, dielectric constant is not large, in the electronics industry is widely used in solid integrated electric furnace base tube base, shell, porcelain frame, thin window, missile radar antenna protective cover.
4, Al2O3 is an ionic crystal, the structure is very stable. Used at high frequency, high pressure and high temperature, its insulation is still good, coupled with little loss, dielectric constant is not large, in the electronics industry is widely used in solid extrusion subgrade plate tube base, shell, porcelain frame, micro glass window, missile radar antenna protective cover and so on.
5, corundum products have good air tightness, even at high temperature is also tight and airtight, so it is widely used in electric vacuum, such as the use of corundum to make a variety of large vacuum tube shells, solid microcircuits in the dual in-line package shell.
6, corundum insulation materials, such as corundum light bricks, corundum hollow balls and fiber products, are widely used with a variety of high temperature furnace wall and furnace top, both high temperature and heat preservation.
7, transparent corundum products can be made of lamp, microwave fairing. In addition, Na-b-Al2O3 products are electrolyte materials for the manufacture of sodium-sulfur batteries.
Special purpose
As a kind of abrasive, corundum is widely used in abrasive abrasives, of which there are many types of corundum, the use of different types of corundum is not the same, this column will introduce you to the type characteristics and specific use of corundum.
1. Brown corundum
The appearance of brown corundum is brown, and the content is 94.5%- 97%. It has the characteristics of high hardness, high toughness, sharp particle and relatively low price, suitable for grinding metal with high tensile strength, in the absence of other abrasives, it can generally be replaced by it.
It is widely used for rough grinding of ordinary steel, such as: carbon steel, general alloy steel, calcined cast iron, hard bronze and so on. Brown corundum second grade abrasive commonly used as grinding wheel, resin cutting wheel. Sand tile, emery cloth, sandpaper, etc.
2. White corundum(white alumina oxide)
The hardness of white corundum is slightly higher than that of brown corundum, but the toughness is slightly worse when grinding, it is easy to cut into the workpiece, and the self-sharpness is better, the heat is small, the grinding ability is strong, the efficiency is high, and the price is higher than that of brown corundum.
Suitable for grinding high hardness steel, such as high speed steel, high carbon steel, hardened steel, alloy steel and so on.
3. Black corundum
Black corundum is a derivative of brown corundum and has a black appearance. Low hardness but good toughness.
It is mostly used for free grinding, such as polishing or rough grinding before electroplating, and is also used for making coated abrasive tools, resin cutting pieces, polishing blocks, etc.
4. Single crystal corundum
The particle of single crystal corundum abrasive is composed of a single crystal, and has a good multi-edge cutting edge, high hardness and toughness, strong grinding ability, less grinding heat, the disadvantage is that the production cost is high, there is waste gas in the production, waste water generation, and the output is low.
It can be used for grinding hard and tough hard metal materials, such as stainless steel, high vanadium high speed steel, heat resistant alloy steel and easily deformed and easily burned workpieces, considering that the single crystal corundum abrasive is limited by production conditions, generally only recommended for the grinding of heat resistant alloys and hard to grind metal materials.
5. Microcrystalline corundum
Microcrystalline corundum is a derivative of brown corundum, and its appearance color and chemical composition are similar to that of brown corundum. It is characterized by small crystal size (50-280 μm), good abrasive toughness, high strength and good self-sharpness.
Suitable for grinding stainless steel, carbon steel, ball mill cast iron, etc. The grinding method is suitable for forming grinding, cutting grinding, fine grinding and heavy load grinding.
6. Zirconium corundum
It is characterized by slightly lower hardness, but the toughness value is large, the strength is high, the crystal size is usually fine, and the wear resistance is good.
Foreign zirconium corundum abrasive is mainly used for heavy load grinding, suitable for grinding heat resistant alloy steel, titanium alloy and austenitic stainless steel.
7. Chrome corundum
Chrome corundum is a derivative of white corundum, the appearance is rosy, the hardness is similar to white corundum, the toughness is slightly higher than white corundum and the strength is high, the grinding performance is good, the grinding precision is high. Abrasives made of this kind of abrasive have good shape retention.
The application range is similar to that of white corundum, especially suitable for the fine grinding and molding of various tools, measuring tools, instrument parts, usually chrome corundum has better grinding performance than white corundum.
8. Sintered corundum
Sintered corundum is made of fine alumina or alumina powder sintered, characterized by good toughness, can be made into various special shapes and sizes of abrasive particles.
Mainly used for heavy duty ingot grinding wheel, suitable for grinding stainless steel ingot and so on.
