Varieties Of Abrasives

Varieties of abrasivesThe varieties of abrasives can be divided into two categories: natural abrasives and artificial abrasives.First, the variety of natural abrasivesAll natural materials that can be used for grinding or grinding are collectively referred to as natural abrasives. Commonly used natural abrasives are the following:1. Diamond(1) for dressing grinding wheels;(2) grinding and grinding of difficult materials (such as cemented carbide, gem glass, stone, etc.).2. Natural corundum(1) high-grade corundum (commonly known as gemstone) sapphire (containing titanium), ruby (containing chromium), etc.;(2) ordinary corundum, black or brownish-red;Natural corundum, the first kind is mainly used for jewelry, two kinds can be used as abrasive, used to make grinding wheel, whetstone, sandpaper, emery cloth or micro-powder, grinding paste, etc.

Second, the variety of artificial abrasives1, corundum series artificial abrasivesCorundum series of artificial abrades are brown corundum, white corundum, zirconium corundum, microcrystalline corundum, single crystal corundum, chrome corundum, praseodymium corundum, black corundum and bauxite sintered corundum and so on.(1) Brown corundum (A)Brown corundum is made from bauxite, anthracite and iron filings, which are smelted at high temperature in electric arc furnace. In the smelting process, the carbon in the anthracite bauxite silicon oxide (SiO2), iron oxide and titanium oxide and other impurities reduced to metal, these metals together to become ferroalloy, due to its density is larger than corundum molten liquid and settling to the bottom of the furnace and corundum molten liquid separation.Brown corundum crushing resistance is strong, anti-oxidation, anti-corrosion, has good chemical stability, is a kind of widely used abrasive. It is suitable for grinding metal materials with high tensile strength, such as ordinary carbon steel, hard bronze, alloy steel, malleable cast iron, etc.(2) White fused alumina (WA)White corundum (a-Al2o3) is an abrasive made from aluminum oxide powder heated and melted in an arc furnace. Impurities in raw materials are not excluded in the smelting process, therefore, the quality of white corundum is closely related to the purity of raw materials.The content of A1203 in white corundum should be more than 97%, and its hardness is higher than that of brown corundum, but it is brittle. It has good cutting, oxidation resistance and gas corrosion performance, and has good insulation. Mainly used for hardening steel, alloy steel fine grinding and fine grinding, grinding thread and gear, white corundum can also be used for precision casting and refractory materials.(3) Microcrystalline corundum (MA)The raw materials and smelting method used by microcrystalline corundum are basically the same as that of brown corundum. Immediately after stopping the furnace, the molten liquid is poured into the mold for rapid cooling (generally within 30 minutes), so as to obtain the aggregate of fine crystals.Microcrystalline corundum in the smelting process, the degree of reduction of impurities is poor, the content of Al203 is 94% ~96%, the crystal size is generally 80~300 /tm, the crystal accounts for 57% ~85%, the largest crystal size does not exceed 400~600um. It has the characteristics of high strength and toughness. Suitable for heavy load grinding, can grind stainless steel, carbon steel, bearing steel and special ductile iron and other materials, because the abrasive particles in the grinding process is micro-edge broken state, is also used for precision grinding and even mirror grinding.(4) Single crystal corundum (SA)Single crystal corundum is bauxite, anthracite, iron filings and pyrite (FeS) as raw materials, in the arc furnace eutectic, bauxite in iron oxide, silicon dioxide and titanium oxide have been reduced and composed of iron alloy from the molten liquid settling to the bottom of the furnace. A small part of alumina and carbon, ferrous sulfide decomposition reaction, a small amount of aluminum sulfide (AI2S3) filled in between the single crystal particles, when the frit is cooled into the water, aluminum sulfide is dissolved, and the aluminum sulfide separated by the single crystal corundum can be dispersed into a natural particle size of the abrasive.Monocrystalline corundum is gray, its particle shape is mostly equal to the shape, the crystal does not contain impurities, with multi-angular cutting edge, under the same grinding force, the formed torque is less than other abrades, so it is not easy to break, high mechanical strength, single particle compressive strength is 22~38 kg, and brown corundum is only 10~20kg. Single crystal corundum due to high hardness and toughness, so the cutting ability is strong, can be used to process tool steel, alloy steel, stainless steel, high vanadium steel and so on.(5) Black fused alumina (BA)The smelting method of black corundum is the same as that of brown corundum, which is made of bauxite as raw material, with a small amount of reducing agent, and is melted, and its power consumption is about two-thirds of brown corundum. Is black, the main chemical composition: A1203 is not less than 77%, SiO2 content is 10% ~12%, Fe203 content is 7% ~ 10%, TiO2 about 3%, density is not less than 3.61 g/cm3.Black corundum has a good self-sharpening, less heat when grinding, the roughness of the workpiece is better, suitable for the underside polishing of parts before electroplating, the polishing of aluminum products and stainless steel, can also be used for polishing optical glass, processing wood and so on. Because of its good hydrophilicity, it can be used in the manufacture of sandpaper, emery cloth and resin abrasive tools, and can also be used as grinding paste and polishing powder. Because of its high iron content, black corundum is not suitable for the manufacture of ceramic abrades.

2, carbide series artificial abrasive silicon carbide (C, GC)Silicon carbide is quartz, petroleum coke as the main material, wood powder, salt as auxiliary materials according to a certain proportion of mixed into the resistance furnace, through high temperature smelting and made of artificial abrasive varieties.Silicon carbide is divided into black and green two kinds: black silicon carbide is black or blue-black, green silicon carbide is green or blue-green. In the manufacturing process, the production of green silicon carbide is characterized by the use of more pure raw materials, the burden to add salt, it can promote the product is green. The purity of green silicon carbide is higher than black silicon carbide.Silicon carbide does not react with any acid, but the melt of the basic oxide can promote the decomposition of silicon carbide.Compared with corundum artificial abrasives, black silicon carbide has higher hardness and greater brittleness. It is suitable for processing metals and non-metallic materials with lower tensile strength, such as gray cast iron, brass, lead and other non-ferrous metals, as well as hard brittle materials such as ceramics and glass stoneGreen silicon carbide compared with black silicon carbide, its purity, hardness, brittleness is slightly higher, suitable for processing hard and brittle materials, such as carbide, glass, agate, etc., is also widely used in measuring tools, cutting tools, mold grinding and aircraft, automobiles, ships and other engine cylinder honing.