(6) Zirconium corundum (ZA)
Zirconium corundum is made of aluminum oxide powder and zirconia as raw material, smelted in electric arc furnace at high temperature, and the whole process is basically a melting recrystallization process. It is a kind of eutectic aggregate composed of α--Al2O3, and ZrO2, and the two crystals should be interlaced to form microcrystalline crystals as much as possible during the smelting process.
Zirconium corundum is suitable for high speed and heavy load grinding, and can be used for grinding cast iron, cast steel, alloy steel and high speed steel, etc. It is especially suitable for titanium alloy, heat resistant alloy, high vanadium steel and stainless steel grinding process.
(7) Praseodymium corundum (NA)
The manufacturing process of praseodymium-neodymium corundum is similar to that of white corundum, with the difference that about 0.175% praseodymium-neodymium enrichment (praseodymium oxide, neodymium oxide, lanthanum oxide) is added in the smelting process. It is suitable for grinding stainless steel, high-speed steel, ductile iron, high manganese cast steel and certain heat-resistant alloys.
(8) Black corundum (BA)
Black corundum smelting method is the same as brown corundum, with trihydrate bauxite as raw material, add a small amount of reducing agent, made by dissolving, its power consumption is about two-thirds of brown corundum. It is black in color, main chemical composition: Al2O3 is not less than 77%, SiO2 content is 10--12%, Fe2O3 content is 7--10%, TiO2 is about 3%, specific gravity is not less than 3.61.
Black corundum has good self-sharpening, less heat generation when grinding, better finish of processed parts, suitable for polishing the bottom surface of parts before electroplating, polishing aluminum products and stainless steel, also can be used for polishing optical glass, processing wood, etc.. Because of its good hydrophilicity, it can be used in the manufacture of sandpaper, emery cloth and resin abrasives, and can also be used as abrasive paste and polishing powder. Black corundum due to high iron content, and therefore should not be used for the manufacture of ceramic abrasives.
(9) Alumina sintered corundum
Bauxite sintered corundum is the only corundum smelted without electric furnace, it uses high quality cooked bauxite (Al2O3 content of 85% or more) by wet ball milling to 3 micron particles slurry (ball milling should be added binder), and then pressed and filtered into a variety of geometric shapes, sintered at 1500 ℃.
The main chemical composition of alumina sintered corundum: Al2O3 (85--88%), SiO2 (3--4%), TiO2 (3.5--4.5%), Fe2O3 (5.6--6.5%). It has α--Al2O3 microcrystalline structure, high toughness, can withstand large grinding pressure without breaking, and can cut thicker metal layers, and the lateral feed can be up to 6 mm or more. The shape of the abrasive can be made into various columnar bodies, which is the only special case among all abrasives and is suitable for heavy-duty barren grinding.
2、Carbide series artificial abrasives
(1) Silicon carbide
Silicon carbide is made of quartz, petroleum coke as the main material, water powder, salt as auxiliary materials mixed in a certain proportion and then loaded into the resistance furnace, through high-temperature smelting and made of artificial abrasive.
Silicon carbide is divided into two types of black and green: black silicon carbide (C) is black or blue-black, and green silicon carbide (GC) is green or blue-green. In the manufacturing process, the production of green silicon carbide is characterized by the use of purer raw materials and the addition of table salt to the furnace charge, which promotes a green color of the product. The purity of green silicon carbide is higher than that of black silicon carbide.
Silicon carbide does not react with any acid, but alkaline oxide melts can contribute to the decomposition of silicon carbide.
Compared with corundum-based artificial abrasives, black silicon carbide is harder and more brittle, and is suitable for processing low tensile strength metal and non-metal materials, such as gray cast iron, brass, lead and other non-ferrous metals, as well as ceramics, glass factory materials and other hard and brittle materials. Green silicon carbide compared with black silicon carbide, its purity, hardness, brittleness is slightly greater, suitable for processing hard and brittle materials, such as cemented carbide, glass, agate, etc., but also widely used in measuring tools, cutting tools, mold fine grinding and aircraft, automotive, marine and other engine cylinder honing.
With industrial development and scientific and technological progress, silicon carbide non-grinding applications are expanding, in the inflammation-resistant materials used to make a variety of advanced inflammation-resistant products, such as pads, out of the iron groove, crucible melting pool; in the metallurgical industry as a steel deoxidizer, can save electricity, shorten the smelting time, improve the operating environment; in the electrical industry, the use of silicon carbide conductive, thermal conductivity and oxidation resistance to create heating elements --Silicon carbide rods. Silicon carbide sintered products can be used as fixed resistors, and in engineering can also be used as anti-slip and anti-corrosion agents. Silicon carbide mixed with epoxy resin can be coated in acid-resistant containers, worm gear blades to play a role in corrosion and wear resistance.
(2) Cerium silicon carbide (CC)
Cerium carbide is smelted in the silicon carbide furnace charge without adding salt and adding trace amount of cerium oxide (CeO2), its appearance is similar to green silicon carbide, microhardness is 36.29 Gpa. compared with green silicon carbide, its cerium carbide microhardness, single particle compressive strength, toughness, etc. are higher than green silicon carbide.
Since the physical properties of cerium silicon carbide have been changed, the grinding effect has been improved to some extent. The test proves that when grinding titanium alloy, cerium silicon carbide compared with green silicon carbide, cutting efficiency is nearly doubled, and the spark is smaller; when grinding cast iron, when the tool feed is 0.01mm, cerium silicon carbide durability than green silicon carbide grinding wheel increased by 18.9%, grinding ratio increased by 9.6%, when the tool feed is 0.02mm, its durability increased by 27.4%, grinding ratio increased by 74.1%. This shows that the effect of grinding cast iron with cerium silicon carbide improves more significantly than that of green silicon carbide when the tool feed is 0.02mm. The effect of grinding cemented carbide is similar to that of green silicon carbide, and the effect of grinding hard-to-grind high-speed steel such as CO5Si M5Al 5F-6 is similar to that of single crystal corundum.
(3) Boron carbide (BC)
Boron carbide (B4C) is made of boric acid (H3BO3) and carbon materials as raw materials, smelted in an electric arc furnace at a high temperature of 1700 - 2300 ℃ by the direct reduction of carbon to molten boric anhydride (B2O3).
Boron carbide a metallic luster gray-black powder, a super hard material. When heated to 500℃ in air, boron carbide begins to oxidize when the temperature reaches 800--900℃, its oxidation effect is more significant. Boron carbide has been used to replace diamond to grind carbide tools. Its sintered products can replace diamond as a grinding wheel dressing tool, suitable for fine grinding tungsten carbide, carbon titanium alloy, sintered corundum, artificial stones and special ceramics and other hard material products.
(4) Silicon boron
Silicon-boron is made of boric acid, quartz sand and graphite, smelted at high temperature in an electric arc furnace, and is gray-black in color, its hardness is second to boron nitride and higher than boron carbide, with high brittleness.
It is suitable for hard material processing such as hard alloy, semi-tutor, artificial gemstone and special ceramics.
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