Abrasive materials, General information
Abrasives (fr. abrasif - grinding, from Latin abradere - to scrape) are substances of high hardness that are used for processing various surfaces. They are used in shaping or finishing of a workpiece by friction, which results in the removal of the surface layer of material from the processed area. The result can be either a smoothed, polished surface or a surface with the desired roughness.
Source: https://www.geolib.net/mineralogy/kvarc.html
Abrasives are divided by hardness (superhard, hard, soft) and chemical composition, as well as by the size of the grinding grit (coarse, medium, fine, extra fine). Grit size is measured according to the standards of various international measurement systems: FEPA, JIS, etc. In the Russian GOST, micrometers are used. The particle size of standard abrasives ranges from 2 mm (2000 microns) to 40 microns. The mechanics of their work in the process of grinding is determined by the shape and hardness. The abrasive grains have rough edges, often ending in dots, which reduce the contact area of the surface, due to which pressure is localized at that point. When the abrasive and the material come into contact, the force applied to the grains causes fragments of the material to break away, simultaneously flattening the abrasive grain and/or causing the grain to separate from the rest of the abrasive. The more firmly the grit is anchored in the abrasive layer, the less wear it is subjected to and the longer its working life.
Source: https://clck.ru/qBNJT
As a rule, the materials used as abrasives are either hard minerals (of Mohs scale 6 or higher) or synthetic stones, some of which may be chemically and physically identical to natural ones. The most prominent example is diamond, which is extracted by mining and, at the same time, is grown artificially in a laboratory. Both versions of the abrasive have the same working qualities.
NATURAL ABRASIVES
Diamond — is a cubic allotropic form of elementary carbon, mined in primary (kimberlite pipes) and placer deposits (see article). It is the most expensive natural abrasive and because of its cost it is practically not used for abrasive works.
Source: http://dragmag.ru/chem-opredeljaetsja-cennost-neobrabotannyh-almazov/
Emery - is a natural mineral composed of corundum and magnetite (a black magnetic iron oxide) It has been used by people as the basic and most available abrasive material for several thousand years (see article).
Source: https://alexander-td.com/ru/blog/nazhdak
Corundum — is a crystalline aluminum oxide, one of the hardest minerals, second only to diamond. It is mined in placers and sometimes in ores. It is practically not used as an abrasive, as it is replaced by its synthetic, cheaper analogue.
Source: https://kamenis.com/korund/korund-kamen/
Diatomite — is a mineral composed of the shells of ancient mollusks and crustaceans (diatoms) by more than 50% of its weight. It is used in polishing pastes (see article).
Source: https://clck.ru/qBJBM
Garnet — is a group of minerals found in crystalline shales and gneisses. It is contained in natural abrasives in the form of impurities, and the main substance of the rock acts as a natural binder, firmly holding its grains (see article).
Source: https://clck.ru/qBKC5
Quartz — is a crystalline silicon dioxide, one of the most common minerals in the Earth's crust. It is the basic mineral for the highest quality and most expensive natural abrasives (see article).
Source: https://mineralpro.ru/minerals/quartz/
FREQUENTLY USED SYNTHETIC ABRASIVES
Artificial diamond — is a cubic allotropic form of elementary carbon which is synthesized under high pressure. It is used everywhere for processing of hard alloys, stone, glass, non-ferrous metals, etc. One of the most popular abrasives (see article).
Source: https://russian.alibaba.com/Popular/CN_rough-diamonds-from-india-Trade.html
Cubic boron nitride (borazon, elbor, CBN). Synthesized at high pressure by heating boron and nitrogen in the presence of various catalyst solvents. Along with artificial diamond it belongs to the most productive and expensive synthetic abrasives.
Boron-carbon-silicon alloy is a superhard material with microhardness (hardness of separate parts of microstructure) exceeding 70 GPa. It is created in the process of melting of coke, quartz and boron anhydride in an electric arc furnace, followed by crushing and classification by grain size.
Source: http://phyjnc.com/en/product/7_1
Boron carbide — is a binary compound of boron and carbon. It is the third hardest abrasive after diamond and elbor.
Source: https://snabcomplekt.com/helpful-information/primenenie-karbid-bora/
Silicon carbide — is a binary inorganic chemical compound of silicon and carbon. One of the most popular abrasive materials, it is widely used for processing various steels. (see article)
Source: https://stankiexpert.ru/spravochnik/materialovedenie/karbid-kremniya.html
Electrocorundum — is an artificial aluminum oxide, the second most popular abrasive substance after silicon carbide. It is used for processing various hard surfaces, both in the form of bonded abrasives and in the form of various soft pastes. (see article)
Source: https://liv-unikon.com.ua/ru/glynozem-metallurgycheskyj.html
Synthetic abrasives also include other substances used in industry: aluminum nitride, silicon nitride, zirconium oxide, cerium dioxide, tin dioxide, chromium oxide, titanium dioxide, etc.
ABRASIVE BINDING MATERIALS
For ease of use in industry, the abrasive grain is placed in a special matrix - a binder that firmly holds the abrasive, most often by baking at high temperatures (see article). Thanks to the binder, the abrasive materials can be given any shape required for use in a variety of production conditions. Binding allows the abrasive to be given additional properties and to be more varied for the required application. Various coatings over which the abrasive grit is applied can also perform the function of a binder. The abrasive can also be used in a free form, for various options of blasting, tumbling with free rolling objects, etc. Abrasives are used in the form of a variety of tools: trimming and grinding wheels, bars of different sizes, tapes, sandpaper, special polishing pastes, etc..
Source: https://aif.by/vybor/kakie_abrazivnye_krugi_i_diski_vybrat_dlya_raboty
The main types of surface treatment are: cylindrical and flat grinding, belt grinding, lapping, water-jet and sandblasting, ultrasonic treatment, honing (hole treatment), polishing and supergrinding (used for high-precision mechanisms, devices, etc.).
Abrasives play an exceptional role in the modern industrial processing of tough and hard materials, being involved in the creation of most human-made products. However, only a small part of them can be used in the effective, fast and quality processing of hardened steel and be used in operations related to its grinding, including sharpening.
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