An abrasive is a material, often a mineral, used to form or complete workpieces through friction that leads to pieces of workpiece lost due to friction. While finishing materials often mean polishing it to get a smooth and reflective surface, this process can also involve hardening such as satin, matte or finished beads. In short, the ceramics used to cut, grind and polish other soft materials are known as abrasives.
The abrasion materials are very common and are used very widely in a variety of industrial, domestic, and technological applications. This gives rise to great variations in abrasive physical and chemical compositions as well as abrasive forms. Some common uses for abrasives include grinding, polishing, buffing, honing, cutting, drilling, sharpening, banging, and sanding (see abrasive machining). (For simplicity, the "minerals" in this article will be used loosely to refer to both minerals and substances that resemble either manmade minerals or not.)
File is not abrasive; they remove the material not by scratching or rubbing, but by cutting the sharp teeth that have been cut to the surface of the file, very similar to the saw. However, diamond files are an abrasive coated shape (because they are metal rods lined with diamond powder).
Video Abrasive
Mechanics of abrasion
The abrasive generally depends on the difference in hardness between the abrasive material and the material being worked out, the abrasive becomes harder than the two substances. However, this is not necessary because two solid materials repeatedly rub against each other will tend to fade together; examples include, softer shoe soles that sweep away wood or stone steps for decades or centuries or glaciers degrading the rocky valleys.
Typically, the materials used as abrasives are hard minerals (rated 7 or more on the Mohs hardness scale) or synthetic stones, some of which may be chemically and physically identical to natural minerals but can not be called minerals as they do. does not appear naturally. (Although useful for comparative purposes, the Mohs scale is of limited value to material engineers because it is an arbitrary, ordinal, irregular scale.) Diamond, a common abrasive, for example occurs naturally and is produced industrially, such as corundum naturally but which is now more commonly made from bauxite. However, softer minerals such as calcium carbonate are used as abrasive materials, such as "polishing materials" in toothpaste.
This mineral is destroyed or is small enough (anywhere from a macroscopic grain of about 2 mm to a microscopic grain of about 0.001 mm) to allow its use as abrasive. These grains, commonly called grits, have rough edges, often ending at points that will decrease the surface area in contact and increase local contact pressure. Rough materials and materials to be carried are brought into contact while in motion relative to each other. Styles applied through the granules cause fragments of the material employed to escape, while simultaneously refining coarse grains and/or causing the grain to work away from other abrasive parts.
Some factors that will affect how quickly a substance is obscured include:
- The violent difference between two substances: a much tougher abrasive will cut faster and deeper
- Grain size (grit size): larger grains will be cut faster because cut deeper
- Adhesion between grains, between grains and backing, between grains and matrix: determines how quickly the seeds disappear from the abrasive and how quickly the fresh grains, if any, are exposed
- Contact style: more styles will cause faster abrasion
- Loading: abrasive wear and removal of work material tends to fill space between abrasive grains thereby reducing cutting efficiency while increasing friction
- Use of lubricants/coolers/metalworking: Can transport swarf (prevent loading), transport heat (which may affect the physical properties of a workpiece or abrasive), reduce friction (with substrate or matrix), suspend subject to work material and allow abrasives to finish more finely, do stress on the workpiece.
Maps Abrasive
Mineral abrasive
Abrasives can be classified as natural or synthetic. When discussing sharpening stones, natural stones have long been considered superior but advances in material technology see these differences becoming less distinct. Many synthetic abrasives are effectively identical to natural minerals, differing only because synthetic minerals have been produced rather than mined. Dirt in a natural mineral can make it less effective.
Some natural abrasives are:
- Calcite (calcium carbonate)
- Emery (impure corundum)
- Dust diamonds (synthetic diamonds are widely used)
- Novaculite
- Pumice
- Rouge
- Sand
- Corundum
- Garnet
- Sandstone
- Tripoli
- Feldspar Powder
- Staurolite
Some abrasive minerals (such as alumina zirconia) occur naturally but are quite rare or quite harder or expensive to obtain such a way that synthetic stones are used in industry. These and other artificial abrasives include:
- Borazon (cubic boron nitride or CBN)
- Ceramics
- Aluminum oxide ceramics
- Iron oxide iron
- Corundum (alumina or aluminum oxide)
- Dry ice
- Glass beams
- Abrasif steel
- Silicon carbide (carborundum)
- alumina Zirconia
- Boron carbide
- Slag
Abrasive produced
Abrasives are formed for many purposes. Natural abrasives are often sold as a dressing stone, usually in the form of rectangular blocks. Both natural and synthetic abrasives are generally available in various forms, often coming as bonded or coated abrasives, including blocks, belts, discs, wheels, sheets, rods and loose grains.
Abrasive bound
A bonded abrasive consists of an abrasive material contained in the matrix, although very fine aluminum abrasive oxides may comprise sintered material. This matrix is ​​called a binder and is often a clay, resin, glass or rubber. This abrasive and binder mixture is usually formed into blocks, sticks, or wheels. The most commonly used abrasive is aluminum oxide. Also common are silicon carbide, tungsten carbide and garnet. An artificial stone is often a bonded and readily available abrasive as a two-sided block, each side representing different grit levels.
Grinding wheels are cylinders that are rotated at high speed. Despite having worked with a foot pedal or a hand crank, the introduction of an electric motor has made it necessary to build the wheel to withstand a larger radial pressure to prevent flying wheels apart as it spins. A similar problem arises with the cutting of the wheel, which is often strengthened structurally with impregnated fibers. The relatively high speeds between abrasives and workpieces often make it necessary to use such lubricants. Traditionally, they are called refrigerants because they are used to prevent the formation of friction heat that can damage the workpiece (such as damage the tempering of the blades). Some studies show that lubricant heat transport properties are less important when dealing with metals because metals will rapidly heat from the work surface. More important is their effect on reducing tensile stress while increasing some pressure press and reducing "thermal and mechanical pressure during chip formation".
Various shapes are also used as heads in rotary equipment used in precision work, such as scale modeling.
The tied Abrasive needs to be straightened and applied after use. Dressing is cleaning of waste material (swarf and loose abrasive) from the surface and showing fresh grit. Depending on the abrasives and how they are used, dressings may involve abrasives that are only placed under running water and brushed with a rigid brush for soft rocks or other abrasive abrasive soils, such as aluminum oxide used to dress grinding wheels.
Truing is returning the abrasive to its original surface shape. Wheels and stones tend to be uneven, leaving the cutting surface no longer flat (it says "dished out" if it is meant to be flat stone) or no longer the same diameter across the cutting surface. This will cause uneven abrasion and other difficulties.
Abrasive plated
A coated layer consists of abrasives mounted on a support material such as paper, cloth, rubber, resin, polyester or even metal, many of which are flexible. Sandpaper is a very common abrasive layer. Coated abrasives are the most common minerals similar to those used for bound abrasives. A binder (often a kind of adhesive or resin) is applied to the support to provide a flat surface which is then followed by the grit. Backing webbing can also use a filler agent (again, often resin) to provide additional resistance.
The coated abrasive can be formed for use in rotary and orbital abrasives, to wrap around the sanding block, as handpads, as closed loops for use on belt grinders, as a striking surface on matchboxes, on diamond and diamond plates. Diamond tools, though for cutting, are often abrasive.
Another abrasive and its use
Sand, glass beads, metal slags of copper slag and dry ice can all be used for a process called sandblasting (or similar, such as the use of bead blasting glass beads). Dry ice will be sublimated without leaving the rest of the abrasive.
The cutting compounds used in automotive paints are examples of suspended abrasives in liquids, pastes or waxes, such as some polishing fluids for silver and optical media. The liquid, paste or wax act as a binding agent that maintains the abrasion attached to the fabric used as a base to move the abrasive throughout the workpiece. Especially cars, wax can serve as a protective agent by preventing exposure of paint from metal to air and also acts as an optical filler to make less visible scratches. Toothpaste contains calcium carbonate or silica as a "polishing agent" to remove plaque and other ingredients from the tooth because of the hardness of calcium carbonate less than tooth enamel but more than that of a contaminant.
Highly refined rouge powder is commonly used for grinding glass, which is somewhat replaced by modern ceramics, and is still used in jewelry making for highly reflective end result.
The cleaning product also contains suspended abrasives in pastes or creams. They are chosen to be quite safe on some surfaces of linoleum, tiles, metal or stone. However, many laminated surfaces and ceramic furnaces on it are easily damaged by these abrasive compounds. Even ceramic or pottery or cookware utensils can damage this surface, especially the bottom of the tableware, which is often not partially or completely glazed and acts as another bonded abrasive.
The metal pots and stoves are often rubbed with abrasive cleaners, usually in the form of the above mentioned creams or pastes or of steel wool and non woven scouring pads that hold abrasive fine grains.
Human skin also undergoes abrasion in the form of exfoliation. Abrasives for this can be much softer and more exotic than for other purposes and may include things like almonds and oatmeal. Dermabrasion and microdermabrasion are a rather general cosmetic procedure that uses abrasive minerals.
Scraped compact discs and DVDs can sometimes be fixed through buffing with very fine compounds, the principle is that many small scratches will be more optically transparent than single big scratches. However, this does require skill and will eventually cause the protective layer of the disc to be completely eroded (especially if the original stroke is deep), at that time, the surface of the data will be destroyed if the abrasion continues.
abrasive options
The shape, size and nature of the workpiece and the desired end result will affect the abrasive options used. A bonded abrasive grinding wheel can be used to hone a knife commercially (resulting in a hollow mill), but an individual can then sharpen the same knife as a natural or even abrasive-coated abrasive (like sandpaper) embedded on a soft, non- slip to make reaching the convex grinding easier. Similarly, a brass mirror can be cut with a bonded abrasive, the surface is flattened with a coated abrasive to obtain a base shape, and then has a finer value of abrasives successively applied to a wax paste impregnated with rouge to leave a sort of "finish without taste "called, in this case," the mirror is finished ".
Also, different adhesive shapes can make it more difficult to scrape a certain area of ​​the workpiece. Health hazards may arise from generated dust (which can be repaired through the use of lubricants) which may cause silicosis (when abrasive materials or workpieces are silicates) and any lubricant option. In addition to water, oil is the most common lubricant. This may pose inhalation hazards, contact hazards and, because friction always generates heat, the dangers of combustible material.
Abrasive materials that are too hard or too rough can get rid of too much material or leave unwanted scratches. In addition to unsightly, scratching can have other more serious effects. Excessive abrasion or scratching may be:
- reduces or destroys usability (as in the case of optical lens scratches and compact discs or blunt knives);
- trap dirt, water, or other materials;
- increasing surface area (enabling greater chemical reactivity such as increased rusting which is also affected by material trapped in scratches);
- scrape or penetrate layers (such as paint or chemicals or wear-resistant coatings);
- too quickly causes a lost object (such as slats or gems);
- increases friction (like on cushions and glittering pistons).
A smoother or softer abrasive will tend to leave a much smoother scratch that may not even be visible to the naked eye ("uncompleted resolution"); Softer abrasives may not even significantly erode certain objects. Softer or finer aerations will take longer to cut, as they tend to cut deeper than rougher and tougher materials. Also, a softer abrasive can become less effective faster because the abrasive itself has abrasion. This allows a fine polisher to be used in metal polishing and lenses where a smoother series of scratches tends to take on a much more glossy or reflective appearance or greater transparency. Very fine abrasives can be used to coat the dead skin for a throat-cut razor, however, the purpose of stropping is not to erode the material but to straighten the spines at the ends. The final stage of sharpening Japanese sword is called polishing and can be a superfinishing form.
Different structural or structural modifications can be made to change the cutting properties of abrasives.
Another very important consideration is price and availability. Diamonds, for a long time considered the hardest substances that exist, are actually softer than fullerite and harder aggregate diamond nanorods, both of which have been synthesized in the laboratory, but no commercial process has yet been developed. The diamond itself is expensive because of the scarcity of nature and the cost of synthesizing it. Bauxite is a very common ore which, along with a fairly high corundum hardness, contributes to corundum status as a cheap, common abrasive.
Thoughts should be given to the desired task of using hard and precise abrasives. On the one hand, using too-hard abrasive waste by wearing it when a cheaper and less harsh abrasion will suffice. At the other end, if the abrasive material is too soft, the abrasion does not occur in a timely fashion, effectively disposing of the abrasive as well as the costs associated with the loss of time.
Another example of abrasion
Apart from the aforementioned use of shaping and finishing, abrasives can also be used to prepare surfaces for such applications as adhesive paints. Overly smooth surfaces can prevent paint and adhesives from sticking strongly as irregular surfaces can allow. Rubber tire repair kits (which, in particular bicycles, are actually patches for inner tubes rather than tires) require the use of abrasives so that self-vulcanised cement will be strongly attached.
Accidentally, people who use knives on glass or metal cutting boards fool their knives. The pressure at the tip of the blade can easily make microscopic (or even macroscopic) pieces on the board. This piece is the source of ready-made abrasive material as well as this abrasive full channel through which the edge slides. For this reason, and regardless of health benefits, wooden planks are much more desirable. A similar incident arises with a glass cutter. The glass cutters have a circular blade designed to roll not slide. They should never retrace the pieces that have been done.
Unwanted Abrasion may result from the presence of carbon in the internal combustion engine. While smaller particles are readily transported by the lubrication system, larger carbon particles can obscure components with close tolerance. Carbon arises from overheating of engine oil or from incomplete combustion. This soot can contain recorded fullerenes for their extreme hardness - and small size and limited quantities that tend to limit its effect.
See also
- Abrasion (mechanical)
- Abrasive blasting
- Erosion
- Abrasive steel
- Tribology
- Wear
References
Further reading
- Momber, A.W., Kovacevic, R.: The Jet Air Abrasive Machining Principles. Springer, London, 1998.
- Momber, A.W.: Blasting Cleansing Technologies. Springer Publ., Heidelberg, 2008
- Metal and Composite Finishing Inc., Abrasive Technical Information
External links
- Abrasion in Curlie (based on DMOZ)
- Ã, "Abrasive". The New Encyclopedia of Collier . 1921.
Source of the article : Wikipedia
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