Recommendations for choosing an abrasive tool
Excellent modern the abrasive used for processing various materials is electrocorundum. This is an artificially obtained, by melting, abrasive substance, the structure of which is based on aluminum oxide. Additional components are compounds of iron, titanium and calcium.
Depending on the subtleties of manufacturing technology and qualitative composition , electrocorundum is divided into types:
Choice of abrasive material
Operation description |
Material brand |
Processing of materials with high tear resistance: stripping of steel castings, forgings of high-strength and bleached cast iron, ductile iron, semi-finishing of machine parts made of carbon and alloy steels in non-hardened and hardened form, manganese bronze, nickel and aluminum alloys. |
13A, 14A |
Processing of thin parts and tools: operations in which it is difficult to remove the heat generated during grinding (stamps, teeth, gears, threaded tools, thin knives and blades, steel cutters, drills, woodworking knives, etc.). |
25A |
Processing of hardened and non-hardened steel workpieces, for stripping grinding, grinding with large removal of metal. |
95A |
Processing of hard materials with low tear resistance (cast iron, bronze and brass casting, hard alloys, precious stones, glass, marble, granite, porcelain, hard rubber, etc.). As well as processing of very viscous materials (heat-resistant steels, copper alloys, aluminum, rubber). |
53C, 54C |
To perform work with various parts, an abrasive tool with optimal properties for the materials from which these elements are made is used. One of these characteristics is the grain size of the circle, where the grain size of the grinding tool is considered one of the determining parameters.
Considering these data, abrasive materials are classified as follows:
- шлифзерно;
- шлифопорошки;
- micro-powders;
- thin micro-powders, denoted by certain numbers, comparable to the parameters of the cells of control sieves.
The size of particles related to micro-powder compositions is determined using optics by linear measurement, as well as by photoelectric method, that is, the rate of grain deposition.
Circle grain selection
Operation description |
Material brand |
Stripping operations with a large cutting depth: stripping of blanks, castings, forgings, stamped products. Processing of materials that cause filling of the pores of the circle and salting of its surface (brass, copper, aluminum, etc.). |
F16-F26 |
Flat grinding with the end of the circle, sharpening of medium and large cutters, straightening of an abrasive tool, a segment. |
F24-F36 |
Preliminary and combined grinding (preliminary and final grinding without removing the product from the machine), sharpening of the cutting tool. |
F30-F60 |
Fine grinding, processing of profile surfaces, sharpening of small tools. |
F54-F80 |
Finishing grinding, finishing of hard alloys and cutting tools, pre-honing, sharpening of hard blades. |
F100-F180 |
The hardness of an abrasive tool is an extremely relative concept and is interpreted in different ways. Physical meaning: hardness means the resistance by which the binder prevents the loss of abrasive grains from grinding wheel or other abrasive tool.
Abrasive grains, as they become blunted, should be updated by chipping or coloring the particles. If the circle is too hard, the bundle continues to hold the blunted and lost cutting ability of the grain. As a result, the cutting process stops and is replaced by a friction process with high contact temperatures, while the grinding process consumes a lot of power, the products heat up (their warping is possible), traces of crushing, risks, cauterization and other defects appear on the surface. If the circle is too soft, the grains that have not lost their cutting ability are painted, the geometry of the abrasive tool changes, and its wear increases. As a result, the grinding process becomes ineffective, vibration appears, forced correction of the circle is necessary. In both cases, the intensity of material removal decreases, the surface roughness increases.
In the abrasive industry, a conditional gradation of the abrasive tool according to the degree of hardness is adopted, which is measured by sandblasting contact method or sound contactless (sometimes complex). The degrees of hardness are regulated by the relevant standards and allow identifying the physical and mechanical properties of the abrasive tool.
The contactless method is accepted only in Russian standards and does not cover all types of abrasive tools, there is no exact correspondence with the sandblasting method. But there is an advantage: during the inspection, circles (products) with cracks, uneven hardness, etc. are detected.
When choosing the hardness of an abrasive tool, the following factors should be taken into account:
- chemical and physico-mechanical properties of the processed material;
- the size of the contact area between the grinding tool and the processed product;
- processing modes;
- machine drive power;
- technical condition of the machine.
The degrees of hardness, the approximate ratio of hardness according to different standards and different methods are given in the table below:
Selection of the hardness of the abrasive tool
Operation description |
Hardness |
Grinding, processing of turbine blades. |
H, G |
Grinding of the raceways of the outer hinge, processing (gear grinding) by continuous rolling, grinding of the base end of the bearing ring. Sharpening and fine-tuning of cutting tools made of hard alloys, grinding of hard-to-process alloys. |
H, G, J, I |
Restoration of the barrel of rolling and supporting steel and cast iron rolls, restoration of workings, defects, planned re-grinding of rolls, processing of necks, ledge of the rolling roll, surface treatment of the axis of the rolls, grinding of the connecting rod plane and cover, grinding of the connecting plane on the connecting rod and the lid of the outer hinge separator, rough grinding of the connecting rod planes, grinding of the connecting rod connector plane and cover. |
K, L |
Stripping operation of the roll casting crust, grinding of the base end of the gearbox gear. |
M, N |
Selective stripping, grinding of hot-rolled plates and sheets made of titanium alloys, stripping of surfaces of forged bars and large stampings made of titanium alloys, stripping of rolled sheet surfaces, stripping and reducing the outer diameter of pipes. |
O, P, Q |
Removal of lamps, defects (scratches, drawings), chamfering, metal illumination to identify and remove defects, deburring, grinding of railway special parts after casting, processing of axles of wagon wheels, continuous stripping of defects on the forming surface of titanium alloy rods. |
R, S |
Solid stripping. |
T, U |
Manual sharpening of the cutting tool. |
M, N |
Sharpening of the cutting tool with mechanical and automatic feeding. |
K, L |
Flat grinding with the end of the circle. |
I, J, K, L |
Abrasive tools are manufactured with a predetermined structure. Each structure is assigned its own number. Tools with a structure from No. 1 to No. 12 are manufactured; the higher the structure number, the more bundles and less grinding material per unit volume of the tool. Structures No. 1-4 are called closed (dense), No. 5-8 - medium, No. 9-12 - open.
The following factors influence the choice of the tool structure:
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physical and mechanical properties of the processed material (soft materials with low tear resistance are treated with circles of open structures, hard materials with fine-grained structure and brittle materials with circles of closed structures);
- required finishing quality (for final processing, circles of more closed structures should be used than for preliminary or rough processing; for roughing with a significant allowance, it is recommended to use circles of open structures);
- the amount of pressure during grinding (at high pressures, circles of medium and closed structures should be used).
The choice of the structure of the abrasive tool depending on the grinding operation is given in the table:
Choosing the circle structure
Operation description |
Structure |
Stripping of hard and brittle materials at high pressures. |
1-3 |
Shaped grinding, if necessary, to maintain the profile of the circle, grinding at high and variable loads. |
3, 4 |
Round external grinding, centerless grinding, flat grinding with the periphery of the circle and tool sharpening. |
5-7 |
Flat grinding with the end of the circle, internal grinding. |
7-9 |
Grinding and sharpening of tools. Thread grinding with fine-grained circles. |
8-10 |
Burn-free grinding, gear grinding with high roughness requirements. Rubber grinding, deep grinding. |
11-14 |
Sources :
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Modern abrasive technologies, https://sat-abraziv.ru /
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The Center of Abrasives, https://abrasive.ru /
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Volga Abrasive Plant,https://vabz.ru /