Hard alloy. Brands, characteristics, application. Carbide tool. The best connections for machining hard materials Waterjet cutting: benefits and features

Instrumental materials are those whose main purpose is to equip the working part of the instruments. These include tool carbon, alloyed and high-speed steels, hard alloys, mineral ceramics, superhard materials.

Basic properties of tool materials

Tool material	Heat resistance 0 С	Flexural strength, MPa	Microhardness, НV	Thermal conductivity coefficient, W / (mChK)
Carbon steel Alloy steel High speed steel Hard alloy Mineraloceramics Cubic nitride				8.1. Tool steels. By chemical composition, alloying degree, tool steels are divided into tool carbon, tool alloyed and high-speed steels. The physical and mechanical properties of these steels at normal temperatures are quite close, they differ in heat resistance and hardenability during quenching. In alloyed tool steels, the mass content of alloying elements is insufficient to bind all carbon into carbides; therefore, the heat resistance of steels of this group is only 50-100 0 C higher than the heat resistance of carbon tool steels. In high-speed steels, they tend to bind all carbon into carbides of alloying elements, while eliminating the possibility of the formation of iron carbides. Due to this, the softening of high-speed steels occurs at higher temperatures. Tool carbon (GOST 1435-74) and alloyed (GOST 5950-73) steels. The main physical and mechanical properties of tool carbon and alloy steels are given in the tables. Tool carbon steels are designated by the letter Y, followed by a number characterizing the mass content of carbon in steel in tenths of a percent. So, in steel grade U10, the mass content of carbon is one percent. The letter A in the designation corresponds to high-quality steels with a reduced mass content of impurities. Chemical composition carbon tool steels steel grade steel grade phosphorus - 0.035%, chromium - 0.2% nickel - 0.25%, copper - 0.25% Phosphorus - 0.03%, chromium - 0.15% copper - 0.2% In tool alloy steels, the first figure characterizes the mass content of carbon in tenths of a percent (if there is no figure, then the carbon content in it is up to one percent). The letters in the designation indicate the content of the corresponding alloying elements: G - manganese, X - chromium, C - silicon, B - tungsten, F - vanadium, and the numbers indicate the percentage of the element. Tool alloyed steels of deep hardenability of grades 9ХС, ХВСГ, Х, 11Х, ХВГ are distinguished by small deformations during heat treatment. The chemical composition of low alloy tool steels steel grade e 0,4 e 0,3 e 0,35 e 0,35 e 0,35 e 0,3 Notes: B1 low alloy steel chemistry is set to retain the benefits of carbon steels by improving hardenability and reducing sensitivity to overheating Steel type ХВ5 have increased hardness (HRC up to 70) due to high carbon content and reduced manganese content Chromium steels of type X belong to steels with increased hardenability Steels alloyed with manganese type 9XC are resistant to hardness reduction during tempering These materials have limited areas of application: carbon ones are mainly used for the manufacture of locksmith tools, and alloyed ones - for threading, woodworking and long tools (CVG) - broaches, reamers, etc. 8.2. High speed steels (GOST 19265-73) The chemical composition and strength characteristics of the main grades of these steels are given in the tables. High-speed steels are designated by letters corresponding to carbide-forming and alloying elements: P - tungsten, M - molybdenum, F - vanadium, A - nitrogen, K - cobalt, T - titanium, C - zirconium). The letter is followed by a number indicating the average mass content of the element in percent (the chromium content of about 4 percent is not indicated in the designation of grades). The number at the beginning of the steel designation indicates the carbon content in tenths of a percent (for example, 11R3AM3F2 steel contains about 1.1% C; 3% W; 3% Mo and 2% V). The cutting properties of high-speed steels are determined by the volume of the main carbide-forming elements: tungsten, molybdenum, vanadium and alloying elements - cobalt, nitrogen. Vanadium, due to its low mass content (up to 3%), is usually not taken into account, and the cutting properties of steels are determined, as a rule, by a tungsten equivalent equal to (W + 2Mo)%. In the price lists for high-speed steels, three groups of steels are distinguished: steels of the 1st group with a tungsten equivalent of up to 16% without cobalt, steels of the 2nd group - up to 18% and a cobalt content of about 5%, 2 hundred or the 3rd group - up to 20% and a cobalt content of 5-10%. Accordingly, the cutting properties of these groups of steels also differ. The chemical composition of high-speed steels steel grade e 0,5 e 0,5 e 0,5 e 0,5 e 0,5 The chemical composition of cast high-speed steels steel grade In addition to the standard ones, special high-speed steels are also used, containing, for example, titanium carbonitrides. However, the high hardness of the blanks of these steels, the complexity of machining are not conducive to widespread use. Powder high-speed steels R6M5-P and R6M5K5-P are used in the processing of difficult-to-machine materials. The high cutting properties of these steels are determined by a special fine-grained structure, which contributes to increased strength, a reduced radius of curvature of the cutting edge, improved machinability by cutting and especially grinding. Currently, industrial tests are underway for tungsten-free high-speed steels with a high content of various alloying elements, including aluminum, malibden, nickel and others. One of the significant disadvantages of high-speed steels is associated with carbide heterogeneity, i.e. with an uneven distribution of carbides over the section of the workpiece, which, in turn, leads to uneven hardness of the cutting blade of the tool and its wear. This disadvantage is absent in powder and maraging (with a carbon content of less than 0.03%) high-speed steels. steel grade Approximate purpose and technological features Can be used for all types of cutting tools when processing common construction materials. Possesses high manufacturability. For roughly the same purposes as P18 steel. Poorly polished. For tools of a simple shape that do not require a large volume of grinding operations; used for processing conventional construction materials; has increased plasticity and can be used for the manufacture of tools by plastic deformation methods; reduced grindability. For all types of cutting tools. Can be used for tools with shock loads; a narrower range of quenching temperatures than that of R18 steel, an increased tendency to decarburization. Finishing and semi-finishing tools / shaped cutters, reamers, broaches, etc. / when processing structural steels. The same as the R6M5 steel, but in comparison with the R6M steel it has a slightly higher hardness and lower strength. They are used for the manufacture of tools of a simple shape that do not require a large volume of grinding operations. Recommended for processing materials with increased abrasive properties / fiberglass, plastics, ebonite, etc. / for finishing tools working at medium cutting speeds and small cross-sections; reduced grindability. For finishing and semi-finishing tools operating at medium cutting speeds; for materials with increased abrasive properties; recommended instead of steels R6F5 and R14F4, as steel with better grindability with approximately the same cutting properties. R9M4K8, R6M5K5 For processing high-strength stainless, heat-resistant steels and alloys in conditions of increased heating of the cutting edge; grindability is somewhat reduced. R10K5F5, R12K5F5 For processing high-strength and hard steels and alloys; materials with increased abrasive properties; grindability is low. For processing steels and alloys of increased hardness; vibration-free finishing and semi-finishing; reduced grindability. For tools of simple shape when processing carbon and alloy steels with a strength of not more than 800 MPa. R6M5K5-MP, R9M4K8-MP (powder) For the same purposes as steel R6M5K5 and R9M4K8; have better grindability, are less deformed during heat treatment, have greater strength, show more stable performance properties. 8.3. Hard alloys (GOST 3882-74) Hard alloys contain a mixture of grains of carbides, nitrides, carbonitrides of refractory metals in binders. Standard grades of hard alloys are made on the basis of tungsten, titanium, tantalum carbides. Cobalt is used as a binder. The composition and basic properties of some grades of hard alloys for cutting tools are shown in the table. Physical and mechanical properties of one-, two- and three-carbide hard alloys Composition physical and mechanical properties of tungsten-free hard alloys Depending on the composition of the carbide phase and the binder, the designation of hard alloys includes letters characterizing carbide-forming elements (B - tungsten, T - titanium, the second letter T - tantalum) and a binder (letter K - cobalt). The mass fraction of carbide-forming elements in monocarbide alloys containing only tungsten carbide is determined by the difference between 100% and the mass fraction of the binder (the number after the letter K), for example, the VK4 alloy contains 4% cobalt and 96% WC. In two-carbide WC + TiC alloys, the number after the letter of the carbide-forming element is determined mass fraction carbides of this element, the next figure is the mass fraction of the binder, the rest is the mass fraction of tungsten carbide (for example, the T5K10 alloy contains 5% TiC, 10% Co and 85% WC). In three-carbide alloys, the number after the letters TT means the mass fraction of titanium and tantalum carbides. The number behind the letter K is the mass fraction of the bond, the rest is the mass fraction of tungsten carbide (for example, the TT8K6 alloy contains 6% cobalt, 8% titanium and tantalum carbides and 86% tungsten carbide). In metalworking, the ISO standard distinguishes three groups of applicability of carbide cutting tools: group P - for processing materials that give drainage chips; group K - fractured shavings and group M - for machining various materials(universal hard alloys). Each area is divided into groups and subgroups. Hard alloys are generally produced in the form of plates of various shapes and accuracy: brazed (glued) - in accordance with GOST 25393-82 or replaceable multifaceted - in accordance with GOST 19043-80 - 19057-80 and other standards. Multifaceted inserts are produced both from standard grades of hard alloys and from the same alloys with single-layer or multi-layer superhard coatings of TiC, TiN, aluminum oxide and other chemical compounds. Coated plates have increased durability. To the designation of plates from standard grades of hard alloys coated with titanium nitrides add - the marking of the letters KIB (TU 2-035-806-80), and to the designation of alloys according to ISO - the letter C. Plates are also produced from special alloys (for example, according to TU 48-19-308-80). Alloys of this group (group "MC") have higher cutting properties. The alloy designation consists of the letters MC and a three-digit (for uncoated plates) or four-digit (for titanium carbide coated plates) number: The 1st digit of the designation corresponds to the area of ​​application of the alloy according to the ISO classification (1 - processing of materials that give drainage chips; 3 - processing of materials that give breakage chips; 2 - processing area corresponding to area M according to ISO); The 2nd and 3rd digits characterize the subgroup of applicability, and the 4th digit - the presence of coverage. For example, MC111 (analogue of standard T15K6), MC1460 (analogue of standard T5K10), etc. In addition to finished plates, workpieces are also produced in accordance with OST 48-93-81; the designation of blanks is the same as for finished plates, but with the addition of the letter Z. Tungsten-free hard alloys are widely used as materials that do not contain scarce elements. Tungsten-free alloys are supplied in the form of finished plates of various shapes and sizes, degrees of accuracy U and M, as well as plate blanks. The fields of application of these alloys are similar to the fields of application of two-carbide carbide alloys under shock-free loading. It is applied for Fine turning with a small cut, final threading, reaming and other similar types of processing of gray cast iron, non-ferrous metals and their alloys and non-metallic materials (rubber, fiber, plastic, glass, fiberglass, etc.). Cutting sheet glass Finishing (turning, boring, tapping, reaming) of hard, alloyed and bleached cast irons, case-hardened and hardened steels, and highly abrasive non-metallic materials. Rough turning with an uneven cut section, rough and fine milling, reaming and boring of normal and deep holes, rough countersinking when machining cast iron, non-ferrous metals and alloys, titanium and its alloys. Finishing and semi-finishing of hard, alloyed and bleached cast irons, hardened steels and some grades of stainless high-strength and heat-resistant steels and alloys, especially alloys based on titanium, tungsten and molybdenum (turning, boring, reaming, threading, scraping). Medium machining of heat-resistant steels and alloys, stainless steels austenitic class, special hard cast irons, hardened cast iron, hard bronze, light metal alloys, abrasive non-metallic materials, plastics, paper, glass. Machining hardened steels, as well as raw carbon and alloy steels with thin cut sections at very low cutting speeds. Finishing and semi-finishing turning, boring, milling and drilling in gray and ductile cast iron as well as bleached cast iron. Continuous turning with small cross-sections of steel castings, high-strength, stainless steels, including hardened ones. Processing of non-ferrous alloys and some grades titanium alloys when cutting with small and medium cut sections. Rough and semi-rough turning, preliminary threading with turning tools, semi-finishing milling of solid surfaces, reaming and boring of holes, countersinking of gray cast iron, non-ferrous metals and their alloys and non-metallic materials. Rough flow with an uneven cut and interrupted cutting, planing, rough milling, drilling, rough reaming, rough countersinking of gray cast iron, non-ferrous metals and their alloys and non-metallic materials. Machining of stainless, high-strength and heat-resistant hard-to-machine steels and alloys, including titanium alloys. Roughing and semi-roughing of hard, alloyed and bleached cast irons, some grades of stainless, high-strength and heat-resistant steels and alloys, especially alloys based on titanium, tungsten and molybdenum. Manufacturing of some types of monolithic tools. Drilling, countersinking, reaming, milling and gear hobbing of steel, cast iron, some difficult-to-machine materials and non-metals with solid carbide, small-sized tools. Cutting tool for wood processing. Fine turning with a small cut section (t pa diamond cutting); tapping and reaming of unhardened and hardened carbon steels. Semi-rough turning with continuous cutting, finishing turning with interrupted cuts, tapping with turning tools and rotating heads, semi-finishing and finishing milling of solid surfaces, reaming and boring of pre-machined holes, finishing countersinking, reaming and other similar types of processing of carbon and alloy steels. Rough turning with an uneven cut section and continuous cutting, semi-finishing and finishing turning with interrupted cutting; rough milling of solid surfaces; reaming of cast and forged holes, rough countersinking and other similar types of processing of carbon and alloy steels. Rough turning with an uneven cut section and interrupted cutting, shaped turning, cutting off with turning tools; finishing planing; rough milling of intermittent surfaces and other types of processing of carbon and alloy steels, mainly in the form of forgings, stampings and castings for crust and scale. Heavy rough turning of steel forgings, stampings and castings on a crust with shells in the presence of sand, slag and various non-metallic inclusions, with an uneven cut section and the presence of impacts. All types of planing of carbon and alloy steels. Heavy rough turning of steel forgings, stampings and castings on a crust with shells in the presence of sand, slag and various non-metallic inclusions with a uniform cut section and the presence of impacts. All types of planing of carbon and alloy steels. Heavy rough milling and carbon and alloy steels. Roughing and semi-finishing of some grades of difficult-to-machine materials, austenitic stainless steels, low-magnetic steels and heat-resistant steels and alloys, including titanium ones. Milling of steel, especially milling deep grooves and other types of processing that place increased demands on the resistance of the alloy to thermal mechanical cyclic loads. 8.4. Mineral ceramics (GOST 26630-75) and superhard materials Mineral ceramic tool materials have high hardness, heat and wear resistance. They are based on alumina (silicon oxide) - oxide ceramics or a mixture of silicon oxide with carbides, nitrides and other compounds (cermets). The main characteristics and fields of application of various grades of mineral ceramics are given in the table. The shapes and sizes of replaceable multifaceted ceramic plates are determined by the GOST 25003-81 * standard. In addition to traditional grades of oxide ceramics and cermets, oxide-nitride ceramics are widely used (for example, ceramics of the "cortinit" grade (a mixture of corundum or aluminum oxide with titanium nitride) and silicon nitride ceramics - "silinit-R". Physical and mechanical properties of tool ceramics Processed material Hardness Ceramic brand Cast iron gray VO-13, VSh-75, TsM-332 Malleable cast iron VSh-75, VO-13 Bleached cast iron VOK-60, ONT-20, V-3 Structural carbon steel VO-13, VSh-75, TsM-332 Structural alloy steel VO-13, VSh-75, TsM-332 Refined steel VSh-75, VO-13, VOK-60 Silinit-R Case-hardened steel VOK-60, ONT-20, V-3 VOK-60, V-3, ONT-20 Copper alloys Nickel alloys Silinit-R, ONT-20 Synthetic superhard materials are made either on the basis of cubic boron nitride - CBN, or on the basis of diamonds. Materials of the CBN group have high hardness, wear resistance, low coefficient of friction and inertness to iron. The main characteristics and effective areas of use are shown in the table. Physical and mechanical properties of STM based on CBN IN recent times this group also includes materials containing the Si-Al-O-N ( trademark"sialon"), based on silicon nitride Si3N4. Synthetic materials are supplied in the form of blanks or ready-made replacement plates. On the basis of synthetic diamonds, such brands are known as ASB - synthetic diamond "ballas", ASPK - synthetic diamond "carbonado" and others. The advantages of these materials are high chemical and corrosion resistance, minimal radius of curvature of the blades and the coefficient of friction with the processed material. However, diamonds have significant disadvantages: low bending strength (210-480 MPa); reactivity to some of the fats contained in the coolant; dissolution in iron at temperatures of 750-800 C, which practically excludes the possibility of their use for processing steels and cast iron. Mainly, polycrystalline synthetic diamonds are used for processing aluminum, copper and their alloys. Purpose of STM based on cubic boron nitride Material grade Application area Composite 01 (Elbor R) Thin and finish turning without impact and face milling of hardened steels and cast irons of any hardness, carbide alloys (Co => 15%) Composite 03 (Ismit) Finishing and semi-finishing of hardened steels and cast irons of any hardness Composite 05 Pre and final turning without impact on hardened steels (HRC e<= 55) и серого чугуна, торцовое фрезерование чугуна Composite 06 Finish turning of hardened steels (HRC e<= 63) Composite 10 (Hexanite R) Preliminary and final turning with and without impact, face milling of steels and cast irons of any hardness, hard alloys (Co => 15%), interrupted turning, machining of welded parts. Roughing, semi-roughing and finishing turning and milling of cast irons of any hardness, turning and boring of steels and copper-based alloys, cutting along the cast skin Composite 10D Preliminary and final turning, including with impact, of hardened steels and cast irons of any hardness, wear-resistant plasma surfacing, face milling of hardened steels and cast irons.

A high-tech and complex process that requires special equipment and special tools. This is due to the fact that such alloys have high elasticity and strength, and therefore strongly resist cutting, drilling, grinding and other mechanical treatments. At the same time, the quality of the corresponding process largely depends on the characteristics of the metal and the correct selection of the cutting tool.

Features of hard alloys

Hard-to-machine metals include heat-resistant and stainless steels and alloys. These materials represent a solid solution of the austenitic class; therefore, they are characterized by such qualities as high resistance to corrosion, the ability to work in a stressed state for a long time, and resistance to chemical destruction. In addition, some types of these metals are characterized by a structure of high dispersion. Due to this, the sliding process practically does not occur.

Processing is also complicated for the following reasons:

• when cutting, the material is hardened;
• alloys of this nature have low thermal conductivity, and therefore the contact part of the workpiece and the tool begin to set;
• the original strength is retained even at very high temperatures;
• high abrasion ability of alloys leads to the formation of inclusions that negatively affect the tool;
• The vibration resistance of metals is caused by the uneven flow of the cutting process, which means that it will not be possible to obtain the desired processing quality.

Tool selection

In order to avoid all the problems described above and to carry out high-quality machining of hard alloys, it is first of all necessary to choose the right tool. It must be made of metal that has better cutting properties than the workpiece. At the same time, experts recommend using carbide cutters for preliminary processing, and high-speed cutting tools for finishing. The latter include steel grades R14F4, R10K5F5, R9F5, R9K9.

For the manufacture of tools from carbide metals, three types of alloys are used:

• T30K4, T15K6, VKZ - wear-resistant;
• T5K7, T5K10 - are distinguished by high viscosity;
• VK6A, VK8 - insensitive to shock, have the least resistance to wear.

To strengthen the tools and improve their performance, the second layer of hard alloy metal, cyanidation, chromium plating, and cladding are additionally applied.

Coolant

The correct selection of coolants and the way they are used is an equally important process if it is necessary to process hard alloys. For drilling, experts recommend using mineral-based materials. They especially increase productivity when working with titanium, which is very difficult to work with. For turning of alloy steels, semi-synthetic cutting fluids are suitable, for honing and grinding cast iron - a liquid without mineral oils. There are also versatile materials that are very beneficial to use if the nature of metal processing is constantly changing.

The most optimal way of supplying coolant when working with hard metals is considered to be high-pressure, in which the liquid is supplied with a thin stream to the rear wall of the tool. Spraying liquid and cooling with carbon dioxide are equally effective. All this allows to increase the tool life and improve the quality of processing.

equipment requirements

Equipment for the processing of hard metals is strikingly different from standard machine tools. Similar models differ:

• increased rigidity of all mechanisms;
• vibration resistance;
• high power;
• the presence of channels for the removal of chips;
• special seating positions for fixing the short tool.

Choosing a bond of abrasive tools

The bond determines the strength and hardness of the tool, has a great influence on the modes, productivity and quality of processing. Bundles are inorganic (ceramic) and organic (bakelite, vulcanite).
CERAMIC BOND possesses high fire resistance, water resistance, chemical resistance, well retains the profile of the working edge of the wheel, but is sensitive to shock and bending loads. The ceramic-bonded tool is used for all types of grinding except for roughing (due to the fragility of the bond): for cutting and slotting narrow grooves, flat grinding of the grooves of ball bearing rings. The ceramic-bonded tool retains its profile well, has a high porosity, and removes heat well.
BAKELITE BOND has a higher strength and elasticity than ceramic. An abrasive tool on a bakelite bond can be made of various shapes and sizes, including very thin ones - up to 0.5 mm for cutting and cutting work. The disadvantage of bakelite binder is its low resistance to the action of coolants containing alkaline solutions. When on bakelite bunch, the coolant should not contain more than 1.5% alkali. Bakelite bond has a weaker adhesion to abrasive grain than ceramic bond, therefore the tool on this bond is widely used in surface grinding operations where self-sharpening of the wheel is necessary. The tool on a bakelite bond is used for rough roughing work performed manually and on suspended walls: flat grinding with the end of a circle, cutting and cutting grooves, sharpening tools, when processing thin products, where a burn is dangerous. Bakelite bond has a polishing effect.

Selection of the grade of abrasive material

Abrasive materials(fr. abrasif - grinding, from Latin abradere - to scrape off) are materials with high hardness and are used for surface treatment of various materials. are used in the processes of grinding, sharpening, polishing, cutting materials and are widely used in the blank production and finishing of various metallic and non-metallic materials. Natural abrasives - flint, emery, pumice, corundum, garnet, diamond and others. Artificial: fused alumina, silicon carbide, borazon, elbor, synthetic diamond and others.

ELECTROCORUND NORMAL

It has excellent heat resistance, high adhesion to the binder, mechanical strength of grains and significant viscosity, which is important for performing operations with variable loads. Processing of materials with high tensile strength. This is the roughing of steel castings, wires, rolled products, high-strength and bleached cast irons, malleable cast iron, semi-finishing processing of various machine parts made of carbon and alloy steels in unhardened; and hardened form, manganese bronze, nickel and aluminum alloys. 25A

ELECTROCORUND WHITE

In terms of physical and chemical composition, it is more homogeneous, has a higher hardness, sharp edges, good self-sharpening, better eliminates the roughness of the machined surface in comparison with normal fused alumina Processing of hardened parts made of carbon, high-speed and stainless steels, chrome-plated and nitrided surfaces. Processing of thin parts and tools, sharpening, flat, internal, profile and finishing grinding. 38A

ELECTROCORUND ZIRCONIUM

Fine crystalline, dense and durable material. Tool life for roughing operations is 10-40 times higher than that of a similar tool made of normal electrocorundum. Rough grinding of steel workpieces at high speed, feed and clamping force. Power rough grinding of steel workpieces. 54C

SILICON CARBIDE BLACK

Possesses high hardness, abrasion and brittleness. The grains are in the form of thin plates, which increases their brittleness in work. Processing of hard materials with low tensile strength (cast iron, bronze and brass castings, hard alloys, precious stones, glass, marble, graphite, porcelain, hard rubber, bones, etc.) etc.), as well as very viscous materials (heat-resistant steels, alloys, copper, aluminum, rubber). 63C

SILICON CARBIDE GREEN

It differs from black silicon carbide with increased hardness, abrasive ability and brittleness For machining parts made of cast iron, non-ferrous metals, granite, marble, hard alloys, machining titanium, titanium-tantalum hard alloys, honing, finishing work for parts made of gray cast iron, nitrided and ball bearing become. 95A

ELECTROCORUND CHROMTITANIC

Has a higher mechanical strength and abrasive ability compared to normal fused alumina

Rough grinding with high metal removal

Selecting the grit of the tool

Grain	Treatment type
LargeF6-F24	Roughing operations with a large depth of cut, cleaning of workpieces, castings. Processing of materials that cause grease on the surface of the circle (brass, copper, aluminum).
F24 - F36	Surface grinding with a wheel end, sharpening cutters, dressing an abrasive tool, cutting off.
AverageF30 - F60	Preliminary and combined grinding, sharpening of cutting tools.
F46 - F90	Fine grinding, processing of profiled surfaces, sharpening of small tools, grinding of fragile materials.
SmallF100-F180

Finishing grinding, finishing of hard alloys, finishing of cutting tools, steel blanks, sharpening of thin blades, preliminary honing.

Coarse-grained tools are used:
- for roughing and preliminary operations with a large depth of cut, when large allowances are removed;
- when working on machines of high power and rigidity;
- when processing materials that cause filling of the pores of the wheel and salting of its surface, for example, when processing brass, copper and aluminum;
- with a large area of ​​contact between the wheel and the workpiece, for example, when using high wheels, with flat grinding with the wheel end, with internal grinding.
Medium and fine-grained tools are used:
- to obtain a surface roughness of 0.320-0.080 microns;
- when processing hardened steels and hard alloys;
- during final grinding, sharpening and finishing of tools;
- with high requirements for the accuracy of the processed profile of the part.
With a decrease in the size of abrasive grains, their cutting ability increases due to an increase in the number of grains per unit of the working surface, a decrease in the radius of rounding of grains, and less wear of individual grains. A decrease in the grain size leads to a significant decrease in the pores of the wheel, which necessitates a decrease in the grinding depth and the size of the allowance removed during the operation. The finer the abrasive grains in the tool, the less material is removed from the workpiece per unit of time. However, fine-grained tools are less self-sharpening than coarser-grit tools, resulting in dulling and salting faster. A rational combination of the processing mode, tool dressing and grain size allows obtaining high accuracy and excellent surface treatment quality.

Tool hardness selection

O, P, Q Profile grinding, interrupted surface grinding, honing and thread grinding of coarse steps. AverageM-N Surface grinding with segments and annular discs, honing and thread grinding with bakelite-bonded discs. Medium softK-L Finishing and combined round, external centerless and internal grinding of steel, surface grinding, thread grinding, sharpening of cutting tools. SoftH-F Sharpening and finishing of cutting tools equipped with hard alloy, grinding of difficult-to-machine special alloys, polishing.

The hardness of the tool largely determines the productivity of labor during processing and the quality of the processed.
Abrasive grains, as they become dull, must be renewed by chipping and chipping of particles. If the wheel is too hard, the binder continues to hold the dull grains that have lost their cutting ability. At the same time, a lot of power is consumed for work, the products heat up, their warpage is possible, traces of cutting, scratches, burns and other defects appear on the surface. If the wheel is too soft, the grains, which have not lost their cutting ability, crumble, the wheel loses its correct shape, its wear increases, as a result of which it is difficult to obtain parts of the required size and shape. In the process of processing, vibration appears, more frequent dressing of the wheel is necessary. Thus, one should take a responsible approach to the choice of the hardness of the abrasive tool and take into account the characteristics of the workpieces.

The issue of finishing hardened steel is solved in modern production mainly by abrasive processing. Until recently, this was due to the different level of equipment for grinding and blade processing. Lathes could not guarantee the same precision that was achieved with grinding machines. But now modern CNC machines have sufficient movement accuracy and rigidity, so the share of turning and milling of hard materials is constantly expanding in many industries. Turning hardened workpieces has been used in the automotive industry since the mid-eighties of the last century, but today a new era begins in this type of processing.

Heat-treated workpieces

Many steel parts require heat treatment or case hardening to acquire additional wear resistance and the ability to withstand significant loads. Unfortunately, high hardness negatively affects the machinability of such parts. Gear parts and various shafts and axles - typical hardened parts are turned, dies and molds are hardened milled. Heat-treated parts - rolling elements, as a rule, require finishing and finishing, which removes form errors and ensures the required accuracy and surface quality. As for parts of dies and molds, now there is a tendency to process them in a hardened state already at the stage of roughing. This leads to a significant reduction in the production time of the stamp.

Solid material handling

The processing of parts after heat treatment is an issue that requires a flexible approach. The range of solutions depends on the type of tool material selected for machining. For a tool, the ability to process hard materials means high heat resistance, high chemical inertness, and abrasion resistance. Such requirements for the tool material are determined by the machining process itself. When cutting hard materials, high pressure is applied to the cutting edge, which is accompanied by the release of a large amount of heat. Higher temperatures help the process by softening the chips, thereby reducing cutting forces, but negatively affect the tool. Therefore, not all tool materials are suitable for processing heat-treated parts.

Carbide grades are used to machine materials with hardness up to 40HRc. For this, we recommend fine-grained carbide alloys with a sharp cutting edge, which are highly resistant to abrasive wear and have high thermal and plastic deformation resistance. Uncoated cemented carbides such as H13A from Sandvik Coromant have these properties. But it is also possible to successfully use grades with wear-resistant coatings for finishing and P05 and K05 applications, such as GC4015, GC3005.

The most inconvenient workpiece for cutting is a workpiece with a hardness of 40… 50HRc. When working in this range, hard alloys are no longer satisfied with their heat resistance. At the same time, CBN and ceramics wear out quickly. Due to the insufficient hardness of the material being processed, a build-up is formed on the front surface of the tool, causing the cutting edge to chip off when it is torn off. Therefore, the problem of choosing a tool material for work in this range of hardness is solved on the basis of economic considerations. Depending on the serial production, one has to either put up with low productivity and dimensional accuracy when working with hard alloy, or work more efficiently with ceramics and CBN, but with the risk of plate breakage.

At a higher hardness of 50-70HRc, the choice is unambiguously inclined towards machining using a tool with a ceramic or cubic boron nitride cutting part. Ceramic allows even intermittent processing, but provides a slightly higher surface roughness than CBN. CBN machining can achieve roughness up to 0.3Ra, while ceramic produces a surface roughness of 0.6Ra. This is due to different wear patterns of the tool material: under normal conditions, CBN has uniform wear along the flank surface, and microscales are formed on the ceramics. Thus, the CBN keeps the cutting edge line continuous, which allows for better surface roughness values. Cutting conditions for processing hardened materials vary within a fairly wide range. It depends on the workpiece material, processing conditions and the required surface quality. When processing a workpiece with a hardness of 60 HRc with new grades of cubic boron nitride CB7020 or CB7050, the cutting speed can reach 200 m / min. CB7020 is recommended for continuous cutting finishing and CB7050 for finishing heat-treated materials in unfavorable conditions, i.e. with blows. Plates from these grades are produced with a thin titanium nitride coating. According to Sandvik Coromant, this makes it much easier to control insert wear. The company also produces plates from similar grades of cubic boron nitride CB20 and CB50, but without coating.

Various types of ceramics are commonly used for machining hardened steels. Sandvik Coromant currently manufactures all types of ceramics and is actively developing new grades. Oxide ceramics CC 620 is produced on the basis of aluminum oxide with small additions of zirconium oxide to increase strength. It has the highest wear resistance, but it can only be used in good conditions due to its low strength and thermal conductivity. Mixed ceramics CC650 based on alumina with silicon carbide additives are more versatile. It has higher strength and good thermal conductivity, which allows it to be used even with interrupted processing. The so-called whiskey ceramics CC670 has the greatest strength. The composition of which also includes silicon carbide, but in the form of long crystalline fibers that penetrate the base material. The main area of ​​application of this grade of ceramics is the processing of heat-resistant alloys based on nickel, but due to its high strength, it is also used for processing hardened steel in adverse conditions. Cutting data when using ceramic inserts, as well as in the case of cubic boron nitride, vary within wide limits. This is largely due not to differences in the properties of the tool material, but to a variety of processing conditions, when sufficient heating is achieved in the cutting zone and, accordingly, a decrease in forces and wear. Typically, the optimum cutting speed is in the range of 50-200 m / min. Moreover, a decrease in cutting speed does not necessarily lead to an increase in tool life, as is the case with carbide.

New opportunities

Productivity in the processing of hardened materials has so far been achieved through tool design changes and equipment improvements. Now, new tool materials allow working at high speeds, and the geometry of the cutting part to reach high values ​​of working feeds. In addition, the ability to machine parts in one set-up when turning or milling results in a significant reduction in non-productive times.

The amount of feed depends on the geometry of the tip of the cutting tool. For tools with a radial apex, the feed turns out to be rigidly associated with the requirement to ensure a given surface quality. Typical feed rate 0.05 ... 0.2 mm / rev. But now there are inserts on the market called wipers, which allow you to increase it. When machining with such inserts, the feed value can in practice be doubled without affecting the surface quality. The wiper effect occurs by modifying the top of the insert and creating a special large radius wiper that is a continuation of the main corner radius. The wiping cutting edge provides a minimum auxiliary entering angle during insert operation, which allows increasing the working feed without losing the quality of the machined surface. When the feed is increased, the cutting path is halved, and therefore the wear of the insert. The revolutionary thing about this solution is that the increase in productivity is achieved simultaneously with the increase in the resource of the tool.

Wiper inserts were pioneered by Sandvik Coromant and are becoming increasingly popular. For example, for CBN and ceramic inserts, there are already two wiper geometries. WH geometry is the basic geometry for maximum performance. The optional WG geometry provides low cutting forces and is used for high speed machining with high demands on surface finish.

CBN and ceramic wiper inserts take finishing and finishing of hardened materials to new levels of productivity.

The main advantages of turning hardened materials:
high productivity due to high cutting speeds and reduced auxiliary time;
high flexibility of use;
the process is easier than grinding;
no burns;
minimal warpage of the workpiece;
additional productivity increase due to high feed rates when using wiper inserts;
the ability to unify equipment for complete processing of a part;
safe and environmentally friendly processing process.

One of the most efficient ways to cut and handle hard materials is waterjet cutting. It can be used to cut hard materials such as marble and granite, metal, concrete and glass. This type of cutting is widely used in construction in the processing of composite and ceramic materials, sandwich structures.

Waterjet cutting is a highly directional, high-pressure jet of water that hits the material at high speed. Initially, only water was used and the method was called water jet cutting. It was used for processing not too hard materials that required a more delicate effect than other types of cutting. It was optical fiber and cables, laminated materials that do not tolerate high temperatures and the occurrence of a fire hazard.

Later, an abrasive was added to the water, which significantly increased the cutting force of the water jet. Finely dispersed garnet sand is used as an abrasive. With the use of abrasive particles, it has become possible to cut much harder materials such as rocks and metals.

In this regard, waterjet cutting is widely used in various industries, in construction and in the manufacture of monuments. Often, granite is used for the manufacture of monuments, and the prices for monuments in Moscow allow you to make a choice for any wallet. However, not everyone thinks that when ordering a monument, not only the cost of the material and work matters, but also the method of processing.

Waterjet cutting can be called very gentle in the sense that there is no intense impact on the material, which means that its strength is not reduced. To order monuments, prices are calculated based on the method of cutting and processing the stone. Waterjet cutting avoids cracks and chips, and also minimizes stone loss during processing. This is just one of the benefits of waterjet cutting.

Waterjet cutting: advantages and features

1. No strong heating of the material

This parameter is critical both for metal and for natural and artificial stone and tiles. When cutting with an abrasive water jet, the temperature remains in the range of 60-90 ° C. Thus, the material is not exposed to high temperatures, as with other types of cutting, which increases its service life.

2. Versatility of application

The waterjet "blade" can cut both hard and medium hard materials with equal success. True, in the case of working with the latter, it is not necessary to use an abrasive.

3. Excellent cutting quality

The roughness of the cut edge when using waterjet cutting is Ra 1.6. Using this method will help you get a clear cut without unnecessary dust and loss of material.

4. Fire safety

All components used in cutting are fire and explosion proof, including due to low temperature. No flammable substances are used when cutting, which significantly reduces the risk during work.

5. No fusion of the material

This property also follows from the cut temperature. When cutting, the material does not burn either in the adjacent areas or directly on the cut, which is especially important when working with metals.

6. Multipurpose use

Using waterjet cutting, it is possible to cut both 200mm thick steel sheet and many thin sheets stacked together. This saves time and increases productivity.

The disadvantages include the high cost of consumables (namely, sand) and the limited resource of the cutting head and some other components of the machine. The waterjet cutting machine consists of a pump (several) in which water is injected at a pressure of up to 4000 bar, a nozzle, a mixing chamber and a second carbide nozzle.

How waterjet cutting works:

With the help of a pump, water is pumped in at a pressure of up to 4000 bar;