Processing of hard materials. Hard alloy. Brands, characteristics, application. Carbide tool. Waterjet cutting: advantages and features
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. The bakelite bond has a weaker adhesion to the abrasive grain than the 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 from 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:
- during 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 end of the wheel, 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 coarse thread grinding of parts. 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 one.
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.
Depending on the requirements for the final product heat treatment produced by various methods.
Drying processes used in the production of final intermediate products in the form of granules, briquettes, as well as for dehydration of solutions, sludge and suspensions; by subsequent drying, firing or sintering of the granular or shaped material, the final product is obtained. In these cases, the regularities of heat and mass transfer are the same as during the main technological processes of drying in the chemical industry and in the production of building materials.
V sintering process of agglomerates and preforms, powder particles are combined into a monolithic polycrystalline solid with properties close to those of a compact material. The heat treatment process consists of two stages.
The first stage - removal of the technological binder - occurs at the temperatures of evaporation and melting of the binder and ends at the temperature of the beginning of sintering of the powder particles. The second stage - sintering - begins at a temperature corresponding to the mutual sintering of particles to each other, and continues until the temperature of obtaining a monolithic body, which is approximately 0.8 of the melting temperature of the ceramic material. The firing mode is selected based on the chemical and granulometric composition of the waste mixture, the molding or pressing method, as well as the size and type of the product.
During sintering, the initial charge (formed or pressed) is a thermodynamically unstable disperse system with a large supply of free energy.
The sintering process can be conventionally divided into three stages.
At the first stage, the driving force is the excess of free surface energy of fine particles, which tends to compress the workpiece due to the arising pressure and reduce its free surface. The particles slide along the grain boundaries, which causes the workpiece to compact and shrink.
In the second stage, the particles are baked at the contact points created in the first stage. During firing, the contacts between the particles expand, and the shape and size of the pores are continuously changing. The kinetics of this process is determined by the speed of the viscous flow of the medium in which the pores are located. At this stage, the viscous flow of the medium is determined by the mechanism of surface diffusion of atoms over the surfaces of sintering particles to the region of the contact isthmus.
At the third stage, only closed isolated pores remain in the sintered body, and further compaction is possible only by reducing their number and volume (healing process). The final sintering stage is the longest.
Pyrolysis process finds application in the processing of wood waste, plastics, rubber products, solid waste and oil refining sludge and is the process of decomposition of wood waste, other plant materials when they are heated to a temperature of 450-1050 ° C without access to air. This produces gaseous and liquid products, as well as solid coal.
native remainder ( charcoal in wood processing, carbon black in tire disposal).
Depending on the heating temperature, pyrolysis plants are divided into low-temperature (450-500 ° C), characterized by a minimum gas output, a maximum amount of resins, oils and solid residues; medium-temperature (up to 800 ° C) with an increased yield of pyrolysis gas and a reduced yield of resins and oils; high-temperature (over 800 ° C) with maximum gas output and minimum - resinous products.
High temperature intensifies waste disposal. The reaction rate grows exponentially with increasing temperature, and heat losses increase linearly. In this case, a more complete yield of volatile products occurs and the volume of the resulting solid residue is reduced. During pyrolysis, the temperature range of 1050-1400 ° C is undesirable, since it leads to the formation of slags, especially in MSW.
The pyrolysis process is carried out in batch or continuous furnaces of various designs (chamber, tunnel, mine, with moving layers) with external and internal heating. At the initial stage, with an increase in temperature, endothermic processes occur. When wood or other plant waste is heated to 150 ° C, moisture is removed, and at temperatures of 170-270 ° C, CO and CO2 gases and small amounts of methyl alcohol and acetic acid are formed. Exothermic transformations begin at 270-280 ° C. The yield of non-condensable gases, such as CO and C0 2, decreases and at the same time the yield of other gaseous and vaporous substances (CH 4, C 2 H 4, H 2), as well as methyl alcohol and acetic acid, increases. The speed of the process is influenced by the size of the pieces of recyclable waste, their moisture content and temperature.
The gases leaving the furnace cool down and release valuable components from them. The resulting charcoal is used in the production of active carbon, black powder and other processes.
The question 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 accuracy that was achieved on 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, the cutting edge is high pressure, 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, for example 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. In this way, the CBN keeps the cutting edge line continuous, which makes it possible to obtain best values roughness of the treated surface. 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 firm 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 aluminum oxide 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 speeds cutting and reducing 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.
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 | Heat 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 U, followed by a number characterizing the mass content of carbon in the 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 of carbon tool steels
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
These materials have limited areas of application: carbon ones are mainly used for the manufacture of locksmith tools, and alloyed ones - for thread-forming, 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, steel 11R3AM3F2 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
The chemical composition of cast high-speed steels
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.
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 by the mass fraction of 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 ISO standard there are three groups of applicability of carbide cutting tools: group P - for processing materials that give drainage chips; group K - breakage shavings and group M - for processing 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 - area of processing 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 as finished plates of various shapes and sizes, degrees of accuracy U and M, as well as blanks of plates. The fields of application of these alloys are similar to those of two-carbide carbide alloys under shock-free loading.
8.4. Mineral ceramics (GOST 26630-75) and superhard materialsMineral 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
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 CBNRecently, 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
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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, which 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 temperatures. No flammable substances are used when cutting, which significantly reduces the risk of 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 steel sheet and many thin sheets stacked together. This saves time and improves 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;
