Cutting difficult materials. DjVu. Method of processing solid materials Silicon carbide green
Five-spindle machine from Fives.
Fives Cincinnati XT copy milling machine is equipped with five spindles for machining titanium parts
Kennametal's new spindle connections improve the reliability and productivity of Cincinnati's high volume titanium contour milling machine.
In a period of sustainable development in demanding industries such as aircraft manufacturing civil aviation, the entire supply chain is rigorously tested. This is due to the need to maintain high quality standards and meet deadlines.
Machine builder Fives Cincinnati knows this: The company's plant in Hebron, Kentucky manufactures Cincinnati multipurpose machines, fiber winding systems and multi-spindle contour milling machines. According to the company, which operates 650 contour milling machines around the world, any jet aircraft used in civil aviation has been manufactured using Cincinatti contour milling technology in one way or another.
The center of the highest activity.
Fives Cincinnati XT 5-spindle copy milling machine working area
The latest generation of Cincinnati XTi machines with the option of three- or five-spindle layout with a movable gantry is impressive in many ways. They have been designed for businesses that process different types materials. Thus, 7000 rpm spindles can cut aluminum and steel, while high torque spindles (2523 Nm) can cut titanium and other cemented carbides. What's more, the company markets the XTi as “the only multi-spindle roughing platform for titanium,” and claims that their metal removal rate of 100 cubic inches per minute is a record in the industry.
Kennametal Inc. KM4X100 spindle couplings can now be selected for XTi with 4,267mm travel (incremental 3,658mm) in the X-axis, 3,683mm in the Y-axis and 711mm in the Z-axis.
The hardness of titanium when contouring or milling with smaller or larger pitches constantly creates difficulties in terms of metal removal. Increased efficiency in carbide machining assumes maximum metal removal rates despite significant efforts and low speed cutting.
Connection to remove.
The KM4X100 spindle connection plays an important role in achieving maximum speed metal removal
Fives Cincinnati, like other machine builders, has responded to this challenge by increasing machine rigidity and damping performance. These improvements have minimized vibration, which negatively impacts part quality, product output and tool life, while increasing productivity. However, the tool-spindle connection is still a structural element that requires greater reliability and durability.
The amount of material removed during a particular operation is determined by the reliability of the connection between the machine and the cutting tool, which must withstand high loads, while remaining strong enough even in the event of strong tool bending or vibrations.
More stable metal removal rate (MRR).
By combining a high clamping force and an optimal level of interference, the KM4X provides a strong spindle connection with high rigidity and maximum bending load resistance. This improves the reliability and productivity of the machine when machining carbide and other materials.
The spindles are capable of transmitting a certain moment of rotation, while the cutting forces also create bending moments that exceed the specified limits for the connection even before the maximum torque is reached. This is seen in face milling where the overhang is usually greater and the bending resistance of the spindle joint is the limiting factor. For example, an 80 mm helical cutter with interchangeable cutting inserts extending 250 mm beyond the spindle end produces a bending moment of 4620 Nm and a torque of up to 900 Nm when machining Ti6Al4V at a speed of 360 cm 3 / min, a cutting width of 12.7 mm and a cutting depth of 63.5 mm.
By combining a high clamping force with an optimal level of interference, the new generation of KM4X spindle connections from the company provides reliability, extremely high rigidity and significant resistance to bending forces. In the case of titanium machining tools, this means a significant increase in machine productivity when machining carbide, the ability to develop incredibly high metal removal rates and get more finished parts per shift.
Fives Cincinnati Analytical Engineer Robert Snodgrass teamed up with Kennametal General Account Manager Mike Malott to study the performance of the KM4X about 4 years ago. “The engineering concept impressed me,” Snodgrass recalls. “She made it clear to us that the possibilities for machine tool design are endless: the increased spindle rigidity allows us not only to meet customer requirements for a more efficient cutting process, but also to increase the volume of production.”
Contouring progress.
Titanium contouring process
Kennametal VP Mark Huston explains: “Remember that typical aircraft structures are made from forgings, removing a significant amount of material to produce finished parts with the required parameters. Material utilization ratio - the ratio of the weight of purchased raw materials to the weight of the finished part - can be 4: 1, 8: 1 and even more, depending on the part. "
Due to their design and the limitations of the spindle connection, the first generation of Cincinnati contour milling machines provided metal removal rates of up to 4 cubic inches per minute when machining titanium parts. The new generation of Cincinnati XT machines, combined with the HSK 125 spindle end connection, has increased this speed to 50 inches, and with the introduction of the KM4X100, it has been doubled to 100 cubic inches per minute.
“Even at 100 cubic inches per minute, the XT benchmark test results using the KM4X were much lower than the theoretical bending moment limits,” added Snodgrass. Noting that previous generation testing had used CAT60 taper tool holders, he compared using the 50-taper version to "driving a tank and an SUV." The KM4X connection helped achieve twice the metal removal rate of a 60-taper tool holder. Compared to the CAT50, HSK100, or KM4X100, the CAT60 weighs almost twice as much.
Maximum torque, maximum power.
During the test run, the spindle connection is tested with the maximum torque and cutting forces. However, this is not a problem for the Fives Cincinnati XT contour milling machine with KM4X spindle connection.
Ken Wichman, Product Manager at Fives Cincinnati, commented, “This is a new dimension in spindle and machine tool design. Many gantry machines use a manual tool changer, even with an automatic changer / magazine. The increase in bending moment resistance in the KM4X allows the use of lighter tools than in the case of CAT or HSK with the same resistance limit. In terms of ergonomics, this is a huge advantage for the operator. For a customer opting for an automatic tool changer, the KM4X will allow more tools to fit into the available space. ”
Depending on the requirements for the final product, heat treatment is carried out using different 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; the final product is obtained by subsequent drying, firing or sintering of the granular or shaped material. In these cases, the regularities of heat and mass transfer are the same as when carrying out the main technological processes drying in 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, causing 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 various designs(chamber, tunnel, mine, with moving layers) with external and internal heating. On initial stage when the temperature rises, 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 humidity and temperature.
The gases escaping from 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.
One of the most effective ways cutting and processing of hard materials is waterjet cutting. It can be used to cut hard materials such as marble and granite, metal, concrete and glass. This view 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 for both metal and natural and artificial stone, 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 increases productivity.
The disadvantages include the high cost. consumable(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 under a pressure of up to 4000 bar;
Instrumental materials are those whose main purpose is to equip the working part of the instruments. These include tool carbon, alloy 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
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 used mainly 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, 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 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 - 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 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 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 CBNV 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. Basically, polycrystalline artificial diamonds are used for processing aluminum, copper and alloys based on them. Purpose of STM based on cubic boron nitride
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