Abstract The choice of tool material depends on the cutting conditions and on which surface will be reground. For example, if the rake face of the tool is reground, it is more advantageous to use high speed steel with drills because the steel is more resistant to crater wear after the tool has no coating on the rake face. Progress in tool materials, out...
The choice of tool material depends on the cutting conditions and on which face will be reground. For example, if the rake face of the tool is reground, it is more advantageous to use high speed steel with drills because the steel is more resistant to crater wear after the tool has no coating on the rake face. The advancement of tool materials has led to the use of high-speed steel, hard alloy, various toughened ceramics, milled-base cermets, poly-diamonds and c-BN, which greatly improved the machining efficiency of metal cutting. Knives of each material have their own advantages and disadvantages and are therefore of particular use. Tool life and film thickness also have a certain relationship. If the blade surface wear is used as the reference, the tool life will increase with the increase of the film thickness, but the saturation will be achieved when the film thickness is 5μm, that is, the life is no longer significantly increased; but if the previous guilloche depth is the reference of the tool life, the tool life In proportion to the film thickness, no saturation phenomenon was observed. When the film layer is too thick, it is easy to cause peeling, and now the coating thickness of the turning tool is usually 5 μm - 10 μm.
Coated tools place new demands on tool geometry. It is generally believed that improvements in tool geometry, such as the rake angle, chip evacuation space, etc., should focus on the chip removal capability to accommodate increased cuts at higher feed rates and higher speeds. The coated knife has a high processing efficiency, which allows for a higher feed rate and cutting speed (which can be increased to 2-3 times the original cutting speed). For difficult-to-machine materials, the coating improves tool performance.
For hard coatings of milling cutters, the effect of film thickness is different. When milling a steel workpiece, the tool life is the longest when the film thickness is about 2 μm, and the life is decreased when the film thickness is increased. However, when machining cast iron or the like having a small impact, the optimum film thickness changes in a thicker direction. TiC coatings have the best results in milling, while Al2O3 coatings do not show the advantages of turning.
Carbide tools are usually coated by CVD, but PVD coating treatment hardly causes the edge strength to drop. PVD coated carbide milling cutters are more durable than CVD coatings. For the wear resistance of general high speed steel tools, CVD coatings are superior to PVD coatings, but precision, complex shapes, expensive, and non-reground high speed steel tools are mostly PVD coatings.
It is a rather complicated technique to improve the use of coated tools and to make full use of the hard coating. In order to achieve an optimized combination, a database of coated tools is created, and different workpieces are selected by computer to select tool coating materials and processing parameters. The situation becomes simple and effective, thus achieving high-quality, high-efficiency, low-cost processing targets.
The hard film on the surface of the tool has the following requirements on the material: 1 high hardness and good wear resistance; 2 stable chemical properties, no chemical reaction with the workpiece material; 3 heat and oxidation resistance, low friction coefficient, and strong adhesion to the substrate. It is difficult for a single coating material to fully meet the above technical requirements. The development of coating materials has been developed from the initial single Tin Coating, TiC coating, TiC-Al2O3-TiN composite coating and multi-composite coatings such as TiCN and TiAlN. Now the latest development of TiN/NbN, TiN/CN, and other multi-component composite film materials have greatly improved the performance of tool coatings.
Among the hard coating materials, TiN is the most mature and widely used process. At present, the use rate of TiN coated high speed steel tools in industrialized countries has accounted for 50%-70% of high speed steel tools, and the use rate of some non-reground complex tools has exceeded 90%. Due to the high technical requirements of modern metal cutting tools, TiN coatings are increasingly unsuitable. The TiN coating has poor oxidation resistance. When the temperature is up to 500 ° C, the film is obviously oxidized and ablated, and its hardness can not meet the needs. TiC has a high microhardness, so the wear resistance of the material is good. At the same time, it adheres firmly to the substrate. When preparing a multi-layer wear-resistant coating, TiC is often used as the underlying film in contact with the substrate, which is a very common coating material in coating tools.
The development of TiCN and TiAlN has brought the performance of coated tools to a higher level. TiCN can reduce the internal stress of the coating, improve the toughness of the coating, increase the thickness of the coating, prevent the crack from spreading, and reduce the chipping of the tool. Setting TiCN as the primary wear layer of the coated tool significantly increases tool life. TiAlN has good chemical stability and anti-oxidation wear. When processing high-alloy steel, stainless steel, alloy, and nickel alloy, it has a life expectancy of 3-4 times that of TiN coated tools. If there is a high Al concentration in the TiAlN coating, a very thin non-state Al2O3 is formed on the surface of the coating during cutting to form a hard inert protective film, which can be used more effectively. High-speed machining. The oxygen-doped titanium-titanium carbide TiCNO has high microhardness and chemical stability and can produce a coating equivalent to TiC+Al2O3 composite coating. Some transition metal nitrides, carbides, borides and their multi-component compounds, some of which have a relatively high hardness, can be developed for coating tools, which will make a new breakthrough in the performance of coated tools. .
Among the above hard film materials, there are three types in which the microhardness HV can exceed 50 GPa: a diamond film, a cubic boron nitride CBN, and a carbon nitride β-C3N4. The emergence of these few ultra-high hardness film materials has opened up a very rare and expensive natural diamond for the development of hard films for coated tools, which is far from meeting the needs of modern industry. In the mid-1950s, General Motors of the United States artificially synthesized diamond to obtain granular and powdered diamond. Due to the difficulty in processing granular diamond, it is difficult to apply it to the surface of the tool. The polycrystalline diamond inserts (PCD) commonly used in the mechanical industry also limit their performance due to their single geometry, no chipbreaks and reasonable geometric parameters. In the early 1970s, diamond film was synthesized by low-pressure chemical vapor deposition. After more than 20 years of technical research, the technology of low-pressure gas phase synthesis of diamond finally made a major breakthrough. Research on diamond has become a hot topic in the world.
Diamond and graphite are allotropes, diamond bodies are cubic, belonging to the Fd3m space group; and graphite is a hexagonal line, belonging to the R3m space group. Due to the different bonding modes between atoms, the performance difference is very large. From the theory of thermodynamics, graphite is more stable than diamond. Low-pressure vapor-grown diamond, in the phase diagram of carbon, is carried out in a region where graphite is steady state and diamond is metastable. However, since the chemical potentials of the two phases are very close, both phases can be formed. The key technology for low pressure gas phase synthesis of diamond is to inhibit the graphite phase and promote the growth of the diamond phase. Commonly used synthetic methods include hot wire method, plasma enhanced chemical vapor deposition (PECVD), including microwave PCVD, electron cyclotron resonance ECR-PCVD, DC and RF PCVD, DC and high frequency arc discharge thermal plasma. The energy input during the reaction (such as RF power, microwave power, etc.), the activation state and optimal ratio of the reaction gas, and the nucleation mode of the deposition process are decisive for the formation of the diamond film. The crystal form and lattice constant of the substrate material have a great influence on the nucleation growth of the diamond film. When the diamond phase and the graphite phase simultaneously nucleate on the substrate, the graphite phase will grow rapidly. If a high concentration of hydrogen is present, it will corrode the grown graphite phase and remove the graphite phase. Although it can also corrode the diamond phase, it is much slower, thus inhibiting the growth of the graphite phase. purpose. Many deposited diamond films require temperatures from 600 ° C to 900 ° C, so this technique is commonly used to deposit diamond films on the surface of cemented carbide tools.
The commercialization of diamond carbide tools is a major achievement in coating technology in recent years. Compared with synthetic diamond film, the research work of synthetic CBN film is carried out later. BN has three isomers: 1CBN cubic strain sphalerite structure, F43m space group; 2h-BN hexagonal line graphite structure, P6/mmc space group; 3w-BN hexagonal line wurtz structure, P63mc space group. The properties of the three isomers vary widely, and h-BN has a structure very similar to graphite and has a very soft texture. In w-BN and CBN, B and N atoms are all formed into a tetracoordinate structure, which are all superhard materials. The CBN obtained by the high temperature and high pressure method is granular crystal, the highest microhardness is up to 84.3 GPa, and the highest microhardness of the CBN film is 61.8 GPa, which is no less than the diamond film. CBN is second only to diamond in terms of hardness and thermal conductivity, and has excellent thermal stability. It does not oxidize when heated to 1000 ° C in the atmosphere. CBN has extremely stable chemical properties for iron group metals. Unlike diamond, which is not suitable for processing steel, it can be widely used in the finishing and grinding of steel products. In addition to excellent wear resistance, CBN coating can process heat-resistant steel, titanium alloy and hardened steel at a relatively high cutting speed. It can cut high-hardness chill rolls, carbon-doped materials and tool wear. Very severe Si-Al alloys, etc. The methods for synthesizing CBN thin films by low pressure gas phase mainly include CVD and PVD methods. CVD includes chemical transport PCVD, hot wire assisted heating PCVD, ECR-CVD, etc.; PVD has reactive ion beam plating, active reactive evaporation, laser evaporation ion beam assisted deposition, and the like.
CBN synthesis technology has a lot of work to do in basic research and application technology, including reaction mechanism and film formation process, plasma diagnosis and mass spectrometry, determination of optimal process conditions, and development of high-efficiency equipment.
The reason why the tool with super hard coating has a small amount of wear is due to the high hardness, high melting point and excellent thermochemical stability of the superhard compound of the film layer. Superhard compounds are mostly composed of transition metal nitrides, carbides and borides. They are combined with strong covalent bonds and have a low standard free energy of formation, which constitutes a very stable system and does not significantly reduce hardness at high temperatures. These layers exhibit higher resistance to mechanical wear and thermal wear than tool materials such as cemented carbide and high speed steel.
Coating conditions, process parameters, pre-plating substrate pretreatment, etc. are very important for the preparation of high quality coatings. The state of the tool surface is critical to the adhesion of the coating. The surface of the workpiece to be plated must be free of other layers, burns, rust, oil or other contaminants. The workpiece is subjected to strict sand blasting and degreasing cleaning, and ion bombardment cleaning is performed before the hard film is grown in a vacuum.
The tool used for different coating materials has different effects. Low-speed cutting, TiC coating has an advantage; high-speed cutting, TiN is more suitable; HfN has higher thermochemical stability than TiN, suitable for working at higher cutting speeds. Compared to TiN and A1203 coatings, A1203 coatings have a significant advantage in high-speed cutting, while TiN-coated tools have a longer service life at low-speed cutting.
Compared with uncoated tools, coated tools have significant advantages: they can improve machining efficiency, improve machining accuracy, and extend tool life, thus ensuring the quality of workpieces and reducing processing costs. Modern metal cutting, the requirements of the tool are high cutting speed, high feed rate, high reliability, long life, high precision and good cutting control. The emergence of coated tools has made a major breakthrough in cutting performance. It combines the tool base with the hard film surface. Due to the good toughness and high strength of the substrate, the hard film surface has high wear resistance. And a low coefficient of friction, which greatly improves the performance of the tool.
Lamination of various choices: plain gold, plain white, transparent, black, laser effect, colorful. Tinplate with lamination on single face or both faces. Laminated Tinplate is with stable chemical and physical performance. Laminated tinplate is with lower cost, if compared with lacquering or printing.
1. Technical standard: BS EN 10202, DIN EN 10203, GB/T2520 , JIS G3303
2. Steel type: MR, SPCC3. Thickness: 0.115 - 0.50 mm
4. Width: 600 - 1050 mm
5. Length: 600-1200mm
Tin coating: ordinary 2.8 or 2.8g and 5.6g or 5.6g, we can produce according to customer's requests.
Laminated Tinplate
Laminated Tinplate,Laminated Tin Free Steel Tinplate,Etp Tinplate Laminated,Tin Coating Tin Plate
Jiangsu Guolian New Material Co., Ltd. , https://www.cntinplate.com