However, ceramics have poor impact toughness, so the requirements for high-speed cutting are high, that is, the material to be processed is required to be uniform, and the direction, angle and speed of the tool approaching the workpiece are very strict. Ceramic and cermet tool materials replace hard alloys in the finishing and semi-finishing of steel and cast iron, improving processing efficiency and product quality. High speed cutting technology
High-speed cutting technology is characterized by high efficiency, high precision and high surface quality. It has been widely used in the automotive industry, aerospace, mold manufacturing and other industries, and is an important part of contemporary advanced manufacturing technology. The characteristics of high-speed cutting technology are mainly reflected in the following aspects:
1 The cutting speed is very high, usually 5 to 10 times that of ordinary cutting. 2 The spindle speed of the machine tool is very high, generally above 10 000 ~ 20 000r / min. 3 The feed rate is very high, usually 15 ~ 50m / min, up to 90m / min. 4 For different cutting materials and tool materials used, the meaning of high-speed cutting is not the same. 5 During the cutting process, the cutting edge passes at a frequency close to the dominant natural frequency of the “Machine-Tool-Work†system.
Compared with traditional machining, high-speed cutting significantly increases the cutting speed, resulting in increased friction between the workpiece and the rake face, and leads to an increase in the temperature of the chip and tool contact surface, which can reach the melting point of the workpiece material, making the workpiece soft or even Liquefaction, thus greatly reducing the resistance to cutting tools, making cutting become lighter. At the same time, 70% ~ 80% of the heat generated by the processing is concentrated on the chips, and the removal speed of the chips is fast, the heat transferred to the workpiece is greatly reduced, and the processing precision is improved. High-speed machining is an indispensable technology that greatly increases the machining efficiency without increasing the number of equipment. The advantages are: improving production efficiency; improving machining accuracy and surface quality; and reducing cutting resistance.
In order to achieve high-speed machining, high-flexible high-speed CNC machine tools and machining centers are generally used, and some special high-speed milling and drilling machines are used.
The machine tool also has a high-speed spindle system and high-speed feed system, high spindle stiffness characteristics, high-precision positioning function and high-precision interpolation function, especially the arc high-precision interpolation function. High-speed machine tools and high-speed tools are the premise and basic conditions for high-speed cutting. There are strict requirements for high-speed machine tool performance and tool material selection in high-speed machining.
High-speed cutting requires high-speed cutting. High-speed machining places special requirements on tool materials. In addition to the required hardness and wear resistance, strength and toughness, heat resistance, processability and economy, it should also be high. Reliability, high heat resistance and thermal shock resistance as well as good high temperature mechanical properties. At present, tool materials commonly used for high-speed cutting include titanium-based cemented carbide, ceramics, polycrystalline cubic boron nitride, coated tools, and diamonds.
(1) The properties of cemented carbide tool materials are all improved. The hardness of titanium-based cemented carbide tools is above 2000HV. Compared with WC cemented carbide, the strength, hardness, toughness and chipping resistance are significantly improved. And the ability to resist bonding is also significantly enhanced. Moreover, the performance of cemented carbide is continuously improved and the application surface is expanding. The first is the development of fine-grained, ultrafine-grained hard alloy materials, which have significantly improved strength and toughness. It is used to manufacture solid carbide tools such as small and medium-sized drills, end mills, taps, etc. The tool replaces the Chinese metalworking online. The traditional high-speed steel tool is used to bring the universal tool into the field of high-speed cutting. Secondly, the development and use of new processes such as cemented carbide pressure sintering improve the intrinsic quality of cemented carbide. In the case of the base material of the chemically coated cemented carbide insert grade, a graded cemented carbide with good resistance to plastic deformation and a tough surface was developed, which improved the cutting performance and application range of the coated cemented carbide insert.
(2) Coatings are the key technology to improve tool performance. Coating technology of cutting tools plays an important role in the development of modern cutting and cutting tools. The coating technology can achieve very good comprehensive mechanical properties of the cutting tool, not only effectively improve the service life of the tool, but also greatly improve the cutting efficiency of the Chinese metal processing online, so the coated tool becomes a high-speed cutting technology. The fastest-growing tool has a ratio of more than 50% in the tool. The coating tool is mainly used in drills, reamers, taps, hobs, inserts and carbide inserts.
Chemical coating (CVD) is the main coating process for indexable inserts. By chemical vapor deposition and vacuum sputtering, a layer of TiC or Al2O3 with a thickness of 5 ~ 12μm is sprayed on the surface of the cemented carbide tool. Improve the hardness of the tool surface and improve wear resistance and lubricity.
Among them, the hardness of Al2O3 coated tool is up to 300HV, which has higher high temperature hardness and stability. The two-layer and three-layer composite coatings such as TiC-TiN and TiC-TiN-Al2O3 have better cutting performance. CVD diamond coatings have also made progress, reducing the surface roughness of coatings, and entering the practical stage of China Metalworking Online. At present, the coating ratio of foreign carbide indexable inserts has reached more than 70%.
The progress of physical coating (PVD) has attracted remarkable progress, and significant progress has been made in furnace structure, process, automatic control, etc., and not only heat-resistant coatings suitable for high-speed cutting, dry cutting, and hard cutting have been developed. , such as Super TiAlN, and TiAlCN, which has better comprehensive performance, all rights reserved coatings and DLC, W/C anti-friction coatings, and through the innovation of coating structure, nano-scale ultra-thin super multi-layer coating The development and application of new coating materials will be accelerated, and the hardness and toughness of the coating will be greatly improved. The coating will become the main way to improve the performance of the tool.
(3) The use of superhard tool materials ceramics, PCBN and diamond will significantly increase ceramic knives with alumina-based Al2O3 and silicon nitride-based Si3N4, with high hardness and wear resistance, heat resistance up to 1200 °C Above, the chemical stability is good, the affinity with metal is small, the cutting speed can be increased by 3 to 5 times, and the high hardness material of 65HRC can be processed.
However, ceramics have poor impact toughness, so the requirements for high-speed cutting are high, that is, the material to be processed is required to be uniform, and the direction, angle and speed of the tool approaching the workpiece are very strict. Ceramic and cermet tool materials replace hard alloys in the finishing and semi-finishing of steel and cast iron, improving processing efficiency and product quality.
Polycrystalline cubic boron nitride (PCBN) is a soft hexagonal boron nitride added under high temperature and high pressure. It has better chemical stability than diamond, hardness up to 8000 ~ 9000 HV, good wear resistance and heat resistance up to 1400. °C, which is chemically inert with iron, is suitable for processing materials with high hardness, and will become the main tool material for high-speed cutting of ferrous metals, difficult-to-machine materials, and dry cutting and hard cutting.
Most of the diamond used to produce cutting is synthetic diamond. There are three types of synthetic diamonds: polycrystalline diamond (PCD), chemical vapor deposited diamond (CVD), and high temperature synthetic single crystal diamond. PCD and single crystal diamond are the best tools for the efficient and precise processing of non-metallic materials such as non-ferrous metals, ceramics, glass and graphite.
Http://news.chinawj.com.cn Editor: (Hardware Business Network Information Center) http://news.chinawj.com.cn
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