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The metal cutting tool materials used today can be divided into nine types, including high-speed steels with the lowest cutting speed and worst wear resistance, and polycrystalline diamond tools with the best high-speed performance. High-speed cutting also requires a tool material with good toughness, high impact resistance and good wear resistance.
In general, low-performance tools, such as high-speed steel and non-coated cemented carbide, have a wide range of applications in general machining, but high-speed performance is not good. While high-performance tools, such as polycrystalline diamond tools, are the hardest among all tool materials, they have very high wear resistance and speed capability. Cutting heat has little effect on it, and high-speed machining of non-ferrous metals and non-metal materials. It fully demonstrated its superiority. However, its impact resistance is poor, and its thermal properties when cutting steel and cast iron materials are poor. Because high-speed cutting of ferrous metals, the carbon atoms in the tool material will diffuse to the workpiece, causing increased wear of the tool.
Carbide cutting tools have the largest number of applications, accounting for 80% of all tool sales. 90% of ordinary speed metal cutting uses carbide tools. Carbide has better impact toughness, but high speed performance is not good. In addition, high-speed cutting tools also have extremely high thermal and chemical stability, and hard alloys cannot meet this requirement.
CBN tools are extremely heat-resistant and can cut hard materials at high temperatures, but are expensive and cannot process soft metal materials. The aluminum-based ceramic material with good chemical stability is just suitable for this kind of processing, but it lacks thermo-hardness and cannot be used for high-speed processing.
Concentrating the advantages of different characteristics of tool materials, developing new tool materials, so that it has both impact toughness and high wear resistance, is one of the major issues to be solved in the research of high-speed cutting tools. On tool base materials with relatively good impact toughness, surface coating with a material with good thermal and wear resistance results in new tools, often with the advantages of two materials, such tools in high-speed cutting Has a great scope of application.
Under the guidance of this idea, new composite cutting tools such as hard alloy coated cutters, CBN coated cutters, and PCD coated cutters have emerged, which are suitable for high-speed cutting of different metal materials.
Suitable for high-speed cutting of coated carbide tools, due to the use of heat-resistant, high hardness coating materials and multi-layer coating technology, the coated carbide cutting tools have a large cutting range, long life, and cutting. Performance is much better than uncoated carbide. Therefore, coated cemented carbides have a great tendency to replace ordinary uncoated cemented carbides.
The tool coating technology can be used not only on the hard alloy tool, but also on other tool materials, such as cermets and ceramics.
Ceramic cutting tools can also be used for high-speed cutting tools. It is an important part of the research and development of cutting tool materials in recent years. Whisker-reinforced ceramic tool is a special material tool, because it has a good impact toughness, thermal shock resistance characteristics, it is suitable for high-speed processing.
Another problem that high-speed cutting tools have to solve is to grind or push out certain geometry chip breakers on the insert to achieve chip breaking and control the chip direction, which is also an important technique for improving the machining efficiency and improving the tool durability.
High-speed cutting tools should have excellent impact toughness and thermal shock resistance, better heat resistance, abrasion resistance, and chemical stability, as well as better chip breaking effects, and be adapted to a wider range of metal cutting.
From the study of high-speed cutting mechanism, we can see that with the increase of cutting speed, the metal removal rate is greatly improved, and the material has a high strain rate (about 1.67×105 /s at the cutting speed of 500m/min, cutting temperature). Achieving 1400°C) The various phenomena that occur at the chip forming process and at the contact surface between the tool and the workpiece are different from those in the conventional cutting conditions. Tool hardness and tool wear issues have become critical. In order to achieve high-speed cutting, tool materials and tool manufacturing techniques suitable for high-speed cutting must be supported.
October 30, 2023