Boron Ultrahard Material
China cubic boron nitride full industry manufacturer
Hardened steel is a typical wear-resistant and difficult-to-machine material. After quenching or low-temperature tempering to relieve stress, the hardness of this material is as high as HRC45~HRC65, and it has high mechanical strength and fatigue wear resistance. Therefore, hardened steel is widely used in Various occasions that require high hardness and wear resistance, such as gears, bearings, etc. When cutting hardened steel, PCBN tools usually use dry cutting, and their working temperature can usually reach more than 1000 ° C. At such a high temperature, the thermal conductivity of carbide, ceramic tools and even diamond tools increases, and their performance will be reduced. The sharp drop affects the smooth progress of cutting. Usually when the cutting temperature is high, especially when cutting hardened materials, the high temperature can soften the hard surface layer and make the cutting go smoothly. At this time, the PCBN tool needs to show its thermal stability and excellent performance at high temperature to meet the cutting conditions. requirements.
1. Advantages of PCBN tools for machining hardened steel
1.1 At the temperature of cutting hardened steel (800 ~ 1000 ℃), the hardness and wear resistance of PCD, ceramic and cemented carbide tools are greatly reduced, and the durability of PCBN tools is relatively low. Still able to maintain high performance, the best of all cutting tools.
1.2 PCBN tool will not produce oxidation phenomenon under the high temperature generated by cutting. When cutting iron group metals, due to its high chemical inertness, it is not easy to chemically react with it, and it has high stability. Therefore, when cutting hardened steel, it has high stability. The chemical wear is relatively small, resulting in very high wear resistance.
2. Wear characteristics of hardened steel processed by PCBN tools
When the PCBN tool cuts hardened steel, there are many types of wear. Among them, the rake face wears, that is, the range of crater wear is small, which is due to the small depth of cut and the brittleness of the material; and the flank face. The wear is similar to that of carbide cutting, except that the wear rate of PCBN tools is much slower than that of carbide tools. PCBN tool wear will lead to reduced tool durability and frequent tool changes, which will also lead to reduced dimensional accuracy and surface roughness of the workpiece to be machined. The main reason for PCBN tool wear is the chemical wear of CBN particles during processing, and the wear resistance of the binder in the cutting process is better than that of CBN particles.
2.1 The cutting force is large. Because the hardness of the PCBN tool and the hardened material is very high, and the edge of the PCBN tool usually has a negative chamfer or edge grinding structure, which enhances the strength of the edge and avoids the premature cutting edge. Wear and failure, but also cause a significant increase in cutting forces during cutting.
2.2 High cutting temperature PCBN tool cutting hardened steel is usually carried out under dry cutting conditions. The collision and friction of two high-hardness materials will generate very high cutting temperature and heat, which will affect the dimensional accuracy and surface roughness of the workpiece. It will also cause the wear of the PCBN tool, so that the durability is reduced.
2.3 Sawtooth chip shape When the PCBN tool cuts hardened steel, the hardness is very high, and the machining allowance is small, and the metal material removed by cutting is thin, so the sawtooth chip is usually generated during the cutting process. In the process of its formation, it is often accompanied by periodically changing cutting force and high cutting temperature.
3. Conclusion
PCBN tool overall cubic boron nitride (PCBN) tool has excellent performance, high hardness, wear resistance, and shows red hardness and thermochemical stability at high cutting temperatures. It is more suitable for high-speed and dry cutting and "grinding by turning ” and other advanced processing methods. At the same time, it has better processing flexibility when cutting hardened steel, and its surface quality can also be obtained or even surpassed by traditional grinding.
