Cubic boron nitride (CBN) has high hardness, good thermal conductivity, and is not easy to react with iron materials, second only to diamond. Polycrystalline cubic boron nitride (PCBN) is made by sintering CBN particles with a ceramic binder. PCBN facilitates the process of hardened steel from grinding to cutting. Sumitomo Electric’s hard alloy PCBN cutting tools can significantly improve efficiency and save costs during the finishing and semi-finishing of iron materials such as cast iron. On the other hand, PCBN is used in the efficient and high-precision machining of cast iron because of its high strength and good thermal conductivity. For example, the surface finishing of engine blocks and oil pumps is usually performed using PCBN cutting tools. This article mainly discusses the method of milling cast iron with new PCBN tools.
There are two types of PCBN sintered body: one is the CBN particles bound to the binder. The other is to use a small amount of binder material to bind the CBN particles together. The former has good wear resistance and can be cut with hardened steel. Otherwise, the CBN content is high and the thermal conductivity is good, which can be used for cast iron processing, heat-resistant alloys, and PM components. BN7000 belongs to the latter.
Figure 1 shows the new PCBN grade BN7000 cutting tool. The CBN content of BN7000 is higher than other traditional PCBN cutting tools, with high strength, good toughness, high hardness, and good thermal conductivity. Figure 2 shows the microstructure and properties of BN7000. With a sintering pressure higher than the commonly used 5GPa, the CBN content increases from 90vol% to 93VOL%. In order to reduce the wear of the binder, the amount of binder in the BN7000 sintered body was reduced by 30%. During the sintering process, the CBN particle reaction is accelerated to improve the composition of the binder, thereby greatly improving the bonding strength of the binder. Larger than traditional adhesives.