With the rapid development of manufacturing technology, manufacturing technology as the basis of machining processes, cutting into the development of efficient development of new methods of cutting processing technology to provide complete sets of technology characteristics of new stage of development. At the same time, manufacturing technology, materials difficult to machine tool technology development to promote the development of tool technology toward high-state cutting, high-speed cutting, high-precision dry machining direction. Can achieve high efficiency, high stability, long-life applications are processed the growing popularity of super-hard cutting tools, automotive, aerospace, energy, military, mold plays an important role in the fields.
Machining, cutting tool material decision process efficiency, quality and processing costs of processing a key factor, the correct application of tool material selection is essential. The main modern high-speed steel tool materials, carbide ceramics, they are mainly hard phase composition of carbide, nitride oxide, together with adhesive material, the following tool hardness HV2000. For some modern refractory materials processing, the hardness can not meet the requirements of the superhard cutting tool materials have come into being. PCBN (polycrystalline cubic boron nitride) cutting tools, ceramic cutting tools, coated cutting tools will have great high hardness, chemical stability, wear resistance, can meet the high-speed cutting, dry machining, hard machining and other green manufacturing requirements. As the accuracy of PCBN cutting tools, cutting efficiency and tool life with unparalleled advantages and other aspects, therefore, PCBN tools to promote application can create huge economic benefits.
Paper mainly expounds the CBN cutting tool materials, physical properties and application of new developments and prospects in the 21st century development prospects of PCBN cutting tools.
CBN tool material manufacturing methods
Cubic boron nitride CBN (CubicBoronNitride) 20 Century 50's first by the U.S. General Electric (GE) companies use artificial methods of synthesis of high temperature and pressure conditions, the hardness of HV8000, second only to diamond (HV10000) and much higher than other materials, It is referred to as super-hard materials and diamond.
CBN crystals with the diamond crystals are sphalerite type, and the lattice constant close to the same type of chemical bond, so close to diamond hardness with compressive strength of CBN, but also because it is by the N, B atoms, it has a higher thermal stability than diamond chemical inert.
CBN tool material manufacturing methods primarily hot pressing method, the suppression of CBN crystal powder raw material - hexagonal boron nitride powder (HBN) placed pyrophyllite cavity, combined with catalysts, with a top six side top or sides of hydraulic press, 1600 ?, 5 ~ 6GPa CBN crystal formed under the hot pink 10min. Single crystal powder can be used for abrasive, abrasive. CBN crystal powder with a binder with catalysts, 1800 ?, 5 ~ 6GPa 3min will be under further pressure the whole blade or PCBN composite blade (carbide bottom, there are about 0.5mm thin CBN).
PCBN tool material properties
(1) has high hardness and wear resistance.
CBN crystal microhardness HV8000 ~ HV9000, the second highest known hardness of material. Different amounts of binder PCBN tool material hardness HV4000 ~ 6000 between the cemented carbide tool material hardness only HV1100 ~ 1800; Al2O3 ceramic tool material hardness of HV2000. Thus, for the processing of high hardness materials PCBN cutting tools have a higher wear resistance than cemented carbide and ceramics, can reduce the size of a large part machining error or the size dispersion, reducing tool change time of transfer Knife, to get performance full play.
(2) has high thermal stability, high temperature hardness.
CBN heat resistance up to 1400 ~ 1500 ?, 800 ? when the hardness of the hardness at room temperature Al2O3/TiC ceramic composite. Cutting temperature is higher, will be processed material softening, and the hardness difference between the increase of tool is beneficial to machining, but have little effect on tool life.
(3) has good thermal conductivity.
CBN thermal conductivity rate of 1300W / (m? K), 3.5 times the Purple Gang. The carbide thermal conductivity was only 35 ~ 75W / (m? K). CBN thermal conductivity than diamond, but much higher than the carbide, and, PCBN cutting tool thermal conductivity with the temperature increase is increasing, and therefore can quickly spread the heat tip Department will help to improve workpiece machining accuracy.
(4) has a high Young's modulus.
PCBN Young's modulus is about 750GPa, higher than the WC, TiC, Al2O3 and other materials.
(5) has a small thermal expansion.
PCBN thermal expansion coefficient of about (2.1 ~ 2.3) × 10-6 / K, the carbide thermal expansion coefficient (5 ~ 7) × 10-6 / K.
(6) has a smaller density.
PCBN density 3.48g/cm3, and Al2O3, Si3N4 density similar.
(7) has a low fracture toughness.
PCBN fracture toughness is about (3.5 ~ 5) Pa? M0.5, only half of ceramic tool materials. This is the only shortcomings PCBN.
(8) has good chemical stability.
CBN has a high antioxidant capacity, the atmosphere, 1000 ? when not produce oxidation, PCBN1300 ~ 1500 ? not decomposition; acid from erosion; on the iron group materials were inert, 1200 ~ 1300 ? was no chemical reaction. However, about 1000 ? and the water will produce hydrolysis, resulting in a large number of CBN wear, so when using PCBN tools dry cutting method should be adopted.
(9) has a low coefficient of friction.
CBN with different friction coefficient between 0.1 and 0.3, below the carbide friction coefficient (0.4 ~ 0.6), friction velocity and friction coefficient with increasing pressure is slightly reduced. Cutting difficult to form layers or stranded BUE will help improve the quality of surface processing. I am a professional editor from China Product, and my work is to promote a free online trade platform. http://www.himfr.com/ contain a great deal of information about oil filled radiator , electric fireplace manufacturers welcome to visit!
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