Diamond tool is the ideal tool material for high-speed cutting (2500～5000m/min) aluminum alloy. However, due to the affinity of carbon to iron, especially at high temperature, diamond can react with iron, so it is not suitable for cutting. Iron and its alloy workpieces.
Cubic boron nitride
Cubic boron nitride (CBN) is a purely synthetic material. It is the second superhard material, CBN micropowder, synthesized in the late 1950s using a diamond-like method. Due to the poor sintering performance of CBN, it was not until the 1970s that a cubic boron nitride agglomerate (polycrystalline cubic boron nitride PCBN) was produced, which consisted of CBN fine powder and a small amount of binder phase (Co, Ni or TiC, TiN, Al2O3). ) Sintered under high temperature and high pressure. CBN is a dense phase of boron nitride, with high hardness (after diamond) and heat resistance (1300 ~ 1500 ° C), excellent chemical stability (far better than diamond) and thermal conductivity, low coefficient of friction . PCBN has a low affinity for Fe elements, so it is an ideal tool material for high-speed cutting of ferrous metals. The micro-grains in the PCBN structure are disorderly arranged, uniform in hardness, non-directional, consistent wear resistance and impact resistance, and overcome the disadvantages of CBN easy cleavage and anisotropy. The CBN content, grain size and bonding are equivalent to affect the performance of the PCBN. The CBN content is high, the hardness and thermal conductivity of PCBN are high, the CBN grain size is large, the damage resistance is weak, and the sharpness of the blade is poor. When the metal materials Co and Ni are used as the binder phase, PCBN has better toughness and conductivity. When the ceramic material is used as the binder phase, it has good thermal stability. At present, the PCBN layer of about 0.5mm is directly sintered or brazed on the cemented carbide substrate to form a PCBN composite sheet, which is advantageous for improving strength and solderability, and is convenient for manufacturing PCBN cutters.
There are roughly two types of PCBN blanks in terms of organization. One is a high content of PCBN (CBN, mass 80% to 90%), which is mainly composed of direct bonding between CBN grains, and has high hardness and high thermal conductivity. The other is PCBN with a low CBN content, which is firmly bonded with a small amount of metal or ceramic binder, and has good strength and toughness. Generally, the PCBN tool with lower CBN content (50%~65%) is suitable for finishing 45~65HRC hardened steel, high content (80%~90%) suitable for processing nickel-chromium cast iron, coarse and semi-coarse intermittent Cutting hardened steel, cutting cast iron at high speed, machining hard alloys, sintered metals and heavy alloys. A PCBN tool with a suitable CBN content can be used to process cast iron at a high speed of 500 to 1500 m/min, a hardened steel of 45 to 65 HRC at 100 to 400 m/min, and a heat resistant alloy at 100 to 200 m/min. However, it is not suitable to process steel and alloy steels, alloy cast irons and heat-resistant alloys with ferrite and below 45HRC, and it is not suitable for processing workpieces below 35HRC. Coated CBN tools are still under investigation.
ceramic knife
Ceramic tools are one of the most important tool materials for high speed cutting. At present, the proportion of ceramic inserts in the world accounts for about 3% to 5% of the indexable blades, 5% to 7% in Russia, 7% to 9% in Japan, and 9% to 12% in Germany. Britain, France, Sweden, etc. It is also vigorously promoting its application. Due to the great progress in the raw materials, components and preparation processes of modern ceramic tools, the sales growth of ceramic knives has reached 20% in the past five years. The ceramic tools that have been developed internationally are mainly two series of alumina-based (Al2O3) and silicon nitride-based (Si3N4), which are added with various oxides, nitrides, carbides and borides to form different varieties. Alumina based and silicon nitride based ceramic tools. There are more than 40 varieties and more than 200 grades, of which there are more than 25 kinds of alumina base and nearly 15 kinds of silicon nitride base.
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