Development and Prospects of PCBN Tools in the 21st Century (3)

PCBN tool classification and its influencing factors

PCBN tool materials, like other types of tool materials, have many grades depending on the composition and are suitable for different purposes. The performance of PCBN is related to the content of CBN, the particle size and the type of binder. By adjusting the CBN content, grain size and binder ratio and type, PCBN tools with different properties and different processing requirements can be obtained.

(1) PCBN cutters can be roughly divided into two categories according to the added components: one is directly sintered by CBN single crystal, with a large CBN content (more than 70%), high hardness, suitable for heat-resistant alloys, cast iron and The cutting process of iron-based sintered metal; the other is a hot-pressed body in which a certain proportion of ceramic binder (mainly TiN, TiC, TiCN, AlN, Al2O3, etc.) is sintered by using CBN grains as the main body. PCBN has a low CBN content (less than 70%) and a low hardness, which is suitable for the cutting of hardened steel.

(2) The bonding agent of PCBN mainly has three types: metal bonding agent, which is composed of metal or alloy, such as Co, Ni, etc. The toughness and conductivity of the metal bond PCBN sintered body are good, and the disadvantage is that the bonding agent softens and resists at high temperature. The grinding performance is degraded; the ceramic bond, such as A1203, etc., the ceramic bond PCBN sintered body has high high temperature wear resistance and strong anti-adhesive ability, which solves the problem of high temperature softening of the metal bond, but its impact resistance Poor and brittle; cermet binders such as TiN, TiC, TiCN, AlN, etc., solve the above problems and have better comprehensive performance.

(3) PCBN tools can be divided into: composite PCBN hot press block and PCBN composite sheet with cemented carbide composite hot pressing. The overall PCBN insert is rigid and suitable for roughing; the composite PCBN insert is less expensive and suitable for finishing or semi-finishing.

(4) The existing research shows that the tool prepared by using pure CBN material can not obtain the best processing effect in many cases, and the content of CBN is generally between 50% and 95%. The CBN content mainly affects the hardness and thermal conductivity of PCBN. With the increase of CBN content, the hardness, wear resistance and thermal conductivity of PCBN increase, and the toughness decreases. When the content of CBN is less than 50%, the hardness of PCBN decreases. Causes the cutting edge to plastically deform and break the blade. When the CBN content exceeds 95%, the performance of the PCBN deteriorates, the brittleness increases, the CBN crystal grains are easily detached, and the wear resistance is greatly reduced.

PCBN tool application

1 PCBN is the best tool material for hard cutting technology

(1) Tools made of super-hard materials have high hardness, high Young's modulus, high thermal conductivity, low friction and low thermal expansion, and can cut a variety of hard materials and difficult materials. The red hardness and wear resistance of PCBN tools have great advantages in hard dry-cutting difficult-to-machine materials. PCBN tools are commonly used to machine materials with hardnesses higher than HRC50. They have high hardness at cutting temperatures up to 1500 °C and are ideal for cutting hardened steels, chilled cast irons and other high-hard ferrous metals.

(2) Finishing of quenching hardware (hardness higher than HRC55) is usually done by grinding. However, with the development of tool materials and the improvement of machining precision of CNC machine tools, hard cutting is used instead of grinding to complete parts. Final processing has become a new finishing route.

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