CNC Machine CBN Hard Turning Inserts Super Hard Hardness Customized

CBN Inserts For Hard Turning

Handling of raw materials
Because there are impurities such as WBN, HBN, pyrophyllite, graphite, magnesium, iron, etc. remaining in the CBN micropowder; in addition, it and the binder powder both contain adsorbed oxygen, water vapor, etc., which are unfavorable for sintering. Therefore, the purification method of raw materials is one of the important links to ensure the performance of synthetic polycrystalline. During the development, we used the following methods to purify the CBN powder and binder materials: first, treat the CBN powder with NaOH at about 300 C to remove pyrophyllite and HBN; then boil perchloric acid to remove graphite; The plates were boiled to remove metals and washed with distilled water until neutral. Co, Ni, Al, etc. used for the binder are subjected to hydrogen reduction treatment. Then, the CBN and the binder are mixed uniformly according to a certain ratio and incorporated into the graphite mold, then sent to a vacuum furnace with a pressure less than 1E2, heated at 800-1000°C for 1 hour, and removed the dirt on the surface, adsorbed oxygen and water vapor, etc., so that the The surface of CBN grains is very clean.
In terms of the selection of binder materials and the addition amount, the total amount of binder added should be sufficient but not excessive. The experimental results show that the wear resistance and flexural strength of polycrystalline are closely related to the mean free path (the thickness of the binder phase layer). The dosage of the agent is 10% to 15% (mass ratio).
In addition to the selection of binder, the determination of CBN particle size and particle size ratio is also crucial. According to the requirements of machining accuracy and surface quality, the particle size of CBN used for manufacturing cutting tools is roughly divided into: coarse particle size 20-30 μm; medium particle size 3 ~10 microns; fine particle size 2 microns. Polycrystalline made of coarse grain is difficult to make into a tool with high precision requirements, but its wear resistance and impact resistance are high, and polycrystalline made of fine grain can meet the requirements of finishing and super finishing.

1.embryo body synthesis

The PCBN composite sheet is directly compounded with the CBN layer and the cemented carbide substrate under high temperature and high pressure, and is made into various welding forming cutting tools or blades through cutting and welding processes.
Integral PCBN sintered block is directly sintered without alloy matrix to become integral PCBN blade. After sharpening, cubic boron nitride integral polycrystalline blade is made. As shown in "PCBN composite sheet". Synthesis equipment Most of the synthetic equipment used abroad are two-sided top presses, and most of them are six-sided top presses in China.

2.Grinding process of PCBN tool

The produced PCBN tool blank needs to be sharpened for cutting, and the sharpened tool obtains the correct geometry and surface finish. Generally divided into rough grinding, fine grinding and grinding processes. 180-240 resin-bonded diamond grinding wheel is used for rough grinding, with a feed of 0.01 mm/double stroke; Wlo-W14 resin-bonded grinding wheel is used for fine grinding, with a feed of 0.005 mm/double stroke; for grinding For diamond grinding wheel or grinding paste of W5~W3, special attention should be paid to the influence of cutting edge dressing of diamond grinding wheel on grinding. Although the tool swings back and forth on the entire end face of the grinding wheel during the sharpening process to make the surface consumption of the grinding wheel uniform, in fact, the surface of the grinding wheel is still prone to unevenness, which must be frequently trimmed.

3.Geometric parameters of PCBN tools

The life of a PCBN tool is closely related to its geometric parameters, and a suitable front and rear angle can improve the impact resistance of the tool. Chip removal capacity and heat dissipation capacity. The size of the rake angle directly affects the force of the cutting edge and the internal stress state of the insert. In order to avoid the excessive tensile stress caused by the mechanical impact of the tool tip, a negative rake angle (-5.～-10.) is generally used. At the same time, in order to reduce the wear of the relief angle, the main and auxiliary relief angles are 6. , the corners are rounded with a nose radius of 0.4–1.2 mm, and the edges are ground smooth.

4.Inspection of PCBN tools

In addition to testing physical properties such as hardness index, bending resistance, tensile strength, etc., it is also necessary to use a high-power electron microscope to check the surface and edge processing accuracy of PCBN tools. Then it is dimensional inspection, precision inspection, M value, geometric tolerance, roughness, and then packaging and storage.