Introduction of superhard material tools used in machining

Superhard material tools currently mainly include single crystal diamond tools, polycrystalline diamond (PCD) tools, chemical vapor deposition (CVD) diamond tools, and polycrystalline cubic boron nitride (PCBN) tools. It is not only the ideal tool for processing high-hardness materials, but also replaces ordinary cutters with super-hard material tools for cutting, which can realize high-speed and high-efficiency machining of cast and forged blanks and/or finish roughing and finishing in one time. Superhard material tools are perfectly suited for high speed, precision and automated machining. Especially in the case of car grinding, milling and grinding, it is suitable for precision grinding of forming, profiling and sizing, and the grinding quality is significantly improved, and the grinding efficiency is increased several times or even dozens of times. . It not only prevents defects such as surface burns, micro-cracks, gaps, and excessively deteriorated layers, but also improves work efficiency, reduces consumption and grinding costs. It has the advantages of high efficiency, low consumption, strong adaptability and short manufacturing cycle. At present, it has been widely used in the machining of automobiles, motorcycles, aviation, mining, electronics, glass and other industries.



1. Application in machining

1.1 Application in turning machining

1.1.1 Turning steel parts

When machining hardened steel, superhard material tools can be worn by car. Since the depth of cutting is ten times higher than grinding, the efficiency can be increased by more than 4 times, and the processing cost is reduced to 1/5.


The hardened steel with a PCBN tool with a hardness higher than 45HRC has the best effect, and the cutting speed is generally 80-120M/MIN. The cutting speed of high hardness workpieces should be low, such as workpieces with a hardness of 70HRC, and the cutting speed should be 60~80M/MIN. The cutting depth of the finished car is 0.1-0.3MM, the feed rate is 0.05-0.025MM/R, the surface roughness is RA0.3-0.6μM, and the dimensional accuracy is 0.013MM. If a rigid CNC lathe is used and the rigidity of the PCBN tool is good and the cutting edge is sharp, the surface roughness of the finished car can reach RA0.3μM and the dimensional accuracy is 0.01MM, which can reach the level of CNC grinding machine processing.


A factory originally used the grinding process to process pinion gears, which can only process 100 pieces in one class; now it uses PCBN tool turning, the cutting parameters are: V=60～120MM/MIN, F≤0.12MM/R, AP≤0.1MM, one The class can process 400 pinions. In addition, the processing costs allocated to each gear have also decreased.


For example, using the PCBN tool to process the carburized and quenched 20CRMNTI automotive gearbox synchronizer fork (HRC58~62), cutting speed V=150MM/MIN, feed? =0.1MM/R, AP=0.2~0.3MM, tool cutting stroke reaches 9.58KM. After the car is milled, the efficiency is increased by more than 4 times, and the processing cost is reduced to 1/3 to 1/2 of the original grinding process.


The Netherlands HEMBRUG company adopts PCBN tool finishing hardening EN21 bearing steel (HRC62) and American National Standard Process Research Y in MIKROTURNCNC series super-precision lathe. KEVINCHOU and CHRISJ. EVANS uses SUMITOMOBN series PCBN tools to process AISIM50 steel (HRC62~64) and UK DEBEERS industrial diamond company M. A. FLEMING uses the AMBORITEDBN45 tool to turn EN31 bearing steel on the DELTATURN40 lathe, all of which achieve nano-cutting.


Examples of ultra-hard material tool processing steel parts are the 20CRMNTIHA3 multi-speed spline cutting groove (HRC58-63) for processing two-axis in heavy-duty vehicle transmission using CK7820 CNC lathe of Great Wall Machine Tool Plant, and 45 machining machine for mining machinery using 1A616 machine tool. No. Φ48H6 drive shaft (HRC42～45), using the PCBN tool to accurately turn GCR15 hardened bearing steel workpieces (30HRC, 40HRC, 50HRC, 60HRC and 64HRC) on the CA6140 lathe with stepless speed change.


Use specially ground PCBN tools on ultra-precision lathes with a depth of cut of 15 to 20? M, the feed rate is 0.608? Under the condition of M/R rotation, the surface finish of the machined surface can reach RMAX=0.0254? M. Cutting stainless steel on a general precision CNC lathe, you can get RMAX=0.2? Surface roughness within M.


1.1.2 Turning cast iron parts

When processing hard cast iron, as long as the hardness reaches the medium hardness level (HRC45), the tool with super-hard material will achieve good processing results, which is very suitable for high-speed machining on high-volume production lines, and is widely used in the automotive industry.


The exhaust valve seat on the engine cylinder head is made of copper and molybdenum high chromium alloy cast iron (HRC44). The processing methods generally include milling and car. Most of them are on the automatic line, and processed together with the hinge hole of the hinge, V= 71.6M/MIN,? =26.5MM/MIN, AP=1.0MM, using PCBN overall blade processing, average durability is 1,200 valve seats, machining surface roughness RA0.4μM, cone surface swing ≤0.05MM, high tool life and stable quality .


In the automobile engine production line, the cylinder hole finishing of the gray cast iron cylinder requires high dimensional accuracy, small surface roughness and good stability of the cylinder bore; the cutting speed is high due to the fast processing cycle of the production line (usually V≥500M/MIN) The tool life is long (the number of machining holes is ≥1000), and the blade life of multiple stations such as chamfering, stop, and coarse boring should meet the durability requirements. High-speed cutting and high-stability machining of engine cylinder bore can be realized by PCBN tool; the typical cutting parameters are: V=500M/MIN, F=0.2～0.4MM/R, AP=0.2～0.7MM; machining surface roughness RA ≤ 1.6μM, tool life "1,000 pieces.


Boron-containing cast iron cylinder liner is processed by PCBN tool. Cutting parameters: V=200M/MIN, F=0.1MM/R, AP=0.2～1MM, machining surface roughness RA≤1.6μM, precision IT6, between two sharpening With a tool life of 100 pieces, it can achieve "car grinding". Due to the dry cutting, the environmental pollution of the cutting fluid and the grinding wheel dust is avoided, and the chips can be recycled and reused, which meets the requirements of clean production.


Cutting the gray cast iron brake disc with PCBN tool, the cutting speed is generally 700 ~ 2,000M / MIN, such as Shanghai General Motors Corporation using SECO tool company PCBN300 type blade, cutting speed can reach 2,000M / MIN.


1.1.3 Turning alloy workpieces

Using PCD tools to turn aluminum alloy wheels, the cutting speed can be V=500~1000M/MIN,? Recommended 0.05 ~ 0.5MM / R, AP is generally 0.5MM ~ 3MM.


PCBN tool turning high cobalt chromium molybdenum corrosion resistant alloy with cutting speed of 160M/MIN,