PCBN cutting tools

PCBN tools are artificial cubic boron nitride cutting tools, but also to maintain it at a high temperature characteristics of high hardness, mainly to do with the

processing of iron. Cubic boron nitride CBN (Cubic Boron Nitride) is the use of artificially synthesized under high temperature and pressure, and its hardness second

only

Diamond is much higher than in the other materials, it referred to as the diamond superhard material.
Feature
CBN has high hardness, chemical inertness and high temperature thermal stability, so widely used as an abrasive CBN grinding wheel. As CBN tool materials with

properties superior to the other, so people start by trying to apply it cutting, but crystal

CBN particles is small, difficult to be made knives, and CBN sintered poor, difficult CBN sintered body made larger, until the 1970s, the former Soviet Union, China,

the United States, Britain and other countries have been successfully developed only as cutting tools CBN sintered body - Polycrystalline Li

Fang BN PCBN (Polycrystalline Cubic Boron Nitride). Since then, PCBN cutting performance with its superior machinability applied in various fields, especially in high

hardness materials, cutting difficult materials processing is unique. After more than 30

Years of development and application, has now emerged for the processing of different materials, PCBN cutting tool materials.
Species
By adding ingredients points: a single crystal directly from the CBN and PCBN sintered add a certain percentage of binder PCBN sintered body into two categories; press

the manufacture of composite points: a whole block and with PCBN sintered carbide composite sintered PCBN composite film categories. Currently a wider application

PCBN is a composite sheet with the adhesive according to the proportion of the added binder hardness is different from the type of the PCBN, the more the binder

content lower hardness, toughness better; binders different types, the use of PCBN also different, as shown in Table 1, the binder common PCBN

Tool and its use.
Use
CBN content (%) - Binder Type - The main purpose
~ 60-TiN-hardened steel
~ 70-TiC-iron
~ 70-Al2O3-iron
~ 90-AlN-high-strength cast iron
~ 80-Co-heat-resistant alloy cast iron
Production Process
Processing of raw materials
CBN powder in the residual WBN, HBN, pyrophyllite, graphite, magnesium, iron and other impurities; additional powder and binding agent which contain adsorbed oxygen,

water vapor, the sintered negative. Therefore, purification and treatment of raw materials to ensure the performance of synthetic polycrystalline important part of

. When we use the following methods developed by the CBN powder and a binder material for purification treatment: first in the 300 C about treatment with NaOH CBN

emblem powder, remove one of the pyrophyllite and HBN; perchloric acid and then boiled to remove graphite; finally heating with HCl in board boiled to remove gold

Genus, and washed with distilled water to neutral. Binders used Co, Ni, Al, etc. by hydrogen reduction treatment. Then CBN and binding agent by a certain ratio and

mixing parameters into a graphite die, into the pressure is less than 1E2 vacuum furnace, heating 800 ~ 1000 ° C treatment 1h,

Remove the surface dirt, adsorbed oxygen and water vapor, so that the CBN grain surface is very clean.
Binder material selection and dosage, the total amount of binder added, but not too much should be sufficient. Experimental results show that the wear resistance and

flexural strength of polycrystalline and mean free path (the thickness of the binder phase) close, when the mean free path is 0. 8 ~ 1.2μm when

, The highest ratio of polycrystalline wear, when incorporated in an amount of binding agent 10% to 15% (mass ratio).
In addition to the choice of binder addition, CBN particle size and particle size ratio is also crucial to determine the root exclusion of machining accuracy and

surface quality requirements, the CBN cutting tools manufacturing granularity divided roughly into: coarse-grained 20 ~ 30μm; Particle size 3 10 microns; granular 2

microns. Use

Coarse-grained polycrystalline made it difficult to make high precision tool, but its abrasion resistance, high impact resistance, made of fine-grained polycrystalline

tool made to meet the requirements of finishing and super finishing
Synthetic embryo
PCBN composite film is directly under heat and pressure to CBN carbide substrate layer and the composite together, after cutting, welding molding made of a variety of

welding or cutting tool inserts. Overall PCBN sintered block is directly sintered alloy substrate with a whole PCBN cutter Pei,

After post-sharpening blade made of polycrystalline cubic boron nitride as a whole.
Overall polycrystalline cubic boron nitride inserts
Synthesis equipment abroad, mostly used on both sides of the top synthetic device presses, domestic mostly cubic press.
PCBN tool grinding process
Production of the PCBN tool can be used for the embryo to sharpening cutting, grinding tools for the correct geometry and surface roughness. General points roughing,

finishing and polishing process. 180 to 240, using coarse resin bond diamond grinding wheel, the amount of feed is 0. 01 mm /

Double stroke; grinding with wlo ~ W14 resin bonded grinding wheel, the amount of feed is 0. 005 mm / double stroke; W5 ~ W3 diamond grinding wheel or grinding paste,

abrasive grinding diamond wheel should pay special attention to the opening edge Dressing for sharpening effect. Despite the sharpening process

End face of the tool in the wheel back and forth across the surface of the grinding wheel to consume the same, but in fact is still prone to uneven wheel surface to be

trimmed regularly.
PCBN tool geometry parameters
PCBN tool life is closely related to its geometry, the right front corner of the tool can be improved impact resistance. Chip capacity and cooling capacity. Rake angle

directly affects the size of the cutting edge and the blade of the forces within the state of stress. To avoid tip withstand mechanical

The impact caused by the tensile stress is too large, the general negative rake angle (-5 ~ - 10), while reducing wear and tear after a corner, primary and secondary

clearance angle of 6. , The tip radius of 0.4-1.2mm fillet and chamfer grinding smooth.
PCBN tool inspection
In addition to testing the hardness index, slightly bending, tensile strength and other physical properties, but also need to use high-powered electron microscope

examination PCBN tool surface and edge processing accuracy. Then dimensional inspection, precision detection, M values, and geometric tolerances, roughness, and then

packed into

Libraries.
Production Quality
1, high purity, high purification rate of raw materials, reliable synthesis embryo specification, these two directly determines the performance of cubic boron nitride

cutting tool. Of course, this is also the cubic boron nitride cutting tools on the market price of the uneven biggest reason.
2, grinding, unlike the cubic boron nitride cutting tools with complex geometries and carbide blade coating performance depends on the performance tool embryo, while

the grinding process and precision cutting directly determine the microscopic properties. So the use of peripheral grinding machine, tool costs

While increasing a lot, but the quality and cubic boron nitride cutting tool durability will be on the next level.
3, strict testing means: In addition to dimensional accuracy and surface quality, cubic boron nitride cutting tools production process, is the most prone to waste

under the electron microscope microscopic detection of defects. Edge at the invisible microscopic defects is cubic boron nitride cutting tool chipping during use

The mouth of the fuse, making it easy to use tool bar knife when problems arise.
From the use of perspective: impact performance, especially in rough field use without chipping, not fragmentation, which is cubic boron nitride cutting tools using

the most basic security guarantees. Good wear resistance, efficient processing at the same time, instead of carbide cutting tools can cost

And ceramic blade, which is cubic boron nitride cutting tools use economical guarantee.
As much as high-end products PCBN cutting tools, manufacturing strength, high technical threshold. In the non-composite superhard cutting tool market, the overall

polycrystalline cubic boron nitride inserts are already strengths.
Cutting
Because the crystal and diamond crystals are of CBN blende type, and similar lattice constant, the same chemical type, and thus the hardness of CBN and diamond has a

compressive strength of close to, but also because it is N, B composed of atoms, and therefore has more than a higher thermal stability of diamond

And chemical inertness. PCBN cutting tool material main properties are as follows:
With high hardness and wear resistance
The microhardness of the single crystal CBN HV8000 ~ 9000, is now known to the second high-hardness material, PCBN composite sheet hardness is generally HV3000 ~ 5000.

Therefore, for the processing of high hardness materials and ceramics higher than the wear resistance of cemented carbide, to reduce large

Machining of size deviation or size dispersion, especially for high degree of automation devices, can reduce tool spatula auxiliary time to be fully realized

performance.
With high thermal stability and high temperature hardness
CBN heat resistance up to 1400 ~ 1500 ℃, at 800 ℃ Al2O3/TiC hardness of the ceramic temperature hardness, therefore, when the cutting temperature is high, causes the

softened material to be processed, the tool increases the hardness difference between the is beneficial for cutting, while the tool life

Little impact.
With high chemical stability
CBN has a high antioxidant capacity, at 1000 ℃ not produce oxidation, with the iron-based material while the 1200 ~ 1300 ℃ chemical reaction does not occur, but in

about 1000 ℃ produce the hydrolysis with water, resulting in a large number of CBN is abrasion, so use PCBN cutting tools

Wet cutting should pay attention to select the type of cutting fluid. Under normal circumstances, the wet PCBN cutting tool life for no obvious increase, so often used

when using PCBN cutting tools for dry cutting method.
With good thermal conductivity
CBN materials, thermal conductivity of diamond, but much higher than tungsten carbide, and with improved cutting temperature, PCBN cutting tool increasing the thermal

conductivity, so the heat can rapidly spread at the tip, is conducive precision of the workpiece improved.
Has a low coefficient of friction
CBN with a different coefficient of friction between 0.1 to 0.3, significantly lower than the coefficient of friction alloy (0.4 to 0.6), and the friction velocity and

with the increase of the positive pressure decreases slightly. Therefore, low friction coefficient and excellent anti-blocking ability, the CBN cutting tool

Retention is not easy to form a layer or BUE, is conducive to improving the quality of the machined surface.
Applications
For high-speed and ultra-high-speed machining technology
PCBN tool best suited for cast iron, hardened steel and other materials, high-speed machining. PCBN cutting tool by the cast iron and hardened steel cutting tool flank

wear and can be seen from the relationship: When the cutting speed exceeds a certain limit, the higher the cutting speed, PCBN cutting tools

Flank wear rate but smaller, the high-speed cutting tool life under rather high, a feature that is particularly suitable for modern high-speed machining.
Hard cutting tool materials processing technology best
For quenching hardware (hardness HRC55 or more) of the finishing, usually grinding way to accomplish, but with the development of cutting tool materials and lathe

(especially CNC lathe) machining accuracy increased to hard cutting instead of grinding to finish parts The final processing has become an

The new finishing way that this kind of car instead of grinding process method has the following advantages:
(1) can improve the processing of flexible, breaking the restrictions grinding wheel, by changing the cutting edge and the cutting means of the geometrical shapes can

be processed of the workpiece;
(2) cutting the increasingly serious environmental problems, grinding waste generated and waste treatment and removal more difficult, but also harmful, and hard

cutting without adding coolant, is of great significance;
(3) high cutting efficiency, the processing time is short, the equipment investment costs, it can reduce processing costs;
(4) removal of the energy consumed by the same volume of only 20% of the grinding, resulting in less heat cutting, the machined surface does not easily cause burns and

small cracks, easy to maintain the integrity of the surface properties;
(5) The same metal removal cases, hard cutting energy savings compared to grinding.
Typically used for hard cutting tool materials are ceramics, TiC coated inserts and PCBN cutting tool materials, but at higher speeds (1000m/min above) under the Hard

turning, PCBN tool material is the best breed. If the auto gearbox synchronizer sleeve fork (Material

20CrMnTi, hardness HRC58 ~ 62) used in vehicles instead of grinding process, the efficiency is improved more than four times, the processing cost of the grinding

process reduces the original 1/3 to 1/2.
Dry cutting technology ideal tool material
As economic and environmental reasons, in recent years, dry machining method has become the focus of the field of machinery manufacturing research. We first look wet

cutting process due to the use of cutting fluid problems caused by:
(1) long-term exposure to air or machining, cutting heat caused by the cutting fluid mist evaporation, easily contaminated environment, endanger the health of the

operator, the cutting fluid of sulfur, chlorine and other additives, the greater the damage affecting surface quality;
(2) cutting fluid affect the processing costs, according to statistics, the cutting fluid production costs accounted for 15% of the cost of tools only 3% to 4%;
(3) cutting fluid leakage, overflow will pollute the environment, prone to safety, quality incidents;
(4) cutting fluid transport, recovery, filtering device and higher maintenance costs, increased production costs.
For these reasons, dry machining process has been in the Western industrial countries have considerable application. Makino's recommended by the American "red

crescent" (Red Crescent) Dry cutting process, both can give full play to the cutting tools, but also large compared with the wet cutting

Greatly improve productivity. The mechanism is due to high cutting speed, the heat gathered in front of the tool, the cutting material reaches the vicinity of the red

hot condition, the yield strength decreased, thus the effect to improve cutting efficiency. Red Crescent dry cutting process using a precondition

Cutting pieces at higher temperatures, the strength of the material to be cut significantly decreased, becoming easy cutting, and cutting tool material strength in the

same state to have a good red hardness and thermal stability, but also have good resistance to wear resistance and adhesion.
Process suitable for dry cutting tool materials are ceramics, cermets, coated cemented carbide and PCBN cutting tool materials, etc., but on the hardness and thermal

stability for the red, PCBN material is the most suitable process for dry cutting tool materials, and As PCBN cutting tool material has the advantage

, Under conditions more suitable for high-speed dry cutting, PCBN cutting tool with a gray cast iron cutting wet and dry cutting comparison of both cases, it can be

seen: PCBN case in high speed dry cutting, wet cutting higher than tool life.
Suitable for automated processing and machining difficult materials
PCBN tools have high hardness and abrasion resistance at high cutting speeds for a long time precision machined parts (size dispersion small), greatly reducing the

number of tool changes and tool wear compensation down the time it takes. Therefore, it is suitable for CNC machine tools and automation

Higher levels of processing equipment, and can make high-performance equipment to get into full play.
Applications in difficult to machine materials, PCBN cutting tool also shows its superior performance, such as surface spray (paint) materials processing, tooling with

other materials, tool life is very low, and can not use grinding method of processing, and PCBN is The only suitable tool materials; and

For example, in the oil power plant equipment used in high-alloy cast iron, using PCBN cutting tools carbide tools improve cutting efficiency compared to more than

four times the cost of a single piece tool down to the original 1/5. Also in the sintered material such as cemented carbide cutting processing, PCBN cutting tools

Also showed a good cutting performance.
PCBN cutting tool application examples
As PCBN high hardness and wear resistance, high temperature does not react with the iron group metal chemical inertia, so the main material for high hardness and

cutting difficult materials, such as hardened steel, high alloy wear cast iron, high temperature alloy, high speed steel, surface spray

Welding materials, sintered metal materials and other difficult materials cutting.
(A) processing of hardened steel, can play in turning instead of grinding effect, because the grinding depth greater than the depth of cut more than ten times, so high

processing efficiency, the surface does not produce burns. If turning instead of grinding speed sliding gear (20CrMnTi, hardness HRC58 ~ 62), the cut

Cutting grinding efficiency than the original four times.
(2) high-alloy (tungsten or chromium 18%) cast iron, carbide cutting speed compared to more than 10 times, more than four times the cutting efficiency.
(3) processing of high-cobalt-chromium-molybdenum corrosion resistant alloy, PCBN cutting speed is 160m/min, is eight times carbide cutting tools.
(4) Processing thermal spraying (spray) materials, surface grinding spray member can not be used, but with low efficiency carbide cutting tool, switch after PCBN tools

improve processing efficiency, to save processing costs more than 50%. PCBN tools can be used to close the essence of non-ferrous metals

Cut and sintered metal cutting and so on.
Caution
If the correct choice of cutting, tool geometry and other processing conditions, it is an efficient long-life PCBN cutting tools, to create a high economic benefits,

but if you use improper methods, it will cause a great waste.
(A) a reasonable choice of cutting parameters: cutting speed should be selected according to material to be processed, generally much higher than the carbide tools.

Cutting hardness HRC55 ~ 65 hardened steel optional cutting speed 80 ~ 120m/min, PCBN cutting hard materials is due to the cutting area

Small areas within a metal softening of the applicants, thus cutting speed is too low, you can not play PCBN cutting tools. Feed generally not greater than 0.2mm / r,

cutting depth generally choose less than 0.3mm.
(2) a reasonable choice of tool geometry parameters: Since PCBN tool toughness than ceramics, less than carbide, so the choice of tool geometry parameters of the main

consideration is to ensure edge strength, rake angle generally opt (0 ° ~ -10 °), posterior horn choose a smaller, 10

°. Addition to special requirements in order to ensure tip strength, knife sharp corners generally not less than 90 °; blade to grind negative chamfer, generally

taken to be 0.2mm × (-15 ° ~ -30 °), before use use 30 ~ 50 times the magnifying glass on the tool checks to ensure cutting edge without chipping.
(3) cooling and lubrication: the tool to other materials, the use of coolant will help improve surface finish and longer tool life, but for PCBN tools except in very

special circumstances, do not add coolant to achieve the desired processing of the same quality and longer tool life of PCBN

Tool is not afraid of hard afraid soft. If coolant is used, you can not use water-soluble coolant, because CBN easy to produce at 1000 ℃, hydrolysis, resulting in a

serious tool wear.
(4) of the machine process systems: As PCBN tool used for hardened steel and cast iron and other difficult to machine materials, cutting and chamfering tool has a

negative, and thus greater radial force. This requires the machine rigidity and precision is better, the system should be small vibration, tool overhang installation

Arm should be small, PCBN cutting tool is not suitable for waste-sided machining.
At present, although the relative price of PCBN cutting tool material carbide and ceramic tools price is also high, but equally to each of the tool on the workpiece

material costs are lower than other tools, the use of advanced machining technology when, if grinding machine and other production equipment investment apportioned

Costs, the use of PCBN tools will bring greater economic benefits. SMEs in general, finishing grinding process is always the bottleneck in the manufacturing process,

if the purchase of good performance lathes, using PCBN cutting tools, application to turning instead of grinding and other advanced machining work

Arts, save equipment investment, increased productivity, but also greatly increase the flexibility of the processing. In addition, the present due to the increase of

personnel costs and environmental requirements, and vigorously promote the use of PCBN cutting tools, give full play to their potential effectiveness, improve

machinability

Technical level is of great significance.
Rational use
As PCBN cutting tool material has excellent cutting performance, it is particularly suitable for processing more than its hardness HRC45 hardened steel, cast iron,

HRC35 or more heat-resistant alloys, and the other blade HRC30 less difficult machining pearlitic gray cast iron.
In order to give full play to the superiority of PCBN inserts, obtain satisfactory processing results in practical use, refer to Table 1 in addition to the recommended

cutting PCBN inserts optional, but should be based on the machine, the workpiece and other relevant conditions fully into account the specific circumstances , co-

Reasonable choice.
1 hard cutting, the radial force is large, which requires the machine power to a large, rigid machine tool system is better, it will not only protect PCBN cutting

tools, and be satisfied with the processing results. Clamping PCBN tool, the tool overhang length should be as short as possible in order to prevent chatter Arbor

Vibration and deformation of the PCBN tool maintaining good processing condition.
Table 1 PCBN cutting blade used
Workpiece material cutting speed (m / min) Feed (mm / r) Cutting depth (mm)
Gray cast iron 180 ~ 230HB 400 ~ 1000 0.15 ~ 0.5 0.12 ~ 2.0
Hard cast iron 400HB 70 ~ 150 0.15 ~ 0.5 0.12 ~ 2.0
Hardened steel 45HRC 60 ~ 140 0.15 ~ 0.5 0.2 ~ 2.5
Heat-resistant alloy 35HRC 100 ~ 240 0.05 ~ 0.3 0.1 ~ 2.5
2.PCBN intensity ratio of carbide cutting tools is low, so the hard cutting machining, usually with a negative rake angle, the larger the posterior horn and negative

chamfer, which is not only conducive to the cutting edge reinforcement, and with good wear resistance. Usually take negative chamfer dimension

(0.1 ~ 0.5) × (10 ° ~ 30 °) is appropriate. If cutting the appropriate passivation, the effect will be better. In addition, where possible, try using a small main

angle and large nose radius, which helps protect the blade, extending the use of the tool

Life.
3 In order to make good use of PCBN cutting tools, stable control of workpiece quality, accurate judgment PCBN tool durability is essential. If you have been using the

tool wear has been very serious, then the cutting force and cutting temperature increases, cutting poor, it is difficult to control the workpiece feet

Inch and surface integrity, and even unable to continue grinding PCBN tools scrapped. In order to ensure the normal use of the tool, we recommend PCBN tool flank wear

reached 0.3 ~ 0.6mm (fine car take a small value) should be reground. However, some devices require regrinding

And skills, most factories do not have a machine suitable conditions, the general PCBN tool regrinding should be done by a professional factory.
4 For high hardness and irregular workpieces, as PCBN inserts more brittle, afraid to shock. Cut from the workpiece face, cut out, especially in the surface of the

slag, sand holes, uneven, it is most prone to shocks, so that edge rupture, resulting in reduced durability. Therefore, in

Using PCBN tools, the best first roughing chilled layer once, and the workpiece the Leads chamfered end first, to reduce the impact of PCBN cutting tools.
5.PCBN tool is not suitable for machining ferrous materials softer.
6 to determine the cutting speed, feed rate and cutting depth and comprehensive consideration of productivity and processing costs. In general, the cutting speed is

higher than about 2 times carbide tools, high cutting speed cutting generate large heat the plastic material to be processed increases,

Help control chips and reduce cutting forces.
7 using PCBN tools, it can add coolant, or not added, when the use of coolant must be fully cooled.
For information about using PCBN tool commonly wear, wear causes and preventive measures are shown in Table 2.
Table 2 PCBN blade wear forms, causes and preventive measures
Wear form mainly preventive measures
Crater wear hardness of the workpiece is too soft; cutting speed is too fast; produce chemical and diffusion wear instead carbide or ceramic knives; reduce cutting

speed used coolant
Pressure surface abrasion cutting speed is too fast; feed too; tool clearance angle is too small to increase the cutting speed and feed rate; increased posterior horn
Wear the main angle boundaries too; feed too; cutting speed is too small to reduce the main angle; reduce feed rate; increased cutting speed
Wear fracture system rigidity; small sharp knife; feed and cutting speed is too big; tool edge brittle improve system rigidity, increasing knife sharp corners; Reduce

the feed rate and cutting speed and the use of negative chamfer tool
PCBN layer of broken system rigidity; workpiece impact too; PCBN layer is too thin, too brittle tool edge technology system to improve rigidity; workpiece surface

preparation and chamfers; PCBN using thick layers; using negative chamfering tool
Grinding
Vitrified diamond wheel vitrified bond diamond and combine common characteristics, with strong grinding, grinding temperature is relatively low, abrasive wear is

relatively small; coolant can be adapted to a variety of role; grinding abrasive shape maintain good, fine grind the workpiece

High; Abrasives has more holes, grinding will help chip and heat, easy to plug, not burn the workpiece; abrasive relatively good self-sharpening, finishing a long time

interval, trimming easier and so on.
Select reasonable parameters, vitrified diamond grinding wheel during the grinding PCBN cutting tools, due to resin bond is relatively soft, easily deformed when

grinding, grinding PCBN tools can not effectively; grit metal bond because of the ability to bind too Strong self-sharpening abrasive leaving

Poor, grinding efficiency is low, and metal bonded grinding wheel will cause the edges of PCBN tools most serious damage; integrated grinding efficiency, durability

and abrasive machining the workpiece surface quality vitrified diamond grinding wheel is PCBN cutting tools ideal choice.