Basic knowledge of cutting tools

Advanced processing equipment and high performance CNC tools, in order to give full play to its due efficiency, to obtain good economic benefits.With the rapid development of cutting tool materials, the physical, mechanical and machining properties of various new cutting tool materials have been greatly improved, and the application scope has been constantly expanded.

Tool material should have basic properties

The choice of tool material has great influence on tool life, machining efficiency, machining quality and machining cost.Cutting tools to withstand high pressure, high temperature, friction, impact and vibration and other effects.Therefore, the tool material should have the following basic properties:

(1) hardness and wear resistance.The hardness of the cutting tool material must be higher than that of the workpiece material, generally more than 60HRC.The higher the hardness of the tool material, the better the wear resistance.

(2) strength and toughness.The cutting tool material should have high strength and toughness, so as to withstand cutting force, impact and vibration, and prevent brittle fracture and edge collapse of the tool.

(3) heat resistance.The tool material's heat resistance is good, can bear the high cutting temperature, has the good oxidation resistance.

(4) process performance and economy.Tool material should have good forging performance, heat treatment performance, welding performance;Grinding performance, and the pursuit of high performance ratio.

Tool material types, properties, characteristics, applications

1.Types, properties and characteristics of diamond tool materials and tool applications

Diamond is an isomer of carbon. It is one of the hardest materials that has been found in nature.Diamond tools have high hardness, high wear resistance and high thermal conductivity, and have been widely used in the processing of nonferrous and nonmetallic materials.Especially in the high speed machining of aluminum and silicon alloy, diamond cutting tools are the main cutting tools that are difficult to replace.Diamond cutting tools with high efficiency, high stability and long life are indispensable tools in modern CNC machining.

Type of diamond tools

(1) natural diamond cutting tools: natural diamond as a cutting tool for hundreds of years of history, natural single crystal diamond tool after fine grinding, can grinding extremely sharp blade, blade radius of 0.002 mu m, can realize the ultra-thin cutting, can work out high precision and low surface roughness of workpiece, is accepted, the ideal and does not take the place of ultra-precision machining tools.

(2) the PCD diamond tool: natural diamond is expensive, diamond is widely used in machining or polycrystalline diamond (PCD), since the early 1970 s, the use of high temperature and high pressure synthesis technology of the preparation of polycrystalline diamond (Polycrystauinediamond, hereinafter referred to as PCD blade developed later, on many occasions, natural diamond cutting tool has been replaced by artificial polycrystalline diamond.PCD is rich in raw materials and its price is only a few to a tenth of that of natural diamond.

PCD tools cannot grind out extremely sharp cutting edges, and the surface quality of processed workpiece is not as good as natural diamond, so it is not easy to manufacture PCD blades with broken chip slots in the industry.Therefore, PCD can only be used for fine cutting of non-ferrous and non-metallic metals, and it is difficult to achieve ultra-precision mirror cutting.

CVD diamond tools: since the late 1970s to the early 1980s, CVD diamond technology in Japan.CVD diamond refers to the synthesis of diamond film by chemical vapor deposition (CVD) on a heterogeneous matrix (such as cemented carbide, ceramics, etc.). CVD diamond has exactly the same structure and characteristics as natural diamond.Compared with natural diamond, the performance of CVD diamond is very close to that of natural diamond. It has both the advantages of natural single crystal diamond and polycrystalline diamond (PCD), and overcomes their disadvantages to some extent.

Diamond tool performance characteristics:

Extremely high hardness and wear resistance: natural diamond is the hardest substance that has been found in nature.Diamond has a very high wear resistance, when processing high hardness materials, the diamond tool life is carbide tool lO ~ 100 times, even up to hundreds of times.

Has a very low coefficient of friction: the coefficient of friction between diamond and some non-ferrous metals is lower than other tools, the coefficient of friction is low, machining deformation is small, can reduce the cutting force.

Cutting edge is very sharp: the cutting edge of the diamond tool can be sharpened to be very sharp. The natural single crystal diamond tool can be up to 0.002 ~ 0.008, which can carry out ultra-thin cutting and ultra-precision machining.

Has high thermal conductivity: diamond thermal conductivity and thermal diffusion rate is high, cutting heat is easy to spread out, cutting temperature is low.

With a lower thermal expansion coefficient: the thermal expansion coefficient of diamond is several times smaller than that of cemented carbide, the cutting heat caused by the change in tool size is very small, which is particularly important for precision and ultra-precision machining with high requirements for dimensional accuracy.

Application of diamond tool.

Diamond tools are used for fine cutting and boring of nonferrous and nonmetallic materials at high speed.Suitable for processing various wear-resistant non-metals, such as FRP powder metallurgy blank, ceramic materials, etc.Various wear - resistant non - ferrous metals, such as all kinds of silicon aluminum alloy;All kinds of non-ferrous metal finishing.The disadvantage of diamond tool is that its thermal stability is poor. When the cutting temperature exceeds 700℃ ~ 800℃, diamond tool will lose its hardness completely.In addition, it is not suitable for cutting ferrous metals, because diamond (carbon) at high temperature easy to interact with iron atoms, so that the carbon atoms into the structure of graphite, the tool is very easy to damage.

2.Types, properties and characteristics of cubic boron nitride cutter materials and tool applications

The second superhard material, cubic boron nitride (CBN), synthesized by a method similar to that used in diamond manufacturing, is second only to diamond in hardness and thermal conductivity. It has excellent thermal stability and does not oxidized when heated to 10000C in the atmosphere.CBN has very stable chemical properties for ferrous metals and can be widely used in the processing of steel products.

Type of cubic boron nitride cutter

Cubic boron nitride (CBN) is a substance that does not exist in nature. It can be divided into single crystals and polycrystals, namely, CBN single crystals and polycrystalline inecubic bornnitride (PCBN).CBN is one of the isomers of boron nitride (BN), whose structure is similar to that of diamond.PCBN (polycrystalline cubic boron nitride) is a polycrystalline material sintered together by the combination phase (TiC, TiN, Al, Ti, etc.) of the fine CBN material under high temperature and high pressure. It is currently the tool material second only to diamond in hardness by artificial synthesis.PCBN is mainly used to make tools or other tools.

PCBN cutter can be divided into integrated PCBN blade and cemented carbide composite sintered PCBN composite blade.

PCBN composite blade is formed by sintering a layer of o-5 ~ 1.0mm thick PCBN on a hard alloy with good strength and toughness. Its performance has both good toughness and high hardness and wear resistance. It solves the problems of low bending strength and welding difficulty of CBN blade.

The main performance and characteristics of cubic boron nitride

The hardness of cubic boron nitride is slightly less than that of diamond, but it is much higher than that of other high hardness materials.The outstanding advantage of CBN is that its thermal stability is much higher than that of diamond, which can reach more than 1200℃ (700 ~ 800℃ for diamond). The other outstanding advantage is that it has great chemical inertness and cannot react with iron at 1200 ~ 1300℃.The main properties of cubic boron nitride are as follows.

High hardness and wear resistance: CBN crystal structure is similar to diamond, with diamond similar hardness and strength.PCBN is especially suitable for machining high hardness materials which can only be grinded before, and can obtain better workpiece surface quality.

It has high thermal stability: the heat resistance of CBN can reach 1400 ~ 1500℃, almost l times higher than that of diamond (700 ~ 800℃).PCBN tools can be used to cut high temperature alloy and quenched steel 3 to 5 times faster than carbide tools.

(3) excellent chemical stability: and iron materials to 1200 -- 1300℃ does not have a chemical effect, will not like the rapid wear of diamond, then it can still maintain the hardness of cemented carbide;PCBN tools are suitable for cutting hardened steel parts and chilled cast iron, and can be widely used in high-speed cutting of cast iron.

(4) has better thermal conductivity: although the thermal conductivity of CBN is not as good as diamond, but in all kinds of tool materials, PCBN thermal conductivity is second only to diamond, much higher than high-speed steel and cemented carbide

With a lower coefficient of friction: low coefficient of friction can lead to the reduction of cutting force, cutting temperature, machining surface quality.

Cubic boron nitride tool application:

Cubic boron nitride is suitable for finishing all kinds of difficult cutting materials such as hardened steel, hard cast iron, superalloy, hard alloy and surface spraying material.The machining accuracy can reach IT5(hole is IT6), and the surface roughness value can be as small as Ra1.25 ~ 0.20 livm.

Cubic boron nitride tool material toughness and bending strength is poor.Therefore, cubic boron nitride turning tool is not suitable for rough machining with low speed and large impact load.At the same time is not suitable for cutting plastic materials (such as aluminum alloy, copper alloy, nickel alloy, plastic steel, etc.), because the cutting of these metals will produce serious chip tumor, and make the processing surface deterioration.

3.Types, properties and characteristics of ceramic tool materials and tool applications

Ceramic cutting tools have the characteristics of high hardness, good wear resistance, good heat resistance and chemical stability, and it is not easy to bond with metal.Ceramic cutting tools play a very important role in CNC machining. Ceramic cutting tools have become one of the main cutting tools for high-speed cutting and difficult material processing.Ceramic cutting tools are widely used in high speed cutting, dry cutting, hard cutting and machining of difficult materials.Ceramic cutting tools can efficiently process the high hard materials that traditional cutting tools cannot process at all, so as to realize "grinding by car".The optimum cutting speed of ceramic cutting tools can be 2 ~ lO times higher than that of cemented carbide cutting tools, thus greatly improving the cutting efficiency.The main raw material used by ceramic cutting tools is the most abundant element in the earth's crust. Therefore, the promotion and application of ceramic cutting tools is of great significance to improve productivity, reduce processing costs and save strategic precious metals. It will also greatly promote the progress of cutting technology.

Type of ceramic tool material

Ceramic cutting tool materials can be generally divided into three categories: alumina ceramic, silicon nitride ceramic, composite silicon nitride - alumina ceramic.Alumina - based and silicon nitride - based ceramic tool materials are the most widely used.The performance of silicon nitride ceramic is superior to that of alumina ceramic.

The ceramic tool performance, characteristics

The performance characteristics of ceramic tools are as follows:

High hardness, good wear resistance: although the hardness of ceramic tools is not as high as PCD and PCBN, but much higher than the carbide and high-speed steel tools, reaching 93-95hra.Ceramic cutting tools can be used to process high hard materials which are difficult to be processed by traditional cutting tools. They are suitable for high speed cutting and hard cutting.

(2) high temperature resistance, good heat resistance: ceramic tools in 1200℃ above the high temperature can still be cut.Ceramic cutting tools have good mechanical properties at high temperature. A12O3 ceramic cutting tools have particularly good oxidation resistance. The cutting edge can be used continuously even if it is in a red-hot state.Therefore, ceramic cutting tools can achieve dry cutting, which can save cutting fluid.

Good chemical stability: ceramic tools are not easy to bond with metal, and corrosion resistance, chemical stability is good, can reduce the tool bonding wear.

Low friction coefficient: ceramic tool and metal affinity is small, low friction coefficient, can reduce the cutting force and cutting temperature.

The ceramic knife has applications

Ceramic is one of the cutting tool materials mainly used for high speed finishing and semi-finishing.Ceramic tool is suitable for cutting all kinds of cast iron (gray cast iron, ductile cast iron, malleable cast iron, chilled cast iron, high alloy wear resistant cast iron) and steel (carbon structural steel, alloy structural steel, high strength steel, high manganese steel, quenched steel, etc.), also can be used for cutting copper alloy, graphite, engineering plastics and composite materials.

The ceramic cutting tools have the problems of low bending strength and poor impact toughness, so they are not suitable for cutting under low speed and impact load.

4.Properties and characteristics of coating tool materials and tool applications

Coating the cutting tool is one of the important ways to improve the performance of the cutting tool.The appearance of coating tool makes a great breakthrough in cutting performance.Coated cutting tools are coated with one or more refractory compounds with good wear resistance on the body with good toughness. It combines the base of the cutting tools with the hard coating, thus greatly improving the performance of the cutting tools.Coating tool can improve machining efficiency, improve machining accuracy, prolong tool service life and reduce machining cost.About 80% of the cutting tools used in new CNC machine tools are coated.Coating tool will be the most important tool in the field of nc machining in the future.

Type of coated knives

According to different coating methods, coating tools can be divided into chemical vapor deposition (CVD) coating tools and physical vapor deposition (PVD) coating tools.Coated carbide tools are generally used for chemical vapor deposition at a deposition temperature of about 1000℃.The coated high speed steel tool generally adopts the physical vapor deposition method, the deposition temperature is about 500℃;

According to the substrate material of coated tools, coated tools can be divided into carbide coated tools, high-speed steel coated tools, and coated tools on ceramics and superhard materials (diamond and cubic boron nitride).

According to the properties of coating materials, coating tools can be divided into two categories, that is, "hard" coating tools and "soft" coating tools.The main objectives of "hard" coated tools are high hardness and wear resistance, and their main advantages are high hardness and good wear resistance, typically TiC and TiN coatings."Soft" coating tool to pursue the goal of low friction coefficient, also known as self-lubricating tool, it and workpiece material friction coefficient is very low, only about 0.1, can reduce adhesion, reduce friction, reduce cutting force and cutting temperature.

Recently, Nanoeoating tools have been developed.This coating tool can be used in various combinations of coating materials (such as metal/metal, metal/ceramic, ceramic/ceramic, etc.) to meet different functional and performance requirements.The reasonable design of nanometer coating can make the cutting tool material have excellent anti-friction and anti-wear function and self-lubricating performance, which is suitable for high-speed dry cutting.

The characteristics of coating tools

The performance characteristics of coating tool are as follows:

(1) mechanical and cutting performance is good: coating tool will be the matrix material and coating material of good performance combined, not only to maintain the matrix of good toughness and high strength, and has a coating of high hardness, high wear resistance and low friction coefficient.As a result, the cutting speed of coated cutting tools can be more than 2 times higher than that of uncoated cutting tools, allowing for a higher feed.Coating tool life is also improved.

(2) strong versatility: coating tool versatility is wide, the scope of processing is significantly expanded, a coating tool can replace several kinds of non-coating tool use.

(3) coating thickness: with the increase of coating thickness tool life will increase, but when the coating thickness reaches saturation, tool life is no longer significantly increased.Coating is too thick, easy to cause stripping;When the coating is too thin, the wear resistance is poor.

(4) re-grinding: coating blade re-grinding poor, coating equipment complex, high process requirements, long coating time.

Coating materials: different coating materials of the tool, cutting performance is not the same.For example, when cutting at low speed, TiC coating has the advantage;TiN is more suitable for high speed cutting.

Application of coating tools

Coating tool has great potential in the field of nc machining and will be the most important tool in the field of nc machining in the future.The coating technology has been applied to the end milling cutter, reamer, drill bit, composite hole machining tool, gear hob, gear shaper, gear shaver, forming broach and all kinds of clamping indexable blades, which can meet the needs of high-speed machining of all kinds of steel and cast iron, heat resistant alloy and non-ferrous metal and other materials.

5.The types, properties, characteristics and applications of carbide tool materials

Carbide cutting tools, especially indexable carbide cutting tools, is the dominant production of nc machining tool, since the 1980 s, a variety of monolithic and indexable carbide cutting tools, or the variety of the blade has been extended to the field of all kinds of cutting tool, with indexable carbide cutting tools by a simple tool, face milling cutter to expand to the field of precision, complex, forming tools.

Type of carbide tools

According to the main chemical components, cemented carbide can be divided into tungsten carbide based cemented carbide and titanium (TiC(N) -based cemented carbide.Tungsten carbide based cemented carbide includes tungsten cobalt (YG), tungsten cobalt titanium (YT), and added rare carbide (YW), which have their own advantages and disadvantages. The main components are tungsten carbide (WC), titanium carbide (TiC), tantalum carbide (TaC), niobium carbide (NbC), etc. The commonly used metal bonding phase is Co.

Titanium carbides based on carbon (nitrogen) nitride are carbides with TiC as the main component (some with other carbides or nitrides added). The commonly used metal bonding phases are Mo and Ni.

ISO (international organization for standardization) classifies carbide for cutting into three categories:

K class, including Kl0 ~ K40, is equivalent to China's YG class (the main component is wc. Co).

Class P, including P01 ~ P50, is equivalent to China's YT class (the main component is wc.tic. Co).

M class, including M10 ~ M40, is equivalent to China's YW class (the main component is wc-tic-tac (NbC) -co).

The grades represent a range of alloys from high hardness to maximum toughness in Numbers between 01 and 50.

The carbide tool performance characteristics

The performance characteristics of cemented carbide tool are as follows:

High hardness: carbide cutting tools are made of carbide with high hardness and melting point (called hard phase) and metal binder (called bonding phase) by powder metallurgy method, its hardness is up to 89 ~ 93HRA, much higher than high-speed steel, at 5400C, the hardness can still reach 82 ~ 87HRA, and high-speed steel at room temperature hardness (83 ~ 86HRA) the same.The hardness value of cemented carbide varies with the nature, quantity, particle size and content of the metal bond phase, but generally decreases with the increase of the content of the metal bond phase.The hardness of YT alloy was higher than that of YG alloy when the content of adhesive phase was the same, and the alloy with TaC(NbC) added had higher hardness at high temperature.

(2) bending strength and toughness: the bending strength of common cemented carbide is within the range of 900 ~ 1500MPa.The higher the content of metal bonding phase, the higher the bending strength.When the content of adhesive is the same, the strength of YG (wc-co) alloy is higher than that of YT (wc-tic) alloy, and the strength decreases with the increase of TiC content.Carbide is a brittle material, its impact toughness at room temperature is only 1/30 ~ 1/8 of high-speed steel.

The application of cemented carbide tool is commonly used

YG alloys are mainly used for processing cast iron, non-ferrous and non-metallic materials.Fine grain cemented carbide (such as YG3X, YG6X) has higher hardness and wear resistance than medium grain in the same amount of cobalt, which is suitable for processing some special hard cast iron, austenitic stainless steel, heat-resistant alloy, titanium alloy, hard bronze and wear-resistant insulation materials.

The outstanding advantages of YT cemented carbide are high hardness, good heat resistance, high hardness and compressive strength at high temperature than YG, and good oxidation resistance.Therefore, when the knife is required to have high heat resistance and wear resistance, the brand with high TiC content should be selected.YT alloy is suitable for processing plastic materials such as steel, but not titanium alloy, silicon aluminum alloy.

YW alloy possesses the properties of YG and YT alloys, and has good comprehensive performance. It can be used for processing steel, cast iron and non-ferrous metals.Such alloys, if properly enriched with cobalt, can be of high strength and can be used for rough machining and intermittent cutting of all kinds of difficult materials.

6.Types, characteristics and applications of high speed steel cutters

High Speed Steel (HSS) is a kind of High alloy tool Steel with more alloying elements such as W, Mo, Cr and V.High speed steel cutting tools in the strength, toughness and process and other aspects of the excellent comprehensive performance, in the complex cutting tools, especially manufacturing hole processing tools, milling tools, thread tools, broach, cutting tools and other complex blade shape cutting tools, high speed steel still occupies a major position.High - speed steel tools are easy to grind out sharp cutting edges.

According to different USES, HSS can be divided into general HSS and high performance HSS.

General purpose high speed steel cutter

General purpose high speed steel.Generally can be divided into two kinds of tungsten steel, tungsten molybdenum steel.The content (C) of this type of high speed steel is 0.7% ~ 0.9%.According to the tungsten content of the steel, can be divided into W is 12% or 18% tungsten steel, W is 6% or 8% tungsten molybdenum steel, W is 2% or no W molybdenum steel.Universal high speed steel has a certain hardness (63-66hrc) and wear resistance, high strength and toughness, good plasticity and processing technology, so it is widely used in the manufacture of all kinds of complex cutting tools.

Tungsten steel: the typical grade of universal high speed steel tungsten steel is W18Cr4V, (W18 for short), with good comprehensive performance, the high temperature hardness at 6000C is 48.5 HRC, can be used for the manufacture of various complex cutting tools.It has the advantages of good grinding performance and small decarbonization sensitivity, but due to the high carbide content, uneven distribution, larger particles, strength and toughness is not high.

Tungsten molybdenum steel: refers to a part of tungsten steel tungsten replaced by molybdenum obtained by a high-speed steel.The typical grade of tungsten molybdenum steel is W6Mo5Cr4V2, (referred to as M2).The carbide particles of M2 are fine and uniform, and the strength, toughness and high temperature plasticity are better than W18Cr4V.Another tungsten molybdenum steel is W9Mo3Cr4V(W9 for short), its thermal stability is slightly higher than M2 steel, bending strength and toughness are better than W6M05Cr4V2, with good machining performance.

High-performance high speed steel cutting tools

High performance high speed steel (HSS) is a new type of steel with carbon content, vanadium content and alloy elements such as Co and Al added into the composition of general high speed steel, so as to improve its heat resistance and wear resistance.There are mainly the following categories:

High carbon high speed steel: high carbon high speed steel (such as 95W18Cr4V), room temperature and high temperature hardness is high, suitable for the manufacture and processing of ordinary steel and cast iron, wear resistance requirements of the higher bit, reamer, tap and milling cutter or processing of harder materials, not to bear large impact.

High vanadium high speed steel: typical grades, such as, W12Cr4V4Mo, (EV4 for short), V increased to 3% to 5%, good wear resistance, suitable for cutting the tool wear of great material, such as fiber, hard rubber, plastic, can also be used for processing stainless steel, high strength steel and high temperature alloy and other materials.

(3) cobalt high speed steel, cobalt containing superhard high speed steel, the typical brand, such as, W2Mo9Cr4VCo8, (hereinafter referred to as M42), a high degree of hardness, its hardness is 69-70 HRC, suitable for processing high strength heat-resistant steel, high temperature alloy, titanium alloy and other hard processing material, M42 grinding can be good, suitable for the production of sophisticated tools, but unfavorable work under impact cutting condition.

(4) aluminum high speed steel: is a superhard high speed steel containing aluminum, typical grades, such as, W6Mo5Cr4V2Al, (501 for short), 6000C high temperature hardness also reached 54HRC, cutting performance is equivalent to M42, suitable for the manufacture of milling cutter, drill, reamer, gear cutter, broach, for the processing of alloy steel, stainless steel, high strength steel and high temperature alloy and other materials.

(5) n superhard high speed steel: typical grades, such as W12M03Cr4V3N, short for (V3N), is a superhard high speed steel containing nitrogen, hardness, strength, toughness and M42 equivalent, can be used as a replacement for cobalt high speed steel, for low-speed cutting difficult to process materials and low-speed high precision processing.

Smelting high speed steel and powder metallurgy high speed steel

According to the different manufacturing process, HSS can be divided into smelting HSS and powder metallurgy HSS.

(1) melting high speed steel: ordinary high speed steel and high performance high speed steel are produced by melting.They are made into cutting tools by smelting, ingot casting and plating rolling.Carbide segregation is a serious problem in melting HSS. Hard and brittle carbide is not evenly distributed in HSS, and the grain size is large (up to dozens of microns), which adversely affects the wear resistance, toughness and cutting performance of HSS tools.

(2) of powder metallurgy HSS (PM HSS) : powder metallurgy HSS (PMHSS) is a high frequency induction furnace smelting of steel liquid, with high pressure argon gas or pure nitrogen atomization, quench again and get a fine uniform crystal structure (high speed steel powder), then the powder of billet in high temperature and high pressure down into the knife, or first made billet again after forging, rolling into a shape of cutting tool.Compared with HSS made by melting method, PMHSS has the advantages of fine and even carbide grains, and the strength, toughness and wear resistance of HSS are improved relatively.PMHSS tools will be further developed and play an important role in the field of complex CNC tools.Typical brands, such as F15, FR71, GFl, GF2, GF3, PT1, PVN, etc., can be used to manufacture large-size, heavy-duty, high-impact tools, as well as precision tools.

CNC tool material selection principles

At present, the widely used CNC tool materials mainly include diamond tool, cubic boron nitride tool, ceramic tool, coating tool, carbide tool and high-speed steel tool.Tool material total brand, its performance varies greatly.The following table shows the main performance indicators of various tool materials.

CNC machining tool material must be selected according to the workpiece processed and the processing nature.The selection of cutting tool materials should be matched with the processing object, the matching of cutting tool materials with the processing object, mainly refers to the matching of mechanical properties, physical properties and chemical properties of the two, in order to obtain the longest tool life and maximum cutting productivity.

1.The material of cutting tool matches the mechanical properties of machining object

The problem of mechanical properties matching between cutting tools and machining objects mainly refers to the matching of mechanical properties such as strength, toughness and hardness between cutting tools and workpiece materials.The cutting tool materials with different mechanical properties are suitable for different workpiece materials.

The hardness order of tool materials is: diamond tool > cubic boron nitride tool > ceramic tool > carbide > high speed steel.

The order of the bending strength of the cutting tool materials is: > high speed steel > cemented carbide > ceramic cutting tool > diamond and cubic boron nitride cutting tool.

(3) the order of toughness of tool materials is: > high speed steel > hard alloy > cubic boron nitride, diamond and ceramic tools.

High hardness workpiece material, must be processed with a higher hardness tool, tool material hardness must be higher than the workpiece material hardness, generally required in 60HRC above.The higher the hardness of the cutting tool material, the better its wear resistance.For example, when the amount of cobalt in cemented carbide increases, its strength and toughness increase, and its hardness decreases, so it is suitable for rough machining.When the amount of cobalt decreases, its hardness and wear resistance increase, suitable for finishing.

Cutting tools with excellent mechanical properties at high temperature are especially suitable for high speed machining.The high temperature performance of ceramic tool enables it to cut at a high speed, which is 2 ~ 10 times faster than that of cemented carbide.

2.The cutting tool material matches the physical properties of the machining object

Tools with different physical properties, such as high-speed steel tools with high thermal conductivity and low melting point, ceramic tools with high melting point and low thermal expansion, and diamond tools with high thermal conductivity and low thermal expansion, are suitable for different workpiece materials.When machining the workpiece with poor thermal conductivity, the tool material with good thermal conductivity should be used so that the cutting heat can be transferred out quickly and the cutting temperature can be reduced.Due to the high thermal conductivity and thermal diffusivity of diamond, the cutting heat is easy to spread out and does not produce great thermal deformation, which is particularly important for precision machining tools requiring high dimensional accuracy.

Heat resistant temperature of various tool materials: diamond tool is 700 ~ 8000C, PCBN tool is 13000 ~ 15000C, ceramic tool is 1100 ~ 12000C, TiC(N) base cemented carbide is 900 ~ 11000C, WC base ultra-fine grain cemented carbide is 800 ~ 9000C, HSS is 600 ~ 7000C.

The order of thermal conductivity of various tool materials: PCD>, PCBN>, WC based cemented carbide >TiC(N), based cemented carbide >, HSS>, Si3N4, >, A1203, ceramic.

The order of thermal expansion coefficient of various cutting tool materials is as follows: HSS>WC based cemented carbide >TiC(N)>A1203 based ceramic >PCBN>Si3N4 based ceramic >PCD.

The order of thermal shock resistance of various tool materials is as follows: HSS>WC based cemented carbide >Si3N4 ceramic >PCBN>PCD>TiC(N) based cemented carbide >A1203 ceramic.

3.The cutting tool material matches the chemical properties of the machining object

The matching of chemical properties between cutting tool materials and machining objects mainly refers to the matching of chemical property parameters such as chemical affinity, chemical reaction, diffusion and dissolution between cutting tool materials and workpiece materials.Materials different tools are suitable for processing the workpiece material is different.

A variety of cutting tool materials anti-bonding temperature (and steel) : PCBN> ceramic > carbide >HSS.

The antioxidant temperature of various cutting tool materials is as follows: ceramic >PCBN> carbide > diamond >HSS.

The diffusion strength of various cutting tool materials (for steel) is: >Si3N4 base ceramics >PCBN>A1203 base ceramics.The diffusion strength (for titanium) is: a 1203-based ceramic >, PCBN, >, SiC, >, Si3N4, > diamond.

4.Reasonable selection of nc tool material

Generally speaking, PCBN, ceramic tools, coated carbide and TiCN base carbide tools are suitable for nc machining of ferrous metals such as steel;PCD tools are suitable for the processing of Al, Mg, Cu and other non-ferrous metal materials and their alloys and non-metallic materials.Table 3-3-2 lists some workpiece materials suitable for machining the cutter materials mentioned above.

The following table shows a variety of tool materials suitable for processing some workpiece materials.