Basic information for CNC machining cutting tool
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Update time : 2017-10-17 17:44:00
Cutting tool cutting performance pros and cons, a direct impact on the production efficiency, processing quality and production costs. The cutting performance of the tool, first of all depends on the cutting part of the material; followed by the geometry and tool structure selection and design is reasonable.
First, the basic requirements of the tool material
In the cutting process, the cutting part of the tool not only to bear a great cutting force, but also to bear the chip deformation and friction generated by the high temperature, to maintain the cutting capacity of the tool, the tool should have the following cutting performance.
1. High hardness and abrasion resistance
The hardness of the tool material must be higher than the hardness of the workpiece material. At room temperature should generally be above HRC60. In general, the higher the hardness of the tool material, the better the wear resistance.
2. Sufficient strength and toughness
Cut the cutting part to bear a lot of cutting force and impact. Therefore, the tool material must have sufficient strength and toughness.
3. Good heat resistance and thermal conductivity
The heat resistance of the tool material is to maintain its hardness and strength at high temperatures, the better the heat resistance, the ability of the tool material to resist plastic deformation at high temperatures, and the stronger the resistance to abrasion. The better the thermal conductivity of the tool material, the more heat generated when cutting heat conduction, thereby reducing the cutting part of the temperature, reduce tool wear.
4. Good craftsmanship
For ease of manufacture, the tool material is required to have good workability. Including hot workability (thermoplastic, weldability, hardenability) and machinability.
5. Good economy
Second, commonly used tool materials
There are many types of tool materials, commonly used tool steel, including: carbon tool steel, alloy tool steel and high speed steel), cemented carbide, ceramics, diamond and cubic boron nitride.
Carbon tool steel and alloy tool steel, due to poor heat resistance, should only be hand tools.
Ceramics, diamond and cubic boron nitride, due to crisp, poor process and expensive and other reasons, only in a small range of use.
The most commonly used tool material is high speed steel and cemented carbide.
1. High speed steel
Is in the alloy tool steel to add more tungsten, molybdenum, chromium, vanadium and other alloy elements of high alloy tool steel. It has a high strength, toughness and heat resistance, is currently the most widely used tool materials. Due to sharpening when easy to get sharp edge, also known as "Feng Gang".
High-speed steel according to different uses, can be divided into ordinary high-speed steel and high-performance high-speed steel.
1) ordinary high-speed steel ordinary high-speed steel has a certain hardness (62 ~ 67 HRC) and wear resistance, high strength and toughness, cutting steel cutting speed is generally not higher than 50 ~ 60m / min, not suitable for high-speed cutting And hard material cutting. Common grades are W18Cr4V, W6Mo5Cr4V2.
2) high-performance high-speed steel in ordinary high-speed steel to increase the carbon, vanadium content or add some other alloy elements and get heat resistance, higher wear resistance of the new steel. But the overall performance of such steel as ordinary high-speed steel. Commonly used brands are 9W18Cr4V, 9W6Mo5Cr4V2, W6Mo5Cr4V3 and so on.
2.Tungsten Carbide cutting tool
Carbide is a high hardness and melting point of the carbide, with Co, Mo, Ni as a binder sintered powder metallurgy products. Its room temperature hardness of up to 78 ~ 82 HRC, 850 ~ 1000 ℃ high temperature, cutting speed than high-speed steel 4 to 10 times higher. But the impact toughness and bending strength than the high-speed steel is poor, so rarely made the overall tool. In actual use, the carbide blade is often welded or mechanically clamped to the cutter body.
China's current production of cemented carbide is divided into three categories:
1) Class K (YG)
That is, tungsten and cobalt, composed of tungsten carbide and cobalt. This kind of hard alloy toughness is better, but the hardness and wear resistance is poor, suitable for processing cast iron, bronze and other brittle materials. Commonly used grades are: YG8, YG6, YG3, they are manufactured in turn for rough processing, semi-finishing and finishing. Numbers indicate the percentage of Co, YG6 containing 6% Co, the more Co, the better the toughness.
2) P class (YT)
Tungsten and cobalt, composed of tungsten carbide, titanium carbide and cobalt. This type of cemented carbide heat resistance and wear resistance is better, but the impact toughness is poor, suitable for processing steel and other tough materials. Commonly used brands are: YT5, YT15, YT30, etc., where the figures that the percentage of titanium carbide content, the higher the content of titanium carbide, the wear resistance is better, the lower the toughness. These three grades of carbide manufacturing tools are suitable for roughing, semi-finishing and finishing.
3) Class M (YW)
Tungsten and cobalt tantalum and niobium. By adding a small amount of rare metal carbide (TaC or NbC) to the tungsten-cobalt-based cemented carbide. It has the advantages of the first two types of cemented carbide, with its manufacture of both the processing of brittle materials, but also processing tough materials. At the same time can also processing high-temperature alloys, heat-resistant alloys and alloy cast iron and other difficult materials. Common grades are YW1, YW2.
Third, the other tool material profile
Coated cemented carbide
This material is coated with a layer of very thin hard and abrasion resistance by chemical vapor deposition (CVD) or physical vapor deposition (PVD) on hard or alloy substrates or high speed steel substrates Extremely difficult refractory metal compounds are obtained from the tool material. In this way, the tool has both the strength and toughness of the base material and the high wear resistance. Commonly used coating materials are TiC, TiN, Al2O3 and so on. TiC toughness and wear resistance; TiN anti-oxidation, anti-adhesion is good; Al2O3 good heat resistance. The coating material can be selected according to the different needs.
2. Ceramics
Its main component is Al2O3, the blade hardness of up to 78 HRC above, the ability of 1200 ~ 1450 ℃ high temperature, it can withstand higher cutting speed. But the bending strength is low, the impact toughness is poor, easy to chipping. Mainly used for steel, cast iron, high hardness materials and high-precision parts of the finishing.
3. Diamond
Diamond is made of artificial and natural two kinds of cutting tools, most of the artificial diamond, its hardness is extremely high, up to 10000 HV (carbide only 1300 ~ 1800 HV). Its wear resistance is 80 to 120 times the carbide. But the blade is poor, the affinity of the iron family material. Therefore, generally not suitable for processing ferrous metals, mainly used for hard alloy, glass fiber plastic, hard rubber, graphite, ceramics, nonferrous metals and other materials, high-speed finishing.
4. Boron nitride (CNB)
This is a synthetic superhard tool material, its hardness up to 7300 ~ 9000HV, second only to the hardness of the diamond. But the thermal stability is good, can be resistant to 1300 ~ 1500 ℃ high temperature, and iron family of small affinity. But the strength is low, poor weldability. At present mainly used for processing hardened steel, chilled cast iron, high temperature alloys and some difficult to process materials.
In general, the coating cutting tool is mainly four types: coated high speed steel cutting tools, coated carbide cutting tools, and ceramic and superhard materials (diamond or cubic boron nitride) blade on the coating tool. But before the two kinds of coating tools used the most. The coating on the ceramic and superhard material blades is a material with a lower hardness than the substrate. The purpose is to improve the fracture toughness of the blade surface (which can be increased by more than 10%), which can reduce the cutting edge and breakage of the blade and expand the application range.
First, the basic requirements of the tool material
In the cutting process, the cutting part of the tool not only to bear a great cutting force, but also to bear the chip deformation and friction generated by the high temperature, to maintain the cutting capacity of the tool, the tool should have the following cutting performance.
1. High hardness and abrasion resistance
The hardness of the tool material must be higher than the hardness of the workpiece material. At room temperature should generally be above HRC60. In general, the higher the hardness of the tool material, the better the wear resistance.
2. Sufficient strength and toughness
Cut the cutting part to bear a lot of cutting force and impact. Therefore, the tool material must have sufficient strength and toughness.
3. Good heat resistance and thermal conductivity
The heat resistance of the tool material is to maintain its hardness and strength at high temperatures, the better the heat resistance, the ability of the tool material to resist plastic deformation at high temperatures, and the stronger the resistance to abrasion. The better the thermal conductivity of the tool material, the more heat generated when cutting heat conduction, thereby reducing the cutting part of the temperature, reduce tool wear.
4. Good craftsmanship
For ease of manufacture, the tool material is required to have good workability. Including hot workability (thermoplastic, weldability, hardenability) and machinability.
5. Good economy
Second, commonly used tool materials
There are many types of tool materials, commonly used tool steel, including: carbon tool steel, alloy tool steel and high speed steel), cemented carbide, ceramics, diamond and cubic boron nitride.
Carbon tool steel and alloy tool steel, due to poor heat resistance, should only be hand tools.
Ceramics, diamond and cubic boron nitride, due to crisp, poor process and expensive and other reasons, only in a small range of use.
The most commonly used tool material is high speed steel and cemented carbide.
1. High speed steel
Is in the alloy tool steel to add more tungsten, molybdenum, chromium, vanadium and other alloy elements of high alloy tool steel. It has a high strength, toughness and heat resistance, is currently the most widely used tool materials. Due to sharpening when easy to get sharp edge, also known as "Feng Gang".
High-speed steel according to different uses, can be divided into ordinary high-speed steel and high-performance high-speed steel.
1) ordinary high-speed steel ordinary high-speed steel has a certain hardness (62 ~ 67 HRC) and wear resistance, high strength and toughness, cutting steel cutting speed is generally not higher than 50 ~ 60m / min, not suitable for high-speed cutting And hard material cutting. Common grades are W18Cr4V, W6Mo5Cr4V2.
2) high-performance high-speed steel in ordinary high-speed steel to increase the carbon, vanadium content or add some other alloy elements and get heat resistance, higher wear resistance of the new steel. But the overall performance of such steel as ordinary high-speed steel. Commonly used brands are 9W18Cr4V, 9W6Mo5Cr4V2, W6Mo5Cr4V3 and so on.
2.Tungsten Carbide cutting tool
Carbide is a high hardness and melting point of the carbide, with Co, Mo, Ni as a binder sintered powder metallurgy products. Its room temperature hardness of up to 78 ~ 82 HRC, 850 ~ 1000 ℃ high temperature, cutting speed than high-speed steel 4 to 10 times higher. But the impact toughness and bending strength than the high-speed steel is poor, so rarely made the overall tool. In actual use, the carbide blade is often welded or mechanically clamped to the cutter body.
China's current production of cemented carbide is divided into three categories:
1) Class K (YG)
That is, tungsten and cobalt, composed of tungsten carbide and cobalt. This kind of hard alloy toughness is better, but the hardness and wear resistance is poor, suitable for processing cast iron, bronze and other brittle materials. Commonly used grades are: YG8, YG6, YG3, they are manufactured in turn for rough processing, semi-finishing and finishing. Numbers indicate the percentage of Co, YG6 containing 6% Co, the more Co, the better the toughness.
2) P class (YT)
Tungsten and cobalt, composed of tungsten carbide, titanium carbide and cobalt. This type of cemented carbide heat resistance and wear resistance is better, but the impact toughness is poor, suitable for processing steel and other tough materials. Commonly used brands are: YT5, YT15, YT30, etc., where the figures that the percentage of titanium carbide content, the higher the content of titanium carbide, the wear resistance is better, the lower the toughness. These three grades of carbide manufacturing tools are suitable for roughing, semi-finishing and finishing.
3) Class M (YW)
Tungsten and cobalt tantalum and niobium. By adding a small amount of rare metal carbide (TaC or NbC) to the tungsten-cobalt-based cemented carbide. It has the advantages of the first two types of cemented carbide, with its manufacture of both the processing of brittle materials, but also processing tough materials. At the same time can also processing high-temperature alloys, heat-resistant alloys and alloy cast iron and other difficult materials. Common grades are YW1, YW2.
Third, the other tool material profile
Coated cemented carbide
This material is coated with a layer of very thin hard and abrasion resistance by chemical vapor deposition (CVD) or physical vapor deposition (PVD) on hard or alloy substrates or high speed steel substrates Extremely difficult refractory metal compounds are obtained from the tool material. In this way, the tool has both the strength and toughness of the base material and the high wear resistance. Commonly used coating materials are TiC, TiN, Al2O3 and so on. TiC toughness and wear resistance; TiN anti-oxidation, anti-adhesion is good; Al2O3 good heat resistance. The coating material can be selected according to the different needs.
2. Ceramics
Its main component is Al2O3, the blade hardness of up to 78 HRC above, the ability of 1200 ~ 1450 ℃ high temperature, it can withstand higher cutting speed. But the bending strength is low, the impact toughness is poor, easy to chipping. Mainly used for steel, cast iron, high hardness materials and high-precision parts of the finishing.
3. Diamond
Diamond is made of artificial and natural two kinds of cutting tools, most of the artificial diamond, its hardness is extremely high, up to 10000 HV (carbide only 1300 ~ 1800 HV). Its wear resistance is 80 to 120 times the carbide. But the blade is poor, the affinity of the iron family material. Therefore, generally not suitable for processing ferrous metals, mainly used for hard alloy, glass fiber plastic, hard rubber, graphite, ceramics, nonferrous metals and other materials, high-speed finishing.
4. Boron nitride (CNB)
This is a synthetic superhard tool material, its hardness up to 7300 ~ 9000HV, second only to the hardness of the diamond. But the thermal stability is good, can be resistant to 1300 ~ 1500 ℃ high temperature, and iron family of small affinity. But the strength is low, poor weldability. At present mainly used for processing hardened steel, chilled cast iron, high temperature alloys and some difficult to process materials.
In general, the coating cutting tool is mainly four types: coated high speed steel cutting tools, coated carbide cutting tools, and ceramic and superhard materials (diamond or cubic boron nitride) blade on the coating tool. But before the two kinds of coating tools used the most. The coating on the ceramic and superhard material blades is a material with a lower hardness than the substrate. The purpose is to improve the fracture toughness of the blade surface (which can be increased by more than 10%), which can reduce the cutting edge and breakage of the blade and expand the application range.