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  • Product Name: Reasonable choice of aluminum piston machining cutting tool material
  • Product ID: Reasonable choice of aluminum pi
  • Add time: 2017-06-08
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The advantages and disadvantages of the tool material performance are the basic factors that affect the processing surface quality, cutting efficiency and tool life. Cutting work, the direct work of the cutting work is cutting part of the tool. Tool cutting performance depends largely on the material that makes up the cutting part of the tool, the geometry of the cutting part and the choice of the tool structure and whether the design is reasonable. Cutting processing productivity and tool durability, tool consumption and processing costs, processing accuracy and surface quality of the pros and cons, etc., to a large extent depends on the reasonable choice of tool material. The correct choice of tool material is one of the important contents of the design and selection of the tool.

        Each type of tool material has its specific processing range, can only be applied to a certain workpiece material and cutting speed range. Different tool materials and the same kind of tool processing different parts of the workpiece material life is often a big difference, such as: processing aluminum piston, diamond tool life is YG-type carbide cutting tool life several times to several times; YG-type carbide cutting tool processing silicon content of high, medium and low aluminum alloy life also has a great difference. Therefore, the rational use of cutting tools is the key to successful cutting. Each tool material has its best processing object, that is, there is a reasonable match between the cutting tool and the processing object.

1 tool material should have the performance
1.1 High hardness and abrasion resistance
The hardness is the basic characteristic that the tool material should have. The cutter must cut the chip from the workpiece and its hardness must be greater than the hardness of the workpiece. Cutting metal cutting tool used in the cutting edge hardness, generally more than 60HRC.
Wear resistance is the ability of materials to resist wear and tear. In general, the higher the hardness of the tool material, the better the wear resistance. The higher the hardness (carbide, nitride, etc.) in the organization, the higher the number, the smaller the particles, the more uniform distribution, the better the wear resistance. The abrasion resistance is also related to the chemical composition, strength, microstructure and temperature of the material. The formula can be used to represent the wear resistance of the material WR:
WR = KIC0.5E-0.8H1.43
Where: H - material hardness (GPa). The higher the hardness, the better the wear resistance.
KIC - Fracture toughness of material (MPa · m½). KIC greater, then the material caused by the stress caused by the smaller fracture, the better the wear resistance.
E - elastic modulus of the material (GPa). E is very small, due to abrasive grain caused by microstrain, contribute to lower stress, wear resistance increased.
1.2 sufficient strength and toughness
The tool material must have sufficient strength and toughness to make the tool work under great pressure and in the shock and vibration conditions that often occur during the cutting process without creating chipping and breaking.
1.3 High heat resistance (thermal stability)
Heat resistance is a major indicator of the cutting performance of the tool material. It refers to the tool material in high temperature conditions to maintain a certain hardness, wear resistance, strength and toughness of the performance.
The tool material should also have the ability to resist oxidation at high temperatures and the ability to resist anti-adhesion and anti-diffusion, ie the tool material should have good chemical stability.
1.4 good thermal physical properties and thermal shock resistance
The better the thermal conductivity of the tool material, the easier the cutting heat away from the cutting area, is conducive to reducing the cutting temperature.
When the cutting tool is intermittently cut or the cutting fluid is used, it is often subjected to a large thermal shock (severe temperature change), and the inside of the tool causes cracks. The ability of the tool material to resist thermal shock can be expressed by the thermal shock resistance factor R, which is defined as:
R = λσb (1-μ) / Eα
Where: λ - thermal conductivity;
Σb - tensile strength;
Μ - Poisson ratio
E - elastic modulus;
Α - coefficient of thermal expansion.
Thermal expansion coefficient is small, can reduce the heat distortion; elastic modulus is small, can reduce the heat distortion caused by the magnitude of the alternating stress; is conducive to heat-resistant materials Increased impact performance.
Good thermal impact resistance of the tool material, cutting can be used in cutting fluid.
1.5 good process performance
In order to facilitate the manufacture of the tool, the tool material is required to have good process performance, such as forging performance, heat treatment performance, high temperature plastic deformation performance, grinding performance.
1.6 Economy
Economy is one of the important indicators of tool material, high-quality tool material Although the cost of a single tool is very high, but because of its long life, the cost of each component is not necessarily high. So the choice of tool materials to consider the economic results.
2 tool material
2.1 high speed steel
High-speed steel is a high alloy steel that joins more alloy elements such as tungsten, molybdenum, chromium, vanadium and so on. High-speed steel has a high strength and toughness, and has a certain hardness and wear resistance. Suitable for all kinds of cutting tools. High-speed steel tool manufacturing process is simple, easy to wear sharp cutting edge, so despite the new variety of tool materials continue to appear, high-speed steel cutting tools in metal cutting still accounts for a large proportion. Can process non-ferrous and superalloys. As the high-speed steel with the above performance, the piston processing of the milling riser, milling and groove milling and milling expansion slot cutter, drilling holes with drill bits and other tools are high-speed steel materials.
2.2 Carbide
Carbide is made of powder metallurgy by refractory metal carbides (such as WC, TiC, TaC, NbC, etc.) and metal binders such as Co, Ni, and the like.
As the carbide contains a large number of metal carbides, these carbides have high melting point, high hardness, good chemical stability, good thermal stability and other characteristics, therefore, hard alloy material hardness, wear resistance, heat resistance Sex is high Common hard alloy hardness of 89 ~ 93HRA, higher than the hardness of high-speed steel (83 ~ 86.6HRA) high, at 800 ~ 1000 ℃ fashion can be cut. At 540 ℃, the hard alloy hardness of 82 ~ 87HRA, at 760 ℃, the hardness can still maintain 77 ~ 85HRA. Therefore, the carbide cutting performance is much higher than the high-speed steel, tool durability can be increased several times to several times in the same degree of durability, cutting speed can be increased 4 to 10 times.
At present, the carbide tools used in our company are YG6 and YGX in YG (WC-TiC-Co). YT15 (WC-TiC-Co) in the YT15 and other carbide used for piston roughing, semi-finishing and part of the finishing process.
2.3 Diamond
Diamond is currently known mineral materials in the highest hardness, the best thermal conductivity of the material, with a variety of metal, non-metallic materials, the friction wear only carbide carbide 1/50 ~ 1/800, is the production of cutting tools Ideal material. However, natural single crystal diamond is only used in the production of jewelry and some non-ferrous metals ultra-precision machining. Tool with artificial large particles of single crystal diamond Although De Beers, Sumitomo Electric, etc. have been industrial production, but has not yet entered a large number of applications.
Diamond cutting edge is very sharp (which cut the very small section of the chip is very important), the blade roughness is very small, the friction coefficient is low, the cutting is not easy to produce BUE, processing surface quality. Processing of non-ferrous metals, the surface roughness can reach Ra0.012μm, processing accuracy can reach more than IT5 level.
There are three kinds of diamond tools: natural single crystal diamond tool, the overall artificial polycrystalline diamond tool, diamond composite tool. Natural diamond tools due to the higher cost and other reasons, in the actual production of less. Artificial diamond is the role of alloy catalyst, at high temperature and pressure from the conversion of graphite. Diamond composite blade is in the carbide substrate through high temperature, high pressure and other advanced technology sintering a layer of about 0.5 ~ 1μm thick diamond, this material is made of hard alloy matrix, its mechanical properties, thermal conductivity and expansion coefficient are similar In the hard alloy, the matrix of artificial polycrystalline diamond abrasive in the diamond crystal was irregularly arranged, its hardness and wear resistance in all directions are uniform.
Polycrystalline diamond (PCD) is made by sieving artificial diamond microcrystals under high temperature and high pressure. In the sintering process, due to the addition of additives, diamond crystals formed between the TiC, SiC, Fe, Co and Ni as the main component of the bridge. The hardness and toughness of PCD are greatly improved, the hardness is about 9000HV, the bending strength is O.21 ~ 0.48GPa, and the thermal conductivity is the same as that of the structure. Is 20.9 J / cm · s ° C, and the thermal expansion coefficient is 3.1 × 10 -6 / ° C. Now the use of polycrystalline diamond tools are mostly PCD and carbide substrate sintered complex, that is, in the carbide substrate sintered on a layer of PCD. PCD thickness is generally 0.5mm and 0.8mm, because the bottom of the cemented carbide, welding convenience; and because PCD combined bridge conductivity, making PCD easy to cut into a variety of shapes, made of various tools, the cost is far lower In natural diamond.
Polycrystalline diamond (PCD) can process a variety of non-ferrous metals and wear-resistant high-performance non-metallic materials such as aluminum, copper, magnesium and its alloys, hard alloy, fiber reinforced plastics, metal matrix composites, wood composites The PCD tool material in the diamond grain size is different, the impact on performance is also different, the larger the grain size, the higher the wear resistance. In the similar cutting edge processing capacity, the smaller the grain size, the better the quality of the blade. The PCD with the grain size of 10 ~ 25μm can be used to cut the silicon alloy with the Si content of 12 ~ 18% and the PCD with the grain size of 8 ~ 9μm with the Si content of less than 12% with 500 ~ 1500m / min. Ultra-precision machining, you should use small grain size PCD tool. PCD wear resistance at more than 700 ℃, because its structure contains metal Co, will promote the "reverse reaction" from diamond to graphite. PCD has a good fracture toughness, can be intermittent cutting, can be 2500m / min high-speed end milling Si content of 10% aluminum alloy.
It can realize high precision, high efficiency, high stability and high surface finish of nonmetallic and nonmetallic materials with high hardness, high wear resistance, high thermal conductivity and low friction coefficient of diamond material. In the processing of non-ferrous metals, PCD tool life is a few times or even hundreds of times the carbide cutting tools, aluminum piston is the ideal tool for precision machining. For example: fine wheel piston ring groove, fine boring piston pin hole, fine wheel piston outer circle, fine car piston top and other processes.
2.4 cubic boron nitride
Polycrystalline cubic boron nitride (PCBN) is made by adding the catalyst into a binder with a small amount of binder phase (Co, Ni or TiC, TiN, Al203) at high temperature and high pressure. It has a high hardness (second only to diamond) and heat resistance (1300 to 1500 ° C), excellent chemical stability, much higher thermal stability (up to 1400 ° C) than diamond tools and low thermal conductivity Friction coefficient, but its strength is low. Compared with the diamond, PCBN has the advantage of high thermal stability is much higher, up to 1200 ℃ (diamond 700 ~ 800 ℃), can withstand high cutting speed; another prominent advantage is the chemical inertia, and iron family Metal at 1200 ~ 1300 ℃ does not play a chemical reaction, can be used for processing steel. Therefore, PCBN tool is mainly used for efficient processing of black difficult to process materials.
PCBN tool in addition to the above features, there are the following advantages: ① high hardness, especially suitable for processing only before grinding HRC50 above the hardened steel, HRC35 above the heat-resistant alloy and HRC30 and other tools Difficult to process gray cast iron. ② compared with carbide cutting tools, cutting speed, high-speed and efficient cutting can be achieved. ③ good wear resistance, high tool durability (for the carbide cutting tool 10 to 100 times), can get a better surface quality of the workpiece to achieve the car on behalf of the mill. The disadvantage is that the impact resistance of the PCBN tool is less than that of the cemented carbide. Therefore, it should be noted that the rigidity of the process system should be used to avoid the impact cutting.
PCBN can be made into a whole blade, can also be combined with cemented carbide made of composite blade. PCBN composite blade is in the carbide substrate sintered a 0.5 ~ 1.0mm thick PCBN, its performance both good toughness and high hardness and wear resistance.
PCBN performance is mainly related to CBN particle size, CBN content and binder type, according to its organization can be divided into two categories: one is directly from the CBN grain, CBN content is high (more than 70%), High hardness, suitable for heat-resistant alloy, cast iron and iron sintered metal cutting; the other is based on CBN grain as the main body, through the ceramic binder (mainly TiN, TiC, TiCN, AlN, Al203, etc.) sintering This type of PCBN has a low CBN content (70% or less), low hardness, and is suitable for cutting hardened steel.
In my company, cubic boron nitride tool is used in the cast iron ring piston cast iron ring groove process, but also used in the piston three-dimensional by the mold processing.
2.5 Ceramics
The main advantages of ceramic tool materials are:
Has a high hardness and wear resistance, room temperature hardness of 91 ~ 95HRC;
Has a high heat resistance, high temperature at 1200 ℃ hardness of 80HRC; and high temperature conditions, bending strength, toughness decreased very little;
Has a high chemical stability, ceramic and metal affinity is small, high temperature oxidation resistance, even at the melting temperature does not interact with steel. So the bonding of the tool, diffusion, less oxidation wear;
Have a lower coefficient of friction, the chip is not easy to stick knife, easy to produce BUE.
The disadvantage of ceramic knife is:
Brittleness, low strength and toughness, bending strength only 1/2 ~ 1/5 carbide, so the use of the necessary geometric parameters and cutting the amount must be selected; to avoid the impact load, to prevent chipping and damage; , Ceramic knife thermal conductivity is low, only the carbide 1/2 ~ 1/5, thermal expansion coefficient is 10 to 30% higher than the carbide, thermal shock resistance is poor.
At present, ceramic cutting tools have not been used in the aluminum piston processing process.
3 Summary
The development of tool materials plays a decisive role in the advancement of cutting technology. This paper describes the cutting used in the diamond, polycrystalline cubic boron nitride, ceramics, carbide, high speed steel and other tool materials, the performance and scope of application. The tool damage mechanism is the theoretical basis for the rational selection of the tool material. The matching between the tool material and the workpiece material is the key basis for the selection of the cutting tool material. The tool material can be obtained according to the mechanical, physical and chemical properties of the tool material and the workpiece material. Good cutting effect. The piston in the cutting of the tool material selection was described.
High-speed steel: Piston milling mills, milling and grooving and grooving slot milling cutter, drilling hole with drill bits are high-speed steel materials.
Carbide: YG, YD series of carbide cutting tools are widely used in aluminum piston processing in various processes, especially the piston roughing and semi-finishing process.
Cubic boron nitride: cubic boron nitride tool is used in the cast iron ring piston grinding ring ring ring process. It is also used in the processing of the piston.
Diamond: Diamond tool can use high hardness, high wear resistance, high thermal conductivity and low friction coefficient of diamond material to achieve non-ferrous metal and wear-resistant non-metallic materials, high precision, high efficiency, high stability