Dry cutting tool has higher requirements, such as structural materials, cutting tool and cutting tool coatings.
In traditional machining, cutting fluid wet cutting occupies an important position, but there are many disadvantages. For example, need to spend a lot of money to maintain a large cutting fluid system, also need to regularly add preservatives, replacing the cutting fluid, thus increasing the cost of many of the costs, the proportion accounted for 15% of total cost of production to 17%, while the cutting tool cost usually accounts for 2% of the total cost to 5%. Because of the harmful substances in cutting fluid, cause harm to the health of workers, to pollute the environment. Therefore, its use has brought more and more problems. From these aspects, the dry cutting has more advantage.
Dry cutting tool should be more excellent high temperature performance (hardness) and wear resistance, cutting tool material at present, such as the new carbide, ceramics, CBN and PCBN have high temperature resistant enough wear resistance, can be used in dry cutting conditions. Moreover, the application of modern cutting tool materials for high speed machining is more suitable for dry cutting. Like CBN and advanced carbide material grades, especially the tool material coating protection, without the use of cutting fluid in high speed and high temperature actually cut more efficiency and life.
The demand on cutting tool for dry cutting
Must have excellent hardness and wear resistance of the tool cutting the stem, with high temperature can effectively withstand the cutting process; the low friction coefficient, to rise can reduce the friction between tool and chip and workpiece surface inhibition of cutting temperature; high strength and impact resistance performance, can withstand the cutting force at more and more poor cutting conditions. In order to realize the dry cutting, tool materials with high heat resistance (hot hardness and wear resistance is a must). The cubic boron nitride (CBN), polycrystalline cubic boron nitride (PCBN), diamond, polycrystalline diamond (PCD) (A12O3, Si3N4), ceramic, metal ceramic (CERAMIC), ultra-fine Grain Cemented Carbide and coated carbide tool materials have been widely used in dry cutting. Iscar development in the past two years many can be used for dry cutting tool materials: IB90 and IB85, CBN content as high as 85% and 90%, the blade wear resistance and high toughness, can deal with intermittent cutting vibrations, recommend high speed cutting and hardened steel for cast iron for interrupted cutting and rough machining. Low CBN content type, IB55, IB50, CBN content is 50% and 55%, more suitable for semi finish machining and finish machining. IB10H belongs to the CBN ultra-fine grain, wear resistance and toughness are higher, used for high speed continuous cutting, can obtain a high surface quality; IB20H fine grain and medium grain CBN, for continuous - mild intermittent cutting; and IB10HC, IB25HC and IB25HA coated TiN, Ti (C, N, O) and Ti (C, N), applied to the corresponding occasions.
The cutting tool coating special
The cutting tool coating treatment, is an important way to improve the performance of the cutting tools. In a tough coating on the surface of a cutter body heat and wear resistance are very high material, so that in the cutting process in cutting tool between the chip and the increase of a heat insulation barrier, prevent heat transfer to the substrate to reduce tool wear and heat generation, and reduce the coefficient of friction between the tool / workpiece surface, play some lubrication function, so the most suitable for dry cutting tool coatings. Such as A12O3, is a basic component of alumina based ceramics, A12O3 coating has good mechanical properties, excellent hardness and chemical stability, therefore, A12O3 blade coating has good ability of crater wear resistance, low thermal conductivity, with the increase of temperature the thermal conductivity is reduced, this characteristic in machining, can block cutting heat to the tool cutting edge, prevent the heated plastic deformation caused by the sudden failure, ISCA medium temperature chemical coating (MTCVD) alpha -TEC, optimization has good oxidation stability and high thermal stability in A12O3 α phase, improved A12O3 multilayer coatings
In general, the coating can be divided into two categories: one category is the hard coating, which is coated with TiN, TiC, TiCN, TiA1N, A12O3, CBN, diamond, diamond-like DLC, nanometer material coating on the surface, this kind of coating the coating has high hardness, good wear resistance; another kind is the "soft" coating, this kind of coating chalcogenide M0S2 or WS2 or TaS2 antifriction coating, significantly reduce the friction coefficient, the coated tool called "self lubricating cutter", this kind of coating tools for lubrication no cutting fluid in a certain extent, resist the cutting temperature rise, it is suitable for dry cutting. IC908, IC907, IC903 ISCA belongs to the hard coating, they use ultra-fine grain cemented carbide has good resistance to mechanical impact and thermal shock performance as the base, through the PVD coating process has lower friction coefficient and high temperature resistant material TiAlN, oxidation temperature is high, the cutting will produce TiAlN film, have better oxidation resistance, oxidation temperature is 700 ℃ ~ 800 ℃, oxidation temperature is higher than that of TiC, TiN coating. TiAlN in the high temperature than TiN high hardness, good thermal stability, the high temperature oxidation. Friction can improve the tool and workpiece / chip, reducing heat generation, in addition, the thermal conductivity of TiAlN coating rate is also lower than the TiN coating, so as to heat insulation effect, so that the tool can withstand higher temperature in dry cutting. PVD-TiAlN coating, hardness and TiCN, TiN, temperature and thermal stability than TiCN and TiN, at 1450 ℃. The TiAlN coating with A1 content, the higher hardness, resistance to high temperature fracture is stronger, have high hardness and abrasion resistance, and the oxidation temperature.
In recent years, iscar by ultrathin TiN and TiAlN on alternately coated tool, cutting tool coated with strong adhesion, high heat resistance and good abrasion resistance and other characteristics, the advantages of TiN, TiAlN accumulation and TiNC coating, and then use the coating processing technology of SUMO-TEC, further improve the toughness and wear resistance, reduce the surface friction coefficient, so that the cutting zone temperature lower, chipping resistance and anti bue better, so as to obtain more reliable and durable life of cutting tool in machining the vast majority of the processed material, the durability of the blade increases 20% ~ 280%.
Special design of cutter structure
In the aspect of tool geometry, dry cutting tool design should strive to follow the "low temperature" the principle of design, tool structure design must consider the machining process of heat as little as possible, that is to say the tool structure should strive to achieve and low friction and low cutting force. The tool can not usually adapted to dry cutting, therefore, dry cutting tool geometry parameters should be optimized, requested that the tool has larger anterior angle, and with the shape of cutting edge fitting, such as iscar various milling inserts -PDR and -PDR? HM groove, the zero diamond blade and double positive rake angle design, i.e. reduce the cutting force and enhance the blade intensity and volume heat performance.
In order to reduce the cutting heat, iscar in the car blade, blade groove and milling cutter rake face is set to strengthen edge, can be formed in squamous cutting surface contact area, the contact area of tool and chip is greatly reduced, and most of the heat is chipping away, cutting temperature than ordinary blade is greatly reduced, but also increase the shear angle the tool life, improve. In addition, consider the maximum lubricity tool surface, prevent bue, iscar first knife body were hard nickel transition layer and transition layer containing Ti, greatly improves the surface of the knife body hardness and lubrication. The flute profile tool also need to consider the "low temperature" design principle, ensures low friction chip flow in order to reduce the cutting tool and cutting friction between chip, the chip is convenient, reduce the heat accumulation, therefore, in the milling cutter and knife trough iscar areas using vertical installing structure blade, avoid chip and chip space hampered row increases the knife body.
Dry cutting future
Dry machining is not only related to the cutting tool material, cutting tool coatings, but also relates to every tool geometry, tool structure, machine tools, cutting, machining etc.. This requires development of new tool materials, and pay attention to prevent the diffusion bonding, the tool material and workpiece with a reasonable tool material and workpiece and dry cutting.
Study of new tool materials are mainly concentrated in the super hard tool materials, metal ceramic, ceramic, coating, excellent performance of high-speed steel and hard alloy etc.. ISCA with particular emphasis on R & D of coated cutting tools, because the coated tool combining high hardness and wear resistance, high heat resistance, high toughness, high anti adhesive properties, high chemical stability and low coefficient of friction, the development of dry cutting technology is highly dependent on the cutting tool coating technology.
In addition to thermal stability, toughness, hardness of cutting tool material, there are different tool materials in dry cutting adaptability, different materials to be machined in dry cutting function, characteristics, performance etc.. Tool geometry design, rationally determine the blade shape and geometry parameters, to give full play to the role of cutting tools in dry cutting performance is very important, so the blade shape iscar also R & D intensity has higher and more stable blade clamping way; consider the distribution adjustment of the cutter body quality reasonable, makes the knife expansion uniformity etc.. The geometric parameters, we emphasize the small cutting force low cutting temperature principle.
Dry cutting is a concrete manifestation of the environmental clean production concept, it not only reduces the production cost, promote the tool technology progress, but also brought a new green manufacturing technology, is the manufacturing industry will be the pursuit of the goal.
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