Applicability of the hottest cutting tool and the

2022-08-23
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Applicability of the tool to the workpiece being processed

material and mechanical conditions applicable to the workpiece being processed

the most important basic point on the tool is the tool tip. The so-called tool tip, by definition, is the intersection of the main and auxiliary cutting edges. The main cutting edge is the intersection of the rake face and the main flank, and the auxiliary cutting edge is the intersection of the rake face and the auxiliary flank; Therefore, the tool tip is actually the intersection of the front knife surface, the main rear knife surface and the auxiliary rear knife surface. In addition to the working state, the point of contact with the workpiece is also on the intersection of the machined surface and the cutting plane (also known as the transition surface) on the workpiece. Therefore, it is actually the convergence point of five faces and two blades

however, the scope of the tool tip in this paper is larger than the above definition. It refers to the above-mentioned concept "tool tip" and the surrounding area adjacent to the "tool tip" on the tool

there are three main factors that constitute the cutting performance of this tool tip: matrix material, surface state, and geometric shape. These three factors and their interaction basically determine the cutting performance of this tool tip

base material: many cutting tools now have coatings, but the base material still plays a very important role in the performance of the tool tip. The coating is usually very thin, and the thickness of most coatings is 3 ~ 25? M (about times the health of human hair), the cutting force and cutting heat it can directly bear are still very limited, and most of the cutting force and cutting heat depend on the base material of the tool. At present, it is mainly used for tool matrix materials, including high-speed steel, tungsten based cemented carbide (usually called cemented carbide), titanium based cemented carbide (usually called cermet by many people), ceramics (oxide ceramics, nitride ceramics, mixed ceramics, etc.), cubic boron nitride (CBN), artificial diamond (PCD, German abbreviation for PKD). At present, cemented carbide is the most commonly used. A flame retardant material

Kenner blade material with cobalt rich layer technology

tungsten based cemented carbide is divided into two categories: tungsten cobalt cemented carbide and tungsten cobalt titanium cemented carbide (see the article on the invention of random brush cemented carbide). The role of cobalt in cemented carbide is the bonding phase. Therefore, the higher the cobalt content of the matrix material, the stronger the impact resistance under the same conditions. Tungsten carbide and titanium carbide are hard phases. The more hard phases, the higher the hardness of the matrix material. Therefore, due to the uniform machining allowance and small impact, cemented carbide with less cobalt can be selected during finishing, and the wear resistance of the tool is also better; While rough machining often faces the situation of uneven allowance, it is advisable to use cemented carbide with high cobalt content, which is of great significance to prevent the sudden edge collapse of the tool during rough machining and give full play to the durability of the tool

a) fine grained cemented carbide kc635m

a series of chain reactions caused by overload

b) ultrafine grained cemented carbide kc637m

fine grained cemented carbide

a technological progress in recent years is the cobalt rich layer technology. The cemented carbide with cobalt rich layer technology is to concentrate the cobalt in the cemented carbide relatively to the surface through a certain process, so that the central part of the cemented carbide has higher hardness, and the surface has stronger toughness because of more cobalt. The impact of chips in cutting mainly occurs on the surface, and the tool with cobalt rich layer can resist such impact better

Another major change in the matrix is fine graining. Under the same or similar chemical composition, particle refinement can significantly improve the strength of cemented carbide. In my opinion, in a way, the strength analysis of cemented carbide is quite similar to that of grinding wheel. The strength of cemented carbide cutting tools is actually composed of two aspects: one is the strength of the hard phase itself, that is, the ability of the hard phase to resist external force damage, and the other is the ability of the bonding phase to protect the hard phase from falling off and displacement. The refined cemented carbide is firstly due to the refinement of hard phase particles, which increases the critical external force for its destruction. For example, it is easy for us to break a piece of chalk, but it is much more difficult to break a piece of chalk

tool coating: some data say that% of all cutting tools are coated tools. The coating improves the cutting performance of all cutting tool base materials: high speed steel (HSS), cemented carbide, cermet, ceramics, superhard materials, etc

why does the tool need coating? Its main functions include the following aspects:

prolonging tool life

anti abrasive wear

anti crescent wear

preventing the formation of debris buildup

improving machining efficiency

usually by improving cutting speed

improving workpiece surface finish

the usual tool coating is divided into chemical coating (CVD) and chemical coating (PVD). Chemical coatings are mainly used for coating titanium carbide (TIC), titanium carbonitride (TiCN), titanium nitride (TIN), aluminum oxide (Al2O3), diamond, etc., while physical coatings can be coated in a wide variety, such as titanium nitride (TIN), titanium carbonitride (TiCN), titanium aluminide (TiAlN), titanium diboride (TiB2), zirconium nitride (ZrN), chromium nitride (CRN), and aluminum titanide (AlTiN) with higher aluminum content than titanium aluminide, Aluminum nitride chromide (AlCrN) with chromium instead of titanium, etc. In addition, there are some such as medium temperature chemical coating (mt-cvd) titanium nitride (TiCN), some plasma technology chemical coating, etc

in recent years, compared with chemical coating, physical coating has developed rapidly, and new coating varieties emerge in endlessly. However, in conventional steel processing, aluminum oxide (Al2O3) coating is still the absolute main force. In terms of current technology, chemical coating is the best choice to obtain Al2O3 film with superior heat resistance, especially stable A-phase Al2O3. At present, all tool manufacturers are committed to thickening the thickness of Al2O3 film on the premise of ensuring the adhesion of the coating, improving the adhesion between the coating and the substrate. 1. The types of common universal material testing machines, improving the interlayer adhesion of multi-layer coatings, improving the contact between the surface coating and the workpiece, and even trying to control the grain growth of the film in the direction selected in advance. In September, 2006, I accompanied Mr. Xin Jiezhi, editor in chief of "tool technology" and Mr. Wang Tianchen, editor in chief of "mechanical workers (cold processing)" to interview Bernard north, vice president of metalworking Solution & server group (mssg), a subsidiary of Kenner metal. Mr. North said that the coating thickness of Kenner metal could reach about 30? m. The coating thickness of the upgraded kc9110, which they officially launched to the market, has reached 24? m。 Due to the breakthrough of coating technology like this, the average cutting speed of kc9110 is increased from about 250m/min five years ago to an average of 320m/min

Yamaguchi tools published their achievements in research and improvement of coating nucleation. Yamaguchi cutting tool believes that the optimized nucleation can significantly improve the wear performance, and these kinds of a-Al2O3 layers are usually composed of relatively small, defect free particles that are free of porosity. The a-Al2O3 layer of the structure shows the best wear resistance. The manufacturing level of A-based Al2O3 coating duratomic "of Shanxin Technology Co., Ltd. has reached the atomic level. As a result, the mechanical and thermal properties exceed the capabilities of all currently produced Al2O3. Compared with traditional Al2O3, duratomic" coating shows higher durability/toughness, excellent heat/wear resistance, chemical inertia, and thus reduces the tendency of chip formation. Shangao's A-based Al2O3 coating duratomic "seems to abandon the law that the outermost layer is covered with tin film to facilitate the identification of wear, so that the a-Al2O3 coating can reach a thicker thickness. According to the information provided by shangao, duratomic" film is indeed very competitive

however, due to the high coating temperature (about 900 ~ 1000 ℃), there will be a brittle between the substrate and the film η At the same time, due to the different thermal expansion coefficients of the substrate and the film, cracks in the coating occur at high temperature. η It has a negative effect on the adhesion of the coating. Although there is no definite evidence to support whether a small number of surface cracks have a negative effect on tool cutting, it is at least a hidden danger of coating surface crack propagation. Therefore, German Hauser Coating Technology Co., Ltd. and Walter have developed the technology of preparing Al2O3 film by physical coating at lower temperature. For this technology, I don't know the metallographic structure and stability of the Al2O3 film, but according to Mr. e Youpeng, the technical director of Walter (Wuxi) Co., Ltd., the performance of the coating in processing stainless steel and difficult to process materials is commendable

as far as I know, in terms of improving the adhesion between the coating and the tool matrix material, the treatment before coating is very important. Good surface treatment can not only improve the adhesion strength of the coating and make the surface smoother, but also help to reduce the generation of chip nodules, micro chipping, and reduce the harm of chip flow. However, some domestic tool manufacturing enterprises do not do serious and careful treatment before coating, which reduces the bonding force between the coating and the tool, so that the original advantages of the coated tool can not be fully brought into play

edge geometry: the geometric parameters of the tool edge are another important factor that determines the performance of the edge. The geometric shape of the tool includes not only the front angle, back angle and chip breaking groove, but also the details of negative chamfer, polishing edge, passivation and polishing. The cutting performance of tools is usually formed by the interaction of matrix, surface technology and edge geometry, so the edge geometry can often make up for some deficiencies of tool matrix material or coating

because the geometry of the tool contains many factors, some relationships are relatively complex, and some people who have not studied it often do not understand the mystery. They think that they can defeat their opponents technically by relying on some new material technology or coating technology, which is too simple to see the problem

ten years ago, shortly after I joined Walt, I encountered a thorny problem with a customer. This customer has a cast steel part that needs to be processed, using a corn milling cutter with a blade. At that time, a German in Walter China made two knife tests, and the blade was blown away. The customer's tool consumption is very attractive to Walter. After Walter made some efforts, the customer's engineer in charge agreed to give Walter another chance, but asked Walter to try the unsuccessful corn milling cutter first, otherwise it is impossible

great pressure

I first analyzed the processing status. The steel casting is processed into a semi closed inner cavity, and one place is the intersection of three planes. The working condition in this place is very bad. There are transition fillets at the intersection of the two inner planes of the steel casting, where three two vertical planes intersect, so the three transition fillets form a local area with a large actual allowance. German technicians cut to this place for two knife tests, and the blade was shattered because it could not bear too much local allowance. Therefore, how to deal with this corner will be my main consideration in choosing tools

I don't think there is much difference between the matrix material and coating selected by German technicians in terms of tool selection

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