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Tritonized tantalum has the highest melting point (3983 ° C), but hafnium carbide is one of the highest melting alloys (3928 ° C). The topic mentioned should be tantalum hafnium carbon alloy (penta tantalum tetrafluoride), Wikipedia referred to the alloy is currently known compounds in the highest melting point of the material. "Encyclopedia Britannica" had included the conclusion, but later changed it to one of the highest melting point of the material.
Hafnium alloy containing metal element hafnium, is the world's highest melting point of the material. It is known that the highest melting point of the material is hafnium compounds: five tantalum tetrafluoride (Ta4HfC5) melting point of 4215 degrees Celsius
Hafnium, metal Hf, atomic number 72, atomic weight 178.49, is a shiny silver gray transition metal. Hafnium has 6 natural stable isotopes: hafnium 174,176,177,178,179,180. Hafnium does not act with dilute hydrochloric acid, dilute sulfuric acid and strong alkali solution, but soluble in hydrofluoric acid and aqua regia. Element name comes from the Latin name of Copenhagen. In 1925 the Swedish chemist He Weixi and the Dutch physicist Kostel with fluorine fluoride salt fractionation method to obtain pure hafnium salt, and reduction with sodium metal to get pure metal hafnium. The content of hafnium in the crust is 0.00045%, which is often associated with zirconium in nature.
The tantalum carbide has the highest melting point (3983 ° C) if the binary compound is alone, but the hafnium carbide is one of the highest melting alloys (3928 ° C). The topic mentioned should be tantalum hafnium carbon alloy, Wikipedia referred to the alloy is currently known compounds in the highest melting point of the material. "Encyclopedia Britannica" had included the conclusion, but later changed it to one of the highest melting point of the material.
As early as 1930, Agte et al. Proposed that the tantalum-hafnium-carbon alloy had the highest melting point (4215 ° C) and was then verified by Andrievskii et al., But there are still references to the highest melting point of the tantalum carbide, The specific values of the melting points of these compounds are also different.
Andrievskii et al. Found that the high melting point of tantalum-hafnium-carbon alloy was caused by changes in the composition of the compound during the experiment. Hafnium in which the role is only to enhance the evaporation of carbon, so that its melting point can be compared with tantalum (with the evaporation of carbon, the stoichiometric amount of each component close to the tantalum carbide), and tantalum The high melting point originates from the formation of a stable metal sublattice structure.
Lavrentyev et al. Argue that the Ta-Hf-C solid solution has a high melting point due to the strong chemical bond effect of HfC and TaC (heterogeneous 5d and 2p). Osama et al. Also refer to this interpretation, and according to the literature, it is suggested that HfC and TaC can form a uniform single-phase cubic crystal structure, which improves the stability of its structure.
The above mentioned alloy has a high melting point of the reasons should be a combination of multi-factor role, I have not seen the literature has a specific conclusion. The difference in the melting point values mentioned in the different literatures may be due to changes in compound composition, structure, etc. that are difficult to avoid during the high temperature melting point measurement, and the lack of measurement means.
Application of NC Tool in Precision Cutting
Precision and ultra-precision machining has become a key technology in the international competition, many modern technology products need high-precision manufacturing, such as the development of cutting-edge technology, the development of national defense industry, the development of microelectronics industry and so require precision and ultra-precision machining equipment.
At present, in the industrialized countries, the general factory can be stable grasp of the processing accuracy is 1 um, and accordingly, usually the processing accuracy of 0.1 ~ 1 um, processing surface roughness between Ra 0.02 ~ 0.1 um processing method called For precision machining, and the processing accuracy is higher than 0.1 um, the processing surface roughness is less than Ra 0.01 um processing method known as ultra-precision machining. Ultra-precision cutting is a kind of metal cutting, natural obedience to the general rule of metal cutting, but it also has a lot of special rules, which is due to the special physical and chemical properties of diamond tools and cutting layer caused by very thin.
Ultra-precision machining is a wide range of new technologies, its processing accuracy and surface quality are used by the ultra-precision machine tools, diamond tools, cutting technology, measurement and error compensation technology, the operator's technical level, the environment Support conditions and other factors combined effect of the results.
- 1. Current research status and application areas Common symbol Meaning:
- PCD - high temperature and high pressure synthesis of polycrystalline diamond;
- CVD diamond and PCVD diamond - chemical vapor deposition (low pressure) polycrystalline diamond (in the form of a coating film and a free brazeable substrateless film);
- CBN - cubic boron nitride;
- PCBN - polycrystalline cubic boron nitride;
- CVDCBN - Chemical Vapor Deposition of Cubic Boron Nitride.
Superhard materials refer to diamond and cubic boron nitride, and their hardness is several times higher than that of other tool materials. Diamond is the hardest material in nature, CBN hardness after diamond, in recent years, the rapid development of superhard tool materials.
(PCD), made of graphite as raw material, made by high temperature and high pressure; artificial polycrystalline diamond composite sheet (PCD / CC), with carbide (carbide) As the substrate, the surface of 0.5 mm thick polycrystalline diamond, the same method and PCD manufacturing methods. Diamond film coating tool (CD), with CVD process, the surface of the tool coated with a thickness of about 10 ~ 25 um film. Diamond thick film cutter (TFD), also using CVD process, in another substrate coated with more than 0.2 mm thick film, and then cut into a certain size of the thick film, and then welded on the carbide blade used.
PCD tool has a very high degree of durability (more than a few times higher than the carbide cutting tool life), the stability of the size of processing accuracy (Machinable thousands to tens of thousands), and good surface roughness. The main processing objects are non-ferrous metals, non-metallic materials and wood materials containing Al2O3, such as copper, aluminum and other non-ferrous metals and their alloys, ceramics, all kinds of fiber and particle reinforced composite materials, plastics, rubber, graphite, glass, wood , But also for the above materials for ultra-precision processing, but avoid processing steel and other iron family metals. Made in China
The main varieties are: PCD woodworking saw blade and trimming knife, PCD indexing blade, PCD piston series cutter, PCD wheel cutter, PCD commutator tool, PCD case, jewelry tool, all kinds of PCD welding tool, boring knife The
PCD, PCBN and synthetic single crystal diamond are synthesized at high temperature and high pressure, while CVD diamond is prepared at low pressure. The mixture of the carbon-based gas and the hydrogen is decomposed at high temperature and below atmospheric pressure to form diamond deposited on the substrate. The diamond is diamond, which does not require a metal catalyst, so it is thermally stable. The diamond diamond is different from the grain size and structure. CVD diamond does not require metal catalyst. Close to natural diamond. According to different applications need to choose a different CVD deposition process can be synthesized grain size and surface morphology of the diamond is very different. Due to the variety of requirements for tool performance, it is possible to have a variety of different grain sizes of CVD to meet the needs of various applications. In fact, there are two forms of CVD diamond tools, the first is in the appropriate substrate deposition thickness of less than 30 um thin layer (film), such as ISO blade and twist drill edge is two typical thin coating. The second is to deposit a substrateless diamond layer (thick film) with a thickness of 1 mm and braze it on the substrate if desired.
Diamond tools are: turning tools, milling cutter, boring knife and other varieties, more than 80% for the automotive and motorcycle industry, the other is used for household appliances, general machinery and other fields. Diamond tools in the automotive and motorcycle industry is mainly used for processing engine piston skirt, pin hole, cylinder block, gearbox, carburetor and so on. Because these components contain high silicon content (more than 10%), and most of the use of high-volume production line, the tool life requirements are higher, hard alloy tool is difficult, and diamond tool durability is a carbide tool Of the 10 to 50 times, can guarantee the dimensional stability of parts, and can greatly improve the cutting speed, processing efficiency and surface quality of the workpiece.
The first half of 2017 abrasive abrasive exports of 1.1 billion US dollars an increase of 15.2%
Since the first half of 2017, in the market demand gradually picked up under the support of the machine tool market and industry operations show warmer and stabilize the situation. According to the National Bureau of Statistics, customs import and export and industry focus on business statistics, the first half of the machine tool market and the overall situation of the operation of a brief analysis and introduction.
First, the overall situation
Since the second half of 2016, in the market rebound and pre-transformation and upgrading work under the influence of the machine tool industry, the overall operation of the resumption of growth. According to the National Bureau of Statistics data, the first half of 2017, the industry's main income of 505.8 billion yuan, an increase of 12.2%; total profit of 31.5 billion yuan, an increase of 23.6%.
According to the Association of the domestic machine tool market consumption, the first half of 2017 metal processing machine tools (including metal cutting machine tools and metal forming machine) consumption of 13.6 billion US dollars, an increase of 3.8%. Among them, the metal cutting machine tool consumption of 9 billion US dollars, down 2.2%; metal forming machine tool consumption of 4.6 billion US dollars, an increase of 17.9%. The first half of 2017 tools (including cutting tools and measuring instruments) consumption of 2.5 billion US dollars, an increase of 25.0%. Overall, the first half of the machine tool consumption showed a slight increase in the state, metal cutting machine tool consumption fell slightly mainly due to the decline in the RMB exchange rate, the total domestic output flat, export growth and import decline and other factors together.
Domestic machine tool production showed year-on-year growth. The first half of 2017 metal machine tool output of 11.3 billion US dollars, an increase of 7.4%. Among them, the metal cutting machine tool output of 6.9 billion US dollars, flat year on year; metal forming machine tool output 4.4 billion US dollars, an increase of 21.5%. The first half of 2091 tool output of 2.9 billion US dollars, an increase of 20.8%. Metal forming machine tools and tool products in the field of production showed a significant recove
Machine tool industry in the field of foreign trade situation is showing a steady trend, the first half of 2017 machine tool exports rebounded significantly, exports 5.4 billion, an increase of 10.3%; machine tool imports to achieve growth "from negative to positive", import The amount of 6.9 billion US dollars, an increase of 5.4%. Trade deficit of $ 1.5 billion, down 8.3%.
Exports of major segments of products: Exports of metalworking machines amounted to $ 1.5 billion, an increase of 8.5% over the same period last year. Among them, the metal cutting machine tool exports 1 billion US dollars, an increase of 8.9%; metal forming machine tool exports 500 million US dollars, an increase of 7.8%. Cutting tool exports 1.2 billion US dollars, an increase of 6.5%; abrasive abrasive 1.1 billion US dollars, an increase of 15.2%.
Main segmentation of product areas: imports of metal processing machine tools 3.8 billion, down 3.4%. Among them, the metal cutting machine tool imports 3.1 billion US dollars, down 4.0%; metal forming machine tool imports 700 million US dollars, down 0.6%. Cutting tool imports amounted to 800 million US dollars, an increase of 19.1%. China Machine Tool Industry Association in the industry focus on key enterprises and major foreign enterprises in China, the first half of 2017 machine tool industry leader in the questionnaire survey, the questionnaire returned to 136, the relevant enterprises in 2016 product sales of about 84.4 billion yuan The In the first half of 2017, China's machine tool industry boom index was 62.5% in the first half of 2017, up from 8.66% at the end of 2016, and continued to maintain the trend of expansion in the first half of 2017.
Second, the need to focus on the issues and recommendations
In the second half of 2017, the pressure of economic operation was still large, and the uncertainty of investment volatility and market demand would have a direct impact on the operation of machine tool companies in the second half of the year. Through the survey of foreign-funded enterprises in the field of machine tools, the outstanding problems encountered in the current business operations are mainly concentrated in the following nine aspects: competition of similar products (14.4%), lack of market demand (13.4%), operating costs (Accounting for 9.4%), insufficient capacity (7.8%), insufficient international market development (5.4%), market demand upgrade (5.2%), human resources (9.9%), %) And market development (3.5%). From the above data, 41.9% of the market-related issues related to the development of enterprises, accounting for 20.1% of the operating and cost-related activities and 18.9% of the human resources.
At the same time, the questionnaire also reflects the enterprises in response to the above problems taken by the corresponding measures. From the distribution of these measures, with the recent market and industry to run some of the trend characteristics are basically the same. The main measures taken by the enterprises are the following six aspects: control costs (22.6%), strengthening R & D and technological innovation (17.9%), strengthening market segmentation (16.0%), introducing and developing new products (12.4 %), Downsizing (8.1%) and expanding production capacity (7.9%).
In summary, this year's machine tool consumer market and industrial operation is expected, compared with the end of last year's forecast results have increased. At the same time, taking into account the second half of the economic environment and changes in market demand uncertainty, is expected in 2017 machine tool spending will show a slight increase or flat state.
Carbide roll minimum rolling thickness
The minimum sheet thickness that may be rolled when the tungsten carbide roll is elastically flattened. In a certain rolling mill rolling a certain product, with the gradual thinning of the strip, press more and more difficult. When the strip is thin to a certain extent, no matter how tightly the screw is pressed or the pressure under the hydraulic pressure is increased, it is impossible to make the product thinner due to the elastic flattening of the roll, regardless of the number of repeated rolls. This limit thickness is called the minimum rolling thickness.
In the rolling, the rolling material interacts with the roll, and the rolling material is deformed under the action of the carbide roll, and the reaction force of the rolling mill and the roll is elastically deformed. Of course, the rolling is also accompanied by a small elastic deformation, through the roll after a small amount of elastic deformation to restore, increasing the thickness of the workpiece. As shown in the figure, the rolling of the thickness H is reduced by Δh in the roll, but the roll is reduced by Δh1 due to the elastic deformation of the roll. At the same time, after the roll is rolled, the rolling reduction is reduced by Δh2 due to the elastic deformation recovery. As a result, the actual reduction of the workpiece Δh = Δh total - Δh1 - Δh2 When Δh total = Δh1 + Δh2 At that time, the roll will not be depressed by the roll, when the thickness of the roll is the minimum rolling thickness. (M.D. Stone), Roberts (W. L. Roberts), Ford - H.Ford (H.Ford) - (J.M.Al-exander) and others have made the theoretical study on the minimum rolling thickness formula The
According to Stone's formula, the minimum rolling thickness hmin = 3.58DμK / D
Where D is the working roll diameter; μ is the friction coefficient; K is the metal plane deformation resistance; E is the mechanical elastic modulus. In order to roll out the thinner strip, it is necessary to reduce the roll diameter of the work roll, use efficient process lubricant (see plastic processing process lubrication), reduce the deformation resistance of the metal, increase the elastic modulus of the roll, The elasticity of the small roll is flattened. Modern 20-roll mill with a diameter of up to 10mm tungsten carbide roll, rolling thickness of less than 0.001mm very thin strip.
Engineering, generally can be determined according to the following formula roll diameter and finished strip thickness ratio of the relationship between D ≤ 1000h When increasing the intermediate annealing and rolling times D ≤ 2000h The use of asynchronous rolling technology can break through the above minimum rolling thickness limit, the principle is different from the general rolling theory.