Scholars at home and abroad have carried out preliminary analysis and Research on the crack formation and propagation, chip shape and size, and the interaction between tool and workpiece material in graphite ordinary cutting and high-speed machining. Das believes that when graphite turning is carried out with positive rake tool, a large chip will be generated first, and an arc groove will be left on the surface of the workpiece to be processed, and then it will be removed in the form of small chips; When the negative rake tool is used for machining, due to the synchronous expansion of multiple sliding surfaces, the chip produced is mainly small particle chip.
When studying the turning process and characteristics of carbon graphite materials, it is pointed out that the cutting tools do not simply peel off the surface of graphite blank, but “cut and peel” or “crush and peel” the particles on the cutting surface according to the properties of cutting tools and blank, the cutting factors of cutting tools and the sharpness of cutting edge. The cutting force in the cutting process of carbon graphite materials is irregular Intermittent high-frequency impact force; In addition, there is considerable friction between carbon particles and cutting edge in high-speed relative motion. It is considered that the cutting process of graphite material is mainly that the surface of the processed material is cracked (crushed) by the extrusion force of the tool edge, which is actually the friction between the edge 1:3 and the processed material. It is mentioned that the chip powder particles in stone burning ink turning are concave convex and broken. The shape of the new grinding tool chip is seriously irregular, the surface is multi angular, and the size is tens to hundreds of microns. With the increase of tool wear, the average diameter of the chip particles is approximately spherical, and the concavity and convexity of the powder surface decreases by 14.
Carbon element is one of the most closely related and important elements in nature. It has the characteristics of multiple electronic orbits of SP, SP2 and SP3 hybrid. In addition, the anisotropy of SP2 leads to the anisotropy of crystals and other permutations. Therefore, carbon materials with carbon as the only constituent element have various properties, and new carbon is consistent. New carbon materials have been found and artificially made. In fact, no element can be used as a single element to form so many substances with completely different structures and properties, such as three-dimensional diamond crystals, two-dimensional graphite lamellae, one-dimensional carbene and carbon nanotubes, zero dimensional fullerene molecules and so on.
Carbon industry belongs to the basic raw material industry and is an indispensable basic material in the development of national economy. Although China is now a large country in the production and export of carbon products, it is difficult for high-end products to have a voice in the international market. There is still a gap between China and a carbon power in terms of high-tech carbon products and special carbon products in some fields. The following is an analysis of the development status of carbon materials.
The development status of carbon materials shows that China’s economic growth has been in an upward trend. Under this environment, the carbon industry has been promoted to develop rapidly and gradually become the main economic pillar industry in China. However, at this stage, the development status of carbon materials has encountered a bottleneck period, and it is urgent to restore the power of industrial development as soon as possible.
If you have any needs about China Graphite Electrodes ,please contact us!
Due to the short supply of carbon products and high profit margin, the economic benefits of carbon enterprises are generally optimistic, Carbon products once had “black gold” “Carbon enterprises have sprung up all over the country and have grown rapidly to nearly 400. However, there are only more than 40 carbon enterprises with supporting processes and large-scale enterprises. However, there are only two of the more than 40 carbon enterprises with leading products of more than 50000 tons. It can be seen from the development status of carbon materials that there are many small and medium-sized enterprises in the whole carbon industry, which are small and difficult to form effective competitiveness. Take the leading product graphite electrode as an example, The production of nearly 400 carbon enterprises in China reached 450000 tons, more than double the demand. In 2002, the graphite electrode production of 33 carbon enterprises counted was 223700 tons, and there were enterprises not counted that produced about 20000-30000 tons of graphite electrodes and about 20000 tons of imported electrodes. The total resources of domestic production and imported graphite electrodes were 270000 tons, while the apparent consumption of graphite electrodes in 2002 was about 180000 tons, which was far greater than the demand. Due to the contradiction between supply and demand, the market competition of carbon enterprises is becoming more and more fierce, and even the situation of competitive price reduction and disorderly competition appears. The market is difficult to control, which makes the overall benefits of the carbon industry suffer great losses.
In order to meet the market demand, China’s carbon enterprises have made great efforts in recent years to adjust the product structure. In 1997, China produced 5500 tons of ultra-high power graphite electrodes, accounting for 2.5% of the total graphite electrodes; In 2002, 23400 tons of ultra-high power graphite electrodes were produced, accounting for 10.4% of the total graphite electrodes, an increase of 7.9 percentage points over 1997. In 1997, China produced 61000 tons of high-power graphite electrodes, accounting for 28% of the total output of graphite electrodes; In 2002, 85100 tons of China graphite electrodes were produced, accounting for 38% of the total output of graphite electrodes, an increase of 10 percentage points over 1997. Although the product structure adjustment of China’s carbon industry is fast, the large-size ultra-high power graphite electrode required by the market still needs to be imported. Perhaps, China’s carbon industry should continue to accelerate the pace of product structure adjustment and strive to produce large-scale ultra-high-power graphite electrodes to meet the needs of domestic large electric furnace production and reduce imports. If enterprises do not adapt to the market, it is difficult for them to survive and develop. China’s carbon enterprises should speed up the pace of adapting to the market, continuously enhance their strength and actively participate in market competition. This is the way for the development of carbon materials in China.
1. High temperature resistance: graphite is one of the most high temperature resistant materials known at present. Its melting point is 3850 ℃± 50 ℃ and its boiling point is 4250 ℃. Under 7000 ℃ ultra-high temperature arc for 10s, the graphite loss is the smallest, and the graphite loss is 0.8% by weight. It can be seen that the high temperature resistance of graphite is very prominent.
2. Special thermal shock resistance: graphite has good thermal shock resistance, that is, when the temperature changes suddenly, the thermal expansion coefficient is small, so it has good thermal stability and will not produce cracks when the temperature changes rapidly.
3. Thermal conductivity and conductivity: graphite has good thermal conductivity and conductivity. Compared with ordinary materials, its thermal conductivity is quite high. It is 4 times higher than stainless steel, 2 times higher than carbon steel and 100 times higher than ordinary non-metal.
4. Lubricity: the lubricity of graphite is similar to that of molybdenum disulfide, and the friction coefficient is less than 0.1. Its lubricity varies with the scale size. The larger the scale, the smaller the friction coefficient, and the better the lubricity.
5. Chemical stability: graphite has good chemical stability at room temperature and can resist acid, alkali and organic solvent corrosion.
When formulating high-speed machining process, the following aspects shall be comprehensively considered:
(1) Cutting parameters;
(2) Tool feeding mode;
(3) Tool geometry;
(4) The number of cutting edges and the overhang of the cutter bar;
(5) Cooling conditions;
(6) Clamping mode between tool bar and machine tool;
(7) Blade clamping mode, etc.
At present, scholars in Japan and Germany have carried out some relevant research on the optimization of cutting parameters and tool geometric angle for high-speed milling and high-speed turning of graphite with large diameter milling cutter (≯ 12 mm). The results show that:
(1) In terms of tool wear, the cutting speed increases and the wear area decreases; The feed rate per tooth of milling cutter increases, and the tool wear increases; When the rake angle increases, the crater depth KT on the rake face decreases, but the crater width KB on the rake face changes little; The wear of the flank decreases with the increase of the back angle; The smaller the graphite grain size is, the longer the tool life is; The tool life is roughly proportional to the bending strength and shore hardness.
(2) In terms of cutting force, the cutting force of graphite material is only 10% of that of aluminum, copper and other ductile metals. When turning graphite electrode material, the cutting force and its fluctuation amplitude increase with the increase of feed rate: the cutting force decreases with the increase of tool rake angle, and when the rake angle increases to 60C, the change of cutting force is no longer obvious: the higher the bending resistance of the material, the greater the cutting force; The influence of cutting speed of brittle materials on cutting force is generally negligible.
(3) In terms of machined surface quality, increasing cutting speed and cutting feed rate can reduce the surface quality; The tool rake angle increases and the surface quality decreases. Graphite rough machining aims at cutting the largest amount of materials in the shortest time, and can adopt profiling milling or contour milling. The advantages and disadvantages of rough machining process depend on the NC programming according to the tool surface contour curve function, so that fast and simple milling can be carried out along the envelope contour. When finishing, the influence of milling direction on machining accuracy and surface quality should be considered in the treatment of bending angle. Pull milling and drill milling will occur when milling along the surface, and the deformation of the tool will lead to the deviation of the workpiece contour. The best strategy for milling along the plane contour is the combination of back milling and plane contour milling. The main problem of prismatic machining is the fracture of local corners of the die, and the action direction of cutting force should be mainly considered.
At present, the process parameters used in the high-speed machining strategy commonly used by China’s graphite electrode high-speed machining enterprises mainly depend on the experience of programmers and are selected according to the general principles, but there has been no theoretical and Application Research on the programming strategy and process parameter optimization of special structural parts.
May day, also known as international labor day and labor day, is the labor day of most countries in the world. The festival originated from the workers’ strike in Chicago. In order to commemorate the great workers’ movement, the second international founding conference in 1889 announced that may 1 of each year would be designated as international labor day. The Administrative Council of the Central People’s Government of China made a decision in December 1949 to designate May 1 as labor day.
In April 18th, covid-19, Pang Xinghuo, deputy director of the Beijing Center for Disease Control and prevention and member of the national New Coronavirus pneumonia expert group, introduced the news release of the new crown pneumonia prevention and control work in Beijing. “The May Day” holiday has a large number of staff and lots of people, which has increased the risk of transmission and infection of infectious diseases. It reminds the general public that it is not necessary to leave Beijing, do not travel to high-risk areas, advocate local festivals and do not participate in mass gatherings.
On April 20, Yu ChuanHua, Professor of epidemiology and health statistics at Wuhan University, also told reporters that the May Day holiday was originally a day for everyone to go out and play. However, recently, the cross transmission between regions has been obvious. In some regions, the infection base is at a high level, and the risk of community transmission is still high. The situation of national dynamic clearing and prevention and control is severe and complex. During the May Day holiday, it should be advocated to celebrate the Festival locally and not organize or participate in large-scale gatherings, dinners and other gathering activities.
If you have any needs about China Graphite Electrodes ,please contact us!
As one of the four main materials of lithium-ion battery, the specific capacity and working voltage of the negative electrode material directly determine the energy density and working voltage of the battery. Although silicon materials begin to move towards industrialization, the current mainstream negative electrode material is still graphite electrode materials, which has a low lithium intercalation potential in the reaction process. At the same time, the lithium intercalation compounds generated replace the metal lithium negative electrode, so as to avoid the deposition of metal lithium dendrites, Therefore, the safety can be significantly improved. As the last theme of the four main materials of lithium battery, we will have a systematic and intuitive understanding of graphite materials from the aspects of basic knowledge, production process, test methods and failure mode analysis, and make a brief introduction to the basic knowledge of graphite materials.
Graphite materials are mainly divided into artificial graphite and natural graphite. Artificial graphite can be divided into MCMB (mesophase carbon microsphere), soft carbon and hard carbon according to different processing technology. Ideal graphite has layered structure, each plane is similar to benzene ring, and the layers are connected by large π bond; It has 2H type hexagonal crystal system and 3R type rhombohedral crystal system.
For ideal graphite, its theoretical capacity is 372mah / g, but in the actual battery design process, the negative electrode will be excessive by 5% – 10%. At the same time, SEI film is formed during the first charging process to protect the negative electrode surface and prevent the further reaction between electrolyte and negative electrode, and the quality of this film will directly affect the performance of the battery.
Carbon materials are inorganic non-metallic materials dominated by carbon. Carbon materials are basically composed of non graphitic carbon, while graphite materials are mainly composed of graphitic carbon. Graphite is divided into natural graphite and artificial graphite.
Graphite material is mainly composed of polycrystalline graphite. Graphite is a kind of layered crystal with hexagonal plane grid between carbon atoms. Although graphite is an inorganic non-metallic material, it is called semi metal because of its good thermoelectric conductivity. Graphite has higher thermoelectric conductivity than some metals, far lower coefficient of thermal expansion and high chemical stability than metals, which makes it of great value in engineering application. Graphite is chemically inert in non oxidizing medium and has good corrosion resistance. Except for strong acid and strong oxidizing medium, graphite is not corroded by other acid and alkali salts and does not react with any organic compounds.
Graphite material is also a kind of high-temperature resistant material. At high temperature, graphite will not melt. The gasification temperature is very high, but 3350 18 begins to sublimate into gas under normal pressure. The strength of general materials decreases gradually at high temperature, while that of graphite is within 2500 ‘C. its strength increases with the increase of temperature. Above 2000 ℃, its strength is twice that of normal temperature. Graphite material also has excellent thermal shock resistance. Therefore, graphite material has its unique advantages as a high-temperature material.
Because graphite material has the advantages of high temperature strength, conductive heat transfer, thermal shock resistance, corrosion resistance and good lubricity, it has become an indispensable structural material, high temperature material, conductive material, anti-wear material and functional material in the development of national economy. At present, graphite materials have been widely used in metallurgy, chemical industry, electronics, electrical appliances, machinery, nuclear energy and aerospace industry. They can be used as graphite electrodes, electrolytic anodes, molds and high-temperature bearings; Surface coating as neutron deceleration material and nuclear fuel in atomic nuclear reactor; In the field of aerospace, graphite material can be used in satellite antenna, space shuttle shell, rocket generator nozzle throat liner and other parts.
Graphite material is mainly composed of polycrystalline graphite, graphite is a kind of multilayered crystal with hexagonal annular planar grids between carbon atoms. Although graphite belongs to inorganic non-metallic materials, it is called semi metal because of its good thermal and electrical conductivity. Graphite has a higher heat than some metals, the electrical conductivity, at the same time, has a low thermal expansion coefficient, high melting point and chemical stability, which makes it important in engineering application. Graphite is chemically inert in a non oxidizing medium, With good corrosion resistance, in addition to strong acid and strongly oxidizing medium, graphite is not affected by other acid, alkali, salt corrosion, do not react with any organic compounds.
Graphite is also a high-temperature resistant material, at high temperature, the graphite will not melt, but at atmospheric pressure at 3,350 ℃ began to sublimate into gas. The strength of general materials decreased gradually at high temperature, but the strength of graphite at 2000 ℃ was higher than that of normal temperature. Graphite also has good thermal shock resistance.
Graphite has good self-lubricating properties, it can be used as antiwear lubricating material in the oil-repellent occasion. The capture cross-section of the high energy neutron is small, and the scattering cross-section is large, with good neutron deceleration performance and strong resistance to neutron radiation damage, and can be used as deceleration material and structural masonry in the nuclear reactor.
The disadvantage of graphite is that the oxidation resistance is worse, as the temperature increases, the oxidizing rate increases.
Graphite material is a carbon material composed of graphite carbon. It is one of the most rapidly developing materials in today’s industrial materials. It is not only used in traditional industrial industries (metallurgy, chemical industry and machinery), but also its application has been extended to a wider range of high-tech fields, such as aerospace, aviation, electronics, electrochemistry, communication, nuclear industry, precision machinery, bioengineering and environmental protection. The graphite material studied in this paper is cold isostatic pressing isotropic high-performance graphite electrode material for EDM (unless otherwise specified, all graphite materials studied in this paper are referred to as graphite).
It is widely used abroad. More than 95% of EDM users in the United States choose graphite as electrode material. In other industrialized countries, such as Japan and Switzerland, Graphite also plays a major role in electrode materials for EDM. In recent years, graphite, as an electrode material, has been widely used in the field of die EDM manufacturing of products in automobile, household appliances, communication and electronics industries in China. The density of graphite is about 1.55-1.859/em3, which is only 1 / 5 of that of copper. At the same time, graphite can be bonded, so it can be used to manufacture large electrodes with complex shapes. Compared with copper electrode materials, graphite has the advantages of high strength, low electrode consumption and small thermal deformation. It is especially suitable for manufacturing and processing electrodes for complex cavity molds with special structures such as thin wall, fins and micro holes. UHP Graphite electrode materials have gradually replaced copper electrodes and become the mainstream of electrode materials for EDM.