Isostatic Graphite refers to graphite materials produced by isostatic pressing. Isostatic graphite is pressed uniformly by liquid pressure during the molding process, and the obtained graphite material has excellent properties. It has large molding specifications, uniform blank structure, high density, high strength, and isotropy, and other advantages. So isostatic graphite is also called "isotropic" graphite.
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Average particle size
Bulk density
Resistivity
Flexural strength
Compressive strength
Shore hardness
Elastic Modulus
Coefficient of thermal expansion (100-600&#;)
Ash
mm
g/cm3
μΩ·m
Mpa
Mpa
HS
Gpa
x10^-6/&#;
%
IG-I
&#;0.025
&#;1.70
&#;15.0
&#;28.0
&#;56.0
&#;50.0
&#;9.5
&#;3.2
&#;0.07
IG-II
&#;0.025
&#;1.75
&#;15.0
&#;35.0
&#;70.0
&#;55.0
&#;10.0
&#;3.8
&#;0.07
IG-III
&#;0.025
&#;1.80
&#;14.0
&#;37.0
&#;75.0
&#;55.0
&#;10.5
&#;4.2
If you are looking for more details, kindly visit Special Graphite Shaped Part for Sale.
&#;0.07
IG-IV
&#;0.025
&#;1.85
&#;13.0
&#;42.0
&#;85.0
&#;55.0
&#;11.0
&#;4.5
&#;0.07
It has found applications in over 30 different industries, from nuclear and metallurgical applications to semiconductor, solar, continuous casting, EDM and many others.
Our Isostatic Graphite is carefully handled during storage and transportation to preserve the quality of our product in its original condition.
Production process of Isostatic Graphite
The production of isostatic graphite requires the crushing, screening, grinding of raw materials, melting of adhesives, and processing of ingredients, kneading, molding, roasting, impregnation, graphitization and other processes.
1. Raw materials and crushing
The raw material for isostatic graphite is needle-shaped petroleum coke, which has low sulfur content, low ash content and low volatile matter. Graphite products made from needle-shaped petroleum coke have the characteristics of high degree of graphitization, low resistance, high surface lubricity, etc., providing super performance graphite electrode product information.
Petroleum coke is a product made by separating light and heavy oils from crude oil by distillation, and then converting heavy oil into a product by thermal cracking. Its main element carbon accounts for more than 80wt%, and the rest are hydrogen, oxygen, nitrogen, sulfur and metal elements (Al, Fe, Ca, Mg, Si). The raw material petroleum coke has a large particle size and needs to be crushed first. To produce fine-grained graphite, most of the powder is 0.075mm, and some of the powder is 0.042mm or 0.037mm micro-powder; to produce ultrafine graphite, the particle size of the powder is less than 0.02mm or smaller, so petroleum coke needs to use air flow mills or other ultrafine grinding equipment. The classification of fine powder is more difficult than soft powder, and special technology is required. Use the crushing equipment and air flow milling equipment commonly used in metallurgy to crush it, in order to obtain petroleum coke powder with suitable particle size.
2. Ingredients and kneading
Mix the purified petroleum coke powder with suitable particle size with the binder in a certain proportion, and mix them sufficiently in the kneading equipment. Commonly used binders are coal tar, asphalt or resin. In the entire isostatic graphite production process, kneading is a very critical process, which is directly related to the subsequent graphite yield. Organic matter and volatile matter in asphalt have a great influence on the yield of graphite products. In order to achieve a relatively high yield, it is necessary to strictly control the temperature rise and fall program and kneading time of the kneading equipment.
Commonly used kneading equipment in the carbon industry include biaxial kneading machines, uniaxial kneading machines, and countercurrent high-speed kneading machines. Countercurrent high-speed kneading machines are used for the preparation of special graphite. In addition, the kneaded paste needs to be processed by a sheeting process. The paste is rolled into 1~3mm thin sheets (1~2 sheets) by a rubber mill, so that the binder and coke powder can be more effectively combined. After sheeting, the paste is ground into paste powder by an all-purpose crusher for isostatic pressing.
3. Molding
The production of isostatically pressed graphite adopts cold isostatic pressing. The graphite samples formed by cold isostatic pressing equipment need to be roasted and impregnated many times. The purpose of roasting is to allow the volatiles in the binder in the graphite to escape. The impregnation is to maintain the compactness of the graphite. The general impregnating agent is various resins or asphalt. The graphite samples formed by cold isostatic pressing need to be roasted and impregnated many times to meet the requirements of special graphite products.
4. Calcination and impregnation
For graphite products that require higher bulk density, cracks and waste products are easily generated during the calcination process, so a slower heating curve should be used; for the calcination of smaller-sized graphite products, square or round containers can be made of heat-resistant materials, and then the raw products can be placed in the container and filled with fillers for isolation and covering, and then loaded into the calcination furnace for calcination. The key to impregnation is penetration. High-density graphite products need to be impregnated 2 to 4 times, and they need to be calcined once after each impregnation; for impregnation, the softening point of the impregnant should be correctly selected (related to the viscosity of the impregnant), and the preheating temperature before the calcination product is impregnated and the temperature, pressure, vacuum degree, pressurization time and other process parameters of the impregnation tank should be controlled to achieve a good impregnation effect.
The repeated impregnation and calcination process has a long processing cycle, generally about 2 to 3 months, which puts higher requirements on the service life of the equipment, and also increases the investment of manpower and material resources, and the economic benefits are poor.
5. Graphitization and purification treatment
Carbon products after roasting need to be heat treated at a high temperature of ~&#; before they can be converted into graphitized products. The main difference between carbon products and graphite products is that the carbon atom lattice of the microstructure of carbon products is a chaotic layer structure, while the carbon atoms after graphitization are a three-dimensional ordered layered structure. The graphitization treatment of isostatic graphite is carried out in a graphitization furnace. In addition, chlorine and Freon gases are introduced during the graphitization process to make the impurity elements form chlorides and fluorides and volatilize and escape to achieve the purpose of purification.
Application of isostatic graphite
1. Solar cells and semiconductor wafers
In the solar energy and semiconductor industries, isostatic graphite is used in large quantities to make single crystal vertical pulling furnace hot field graphite parts, multicrystalline silicon melting furnace heaters, compound semiconductor manufacturing heaters, crucibles and other parts. In recent years, solar photovoltaic power generation has developed rapidly, and the production of single crystal silicon and polycrystalline silicon in the photovoltaic industry has a huge demand for graphite. At present, both single crystal and polycrystalline silicon products are developing towards large-scale and high-end development, and there are higher requirements for isostatic graphite, namely: larger specifications, higher strength, and higher purity.
2. Nuclear field
Isostatic graphite has medium mechanical properties, especially excellent high-temperature mechanical properties, large thermal conductivity, and low linear expansion coefficient. In high-temperature gas-cooled reactors, it is mainly used as a reflector, moderator, and active zone structural material, and together with nuclear fuel, it constitutes a nuclear fuel assembly. At a temperature of 400~&#;, it is exposed to high-energy gamma rays and fast neutrons for several years, which can easily cause irradiation damage, thereby changing the structure and properties of graphite. Therefore, the material is required to have a high degree of graphitization, good isotropy, uniform composition, and low elastic modulus.
3. Electrode field
Graphite has no melting point, is a good conductor of electricity, has good thermal shock resistance, and is an excellent electrode material for EDM. Ordinary graphite materials are coarse-grained, low-density anisotropic graphite, which cannot meet the needs of EDM, while isostatic graphite electrodes have uniform, dense structure and high processing precision, which can meet these requirements.
4. Continuous casting crystallizer and mold graphite
It is used for continuous casting crystallizers and mold materials that can withstand high temperatures and high pressures for the production of superhard materials. Isostatic graphite, due to its microparticle structure, high mechanical strength, and uniform heat conduction, makes the surface of continuous casting and molded products smooth, with high intrinsic quality and long service life, making it an excellent material for crystallizers. Moreover, for large sintered materials, the thickness of the mold wall should be as thin as possible, and fine-structured isotropic graphite with high strength must be used.
5. Other uses
It is used in carbon brushes, mechanical seals, collector plates of touch wheels, etc., and high lubricity and high conductivity are extremely important while requiring processing precision. Isostatic graphite is also used to make diamond tools and sintering molds for cemented carbide, thermal field components of optical fiber drawing machines (heaters, insulation cylinders, etc.), thermal field components of vacuum heat treatment furnaces (heaters, bearing frames, etc.), as well as precision graphite heat exchangers, mechanical sealing components, piston rings, bearings, rocket nozzles, etc.
Development direction
Isostatic graphite is a new type of graphite material and a fine product among graphite materials. Due to its series of excellent properties, it will inevitably be closely linked to high-tech and high-end national defense technology, becoming one of the extremely valuable new materials in the 21st century. With economic development, the market capacity of static graphite is increasing day by day, and its development potential is huge.
In the fierce market competition, the foundation and way out for isostatic graphite production enterprises are: to upgrade products, develop in the direction of large specifications, fine structures (ultra-fine structures), high strength, high purity, and multi-functions, conform to the development trends of photovoltaic industry, machinery manufacturing, and nuclear energy utilization, and better serve the development of the economy.
China has become the world's "manufacturing factory", and the development of science and technology has brought about new industrial reforms. The broad application fields of isostatic graphite materials and products have brought vitality to the isostatic graphite industry.
Hebei Benhong New Materials Technology Co., Ltd. can provide isostatic graphite blocks of various uses and sizes. Because of advanced equipment and many years of experience in graphite product production, our products are favored by domestic and foreign users. If you also have a demand for isostatic graphite blocks, you can contact me.
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