Bearing is a kind of sliding parts commonly used in mechanical industry, and its material is different from metal, nonmetal and composite materials.Learn More
Graphite material has: high temperature resistance, oxidation resistance, chemical stability, good self lubrication. Its texture is hard and brittle, its plasticity is not good, and its impact resistance is poor.
Graphite bearings are generally used in the special conditions: lubricating oil cannot be used, low speed and heavy load, high working temperature, or acid-base liquid cannot be used, oil can not be used or metal corrosion can not be used. Graphite bearing is not suitable for high speed and impact load.
Graphite bearing materials are divided into: pure carbon, carbon impregnated resin, carbon impregnated metal, inlaid graphite, resin hot pressed graphite. Mainly used in: high temperature kiln rotating support parts, chemical equipment rotating support parts, chemical acid and alkali pump bearings, liquid food pump bearings, textile machinery, instrument bearings, submersible pumps, mold plane bearings and other fields.
Due to the different material and performance of graphite bearing, the type selection is very important. The same material, regular manufacturers and general small processing workshop product quality difference is larger, not cheap.
In the industrial purification process, it is the most advanced treatment method in the world to mix the purified gas and solvent, and use the rotary injection of graphite rotor to purify the aluminum melt. So in the process of using the graphite rotor, it is inevitable that there will be damage, so next teaches you to take measures from the causes of damage to make the graphite rotor life longer.
The first reason for damage is high temperature oxidation: graphite is mainly composed of carbon. Visible oxidation occurs when graphite is exposed to air over 600 ℃. The products of carbon oxidation are CO and CO2, which can not protect the rotor. Generally speaking, the degassing box can not be completely closed, and most of the chambers are not filled with protective gas, so the oxidation of graphite rotor is inevitable. As a result of oxidation, the diameter of graphite rotor shaft gradually decreases until it is broken and scrapped.
Corresponding protection measures: anti oxidation coating rotor, effectively slow down the rotor oxidation process, prolong the service life of the rotor
The second damage reason is liquid aluminum erosion: the graphite rotor is immersed in the liquid aluminum in the degassing box, and generally rotates at the speed of 200R / min ~ 400R / min and strongly agitates the liquid aluminum, which will produce strong erosion and friction on the rotor. Especially in the liquid surface and rotor rod contact parts gradually thin, and finally will fracture scrap.
Corresponding protection measures: anti oxidation coating rotor, high quality graphite raw material, high strength, anti erosion
The second damage reason is the influence of the transmission system: the transmission system of the degassing device is not stable, especially the connection with the rotor is not concentric, and the rotor swings in the process of operation. On the one hand, the friction between the rotor and the sealing plug causes damage; on the other hand, the rolling of the liquid level increases, and the oxidation and erosion of the graphite rotor intensifies, speeding up the loss of the rotor.
Corresponding protection measures: anti oxidation coating rotor, precision CNC machining, high coaxiality
Because graphite crucible has high temperature resistance, high melting point and other characteristics, it is very commonly used. In addition to the need to pay attention in the process of use, the graphite crucible also needs to do the following preparations before use:
1. Check the graphite crucible for cracks before operation. If there is no cracks, heat the graphite crucible to above 600 ° C and dry it thoroughly.
2. There shall be no ponding around the furnace and in the pit in front of the furnace, and irrelevant articles shall not be stacked near the graphite crucible.
3. Strictly check whether there are explosives in the charge, preheat the charge and ensure it is dry, and add the graphite crucible slowly.
Tips: before using the graphite crucible, the above three points must be done well, otherwise it is very likely to cause the risk of explosion when using the graphite crucible.
Graphite plate has good electrical conductivity, high temperature resistance, acid and alkali corrosion resistance and easy processing. Graphite plate is the first choice for heat conduction plate, and it can also be used as anode plate, so it has a wide range of applications.
Advantages of graphite plate:
1. The ideal sealing material with strong sealing performance has many excellent sealing performance.
2. Thermal stability, self lubrication, corrosion resistance, non aging, non brittle, conductive, fire resistant, etc.
3. It has excellent corrosion resistance, high and low temperature resistance, good compression resilience and good strength.
Application of graphite plate:
1. Refractory: in smelting industry, graphite plate is made of graphite, which is used as protective agent for steel ingot and magnesia carbon brick for lining of smelting furnace.
2. Conductive materials: in the electrical industry, graphite is widely used as electrode, brush, rod, carbon tube and TV picture tube coating.
3. Wear resistant materials and lubricants: in many mechanical equipment, graphite is used as wear-resistant and lubricating materials, which can slide at the speed of 100M / s in the temperature range of - 200 ~ 2000 ℃, with little or no lubricating oil.
4. Sealing material: flexible graphite is used as piston ring gasket and sealing ring of centrifugal pump, water turbine, steam turbine and equipment conveying corrosive medium.
5. Corrosion resistant materials: graphite is used as utensils, pipes and equipment, which can resist the corrosion of various corrosive gases and liquids. It is widely used in petroleum, chemical industry, hydrometallurgy and other departments.
Now the application of flexible graphite is more and more extensive. Qingdao persistent high tech will explain the application field of flexible graphite for you. Flexible graphite is mainly used in these two aspects: one is to use as various filler materials; the other is to use as cushion materials.
It is mainly used for dynamic sealing or static sealing of pumps, valves and kettles. The sealing method is to cut the material into the required length and width, wrap it on different metal parts, and then limit the forming on the press. The sealing packing restricted by this method is suitable for various valve parts such as stop valve, gate valve, regulating valve, ball valve and heating valve. Flexible graphite sheet can also be wound directly around the pump shaft or stem, and then pressed into the packing box with gland. The practice shows that the sealing effect of the direct winding on the shaft is not as good as the pre - limiting molding. The difference between the two methods is due to the different pressure applied and the different degree of uniformity, which results in different compaction degree.
2. cushion material
It is used for gasket such as pressure pad and clamp pad, etc. as sealing information of pad. Some of these materials are directly limited by expanded graphite particles, some are made by punching or cutting flexible graphite plates or composite plates, or cut into the required specifications and shapes and data features are soft and elastic, and they can be easily sealed with the sealing surface.
Flexible graphite data: a kind of non fiber material, that is, flexible graphite is made into sheet and then pressed into sealing filler by die. Flexible graphite, also known as expanded graphite, removes impurities from natural flake graphite. After the treatment with strong oxidation and mixed acid, it becomes graphite oxide. The carbon dioxide is released by the decomposition of oxidized graphite, and the volume expands rapidly, which becomes the flexible graphite with loose texture, soft and durable.
The main characteristics of flexible graphite are as follows:
1. excellent heat resistance and cold resistance. The physical properties of flexible graphite can be applied to about 600 ℃ in air, from ultra low temperature of -270 ℃ to high temperature of 3650 (in non oxidation gas);
2. high rebound rate. When the shaft or shaft sleeve is radial circular runout due to eccentric manufacturing and installation, it has the floating function to meet the requirements. Even if the graphite shows cracks, it can be well closed, and then the binding is tight to avoid leakage.
3. good self lubrication. Flexible graphite, like natural graphite, slips easily under the action of external force, so it has lubrication, good wear reduction and small friction coefficient;
4. excellent chemical corrosion resistance. Besides corrosion in strong oxidizing medium such as nitric acid and concentrated sulfuric acid, flexible graphite has little corrosion in other acids, bases and solvents;
What are the characteristics of graphite electrode materials? Next, Xiaobian will introduce you one by one.
1. Easy to polish;
Because the cutting resistance of graphite is only 1 / 5 of that of copper, it is easier to grind and polish;
2. Light weight;
The density of graphite is only 1 / 5 of that of copper. When the large electrode is used for EDM, it is more suitable for the use of large mold;
3. The loss is small;
Because there are C atoms in the spark oil, the high temperature causes the C atoms in the spark oil to be differentiated, and forms a protective film on the surface of the graphite electrode, which compensates for the loss of the graphite electrode;
4. Low cost;
Due to the rising price of copper in recent years, the price of graphite is lower than that of copper in all aspects; for the universality of carbon in the same volume, the price of graphite is 30% to 60% lower than that of copper, which is relatively stable, and the short-term price is relatively small.
5. No burr;
After the copper electrode is processed, it needs technology to remove the burr, while the graphite electrode is processed without burr, which not only saves a lot of cost and manpower, but also simplifies the automatic production;
6. Fast speed;
Graphite discharge is 2-3 times faster than copper, and the material is not easy to deform. It has a significant advantage in the processing of thin rib electrode. The softening point of copper is about 1000 degrees, and the deformation is caused by heating. The progressive temperature of graphite is about 3650 degrees. In comparison, the coefficient of thermal expansion of graphite is only 1 / 30 of that of copper;
So what is the role of graphite in graphite rods? Next, will introduce you one by one.
1、 Graphite can prevent boiler scaling, graphite can be coated on metal chimney, roof, bridge, pipeline can be anti-corrosion and rust proof.
2、 As conductive materials: used in the electrical industry as the anode of electrode, brush, carbon rod, carbon tube, mercury positive current device, graphite washer, telephone parts, coating of television picture tube, etc.
3、 As wear-resistant and smooth data: graphite is often used as a smooth agent in the mechanical industry. The smooth oil can not be used in high speed, high temperature and high pressure, while graphite wear-resistant data can be used at a high sliding speed at 200-2000 ℃ without smooth oil. Many equipment transporting corrosion media, graphite materials are widely used to make piston cup, sealing ring and bearing. They do not need to add smooth oil when they work. Graphite milk is also an outstanding smooth agent in many metal processing (drawing wire and drawing pipe).
4、 As casting, sand turning, die pressing and high temperature metallurgy data: because of the small thermal expansion coefficient of graphite and the ability to withstand the change of rapid cold and rapid heat, it can be used as a mold for glass ware. After using graphite, ferrous metal can be used to obtain the casting scale accurately, and the surface finish rate is high, and it can be used without processing or processing, so many metals are saved. The powder metallurgy process such as hard alloy is produced. The ceramic boat for pressing and sintering is usually made from graphite materials. Crystal growth crucible, regional quintessence container, support fixture, induction heater, etc. of monocrystalline silicon are all processed with high purity graphite. In addition, graphite can be used as heat insulation plate and base of vacuum smelting, high temperature resistance furnace tube, rod, plate, lattice shed and other elements.
5、 As fire resistant materials: graphite and its products have the properties of high temperature resistance and high strength. It is used to make graphite crucible in metallurgical industry. Graphite is used as the protective agent of ingot and lining of metallurgical furnace in steel making.
6、 Graphite can be used as pencil core, pigment and polishing agent.
7、 Electrode: why graphite can replace copper as electrode.
8、 Graphite has excellent chemical stability. Through the special processing of graphite, with the characteristics of corrosion resistance, good heat conductivity and low permeability, many of them are used to make heat exchanger, reverberation tank, condenser, incinerator, absorption tower, cooler, heater, filter and pump equipment. It is widely used in petrochemical, hydrometallurgy, acid-base production, synthetic fiber, paper industry and other industries, which can save a lot of metal data.
Because the carbon rod is used at high temperature, it is easy to conduct excellent chemical stability. It has been widely used in national defense, machinery, metallurgy, chemical industry, casting, non-ferrous alloy, light and other categories, especially black carbon rods, and also used as ceramics, semiconductors, medicine, environmental protection, laboratory analysis and other categories, and has become the most widely used non-metallic materials. When cutting steel, it is not necessary to use flammable and explosive gas like oxyacetylene flame cutting, which has low cost and safe operation. It can be used to process many kinds of metals which can not be processed by gas cutting, such as cast iron, stainless steel, copper, aluminum, etc. with high efficiency and ideal results.
1. Strictly follow the operating procedures, such as heating, melting, remelting and furnace shutdown, to protect the graphite parts. After each furnace is disassembled, the graphite accessories should be carefully cleaned, the seed crystal and the graphite thermal field accessories should be carefully checked, and the specific records should be made.
2. If part of the crucible is damaged (for example, three pieces are broken and one piece is broken) but it has not reached the life limit, it can be put together or replaced (if there are only a few heats of new three piece crucible, the workshop supervisor will decide whether to use it or not after judging it, make up a set of crucible that can be used and can be put together, and seal and keep the crucible that can be used but not used for the time being). It is suggested that the sealed storage should be used in the furnace of purification when it is used again.
3. Every time the furnace is disassembled, the oxide in the thermal field shall be sorted out, and the siliconizing on the graphite parts shall be cleaned up. The guide tube and insulation cover shall be carefully cleaned to prevent impurities from polluting the raw materials. In addition to personal safety, take care to handle graphite parts with care.
4. In principle, those whose lifespan has reached the replacement deadline need to be replaced (or let experienced people identify them and decide whether they can continue to use them). For those who are not used for the time being, they should be sealed in plastic bags, packed in cartons, marked with heat number, heat number, reason for replacement, source and date, and kept properly
5. Check the graphite accessories for cracks, especially the graphite crucible, graphite tray and graphite crucible rod. If there are cracks, immediately report to the workshop supervisor and replace them. Judge or report to the workshop supervisor where there is silicon. Before the five heats are used to estimate the service life, the shift leader is responsible for checking and checking. After the five heats before the estimated service life are used, the workshop supervisor is responsible for checking and checking.
6. After the service life of graphite accessories is expired, the graphite accessories (graphite tray, crucible rod, graphite crucible) that may cause heavy losses after overdue use shall be removed and replaced with new products. The replaced graphite accessories shall be sealed up, and then be handled after joint review by single crystal workshop, technology department and production department. Other accessories such as heater, heat preservation cylinder, guide cylinder, etc. shall be handled carefully Check to see if there are small cracks and defects. In principle, these graphite accessories can be used continuously without the above defects. It is necessary to make specific records about the graphite thermal field accessories that present the closed furnace.
7. Record the details of the graphite thermal field accessories. The graphite accessories with problems should be recorded and put into the designated address to prevent mixing.
First, we can understand the relevant characteristics of graphite. 1. high temperature resistance, high melting point of graphite, 3850 ℃ in vacuum, increase at low pressure, and increase temperature of 2200 degrees. Unlike general data, when the temperature increases, graphite not only does not soften, but increases its strength, but increases its tensile strength by twice when it is 2500 ℃. 2. special thermal shock resistance, the thermal expansion of graphite is anisotropic, so the micro expansion coefficient is not large, and the volume of graphite is not changed under the condition of sudden temperature change. In addition, it has excellent thermal conductivity, so the thermal shock resistance of graphite is outstanding. As mentioned above, graphite parts should be able to work stably at high temperature for a long time.
In general, compared with other graphite equipment such as heat preservation cover and heater, the flap pot is the same data, same manufacturer and same working environment. Why is the life of the pot far lower than that of the heat preservation cover and heater?
The main reason for cracking of the triple pot is quartz crucible. 1. because the density of molten silicon is larger than solid silicon, the bottom material of the pot will break the quartz crucible during cooling, and the quartz crucible is attached to the triple valve pot. When the stress produced by the cracking of the quartz crucible is greater than the stress of the triple valve crucible, the triple valve crucible will crack. This is to say, if the bottom material of the pot is too much, the triple valve pot will be broken. This is to say, if the bottom material of the pot is too much, the triple valve crucible will be broken The cause of the pot. 2. if the heating time is too long, the quality of the quartz crucible is not over-standard and the raw material pH is not up to the requirements, silicon leakage and silicon permeability will be caused. After the gap between the fused silicon infiltrated into the three valve pot is cooled, one is to break the three-way pot, the other is to make the three-way pot bond with each other, and make it separate from each other during furnace cleaning, which can cause cracking. 3. in the heating process, only the heat source of the three-way pot comes from two aspects: one is the radiation of the heater, the other is from the conduction of the quartz crucible, which leads to the uneven heating of the three-way pot, which expands in some directions, shortens in other directions, and then causes the triple flap pot to crack.
The components of the heat field, such as heater, three-way pot, graphite holder and thermal screen, are all made of graphite. In the process of production, often encounter the phenomenon of heating equipment damage, so what is the reason for the damage of graphite equipment, what measures should be taken to extend the life of graphite equipment? The damage of graphite equipment is mainly caused by human and deterioration. As long as the human side strengthens the management and strengthens the staff's defense awareness, the loss can be reduced to the lowest point. Deterioration is the first thing to discuss here.
Graphite is a crystalline deposit of carbonaceous elements, and its crystal framework is hexagonal layered structure. The distance between each mesh layer is 340pm, and the distance between carbon atoms in the same mesh layer is 142pm;. It belongs to hexagonal crystal system with perfect lamellar cleavage. The cleavage surface is mainly composed of molecular bonds and has weak attraction to molecules, so it has good natural floatability.
Graphite products maintain the original chemical characteristics of flake graphite, and also have strong self-lubricating properties. The specially processed graphite has the characteristics of corrosion resistance, good thermal conductivity and low permeability. It is widely used in making heat exchangers, reaction tanks, condensers, incinerators, absorption towers, coolers, heaters, filters, pumps and other equipment. These equipment are used in petrochemical, hydrometallurgy, acid and alkali production, synthetic fiber, paper and other industrial sectors, which can save a lot of metal materials. With the continuous development of science and technology, people have developed many new uses for graphite. Flexible graphite products, also known as expanded graphite, is a new kind of graphite products. In addition to the characteristics of natural graphite, it also has special flexibility and elasticity. Therefore, it is an ideal sealing material. It is widely used in petrochemical, atomic energy and other industrial fields. The world market demand is increasing year by year.
Graphite products, especially graphite mattresses, can produce negative oxygen ions after heating, activate the surrounding articles, maintain human health, effectively prevent aging, and make skin full of luster and elasticity. The pan and pot made of graphite are heated quickly, and the cooked food is heated evenly from the inside to the outside. The heating time is short. It not only tastes pure, but also can lock the original nutrition of the food. Crucibles and related products are made of graphite. They are shaped and fire-resistant crucibles and related products. They have high fire resistance and low thermal expansion. In the process of melting metal, they are also stable when they are moistened and washed by metal. They have excellent thermal shock stability and excellent conductivity at high temperature. Therefore, graphite crucibles and related products are widely used in the process of direct melting metal.
At room temperature, the chemical properties of carbon are relatively stable, insoluble in water, dilute acid, water, etc
Dilute alkali and organic solvent; react with oxygen at high temperature to produce carbon dioxide or carbon monoxide; in halogen, as long as fluorine can react directly with elemental carbon; under heating, elemental carbon is easily oxidized by acid; at high temperature, carbon can react with many metals to form metal carbides. Carbon is reductive and can temper metals at high temperatures. In addition, recent studies have found that graphite can be dissolved by chlorosulfonic acid to form a chlorosulfonic acid "solution" of monolayer graphene.
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