Graphite electrode refers to petroleum coke and asphalt coke as the main material, coal tar pitch as binder, which is made by raw material calcination, crushing milling, compounding, kneading, forming, roasting, impregnating, graphitization and mechanical processing. High-temperature graphite conductive material, called artificial graphite electrode, is distinguished from natural graphite electrode prepared by using natural graphite as raw material. There are several types of graphite electrodes used:
(1) Used in electric arc furnace
Electric furnace steelmaking is the largest use of graphite electrodes. The output of China's electric furnace steel accounts for about 18% of the crude steel output, and the graphite electrode for steelmaking accounts for 70% to 80% of the total graphite electrode. Electric furnace steelmaking uses a graphite electrode to introduce a current into the furnace, and smelting is performed by a high-temperature heat source generated by an arc between the electrode end and the charge.
(2) Used in mine electric furnace
The ore electric furnace is mainly used for the production of industrial silicon and yellow phosphorus. It is characterized in that the lower part of the conductive electrode is buried in the charge, an electric arc is formed in the material layer, and the heat generated by the resistance of the charge itself is used to heat the charge, wherein current is required. Graphite electrodes are required for higher density electric furnaces. For example, about 100 kg of graphite electrode is consumed for each 1T of silicon produced, and about 40 kg of graphite electrode is consumed for each 1T of yellow phosphorus produced.
(3) For resistance furnace
The graphitization furnace for producing graphite products, the melting furnace for melting glass, and the electric furnace for producing silicon carbide are all electric resistance furnaces. The materials contained in the furnace are both heating resistors and objects to be heated. Usually, graphite electrodes for electric conduction are embedded in the resistance furnace end. In the furnace wall of the department, the graphite electrode used here is not continuously consumed.
(4) For the preparation of shaped graphite products
The graphite electrode blank is also used to process a variety of shaped graphite products such as enamel, mold, boat and heating element. For example, in the quartz glass industry, for every 1T electrofusion tube produced, a graphite electrode blank 10T is required; for every 1T quartz brick produced, 100 kg of graphite electrode blank is consumed.
With the continuous development of science and technology, people have also developed many new uses for graphite. The demand for graphite is also because graphite is used more, so now graphite is also considered a fast-moving product. For example, it is used on solar cells and semiconductor wafers, as well as on nuclear graphite, electrode graphite, continuous casting of crystalline graphite and abrasive graphite.
Flexible graphite products, also known as expanded graphite, are a new type of graphite product developed in the age. The United States successfully researched flexible graphite sealing materials to solve the problem of leakage of atomic energy valves, and then developed production in Germany, Japan and France. In addition to the properties of natural graphite, this product has special flexibility and elasticity.
Graphite is usually used in electrode graphite. This is the most common one because graphite is a good conductor of electricity, has good thermal shock resistance, and is also an excellent general electrode material for EDM electrode materials. The low-density anisotropic graphite with coarse-grained structure can not meet the requirements of EDM, and the isostatically pressed graphite electrode has a uniform structure, compactness and high processing precision, which can meet the needs of this aspect. Others will use solar crystals and semiconductors, using graphite to make single crystal straight pull furnace thermal field graphite parts polysilicon melting furnace heaters, compound conductor manufacturing heaters, crucibles and other components.
Solar photovoltaic power generation is developing rapidly. The demand for monocrystalline silicon and polycrystalline silicon in the photovoltaic industry is huge. At present, single crystal and polycrystalline silicon products are all facing large-scale and high-end development, and there is a higher demand for isostatic graphite. Namely: larger size, higher strength, higher purity. It can also be used in carbon brushes, mechanical seals, and collector plates of contact wheels. It is extremely important to require processing accuracy while also providing lubricity and high electrical conductivity. Ordinary graphite materials need to be impregnated with resin and metal to improve strength and air tightness, but their use is limited in corrosion resistance and high temperature resistance.
In addition, graphite is a polishing agent and rust inhibitor for glass and paper in the light industry. It is an indispensable raw material for the manufacture of pencils, inks, black lacquers, inks and synthetic diamonds and diamonds. It is a good energy-saving and environmentally friendly material that the United States has used as a car battery. With the development of modern science and technology and industry, the application field of graphite is still expanding, and it has become an important raw material for new composite materials in the high-tech field, and plays an important role in the national economy.