The 21st century is the era of black gold, and the uses of graphite products are far higher than we expected. So what are the uses of graphite products that we are currently familiar with?
1. Use as a conductive material
When smelting various alloy steels, ferroalloys or producing calcium carbide (calcium carbide) and yellow phosphorus with electric arc furnace or submerged electric furnace, strong current is introduced through carbon electrode (or continuous self baking electrode ---namely electrode paste) or graphitized electrode to the smelting zone of the electric furnace to generate arc so as to convert electrical energy into heat, and the temperature rises to about 2000 degrees Celsius, so as to meet the requirements of smelting or reaction. Metal magnesium, aluminum, and sodium are generally prepared by molten salt electrolysis. At this time, the anode conductive material of the electrolytic cell is carbon graphite electrode or continuous self-baking electrode (anode paste, sometimes pre-baked anode). The temperature of molten salt electrolysis is generally below 1000 degrees Celsius. Graphitized anodes are generally used as anode conductive materials for salt solution electrolyzers that produce caustic soda (sodium hydroxide) and chlorine. Graphitized electrodes are also used as the conductive material for the furnace head of the resistance furnace used in the production of emery (silicon carbide). In addition to the above uses, carbon and graphite products are widely used as conductive materials in the motor manufacturing industry as slip rings and brushes. They are also used as carbon rods in dry batteries, searchlights or arc carbon rods for arc generation, and anodes in mercury rectifiers, etc.
2. Use as a refractory material
Because carbon and graphite products can withstand high temperatures and have better high temperature strength and corrosion resistance, many metallurgical furnaces can be lined with carbon blocks, such as the bottom, hearth and bosh of blooming furnaces, the inner lining of ferroalloy furnaces and calcium carbide furnaces, the bottom and sides of the aluminum electrolytic cell. Many crucibles used for smelting precious metals and rare metals, and graphite casting crucible used for molten quartz glass are also processed from graphitized blanks. Carbon and graphite products used as refractory materials should generally not be used in an oxidizing atmosphere. Because carbon or graphite is quickly ablated under the high temperature of oxidizing atmosphere.
3. Use as a corrosion-resistant structural material
Carbon graphite electrodes impregnated with organic resin or inorganic resin have the characteristics of good corrosion resistance, good thermal conductivity, and low permeability. This kind of impregnated graphite is also called impermeable graphite. It is widely used in the production of various heat exchangers, reaction tanks, condensers, combustion towers, absorption towers, coolers, heaters, filters, pumps and other equipment, and is widely used in petroleum refining, petrochemicals, and hydrometallurgy, acid and alkali production, synthetic fiber, papermaking and other industrial sectors, which can save a lot of metal materials such as stainless steel. The production of impermeable graphite has become an important branch of the carbon industry.
4. Use as a wear-resistant and lubricating material
Carbon and graphite materials not only have the characteristics of high chemical stability, but also have good lubricating properties. Under the conditions of high speed, high temperature and high pressure, it is often impossible to use lubricating oil to improve the wear resistance of sliding parts. Graphite wear-resistant materials can work in corrosive media at temperatures of -200 to 2000 degrees Celsius and at high sliding speeds (up to 100 m/s) without lubricating oil. Therefore, many compressors and pumps that transport corrosive media widely use piston rings, seals and bearings made of graphite materials. They do not need to add lubricant when they are running. This wear-resistant material is made of ordinary carbon or graphite material impregnated with organic resin or liquid metal material. Graphite emulsion is also a good lubricant for many metal processing (wire drawing, pipe drawing, etc.).
5. As a pyrometallurgical and ultra-pure material
The structural materials used in production, such as crystal growth crucibles, regional refining vessels, brackets, fixtures, induction heaters, etc. for the production of single crystal silicon, are all processed with high-purity graphite materials. Graphite insulation boards and bases used in vacuum smelting, high-temperature resistance furnace tubes, rods, plates, grids and other components are also made of graphite materials.
6. As a casting mold and press mold
The use of carbon and graphite materials has a small thermal expansion coefficient and good resistance to rapid cooling and heating, so it can be used as a mold for glassware and a mold for ferrous metals, non-ferrous metals or rare metals. The castings obtained by graphite casting have precise dimensions and smooth surface. They can be used directly without processing or can be used with a little processing, thus saving a lot of metal. Production of cemented carbide (such as tungsten carbide) and other powder metallurgy processes usually use graphite materials to process press molds and sintering boats.
7. In the atomic energy industry and military industry
The use of graphite in the atomic energy industry and military industry. Because of its good neutron deceleration performance, it was first used as a deceleration material in atomic reactors. Graphite reactor is one of the most widely used atomic reactors at present. Graphite materials used in atomic reactors must have extremely high purity. Some specially treated graphite (such as infiltrating high-temperature-resistant materials on the graphite surface), recrystallized graphite, and pyrolytic graphite have better stability at extremely high temperatures and a higher strength-to-weight ratio. Therefore, they can be used to make solid fuel rocket nozzles, missile nose cones, and parts of space navigation equipment.