First, use as a conductive material When smeltin […]
First, use as a conductive material
When smelting various alloy steels, iron alloys or producing calcium carbide (calcium carbide) and yellow phosphorus in an electric arc furnace or a submerged arc furnace, a strong electric current is introduced through a carbon electrode (or a continuous self-baking electrode--electrode paste) or a graphitized electrode. An electric arc is generated in the melting zone of the electric furnace to convert electrical energy into heat energy, and the temperature rises to about 2000 degrees Celsius to meet the requirements of smelting or reaction. Magnesium, aluminum and sodium are generally prepared by electrolysis of molten salts. At this time, the anode conductive material of the electrolytic cell is made of a graphitized electrode or a continuous self-baking electrode (anode paste, sometimes with a prebaked anode). The temperature of molten salt electrolysis is generally below 1000 degrees Celsius. An anode conductive material for a caustic soda solution electrolytic cell for producing caustic soda (sodium hydroxide) and chlorine gas generally uses a graphitized anode. The conductive material of the burner of the electric resistance furnace used for the production of silicon carbide (silicon carbide) is also a graphitized electrode.
In addition to the above applications, carbon and graphite products are widely used as conductive materials in the motor manufacturing industry as slip rings and brushes, as well as carbon rods in dry batteries, searchlights or arc carbon rods for arcing, anodes in mercury rectifiers. Wait.
Second, use as a refractory
Because carbon and graphite products can withstand high temperature and have good high temperature strength and corrosion resistance, many metallurgical furnace linings can be built with carbon blocks, such as furnace bottom, hearth and belly of ironmaking furnace, ferroalloy furnace and calcium carbide furnace. The lining, the bottom and sides of the aluminum cell. Many of the graphitized bismuth used for bismuth, fused silica glass, etc. for precious metal and rare metal smelting are also processed from graphitized billets. Carbon and graphite articles used as refractory materials should generally not be used in oxidizing atmospheres. Because no flaws are carbon or graphite that quickly ablate at high temperatures in an oxidizing atmosphere.
Third, as a corrosion-resistant structural material
The graphitized electrode impregnated with an organic resin or an inorganic resin has characteristics of good corrosion resistance, good thermal conductivity, and low permeability, and the 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, etc., widely used in petroleum refining, petrochemical, hydrometallurgy. Industrial sectors such as acid and alkali production, synthetic fiber, and papermaking can save a lot of metal materials such as stainless steel. Impervious graphite production has become an important branch of the carbon industry.
Fourth, use as wear and lubrication materials
In addition to its high chemical stability, carbon and graphite materials also have good lubricating properties. It is often impossible to use lubricating oil to improve the wear resistance of sliding parts under conditions of high speed, high temperature and high pressure. Graphite wear resistant materials can operate in corrosive media at temperatures from -200 to 2000 ° C and at very high sliding speeds (up to 100 m / s) without the use of lubricants. As a result, many compressors and pumps that transport corrosive media use piston rings, seals and bearings made of graphite. They do not require the addition of a lubricant when they are running. The wear resistant material is impregnated with an ordinary carbon or graphite material through an organic resin or a liquid metal material. Graphite emulsions are also good lubricants for many metal processing (drawing, drawing, etc.).
5. As a structural material for the production of high temperature metallurgy and ultrapure materials
For example, crystal growth rafts for the production of single crystal silicon, regional refining vessels, supports, fixtures, induction heaters, etc., are all processed from high-purity graphite materials. Graphite insulation board and base used in vacuum smelting, high-temperature resistance furnace tube, rod, plate, grid and other components are also processed by graphite material.
6. Use as a mold and die
Carbon and graphite materials have a small coefficient of thermal expansion and are resistant to rapid cooling and heat, so they can be used as molds for glassware and molds for ferrous and non-ferrous metals or rare metals. The castings obtained by graphite casting are accurate in size and smooth in surface. They can be used directly without processing or can be used as long as they are processed, thus saving a lot of metal. For the production of powder metallurgy such as cemented carbide (such as tungsten carbide), it is common to use graphite materials to process boats for compression and sintering.
7. Use in the atomic energy industry and military industry
Graphite has been used as a decelerating material in atomic reactors because of its good neutron deceleration performance. Graphite reactors are currently a large number of atomic reactors. The graphite material used in the atomic reactor must have a very high degree of purity. Some specially treated graphite (such as infiltrating high temperature resistant materials on the graphite surface) and recrystallized graphite, pyrolytic graphite, have better stability at a very high temperature and a high strength to weight ratio. Therefore, they can be used to make nozzles for solid fuel rockets, nose cones for missiles, and parts for space navigation equipment.