① As a Conductive Material
When using electric arc furnaces or submerged arc furnaces to smelt various steel alloys, ferroalloys, or produce calcium carbide (calcium carbide) and yellow phosphorus, a strong current is introduced into the furnace's melting zone through carbon electrodes (or continuous self-baking electrodes-also known as electrode paste) or graphitized electrodes, generating an arc. This arc converts electrical energy into heat, raising the temperature to around 2000°C, thereby achieving the desired smelting or reaction conditions. Magnesium, aluminum, and sodium are generally produced by molten salt electrolysis. In these cases, the electrolytic cell's anode conductive material is graphitized electrodes or continuous self-baking electrodes (anode paste, sometimes pre-baked anodes). The temperature of molten salt electrolysis is generally below 1000°C. Graphitized anodes are generally used as the conductive anode material in salt solution electrolytic cells used to produce caustic soda (sodium hydroxide) and chlorine. Graphitized electrodes are also used as the conductive material for the furnace head of resistance furnaces used to produce corundum (silicon carbide). In addition to the aforementioned uses, carbon and graphite products are widely used as conductive materials in the motor manufacturing industry, including slip rings and brushes. They are also used as carbon rods in dry cell batteries, arc rods for searchlights or arc generators, and anodes in mercury rectifiers.
② Use as refractory materials
Because carbon and graphite products can withstand high temperatures and possess good high-temperature strength and corrosion resistance, they can be used to line many metallurgical furnaces, such as the hearth, hearth, and belly of ironmaking furnaces, the linings of ferroalloy and calcium carbide furnaces, and the bottom and sides of aluminum electrolytic cells. Many crucibles used in precious and rare metal smelting, as well as graphitized crucibles used for melting quartz glass, are also made from graphitized blanks. Carbon and graphite products used as refractory materials should generally not be used in oxidizing atmospheres. This is because either carbon or graphite will rapidly ablate at high temperatures in oxidizing atmospheres.
③ Use as a corrosion-resistant structural material
Graphitized electrodes impregnated with organic or inorganic resins exhibit excellent corrosion resistance, thermal conductivity, and low permeability. This impregnated graphite is also known as impermeable graphite. It is widely used in the manufacture of various equipment, including heat exchangers, reactors, condensers, combustion towers, absorption towers, coolers, heaters, filters, and pumps. It is widely used in industries such as petroleum refining, petrochemicals, hydrometallurgy, acid and alkali production, synthetic fibers, and papermaking, saving significant amounts of stainless steel and other metal materials. The production of impermeable graphite has become a key branch of the carbon industry.
④ Use as a wear-resistant and lubricating material
In addition to their high chemical stability, carbon and graphite materials also exhibit excellent lubrication properties. Under conditions of high speed, high temperature, and high pressure, it is often impossible to improve the wear resistance of sliding parts with lubricants. Graphite wear-resistant materials can operate without lubricants in corrosive media at temperatures ranging from -200 to 2000°C and at very high sliding speeds (up to 100 m/s). Therefore, many compressors and pumps that transport corrosive media widely use graphite for piston rings, seals, and bearings. These materials operate without the need for lubricants. This wear-resistant material is made from ordinary carbon or graphite impregnated with an organic resin or liquid metal. Graphite emulsions are also excellent lubricants for many metalworking processes, such as wire drawing and tube drawing.
⑤ As a high-temperature metallurgical and ultra-pure material
Structural materials used in production, such as crystal growth crucibles, regional refining vessels, supports, fixtures, and induction heaters used in single-crystal silicon production, are all made from high-purity graphite. Graphite insulation panels and bases used in vacuum smelting, as well as components such as tubes, rods, plates, and grids in high-temperature resistance furnaces, are also made from graphite.