Views: 0 Author: Site Editor Publish Time: 2013-10-10 Origin: Site
1. High temperature resistance
Graphite is one of the most heat-resistant materials known at present. Above 2000ºC, the general material has already turned into gas, or is in a melting state. Even some hard-to-tolerate metals will lose strength around 2500 ºC. Tungsten is known to have the highest melting point of 3600 ºC, but graphite will not melt at this temperature. Its melting point is 3850 ºC (+50 ºC), boiling point is 4250 ºC. All kinds of heat-resistant materials are placed under 7000 ºC ultra-high temperature arc for 10 seconds, graphite loss is the smallest. By weight, the loss of graphite is 0.8%, nylon fiber reinforced phenolic plastics is 1.2%, silicon carbide is 1.7%, high alumina steel and jade is 8.2%, and zirconia, the most heat-resistant metal oxide, is 12.9%.Thus, the high temperature resistance of graphite is very outstanding.
The strength of general materials decreases gradually at high temperatures, while the strength of graphite increases twice as much when heated to 2000ºC. However, the oxidation resistance of graphite is poor. With the increase of temperature, the oxidation rate increases gradually.
2. Special thermal shock resistance
Graphite has good thermal shock resistance. When the temperature changes sharply, the coefficient of thermal expansion is small, so it has good thermal stability. There will be no cracks in the change of temperature.
3. Thermal conductivity and electrical conductivity
Graphite has good thermal conductivity. Although the conductivity of graphite is not comparable to that of copper and aluminum, its thermal conductivity is quite high compared with ordinary materials. For example, it is 4 times higher than stainless steel, 2 times higher than carbon steel and 100 times higher than ordinary non-metal.
The thermal conductivity of graphite is not only higher than that of steel, iron, aluminum and other metal materials, but also decreases with the increase of temperature, which is different from general metal materials. The thermal conductivity of general technology increases with the increase of temperature. Graphite even tends to be adiabatic at extremely high temperatures. Therefore, graphite has thermal insulation at ultra-high temperature.
4. Lubrication
The lubrication performance of graphite is similar to that of molybdenum disulfide, and the friction coefficient is less than 0.1. Its lubrication performance varies with the scale size. The larger the scale is, the smaller the friction coefficient and the better the lubrication performance will be.
5. Plasticity
Graphite has plasticity and can be developed into transparent sheets, but the hardness of high strength graphite is so great that it is difficult to process with diamond tools.
6. Chemical stability
Graphite has good cultural stability at room temperature. It can resist acid, alkali and organic solvent corrosion, but it is easy to oxidize at high temperature.