Detailed analysis of heating principle of graphite rod
Graphite rod is often used as the electric heater of high-temperature vacuum furnace. It is easy to oxidize at high temperature. Except for vacuum, it can only be used in neutral atmosphere or reducing atmosphere. It has small coefficient of thermal expansion, large thermal conductivity, high temperature resistance, extreme cold and extreme heat resistance, and low price. The oxidation rate and volatilization rate of graphite affect the service life of the heat generator. When the true space is 10-3 ~ 10-4 mmHg, the service temperature should be below 2300 ℃. In the protective atmosphere (H2, N2, AR, etc.), the service temperature can reach 3000 ℃. Graphite cannot be used in air, otherwise it will be oxidized and consumed. It reacts strongly with W above 1400 ℃ to form carbides.
The graphite rod is mainly composed of graphite, so we can also understand the characteristics of graphite:
The melting point of graphite is very high. It begins to soften and tend to melt when it reaches 3000C under vacuum. At 3600c, graphite begins to evaporate and sublimate. The strength of general materials gradually decreases at high temperature. However, when graphite is heated to 2000c, its strength is twice that at room temperature. However, the oxidation resistance of graphite is poor, and the oxidation rate gradually increases with the increase of temperature.
The thermal conductivity and conductivity of graphite are quite high. Its conductivity is 4 times higher than that of stainless steel, 2 times higher than that of carbon steel and 100 times higher than that of general non-metal. Its thermal conductivity not only exceeds that of metal materials such as steel, iron and lead, but also decreases with the increase of temperature, which is different from general metal materials. Graphite even tends to be adiabatic at extremely high temperature. Therefore, the thermal insulation performance of graphite is very reliable under ultra-high temperature conditions.
Finally, we can conclude that the heating principle of graphite rod is: the greater the current added to the graphite rod, the higher the surface temperature of the graphite rod.
Post time: Oct-28-2021