The melting point of graphite rod

Graphite rod is the electric heater commonly used in high temperature vacuum furnace. It oxidizes easily at high temperatures. Except for vacuum, it can only be used in a neutral or reducing atmosphere. It has the characteristics of small thermal expansion coefficient, large thermal conductivity, high temperature resistance, extremely cold and hot, low price and so on. The oxidation rate and volatilization rate of graphite affect the service life of the heat generator. When the actual space is 10-3 to 10-4 MMHG, the use temperature should be lower than 2300℃. In the protective atmosphere (H2, N2, AR, etc.), the use temperature can reach 3000℃. Graphite can not be used in the air, otherwise it will be oxidized and consumed. It reacts strongly with tungsten to form carbides above 1400℃.

Graphite rods have a high melting point. Under vacuum conditions, when the temperature reaches 3000 ° C, it begins to soften and tends to melt. At 3600 degrees Celsius, graphite begins to evaporate and sublimate. The strength of general materials gradually decreases at high temperatures. However, when graphite is heated to 2000°C, it is twice as strong as at room temperature. However, the K oxidation of graphite is poor, and the oxidation rate increases gradually with the increase of temperature.

Graphite has high thermal and electrical conductivity. Its electrical conductivity is 4 times higher than stainless steel, 2 times higher than carbon steel, and many times higher than general non-metallic materials. Its thermal conductivity not only exceeds steel, iron, lead and other metal materials, but also decreases with the increase of temperature, which is different from general metal materials. Graphite is even adiabatic at extremely high temperatures. Therefore, the thermal insulation performance of graphite under ultra-high temperature conditions is very reliable.

Processing speed: the processing speed of general graphite is 25 times faster than that of copper; The EDM machining speed is 2 to 3 times that of copper machining speed. The material is not easy to deform: the processing of thin-rib electrodes has obvious advantages: the softening point of copper is relatively high, and it is easy to deform when heated; The sublimation temperature of graphite is 3650℃. The coefficient of thermal expansion is only 1/30 of copper.

Light weight: the density of graphite is only 1/5 of copper. The use of large electrode for EDM can effectively reduce the burden of machine tools. More suitable for large mold applications. It is because of its density that graphite is lighter and easier to produce.