High temperature resistance: the melting point of graphite is 3850±50℃, the boiling point is 4250℃, even after the ultra-high temperature arc burning, the component loss is very small, the coefficient of thermal expansion is very small. The strength of graphite increases with the progress of temperature. At 2000℃, the strength of graphite doubles.

Electrical and thermal conductivity: the electrical conductivity of graphite is one hundred times higher than that of ordinary non-metallic ore. The thermal conductivity is higher than steel, iron, lead and other metal materials. The thermal conductivity decreases with increasing temperature, even at extremely high temperatures, graphite becomes an adiabatic. Graphite conducts electricity because each carbon atom in graphite forms only three covalent bonds with other carbon atoms, and each carbon atom still retains one free electron to carry charge.

Smoothness: The smooth function of graphite depends on the degree of graphitization. The better the degree of graphitization, the smaller the friction coefficient, the better the smooth function. Chemical stability: graphite has good chemical stability at room temperature, and can resist acid, alkali and organic solvent corrosion.

Plasticity: when graphite is used at room temperature, it can withstand the dramatic change of temperature without damage. When the temperature changes rapidly, the volume of graphite changes little and will not produce cracks.

In the design and processing of vacuum furnace, it is necessary to consider that the resistance of electric heating element changes little with the temperature, and the resistivity is stable, so graphite is taken as the preferred material.