The content of pure graphite is more than 99.9%. It is an ideal crucible for inorganic nonmetal, heater for single crystal furnace, graphite for EDM, sintering mould, anode for electronic tube, metal coating and graphite crucible for semiconductor technology. High purity graphite has special processed graphite, which has the characteristics of corrosion resistance, good thermal conductivity and low permeability.
Several advantages of high purity graphite products:
(1) High temperature resistance: the melting point of graphite is 385 + - ℃, and the boiling point is 4250 ℃. Even if the graphite is burned by high-temperature arc, the weight loss is very small, and the coefficient of thermal expansion is also very small. The strength of graphite increases with the increase of temperature. At 2000 ℃, the strength of graphite increases by - times. During the construction of exothermic welding, the chemical reaction temperature of igniting exothermic flux is very high, so the materials used in exothermic welding mould should be resistant to high temperature.
(2) Conductivity and thermal conductivity: the conductivity of high-purity graphite is 100 times higher than that of non-metallic minerals. Thermal conductivity is higher than steel, iron, lead and other metal materials. The thermal conductivity decreases with the increase of temperature. Even at higher temperatures, graphite becomes an insulator. Graphite can conduct 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 transmit charge. In the exothermic welding construction, many points need to be welded, and the construction is not small. The thermal conductivity of graphite can just meet this point, which can not only resist high temperature but also rapidly cool down.
(3) The larger the graphite flake, the better the lubrication performance.
(4) Chemical stability: graphite has good chemical stability at room temperature, and can be resistant to acid, alkali and organic solvent corrosion.
(5) Plasticity: high purity graphite has good toughness and can be rolled into thin sheets. Exothermic welding sometimes requires a variety of joint forms of exothermic welding dies. The plasticity of high-purity graphite can be made into various types, specifications and connection forms of exothermic welding dies.
(6) Thermal shock resistance: high purity graphite can withstand the drastic change of temperature without damage when it is used at normal temperature. When the temperature changes suddenly, the volume of graphite changes little and cracks will not occur.