Isostatic pressing graphite refers to the graphite material produced by isostatic pressing and is a graphite material developed on the basis of “three high graphite”. Isostatic graphite is also known as “isotropic” graphite because of its excellent properties, such as large molding size, uniform billet structure, high density, high strength and isotropy (the characteristics are independent of size, shape and sampling direction) due to the uniform and constant pressure of liquid pressure during the molding process.
The main raw materials for producing isostatic pressure graphite are petroleum coke, asphalt coke and coal tar pitch. Some overseas enterprises use mesophase carbon microspheres. Due to technical barriers, no domestic enterprise has chosen mesophase carbon microspheres as raw materials. Its downstream applications are distributed in semiconductor industry, atomic energy industry, EDM, continuous casting metallurgy industry, photovoltaic and other production fields.
The production of isostatic pressing graphite in China is mainly cold isostatic pressing technology, and its raw materials are petroleum coke and asphalt coke. Compared with China, the process of producing isostatic pressing graphite overseas is simpler, more automatic, lower cost and higher yield. However, overseas countries have imposed strict technical blockade on China, so its specific production raw materials and formula have been kept confidential to China.
Petroleum coke is the main aggregate for the production of isostatic pressure graphite. Generally, petroleum coke needs to be calcined at 1200-1400 ℃ to remove water and volatile. However, in order to improve the mechanical properties and structural compactness of the products, there are also direct production of isostatic graphite using raw coke as raw material. Coal tar pitch is used as a binder in the process of isostatic pressing graphite production. Different enterprises have different equipment conditions and process requirements, and have different requirements for the softening point of coal tar pitch, ranging from 50 ℃ to 250 ℃.
China is a net importer of isostatic graphite. With the increase of the size of silicon wafers, the size requirements of isostatic graphite are gradually expanded. However, the production capacity of domestic high-end isostatic graphite products is insufficient, so the demand for overseas imports remains high and the dependence on imports remains high. However, at present, the substitution effect of carbon matrix composites in silicon thermal field weakens the demand for isostatic pressing graphite in single crystal furnace, so the output and import of isostatic pressing graphite are limited.
The downstream consumption of isostatic graphite is mainly concentrated in photovoltaic and semiconductor fields, accounting for 67% of the total application of isostatic graphite; The second demand is in the field of EDM, accounting for about 14%.