Graphite Electrodes: Full Breakdown of Raw Materials and Production Processes

2025-11-07 16:07:27

Graphite electrodes, these high-temperature resistant conductive materials, serve as essential components in electric arc furnace steelmaking!  They are primarily manufactured using petroleum coke and needle coke as the base materials, with coal tar pitch acting as the binder, through a series of complex technological processes. 1[2]^ Within electric arc furnaces, graphite electrodes play a critical role: they transmit electrical energy into the furnace, generating a powerful electric arc between the electrode tip and the furnace charge.  The intense heat from this arc melts the raw materials, facilitating the steelmaking process.  Beyond steel production, they are also vital in ore-smelting furnaces for producing phosphorus, industrial silicon, abrasives, and other materials. 

Regarding the raw materials:

‌Petroleum Coke:‌ Derived from the coking of petroleum residues and asphalt.  It is a black, porous solid primarily composed of carbon, with very low ash content, typically below 0.5%. 

Based on heat treatment temperature, it is classified into raw (green) coke and calcined coke. 1 Raw coke, obtained via delayed coking, contains high volatile matter and has low mechanical strength. Calcined coke is produced by roasting raw coke, resulting in superior quality. 

Classification by sulfur content includes high-sulfur coke (>1.5% S), medium-sulfur coke (0.5%-1.5% S), and low-sulfur coke (<0.5% S). 1 Graphite electrodes and other artificial graphite products are generally manufactured using low-sulfur coke due to its higher quality. 

‌Needle Coke:‌ Distinguished by its pronounced fibrous texture, exceptionally low coefficient of thermal expansion, and high graphitizability. 1 Its physical and mechanical properties are highly anisotropic: along the fiber axis direction, it exhibits excellent electrical and thermal conductivity, a low thermal expansion coefficient, and high thermal shock resistance. Needle coke is the key raw material for producing high-power (HP) and ultra-high-power (UHP) graphite electrodes.  It is categorized into oil-based needle coke (from petroleum residues) and coal-based needle coke (from refined coal tar pitch). 

‌Coal Tar Pitch:‌ A primary product of coal tar deep processing.  At room temperature, it is a black, highly viscous semi-solid or solid substance with no definite melting point; it softens and melts upon heating. 1 In the carbon industry, it serves as both a binder and an impregnating agent, significantly impacting the production process and quality of carbon products. 

‌Binder Pitch:‌ Typically requires medium softening point, high coking value, and high β-resin content (usually medium-temperature or modified medium-temperature pitch). 

‌Impregnating Pitch:‌ Should have a lower softening point, low Quinoline Insolubles (QI) content, and good rheological properties (usually medium-temperature pitch). 

In summary, the production process of graphite electrodes involves numerous intricate steps and meticulous raw material selection, which together ensure their high quality and widespread industrial application.