Special Graphite – Various High Performance Industrial Materials

Special graphite is a high purity, high density and high strength graphite material and has excellent corrosion resistance, high temperature stability and great electrical conductivity. It is made of natural or artificial graphite after high temperature heat treatment and high pressure processing and is commonly used in industrial applications in high temperature, high pressure and corrosive environments.

It can be divided into various types including isostatic graphite blocks, extruded graphite blocks, molded graphite blocks and vibrated graphite blocks.

Special graphite blocks made of different forming technologies
Manufacturing Technologies

Graphite is a unique non-metallic element composed of carbon atoms arranged in a hexagonal lattice structure. It is a soft and brittle material that is commonly used in various industrial applications due to its unique properties. Graphite can maintain its strength and stability even at temperatures exceeding 3600 °C. Now let me introduce the production process of special graphite.

The production and processing steps of special graphite
  • Step 1 Raw material preparation. Solid raw materials (petroleum coke, pitch coke, carbon black, natural graphite, etc ) are mixed by a certain proportion and then loaded into raw material troughs.
  • Step 2 Crushing& grinding. The mixed materials are ground into powder by crusher and ball mill and then sieved.
  • Step 3 Binder addition. Pitch is often used as a binder. Carbonaceous pitch (coal tar pitch, etc.) is added to the sieved material in a certain proportion. The pitch serves to increase the adhesion and plasticity, which helps the mixture to maintain a certain shape and size during the molding process.
  • Step 4 Material mixing. Mix the ground and sieved materials with carbonaceous pitch (coal tar pitch, etc.) evenly for further processing.
  • Step 5 Forming process. The mixture is compressed and shaped through different processes (extrusion, molding, vibration, isostatic pressing).
  • Step 6 Carbonization process. The compacted material is heated under anaerobic conditions at a temperature of 800 °C to 1200 °C, forming a solid block and this process is called carbonization process.
  • Step 7 Pitch impregnation. It can further reduce the porosity of the product, enhance the density and compressive strength, lower the electrical resistivity of the finished product, and change the physical and chemical properties of the product. It should be noted that after impregnation, a second calcination is required to carbonize the pitch.
  • Step 8 Graphitization. It is a high-temperature heat treatment process in which amorphous disordered layer structured carbon is converted into a three-dimensional ordered graphite crystal structure at 2500 °C to 3000 °C. It can eliminate impurities and improve product performance.
  • Step 9 Processing. Check all graphite properties (grain size, density, bending and compressive strength) and carry out processing.
  • Step 10 Purification process. If used in semiconductor, monocrystalline silicon and atomic energy industries, the materials require high purity and must remove all impurities by chemical methods. That is, put the graphite products in a halogen gas and heat them to 2700 °C. At Xuran, we have the capacity to purify ash content to 5 ppm, far surpassing our peers.
  • Step 11 Coating treatment. Depending on the application of graphite, the surface can be treated to make it smoother, for example, apply a silicon carbide coating on the surface at 1200 °C.