Extruded Graphite – A Multifunctional Material for Extreme Environments

  • Good chemical stability and high temperature resistance.
  • Excellent thermal and electrical conductivity.
  • High thermal shock resistance and high mechanical strength.
  • Great lubrication performance and low static charge.
Extruded graphite blocks and their manufacturing process

Extruded graphite is formed by mixing high purity graphite particles with a binder and then extruding them in an extruder. Compared with isostatic graphite, the extruded graphite has a coarser grain size and a lower strength, but it has a higher thermal and electrical conductivity.

Currently, most carbon and graphite products are produced by extrusion method. They are mainly used as heating elements and thermal conductive components in high-temperature heat treatment processes. In addition, graphite blocks can also be used as electrodes to carry out current transfer in electrolysis processes. Therefore, they are widely used as mechanical seals, thermal conductive materials and electrode materials in extreme environments such as high temperature, high pressure, and high speed.

Table 1: Specifications of Extruded Graphite
Model Density (g/cm3) Particle Size (mm) Specific Resistance (μΩ.m) Porosity Shore Hardness Compressive Strength (MPa) Flexural Strength(MPa) CTE (×10-6 °C-1) Application
GE-1 1.72 0.8/2.0 7.5 35 14 2.4 Electrode/rotors & shafts
GE-2 1.60 0.8/2.0 9.5 25 10 2.9 Electrode/rotors & shafts
  • 1 MPa = 10.2 kgf/cm2; 1 W/m.k = 0.86 kcal/cm.h.°C
  • These properties are typical values and not guaranteed.
Molding Technology

The extrusion method is to load the paste into the paste cylinder of the press and extrude it. The press is equipped with a replaceable extrusion ring (can be replaced to change the cross-sectional shape and size of the product) in front of it, and a movable baffle is provided in front of the extrusion ring. The main plunger of the press is located behind the paste cylinder.

Before applying pressure, place a baffle before the extrusion ring, and apply pressure from the opposite direction to compress the paste. When the baffle is removed and pressure is continued to be applied, the paste is extruded from the extrusion ring. Cut the extruded strip into the desired length, cool and inspect it before stacking. The extrusion method is a semi-continuous production process, which means that after a certain amount of paste is added, several (graphite blocks, graphite materials) products can be continuously extruded.

Currently, most carbon and graphite products are produced by extrusion method.

The picture shows the working principle of extrusion in details.