Isostatic Graphite – Special Graphite with High Thermal Conductivity

  • Extremely high thermal and chemical resistance.
  • Excellent thermal shock resistance and oxidization resistance
  • High electrical and thermal conductivity.
  • Can be used for precision machining.
  • Low impurity content, high purity (< 5 ppm).
Isostatic graphite blocks and their manufacturing process

Isostatic graphite, made of high purity graphite by pressing, is an irreplaceable material used in the manufacturing of single crystal furnaces, metal continuous casting graphite crystallizers, and graphite electrodes for electrical spark discharge machining. In addition to these main applications, it is widely used in the fields of hard alloys (vacuum furnace heaters, sintering plates, etc.), mining (manufacturing of drill bit molds), chemical industry (heat exchangers, corrosion-resistant parts), metallurgy (crucibles), and machinery (mechanical seals).

Table 1: Specifications of Isostatic Graphite
Model Density (g/cm3) Particle Size (μm) Specific Resistance (μΩ.m) Porosity Shore Hardness Compressive Strength (MPa) Flexural Strength (MPa) CTE (× 10-6 °C-1) Application
IS-2(Isostatic) 1.76 20 15 20% 60 95 50 5.9 Heat exchanger/all kinds of machining
IS-3(Isostatic) 1.85 10 12 13% 48 85 46 4.3 Sintering/all kinds of machining
IS-4(Isostatic) 1.90 5 12 13% 48 85 46 4.3 Sintering/all kinds of machining
ED-1(Isostatic) 1.83 9 12 12% 65 116 51 5.8 EDM, semi finishing/finishing
ED-2(Isostatic) 1.81 7 12 12% 69 135 62 6.8 EDM, semi finishing/finishing
ED-3(Isostatic) 1.90 5 12 12% 69 135 62 6.8 EDM finishing, ultra fine grain for low electrode wear
ED-4(Isostatic) 1.92 3 11 11% 72 160 69 6.9 EDM finishing, lowest electrode wear
  • 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 principle of isostatic pressing technology is based on Pascal's law. It changes the unidirectional (or bidirectional) compression of the material into multi-directional (omnidirectional) compression. During the process, the carbon particles are always in a disordered state, and the volume density is relatively uniform with isotropic properties. Besides, it is not subject to the height of the product, thus making the isostatic graphite have no or little performance differences.

According to the temperature at which the forming and solidification take place, isostatic pressing technology can be divided into cold isostatic pressing, warm isostatic pressing, and hot isostatic pressing. Isostatic pressing products have a high density, typically 5% to 15% higher than those of unidirectional or bidirectional mold pressing products. The relative density of isostatic pressing products can reach 99.8% to 99.09%.

The working principle of cold isostatic pressing and hot isostatic pressing