Graphite-copper composite electrode material and electrical discharge machining electrode using the material

An electrical discharge machining electrode, the electrical discharge machining electrode characterized by comprising a graphite-copper composite electrode material comprising a substrate;

• wherein the substrate comprises a graphite material and has pores;
• and copper, wherein the copper is impregnated in the pores of the substrate to thereby form the graphite-copper composite electrode material, wherein the graphite-copper composite electrode material has an electrical resistivity of up to 2.5 μΩm;
• and
• wherein an impregnation rate φ of the copper in the graphite-copper composite electrode material is 13% or greater, the copper impregnation rate φ obtained by the following equation (1):
• φ=[(dB−dB,s)/ρCu]×100, (1)
• wherein dB is a bulk density of the electrode material, dB,s is a bulk density of the substrate comprising the graphite material, and ρCu is the specific gravity of copper, which is ρCu=8.96 Mg/m3;
• and
• wherein the electrical discharge machining electrode is for use in die-sinking a cemented carbide comprising tungsten carbide as a main component by electrical discharge machining.

A graphite-copper composite electrode material comprising:

• a substrate;
• wherein the substrate comprises a graphite material and has pores;
• and copper, wherein the copper is impregnated in the pores of the substrate to thereby form the graphite copper composite electrode material,
• wherein the graphite-copper composite electrode material has an electrical resistivity of up to 2.5 μΩm, and
• wherein a variable x obtained by the following equation (2) is 7.5 or less:
• x=(dB×φ×ρ/σB)×10 (2)
• dB is a bulk density (Mg/m3) of the electrode material, φ is a copper impregnation rate (%), ρ is an electrical resistivity (μΩm), and σB is a flexural strength (MPa).