It was attempted that copper-graphite composite was prepared only on the surface of a copper plate using a spot welding machine. Experiments were carried out with changing the compressive load, the repetition number of the compression and the electrical current in order to study their effects on carbon content and Vickers hardness of the composite. Generally, the carbon content of the composite prepared without an electrical current flow was smaller than that prepared with an electrical current flow. The former composite was prepared with that relatively small angular graphite particles were pushed into the copper plate. In the case of flowing electrical current, graphite particles was heated, and partially or wholly dissolved into molten copper. Therefore, the latter composite was prepared with undissolved graphite and precipitated graphite from the copper melt. In addition, the Vickers hardness of the copper matrix in the composite prepared without an electrical current flow was larger than that prepared with an electrical current flow, because energization heated and annealed the composite. The Vickers hardness of the copper matrix in the composite and the volume fraction of graphite were expressed by the rule of mixtures.
