| 摘要 |
PROBLEM TO BE SOLVED: To obtain a metal mold of long life which can be used for continuously punch processing a thick steel plate or the like for long time by applying an electric discharge surface hardening treatment for forming a hard ceramics coating at a cutting blade portion of the mold or at a contacting portion with the plate material after the mold material is roughly processed for performing a heat treatment of quenching, tempering so as to apply a finish cut processing such as a turning cut. SOLUTION: After a rough processing such as punching is applied to a metal mold material, a quenching, tempering heat treatment is performed. Then, the mold material is finished in high measurement accuracy by applying a finish processing. An electric discharge surface treatment is performed for forming a hard ceramics coating by using electrodes suitable for shapes of portions to be hardened such as a cutting blade portion of the mold for a punch and a die, or a portion where the mold is brought into contact with the plate material at the time of processing. In addition, quality inspection is carried out. Since a hardening treatment is applied to the surface of the mold with the electric discharge surface treatment, rigidity HV is made, for example, to be at 2,500-3,000 and, a coating strength at a tip of the blade is high. Even when a punch processing is performed, seizing or a break away is not taken place on the mold, and pitching is not generated either. Mold life is thus improved.
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