低温プラズマ窒化金型の創製と電磁鋼板のゼロクリアランス打抜きへの展開

抄録

A plasma-nitrided SKD11 punch-die pair was developed for the fine piercing process under nearly zero clearance. A high-density plasma-nitriding system was utilized to nitride the SKD11 punch to have a surface hardness of up to 1600 HV. The annealed SKD11 die substrate was shaved into a core die by accurate piercing with this nitrided punch. After the shaping and plasma nitriding of the shaved core die, both the punch and core die were placed into the cassette die set for piercing experiments under nearly zero clearance. Electromagnetic steel sheets with a thickness of 0.5 mm were prepared to describe the shearing behavior in piercing. The piercing load and stroke histories were measured with increasing number of shots. The engineering durability was also discussed to describe the wear of the punch and die. Fine piercing with smaller burr heights and fractured surface area ratios under the dry condition was put into practice using the plasma-nitrided punch and die-core set with rational compliance under nearly zero clearance.