Abstract
This paper describes the development of alloy cast iron that can be used for the cutting edges of the trimming die of a press die. Usually, a block of tool steel or steel casting is inserted at the cutting edge of the trimming die of a press die. However, we unified the structure part and the cutting-edge part of a press die with alloy cast iron. As it can't bear as the cutting edge in this state, the cutting edge is processed by flame-hardening. After the flame-hardening, we developed the alloy cast iron so that enough hardness may be obtained by natural air-cooling. Thereby, the machining of the installation seat of the cutting edge decreased and the expense of dies has been reduced.