Graphitic steel with high machinability for cold forging --development of forging steel suited for recycling I

摘要

There is a possibility that free-cutting steel with lead will be prohibited in the near future due to environmental reasons. This paper proposes a recyclable graphitic steel which has high cold forgeability and high machinability. During annealing, the cementite in the steel transforms into graphite. The graphite in the steel exists as fine grains which have less resistance to deformation at room temperature, and this steel has higher machinability than free-cutting steel with lead. The flow stress level of this steel is as low as that of low carbon steel; as a result, good durability can be expected for the tools used in cutting the proposed steel after cold forging. In addition, the near net shaping of complex parts can be carried out easily using the steel. This steel can be quenched and hardened: and the high fatigue strength which is typical of carbon steels was observed.