Mechanism-driven fine blanking of high manganese steels

Fine blanking is used in industrial processes for mass production of high accuracy sheet metal parts. The process characteristic leads to a strain hardening of the sheared surface. Utilization of the process-immanent surface hardening can reduce time and energy consumption of downstream heat treatment processes like case hardening. Substituting High Strength Low Alloy (HSLA) steels by High Manganese Steels (HMnS) increases strain hardening during fine blanking and may replace the necessary heat treatment. This work investigated the mechanism-driven behavior of HMnS (1.7401) during fine blanking and its influencing factors, changing the part properties. Based on a characterization of the material properties of HMnS, the influence of the initial sheet temperature, blanking velocity and blank holder force on the sheared surface hardening and quality was analyzed. Due to enhanced strain hardening of HMnS, higher surface hardness with softer core was achieved compared to S700MC (1.8974) HSLA-steel. In addition, the sheared surface hardening was increased by a decrease in blanking velocity and an increase in blank holder forces. Taking into account the alloy design, fine blanking of HMnS offers the potential to achieve a high sheared surface hardening by targeted activation of the deformation mechanisms with simultaneous high quality and strength.