Fineblanking of high strength steels: Control of material properties for tool life

In order to assess the possibility of fineblanking high strength steels while preserving acceptable tool lifetimes, materials with a wide range of ultimate tensile strengths (200–1500 MPa) were fineblanked experimentally and simulated with finite element modeling. Good agreement was achieved and a refined relationship between cutting force and material strength was discovered. The strain at which the cutting force is maximized was shown to be several times greater than the uniform tensile strain, suggesting the concept of manipulating material strain hardening properties to increase material strengths markedly while maintaining acceptable tool stress levels and thus lifetimes. The concept was shown viable using finite element simulations. The results show the need for steels optimized for fineblanking applications. They will have almost opposite properties of advanced high strength steels, which are optimized for sheet formability by increasing their strain hardening at large strains.