Hot-formed steels


    The so-called press hardening method is used for reinforcement parts to achieve extremely high strength. In this process, a conventional boron steel is heated to about 880 to 950° C (1620 to 1740º F), formed hot and then cooled, i.e. hardened, in the die. The hardening process is performed in the die to minimize any warping of the component.
    Unhardened boron steels demonstrate a tensile strength of about 600 N/mm² and a 20% elongation at failure. Hardened boron steels achieve up to  1650 N/mm² at a residual elongation at failure of the finished component of up to 8%. Designation: 22MnB5, BTR 1650, Usibor 1500.
    Currently, press hardening is the only manufacturing method for such high-stength components. Due to the long cycle times and the high energy costs the use of press hardening should be decided case-by-case depending on the component and the vehicle class.  
    It is difficult to predict how high the number of hot-formed components will find use in vehicles. In the current VW Passat there are now, for example, eleven such parts.