from the conferences organized by TANGER Ltd. provisional website
High strength multiphase TRIP steels are very often used as structural materials, especially in the automotive industry. Due to their ability to absorb energy during the impact, they are used for safety components of the car body. These parts can be produced by a hot stamping process, which has the advantage of using lower forming forces and a smaller spring back effect. The problem during heat treatment of TRIP steels is the holding time in the region of bainitic transformation, which facilitates bainite formation and stabilization of retained austenite.In the present study, two low-alloy TRIP steels with and without niobium were chosen. Physical simulation was employed to test an alternative route without an isothermal hold during cooling after hot stamping. Several continuous cooling profiles from the tool temperature were applied. The results were compared with isothermal processing in the region of bainitic transformation. Mixed structures consisting of bainite, martensite, ferrite and retained austenite were obtained for both steels. The ultimate strength reached more than 900 MPa with the elongation A20mm over 15 %.Keywords: TRIP steel, niobium, continuous cooling, retained austenite
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