Challenges with design and processing of carbide-free bainitic AHSS sheets

Superior AHSS sheets are required for the manufacture of light weight body-in-white components to address stringent safety and fuel economy regulations. Carbide free bainitic (CFB) sheets are potential candidate steels with mechanical properties exceeding current commercial TRIP and DP steels. The main challenge is to develop suitable alloy compositions which can be processed by existing continuous annealing or galvanizing lines. This study describes proper processing routes for the manufacture of CFB sheets and presents alloying strategies to tailor the phase transformation response of potential candidate steels. Some examples of CFB alloy systems with tensile strengths between 1200 to 1500 MPa which have been optimized for different processing lines will be demonstrated and discussed.