A Tailored Tempering Process for CSC-15B22 Steel Sheet

The simulation and experimental methods are used to determine the parameters of a tailored tempering process for a lab-scale B-pillar that is made from CSC-15B22 high-strength steel. The finite element software, DEFORM-3D, is used to simulate the tailored tempering process. A segmented hot stamping tool is developed for testing. Results demonstrate that the cooling and heating systems are successful. On the cooled side of the tooling, the cooling rate for the sheet is more than 30 °C/s. The material structure of the sheets is entirely a martensite structure, which results in an ultra-high strength material. The average hardness is measured as HV423, which translates to a tensile strength of 1350 MPa. On the heated side of the tooling, the cooling rate for the sheet is less than the critical cooling rate, the microstructure of the material is ferrite and pearlite, and the average hardness is measured at HV205, which translates to a tensile strength of approximately 660 MPa. The study demonstrates that a tailored tempering process allows production using integrated tooling and produces sheets that have different mechanical properties.