Abstract: Press hardening of higher carbon ultra-high strength steels is attractive because of the potential to reduce vehicle weight while maintaining occupant protection during crash. Tempering of this fully martensitic material could be used to increase the local ductility within a structural component for enhanced crash performance. In this work, an 1800 MPa grade of press hardening steel was fully quenched in a Gleeble Thermal-Mechanical Simulator to produce a fully martensitic microstructure. This material was then subjected to tempering at a variety of temperatures ranging from 100 to 700°C and a tempering hold time of 1 and 15 s. For the greatest tempering temperature of 927°C and a 15 s hold, the hardness reduced from a maximum hardness of 575 to 300 HV1000, which represents a 48% reduction. An FE-SEM was used to generate high resolution micrographs of the tempered microstructures, which revealed the effect of tempering time and temperature on the precipitation behavior of carbides for this class of steel.
Authors: Claire Bourque, Alexander Bardelcik, Constantin Chiriac, and Mary Wells
Keywords: Tempering, Press Hardening Steel, Martensitic Microstructure