Desing System
To that end, plane compression tests were performed, consisting of an initial preconditioning step, followed by several roughing and finishing deformation passes and a final quenching step. After fast cooling to room temperature, a tempering treatment was applied. In the present paper, the complex interaction between the martensitic microstructure, the tempering treatment, the addition of microalloying elements, and the resulting tensile properties was evaluated. For that purpose, an exhaustive EBSD quantification was carried out in both quenched as well as quenched and tempered states for all the steel grades and the contribution of different strengthening mechanisms on yield strength was analyzed. Highest tensile properties are achieved combining Nb and Mo, for both quenched (Q) and quenched and tempered states (Q&T), reaching yield strength values of 1107 MPa and 977 MPa, respectively. Higher tempering resistance was measured for the Mo-bearing steels, making the CMnNbMoB steel the one with the lowest softening after tempering. For CMnB grade, the yield strength reduction after tempering of about 413 MPa was measured, while for NbMo micro-alloyedsteel, yield strength softening is considerably reduced to 130 MPa.