High strength-elongation product of Nb-microalloyed low-carbon steel by a novel quenching-partitioning-tempering process

In this article, a novel quenching-partitioning-tempering (Q-P-T) process was applied to a Fe-0.25C-1.5Mn-1.2Si-1.5Ni-0.05Nb (wt%) hot-rolled steel, and its optimized parameters were obtained by a Gleeble-3500 thermal simulator and salt baths, respectively. Mechanical property results of the astreated Q-P-T samples show that the Nb-microalloyed low-carbon steels subjected to Q-P-T processes cover a wide spectrum of strength (1200-1500 MPa) and elongation (14-18%), and exhibit excellent product of strength and elongation (21,000-22,000 MPa%). Microstructural characterization indicates that high strength results from dislocation-type martensite laths and dispersively distributed fcc NbC or hcp epsilon-carbides in martensite matrix and good ductility is attributed to transformation induced plasticity (TRIP) effect from plenty of retained austenite flakes between martensite laths. (C) 2011 Elsevier B.V. All rights reserved.