Bainitic transformation during the two-step quenching and partitioning process in a medium carbon steel containing silicon

A study of 40SiMnNiCr steel subjected to a two-step quenching and partitioning process (Q&P) is presented. The result suggests that strength variation of Q&P steels during the two-step Q&P process was a cumulative effect of increase of retained austenite fraction, decrease of carbon supersaturation of virgin martensite, and particularly much of lower bainite formation. A trade-off between high strength and good ductility of two-step Q&P steels can be tailored and adjusted by controlling lower bainite fraction. The final amount of austenite was influenced by the transformation kinetics of lower bainite during the partitioning process. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.