A bainite-ferrite multi-phase steel strengthened by Ti-microalloying

Abstract

Ti-microalloyed bainite multi-phase steels were prepared in laboratory scale. The tensile strength of examined steels are all higher than 775 MPa and the maximum value is 875 MPa, with at least 27 J impact energy at 253K which shows a good balance of high strength and high toughness. The examined steels have uniform and fine multi-phase structure with bainite as main phase and ferrite as minor phase, the ratio of ferrite phase gradually decreases with the cooling speed of post-rolling increasing. Most of the precipitates are nano scaled particles of TiN and TiC, which disperse at grain boundaries, dislocations and other places, having effect of grain refinment strengthening and precipitation strengthening. © 2011 The Japan Institute of Metals.