Synergistic effects of carbon content and Ti/Mo ratio on precipitation behavior of HSLA steel: Insights from experiment and critical patent analysis

Abstract

A one-step heat treatment comprising isothermal holding in the two-phase region for different time periods and subsequent quenching contributed to the development of a ferrite and martensite dual-phase structure in TiMo microalloyed steels with different carbon and microalloying element contents. Irrespective of the Ti/Mo atomic ratio, a dual precipitate morphology, namely interphase precipitation and random precipitation, was found in the ferrite matrix. Furthermore, under the fixed carbon content, harder ferrite grains were obtained in the steel with a high [Ti]/[Mo] atomic ratio. This could be explained by the fact that a large volume fraction of tiny-sized carbides formed within the ferrite matrix when the [Ti]/[Mo] atomic ratio was increased. In addition, several microalloyed steels with different [Ti]/[Mo] atomic ratios listed in highly-cited patents were also retrieved and analyzed to support the above deduction. Keywords: Steel, Precipitation, TEM, Ti/Mo, Microhardness, Patent analysis