Effect of Ti on microstructure and properties of Ti-Nb microalloyed high strength steels

摘要

Three Ti-Nb microalloyed high strength steels with varying Ti contents were refined in laboratory 50 kg vacuum induction furnace. Microstructure observation and TEM analysis were conducted. Tensile tests were performed. The results show that both yield strength and ultimate tensile strength increase with the Ti content, while the elongation has no significant change. The microstructures consist of bainite, ferrite and perlite, and microstructure morphology has no obvious difference. TEM analysis shows that the steel with higher Ti content contains more fine precipitates of (Ti, Nb)(C, N), indicating that precipitation strengthening is the main factor for the improvement of strength.