Bainite Transformation of Niobium Microalloyed Steel Under Isothermal and Continuous Cooling Conditions

By measuring hardness curves of isothermal transformation under different temperatures and expanding curves of continuous cooling transformation as well as the observation of microstructure,the TTT diagrams and CCT diagrams were obtained.The influence of strains on bainite transformation was researched under isothermal and continuous cooling conditions.The research results show that the bainite transformation is accelerated by strains under isothermal condition,the nose temperature of bainite transformation is 500 ℃,Bs is 600 ℃.The bainite starting temperature decreases with the increase of cooling rate and increases with the increase of strain under continuous cooling conditions.Bainite transformation is accelerated when deformed at 950 ℃ in the view of bainite starting temperature.