Phase Transformation and Second-phase Precipitation Behavior of Nb-Ti Microalloyed Steel during Cooling after Deformation

The phase transformation behavior of Nb-Ti microalloyed steel during cooling process after deformation was studied by the Gleeble-2000 thermomechanical experiment simulator and by means of a combined method of microscopic hardness measurement.In addition,both second-phase precipitation behavior during cooling after deformation and the effect of cooling rate on the second-phase precipitation were studied by the carbon extraction replicas technique.The results show that there a lot of fine dispersed particles which are main Nb-Ti carbonitride phase are precipitated.The shape of the secondary phase particles is general like square、elliptical、circular shape and irregular shape.With the cooling rate increasing,the second-phase precipitation particles are seen to have become finer and the number of them are increasing.