Study On Recrystallization And Phase Transformation Kinetics Of HRB400 Hot Rolled Bars

In this paper,hot rolled bars(HRB400)as the experimental object,through literature analysis and experimental research,analysis of different holding time under different temperature.The microstructure evolution and recrystallization behavior,the hot rolling thread steel transformation kinetics and recrystallization kinetics equation,provides a theoretical basis for establishing the organization forecast system.By using the thermal analysis method and the expansion method combined with the CCT curve of hot rolled bars,through experimental analysis,when the cooling rate is lower than 3?/s,the final product for the cooling of ferrite and pearlite,when the cooling rate is 3~8?/s,bainite cooling products,when the cooling rate 8~15?/s,appeared Martensite Start cooling products,with the increase of cooling rate,the hardness of the material is also rising.According to the phase change point under different cooling rates,the CCT curve of the steel is drawn,which provides the basis for the isothermal quenching experiment.In order to obtain steel recrystallization kinetics equation,this paper machine simulation of single pass and double compression tests by Gleeble thermal simulation,to simulate the process of dynamic recrystallization and static recrystallization,the dynamic recrystallization,by fitting curve to calculate the activation energy Q=283.3854KJ/mol,recrystallization kinetics equation and dynamic,by two differential calculation of critical strain and deformation velocity under different temperature,and provide a theoretical basis for the static recrystallization.For static recrystallization,below the critical strain calculated in the case of different time interval under a softening rate,calculation of t0.5expression,finally established the static recrystallization kinetics equation.In order to establish the parameters of the dynamic equation of the phase change of the steel bar,the isothermal quenching experiment was carried out on the basis of the CCT curve of the steel.Determination of ferrite by CCT curve(600~730?),pearlite(470~580 ?),bainite(350~450?)change interval,different holding time(1~15min),calculated under different temperature phase transformation volume fraction,with theincrease of the holding time,phase volume fraction is also increasing,determination of ferrite,the pearlite,bainite transformation kinetics equation through linear fitting.