Research On Flow Stress Behavior And Microstructure Evolution In High Temperature Of P91Steels

In order to study the heat resistant steel used in the environment of high temperature,researchers have developed heat resistant steel of different chemical composition, the best oneis P91/T91which the preferential material used as high temperature components. It’s mainlyused for long thick-walled tube boilers and steam pipes, turbine rotors and otherhigh-temperature sites. In overseas, P91large diameter thick-walled tube has beenmanufactured successfully, but the production capacity of our country is insufficient, and hasvery little research to this material. It is necessary to study the basic data and microstructureevolution of P91materials, then, master the deformation behavior under the high temperatureto provide the theory basis for the actual vertical extrusion production of large diameter thickwall long pipe.During the research we had a thermal simulation experiment by Gleeble-3500thermalsimulation test machine, got the high temperature flow strain-stress curves of P91material,and analyzed the experiment results and the metallographic experiments, the high temperatureflow strain-stress was used as a basic parameter of the numerical simulation. Using linearregression method to deal with thermal simulation and experimental data, obtainedmathematical model of dynamic recrystallization P91material. The result is that at hightemperature or low strain rates, dynamic recrystallization of P91heat-resistant steel occurredmore completely.Through grain growth experiments of P91materials and metallographic experiments,obtained the grain growth data in the different temperature and heat preservation time.Analyse the data by the method of regression and obtained grain growth mathematical modelof P91materials.Imported the dynamic recrystallization and grain growth mathematical model into thesoftware Deform-3D used for finite element analysis, simulated the hot compressiondeformation and scale-down extruded P91.The result verified the accuracy of dynamicrecrystallization and grain growth mathematical model, and got the law of average grain sizein the different extrusion ratio.The regular is that the extrusion ratio is bigger, the mechanicalproperties of thick wall pipe is better. It is shown that extrusion ratio within the scope of5~7is reasonable, and scale-down extrusion process test can provide the basis for practicalproduction.