Research On Hot Deformation Behavior And Microstructure Evolution Of Ultra-High Carbon Steel

Ultra-high carbon steel has extremely high strength,hardness and wear resistance,but it is prone to appear cracks and other defects during hot deformation with the increase of carbon content,which affects the performance and application of ultra-high carbon steel.In this paper,the hot compression tests of ultra-high carbon steel of Fe-1.3C-5Cr-0.4Mo-0.4V were carried out by Gleeble-3500,then the stress-strain curve,micro structure evolution and dynamic recrystallization were studied at various temperature,strain rate and reduction with the characterization method of SEM,TEM and EBSD.Furthermore,the finite element models of hot compression and hot rolling were established based on the achieved constitutive equation and dynamic recrystallization model,and the results could be as a theoretical basis for recommendation of practical production.The main conclusions obtained in this study are as follows:?1?The flow stress curves of Fe-1.3C-5Cr-0.4Mo-0.4V were analyzed at the deformation temperature of 950?^-1150?,the strain rate of 0.01 s^-1?5 s^-1 and the strain of 0.511.The constitutive equation of the material was obtained and it can accurately describe the behavior of hot deformation.The activation energy?Q?of ultra-high carbon steel is 729.37 kJ/mol,indicating that the steel needs high temperature and large stress for recrystallization?2?The dynamic recrystallization model of Fe-1.3C-5Cr-0.4Mo-0.4V steel was established by analyzing the micro structure of Fe-1.3C-5Cr-0.4Mo-0.4V at different thermal deformation conditions.The grains in the strain-deformed structure are uniform and fine,and dynamic recrystallization is more likely to occur at the high strain.Combined with the results of TEM and EBSD,the dynamic recrystallization mechanism of the experimental steel is clarified?3?The finite element models of isothermal and non-isothermal forging and hot rolling process were established based on constitutive equation and dynamic recrystallization model of the experimental steel.It shows that the fine grain structure can be obtained with hot forging at T=1050?^-1100? and ?=1 s^-1 and hot rolling at T=1150? and ?=5 s^-1,which is beneficial to obtain high mechanical properties of the steel.