Dynamic Recrystallization Behaviors And Numerical Simulation Of12Cr2Ni4A Steel

12Cr2Ni4A steel was used as the research object in this paper. Isothermalcompressing tests were conducted on the Gleeble-1500hot-simulator at strainrates of0.01~10s-1and temperatures of950~1100℃. True stress-true straincurves at various deformation parameters were drawn on the basis of deformationdata which were analyzed to be with obvious dynamic recrystallization feature,and the flow stresses raise with the raise of strain rates and the reduction oftemperatures.Based on the Arrhenius equations, the flow stress hyperbolic constitutivemodel was established which could accurately represent the variety of flowstresses of12Cr2Ni4A steel in hot compressing deformations. Based on thedynamic materials model theory, the hot processing maps were drawn in whichthe high dissipation rates are in the range of temperatures of1010~1060℃andlow strain rates, processing unstability is in the range of temperatures of1020℃below or1070℃above and high strain rates, and in the unstability zones thedissipation rates are all low.Based on the dynamic recrystallization (hereinafter as DRX) theory, theDRX critical strain model, volume fraction model and grain size model of12Cr2Ni4A steel in hot deformation were established. By the analysis of testsdata and optical microstructure, it was showed that the DRX critical strains raisewith the raise of strain rates and the reduction of temperatures, the DRX volumefractions raise with the raise of strains, the raise of temperatures and thereduction of strain rates, the DRX grain sizes raise with the raise of strains, theraise of temperatures and the reduction of strain rates.Embedding the flow stress constitutive model and DRX models to Deform-3D to conduct the isothermal forging numerical simulations for12Cr2Ni4A steel,it was found that the refining effect strengthens with the raise of strains, strengthens with the reduction of strain rates and temperatures where thehomogeneity would worsen, the experiments and calculations of DRX volumefractions and average grain sizes are very similar which proves the accuracy ofmodels.Non-isothermal forging numerical simulations were conducted, by trial andcompare,1150℃and2s-1was considered to be the relatively ideal forgingtechnical parameters for grain refining which moreover meets the requirementsof hot processing maps. And the practical forging experiment was conducted atthis ideal parameters. Based on the cellular automata theory, the DRXmicrostructure evolution numerical simulation was also conducted at the idealparameters to obtain the microstructure evolution laws of various deformationzones, and the simulation results and practical forging results of same zones arevery similar which proves the accuracy of models.