Research On The Dynamic Recrystallization Behavior And Cellular Automaton Simulation Of X12 Steel For Ultra-supercritical Rotor

X12(X12Cr Mo WVNb N10-1-1)alloy steel is an important material for the production of ultra-supercritical rotors.It contains various alloy elements such as Cr,W,V,Nb,etc.And it has good hardenability and excellent mechanical properties.The rotor is the core component of the ultra-supercritical generator set,and its working environment is usually an ultra-high temperature and ultra-high pressure environment.And the production quality of rotors can directly affect the service life and service performance of the ultra-supercritical generator set.One of its technical bottlenecks is the difficulty of manufacturing ultra-supercritical rotors.In the hot working process,not only the shape of forgings should be controlled,but also the internal structure of forging must be uniform,and the grains must be refined to ensure good overall performance.Dynamic recrystallization behavior is an important factor to refine grains and improve microstructure properties during hot manufacturing of forgings.Therefore,studying the dynamic recrystallization microstructure evolution mechanism of large forging materials during hot deformation is of great significance for the manufacture of ultra-supercritical rotors.This article takes X12 alloy steel as the research object,and conducted experimental research through hot compression test,XRD test,and metallographic test.The data obtained through the test was used to build flow stress model and determine hot deformation activation energy.And then the cellular automaton model of X12 alloy steel was established through the obtained parameters and the program was compiled.The cellular automaton simulation program was used to simulate the dynamic recrystallization microstructure evolution process of X12 alloy steel during hot deformation.The different hot deformation conditions and initial grain size were studied for the dynamic recrystallization microstructure evolution process.In addition,a cellular automata simulation program considering topological deformation technology was written,and the influence of topological deformation process on the evolution process of dynamic recrystallization microstructure was studied.A Gleeble-1500 D thermo-mechanical simulator was used to perform a hot compression deformation test on a ?8 mm × 12 mm cylindrical specimen.And in order to obtain the initial microstructure of the X12 alloy steel before dynamic recrystallization began,the specimen was maintained at different temperatures.Based on the true stress-strain data obtained from the hot compression test,the hot deformation behavior of X12 alloy steel was analyzed,and the Arrhenius flow stress model that reflects its hot deformation behavior was established and flow stress model and determine hot deformation activation energy used in the simulation were obtained.Through XRD Diffraction test,the dislocation density change law of X12 alloy steel under different deformation conditions was studied,the dislocation density change rule of X12 alloy steel was discussed and analyzed.The cellular automaton technology combined with the curvature drive technology was used to simulate the initial grain microstructure which is consistent with physical rules.Through comparison,it was found that the shape and size of the initial microstructure under different hot deformation parameters were basically consistent with the metallographic experiments.Based on the experimental data of hot compression,and the L-J dislocation density model that can reflect the dislocation density change,X12 alloy steel grain nucleation model and growth model were established.Based on the dynamic recrystallization model of X12 alloy steel constructed above,the cellular automaton model of X12 alloy steel was constructed based on the dislocation density change combined with cellular automata technology.The established cellular automaton model was used to simulate the dynamic recrystallization microstructure evolution process of X12 alloy steel under different hot deformation conditions.The results obtained by the cellular automaton simulation were analyzed,and the effects of different hot deformation parameters on the microstructure evolution law of X12 alloy steel during hot deformation were discussed and analyzed.The simulation of different initial grain size was performed,and the effect of the initial grain size on the dynamic recrystallization microstructure evolution was analyzed.By adding topological deformation technology,the effect of topological deformation on the dynamic recrystallization microstructure evolution simulated by cellular automata was studied.And the microstructures at different positions during the hot compression process were predicted combined with the finite element simulation software Forge.The results show that the cellular automaton model of X12 alloy steel constructed in this paper can effectively reflect the microstructure of X12 alloy steel during hot deformation.It has certain guiding significance for the production and processing of X12 alloy steel for ultra-supercritical rotors.