.12% Cr Ultra-supercritical Rotor Steel Forging Process Of Microstructure Evolution Of Experimental And Simulation Studies

Due to excellent plasticity, hardenability, oxidation resistance, weldability and so on,12% Cr ultra-supercritical rotor steel becomes the material of high pressure rotor in the 1000MW ultra-supercritical nuclear set. But the microstructural evolution of the very large volume of the rotor is difficult to control during the forging and heat treatment process,which leads to the significantly decrease of yield strength and impact ductility and is bad to improve of mechanical property because of mixed crystal and coarse grain. Therefore, microstructure evolution rule during the hot deformation process of 12% Cr ultra-supercritical rotor steel has been thoroughly studied. These results could provide the significant theoretical basis during the practical forging technology of ultra-supercritical rotor for the heavy forging.Based on the numerical simulation and physical simulation technique, the microstructure evolution rule of 12% Cr rotor steel during the forging process has been systematically studied and then the microstructure evolution models have been constructed. And then these models have been input the finite element software and simulate the practical forging test process. The main results are as follows:(1) Through the research on the austenite grain growth of various process parameters, grain growth rule of 12% Cr ultra-supercritical rotor steel has been acquired and grain growth model has been established by the regression method. And then comparing the experimental values and the fitting value of the model to verify the reliability of the model.(2) By the hot compression simulation test,the high temperature plasticity behavior of 12% Cr rotor steel has been investigated in the different conditions. The relationship among flow stress, strain rate and deformation temperature under high temperature deformation has been described by hyperbolic sine function via the analysis. According to the strain hardening rate, the critical strain value of dynamic recrystallization, dynamic recrystallization model and grain size model of 12% Cr rotor steel have been established. (3) Using double pass hot compression test, the static softening behavior of 12% Cr rotor steel has been studied. The softening curves of static recrystallization and meta-dynamic recrystallization are in accord with the Avrami equation. And the corresponding recrystallization kinetics model and grain size model have been obtained by analysis the effect of different deformation parameters.(4) Combining with the coupling technology of macroscopic thermodynamic behavior and microstructure evolution, the practical forging process of different softening behavior have been simulated using DEFORM-3D. The error of grain size between simulation and forging test was small which validated the reliability of microstructure models.