Mathematical Modeling And Simulation Of Austenite Microstructure Evolution For Low-pressure Rotor Steel

The low-pressure rotor is the key component of large-scale nuclear or thermal power generating units. During hot forging, the steel must firstly be heated to the austenitic state, and then to obtain the desired microstructure and properties under proper process conditions. As the microstructure is the main factor to determine the macroscopic mechanical properties of the low-pressure rotor, to predict the austenite microstructure evolution during hot deformation is the key to control the mechanical properties of the product. Therefore, research on mathematical modeling and simulation methods for microstructure evolution during hot deformation can provide scientific basis for the development of rational forging process.The grain growth, dynamic recrystallization(DRX), meta-dynamic recrystallization(MDRX), static recovery(SRV) and static recrystallization(SRX) occur during multi-pass hot deformation. The grain growth evolution can be modeled by physics experiments and measured results, but the other evolutions are too complex to establish microstructure evolution model. Therefore, the cellular automata(Cellular Automata, CA) simulation method is adopted to reflect the physical nature of the microstructure evolution.To predict austenite microstructure evolution during hot deformation, the austenite grain growth models during heating and pass gap, and the cellular automata models during other evolution for the rotor steel 30Cr2Ni4 Mo V were developed. The main research content is as follows:The behavior of austenite grain growth during heating was investigated and the grain growth kinetics equation was developed based on the heating-insulation experiments in the furnace. Then, the heating specification for low-pressure rotor steel 30Cr2Ni4 Mo V was studied by the finite element software Deform-2D.The recrystallized austenite grain growth law during pass gap was studied and the grain growth kinetics model was also developed based on the compression-insulation tests on the Gleeble-3500 thermal simulation machine. The model can be used to predict the recrystallization grain growth and thus to provide basis for the development of pass process.To simulate the other complex microstructure evolutions during multi-pass hot deformation, the CA models of micrstructure evolution including the formation of initial grain, DRX, MDRX, SRV, SRX were established.A simulation software to predict the microstructure evolution during multi-pass hot deformation was developed based on the mathematical models and CA models using the Visual C ++ programming tool.