Research On Static Recrystallization Behavior And Simulation Of Microstructure Evolution For316LN

Nowadays, AP1000nuclear power technology is the safest and most advancednuclear power technology.316LN extra-low carbon austenite stainless steel is selected asmaterial of the unit main forging. The forming process of forging is complex, and producthas high grain size requirements. At the nozzle of main pipe, because amount ofdeformation is small, grain refinement is almost entirely dependent on the staticrecrystallization of hot deformation process. Studying static recrystallization of316LN inhot deformation has great significance to design forging process of main pipes and controlfinal properties of products.In this article, the static recrystallization of316LN stainless steel is studied bydouble-pass hot compression tests on Gleeble3500thermomechanical simulator. Thestress-strain curves of316LN at deformation temperatures of950~1150°C, strain rates of0.01~1s-1, and intervals of1~100s have been obtained. The2%offset method is used todetermine the volume fraction of static softening. The influence of deformation parameterson volume fraction of static softening has been analysed, and the static recrystallizationkinetics has been established.Grain structure evolution of316LN in the static recrystallization process is studied byexperimental methods in this paper. The time of completely static recrystallization hasbeen determined based on the kinetic equations of the static recrystallization. Grain sizemodel of316LN stainless steel steady state recrystallization has been establishedcombined with heat deformation experiments and metallurgical analysis techniques.The solidification process has been simulated with the cellular automata method toobtain the initial microstructure. The thermal compression process of not occuringdynamic recrystallization has been simulated to obtain deformation of the grain anddislocation density change. The316LN stainless steel static recrystallization cellularautomaton model has been established and the simulation of static recrystallizationprocess on316LN stainless steel has been achieved combined with the two-dimensionalcellular automata method of quadrilateral mesh, Von Neumann type neighbor and periodic boundary conditions based on the static recrystallization physical mechanisms. The resultsof the simulation about kinetic curve and Avrami constant are consistent with the classicaltheory of JAMK. The influence of various parameters on the static recrystallizationvolume fraction and the grain size has been analyzed by means of simulatingmicrostructure evolution under different deformation conditions. The results of simulationmatch well with the experiment.