Study On The Microstruture Evolution Model And Numerical Simulation During F35MnVN Steel Hot Forging Process

Non-quenched and tempered steel in china has a very broad application prospects,especially in the automotive industry. The reason is mainly because of economic andtechnical characteristics of the non-quenched and tempered steel, for example it hasreduced the heat treatment of high energy consumption, saved energy and so on. However,during the actual production process, high strength and hardness are prone to lead to poorperformance of plasticity and toughness. Therefore, in order to get better mechanicalproperties of non-quenched and tempered steel, It is necessary to study the thermal processparameters and the microstructure evolution process.Select the more usage hot forging materials F35MnVN in china as study object.Through hot compression test on the gleeble-3800thermal simulation machine, the truestress-strain curve was obtained, flow stress curve of F35MnVN steel at high temperaturehave typical dynamic recrystallization feature. For the two stages of flow stress with thedeformation changes, the material flow curve is divided into hardening-dynamic recoverystage and dynamic recrystallization stage. Modeling with the Zener-Hollomon parameter，the mathematical expression of the characteristic variables was established. So thematerial’s high temperature flow stress model was established too.Through single-channel compression test and analysis on the stress-strain curve, thedynamic recrystallization fraction model was established. Through quantitativemetallography experiments and analysis on the sample， the dynamic recrystallizationgrain size of F35MnVN steel under different conditions was gotten, so, modeling with theZener-Hollomon parameter， the dynamically recrystallized grain size model wasestablished. By dual-channel compression test and analysis on the stress-strain curve andwith the Avrami equation， the static recrystallization fraction model was established. Byquantitative metallogrphy experiments and analysis on the sample， the staticrecrystallization grain size under different conditions was gotten, so the staticrecrystallization grain size model was received. By austenite grain growth experiments andmetallograhpic experiments， the grain size was obtained, so, the grain growth model was received.Through secondary development of finite element software MSC.Marc， theestablished flow stress model and microstrucure evolution model were written into thesubroutine of MSC.Marc. The strain, dynamic recrystallization fraction and dynamicallyrecrystallized grain size were simulated during the F35MnVN hot deformation process.Through simulation and experimental data， the correctness of model was verified, metalmicrostructure evolution during hot deformation process was predicted, and the theoreticalbasis to control the mechanical properties of the products effectively had been provided.