Study On Recrystallization Behavior And Thermaldeformation Simulation Of Special Forgings

Special forgings have an important impact on the national economy,and34CrNi3MoV steel has excellent comprehensive mechanical properties and can be used to manufacture tank guns,artillery barrels and autoclave components.In actual production,numerical simulation techniques are often used to evaluate and optimize the thermal deformation process of large forgings before formal production due to the large size of the components and the extreme difficulty of forging.However,the reliability of the simulation results depends heavily on the accuracy of the model predictions.In this thesis,the rheological characteristics and grain morphology evolution of34CrNi3MoV steel were systematically investigated for the thermal processing process,isothermal deformation tests were conducted using a thermo-mechanical simulator,relevant mathematical models were established,and the accuracy of the model prediction was analyzed using finite element software.The main work of this thesis is as follows:Firstly,the stress-strain curves of 34CrNi3MoV steel under different deformation parameters were obtained using single-pass isothermal deformation tests,and the constitutive equations were constructed using two different phenomenological model,and the comparison results showed that the Arrhenius model has higher prediction accuracy.Based on the metallographic test results and datas,a model of the relationship between the critical eigenvalue and the Z parameter was established using the work-hardening rate,on which a kinetic model to predict the dynamic recrystallization volume fraction and a model to describe the grain size evolution were established.Secondly,according to the critical strain characteristic value of dynamic recrystallization,compression interval tests were designed and conducted to analyze the recrystallization behavior during the interval time,and a mathematical model related to sub-dynamic recrystallization of 34CrNi3MoV steel was established based on the test results.The analysis results show that increasing the deformation temperature,extending the interval time and accelerating the strain rate are all beneficial to the improvement of the sub-dynamic recrystallization softening rate,and that finer new grains can be obtained when compressing at high strain rate,but the high temperature environment is not conducive to the grain refinement.Finally,the simulation software was used to simulate the hot compression test process,and the dynamic recrystallization simulation results showed that the dynamic recrystallization in the hot compression process has extremely high regional selectivity,and complete dynamic recrystallization occurred in the central part of the specimen at the strain rate of 0.1 and 0.01 s^-1and the deformation temperature of 1100 and 1200℃,but the grain size in the central part is larger under this condition,which is not conducive to actual production.Meanwhile,the comparison of the simulation prediction results with the test results shows that the accuracy of the model prediction is reliable.