STUDY ON THE DYNAMIC RECRYSTALLIZATION MODEL OF 20CrMnTi STEEL
Gear is an important part of mechanical transmission system.As a widely used gear steel,20CrMnTi has higher and higher requirements for the uniformity of bar structure.Nevertheless,as the bar size increases,the challenge of maintaining microstructure uniformity becomes more difficult.The austenitic deformation behavior of gear steel 20CrMnTi at high temperature was studied by Gleeble thermal simulation experiment in order to improve the microstructure uniformity of bar.True stress-strain curves were obtained for deformation temperatures ranging from 950 ℃ to 1 150 ℃,strain rates ranging from 0.01 s-1 to 10 s-1,and a compression strain of 0.7.A dynamic recrystallization model for this steel was established,which includes the critical strain model for dynamic recrystallization,the volume fraction model for dynamic recrystallization,and the grain size model for dynamic recrystallization.In order to further verify the accuracy of the model,the stepped sample was used for hot rolling experiment and the grain size of the rolled austenite was obtained.The austenite grain size obtained by rolling experiment is compared with that obtained by recrystallization model in thermal-mechanical coupling finite element model of 20CrMnTi steel,and the calculated grain size is in good agreement with the experimental value.It is proved that the prediction accuracy of this model is high,and it can provide a theoretical basis for the optimization of 20CrMnTi bar rolling process.
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