Study On Hot Deformation And Dynamic Recrystallization Behavior Of 60Si2CrVAT Spring Steel

The hot compressive experiment of 60Si2CrVAT spring steel was carried out on Gleeble-3800 thermo-simulation machine. The influence of deformation temperature and strain rate on the hot deformation behavior was investigated at 900～1150℃ and strain rate of 0.1～10s-1.The results show that the flow stress of the spring steel was decreased with increase of temperature but raising with increase of strain rate. The stress-strain curves of deformation rate of 0.1s-1 at different deformation temperature and deformation rate of ls-1 and deformation temperature of 950℃,1050℃ and 1150℃ have the characteristics of dynamic recrystallization.On the basis of the experimental data, the constitutive equation of 60Si2CrVAT spring steel was established according to the Arrhenius hyperbolic sine equation. According to the peak stress value, the thermal deformation activation energy of the material is 338KJ/mol. Methods which find regression under the peak stress was used to calculate the relationship between various constant Q, a, N, a and true strain, and a constitutive equation including deformation temperature, strain rate, the hyperbolic sine equation form of 60Si2CrVAT spring steel was established.Based on the dynamic recrystallization theory, the dynamic recrystallization critical strain model, the dynamic recrystallization volume fraction model and the dynamic recrystallization grain size model are established on the base of the experimental data and the analysis of microstructure of 60Si2CrVAT spring steel. The study found that dynamic recrystallization volume fraction increases with the increase of deformation, recrystallization volume fraction raise with the raise of the deformation temperature and the dynamic recrystallization grain size raise with the increase of the deformation temperature.The constitutive equation, the material parameters and the establishment of the dynamic recrystallization model are embedded into the DEFORM-3D and n μ-merical simulation was conducted on 60Si2CrVAT spring steel. In the hot compression process, stress and strain in the specimen unevenly distribute and change with the amount of deformation, strain rate and deformation temperature. Dynamic recrystallization happens in the center of the specimen first. With increase of deformation, dynamic recrystallization volume fraction also increases and completely dynamic recrystallization region appears. When the strain and strain rate are under certain conditions, the dynamic recrystallization can be promoted with the increase of the deformation temperature. The grain size decreases with the increase of deformation and strain rate and the decrease of the deformation temperature, but the uniformity in the specimen is poor. The dynamic recrystallization volume fraction and grain size were similar to the experimental results which showed that the model was accurate.