Study On Q235Steel Hot Rolling Simulation Intwo-phase Zone

Compared with the traditional hot rolling process in austenite zone, the rollingtechnology not only reduces the production cost in the two-phase zone of low carbonsteel, but also is expected to reduce or even replace the stage of cold rolling reductionand expand the scope of the hot rolling production. Therefore, there exists importantpractical significance to research rolling technology in the two-phase zone of lowcarbon steel. Gleeble-1500thermal simulation testing machine has been used to studythermoplastic deformation behavior of Q235steel with relatively single chemicalcomposition in (α+γ) two-phase zone in this paper. The impact of the material flowstress and microstructure in different deformation temperatures and strain rates isdiscussed in the region. The corresponding flow stress model and the DRX model areestablished, and the effect of DRX is discussed in different defomation conditionsaccording to metallographic analysis.By analyzing the true stress-true strain curves of Q235low carbon steel underdifferent deformation conditions, when deformation temperature is constant, the flowstress increases gradually as the strain rate increases; When strain rate is constant, theoverall trend of the flow stress increases as the rising of temperature in (α+γ) two-phasezone, especially at temperature from780℃to820℃, the abnormal phenomenon ismore obvious in the ferritic α austenitic γ phase zone where the phase transformationoccupy the leading role.Based on the true stress-strain curve data in different conditions and regressioncalculation, respectively, using the JC model, the Arrhenius experience model and thestress model considering the effects of phase transformation to establish the equation ofthe flow stress constitutive relation of Q235low carbon steel during thermoplasticdeformation process.The constitutive equation of JC stress model is as follows:The constitutive equation of the stress model considering the effects of phasetransformation is as follows: It is analysed that the critical strain, volume fraction and grain size of DRX ofQ235low carbon steel are received the influence of deformation temperature and strainrate. With the increase of deformation temperature, dynamic recrystallization criticalstrain showed a trend of lower, and the volume fraction of DRX increase gradually, andthe recrystallized grain size increases gradually. With the increase of strain rate,dynamic recrystallization critical strain showed a trend of increase, and the volumefraction of DRX increase gradually, and the recrystallized grain size decreases gradually.Dynamic recrystallization model of Q235low carbon steel is established under thedifferent deformation conditions.The constitutive equation of the dynamic recrystallization critical strain model is asfollows:The constitutive equation of the dynamic recrystallization volume fraction model isas follows:The constitutive equation of the dynamic recrystallization grain size model is asfollows:...