Grain size model of high-strength steel in multi-pass hot compression
To accurately describe the grain size evolution behavior of 300M high-strength steel during multi-pass hot compression process and solve the problem of discontinuous grain size between different recrystallization processes,a grain size evolution model containing fif-teen parameters was proposed.Double-pass hot compression experiments were carried out in the temperature range of 950-1150 ℃,strain rate range of 0.01-10 s-1,strain range of 0-0.9 and inter-pass holding time range of 0-600 s.The results show that the average grain size increases with increasing of temperature and decreasing of strain rate.Meta-dynamical recrystallization and static recrystalliza-tion occurred completely holding about 3 min after deformation,and grain growth was very slow during subsequent holding time.With the increase of strain,the recrystallization volume fraction increases.Based on the experimental results,the model parameters were obtained by parameter identification with average relative error of 6.9％and average relative deviation of 3.3 μm.The model was integrated into DEFORM to simulate the variation of average grain size of cylindrical specimen of Φ90 mm x 200 mm.Validation experiments were carried out on a die forging press.The results show that the developed double-pass compression grain size evolution model can predict well the e-volution of the average grain size of 300M high-strength steel.
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