A Flow Stress Model for High Strength Steels with Low Carbon Bainite Structure

Two kinds of steels (YP960 and YP690) with low carbon bainite structure were designed, and their flow stress and strain hardening exponents were studied. The results showed that, when Hollomon relation was applied to describe the flow stress, there were significant errors between the experimental and calculated points in specimens tempered below 400 °C, while a high precision was observed in samples tempered above 400 °C. Whereas, the modified Voce relation could effectively predict the flow stress as well as the strain hardening exponent at different tempering temperatures, which was verified by unbiased estimators such as maximum relative error (MRXE) and average absolute relative error (AARE). Besides, the modified Voce relation was also applied to estimate the maximum uniform strain, and the correlation coefficients (R) between the experimental data and calculated maximum uniform strain were more than 0. 91. The high correlation coefficients indicated that the modified Voce relation could effectively predict the uniform deformation ability of high strength steels with low carbon bainite structure at different tempering temperatures.