Two constitutive descriptions of boron steel 22MnB5 at high temperature

• Two high-temperature constitutive descriptions of boron steel 22MnB5 are derived.
• The first is a strain-compensated Arrhenius-type constitutive equation.
• The second is a set of unified mechanism-based viscoplastic equations.
• Both descriptions are effective in describing the hot tensile behavior of 22MnB5.
• However, the prediction accuracy of the first description is a little higher.

The hot deformation behavior and constitutive description of the boron steel 22MnB5 are of vital importance to the process design and numerical simulation of the steel during hot stamping. In order to establish two constitutive descriptions for 22MnB5, it was subjected to isothermal uniaxial tensile testing on a Gleeble 3500 thermomechanical simulator at temperatures ranging from 700 °C to 900 °C and strain rates ranging from 0.01 s−1 to 10 s−1. On the basis of the testing results, a strain-compensated Arrhenius-type constitutive equation and a set of unified viscoplastic equations that take into account the dislocation density were derived for describing the flow behavior of 22MnB5 during hot stamping. The material constants for the two constitutive descriptions were obtained by linear regression and genetic algorithm-based optimization, respectively. Further, the predictability of both the constitutive descriptions was assessed in terms of the correlation coefficient, the average absolute relative error, the root mean square error, and the distribution of the relative error. The results indicated that both constitutive descriptions are effective for describing the hot tensile behavior of 22MnB5, however, the prediction accuracy of the strain-compensated Arrhenius-type constitutive equation is a little higher than that of the unified viscoplastic constitutive equations.