Modeling the hot deformation flow curves of API X65 pipeline steel

In this paper, a new simple model was developed based on a power function of Zener-Hollomon parameter and a third-order polynomial function of strain(m) (m is a constant) to model the hot flow stress of API X65 pipeline steel. The results of the developed equation for modeling the hot flow stress of API X65 pipeline steel was compared with two other constitutive equations, including the Arrhenius equation with strain-dependent constants and an equation with the peak stress, peak strain, and four constants. The performance of all three equations was compared with each other using a root-mean-square error (RMSE) criterion. According to the results obtained, the developed model showed better performance than that of the Arrhenius equation, but worse performance than that of the equation with the peak stress and peak strain. The simplicity of the proposed model is its advantage over the other considered constitutive equations. However, its performance is in an acceptable range.