Constitutive analysis of hot forming process of P91 steel: finite element method approach

This study reports on the forging simulation of P91 steel at a temperature range of 900–1200°C and a strain rate range of 1–15 s⁻¹ using Deform 3D finite element software. The study investigated the effect of forging parameters on metal flow behaviour. The flow stress increased with increasing strain rate at a given temperature, whereas at a constant strain rate, the flow stress decreased with increasing temperature. The results established that metal flow behaviour depends on the process parameters. By substituting flow stress values in the Arrhenius equations, stress exponents “n”and activation energy “Q” were derivedas 5.38 and of 572.89 kJmol⁻¹respectively. A constitutive model for predicting flow stress over a wide range of forging conditions tested was developed. The model was verified by using statistical parameters: correlation coefficient R and average absolute relative error AARE. From the statistical analysis, the values were: R = 0.994 and AARE = 2.988%. The study demonstrates that the FEM simulation model can be applicable in performing, analysing and evaluating industrial metal forming processes.