High temperature deformation behavior and constitutive modeling for 20CrMnTiH steel

• The hot deformation behavior of 20CrMnTiH steel was investigated.
• The optical micrograph of 20CrMnTiH steel after hot compression was observed.
• The sine-hyperbolic constitutive equation of 20CrMnTiH steel was formulated.
• The developed constitutive model has a good prediction of peak flow stress by comparing with experimental data.

The hot compressive deformation behavior of 20CrMnTiH steel, which is one of the most widely used gear steels in China, was investigated at the temperatures from 950 °C to 1150 °C and strain rates from 0.01 to 5 s−1 on Gleeble-3500 thermo-simulation machine. Stress–strain data collected from the tests were employed to establish the constitutive equation. The results show that the flow stress decreases with increasing deformation temperature and decreasing strain rate and the stress–strain curves exhibit single-peak dynamic recrystallization (DRX). The average grain sizes decreased with the increasing strain rate and the decreasing deformation temperature and the higher the deformation temperature, the larger the dynamic recrystallization degree. The exponential law and the hyperbolic sine-type function constitutive equation were established to describe the relationship among σ, T   and ε̇ for 20CrMnTiH steel at the strain rate range of 0.01–0.1 s−1 and 1–5 s−1, respectively. The peak stress values predicted by the proposed constitutive model agree well with the corresponding experimental results, which confirmed the accuracy and reliability of the developed constitutive equation of 20CrMnTiH steel.