Effect of Nb Content on the Hot Deformation Behavior of S460ML Steel

Abstract

The hot deformation behavior of S460ML steel with different Nb contents was investigated by single-pass compression experiment on the Gleeble-1500 thermo-machine simulator at deformation temperatures ranging from 900 to 1200°C and strain rates from 0.1 to 5.0 s -1 . The critical strain of dynamic recrystallization (DRC) under different conditions was determined by using working hardening rate-strain curves. The relationship between critical strain and peak strain of DRC was discussed. By means of regression analysis method, the hot deformation activation energy of steels and the mathematical model for predicting DRC critical strain were calculated and established, respectively. The results showed that DRC occurred during hot deformation. As the deformation temperature increased and strain rate decreased, the critical strain of DRC decreased. The critical strain (e c ) showed linear relationship with peak strain (e p ). As Nb content increased, the needed deformation temperature for occurring DRC increased, while the needed strain rate for it decreased. The activation energy for hot deformation of S460ML steel increased with increasing Nb content.

Hot Deformation Behavior and Processing Maps of 26CrMo7S Steel Used in Oil Exploration

“…Error analysis of the model prediction and experimental values can further describe the accuracy of the above constitutive equations. The correlation coefficient r can express the linear strength between the predicted and experimental values, and r can be computed as shown in Equation (15).…”

“…The research found that fully recrystallized structures corresponded to a high-energy dissipation zone. Zhang et al [15] studied the hot deformation behavior of S460ML steel and developed a mathematical model to predict the critical strain of dynamic recovery (DRV). This model served as a guide for actual engineering analysis.…”

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“…The critical strain can be determined by metallurgical observations; however, this requires considerable effort and time. In [32,33], it was demonstrated that when dynamic recrystallization occurs, the curves of the hardening rate θ = ∂σ ∂ε versus true stress (θ) exhibit an inflection point. The inflection point in the θ-σ curves corresponds to the maximum point of the ∂θ ∂σ −σ curves.…”