Hot Deformation Behavior of a Marine Engineering Steel for Novel 980 MPa Grade Extra‐Thick Plate

Abstract

The hot deformation behavior of a marine engineering steel for a novel 980 MPa grade extra‐thick plate is investigated through hot compression tests at temperatures of 850–1200 °C and strain rates of 0.01–10 s−1. The flow stress curves are corrected to eliminate the effects of friction on the flow stress, and a modified constitutive model is established to accurately quantify the flow behaviors of the steel. Hot working maps of the steel are derived by using a dynamic materials model and the Prasad instability criterion. The effects of the deformation parameters on the dynamic recrystallization (DRX) nucleation mechanisms are evaluated using scanning electron microscopy and electron backscatter diffraction. The flow stress and peak strain increased with decreasing deformation temperature and increasing strain rate, respectively. The activation energy for hot deformation after friction correction is 380.49 kJ mol−1. The DRX mechanism involves the migration of subgrains. The deformation parameters are optimized by combining the degree of DRX and the size of recrystallized grain. The optimum hot working window is determined as 1100–1200 °C and 0.1–10 s−1.