Flow stress, dynamic restoration, strain hardening and ductility in hot working of 316 steel

Abstract

From the determination of flow stress σ in torsion tests over the range 900–1200°C, 0.1–5.0 s −1, in both as-cast and worked 316 stainless steel, the dependence on temperature and strain rate is shown to fit the sinh and Arrhenius functions. Through evolution of the strain-hardening rate θ, changes in slope of the θ-σ curves and extrapolation to the θ=0 axis permits determination of the saturation stress σ s ∗, the constants for the Kocks-Mecking equations and the critical strain for dynamic recrystallization, which could be compared with σ p and ϵ p at the peak in the flow curve. The ductility mounts as temperature rises, the strain-rate falls and the cast structure becomes homogenized. The relationships between grain size, substructure, hot ductility, and stress are discussed. The above hot properties are compared with those of 304 and 317 which have less and more molybdenum respectively.