Formulation of Flow Stress of Nb Added Steels by Considering Work-hardening and Dynamic Recovery.

Abstract

Flow stress of Si-Mn steel and Nb added steels measured under the usual hot deformation conditions for the rolling of steel plates was formulated by taking strain hardening and dynamic recovery into consideration. The functions derived include variables of deformation conditions such as deformation temperature, strain and strain rate and metallurgical factors such as austenite grain size and Nb concentration. The calculated stress-strain relations and the stress-dislocation density relations show close correlation with experimental data. The increase in flow stress by Nb addition is due to the additional effects of the increase in strain hardening rate and the decrease in dynamic recovery rate leading to a high level of dislocation density just after deformation.