Determination of recrystallization stop temperature (TR) of an HSLA steel

Abstract

The alloy chemistry of HSLA steels makes them suitable for thermomechanical processing. However to design thermomechanical processing of HSLA steels, a prior knowledge of recrystallization stop temperature (TR) of the steel is essential. In the present work, an attempt has been made to estimate the TR temperature of a Nb-containing HSLA-100 steel. By analyzing experimental data from published work, regression equations for flow stresses are developed, connecting flow stress with deformation temperature and Nb content of the steel in the region of recrystallization and non-recrystallization zone. These equations are valid for steels with wide range of variation of Nb content (0-0.098%) with a deformation temperature ranging between 850 °C to 1130 °C and an average strain rate in the neighborhood of 3-4/sec. The recrystallization stop temperature (TR) is obtained by solving the above two equations of flow stress for the present steel having 0.03% Nb. The TR temperature thus computed, for a steel used by other researchers, is compared with the TR temperature obtained by them using different experimental techniques. The validity of the equations is further checked by computing flow stresses from the equations for the steel used in the present investigation at various rolling temperatures and comparing with the flow stresses obtained experimentally (i.e. by roll force measurement and using Sim's equation).