Study of Static Recrystallization Kinetics and the Evolution of Austenite Grain Size by Dynamic Recrystallization Refinement of an Eutectoid Steel

Interrupted and continuous hot compression tests were performed for eutectoid steel over the temperature range of 850 to 1050 degrees C and while using strain rates of 0.001, 0.01, 0.1, and 1 s(-1). The interrupted tests were carried out to characterize the kinetics of static recrystallization(SRX) and determinate the interpass time conditions that are required for initiation and propagation of dynamic recrystallization (DRX), while considering that the material does not contain microalloying elements additions for the recrystallization delay. Continuous testing was used to investigate the evolution of the austenite grain size that results from DRX. The results indicate that carbon content accelerates the SRX rate. This effect was observed when the retardation of recrystallization due to a decrease in deformation temperature from 1050 to 850 degrees C was only about one order of magnitude. The expected decelerate effect on the SRX rate when the initial grain size increases from 86 to 387 mu m was not significant for this material. Although the strain parameter has a strong influence on SRX rate, in contrast to a lesser degree of strain rate, both of the effects are nearly independent of the chemical composition. The calculated maximum interpass times that are compatible with DRCR (Dynamic Recrystallization Controlled Rolling), for relatively low strain rates, suggest that the onset and maintaining of the DRX is possible. However, while using the empirical equations that were developed in the present work to estimate the maximum times for high strain rates, such as those observed in the wire and rod mills, indicate that the DRX start is feasible, but maintaining this mechanism for 5% softening in each pass after peak strain is not possible.