THE INFLUENCE OF STATIC AND DYNAMIC RECRYSTALLIZATION ON MEAN FLOW-STRESS AND GRAIN-SIZE IN STEEL

Whether or not static or dynamic recrystallization takes place in stee l under industrial hot forming conditions depends on the schedule vari ables of strain, strain rate, temperature and interpass time. It is im portant to identify which of the two mechanisms is operative, because the microstructural evolution and rolling load differ strongly. The de termination, by physical simulation, of the three critical temperature s of hot rolling (the temperatures of no-recrystallization, and of the start and finish of the austenite-to-ferrite transformation) is outli ned. This is followed by a consideration of the effects of changes in the test schedule on the critical temperatures, in particular that of the interpass time on the no-recrystallization temperature, which are interpreted in terms of the changeover from static to dynamic recrysta llization. The possibilities of ultra grain refinement based on an exp loitation of the characteristics of dynamic recrystallization are also described. Finally, strategies are suggested for the design and optim ization of dynamic recrystallization rolling schedules.