Effect of Composition on the Recrystallization Behavior of if Steels During Simulated Hot Strip Rolling

Flow curves are generated in muti-pass torsion tests for a titanium stabilized and a niobium stabilized IF steel. Two types of test schedule are used, one based on plate rolling and the other approximating strip rolling. The purpose of the former is to define the three critical temperatures of steel rolling. The strip schedules are varied in order to investigate the influence of increasing the total finishing strain (from 2.1 to 3.2) and lowering the first finishing pass temperature (from 990 to 930°C) on microstructural evolution in these steels. All the tests are carried out at a strain rate of 2s-1. Under hot strip rolling conditions, static recrystallization is responsible for the high degree of interpass softening. During the final passes, dynamic recrystallization occurs to a degree that depends on the composition of the steel, the total finishing strain and the temperature. Subjected to the same strip rolling schedule, the niobium stabilized steel has a finer ferrite grain size than the IF steel stabilized with titanium.