260

280A

280A

P.153-163

Flow curves were generated in multi- pass torsion tests for a titanium stabilized and a niobium stabilized IF steel. Two types of test schedule were used, one based on plate rolling and the other approximating strip rolling. The purpose of the former was to define the three critical temperatures of steel rolling. The strip schedules were 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 were carried out at a strain rate of 2s .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.

77/11

Shahsavary

GN132422