Modeling of Flow Stress and Rolling Load of a Hot Strip Mill by Torsion Testing

Abstract

In order to characterize the Lake Erie Workshot strip mill, Stelco Steei, two grades of steel (C-Mnand Nb) were subjected to torsional simulation. The flow stresses and rolling loads are considered in this report. The microstructural behaviours of the two grades are comparedin a separate publication As anticipated, for long interpass times, the Tnr temperature (temperature of no-recrystallization) can be clearly established only for the Nbsteel, the other grade undergoing nearly full softening, i.e recrystallization, at all temperatures By contrast, for short interpass times of the order of 2s, typical of the strip mill, there is little pass-to-pass strain accumulation in either steel. In the temperature range 1 020 to 920°C, static recrystallization is largely responsible for the high degree of interpass softening in the C-Mn steel. In the case of the Nb steel, because of solute effects, the short interpass times do not permit much conventional recrystallization. Instead, softening is brought about mostly by dynamic and post-dynamic recrystallization. This is possible because there is considerably less Nb(CN) precipitation during the short interpass times than under reversing (plate) mill conditions. The decreased level of precipitation in the Nb steel, followed by the initiation of dynamic recrystallization, leads to lower rolling loads in the strip mill for this grade than in the plate mill at the same rolling temperatures. © 1989, The Iron and Steel Institute of Japan. All rights reserved.