Optimisation of hot rolling schedule for direct charging of thin slabs of Nb–V microalloyed steel

Abstract

AbstractA recently developed continuous casting simulator and the ‘Wumsi’ hot deformation simulator have been used to carry out laboratory simulation tests to determine the as cast microstructure and the recrystallisation behaviour of a Nb–V microalloyed steel during the process of direct charging. By variation of the initial specimen thickness (between 25 and 60 mm) different values of total strain ΦΣ could be imposed to improve the coarse as cast microstructure. For a series of deformation schedules the total strain was divided systematically into two components: an austenite grain refining strain ΦγGF (above the recrystallisation stop temperature TRS) and an austenite strengthening strain ΦγS (below TRS). After hot deformation slow and accelerated cooling with simulated coiling were employed. It was found that a total strain ΦΣ>1·4 is required to ensure mechanical properties that were comparable or even superior to those found using the conventional cold charging process. The coarse as cast austenite m...