Dynamic Transformation during Simulated Hot Rolling

Abstract:

High temperature flow curves were evaluated on two Nb steels in both compression and torsion and at a series of temperatures and strain rates. The critical strains for the initiation of dynamic transformation (DT) were determined by the double differentiation method. These are shown to be distinctly lower than those associated with dynamic recrystallization (DRX). It is also evident that the compression critical strains for both DT and DRX are lower than the equivalent torsion critical strains. Mean flow stresses (MFSs) were calculated by integration from the flow curves. When plotted against inverse temperature, stress drops were observed about 30 degrees above the Ae₃. These drops are shown to be caused by the dynamic transformation of austenite to ferrite, a softer phase. The characteristics of the ferrite produced dynamically are described and the transformation is shown to be displacive in nature, leading to the appearance fine Widmanstatten plates.

• Periodical: Materials Science Forum (Volume 762)
• Pages: 1-8
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.762.1
• Online since: July 2013
• Authors: John J. Jonas, Chiradeep Ghosh, Vladimir V. Basabe
• Keywords: Austenite, Cooling Rates, Critical Strain, Critical Temperatures, Dynamic Transformation, Ferrite, Interpass Times, Plate Rolling, Strip Rolling, Transformation

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