Effect of Number of Roughing Passes on the Dynamic Transformation of Austenite during Simulated Plate Rolling

Abstract:

When austenite is deformed within the austenite phase field, it partially transforms dynamically into ferrite. Here, plate rolling simulations were carried out on an X70 steel using rough rolling passes of 0.4 strain each. The influence of the number of roughing passes on the grain size and volume fraction of induced ferrite was determined. Up to three roughing passes applied at 1100 °C followed by 5 finishing passes at 900 °C were employed. The sample microstructures were analysed by means of metallographic techniques. Both the critical strain to the onset of dynamic transformation as well as the grain size decreased with pass number during the roughing simulations. For the finishing passes, the mean flow stresses (MFS`s) applicable to each schedule decreased when a higher number of roughing passes was applied. The volume fraction of dynamically formed ferrite retained after simulated rolling increased with the roughing pass number. This is ascribed to the increased amount of ferrite retransformed into austenite and the finer grain sizes produced during roughing. The forward transformation is considered to occur displacively while the retransformation into austenite during holding takes place by a diffusional mechanism. This indicates that both dynamic transformation (DT) and dynamic recrystallization were taking place during straining.

• Periodical: Materials Science Forum (Volume 941)
• Pages: 717-722
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.941.717
• Online since: December 2018
• Authors: Samuel F. Rodrigues*, Fulvio Siciliano, Clodualdo Aranas Jr., Gedeon S. Reis, Brian J. Allen, John Joseph Jonas
• Keywords: Dynamic Transformation, Mean Flow Stress, Roughing Passes, X70 Steel

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