Rapid Spheroidization and Grain Refinement Caused by Thermomechanical Treatment for Plain Structural Steel

Abstract:

The cold formability of ferritic-pearlitic steels is one of the base parameters for material choice for different forming parts. One of the key factors is the pearlite morphology, which is strongly dependent on chemical composition and previous treatment history. The carbides in pearlite occur mainly in the lamellar form. One of the ways of improving the ductility along with formability is the change of lamellar carbides to globular carbides. This can be conventionally done by soft annealing, which is characterised by long processing times and high energy costs. This paper presents a new processing modification which can lead on the one hand to significant shortening of carbide spheroidization times and on the other hand to intensive refinement of grain size even for low-carbon steels. Low temperature thermomechanical treatment with variation of the heating temperature around A_c1 and incremental deformation was examined on low carbon plain RSt-32 steel. After the thermomechanical treatment conditions were optimized, the refinement of the ferritic grains from an initial 30 μm to circa 5 μm took place, and the time necessary for carbide spheroidization was shortened from several hours to several seconds.

• Periodical: Materials Science Forum (Volumes 706-709)
• Pages: 2770-2775
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.706-709.2770
• Online since: January 2012
• Authors: Bohuslav Mašek, Hana Jirková, Ludmila Kučerová
• Keywords: Carbide Morphology, Rapid Spheroidization, Thermomechanical Treatment (TMT)

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