Processing Low and Ultra-Low Carbon Bainitic Steels with Excellent Property Combinations

Abstract:

Six experimental low and ultra-low carbon C-Mn-Mo-Nb-B and one conventional TMCP steel heats have been prepared to study the effects of chemical composition and hot deformation on the microstructure and the strength-toughness properties. In physical simulation tests, it was found that the deformation of austenite below the non-recrystallization temperature enhances the formation of higher-temperature bainitic morphologies and polygonal ferrite. On the other hand, hardness exhibits relatively low sensitivity to the degree of deformation below Tnr, whereas the deformation results in a distinct refinement in the microstructures, as determined by SEM-EBSD measurements, suggesting an improvement in the impact toughness. Simultaneous alloying with Mo-Nb-B seemed to be most efficient to provide high hardness and strength. Hot rolling trials indicated that the yield strength in the range 500-700 MPa with the excellent toughness down to –80 °C can be achieved in low carbon (≈ 0.03%) bainitic grades.

• Periodical: Materials Science Forum (Volumes 500-501)
• Pages: 535-542
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.500-501.535
• Online since: November 2005
• Authors: P.P. Suikkanen, Jukka Kömi, L. Pentti Karjalainen
• Keywords: Austenite Decomposition, Grain Size, Low Carbon Bainitic Steel, Microstructure, Strength, Toughness, Ultra Low Carbon Bainitic Steel

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