Abstract
Strengthening by micro-alloying permits a remarkable reduction in carbon content which greatly improves weldability and notch toughness. As the strength requirement has increased, a shift from traditional ferrite/pearlite (FP) microstructure produced by a conventional alloy design to a ferrite/acicular ferrite (F/AF) microstructure has been necessary. The ultimate steel microstructures and final properties of steel are shown to be highly dependent on both controlled rolling and accelerated cooling conditions. Two steel grades one having richer chemistry alloyed with Nb–V–Mo–Ti and other lean chemistry with Nb–Ti addition thermo-mechanically processed in such a way that Mo containing steel yielded polygonal ferrite–bainite structure. Whereas, high reduction per pass and high cooling rate in Nb–Ti steel resulted into fine acicular ferrite and bainite microstructure. This steel possessed attractive properties in terms of YS: 584–592 MPa, UTS: 763–803 MPa, %EL: 29–31, YS/UTS: 0.72–0.77 and Charpy impact energy of 210–222 J compared to that of Nb–V–Mo–Ti bearing steel with polygonal ferrite and bainite structure with YS: 487–490 MPa, UTS: 566–576 MPa, %EL: 32–34, YS/UTS: 0.84–0.86 and Charpy impact energy of 328–344 J. The properties so achieved have been related to microstructural variations from polygonal ferrite and bainite to acicular ferrite and bainite.
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The authors are grateful to the management of RDCIS, SAIL, for extending kind permission and support to carry out the work and also for giving permission to publish this work.
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Serfraj Alam, M., Gupta, R., Das, G., Kumar, V., Jha, B.K. (2021). Development of High Strength Low Carbon Lean Micro-alloyed Steel with Optimized Toughness. In: Bag, S., Paul, C.P., Baruah, M. (eds) Next Generation Materials and Processing Technologies. Springer Proceedings in Materials, vol 9. Springer, Singapore. https://doi.org/10.1007/978-981-16-0182-8_1
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