Effect of the Time between Last Deformation Pass and Accelerated Cooling on the Mechanical Properties in Nb and Nb-Mo Microalloyed Steels

Abstract:

The microstructural refinement induced when the holding time between last deformation pass and accelerated cooling is reduced, affects the mechanical properties in low carbon Nb and Nb-Mo microalloyed steels. Plane strain compression tests were performed and mechanical property samples machined in order to quantify this effect using tensile and Charpy impact tests. A complete microstructural characterization was carried out using electron backscattered diffraction (EBSD) measuring unit size distributions and homogeneity of complex microstructures. The synergetic combination of Nb and Mo elements modifies the final microstructures and, therefore, affects the contribution of different strengthening mechanisms, such as substructure, precipitation hardening and dislocation density. Even though strength is not clearly affected by the reduction of the holding time after the last deformation pass, Charpy properties are considerably improved in the case of the Nb steel. The presence of MA islands in the Nb-Mo steel limits the beneficial effect of the microstructural refinement and toughness remains unmodified.

• Periodical: Key Engineering Materials (Volume 716)
• Pages: 281-290
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.716.281
• Online since: October 2016
• Authors: Gorka Larzabal, Nerea Isasti, J.M. Rodriguez-Ibabe, Isabel Gutiérrez, Pello Uranga*
• Keywords: Ferrite Grain Refinement , Molybdenum, Niobium, Strength, Toughness

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