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Modeling of Precipitation Hardening during Coiling of Nb–Mo Steels Maetz, Jean-Yves; Militzer, Matthias; Chen, Yu Wen; Yang, Jer-Ren; Goo, Nam Hoon; Kim, Soo Jin; Jian, Bian; Mohrbacher, Hardy

Abstract

Nb–Mo low-alloyed steels are promising advanced high strength steels (AHSS) because of the highly dislocated bainitic ferrite microstructure conferring an excellent combination of strength and toughness. In this study, the potential of precipitation strengthening during coiling for hot-strip Nb–Mo-bearing low-carbon steels has been investigated using hot-torsion and aging tests to simulate the hot-rolling process including coiling. The obtained microstructures were characterized using electron backscatter diffraction (EBSD), highlighting the effects of Nb and Mo additions on formation and tempering of the bainitic ferrite microstructures. Further, the evolution of nanometer-sized precipitates was quantified with high-resolution transmission electron microscopy (HR-TEM). The resulting age hardening kinetics have been modelled by combining a phenomenological precipitation strengthening model with a tempering model. Analysis of the model suggests a narrower coiling temperature window to maximize the precipitation strengthening potential in bainite/ferrite high strength low-alloyed (HSLA) steels than that for conventional HSLA steels with polygonal ferrite/pearlite microstructures.

Item Metadata

Title
Modeling of Precipitation Hardening during Coiling of Nb–Mo Steels
Creator
Maetz, Jean-Yves; Militzer, Matthias; Chen, Yu Wen; Yang, Jer-Ren; Goo, Nam Hoon; Kim, Soo Jin; Jian, Bian; Mohrbacher, Hardy
Contributor
University of British Columbia. Centre for Metallurgical Process Engineering
Publisher
Multidisciplinary Digital Publishing Institute
Date Issued
2018-09-25
Description
Nb–Mo low-alloyed steels are promising advanced high strength steels (AHSS) because of the highly dislocated bainitic ferrite microstructure conferring an excellent combination of strength and toughness. In this study, the potential of precipitation strengthening during coiling for hot-strip Nb–Mo-bearing low-carbon steels has been investigated using hot-torsion and aging tests to simulate the hot-rolling process including coiling. The obtained microstructures were characterized using electron backscatter diffraction (EBSD), highlighting the effects of Nb and Mo additions on formation and tempering of the bainitic ferrite microstructures. Further, the evolution of nanometer-sized precipitates was quantified with high-resolution transmission electron microscopy (HR-TEM). The resulting age hardening kinetics have been modelled by combining a phenomenological precipitation strengthening model with a tempering model. Analysis of the model suggests a narrower coiling temperature window to maximize the precipitation strengthening potential in bainite/ferrite high strength low-alloyed (HSLA) steels than that for conventional HSLA steels with polygonal ferrite/pearlite microstructures.
Subject
Advanced high strength steels; HSLA steels; Precipitation strengthening; Tempering; Bainitic ferrite; EBSD; Austenite-to-ferrite transformation; Hot-torsion test; Coiling simulation
Genre
Article
Type
Text
Language
eng
Date Available
2019-06-18
Provider
Vancouver : University of British Columbia Library
Rights
CC BY 4.0
DOI
10.14288/1.0379490
URI
http://hdl.handle.net/2429/70695
Affiliation
Other UBC; Non UBC
Citation
Metals 8 (10): 758 (2018)
Publisher DOI
10.3390/met8100758
Peer Review Status
Reviewed
Scholarly Level
Faculty
Rights URI
https://creativecommons.org/licenses/by/4.0/
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DSpace

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CC BY 4.0