University of Oulu

Ma, B., Wu, Y., Hua, M., Uusitalo, J., & DeArdo, A. J. (2020). The development and characterization of ultra high GIGA-strength ferritic hot band steels. Materials Science and Engineering: A, 796, 140048.

The development and characterization of ultra high GIGA-strength ferritic hot band steels

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Author: Ma, Bing1,2; Wu, Yingjie1; Hua, Mingjian1,3;
Organizations: 1Basic Metals Processing Research Institute, Department of Mechanical Engineering and Materials Science, Swanson School of Engineering, University of Pittsburgh, 636 Benedum Hall, 3700 O'Hara Street, Pittsburgh, PA, 15261, USA
2Global Solar Energy, Inc., 8500 S. Rita Rd, Tucson, AZ, 85747, USA
3Sichuan University – Pittsburgh Institute (SCUPI), Sichuan University, Zone 4, Liberal Arts Building, Jiang'an Campus, Chengdu, Sichuan Province, 610207, China
4Centre for Advanced Steels Research, Materials Engineering Laboratory, Department of Mechanical Engineering, University of Oulu, P.O Box 4200, FI-90014, Oulu, Finland
Format: article
Version: accepted version
Access: open
Online Access: PDF Full Text (PDF, 3.2 MB)
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Language: English
Published: Elsevier, 2020
Publish Date: 2022-08-07


The correlations existing among the hot mill processing, as-coiled microstructure and mechanical properties of a Mo–Ti–V microalloyed hot rolled high strength steel were investigated in this current study. Discrete processing parameters, i.e., finish rolling temperatures (FRT) and coiling temperatures (CT), were applied and the corresponding microstructures and mechanical properties were analyzed. It was found that the FRT had only a very minor influence on either microstructures or mechanical properties. However, the CTs strongly affected both the microstructures and mechanical properties. The microstructure in the matrix was observed to change from mainly polygonal ferrite to quasi-polygonal ferrite to granular bainite and upper bainite with falling CTs, accompanied by the formation of martensite/austenite (M/A) constituents at the lower CTs. The strength appeared to be increased by the dislocations originating by the shear component of the displacive phase transformation, and by fine (Ti, Mo)C precipitates, both formed during the coiling process. Strengths reaching values as high as 1166 MPa in yield strength and 1225 MPa in tensile strength were observed in specimens after coiling at 610 °C, and the steels still had a reasonable total elongation of around 20%. However, the hole expansion ratios of these steel conditions were rather low in this study, especially for those with higher strength. Several factors appeared to contribute to the poor hole expansion ratios found in these steel conditions: the presence of coarse TiN inclusions, a large amount of strengthening precipitates and a high dislocation density as well as the presence of M/A constituents.

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Series: Materials science & engineering. A, Structural materials: properties, microstructure and processing
ISSN: 0921-5093
ISSN-E: 1873-4936
ISSN-L: 0921-5093
Volume: 796
Article number: 140048
DOI: 10.1016/j.msea.2020.140048
Type of Publication: A1 Journal article – refereed
Field of Science: 216 Materials engineering
Funding: The authors would like to thank POSCO for providing the steels and the financial support for this study.
Copyright information: © 2020 Elsevier B. V. This manuscript version is made available under the CC-BY-NC-ND 4.0 license