University of Oulu

Tervo, H.; Kaijalainen, A.; Javaheri, V.; Ali, M.; Alatarvas, T.; Mehtonen, M.; Anttila, S.; Kömi, J. Comparison of Impact Toughness in Simulated Coarse-Grained Heat-Affected Zone of Al-Deoxidized and Ti-Deoxidized Offshore Steels. Metals 2021, 11, 1783.

Comparison of impact toughness in simulated coarse-grained heat-affected zone of Al-deoxidized and Ti-deoxidized offshore steels

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Author: Tervo, Henri1; Kaijalainen, Antti1; Javaheri, Vahid1;
Organizations: 1Materials and Mechanical Engineering, Centre for Advanced Steel Research, University of Oulu, P.O. Box 4200, FI-90014 Oulu, Finland
2Steel Technology Department, Central Metallurgical Research and Development Institute, Helwan 11421, Egypt
3Process Metallurgy Research Unit, Centre for Advanced Steel Research, University of Oulu, P.O. Box 4300, FI-90014 Oulu, Finland
4SSAB Europe, Rautaruukintie 155, P.O. Box 93, FI-92101 Raahe, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 6.7 MB)
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Language: English
Published: Multidisciplinary Digital Publishing Institute, 2021
Publish Date: 2021-12-16


The presence of acicular ferrite (AF) in the heat-affected zone (HAZ) of steels used offshore is generally seen as beneficial for toughness. In this study, the effects of varying fractions of AF (0–49 vol.%) were assessed in the simulated, unaltered and coarse-grained heat-affected zones (CGHAZ) of three experimental steels. Two steels were deoxidized using Ti and one using Al. The characterization was carried out by using electron microscopy, energy-dispersive X-ray spectrometry, electron backscatter diffraction and X-ray diffraction. The fraction of AF varied with the heat input and cooling time applied in the Gleeble thermomechanical simulator. AF was present in one of the Ti-deoxidized steels with all the applied cooling times, and its fraction increased with increasing cooling time. However, in other materials, only a small fraction (13–22%) of AF was present and only when the longest cooling time was applied. The impact toughness of the simulated specimens was evaluated using instrumented Charpy V-notch testing. Contrary to the assumption, the highest impact toughness was obtained in the conventional Al-deoxidized steel with little or no AF in the microstructure, while the variants with the highest fraction of AF had the lowest impact toughness. It was concluded that the coarser microstructural and inclusion features of the steels with AF and also the fraction of AF may not have been great enough to improve the CGHAZ toughness of the steels investigated.

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Series: Metals
ISSN: 2075-4701
ISSN-E: 2075-4701
ISSN-L: 2075-4701
Volume: 11
Issue: 11
Article number: 1783
DOI: 10.3390/met11111783
Type of Publication: A1 Journal article – refereed
Field of Science: 216 Materials engineering
214 Mechanical engineering
Funding: The authors are grateful to Business Finland for financing this work as a part of the research project 7537/31/2018 (ISA—Intelligent Steel Applications).
Copyright information: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (