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Article

Characterization of Coarse-Grained Heat-Affected Zones in Al and Ti-Deoxidized Offshore Steels

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Materials and Mechanical Engineering, Centre for Advanced Steel Research, University of Oulu, P.O. Box 4200, FI-90014 Oulu, Finland
2
Process Metallurgy Research Unit, Centre for Advanced Steel Research, University of Oulu, P.O. Box 4300, FI-90014 Oulu, Finland
3
SSAB Europe, Rautaruukintie 155, P.O. Box 93, FI-92101 Raahe, Finland
*
Author to whom correspondence should be addressed.
Metals 2020, 10(8), 1096; https://doi.org/10.3390/met10081096
Received: 20 July 2020 / Revised: 7 August 2020 / Accepted: 11 August 2020 / Published: 13 August 2020
(This article belongs to the Special Issue Inclusion/Precipitate Engineering in Steels)
Deterioration of the toughness in heat-affected zones (HAZs) due to the thermal cycles caused by welding is a known problem in offshore steels. Acicular ferrite (AF) in the HAZ is generally considered beneficial regarding the toughness. Three experimental steels were studied in order to find optimal conditions for the AF formation in the coarse-grained heat-affected zone (CGHAZ). One of the steels was Al-deoxidized, while the other two were Ti-deoxidized. The main focus was to distinguish whether the deoxidation practice affected the AF formation in the simulated CGHAZ. First, two different peak temperatures and prolonged annealing were used to study the prior austenite grain coarsening. Then, the effect of welding heat input was studied by applying three cooling times from 800 °C to 500 °C in a Gleeble thermomechanical simulator. The materials were characterized using electron microscopy, energy-dispersive X-ray spectrometry, and electron backscatter diffraction. The Mn depletion along the matrix-particle interface was modelled and measured. It was found that AF formed in the simulated CGHAZ of one of the Ti-deoxidized steels and its fraction increased with increasing cooling time. In this steel, the inclusions consisted mainly of small (1–4 μm) TiOx-MnS, and the tendency for prior austenite grain coarsening was the highest. View Full-Text
Keywords: CGHAZ; acicular ferrite; Ti-deoxidized steel; inclusions; microstructure; prior austenite morphology CGHAZ; acicular ferrite; Ti-deoxidized steel; inclusions; microstructure; prior austenite morphology
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MDPI and ACS Style

Tervo, H.; Kaijalainen, A.; Javaheri, V.; Kolli, S.; Alatarvas, T.; Anttila, S.; Kömi, J. Characterization of Coarse-Grained Heat-Affected Zones in Al and Ti-Deoxidized Offshore Steels. Metals 2020, 10, 1096. https://doi.org/10.3390/met10081096

AMA Style

Tervo H, Kaijalainen A, Javaheri V, Kolli S, Alatarvas T, Anttila S, Kömi J. Characterization of Coarse-Grained Heat-Affected Zones in Al and Ti-Deoxidized Offshore Steels. Metals. 2020; 10(8):1096. https://doi.org/10.3390/met10081096

Chicago/Turabian Style

Tervo, Henri, Antti Kaijalainen, Vahid Javaheri, Satish Kolli, Tuomas Alatarvas, Severi Anttila, and Jukka Kömi. 2020. "Characterization of Coarse-Grained Heat-Affected Zones in Al and Ti-Deoxidized Offshore Steels" Metals 10, no. 8: 1096. https://doi.org/10.3390/met10081096

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