University of Oulu

Tervo H., Mourujärvi J., Kaijalainen A., Kömi J. (2018) Mechanical Properties in the Physically Simulated Heat-Affected Zones of 500 MPa Offshore Steel for Arctic Conditions. In: Jármai K., Bolló B. (eds) Vehicle and Automotive Engineering 2. VAE 2018. Lecture Notes in Mechanical Engineering. Springer, Cham

Mechanical properties in the physically simulated heat-affected zones of 500 MPa offshore steel for arctic conditions

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Author: Tervo, Henri1; Mourujärvi, Juho1; Kaijalainen, Antti1;
Organizations: 1Materials and Production Engineering, P.O Box 4200, FI-90014 University of Oulu, Oulu
Format: article
Version: accepted version
Access: embargoed
Persistent link: http://urn.fi/urn:nbn:fi-fe2018051824210
Language: English
Published: Springer Nature, 2018
Publish Date: 2019-05-10
Description:

Abstract

Offshore steels for the arctic conditions have an increasing demand due to the opening of new oil fields in the Arctic Ocean. However, the requirements for these steels are extremely demanding, as they need to maintain the desired properties in harsh arctic conditions. Additionally, these requirements need to be achieved also in heat-affected zones caused by the welding. In this study the heat-affected zones were created using the physical simulation, so that the zones would be wide enough for reliable mechanical testing.

Continuous cast 500 MPa offshore steel was hot rolled in the laboratory hot rolling mill to find out the mechanical properties of the base metal. The physically simulated heat-affected zones were studied using Gleeble 3800. Two different cooling times from 800°C to 500°C (t8/5) were used in order to simulate two different welding methods with different heat inputs. Microstructure of both base materials and simulated heat-affected zones were studied using scanning electron microscope and laser scanning confocal microscope. Charpy V-notch impact toughness and hardness profiles were determined of both base material and simulated heat-affected zones.

The base metal microstructure was ferritic with some lath-like bainitic features. Minor changes were noted in the microstructure of physically simulated inter-critical heat-affected zone (ICHAZ), while in physically simulated coarse grained heat-affected zone (CGHAZ) the prior austenite grains had coarsened and the transformation microstructure consisted of lath-like features of bainite and in case of a shorter t8/5 of 6 s, even martensite. It was found out that the critical location regarding the impact toughness in arctic temperatures was found out to be CGHAZ, while the impact toughness of ICHAZ did not differ remarkably from that of the base material. The CGHAZ impact toughness was weaker with t8/5 = 30 s than with t8/5 = 6 s indicating that lower heat input welding methods are more beneficial for this material.

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Series: Lecture notes in mechanical engineering
ISSN: 2195-4356
ISSN-L: 2195-4356
ISBN: 978-3-319-75677-6
ISBN Print: 978-3-319-75676-9
Pages: 779 - 788
DOI: 10.1007/978-3-319-75677-6_66
OADOI: https://oadoi.org/10.1007/978-3-319-75677-6_66
Host publication: Vehicle and Automotive Engineering 2 : Proceedings of the 2nd VAE2018, Miskolc, Hungary
Host publication editor: Jarmai, Karoly
Betti, Bollo
Conference: 2nd VAE2018, Miskolc, Hungary
Type of Publication: A4 Article in conference proceedings
Field of Science: 216 Materials engineering
Subjects:
Funding: The authors are grateful to the Finnish Funding Agency for Technology and Innovation (Tekes) for financing this work as a part of the research project FLEX – Flexible and Adaptive Operations in Metal Production.
Copyright information: © Springer International Publishing AG, part of Springer Nature 2018. This is a post-peer-review, pre-copyedit version of an article published in Lecture Notes in Mechanical Engineering. The final authenticated version is available online at: http://dx.doi.org/10.1007/978-3-319-75677-6_66.