University of Oulu

Koskenniska, S., Kaijalainen, A., Pikkarainen, T. et al. Effect of As-Cast Structure and Macrosegregation on Mechanical Properties in Direct-Quenched Low-Alloy Ultrahigh-Strength Steel. Metall Mater Trans B (2020).

Effect of as-cast structure and macrosegregation on mechanical properties in direct-quenched low-alloy ultrahigh-strength steel

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Author: Koskenniska, S.; Kaijalainen, A.; Pikkarainen, T.1;
Organizations: 1SSAB Europe Oy, Rautaruukintie 155, P.O. Box 93, 92101, Raahe, Finland
2Materials and Mechanical Engineering, Centre for Advanced Steel Research, University of Oulu, P.O. Box 8000, 90014, Oulu, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 5 MB)
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Language: English
Published: Springer Nature, 2020
Publish Date: 2020-11-03


The effect of as-cast structure and macrosegregation on the mechanical properties of a direct-quenched low-alloy martensitic ultrahigh-strength aluminum killed and calcium treated steel cast at different superheats was studied. Samples from the castings were laboratory hot rolled with two different finishing rolling temperatures to distinguish the effect of hot rolling. Using optical emission spectrometry, the steel composition was analyzed as a function of slab thickness in order to detect the variations in steel chemistry due to macrosegregation. Further, hardness profiles, prior austenite grain sizes and tensile and impact toughness were determined for the hot-rolled specimens. It was found that interdendritic segregation was more intense at the higher superheat, which led to more pronounced positive segregation in the columnar-to-equiaxed transition (CET) zone, and negative segregation between CET and the centerline. These macrosegregation patterns were inherited by the hot-rolled samples causing local variations in hardness, which followed the variations in carbon content. However, altering the superheat had a minor effect on the nominal transformed microstructures and nominal prior austenite grain sizes. This occurred because of the interdendritic segregation induced composition variations both enlarged and decreased by turns the grain sizes. The CET also reduced measured impact toughness values.

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Series: Metallurgical and materials transactions. B, Process metallurgy and materials processing science
ISSN: 1073-5615
ISSN-E: 1543-1916
ISSN-L: 1073-5615
Volume: In press
DOI: 10.1007/s11663-020-01997-4
Type of Publication: A1 Journal article – refereed
Field of Science: 216 Materials engineering
Funding: We gratefully acknowledge the financial support from the Finnish funding agency for innovation Tekes and the companies participating in the program. Open access funding provided by University of Oulu including Oulu University Hospital.
Copyright information: © The Author(s) 2020. Open Access. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit