University of Oulu

Koskenniska, S. & Tervo, H. & Kaijalainen, A. & Porter, D. & Kömi, J. & Mehtonen, S. & Pikkarainen, T. (2018) Relationship between inclusions and segregations in continuous cast ultrahigh-strength steel. In: Proceedings of the 10th International conference on Clean steel. 18-20 September 2018 Budapest, Hungary, 1-12.

Relationship between inclusions and segregations in continuous cast ultrahigh-strength steel

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Author: Koskenniska, S.1; Tervo, H.1; Kaijalainen, A.1;
Organizations: 1University of Oulu, Finland
2SSAB Europe Oy, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 1.6 MB)
Persistent link: http://urn.fi/urn:nbn:fi-fe2018100937892
Language: English
Published: Hungarian Mining and Metallurgical Society (OMBKE), 2018
Publish Date: 2018-10-09
Description:

Abstract

The ever-increasing demand for better steel quality necessitates the development of cleaner steels. Controlling the as-cast structure, segregation and the number, size, morphology and chemical composition of non-metallic inclusions enhances steel cleanness. This can be achieved by adjusting a wide range of operating practices throughout the steel making process. In this study, the effect of inclusions and segregations on cleanness of the pilot-scale experimental continuously cast and direct-quenched martensitic low-alloyed ultrahigh-strength steel with a tensile strength of 1850 MPa was analyzed. The investigated steel was also aluminum killed and calcium treated. Two different superheats were used to get differences in the as-cast structures and segregation patterns. Samples of these two casting scenarios were hot rolled with two different finish rolling temperatures to distinguish the possible effect of hot rolling temperature from the effect of segregation and as-cast structure. After hot rolling to a thickness of 12 mm, energy dispersive spectrometer analyses on a scanning electron microscope (SEM-EDS) were performed to characterize the inclusion types and sizes through the thickness on longitudinal cross-sections, and the results were compared to optical emission spectrometry (OES) analyses from the as-cast slab in the thickness direction. The main result of this study is that segregation affects the formation of TiN and MnS inclusions by raising the temperature at which they first form from the melt. This promotes their growth especially in the positively macrosegregated columnar-to-equiaxed transition zone and the centerline.

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Pages: 1 - 12
Host publication: Proceedings of the 10th International conference on Clean steel. 18-20 September 2018 Budapest, Hungary
Conference: Clean steel
Type of Publication: D3 Professional conference proceedings
Field of Science: 216 Materials engineering
Subjects:
Funding: The authors are grateful to DIMECC and the Finnish Funding Agency for Technology and Innovation (TEKES) for financing this work as a part of the DIMECC financing programs SIMP – System Integrated Metals Processing and FLEX – Flexible and Adaptive Operations in Metal Production.
Copyright information: © 2018 The Authors and Hungarian Mining and Metallurgical Society (OMBKE).