University of Oulu

Ali, M., Porter, D., Kömi, J., Heikkinen, E., Eissa, M., El, F., Mattar, T. (2019) The effect of electroslag remelting on the cleanliness of CrNiMoWMnV ultrahigh-strength steels. Journal of Mining and Metallurgy, Section B: Metallurgy, 55 (3), 381-395. doi:10.2298/JMMB190211042A

The effect of electroslag remelting on the cleanliness of CrNiMoWMnV ultrahigh-strength steels

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Author: Ali, M.1,2; Porter, D.1; Kömi, J.1;
Organizations: 1Materials and Mechanical Engineering, Centre for Advanced Steels Research, University of Oulu, Oulu, Finland
2Steel Technology Department, Central Metallurgical Research and Development Institute (CMRDI), Helwan, Cairo, Egypt
3Process Metallurgy Research Unit, University of Oulu, Oulu, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 2.4 MB)
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Language: English
Published: University of Belgrade, 2019
Publish Date: 2019-12-10


The cleanliness of ultrahigh-strength steels (UHSSs) without and with electroslag remelting (ESR) using a slag with the composition of 70% CaF₂, 15% Al₂O₃, and 15% CaO was studied. Three experimental heats of UHSSs with different chemical compositions were designed, melted in an induction furnace, and refined using ESR. Cast ingots were forged at temperatures between 1100 and 950°C, air cooled, and their non-metallic inclusions (NMIs) were characterized using field emission scanning electron microscopy and laser scanning confocal microscopy. Thermodynamic calculations for the expected NMIs formed in the investigated steels with and without ESR were performed using FactSage 7.2 software while HSC Chemistry version 9.6.1 was used to calculate the standard Gibbs free energies (ΔG°). As a result of ESR the total impurity levels (TIL% = O% + N% + S%) and NMI contents decreased by as much as 46 % and 62 %, respectively. The NMIs were classified into four major classes: oxides, sulphides, nitrides, and complex multiphase inclusions. ESR brings about large changes in the area percentages, number densities, maximum equivalent circle diameters, and the chemical composition of the various NMIs. Most MnS inclusions were removed although some were re-precipitated on oxide or nitride inclusions leading to multiphase inclusions with an oxide or nitride core surrounded by sulphide, e.g. (MnS.Al₂O₃) and (MnS. TiN). Also, some sulphides are modified by Ca forming (CaMn)S and CaS.Al₂O₃. Some nitrides like TiN and (TiV)N are nucleated and precipitated during the solidification phase. Al₂O₃ inclusions were formed as a result of the addition of Al as a deoxidant to the ESR slag to prevent penetration of oxygen to the molten steel.

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Series: Journal of mining and metallurgy. Section B, Metallurgy
ISSN: 1450-5339
ISSN-E: 2217-7175
ISSN-L: 1450-5339
Volume: 55
Issue: 3
Pages: 381 - 395
DOI: 10.2298/JMMB190211042A
Type of Publication: A1 Journal article – refereed
Field of Science: 216 Materials engineering
Funding: The authors acknowledge the Egyptian Ministry of Higher Education (Cultural Affairs and Missions Sector) for the financial support during this work.
Copyright information: © 2019 The Authors. The published articles will be distributed under the Creative Commons Attribution ShareAlike 4.0 International license (CC BY-SA). It is allowed to copy and redistribute the material in any medium or format, and remix, transform, and build upon it for any purpose, even commercially, as long as appropriate credit is given to the original author(s), a link to the license is provided, it is indicated if changes were made and the new work is distributed under the same license as the original. Users are required to provide full bibliographic description of the original publication (authors, article title, journal title, volume, issue, pages), as well as its DOI code. In electronic publishing, users are also required to link the content with both the original article published in Journal of Mining and Metallurgy B: Metallurgy and the license used.