University of Oulu

Shu, Q., Li, Q., Medeiros, S.L.S. et al. Development of Non-reactive F-Free Mold Fluxes for High Aluminum Steels: Non-isothermal Crystallization Kinetics for Devitrification. Metall and Materi Trans B 51, 1169–1180 (2020). https://doi.org/10.1007/s11663-020-01838-4

Development of non-reactive F-free mold fluxes for high aluminum steels : non-isothermal crystallization kinetics for devitrification

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Author: Shu, Qifeng1,2; Li, Qiangq2; Santos Medeiros, Samuel Lucas3;
Organizations: 1Research Unit of Process Metallurgy, University of Oulu, 90014, Oulu, Finland
2School of Metallurgical and Ecological Engineering, University of Science and Technology, Beijing, Beijing, 100083, China
3Postgraduate Program in Materials Science and Engineering, Federal University of Ceará, Fortaleza, Ceará, CEP 60440-554, Brazil
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 3.1 MB)
Persistent link: http://urn.fi/urn:nbn:fi-fe2020060942405
Language: English
Published: Springer Nature, 2020
Publish Date: 2020-06-09
Description:

Abstract

It is necessary to study crystallization from glass (devitrification) for non-reactive F-free CaO-Al₂O₃ based mold fluxes; this is especially important for the development of mold fluxes for continuous casting of high aluminum steels. To the knowledge of the authors, there is no report in the literature regarding devitrification of F-free mold fluxes based on the CaO-Al₂O₃-B₂O₃-Na₂O-Li₂O system. Therefore, crystallization kinetics for particular compositions in this system, with different w(CaO)/w(Al₂O₃) ratios, was investigated by Differential Scanning Calorimeter, Field-Emission Environmental Scanning Electron Microscopy / Energy Dispersive Spectroscopy, and X-ray Diffraction techniques. The first crystal, which precipitates during heating from glass, is Ca₁₂Al₁₄O₃₃, followed by CaO. For the first crystal, which precipitates as plate-like (2-dimensional), it was found that, when using the Matusita–Sakka model, agreement between the calculated Avrami parameters and the micrographs obtained from electron microscope was reached. In the same way, agreement was found for the second event—CaO precipitation—which grows 2-dimensionally or 3-dimensionally, depending on the w(CaO)/w(Al₂O₃) ratio. The most important event (in terms of energy liberated and amount of crystals) is Ca₁₂Al₁₄O₃₃ precipitation. For this event, the effective activation energy for crystallization, EG, decreases with the increase of w(CaO)/w(Al₂O₃) ratio. The activation energy for crystallization reflects the energy barrier for crystallization. Thus, it can be concluded that mold fluxes crystallization during heating is enhanced when increasing the w(CaO)/w(Al₂O₃) ratio, for constant contents of B₂O₃, Na₂O, and Li₂O.

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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: 51
Issue: 3
Pages: 1169 - 1180
DOI: 10.1007/s11663-020-01838-4
OADOI: https://oadoi.org/10.1007/s11663-020-01838-4
Type of Publication: A1 Journal article – refereed
Field of Science: 216 Materials engineering
Subjects:
Funding: Open access funding provided by University of Oulu including Oulu University Hospital. Financial support from Natural Science Foundation of China (NSFC Contract No. 51774026), from Academy of Finland for Genome of Steel Grant (No. 311934), and from Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brasil (CAPES, Finance Code 001) is gratefully acknowledged.
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