A Raman and Multinuclear 29Si, 27Al, and 19F NMR Study on the Structural Roles of CaF2 in SiO2–CaO–Al2O3-based Welding Fluxes

The efficacy and efficiency of submerged arc welding (SAW) are largely dictated by the physicochemical properties of the employed welding fluxes, including melting point, viscosity, and activity, etc ., which are inherently rooted in the microstructure of the fluxes. SiO 2 –CaO–Al 2 O 3 -based fluxe...

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Bibliographic Details
Published in:Metallurgical and materials transactions. B, Process metallurgy and materials processing science Process metallurgy and materials processing science, 2022-02, Vol.53 (1), p.232-241
Main Authors: Tian, Huiyu, Wang, Zhanjun, Zhao, Tan, Wang, Cong
Format: Article
Language:English
Subjects:
Aluminum oxide
Calcium fluoride
Calcium oxide
Characterization and Evaluation of Materials
Chemistry and Materials Science
Depolymerization
High strength low alloy steels
Materials Science
Melting points
Metallic Materials
Nanotechnology
NMR
Nuclear magnetic resonance
Original Research Article
Silicon dioxide
Structural Materials
Submerged arc welding
Surfaces and Interfaces
Tetrahedra
Thin Films
Welding fluxes
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Summary:The efficacy and efficiency of submerged arc welding (SAW) are largely dictated by the physicochemical properties of the employed welding fluxes, including melting point, viscosity, and activity, etc ., which are inherently rooted in the microstructure of the fluxes. SiO 2 –CaO–Al 2 O 3 -based fluxes are widely employed for welding high strength low alloy (HSLA) steels. In the present study, the structural roles of CaF 2 on SiO 2 –CaO–Al 2 O 3 -based welding fluxes have been systematically investigated through Raman and magic angle spinning-nuclear magnetic resonance (MAS-NMR) techniques. The results showed that originally intact flux structures depolymerized upon increasing content of CaF 2 . Raman and 29 Si NMR results demonstrated that Q 2 (Q n , n is the number of bridging oxygens (O 0 ) in one [SiO 4 ]-tetrahedron) increased at the cost of Q 3 (1Al) (Q n ( m Al), m means the number of neighboring aluminate groups), which could be well explained by the interruption of the Si-O-Al linkages. Moreover, as confirmed by 27 Al and 19 F NMR results, the proportion of AlF 6 species increased from 9.9 to 34.2 pct, indicating the substitution of Al–F for Al–O bonds and the depolymerization of the flux structure. The unique behavior of F may offer a theoretical basis for fine-tuning structural unit mobility and element transfer behaviors during the actual welding process.
ISSN:1073-5615
1543-1916
DOI:10.1007/s11663-021-02359-4