Mirco-level Insight into the Surface Tension-structure Relationship of Molten CaO–MgO–SiO2–FexO–P2O5 Slags

• Published in: ISIJ International Vol. 61; no. 11; pp. 2765 - 2772
• Main Authors: Liu, Chengjun, Zhang, Rui, Meng, Yifan, Wang, Zhen, Jiao, Shiyan, Jia, Jixiang, Min, Yi
• Format: Journal Article
• Language: English
• Published: The Iron and Steel Institute of Japan 15.11.2021
• Subjects: basic oxygen steelmaking; melt structure; microstructure mechanism; Raman spectroscopy; surface tension
• ISSN: 0915-1559; 1347-5460
• DOI: 10.2355/isijinternational.ISIJINT-2021-236

For comprehensive understanding and control of the properties of CaO–MgO–SiO2–FexO–P2O5 slags, thorough investigation of the surface tension-structure relationship is required. In this study, the structural behaviors of components were analyzed by Raman spectroscopy, and the transformation mechanism of surface tension as a function of composition was clarified. The results showed that with CaO/SiO2 increasing from 0.5 to 2.0, O2– resulted in the progressive breaking of bridging oxygen bonds in [SiO4]- and [PO4]-tetrahedrons, and Ca2+ contributed to the stabilization of [FeO4]-tetrahedrons, thereby promoting the transformation from [FeO6]-octahedrons to [FeO4]-tetrahedrons. Although the network-forming ability of Fe3+ was enhanced, the overall non-bridging oxygen number still showed a gradual increase and thus the non-bridging oxygen bonds with higher unsatisfied energy in the surface layer led to an increase in surface tension. Nonetheless, the increasing P=O bonds effectively reduced surface tension due to its stable configuration in the range of CaO/SiO2 = 0.5–1.0, diminishing the increasing magnitude of surface tension. Furthermore, a strong linear relationship between surface tension and the logarithm of structural parameters was found. On this basis, a surface tension estimation equation applied to the CaO–MgO–SiO2–FexO–P2O5-based system was established in terms of the deconvolution results of the melt structures.