Effect of Na2O on the Interfacial Reaction between CaO–Al2O3 based Mold Fluxes and High-Al Steel at 1500°C

• Published in: ISIJ International 2019/12/15, Vol.59(12), pp.2247-2255
• Main Authors: Yang, Jian, Cui, Hongji, Zhang, Jianqiang, Ostrovski, Oleg, Zhang, Chen, Cai, Dexiang
• Format: Article
• Language: English
• Subjects: CaO–Al2O3-based mold flux; emulsification; flux-steel reaction; high-Al steel; Na2O
• ISSN: 0915-1559; 1347-5460
• DOI: 10.2355/isijinternational.ISIJINT-2019-257

The use of traditional CaO–SiO2-based mold fluxes for the continuous casting of high-Al steel is problematic due to the reaction between [Al] from liquid steel and SiO2 from the CaO–SiO2-based fluxes. CaO–Al2O3-based mold fluxes were proposed to mitigate the interfacial reaction. However, these fluxes contain fluxing agents, such as Na2O, B2O3, etc., which react with [Al] in liquid steel. This article investigates the effect of Na2O content in CaO–Al2O3-based mold fluxes on the reaction between high-Al steel and mold fluxes at 1500°C. The flux-steel reaction led to the accumulation of Al2O3 and reduction of SiO2, Na2O and B2O3 in the fluxes. The increase of the initial Na2O concentration enhanced the rates of Al2O3 accumulation and Na2O reduction; the [Al] concentration in liquid steel also decreased with the increase of initial Na2O content. In the early stage of the reaction, emulsification was observed at the flux-steel interface, which was affected by the precipitation of solid phases along the reaction interface.