Structure of Solidified Films of CaO-SiO2-Na2O Based Low-Fluorine Mold Flux

Jianhua Zeng,Shengping He,Xinchen You,Xiao Long,Min Li,Qiangqiang Wang

doi:10.3390/met9010093

Jianhua Zeng, Shengping He + Show 4 more

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https://doi.org/10.3390/met9010093

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Journal: Metals	Publication Date: Jan 16, 2019
Citations: 3	License type: CC BY 4.0

Affiliation: Chongqing University, Guizhou Institute of Technology

Abstract

As an essential synthetic material used in the continuous casting of steels, mold fluxes improve the surface quality of steel slabs. In this study, a CaO-SiO2-Na2O-based low-fluorine mold flux was solidified by an improved water-cooled copper probe with different temperatures of molten flux and different probe immersion times. The heat flux through solid films and the film structures were calculated and inspected, respectively. Internal cracks (formed in the glassy layer of films during solidification) were observed. The formation and evolution of those cracks contributed to the unstable heat flux density. The roughness of the surface in contact with the water-cooled copper probe formed as films were still glassy and the roughness had no causal relationship with crystallization or devitrification. Combeite with columnar and faceted dendritic shapes were the main crystal in the film.

Highlights

In the continuous casting of steels, mold fluxes control the heat flux from steel shells to the mold [1,2,3] by forming a solid slag film
The usual method to solve this problem is the use of mold fluxes to lower the heat flux from initial steel shells to the mold near meniscus
Based on previous approaches [9,10], the precipitation of cuspidine in slag films is widely considered as a major contribution of high-basicity mold fluxes to decrease the heat flux

Summary

Introduction

In the continuous casting of steels, mold fluxes control the heat flux from steel shells to the mold [1,2,3] by forming a solid slag film. The usual method to solve this problem is the use of mold fluxes to lower the heat flux from initial steel shells to the mold near meniscus. As an important element in fusion agents (e.g., NaF, CaF2 , etc.), fluorine simplifies the microstructure of molten fluxes, decreases its high-temperature viscosities, and promotes the formation of cuspidine (3CaO·2SiO2 ·CaF2 ) in solid slag films [6,7,8]. Based on previous approaches [9,10], the precipitation of cuspidine in slag films is widely considered as a major contribution of high-basicity mold fluxes to decrease the heat flux. These gases potentially pollute the environment and damage the health of workers

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Results

Conclusion