Effects of CeO2 on Viscosity, Structure, and Crystallization of Mold Fluxes for Casting Rare Earths Alloyed Steels

Zeyun Cai,Longfei Li,Xiaokang Cui,Zhen Liu,Bo Song

doi:10.3390/met9030333

Abstract

The CaO-Al2O3-based mold fluxes are proposed for the Ce-bearing heavy rail steel continuous casting because of the low reactivity. Effects of CeO2 on the melting temperature, the viscous property, and the crystallization behavior of the CaO-Al2O3-Li2O-B2O3 mold fluxes were studied using hemisphere melting point method, rotating cylinder method, and X-ray diffraction (XRD) in the present work. The microstructure of the mold fluxes was analyzed by Fourier-transform infrared spectroscopy (FTIR). The results revealed that the addition of CeO2 would increase the melting temperature, but decrease the viscosity at each temperature due to its influence on increasing the depolymerization of the mold fluxes at high temperature. The precipitation of CaO was restrained and CaCeAlO4 generated with increasing CeO2 content since the crystal phases were affected by the microstructure of the melts. The change of the crystalline phases in mold fluxes influences the break temperature and the viscosity of the mold fluxes below the break temperature. These results obtained can provide guidelines for designing new mold fluxes for casting rare earth alloy heavy rail steels.

Highlights

Rare earth is widely used for the production of rare earth treated steels and rare earth alloyed steels as an effective additive [1,2,3]
The CaO-Al2 O3 -based mold fluxes were investigated in previous literature, which reported that the slag-metal interface reaction was reduced by 75%
CaF2 was usually used in mold fluxes to control the melting temperature, viscosity, and crystallization [8,9], but its fluoride compounds pollute the environment [10]

Summary

Introduction

Rare earth is widely used for the production of rare earth treated steels and rare earth alloyed steels as an effective additive [1,2,3]. The increase of the generated rare earth oxides has effects on melting temperature, viscous property, and crystallization behavior of the mold fluxes according to the previous studies [5,6,7]. In order to restrain the slag-metal interface reaction in the continuous casting of the rare earth alloy heavy rail steels, the concept of the mold fluxes with low reactivity was proposed. The CaO-Al2 O3 -based mold fluxes were investigated in previous literature, which reported that the slag-metal interface reaction was reduced by 75%. CaF2 was usually used in mold fluxes to control the melting temperature, viscosity, and crystallization [8,9], but its fluoride compounds pollute the environment [10]. Some researchers studied the influences of CaO/Al2 O3 ratio and the contents of Li2 O and B2 O3 on the viscosity and Metals 2019, 9, 333; doi:10.3390/met9030333 www.mdpi.com/journal/metals

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