Effect of Substituting CaO with BaO and CaO/Al2O3 Ratio on the Viscosity of CaO–BaO–Al2O3–CaF2–Li2O Mold Flux System

Zhirong Li,Qian Wang,Qiangqiang Wang,Shengping He,Xinchen You,Min Li

doi:10.3390/met9020142

Abstract

The effect of substituting CaO with BaO and CaO/Al2O3 ratio on the viscosity of CaO–BaO–Al2O3–CaF2–Li2O mold flux system was studied by rotational viscosity method. The results showed that the viscosity increased with increasing BaO as a substitute for CaO, while the viscosity decreased with the increase in CaO/Al2O3 ratio. The viscous activation energy of the slags is from 92.1 kJ·mol−1 to 133.4 kJ·mol−1. Either the Arhenius or the Weymann–Frenkel equation can be applied to establish the viscosity prediction model. In this paper, the Weymann–Frenkel equation and a new optical basicity with regard to Al2O3 as an acidic oxide were applied to the modified NPL model for predicting the viscosity of CaO–BaO–Al2O3–CaF2–Li2O mold flux system. The estimated viscosity is in good agreement with the measured viscosity.

Highlights

High Mn-high Al steel, exemplified by twin-induced plasticity (TWIP) steel, has high strength and good ductility, as well as a smaller density compared with plain steels due to high contents of aluminum and manganese
It can be seen that the viscosity of the slags increases gradually with increasing BaO as a substitute for CaO
This is consistent with the trend observed by Wang et al [31] for a CaO–BaO–SiO2 –MgO–Al2 O3 slag system and Sukenaga et al [32]

Summary

Introduction

High Mn-high Al steel, exemplified by twin-induced plasticity (TWIP) steel, has high strength and good ductility, as well as a smaller density compared with plain steels due to high contents of aluminum and manganese. This perfectly accords with next-generation steel for automobiles, the development of which is continuously devoted to pursuing safety and energy conservation and environmental protection [1,2]. The high aluminum content, is an unprecedented challenge to the production of high Mn-high Al steel using continuous casting, and the key to the solution for this is to select a proper mold flux [3]. With a substantial change of components, the physical properties of the slag, such as melting temperature and viscosity, will change dramatically, deteriorating the lubrication and heat transfer of slags and further resulting in all kinds of casting defects and even casting interruption [6,7,8,9,10].

Methods

Results

Conclusion