Structure and viscosity of CaO–Al2O3–B2O3–BaO slags with varying mass ratio of BaO to CaO

Harishchandra Singh,Zhifeng Wang,Marko Huttula,Graham King,Timo Fabritius,Wei Cao,Qifeng Shu,Ziqing Liang

doi:10.1111/jace.17877

Abstract

AbstractThe structure of CaO–Al2O3–B2O3–BaO glassy slags with varying mass ratio of BaO to CaO has been investigated by Raman spectroscopy, 11B and 27Al magic angle spinning nuclear magnetic resonance (MAS‐NMR) spectroscopy and atomic pair distribution function (PDF). 11B MAS‐NMR spectra reveal the dominant coordination of boron as trigonal. Both simulations on 11B MAS‐NMR spectra and Raman spectroscopy indicate the presence of orthoborate as the primary borate group with a few borate groups with one bridging oxygen and minor four‐coordinated boron sites. 27Al MAS‐NMR and PDF show the Al coordination as tetrahedral. Raman spectral study shows that the transverse vibration of AlIV–O–AlIV and AlIV–O–BIII, stretching vibration of aluminate structural units and vibration of orthoborate and pyroborate structural groups. A broader distribution of Al–O bond lengths in PDF also supports the enhanced network connectivity. Viscosity measurements show the increase in viscosity of molten slags with increasing mass ratio of BaO to CaO, which further attributes to the enhanced degree of polymerization of the aluminate network.

Highlights

Advanced high- strength steel (AHSS), including transformation-induced plasticity steel and twinning-induced plasticity steel have received intense interest in recent years because of their excellent combination of high strength, good ductility, and lower density.[1,2] In transportation applications, AHSS can be used to design structures with smaller material thicknesses, which saves weight and thereby decreases the fuel consumption and CO2 emissions of vehicles.[3]one of the challenging concerns for production of AHSS in industrial scale is the strong reaction between steel and mold fluxes during continuous casting,[4] which typically leads to problems of lubrication and heat transfer between mold and solidifying steel.[5]
One of the challenging concerns for production of AHSS in industrial scale is the strong reaction between steel and mold fluxes during continuous casting,[4] which typically leads to problems of lubrication and heat transfer between mold and solidifying steel.[5]
Wang et al.[13] investigated the effect of substitution of CaO with BaO on the viscosity and structure of CaO– BaO–SiO2–MgO–Al2O3 glass. These results showed that the viscosity of molten glass increased with increasing BaO substitution, which was correlated to an increase in the degree of polymerization of the glass

Summary

Introduction

One of the challenging concerns for production of AHSS in industrial scale is the strong reaction between steel and mold fluxes during continuous casting,[4] which typically leads to problems of lubrication and heat transfer between mold and solidifying steel.[5] Mold fluxes play an indispensable role in continuous casting of steels and provide two critical functions as lubricating the steel shell and controlling the horizontal heat transfer. One of the most important tasks for the production of AHSS is to develop mold fluxes that could meet the demand of smooth casting of steel. One solution for this is to develop nonreactive

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Discussion

Conclusion