A Review of Fluorine-free Mold Flux Development

Wang, Wanlin; Cai, Di; Zhang, Lei

doi:10.2355/isijinternational.isijint-2018-232

Cited by 31 publications

(17 citation statements)

References 47 publications

(66 reference statements)

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“…Furthermore, it causes the corrosion of the continuous casting machine, because hydrofluoric acid is generated from mold flux; it increases dramatically the corrosion rate especially below the mold where there is a high amount of water accelerating the process. [3][4][5][6][7] This context makes the elimination of fluorine of mold fluxes composition a very important industry demand.…”

Section: Introductionmentioning

confidence: 99%

“…Some oxides as alternatives to replace CaF 2 have been tried, mainly TiO 2 , B 2 O 3 and Na 2 O. 7) For billet casting, steelmakers frequently use high viscosity mold fluxes to overcome problems such as slag entrapment and submerged entry nozzle (SEN) erosion. In this case, crystallization kinetics does not need to be addressed when developing fluorine-free mold fluxes, since crystallization rate is very low; increase in Na 2 O content is a good choice to compensate for fluorine removal.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Crystallization Control for Fluorine-free Mold Fluxes: Effect of Na<sub>2</sub>O Content on Non-isothermal Melt Crystallization Kinetics

et al. 2020

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Crystallization Control for Fluorine-free Mold Fluxes: Effect of Na<sub>2</sub>O Content on Non-isothermal Melt Crystallization Kinetics

et al. 2020

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“…Other oxides, such as Na 2 O, K 2 O, Li 2 O, MgO, MnO, B 2 O 3 and TiO 2 , have also been added into multicomponent mold flux systems to compensate for the negative impact on the mold flux properties with lower fluoride contents, resulting in primary crystalline phases of calcium borosilicate (Ca 11 Si 4 B 2 O 22 ) and perovskite (CaTiO 3 ) to substitute the typical cuspidine phase in CaO-SiO 2 -based mold fluxes. [37][38][39][40] As a result of the recently developed highly alloyed steels, greater customer expectations, and increased green processing needs, the requirements and compositions of mold fluxes have undergone significant changes. Aggressive reactions of the slag and the dissolved elements in the metal often occur for these special steels, resulting in significant compositional changes.…”

Section: Classification and Trends For Mold Flux Developmentmentioning

confidence: 99%

Review on the High-Temperature Thermophysical Properties of Continuous Casting Mold Fluxes for Highly Alloyed Steels

Wang

Sohn

2020

ISIJ Int.

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Several recently developed highly alloyed steel grades have shown unsurpassed performance in terms of physical, chemical, and electromagnetic properties. However, broader commercialization of these steels has been hampered by limitations in mold flux performance. Newly developed steels containing considerable amounts of dissolved Al, Mn, and Ti actively react with typical CaO-SiO 2-based mold fluxes, which severely changes the composition and subsequently the thermophysical properties of the mold flux that determine the external and internal quality of the as-cast steels. These dynamic changes result in nonuniform heat transfer, lubrication issues, surface defects, and caster breakouts. This work critically assesses the current status of the high-temperature thermophysical properties of CaO-SiO 2-based and CaO-Al 2 O 3based mold fluxes intended for use in casting highly alloyed steel grades. Thermophysical properties, including viscosity, crystallization, thermal conductivity, and heat flux, have been evaluated. The effect of compositional variables including CaO/SiO 2 , CaO/Al 2 O 3 , and Al 2 O 3 /SiO 2 mass ratios and the additions of CaF 2 , B 2 O 3 , Li 2 O, K 2 O, Na 2 O, TiO 2 , and BaO on these high-temperature thermophysical properties are discussed.

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“…Therefore, it is urgent to look for substitutes to replace the fluorides in mold flux. During the development of fluorine-free mold fluxes, several oxides, like Na 2 O, K 2 O, Li 2 O, TiO 2 , B 2 O 3 , are used to compensate the negative effects caused by the absence of fluorides [7][8][9][10][11][12]. However, the viscosity and crystallization properties of fluorine-free mold fluxes are not appropriate for continuous casting of high carbon steel and crack sensitive steel [13].…”

Section: Introductionmentioning

confidence: 99%

Effect of Basicity on the Structure, Viscosity and Crystallization of CaO-SiO2-B2O3 Based Mold Fluxes

Sadaf

Zhong

et al. 2020

Metals

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In this study, the structure, viscosity characteristics, and crystallization behavior of CaO-SiO2-B2O3 based melts were studied combining molecular dynamics (MD) simulation, Fourier transform infrared (FTIR) spectroscopy, rotating viscometer test, and FactSage thermodynamic calculation. The results showed that, in the ternary CaO-SiO2-B2O3 glass system, stable structural units of [SiO4]4− tetrahedral, [BO3]3− trihedral and [BO4]5− tetrahedral were formed, and the Si-O and B-O structure depolymerize with the basicity increase from 1.15 to 1.25, then the B-O structure become complex with the basicity further increase to 1.35. In fluorine-free mold fluxes, with the basicity increases, the viscosity at 1300 °C increases, the liquidus temperature decreases and then increases, the network structure polymerizes, it indicates that the structural complexity rather than the melting property change plays a predominant role in increasing the viscosity at 1300 °C. Moreover, due to the changes in crystallization phase and solid solution ratio, the viscosity-temperature curve of fluorine-free slag shows the characteristics of alkaline slag and the break temperature increase with the basicity increase. The MD simulation, FTIR experiment, viscosity test, and FactSage calculation results are verified and complemented each other.

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A Review of Fluorine-free Mold Flux Development

Cited by 31 publications

References 47 publications

Crystallization Control for Fluorine-free Mold Fluxes: Effect of Na<sub>2</sub>O Content on Non-isothermal Melt Crystallization Kinetics

Crystallization Control for Fluorine-free Mold Fluxes: Effect of Na<sub>2</sub>O Content on Non-isothermal Melt Crystallization Kinetics

Review on the High-Temperature Thermophysical Properties of Continuous Casting Mold Fluxes for Highly Alloyed Steels

Effect of Basicity on the Structure, Viscosity and Crystallization of CaO-SiO2-B2O3 Based Mold Fluxes

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