Investigation on Properties of Fluorine‐Free Mold Fluxes Based on CaO–Al2O3–B2O3 System

Li, Jiangling; Kong, Bowen; Galdino, Bruno; Xu, Jia; Chou, Kuo‐Chih; Liu, Qingcai; Shu, Qifeng

doi:10.1002/srin.201600485

Cited by 21 publications

(23 citation statements)

References 38 publications

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“…3,7,11) In view of the fact that CaO-Al 2 O 3 based slag has better crystallization abilities than CaO-SiO 2 basedslag, the present authors developed new kinds of F-free mould fluxes based on the CaO-Al 2 O 3 -B 2 O 3 system. 12) The viscosity values for the CaO-Al 2 O 3 -B 2 O 3 based mould fluxes were located in the scope of traditional CaO-SiO 2 based mould fluxes, whereas the melting temperatures for CaO-Al 2 O 3 -B 2 O 3 based mould fluxes are very close to those of traditional CaO-SiO 2 based ones. However, CaO-Al 2 O 3 -B 2 O 3 based mould fluxes still need further investigation for adjusting their crystallization behaviour.…”

Section: Introductionmentioning

confidence: 79%

“…According to Eqs. (10)- (12), the values of effective activation energy for samples with lower undercooling values should be more negative. In the area of low relative crystallinity, the sample 2 with w(CaO)/w(Al 2 O 3 ) = 1.0 has the highest value of effective activation energy; it agrees with the fact that it has the highest value of undercooling.…”

Section: Instantaneous Nucleationmentioning

confidence: 96%

“…From Eqs. (10) to (12), the thermodynamic barrier W should decrease with decreasing of temperature. As relative crystallinity increases, the crystallization temperature decreases, and then effective activation energy (mainly determined by -W value) should increases.…”

Section: Instantaneous Nucleationmentioning

confidence: 99%

“…The precipitation sequence of crystals in CaO-Al 2 O 3 -B 2 O 3 based F-free mould fluxes was determined in a previous work for the same samples. 12) Heat treatments at various temperatures were adopted to determine the possible precipitations in a previous work. After heat treatment, the samples were quenched and subject to SEM and XRD investigation to determine the precipitated phases.…”

Section: Dsc Analysismentioning

confidence: 99%

“…According to our previous publication, 12) the relevant technological parameters for developing mould fluxes for industrial application were discussed for similar mould fluxes compositions: viscosity at 1 300°C, melting characteristics, and crystallization temperature got from DTA curve. In the present paper, further investigation was per-formed regarding mould fluxes crystallization.…”

Section: Introductionmentioning

confidence: 99%

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Non-Isothermal Melt Crystallization Kinetics for CaO–Al2O3–B2O3 F-Free Mould Fluxes

Shu

Klug

2019

ISIJ Int.

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Efforts have been made to develop fluorine-free mould fluxes for the continuous casting of steel process. In this work the crystallization behaviour of fluorine-free mould slags based on the CaO-Al 2 O 3-B 2 O 3 system was investigated by differential scanning calorimeter (DSC) and scanning electron microscopy equipped with energy dispersive spectroscopy(SEM-EDS). The crystallization kinetics for Ca 3 Al 2 O 6 primary crystals was analysed by combining modified Avrami analysis with Friedman isoconversional method. Avrami parameter n is close to 4 for samples with the ratios w(CaO)/w(Al 2 O 3) = 1 and w(CaO)/w(Al 2 O 3) = 1.2, indicating a crystallization mechanism of continuous bulk nucleation and 3D crystal growth. The Avrami parameter n for samples with w(CaO)/w(Al 2 O 3) = 0.9 is close to 3, indicating instantaneous bulk nucleation and 3D crystal growth. The crystallization rate constant is the highest and half crystallization time is the lowest for the samples with w(CaO)/w(Al 2 O 3) = 0.9, indicating the fastest crystallization. In the initial stage, effective activation energies were mainly determined by the undercooling values. In the final stage, kinetic barrier for crystallization could have some influence on crystallization; for the investigated mould fluxes crystallization in the final stage is retarded by increasing w(CaO)/w(Al 2 O 3) ratio. Thus crystallization mechanisms were elucidated and effective activation energy of crystallization for the first crystal which precipitates from melt was determined.

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Section: Introductionmentioning

confidence: 79%

Section: Instantaneous Nucleationmentioning

confidence: 96%

Section: Instantaneous Nucleationmentioning

confidence: 99%

Section: Dsc Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Non-Isothermal Melt Crystallization Kinetics for CaO–Al2O3–B2O3 F-Free Mould Fluxes

Shu

Klug

2019

ISIJ Int.

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A Review of the Melt Structure and Crystallization Behavior of Non‐Reactive Mold Flux for the Casting of Advanced High‐Strength Steels

Wang

Zhai

Zhang

2021

steel research int.

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The non‐reactive CaO–Al2O3‐based mold flux system is proposed to avoid the reaction problems during the casting process of advanced high‐strength steels, when conventional CaO–SiO2‐based mold flux system is applied. However, new problems such as low consumption and insufficient lubrication are introduced during the industrials of CaO–Al2O3‐based mold fluxes, which is closely associated with its melt structure and crystallization behavior. Herein, the studies on the melt structure and crystallization property of CaO–Al2O3‐based mold fluxes are summarized and discussed. The structural roles of Al2O3, B2O3, and SiO2 in CaO–Al2O3‐based mold flux system are quite complex because the structural transformation occurs in aluminate network structure, such as [AlO4]5− and [AlO5]7−, and borate network structure, such as [BO3]3− and [BO4]5−, in the system. In addition, it is suggested that the addition of basic metal oxides and fluorides will strengthen the stability of network structure, due to the charge compensation effect of Li+ and Ba2+, and the strong electrostatic attraction between Al3+ and F−. On the contrary, many Al‐bearing crystal phases with high melting point precipitate in the CaO–Al2O3‐based melt, which will improve the crystallization ability of slag and deteriorate its lubrication performance.

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New Mold Slag Compositions for the Continuous Casting of Soft Steels

Kölbl

2021

steel research int.

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Several fluorine‐free mold slag compositions have already been established in the literature. In all cases, the formation of a crystalline phase exhibiting behavior similar to that of cuspidine is emphasized to control horizontal heat transfer without influencing the lubrication performance for the casting of peritectic steel grades. In contrast, for casting soft steels, glassy solidification of the slag is required. Herein, different slag compositions involving the selected oxides are developed with the help of FactSage calculations. Mixtures of pure raw materials are melted at 1673 K and quenched to 295 K. It is observed that B2O3 increases the glass‐forming ability of the slags. To obtain the glassy phase, the composition must satisfy the conditions and . For TiO2 content <10 wt%, glassy solidification is detected after quenching to room temperature. However, this phenomenon‐is not observed for slags with TiO2 content >15 wt%. Moreover, the addition of alumina and alkali oxides enhances crystallization. Based on these findings, promising mold slag compositions are designed and characterized in the laboratory using a furnace crystallization test, mineralogical investigations, and the single/double hot thermocouple technique. From the investigated mixtures, three compositions are suggested for use in continuous casting processes.

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Investigation on Properties of Fluorine‐Free Mold Fluxes Based on CaO–Al₂O₃–B₂O₃ System

Cited by 21 publications

References 38 publications

Non-Isothermal Melt Crystallization Kinetics for CaO–Al<sub>2</sub>O<sub>3</sub>–B<sub>2</sub>O<sub>3</sub> F-Free Mould Fluxes

Non-Isothermal Melt Crystallization Kinetics for CaO–Al<sub>2</sub>O<sub>3</sub>–B<sub>2</sub>O<sub>3</sub> F-Free Mould Fluxes

A Review of the Melt Structure and Crystallization Behavior of Non‐Reactive Mold Flux for the Casting of Advanced High‐Strength Steels

New Mold Slag Compositions for the Continuous Casting of Soft Steels

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