Effect of CaF2, B2O3 and the CaO/SiO2 mass ratio on the viscosity and structure of B2O3‐containing calcium‐silicate‐based melts

Kim, Gi Hyun; Sohn, Il

doi:10.1111/jace.16526

Cited by 47 publications

(13 citation statements)

References 61 publications

(168 reference statements)

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“…To decrease the viscosity of the slags, F ions act as a diluent. On the contrary, Kim et al, 22,23) Park et al, 25,30) and Deng et al 20) reported that F ions coordinate to Si ions, thus decreasing the polymerization of the slags by breaking silicate network. Kalisz 49) pointed out that the different behaviors of F ions may be due to the different chemical compositions of the slags under consideration, mainly the basicity of the slags and the presence of other structure modifiers.…”

Section: Discussionmentioning

confidence: 99%

“…Such a phenomenon is consistent with previous studies. [16][17][18][19][20][21][22][23][24][25][26] Physical properties of slags including viscosity intrinsically depend on ionic structure of molten slags. Therefore, to clarify the mechanism of fluorine (F) ions in decreasing slag viscosity, various spectroscopic instruments, such as nuclear magnetic resonance (NMR) spectroscopy, 42) Raman spectroscopy, 25,30) X-ray photoelectron spectroscopy (XPS) 22,43) and Fourier transform infrared (FTIR) spectroscopy, 44,45) as well as molecular dynamics simulation method [45][46][47] have been used to explore the effect of F ions on the structural changes of molten slags.…”

Section: Discussionmentioning

confidence: 99%

“…Similar results were also obtained for low basicity mold fluxes by other researchers. [22][23][24] Park et al 25) revealed that CaF 2 addition effectively decreases the viscosity of CaO-SiO 2 -10%/40%MnO slags, especially when the MnO content is low. A similar conclusion by Kim et al 26) was also obtained for BaO-SiO 2 -MnO-MgO slags containing different MnO contents.…”

Section: Introductionmentioning

confidence: 99%

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Effect of CaF2 on Viscosity and Refining Ability of Highly Basic Slags for Duplex Stainless Steel

Zheng

Wang

et al. 2021

ISIJ Int.

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To optimize CaF 2 content in highly basic CaO-18%Al 2 O 3-SiO 2-10%MgO-CaF 2 (%CaO/%SiO 2 = 6, denoted as C/S = 6) refining slags used for the production of Al-killed duplex stainless steel with high cleanliness demand, the effect of CaF 2 content on the viscosity and refining ability of the slags were studied and compared with typical CaF 2-free highly basic CaO-30%Al 2 O 3-SiO 2-10%MgO (C/S = 6) slag. The effect of CaF 2 addition in decreasing slag viscosity becomes less obvious with increasing temperature and CaF 2 content. When CaF 2 content exceeds 10%, slag viscosity only marginally decreases with further increasing CaF 2 content. Both monoxide-CaO and monoxide-MgO phases are precipitated in all the CaF 2-bearing slags. CaF 2 addition slightly increases monoxide-MgO precipitation, but dramatically decreases monoxide-CaO precipitation. Viscosities of the CaF 2-bearing slags were also theoretically calculated and good agreement with the measured values was observed. Moreover, the 6% CaF 2-bearing slag has very close viscosities above 1 833 K but much lower viscosities below 1 833 K, compared with the CaF 2-free highly basic slag. Further evaluation of the 6% CaF 2-bearing slag on steel cleanliness confirms that 6% CaF 2 addition is sufficient for the highly basic CaO-18%Al 2 O 3-SiO 2-10%MgO-CaF 2 (C/S = 6) slag. The mechanism of CaF 2 in decreasing the viscosity of CaF 2-bearing slags was discussed from the viewpoints that CaF 2 behaves as a network breaker and that CaF 2 suppresses the precipitation of solid phases. The first aspect was identified to play a much greater role in decreasing slag viscosity.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effect of CaF2 on Viscosity and Refining Ability of Highly Basic Slags for Duplex Stainless Steel

Zheng

Wang

et al. 2021

ISIJ Int.

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“…(1). [18][19][20] K AT E RT exp a § © Where η, A, E a , R, T are the viscosity (Pa•s), constant, apparent activation energy (kJ/mol), gas constant (8.314 kJ/ mol/K), and the absolute temperature (K). Furthermore, the activation energy for viscous flow is closely related to the viscosity, which is characterized as when particles in melt move from one equilibrium position to another, the energy required to overcome the resistance.…”

Section: Effect Of La 2 O 3 On the Viscosity Properties Of Moldmentioning

confidence: 99%

Effect of La2O3 on the Viscosity, Crystallization, and Structure of Calcium-silicate-based Mold Flux for Continuous Casting La-bearing FeCrAl Alloy

Fan

Liu

et al. 2021

ISIJ Int.

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The influence of La 2 O 3 on the properties and structure of calcium-silicate-based mold flux for continuous casting La-bearing FeCrAl alloy was studied through employing rotating viscometer, SEM-EDS, XRD, and Raman spectroscopy. The results showed that the viscosity of mold fluxes decreased with the increase of La 2 O 3 content from 0 mass% to 15 mass%. The apparent activation energy for viscous flow decreased from 108.56 ± 1.96 kJ/mol to 87.29 ± 7.29 kJ/mol with increasing La 2 O 3 . Deconvolution Raman analysis showed that with increasing La 2 O 3 , the mole fraction of Q 3 units decreased, while that of Q 0 , Q 1 , and Q 2 units increased. Furthermore, the values of NBO/Si increased from 1.27 to 1.83 with the increase of La 2 O 3 , which indicated that the degree of polymerization of melt structure was reduced and lead to the decrease of viscosity. During the cooling process, cuspidine (Ca 4 F 2 Si 2 O 7 ) was the main crystalline phase in calciumsilicate-based mold fluxes. Nevertheless, when La 2 O 3 was excessively added, a new phase of CaLa 2 (SiO 4 ) 2 was formed owing to the charge balance of Ca 2 + and La 3 + on the simple structural units Q 0 ([SiO 4 ] 4 − ). Therefore, with increasing La 2 O 3 can increase the break temperature and accelerate the formation of crystalline phases Ca 4 F 2 Si 2 O 7 and CaLa 2 (SiO 4 ) 2 at high temperature.

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“…It can be seen that, with the content of B 2 O 3 increasing, the break temperature decreased significantly. The addition of B 2 O 3 can inhibit crystallization, and it would also combine with other oxides in the slag to form low-melting-point eutectics, leading to a reduction in break temperature [20,24]. Figure 11 shows the viscosity-temperature curves of the B2O3-containing slag system.…”

Section: Effects Of B 2 O 3 On Break Temperature and Apparent Activatmentioning

confidence: 99%

Effects of B2O3 on Melting Characteristics and Temperature-Dependent Viscosity of High-Basicity CaO–SiO2–FeOx–MgO Slag

et al. 2020

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In order to reduce the amount of fluorite during the steelmaking process for environmental protection, it is essential to investigate the fluorine-free slag system. Thus, high-basicity CaO–SiO2–FeOx–MgO slag with B2O3 content from 0% to 15% was designed, and its melting characteristics and viscosity were investigated. The influence of B2O3 content on the phase diagram of the slag system was calculated using FactSage 7.3, and the break temperature was determined from the curves of temperature-dependent viscosity. The results show that, with the increase in B2O3 content, the melting characteristics of the CaO–SiO2–FeOx–MgO/B2O3 slag system, including liquidus temperature, flow temperature, softening temperature, and hemispheric temperature, all decreased; the main phase of the slag system transformed from Ca2SiO4 into borosilicate, and finally into borate; the viscous flow activation energy reduced from 690 kJ to 130 kJ; the break temperature reduced from 1590 °C to 1160 °C. Furthermore, the melting characteristics and the break temperature of the slag system with 5% and 8% B2O3 content were found to be the closest to the values of fluorine-containing steel slag.

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Effect of CaF₂, B₂O₃ and the CaO/SiO₂ mass ratio on the viscosity and structure of B₂O₃‐containing calcium‐silicate‐based melts

Cited by 47 publications

References 61 publications

Effect of CaF<sub>2</sub> on Viscosity and Refining Ability of Highly Basic Slags for Duplex Stainless Steel

Effect of CaF<sub>2</sub> on Viscosity and Refining Ability of Highly Basic Slags for Duplex Stainless Steel

Effect of La<sub>2</sub>O<sub>3</sub> on the Viscosity, Crystallization, and Structure of Calcium-silicate-based Mold Flux for Continuous Casting La-bearing FeCrAl Alloy

Effects of B2O3 on Melting Characteristics and Temperature-Dependent Viscosity of High-Basicity CaO–SiO2–FeOx–MgO Slag

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