This study investigates the effect of B2O3 content and CaO/Al2O3 ratio on the melting temperature, viscosity, and electrical conductivity of CaF2–CaO–Al2O3–MgO slag systems for electroslag remelting of boron-containing reduced activation ferritic/martensitic (RAFM) steel. The physicochemical properties were characterized using a slag melting point analyzer, a high-temperature melt property tester, and an electrical conductivity meter. The underlying mechanisms were elucidated through X-ray diffraction (XRD), confocal laser Raman microscope, and thermodynamic calculations using FactSage 8.2. The results demonstrate that increasing B2O3 content leads to a progressive decrease in the high-melting-point phase Ca12Al14O32F2 while increasing the low-melting-point phase CaF2. The low-melting-point region in the isothermal section diagram expands significantly and shifts upward, resulting in a reduction in the melting temperature of the slag. When the CaO/Al2O3 ratio increases from 0.8 to 1.1, the content of low-melting-point phase Ca12Al14O33 increases, decreasing the melting temperature from 1346 °C to 1310 °C. With the increase of B2O3 content and CaO/Al2O3 ratio, the viscous flow activation energy of the slag gradually decreases. The aluminate structure in the slag becomes depolymerized, leading to an increase in the number of non-bridging oxygen atoms. The highly polymerized <InlineEquation ID="IEq1"> <EquationSource Format="TEX">$Q_{{{\text{Al}}}}^{3}$</EquationSource> <EquationSource Format="MATHML"><math> <msubsup> <mi>Q</mi> <mrow> <mtext>Al</mtext> </mrow> <mn>3</mn> </msubsup> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq2"> <EquationSource Format="TEX">$Q_{{{\text{Al}}}}^{4}$</EquationSource> <EquationSource Format="MATHML"><math> <msubsup> <mi>Q</mi> <mrow> <mtext>Al</mtext> </mrow> <mn>4</mn> </msubsup> </math></EquationSource> </InlineEquation> structural units are transformed into less polymerized structural units such as <InlineEquation ID="IEq3"> <EquationSource Format="TEX">$Q_{{{\text{Al}}}}^{0}$</EquationSource> <EquationSource Format="MATHML"><math> <msubsup> <mi>Q</mi> <mrow> <mtext>Al</mtext> </mrow> <mn>0</mn> </msubsup> </math></EquationSource> </InlineEquation>, <InlineEquation ID="IEq4"> <EquationSource Format="TEX">$Q_{{{\text{Al}}}}^{1}$</EquationSource> <EquationSource Format="MATHML"><math> <msubsup> <mi>Q</mi> <mrow> <mtext>Al</mtext> </mrow> <mn>1</mn> </msubsup> </math></EquationSource> </InlineEquation>, and <InlineEquation ID="IEq5"> <EquationSource Format="TEX">$Q_{{{\text{Al}}}}^{2}$</EquationSource> <EquationSource Format="MATHML"><math> <msubsup> <mi>Q</mi> <mrow> <mtext>Al</mtext> </mrow> <mn>2</mn> </msubsup> </math></EquationSource> </InlineEquation>. The overall degree of polymerization of the slag is reduced, and the viscosity decreases. The electrical conductivity increases with temperature from 1430 °C to 1520 °C. With increasing B2O3 content, the activation energy for electrical conduction decreases, reaching a minimum of 36.34 kJ mol−1 at 8 wt pct B2O3, where maximum conductivity is observed. The electrical conductivity increases first and then decreases with the increase of CaO/Al2O3 ratio. When CaO/Al2O3 is 0.9, the lowest activation energy of slag conductivity is 52.13 kJ mol−1, and the conductivity is the highest. The variation in activation energy fundamentally governs the changes in electrical conductivity.

Effect of B₂O₃ and CaO/Al₂O₃ on the Melting Properties, Viscosity, and Electrical Conductivity of ESR Slag for Reduced Activation Ferritic/Martensitic Steel with Boron

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发表日期：

2025年10月6日

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Guo-Xing Qiu,
Guang-Hui Jie,
Hong-Zhao Zhang,
Lei Cao,
Chao Chen,
Yong-Kun Yang,
Xiao-Ming Li

摘要

This study investigates the effect of B₂O₃ content and CaO/Al₂O₃ ratio on the melting temperature, viscosity, and electrical conductivity of CaF₂–CaO–Al₂O₃–MgO slag systems for electroslag remelting of boron-containing reduced activation ferritic/martensitic (RAFM) steel. The physicochemical properties were characterized using a slag melting point analyzer, a high-temperature melt property tester, and an electrical conductivity meter. The underlying mechanisms were elucidated through X-ray diffraction (XRD), confocal laser Raman microscope, and thermodynamic calculations using FactSage 8.2. The results demonstrate that increasing B₂O₃ content leads to a progressive decrease in the high-melting-point phase Ca₁₂Al₁₄O₃₂F₂ while increasing the low-melting-point phase CaF₂. The low-melting-point region in the isothermal section diagram expands significantly and shifts upward, resulting in a reduction in the melting temperature of the slag. When the CaO/Al₂O₃ ratio increases from 0.8 to 1.1, the content of low-melting-point phase Ca₁₂Al₁₄O₃₃ increases, decreasing the melting temperature from 1346 °C to 1310 °C. With the increase of B₂O₃ content and CaO/Al₂O₃ ratio, the viscous flow activation energy of the slag gradually decreases. The aluminate structure in the slag becomes depolymerized, leading to an increase in the number of non-bridging oxygen atoms. The highly polymerized $Q_{{{\text{Al}}}}^{3}$ $Q_{Al}^{3}$ and $Q_{{{\text{Al}}}}^{4}$ $Q_{Al}^{4}$ structural units are transformed into less polymerized structural units such as $Q_{{{\text{Al}}}}^{0}$ $Q_{Al}^{0}$ , $Q_{{{\text{Al}}}}^{1}$ $Q_{Al}^{1}$ , and $Q_{{{\text{Al}}}}^{2}$ $Q_{Al}^{2}$ . The overall degree of polymerization of the slag is reduced, and the viscosity decreases. The electrical conductivity increases with temperature from 1430 °C to 1520 °C. With increasing B₂O₃ content, the activation energy for electrical conduction decreases, reaching a minimum of 36.34 kJ mol⁻¹ at 8 wt pct B₂O₃, where maximum conductivity is observed. The electrical conductivity increases first and then decreases with the increase of CaO/Al₂O₃ ratio. When CaO/Al₂O₃ is 0.9, the lowest activation energy of slag conductivity is 52.13 kJ mol⁻¹, and the conductivity is the highest. The variation in activation energy fundamentally governs the changes in electrical conductivity.

Effect of B2O3 and CaO/Al2O3 on the Melting Properties, Viscosity, and Electrical Conductivity of ESR Slag for Reduced Activation Ferritic/Martensitic Steel with Boron

摘要

Effect of B₂O₃ and CaO/Al₂O₃ on the Melting Properties, Viscosity, and Electrical Conductivity of ESR Slag for Reduced Activation Ferritic/Martensitic Steel with Boron