Evaluation of Thermodynamic Driving Force and Effective Viscosity of Secondary Steelmaking Slags on the Dissolution of Al2O3-Based Inclusions from Liquid Steel,ISIJ International

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Evaluation of Thermodynamic Driving Force and Effective Viscosity of Secondary Steelmaking Slags on the Dissolution of Al2O3-Based Inclusions from Liquid Steel
ISIJ International ( IF 1.8 ) Pub Date : 2021-07-15 , DOI: 10.2355/isijinternational.isijint-2021-037
Pedro Cunha Alves ₁ , Vinicius Cardoso Da Rocha ₁ , Julio Aníbal Morales Pereira ₁ , Wagner Viana Bielefeldt ₁ , Antônio Cezar Faria Vilela ₁

Affiliation

Dissolution of Al₂O₃-based inclusions are paramount during production of special steel and slag engineering is key to enhance this phenomenon. This work evaluates the influence of thermodynamic driving force (ΔC) and effective viscosity (η_e) on steel cleanliness of three distinct steel grades and slag composition (Steel/Slag A, Steel/Slag B and Steel/Slag C). Initial and final steel and slag samples were withdrawal on an electric steelmaking facility. The first samples after addition of aluminum as deoxidizer and the second after vacuum degassing stage. X-ray fluorescence and optical spectrometry obtained initial and final samples chemical composition. An ASPEX Explorer acquired inclusions data and FactSage v.7.2 performed thermodynamic calculations. Analysis of steel Al and O content highlighted an inefficient dissolution of Al₂O₃-based inclusions for Steel/Slag A, deteriorating steel cleanliness. Furthermore, this phenomenon is supported by average inclusions composition on initial and final samples plotted in pseudo-ternary diagram. Steel/Slag B and C provided improved results regarding the dissolution of Al₂O₃-based inclusions with a final inclusion density below 0.50 mm^-2. These two slags composition achieved values of ΔC above 25 and η_e close to 0.10 Pa·s. In addition, their combined effect (ΔC/η_e) presented values above 250 and had the highest linear fit among these analyses. These properties are influenced by slags chemical composition and can be improved controlling parameters as binary basicity and CaO/Al₂O₃ ratio. Slags B and C were selected to define an optimal range for these parameters, with binary basicity between 3.00–3.50 and CaO/Al₂O₃ ratio in a range from 2.50–3.50.

Inclusions average chemical composition on initial and final steel samples as contour lines plotted in CaO–Al₂O₃–SiO₂ and CaO–MgO–Al₂O₃ ternary diagram (a) Steel A; (b) Steel B; (c) Steel C. Fullsize Image

中文翻译：

二次炼钢渣的热动力驱动力和有效粘度对钢液中Al2O3基夹杂物溶解的评价

Al ₂ O ₃基夹杂物的溶解在特殊钢的生产过程中至关重要，炉渣工程是增强这种现象的关键。这项工作评估了热力学驱动力 (ΔC) 和有效粘度 ( η _e) 三种不同钢种和炉渣成分（钢/渣 A、钢/渣 B 和钢/渣 C）的钢清洁度。初始和最终钢和炉渣样品在电炉炼钢设施中取出。添加铝作为脱氧剂后的第一个样品和真空脱气阶段后的第二个样品。X射线荧光和光谱法得到初始和最终样品的化学成分。ASPEX Explorer 获取夹杂物数据，FactSage v.7.2 执行热力学计算。钢中 Al 和 O 含量的分析强调了 Al ₂ O ₃的低效溶解-钢/渣 A 的夹杂物，使钢的清洁度变差。此外，这种现象得到了绘制在伪三元图中的初始和最终样品的平均夹杂物组成的支持。钢/炉渣 B 和 C 提供了关于最终夹杂物密度低于 0.50 mm ^{-2 的}基于Al ₂ O ₃的夹杂物溶解的改进结果。这两种炉渣成分的 ΔC 值高于 25，η _e接近 0.10 Pa·s。此外，它们的综合效应 (ΔC/ η _e) 呈现高于 250 的值，并且在这些分析中具有最高的线性拟合。这些性能受炉渣化学成分的影响，可以通过控制二元碱度和 CaO/Al ₂ O ₃比等参数来改进。选择炉渣 B 和 C 来定义这些参数的最佳范围，二元碱度在 3.00-3.50 之间，CaO/Al ₂ O ₃比在 2.50-3.50 之间。