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Controlled Solidification of Liquids Within the SFC Primary Phase Field of the “Fe2O3”-CaO-SiO2 System in Air
Metallurgical and Materials Transactions B ( IF 3 ) Pub Date : 2019-09-18 , DOI: 10.1007/s11663-019-01689-8
S. Nicol , E. Jak , P. C. Hayes

To provide fundamental information on the phases and microstructures formed during sintering, a liquid with a bulk composition within the silico ferrite of calcium (SFC) primary phase field in the ternary “Fe2O3”-CaO-SiO2 system in air was solidified at a controlled rate. Samples of a bulk composition with a CaO/SiO2 ratio of 4.00 and 69.24 wt pct Fe2O3, were cooled from 1623 K (1350 °C) at 2 K/s, with samples quenched at temperatures between 1513 K (1240 °C) to 1453 K (1180 °C). The silico ferrite of calcium and aluminium I (SFCA-I) and Ca7.2Fe0.82+Fe303+O53 phases were observed to form an intergrowth (‘SFC-I’) rather than the anticipated SFC phase. Solidification was found to occur in three stages, Liquid + ‘SFC-I’, Liquid + ‘SFC-I’ + C2S + CF2, and C2S + CF2 + CF, where C2S denotes dicalcium silicate, CF denotes calcium ferrite and CF2 denotes calcium diferrite. The phases formed and the solidification sequence differ from those predicted under equilibrium and Scheil–Gulliver Cooling. Although not directly applicable to industrial operations, this research clearly shows that the formation of both the SFCA and SFCA-I phase in iron ore sinters is controlled by kinetic processes rather than equilibrium conditions.

中文翻译:

空气中“Fe2O3”-CaO-SiO2 体系 SFC 主相场内液体的受控凝固

为了提供有关烧结过程中形成的相和微观结构的基本信息,在空气中的三元“Fe2O3”-CaO-SiO2 系统中的硅铁氧体钙 (SFC) 主相场中以受控速率固化具有整体成分的液体. CaO/SiO2 比例为 4.00 和 69.24 wt pct Fe2O3 的整体成分样品以 2 K/s 从 1623 K (1350 °C) 冷却,样品在 1513 K (1240 °C) 至 1453 之间的温度下淬火K (1180 °C)。观察到钙铝硅铁氧体 I (SFCA-I) 和 Ca7.2Fe0.82+Fe303+O53 相形成共生 ('SFC-I'),而不是预期的 SFC 相。发现固化发生在三个阶段,液体 + 'SFC-I'、液体 + 'SFC-I' + C2S + CF2 和 C2S + CF2 + CF,其中 C2S 表示硅酸二钙,CF表示铁酸钙,CF2表示二铁酸钙。形成的相和凝固顺序与在平衡和 Scheil-Gulliver 冷却下预测的不同。尽管不能直接应用于工业操作,但这项研究清楚地表明,铁矿石烧结体中 SFCA 和 SFCA-I 相的形成是受动力学过程而不是平衡条件控制的。
更新日期:2019-09-18
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