Silico-ferrite of calcium and aluminum (SFCA) is the major bonding phase in iron ore sintering process and is critical to enhancing the sinter properties, such as reducibility and mechanical strength in subsequent blast furnace operations. The phase relations foundations of the alumina-free silico-ferrite of calcium (SFC) have been previously experimentally investigated in air by the authors (Chen et al. ISIJ Int 59:795–804, 2019, Cheng et al. Metall Mater Trans B 51:1587–1602, 2020) and in 1 atm CO 2 (Chen et al. ISIJ Int, 59:805–809, 2019). Present investigation using equilibration and quenching followed by electron probe X-ray microanalysis (EPMA) technique, follows those previous works on the SFC, with the focus on the effects of: (i) Al 2 O 3 (in the “Fe 2 O 3 ”-CaO-Al 2 O 3 and the “Fe 2 O 3 ”-CaO-SiO 2 -Al 2 O 3 system in air), and (ii) the effect of $$ p_{{{\text{O}}_{2} }} $$ p O 2 (the “Fe 2 O 3 ”-CaO-Al 2 O 3 in 1 atm CO 2 atmosphere), to investigate the thermodynamic stability of the C(A, F) 3 [Ca(Al, Fe) 6 O 10 ] solid solution in the “Fe 2 O 3 ”-CaO-Al 2 O 3 system in both air and pure CO 2 atmospheres between 1150 °C and 1250 °C; and the silico-ferrite of calcium and aluminum (SFCA) solid solution with 1, 2 and 4 wt pct of Al 2 O 3 in bulk compositions in the “Fe 2 O 3 ”-CaO-SiO 2 -Al 2 O 3 system at temperatures in the range between 1255 °C and 1340 °C. Present study shows that C(A, F) 3 is stable over a wide range of Al 2 O 3 concentration (8.8 to 26.7 wt pct Al 2 O 3 , or 12.5 to 34.8 mol pct AlO 1.5 ). It also becomes less stable in terms of both the temperature and the compositional stability range as the oxygen partial pressure is reduced. The SFCA phase in the “Fe 2 O 3 ”-CaO-SiO 2 -Al 2 O 3 system is found to be present in the range of 1 to 4 wt pct Al 2 O 3 bulk compositions selected in air. The relative stability of this phase increases with increased Al 2 O 3 in the bulk material. Tie-lines joining the SFCA and the corresponding liquid and hematite phases are constructed over the range of composition investigated at sub-liquidus temperatures. The new experimental measurements show that the CaO/SiO 2 ratio in the SFCA phase is almost identical to that in the liquid. The distribution ratio of Al 2 O 3 between SFCA and liquid is in the range 2/1 to 3/1.

中文翻译：

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FeO-Fe2O3-CaO-Al2O3体系中C(A, F)3固溶体和FeO-Fe2O3-CaO-SiO2-Al2O3体系中SFCA相的热力学稳定性研究

钙铝硅铁酸盐 (SFCA) 是铁矿石烧结过程中的主要结合相，对于提高烧结性能至关重要，例如在随后的高炉操作中可还原性和机械强度。作者先前已在空气中对无铝硅铁酸钙 (SFC) 的相关系基础进行了实验研究（Chen 等人。ISIJ Int 59:795–804, 2019，Cheng 等人。Metall Mater Trans B 51:1587–1602, 2020) 和 1 atm CO 2 (Chen et al. ISIJ Int, 59:805–809, 2019)。本研究使用平衡和淬火，然后是电子探针 X 射线微量分析 (EPMA) 技术，遵循先前关于 SFC 的工作，重点是：(i) Al 2 O 3（在“Fe 2 O 3 ”-CaO-Al 2 O 3 和“Fe 2 O 3 ”-CaO-SiO 2 -Al 2 O 3 体系在空气中），(ii) $$ p_{{{\text{O}}}_{2} }} $$ p O 2 （“Fe 2 O 3 ”-CaO-Al 2 O 3 在 1 atm CO 2大气），研究 C(A, F) 3 [Ca(Al, Fe) 6 O 10 ] 固溶体在“Fe 2 O 3 ”-CaO-Al 2 O 3 体系中的热力学稳定性，在空气和1150 °C 至 1250 °C 之间的纯 CO 2 气氛；以及在“Fe 2 O 3 ”-CaO-SiO 2 -Al 2 O 3 系统中具有1、2和4wt%的Al 2 O 3 的钙和铝（SFCA）固溶体的硅铁酸盐固溶体，在“Fe 2 O 3 ”-CaO-SiO 2 -Al 2 O 3 系统中温度范围在 1255 °C 和 1340 °C 之间。目前的研究表明，C(A, F) 3 在很宽的 Al 2 O 3 浓度范围内（8.8 至 26.7 wt pct Al 2 O 3 ，或 12.5 至 34.8 mol pct AlO 1.5 ）是稳定的。随着氧分压的降低，它在温度和组成稳定性范围方面也变得不太稳定。发现“Fe 2 O 3 ”-CaO-SiO 2 -Al 2 O 3 体系中的SFCA相以1至4wt%的Al 2 O 3 本体组成的范围存在于空气中。该相的相对稳定性随着散装材料中Al 2 O 3 的增加而增加。连接 SFCA 和相应的液相和赤铁矿相的连接线是在亚液相线温度下研究的成分范围内构建的。新的实验测量表明，SFCA 相中的 CaO/SiO 2 比率几乎与液体中的相同。Al 2 O 3 在SFCA和液体之间的分配比在2/1至3/1的范围内。该相的相对稳定性随着散装材料中Al 2 O 3 的增加而增加。连接 SFCA 和相应的液相和赤铁矿相的连接线是在亚液相线温度下研究的成分范围内构建的。新的实验测量表明，SFCA 相中的 CaO/SiO 2 比率几乎与液体中的相同。Al 2 O 3 在SFCA和液体之间的分配比在2/1至3/1的范围内。该相的相对稳定性随着散装材料中Al 2 O 3 的增加而增加。连接 SFCA 和相应的液相和赤铁矿相的连接线是在亚液相线温度下研究的成分范围内构建的。新的实验测量表明，SFCA 相中的 CaO/SiO 2 比率几乎与液体中的相同。Al 2 O 3 在SFCA和液体之间的分配比在2/1至3/1的范围内。