Activities of FeO_(1.33) in the FeO_x-CaO-SiO_2 and FeO_x-CaO-SiO_2-Al_2O_3 Slags at 1 573 K Under Oxygen Partial Pressures between 10~(-6) and 10~(-2) atm

摘要

Qualities of sinters such as reducibility and strength are controlled by morphologies and mineral phases in iron ore sinters. Main mineral phases are hematite, magnetite and calcium ferrite. Slag phases are also included in sinters, which have been mainly liquid phases during the sintering process. Since iron ions in slags are hardly reduced to metallic irons in a blast furnace, iron oxides such as hematite and magnetite and calcium ferrite should be precipitated from molten slags during the sintering process. Precipitation of iron oxides and calcium ferrites from molten slags depends on the activity of FeO_x in molten slags from the thermodynamic view point. Therefore, the activities of FeO_(1.33) have been measured over the wide ranges of chemical compositions in the single liquid phases of the FeO_x-CaO-SiO_2 and FeO_x-CaO-SiO_2-Al_2O_3 slags at 1 573 K under oxygen partial pressures between 10~(-6) and 10~(-2) atm. It has been found that the a_(FeO1.33) values have maximum at the CaO/SiO_2(mass%) ratios of 0.9-1.0 and 1.3-1.4 for the samples with 35 mass%FeO_x equilibrated at P_(O2) = 1.0×10~(-2) atm and 1.0×10~(-4) atm, respectively. For the samples at P_(O2) = 2.5×10~(-6) atm, on the other hand, a_(FeO1.33) monotonically increases with increasing the CaO/SiO_2 ratio within the compositional range of the single liquid region. As for the effect of the Al_2O_3 addition on the activities, the dependency of the activity on the CaO/SiO_2 ratio becomes moderate with increasing the Al_2O_3 addition on the sample at P_(O2) = 2.5×10~(-6) atm.