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Iron redox equilibria in BOF slag equilibrated with ambient air
Author(s) -
Park Jong Min
Publication year - 2002
Publication title -
steel research
Language(s) - English
Resource type - Journals
eISSN - 1869-344X
pISSN - 0177-4832
DOI - 10.1002/srin.200200171
Subject(s) - slag (welding) , steelmaking , chemistry , oxide , iron oxide , redox , metallurgy , inorganic chemistry , ion , materials science , organic chemistry
The Fe 2+ /Fe 3+ ratio in the CaO‐MgO‐Fe 2 O 3 ‐FeO‐SiO 2 based slag was measured under the condition of equilibrium with the ambient air at 1873 K as a fundamental study for precise slag coating control in BOF operation. The CaO/SiO 2 mass ratios of the main slag were 1, 1.5, 2, 3 and 4, and total iron mass content was in the range of 10 to 35 %. Moreover, mass contents of 1 to 13 % of MnO and 2 to 12 % of Al 2 O 3 were added to the melt to evaluate their effects on the Fe 2+ /Fe 3+ ratio. The effect of slag composition on the Fe 2+ /Fe 3+ ratio was discussed and quantified into a form of formula. As the basicity in slag increases, the Fe 2+ /Fe 3+ ratio decreases. The effect of iron oxide mass content is observed to be dependent on the basicity of slag. An increase in iron oxide mass content makes the Fe 2+ /Fe 3+ ratio higher for basic slag but lower for acidic slag. It is revealed that the redox reaction of iron oxide in steelmaking slag under the ambient air is controlled by the complex anion formation reaction of iron oxide, and that the iron oxide in basic slag exists in the form of 2 or more kinds of complex anion controlling the oxygen anion content. Both Al 2 O 3 and P 2 O 5 increase the Fe 2+ /Fe 3+ ratio by diluting the basic oxides as SiO 2 does, while manganese oxide lowers the Fe 2+ /Fe 3+ ratio enormously down to nearly zero. The Fe 2+ /Fe 3+ ratio can be described as a function of slag composition, X = (%CaO) + 0.38(%Fe 2 O 3 + %FeO)+3.2(%MnO), in the equation of log(Fe 2+ /Fe 3+ ) = ‐0.00107 X 2 + 0.0721 X ‐ 1.982.