Influence of Oxygen on Cu Distribution Behavior Between Molten Iron and FeS-Based Flux
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ronmental virtue of steelmaking using an electric arc furnace (EAF) and scrap steel has been highlighted, as compared to the conventional production route of using a blast furnace which produces a huge amount of CO2. However, there are several issues to be carefully addressed to develop a successful steelmaking process using an EAF. The problem concerning tramp elements can be very serious, as they easily dissolve into molten iron and are difficult to remove using ordinary refining processes. The contents of the tramp elements in steel scrap are therefore likely to be concentrated[1,2] during the repeated recycling of the steel scrap. Among them, copper is regarded as the most important tramp element, because red hot-shortness can be caused when it is enriched at the surface of a slab.[3] In order to meet the rapidly growing demands for scrap steel, appropriate control of the copper content in steel scrap is necessary. Since copper cannot be removed sufficiently by oxidation, several different approaches have been made, such as evaporation by plasma irradiation[4–6] or
YOUNGJO KANG is with the Department of Materials Science and Engineering, Dong-A University, Busan, 48315, Korea. Contact e-mail: [email protected] KIL-SUN SHIN is with the Institute of Industrial Science, The University of Tokyo, Tokyo, 153-8505, Japan. KAZUKI MORITA is with the Department of Materials Science and Engineering, School of Engineering, The University of Tokyo, Tokyo, 113-8654, Japan. Manuscript submitted July 31, 2017. METALLURGICAL AND MATERIALS TRANSACTIONS B
cryogenic processes.[7,8] Due to economical limitations, these techniques for the removal of copper have not been established on a commercial scale. On the other hand, several researchers have realized that the greater affinity of copper for sulfur than that of iron may enable the removal of copper from iron using sulfide fluxes. A pioneering study on Cu removal using a sodium sulfide flux was carried out by Langenberg et al. about 60 years ago.[9] In the late 1980s, Imai et al. measured the Cu partition ratio between Na2S-FeS flux and carbon-saturated iron and the influences of temperature and composition on Cu partition behavior were also investigated.[10] A few years later, there were more detailed researches on Cu removal from molten iron using sulfide flux, in which the phase equilibria in the Fe-C-S system and the effects of different kinds of sulfide flux, e.g., alkaline and alkaline earth metal sulfides were studied.[11–13] As another example of different flux additives, the applicability of aluminum sulfide to the decopperization flux was experimentally investigated by several researchers.[14,15] According to their results, the Cu removal efficiency of Al2S3-FeS-based flux could be enhanced under the condition of a high activity coefficient of FeS. Contrary to the sulfide based flux, which has difficulties with practical operation, different types of flux have been considered for use in decopperization. The decopperization behaviors of various sulfate fluxes have been experimentally compared by Matsuo et
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