FeMn Metal Droplet Behavior in the MnO-SiO 2 -CaO Slag System
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RECENT developments in shale plays and sand oils beyond the traditional natural gas beds have given rise to the consumption of corrosion resistant structural materials. However, due to the costs of raw materials including nickel and chromium, there has been expanded uses of high Mn-containing steels to substitute the more expensive austenitic and ferritic stainless steel products, while maintaining the chemical and physical properties of the structural materials under sour environment service.[1–4] In addition to the application in corrosive environments, these new grades of steels have high impact resistance and toughness at very low temperatures, which makes it suitable for cryogenic applications and containers for LNG (liquefied natural gas) at temperatures of less than 110 K (–163 °C).[5–8] By substituting the stainless steel with these high Mncontaining steels, cost savings of more than 50 pct can be realized. In order to develop and produce high-Mn steels in the existing steel manufacturing process, the quantity of FeMn alloy input into the steelmaking furnace is 10 to 15 times higher as compared with any other raw materials input. Thus, the quality and existing impurities of the FeMn alloy can directly impact the quality of the final product, making the control of FeMn alloy input a core process variable. In particular, the main impurity existing in the FeMn alloy is carbon, thus making high quality medium carbon (MC) FeMn alloys to be in great HYOUNG-SOON JANG, Graduate Student, and IL SOHN, Associate Professor, are with Materials Science and Engineering, Yonsei University, Seoul 120-749, Korea. Contact e-mail: ilsohn@ yonsei.ac.kr JAE WOOK RYU, Research Fellow, is with the Korea Metal Material Research Association, Seoul 138-950, Korea. Manuscript submitted July 31, 2014. METALLURGICAL AND MATERIALS TRANSACTIONS B
demand. However, there have been only limited publications in the field of FeMn alloy and refining-related research.[9–11] Rick et al.[9] discussed the process parameters to lower the carbon content during oxygen blowing in the refining process of the high carbon FeMn alloy. If a low CO gas partial pressure and high MnO activity in the slag-promoted decarburization is maintained, then the Mn volatilization would be an issue for yield issues during blowing. Kwang et al.[10] described the production of ultra-low carbon and phosphorous Mn metal by reduction of the FeMn slag with SiMn. Using a refractory impeller, silico-thermic reaction was accelerated and showed possible alternatives to the costly Mn electrolysis production process. Basson et al.[11] summarized the efforts of improving on the classic submerged arc furnace (SAF) process to produce high carbon (HC) FeMn by direct current (DC) open arc furnaces and the COREX process, but found excessive Mn vaporization to limit the implementation of these new technologies in commercial plants. In the current refining process of MC FeMn alloy production, MnO-SiO2-CaO-based slags are generated during the decarburization refining process. However, signific
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