A Comprehensive Model of the Electroslag Remelting Process: Description and Validation
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ELECTROSLAG remelting (ESR) has been developed to produce high-performance alloys dedicated to critical applications for which high-metallurgical-quality ingots are necessary. Consequently, primary melting is not sufficient; remelting, on the other hand, provides valuable advantages, such as a fine solidification structure, limited occurrence of solidification defects, low levels of micro- and macrosegregation, and sound ingots. Moreover, insulation from air and chemical refining due to the presence of slag improve the inclusional quality.[1,2] An alternating current (AC) flows from a conventional ingot, also called an electrode, to a water-cooled baseplate through a high-resistivity calcium-fluoride-based slag, thus generating Joule heating. The energy is transferred both to the electrode for the melting and to the secondary ingot. Molten metal is produced in the form of droplets that fall in the water-cooled copper mold, building up the final solid ingot, as shown in Figure 1. Therefore, during V. WEBER, formerly Postdoctoral Student, LSG2M, Ecole des Mines de Nancy, Nancy Cedex 54042, France is Research Engineer, ArcelorMittal, Maizie`res-le`s-Metz 57283, France. A. JARDY, CNRS Research Scientist, B. DUSSOUBS, Research Engineer, and D. ABLITZER, Professor, are with the LSG2M, Ecole des Mines de Nancy, France. S. RYBE´RON, Development Technician, and V. SCHMITT, S. HANS, and H. POISSON, Development Engineers, are with Aubert & Duval, Les Ancizes 63770, France. Contact e-mail: [email protected] This article is based on a presentation given at the International Symposium on Liquid Metal Processing and Casting (LMPC 2007), which occurred in September 2007 in Nancy, France. Article published online January 14, 2009. METALLURGICAL AND MATERIALS TRANSACTIONS B
remelting, the secondary ingot is composed of a liquid metal pool, a mushy zone, and a solid part. As noticed previously, additional chemical refining is obtained during the passage of the droplets through the slag. Electroslag-remelted products are high-value-added metallic alloys such as specialty steels or nickel-based superalloys. Consequently, trial-and-error approaches are very expensive and not well suited for systematic studies. Furthermore, the implementation of in-situ experiments is very complicated, due to high-temperature operating conditions. Mathematical modeling is, therefore, a valuable tool for enhancing fundamental understanding, because it allows us to link the operating parameters, such as the melting rate, ingot diameter, and cooling parameters, to local solidification conditions and, thus, to the ingot final quality. For these reasons, a comprehensive model of the ESR process has been developed at the Laboratory of Science and Engineering of Materials and Metallurgy (LSG2M), located in the School of Mines at Nancy, France. The development started in 2004 with a basic hydrodynamic model of the slag. The model was improved step by step, using some former work carried out in Nancy.[3,4] Indeed, the model has several features in common w
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