Validation of a Multiphase Model for the Macrosegregation and Primary Structure of High-Grade Steel Ingots
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FOR the as-cast ingots of high grade steels, many rejection criteria are defined, which are critical for the downstream production chains such as rolling or forging. The most important criteria for the as-cast ingots are the macrosegregation of the major alloying elements, e.g., carbon and chromium, and the inhomogeneous distribution of the primary structure (the columnar zone, the equiaxed zone, and the columnar-to-equiaxed transition). However, both macrosegregation and primary structure are strongly related to the process parameters such as the pouring temperature, the casting rate, the mold design, or the use of insulation or exothermic powder. In order to understand the impact of these process parameters on ingot quality, it is necessary to perform numerous casting trials, which are time consuming and costly. An alternative approach to optimize the process parameters is the use of multiphase and multicomponent modeling. Therefore, Bo¨hler Edelstahl GmbH & Co KG (BEG), a renowned producer of tool steels and special materials, and the CD Laboratory for Multiphase Simulation of Metallurgical Processes (CDL), University of Leoben, started a R. TANZER, Researcher, W. SCHU¨TZENHO¨FER, Head of R&D Department, G. REITER, Production Assistant, Special Steel Plant, and H.-P. FAULAND, Head of Steel Plants, are with Bo¨hler Edelstahl GmbH & Co KG (BEG), Kapfenberg, Austria. Contact e-mail: [email protected] L. KO¨NO¨ZSY, A. ISHMURZIN, and M. WU, Researchers, and A. LUDWIG, Head, are with the Christian-Doppler Laboratory for Multiphase Modeling of Metallurgical Processes, Department of Metallurgy, University of Leoben (MUL), Leoben, Austria. 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 December 16, 2008. METALLURGICAL AND MATERIALS TRANSACTIONS B
cooperation. The numerical models are developed at the CDL, whereas BEG produces ingots of different sizes to validate the model. The outcome of the cooperation will be a model to simulate the formation of macrosegregation and the evolution of primary structure in the as-cast state of ingots. This article presents the preliminary results of applying the multiphase model for simulating solidification of a ternary steel (Fe-C-Cr) and compares the computed data with the laboratory scale casting experiment data. Great efforts were made in the understanding of solidification and the formation of macrosegregation in steel.[1,2] On this basis, a number of articles have been published dealing with the prediction of macrosegregation of steel castings using numerical simulation.[3–5] Gu and Beckermann[6] used a model for solidification of a multicomponent steel with numerical solution of fully coupled mass, momentum, energy, and species conservation equations for the liquid and solid regions as well as the mushy zone. The model was applied to describe the macrosegregation and the flow pattern caused by thermal and solu
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