Numerical Simulation of Solidification Structure of ESR Ingot Using Cellular Automaton Method
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THE electroslag remelting (ESR) process is a remelting process with a consumable electrode for producing ingots of high quality than that of the original material by means of controlled solidification and chemical refining. Figure 1 shows the schematic diagram of ESR process. The Joule heating, which is generated by the alternating or direct current pass through the molten slag to the base plate, remelts the consumable electrode, and the droplet or the continuous stream (depending on the melting rate) of molten melt descends through the molten slag into the pool of molten metal. The heat of the molten metal is extracted by the water-cooled copper mold and the base plate, and finally the high quality remelted ingot is gained with a degree of directional solidification. The solidification structure of ESR ingot is of great importance to the final product properties, and thus has attracted many attentions to control the solidification structure of ESR ingot during the ESR process. Therefore, establishment of the relationship between the practical operation parameters and the solidification structure parameters of ESR ingot becomes one of the main concerns during the ESR operations. However, XIAOHUA WANG, PH.D. Candidate, and YING LI, Professor, are with the School of Materials and Metallurgy, Northeastern University, Shenyang 110819, P.R. China. Contact e-mail: liying@ mail.neu.edu.cn Manuscript submitted February 5, 2014. METALLURGICAL AND MATERIALS TRANSACTIONS B
owing to the high costs associated with the currently produced large ingot, it is hard to comprehensively assess the influence of the practical operation on the final solidification structure of ESR ingot by trial and error method in industrial trials. Consequently, numerical model, as an alternative method, is gradually adopted to quantitatively investigate the complex physical and chemical phenomena occurred in ESR process. The microstructure of the ingot is controlled by the local solidification time which is, in turn, dependent on the local profile and the extent of the mushy zone. Therefore, in the past few decades, investigations on the temperature field, flow field, and electromagnetic field of ESR process are widely carried out using the numerical simulation in order to elucidate the dominant transport mechanisms and characterize the solidification process using the local solidification time and liquid pool shape. Hernandez-Morales and Mitchell[1] had given a comprehensive review of the mathematical models of ESR in 1999 and pointed out that more efforts were required before the models can be applied to define actual operating conditions. Later, improvements on the mathematical model were performed. Kelkar et al.[2] proposed a comprehensive computational model of the ESR process considering the electromagnetic, flow, heat transfer, and phase change phenomena in a coupled manner. Weber et al.[3] also developed a comprehensive model of the ESR process and analyzed the influence of the electrode fill ratio on the distribution of the Joule heating and the electromagnetic force,
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