Effect of Current Frequency on Droplet Evolution During Magnetic-Field-Controlled Electroslag Remelting Process Via Visu
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ADAYS, the electroslag remelting (ESR) process is one of the most important methods to refine the metallic materials for its achievement of high-efficiency purification and fine ingots. The steel ingots refined by the ESR process are used in many areas, such as aviation, electricity, transportation, metallurgy machinery field, and so on.[1–6] To meet the higher demands for clean steel of high quality, sometimes the ESR process becomes an essential technology. It is clear that the nonmetallic inclusions can be removed through the interface between metal and slag. There are three stages to remove the inclusions during ESR process: (1) formation of droplets at the electrode tip; (2) droplets falling through the slag; and (3) collection of the droplets in a pool at the top of the ingot. Some research[7,8] has been done to find out which was the main stage of the refining process. Li et al.[7] took samples from the solid electrode, the molten film on the electrode tip, metal droplets in the slag, and the final ingot. The quantitative determination of inclusions were made by
HUAI WANG and QIANG LI, Doctors, YIPENG FANG, Master, and WEILI REN, ZUOSHENG LEI, ZHONGMING REN, and YUNBO ZHONG, Professors, are with the State Key Laboratory of Advanced Special Steels, Shanghai University, Shanghai 200072, P.R. China. Contact e-mail: yunboz@staff.shu.edu.cn. Manuscript submitted October 10, 2015. METALLURGICAL AND MATERIALS TRANSACTIONS B
metallographic, chemical, and radioisotopic methods. They concluded from the experiments that the cleaning happened most at the electrode tip. So the evolution behavior of the droplets becomes very important because it is one of the key points to influence the former two stages of the ESR process. Based on this dynamic view, if the interface area is larger, the higher removal efficiency of the nonmetallic inclusions will be obtained. The technology called the ‘‘magnetic-field-controlled electroslag remelting (MFC-ESR) process’’ in Figure 1 is considered to be an effective way to enlarge the interface area, leading to the improvement of removal efficiency.[9–11] So MFC-ESR is adopted in this study, and the transverse static magnetic field (TSMF) is chosen as the external magnetic field. Kompan et al.[10,12–14] had investigated the effects of TSMF during MFC-ESR on the overall fluid flow of titanium alloys. They found that it was effective to control the hydrodynamics of the liquid melt (metal and slag) by applying the TSMF. The vibration (50 Hz) of the melt could be generated, which suppressed the rotational movement in the slag pool and contributed to the purification of molten metal. Droplets were not just formed in the central part of the metal pool. The depth and shape of the metal pool could be controlled from a deep V-shape to a shallow U-shape. A fine-grain, homogeneous structure and the high properties of titanium ingots were obtained by using the TSMF during MFC-ESR. Murgasˇ et al.[11] showed that the structure and mechanical properties of the high-speed
steel could be improved by the technology of MFC-ESR. Zhon
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