Influence of Electropulsing Treatment on the Initial Solidification of Molten Steel During Continuous Casting
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been widely acknowledged that the initial solidification behavior of molten steel in the mold is the origin of shell growth and determines the internal[1,2] and surface quality[3–5] of the final slab. However, it is difficult to obtain a clear comprehensive understanding of the initial solidification of steel around the meniscus due to the nature of transient, intensive fluid flow and the high-temperature harsh environment. The related studies are mainly focused on numerical simulation and physical modeling of in-mold initial solidification phenomena during continuous casting. A number of numeric models, for instance, a heat-transfer model by Takeuchi and Brimacombe,[6] a thermal-mechanical model by Schwerdtfeger and Sha,[7] and a multiphase
GUOMIN YING, WANLIN WANG, HAIHUI ZHANG, and JIE ZENG are with the School of Metallurgy and Environment, Central South University, Changsha, 410083, China and also with the National Center for International Research of Clean Metallurgy, Central South University, Changsha, 410083 China. Contact e-mail: [email protected] Manuscript submitted November 19, 2018. Article published online May 11, 2019. 1608—VOLUME 50B, AUGUST 2019
model by Ramirez-Lopez et al.[8] were developed to study the initial solidification phenomena of liquid steel. However, the aforementioned numeric models lack precise boundary conditions and sometimes are not able to capture the exact scenario that occurred during the initial solidification in the mold. Therefore, different physical techniques, such as dip tests, static molds, dip simulators,[9–12] small-scale casters,[13,14] and mold simulators,[15–20] were developed to simulate the steel solidification behavior during continuous casting, with simulator tools, such as the complex inter-relationship between casting parameters, high-frequency heat flux variation, in-mold temperatures’ distribution, shell surface profile, and mold flux crystallization, being well discussed. However, the effect of electropulsing treatment (EPT) on the initial solidification phenomena of steel during continuous casting has not been studied. The EPT has become a novel green solidification control technology in materials processing due to its simplicity and efficiency. Research suggests that the nucleation rate of molten metal was improved and the solidification microstructure could be refined when the pulsed electric current was applied to molten alloys directly through electrodes.[21–24] Intensive studies confirmed the grain refining effect of EPT on the METALLURGICAL AND MATERIALS TRANSACTIONS B
solidification of pure metals,[25] eutectic alloys,[26–28] and solid solution alloys[29] in the past decades. The proposed mechanisms for the EPT-induced grain refine-
Fig. 1—Schematic of (a) the electropulsing-assisted mold simulator apparatus and (b) the location of thermocouples.
ment can be summarized as the nucleation rate being promoted owing to the raised undercooling,[30,31] the accelerated particle motion,[32,33] and the dendrite fragmentation mechanism.[34] Also, the EPT-induced grain refinement
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