Numerical Modeling of the Macrosegregation Improvement in Continuous Casting Blooms by Using F-EMS
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https://doi.org/10.1007/s11837-020-04363-6 Ó 2020 The Minerals, Metals & Materials Society
SOLIDIFICATION BEHAVIOR IN THE PRESENCE OF EXTERNAL FIELDS
Numerical Modeling of the Macrosegregation Improvement in Continuous Casting Blooms by Using F-EMS SHAOXIANG LI,1 ZHIQIANG HAN,1,3 and JIAQUAN ZHANG2 1.—School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China. 2.—School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China. 3.—e-mail: [email protected]
A three-dimensional mathematic model based on segmentation that joins the electromagnetic field, melt flow, heat transfer, solidification and solute transport in the whole casting domain has been established to study the solute transport at the final stage of solidification in a bloom continuous casting process. The effects of the final electromagnetic stirring (F-EMS) positions on the macrosegregation degree of the as-cast bloom are compared and analyzed. The results show that the maximum carbon segregation degree, the ratio of the local carbon concentration to the initial carbon concentration, is reduced from 1.292 to 1.254 with the application of F-EMS. In addition, the position of F-EMS is also an important factor. The maximum carbon segregation degrees are 1.254, 1.237 and 1.269 when the installation location of F-EMS is 14 m, 16 m and 18 m away from the meniscus, respectively. The optimal center solid fraction is about 0.1 at the F-EMS center for this study.
INTRODUCTION Macrosegregation is one of the major internal quality defects that occur in the continuous casting process.1,2 Continuous casting is a typical solidification process of multicomponent alloys. Solute redistribution happens when solute elements are rejected from the solidified dendrites during molten steel solidification. The solute-enriched melt ahead of the solidification front is removed by liquid flow over a long range, ultimately resulting in compositional inhomogeneity at the macroscopic level, which is known as macrosegregation.1,3,4 Macrosegregation cannot be eliminated entirely during the subsequent heat treatment, hot rolling or forging, which will lead to the heterogeneity of the mechanical properties of the final products.5,6 It is crucial to prevent and mitigate macrosegregation during the continuous casting process. For bloom casting, the implementation of mold electromagnetic stirring (M-EMS) is meant to promote the columnar-toequiaxed transition (CET) during solidification,
(Received May 6, 2020; accepted August 26, 2020)
which will subsequently improve the macrosegregation.7 Moreover, the combined stirring technology of M-EMS plus final electromagnetic stirring (FEMS) is frequently used to further reduce the macrosegregation of the as-cast product.7–10 F-EMS has a substantial effect on the heat and species transfer at the final stage of solidification by altering the melt flow in the mushy zone, which has been shown to be an effective method for improving the solute homogeneousness o
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