Abstract

AbstractSoft-contact of molten steel can be achieved by applying a high-frequency electromagnetic field above the mold of continuous casting, which can effectively eliminate surface defects and achieve billets with no cracks and no oscillation marks. It also has some influence on the mold flux. In this study, the effect of a high-frequency electromagnetic field (20 kHz) on a mold flux flow field was simulated using a finite element software, and the slag film was extracted using a slag film simulator. The effect of the high-frequency magnetic field on the microstructure of the mold flux was analyzed using X-ray diffraction, Raman spectroscopy, and mineral phase testing. The results show that the high-frequency electromagnetic field disrupts the orderly movement and increases the movement rate of the liquid flux. The precipitate phase of the slag film did not change, but the silicate dimer Q1 decreased, the chain Q2 increased, and the network degree was increased. The slag film structure changed from the original two-layer form of crystalline layer–glass layer into a three-layer form of crystal layer–glass layer–crystal, and the crystallization ratio increased by 35% on average. The grain-size melilite granularity was reduced from the original 0.12 to 0.005 mm.

Highlights

  • Soft-contact electromagnetic continuous casting technology can significantly improve the billet surface quality, which has been an interest in the field of metallurgy [1]

  • The electromagnetic stress produced by the alternating current (AC) magnetic field reduces the contact pressure between the molten steel and mold wall and decreases the effect of mold oscillation on the billet surface quality, such that the molten steel achieves a “soft contact” [2,3]

  • Okazawa et al [13] studied the change of flux viscosity in mold flux, and the results showed that the flux viscosity decreased under direct current (DC) but increased under AC

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Summary

Introduction

Soft-contact electromagnetic continuous casting technology can significantly improve the billet surface quality, which has been an interest in the field of metallurgy [1]. Soft-contact electromagnetic continuous casting technology research focuses mainly on the softcontact mold, the electromagnetic field imposition method, the electromagnetic field distribution, meniscus shape control, and mechanisms for improving billet surface quality aspects [4,5,6,7,8,9,10]. Studies on the effects of the electric field on flux mainly concentrated on the conductivity, viscosity, and crystallization characteristics under the action of DC or AC, while its influence on the microstructure of flux under a high-frequency alternating electromagnetic field has not yet been reported.

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