This paper reviews the current state of the art in the application of electromagnetic forces to control fluid flow to improve quality in continuous casting of steel slabs. Many product defects are controlled by flow-related phenomena in the mold region, such as slag entrapment due to excessive surface velocity and level fluctuations, meniscus hook defects due to insufficient transport of flow and superheat to the meniscus region, and particle entrapment into the solidification front, which depends on transverse flow across the dendritic interface. Fluid flow also affects heat transfer, solidification, and solute transport, which greatly affect grain structure and internal quality of final steel products. Various electromagnetic systems can affect flow, including static magnetic fields and traveling fields which actively accelerate, slow down, or stir the flow in the mold or strand regions. Optimal electromagnetic effects to control flow depends greatly on the caster geometry and other operating conditions. Previous works on how to operate electromagnetic systems to reduce defects are discussed based on results from plant experiments, validated computational models, and lab scale model experiments.

Electromagnetic Forces in Continuous Casting of Steel Slabs

This paper reviews recent trends of electromagnetic processing in steelmaking, casting and solidification processing. Electromagnetic vibration for controlling the solidified structure and application of microwave in materials processing are also presented. Aim of this paper is to prospect the recent trends in electromagnetic processing of materials.

Recent Progress of EPM in Steelmaking, Casting, and Solidification Processing

MHD analysis in hydromagnetic casting process of clad steel slabs

This study is to investigate the effect of electromagnetic brake (EMBr) on fluid flow and particle motion in steel slab continuous casting strands. The effect of slide gate moving on fluid flow pattern was discussed. A strong swirl and asymmetrical flow at the outports and, subsequently, inside the slab mold, was induced by slide gate. The application of EMBr would be a remedy to the swirl flow in the casting mold. Flow pattern has great influence on the trajectories of injected bubbles and nonmetallic inclusions. More bubbles tend to release from the top surface near the wide face opposite to the gate opening side without EMBr; while, they escape at the center place of the slab thickness when the EMBr was applied. Local brake type EMBr has a little effect on the overall removal fraction of nonmetallic inclusions, especially for the small ones. However, EMBr affects the distribution of inclusions on the cross section of the slab, and more inclusions were observed in the sub-surface layer of the slab.

Effect of Slide Gate and EMBr on the Transport of Inclusions and Bubbles in Slab Continuous Casting Strands

Abstract Ultrasonic Doppler velocimetry measurements and large eddy simulations were conducted on a laboratory-scale physical model of a steel continuous slab caster with a low-melting alloy, both with and without an applied single-ruler magnetic field in one of two different vertical orientations. The computational model agreed very closely with the measurements in all respects, including time-averaged flow, velocity profiles, and transient velocity histories at specific locations. The magnetic field altered both the classic double-roll flow pattern and the flow stability. Lowering the magnetic field below the nozzle caused steeper downward jet angles, lower surface velocities, lower turbulent kinetic energy at the surface, and better flow stability, especially toward the surface, and at higher frequencies. The experimental and computational results both show that the electromagnetic field should not be placed with its maximum directly across the nozzle ports, where it may aggravate unstable flow.

T. Ishii

Papers

Application of a DC magnetic field for the control of flow in the continuous casting strand