Search Results (4)

Herein, a three-dimensional mathematical model was established to investigate the metallurgical behavior of liquid steel in a funnel-shaped mold equipped with single-ruler electromagnetic braking (EMBr). The effects of mold thicknesses, electromagnetic intensity, and casting speed in flow behavior were investigated. The results indicate that with EMBr, multiple pairs of induced current loops are present in the horizontal section of the magnetic pole center, distributed in pairs between the jets and broad faces. The Lorentz force acting on the main jet, which impacts the downward and upward flow at adjacent broad faces, is opposite in direction. Increasing mold thickness results in a larger jet penetration depth, leading to a higher meniscus temperature near the narrow faces accompanied by elevated velocity and turbulent kinetic energy. EMBr can lead to a decrease in shell thickness and an improvement in its uniformity at mold exit. For the thickened mold, as the magnetic flux density increases and the casting speed decreases, the penetration depth of jets and velocity near the narrow faces and meniscus decreases. The shell thickness decreases as the casting speed increases, with the lowest non-uniformity coefficient of 6.78% observed at a casting speed of 5.0 m/min. Full article

The brake effect of the freestanding adjustable combination electromagnetic brake (FAC-EMBr) and EMBr ruler on the behavior of molten steel flow and the level fluctuation were investigated with the numerical method. The effects of the horizontal magnetic pole position (EMBr ruler), magnetic induction intensity, and casting speed on two types of electromagnetic brakes were studied. The numerical simulation results show that the magnetic field caused by the EMBr ruler is mainly distributed under the submerged entry nozzle (SEN), and it is very weak nearby the meniscus area. After the FAC-EMBr is applied, the magnetic field is mainly distributed in the area below the submerged entry nozzle, the upper roll region, and in the meniscus region. The application of the electromagnetic brake can effectively suppress the impact of the jet and decrease the molten steel velocity in the meniscus area. The brake effect of the EMBr ruler on the behavior of the molten steel flow and the level fluctuation is significantly influenced by the horizontal magnetic pole position. The increasing of the magnetic flux density can significantly increase the velocity of molten steel in the upper roll region and lead to an intense fluctuation in the steel/slag interface, as the horizontal magnetic field cannot cover the three key regions. The brake effect of the FAC-EMBr is less influenced by the variation of the process parameters due to the addition of vertical magnetic poles. Additionally, the “secondary braking effect” of the vertical magnetic poles can help to lower the increase of velocity in the upper roll region caused by the excessive magnetic induction intensity and the high casting speed. Therefore, even under the high casting speed conditions, the application of a new type of FAC-EMBr is also an efficient way to suppress the molten steel flow and level fluctuation at the meniscus area and decrease the possibility of slag entrapment. Full article

The turbulent phenomena occurring in the thin slab mold affect the final product quality. Therefore, it is essential to carry out studies to understand and control their occurrence. Current research aims to study the electromagnetic brake (EMBr) effects on the flow patterns in a funnel thin slab mold. The objective is to prevent the detrimental phenomenon known as dynamic distortions (DD) of the flow, applying the EMBr in the typical horizontal position (H-EMBr) and a new vertical position close to the narrow faces (V-EMBr). The fluid dynamics are simulated using the Reynolds stress model (RSM), the Volume of Fluid (VOF) model and the Maxwell equations in their magnetohydrodynamics (MHD) simplification. The results show that the H-EMBr effectively counteracts the DD phenomenon by reducing the submerged entry nozzle (SEN) ports' mass flow rate differences. The EMBr reduces the highest meniscus fluctuations from −10 to ±3 mm with a field intensity of 0.1T and almost 0 mm for higher field intensities. In contrast, the V-EMBr configuration does not reduce or control at all the DD phenomenon, even though eliminating the upper roll flows does not diminish the meniscus fluctuation amplitudes and induces new small roll flows close to the SEN's wall. Full article

Large eddy simulation (LES) of transient magnetohydrodynamic (MHD) turbulent flow under a single-ruler electromagnetic brake (EMBr) in a laboratory-scale, continuous-casting mold is presented. The influence of different electrically-conductive boundary conditions on the MHD flow and electromagnetic field was studied, considering two different wall boundary conditions: insulating and conducting. Both the transient and time-averaged horizontal velocities predicted by the LES model agree well with the measurements of the ultrasound Doppler velocimetry (UDV) probes. Q-criterion was used to visualize the characteristics of the three-dimensional turbulent eddy structure in the mold. The turbulent flow can be suppressed by both configurations of the experiment’s wall (electrically-insulated and conducting walls). The shedding of small-scale vortices due to the Kelvin–Helmholtz instability from the shear at the jet boundary was observed. For the electrically-insulated walls, the flow was more unstable and changed with low-frequency oscillations. However, the time interval of the changeover was flexible. For the electrically-conducting walls, the low-frequency oscillations of the jets were well suppressed; a stable double-roll flow pattern was generated. Electrically-conducting walls can dramatically increase the induced current density and electromagnetic force; hence they contribute to stabilizing the MHD turbulent flow. Full article