Effect of Single-Ruler Electromagnetic Braking (EMBr) Location on Transient Flow in Continuous Casting

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.

Effect of an Electrically-Conducting Wall on Transient Magnetohydrodynamic Flow in a Continuous-Casting Mold with an Electromagnetic Brake

“…For the GaInSn physical model, the wall conductance ratio for brass was 0.134, which is almost the same value for a real steel caster with a mold thickness of 90 mm assuming a thickness of the solidified shell of 5 mm [14]. For the cases of electrically-insulated walls, the wall conductance ratio was zero.…”

“…A DC magnetic field with a maximum field strength of B = 310 mT was installed perpendicular to the flow direction near the SEN ports along the wide wall of the mold. The distribution of the measured magnetic field [12,14] along the vertical casting direction is shown in Figure 1, and was considered in the current study. To simulate the solidified shell in the real mold, the inner walls of the wide mold faces were covered with thin brass plates with a thickness of 0.5 mm.…”

“…Electrically-conducting walls can dramatically increase the induced current density and electromagnetic force; hence they contribute to stabilizing the MHD turbulent flow.Electromagnetic braking (EMBr) is considered an effective flow control technology to maintain a stable "double-roll" flow pattern in the CC mold. Several commercial configurations of EMBr have been successfully used in slab casting, such as local EMBr [7-9], single-ruler EMBr [10][11][12][13][14], and double-ruler EMBr [15][16][17][18][19]. The flow of the electrically-conductive molten steel in the magnetic fields generates an electromagnetic force opposing the motion, and thus should be self-stabilizing.…”

“…However, the interaction between the diverse magnetic fields and the turbulent flow appears to be a rather complex phenomenon, so that it deserves further investigation.Computational fluid dynamics (CFD) allows a deeper inside view into the MHD flow in the mold. Extensive numerical simulations have been carried out considering various magnetic field configurations and flow parameters [9,[12][13][14][15][16][17][18][22][23][24][25]. Miao et al [22] reconstructed the peculiar phenomenon of the excitation of non-steady, non-isotropic, large-scale flow perturbations caused by the application of an external direct current (DC) magnetic field using a Reynolds-averaged Navier-Stokes (RANS)-SST turbulence model.…”

Review on Modeling and Simulation of Continuous Casting

“…This effect on stability has been confirmed with both LES models and with physical models using low‐melting‐temperature metal alloys . Positioning a field directly across or in front of the ports should be avoided because this destabilizes the flow by amplifying minor variations in jet angle: slightly low jets are deflected downward and slightly upward jets are deflected upward . The RANS approach cannot predict these transient phenomena.…”