Mathematical simulation of fluid dynamics during steel draining operations from a ladle

Abstract

Fluid flow dynamics during ladle drainage operations of steel under isothermal and nonisothermal conditions has been studied using the turbulence shear stress transport k-model (SST k-) and the multiphase volume of fluid (VOF) model. At high bath levels, the angular velocity of the melt, close to the ladle nozzle, is small rotating anticlockwise and intense vertical-recirculating flows are developed in most of the liquid volume due to descending steel streams along the ladle vertical wall. These streams ascend further downstream driven by buoyancy forces. At low bath levels, the melt, which is close to the nozzle, rotates clockwise with higher velocities whose magnitudes are higher for shorter ladle standstill times. These velocities are responsible for the formation and development of a vortex on the bath free surface, which entrains slag into the nozzle by shear-stress mechanisms at the metal-slag interface. The critical bath level or bath height for this phenomenon is 0.35 m (in this particular ladle design) for a ladle standstill time of 15 minutes and decreases with longer ladle standstill times. At these steps, the vertical-recirculating flows are substituted by complex horizontal-rotating flows in most of the liquid volume. Under isothermal conditions, the critical bath level for vortex formation on the melt free surface is 0.20 m, which agrees very well with that determined with a 1/3 scale water model of 0.073 m. It is concluded that buoyancy forces, originated by thermal gradients, as the ladle cools, are responsible for increasing the critical bath level for vortex formation. Understanding vortex mechanisms will be useful to design simple and efficient devices to break down the vortex flow during steel draining even at very low metal residues in the ladle.

Numerical Study of Multiphase Flow Dynamics of Plunging Jets of Liquid Steel and Trajectories of Ferroalloys Additions in a Ladle during Tapping Operations

“…The standard k-ε two-equation turbulence model is employed to determine the effective viscosity μ eff, and the detailed equations can be found elsewhere. [13][14][15][16] The trajectory of each particle was calculated by using the Lagrangian-Lagrangian approach, 11,17) which considers the force balance acting on the particle:…”

New Process with Argon Injected into Ladle around the Tapping Hole for Controlling Slag Carry-over during Continuous Casting Ladle

“…During the ladle teeming process, slag carry-over from ladle to tundish not only decreases the heats of continuous casting due to the slag accumulation in the tundish, but also worsens the steel cleanness [1][2][3]. Moreover, to maximize metallic yield and reduce costs, the steel residual is highly desirable to be as small as possible.…”

“…Therefore, for the sake of cleaner steel, improved yield, and higher production, the onset of slag carry-over should be stalled as long as possible during ladle teeming. According to the literature [1][2][3][4][5], two different mechanisms can lead to slag carry-over in teeming ladle: vortex or drain sink. Vortex is characterized by high tangential velocities in the neighborhood of the tapping hole, and can develop even with a high bath height of steel in the teeming ladle.…”

“…A drain sink is always present at the end of the process and takes place when the bath height of the steel is approximately equal to the nozzle diameter [4,6,16]. Several researchers claim that there was no vortex formation and slag carry-over was caused by drain sink in the teeming ladle [4,8], while more researchers reported that vortex was formed prior to the drain sink formation [1][2][3]7,17].…”

Mechanism Analysis of Free-Surface Vortex Formation during Steel Teeming

“…However, they did not specifically analyze the vortex forming process. Davila et al 11) used a VOF model to simulate steel teeming under thermal insulated and thermal non-insulated conditions. They pointed out that the vortex formation height increased due to buoyancy caused by temperature gradients.…”