Influence of Turbulent Flows in the Nozzle on Melt Flow Within a Slab Mold and Stability of the Metal–Flux Interface

Abstract

The design of the ports of a casting nozzle has profound effects on the fluid flow patterns in slab molds. The influence of these outlets have also considerable effects on the turbulent flow and turbulence variables inside the nozzle itself. To understand the effects of nozzle design, three approaches were employed: a theoretical analysis based on the turbulent viscosity hypothesis, dimensional analysis (both analyses aided by computer fluid dynamics), and experiments using particle image velocimetry. The first approach yields a linear relation between calculated magnitudes of scalar fields of e (dissipation rate of kinetic energy) and k 2 (square of the turbulent kinetic energy), which is derived from the wall and the logarithmic-wall laws in the boundary layers. The smaller the slope of this linear relation is, the better the performance of a given nozzle is for maintaining the stability of the melt-flux interface. The second approach yields also a linear relation between flow rate of liquid metal and the cubic root of the dissipation rate of kinetic energy. In this case, the larger the slope of the linear relation is, the better the performance of a given nozzle is for maintaining the stability of the melt-flux interface. Finally, PIV measurements in a mold water model, together with equations for estimation of critical melt velocities for slag entrainment, were used to quantify the effects of nozzle design on the dynamics of the metal-slag interface. The three approaches agree in the characterization of turbulent flows in continuous casting molds using different nozzles.

Review on Modeling and Simulation of Continuous Casting

“…More advanced methods have been applied to simulate surface level and level fluctuations during continuous casting, including moving grid methods, the free‐surface Lattice–Boltzman method, and the Volume of Fluid (VOF) method . In addition to handling larger fluctuations accurately, these methods can capture the effects of surface tension and complex interactions between gravity and momentum forces, which can cause surface waves, sloshing, and slag entrainment.…”

“…[58,83] More advanced methods have been applied to simulate surface level and level fluctuations during continuous casting, including moving grid methods, [49,50,[108][109][110] the free-surface Lattice-Boltzman method, [111] and the Volume of Fluid (VOF) method. [84,[112][113][114] In addition to handling larger fluctuations accurately, these methods can capture the effects of surface tension and complex interactions between gravity and momentum forces, which can cause surface waves, sloshing, and slag entrainment. Simulations with VOF showed how surface instabilities move from the narrow face region to near the SEN with decreasing casting speed, owing to the decrease in dissipation of the jet momentum leaving the ports.…”

“…Simulations with VOF showed how surface instabilities move from the narrow face region to near the SEN with decreasing casting speed, owing to the decrease in dissipation of the jet momentum leaving the ports. [113,114] To understand the entrainment of slag droplets, starting from protrusions beneath the slag layer, entrainment has been modeled with VOF using LES on a fine grid and a special method to identify droplets, and found to match droplet sizes observed in a water model. [115] Using a moving grid method implemented into detached eddy simulations of the transient turbulent flow, dithering of the flow control device (e.g., stopper rod) at the wrong frequency was shown to cause severe surface sloshing instabilities, which matched predictions from an analytical model, and observations at the plant.…”

Mathematical Modeling of Multiphase Flow in Steel Continuous Casting

“…Some 22) VOF models have simulated gas pocket formation near the top of an SEN water model. Others [101][102][103][104] have used VOF to investigate the shape and stability of the top free surface in a casting mold (with/without gas injection) and compared their results with water model experiments. Zhao et al studied slag entrainment by benchmarking an water-oil experiment using VOF and simulating the formation of slag eyes, and detachment mechanisms of slag droplets depending on the casting speed.…”

Simulation for Mass Transfer Kinetics at Slag-Steel Interface during High Al Steel Continuous Casting

“…The flow field and surface fluctuation mold have a significant influence on the metallurgical thermodynamic behavior of the liquid slag layer. The researches of Calderon et al 22) and Ismael et al 23) reflected that the mold size, casting speed and SEN structure directly affected the distribution of steel flow in mold, and then affected the free surface fluctuation and slag entrapment. However, the present researches mainly focused on the mold surface behaviors through physical simulation and numerical simulation.…”