Investigations on Flow Pattern and Pressure inside SEN below Stopper Rod

Abstract

In continuous casting of steel, the casting rate is often controlled by a stopper rod placed in the tundish outlet where the submerged entry nozzle (SEN) tube begins. The flow pattern inside the SEN plays an important role for the bubble formation at the argon injection nozzle at the stopper rod tip. High flow velocities are reached in the small gap between stopper rod and the surrounding SEN walls, and a flow separation has to be expected after the gap due to the fast expansion of the cross section. According to theoretical considerations and to the simulations, the absolute pressure in the gap becomes very low for liquid steel, which can cause cavitation-like effects. PIV-flow measurements in a 1:1 scaled water model of the caster show a highly oscillating and asymmetric flow pattern with rapidly changing separation regions. The low pressure effects expected in liquid steel cannot be investigated on the water-model due to the lower density of water. In numerical simulations of the water-model, the choice of the turbulence model and the usage or the non-usage of geometrical symmetries for the bound of the computational domain have a great impact on the resulting flow pattern and the accuracy of the predicted pressure drop. The results of various turbulence models are compared with results from measurements on a water-model. It turns out that only a 3D model using advanced turbulence models (SST k-v or Large Eddy) produce acceptable results, while 2D simulations completely fail and the standard turbulence models (e.g. k-e) significantly underestimate the pressure drop even in a 3D simulation.

Visualization of Liquid Metal Two-phase Flows in a Physical Model of the Continuous Casting Process of Steel

“…[18] Obviously, the flow detaches from the side walls. Similar flow behavior was reported by Javurek et al [8] In case of gas injection, the void zones at the side walls absorb argon gas and expand downwards along the nozzle wall. The inertial forces of the liquid induce a breakup process of rather large, singular bubbles at the lower interface of the gas pockets.…”

“…The injected gas bubbles have a distinct influence on the flow pattern and may trigger instabilities in the mold, for instance, observations made on real casters showed correlations between argon gas pressure variations in the submerged entry nozzle (SEN) and mold meniscus perturbations. [1] Gas-liquid flows within the SEN and the mold have been addressed by many studies, whereas previous contributions to a better understanding of complex two-phase flows in metallurgical processes have been obtained by a combination of numerical modeling and up to 1:1-scale water models [2][3][4][5][6][7][8][9][10][11][12][13][14][15] and experimental trials at real casting machines. [1,16] Bai and Thomas [4] used 3-D numerical simulations and a water model to investigate the effect of argon bubbles on the turbulent steel flow in a sliding gate configuration.…”

Mathematical Modeling of Inclusions Deposition at the Upper Tundish Nozzle and the Submerged Entry Nozzle

“…For aluminum‐killed steel, alumina is the most common cluster material, which is produced during the deoxidation, from the interaction of refractory material and molten steel, and finally from the re‐oxidation of steel. Trying to reduce the clogging, argon injection through the nozzle wall has been used and recently, it has been injected at the stopper rod tip . Some others have tried to prevent nozzle clogging by calcium injection into the melt in order to produce liquid inclusions .…”

Fluidynamic Effects on the Deposition of Alumina Particles at the Upper Tundish Nozzle

“…Yuan et al [16] studied the SEN Clogging and Su-zhou et al [17] studied the inclusion removal near the mold top surface, both considering the overall effect of drag, gravity, buoyant, and Saffman forces on the inclusion trajectory, without analysing the individual relevancy of each force on the inclusion deposition. Trying to reduce the clogging, argon injection through the nozzle wall has been used and recently, it has been injected at the stopper rod tip [18][19][20][21][22][23]. Despite all these research works, the disruptive clogging phenomenon is still present nowadays; consequently, the main objective of the present research work is to explain the phenomenon of the non-uniform inclusion deposition at the nozzle wall and analyze the individual dynamic effect of inertial, gravitational, buoyant, pressure gradient, and Saffman forces on the deposited inclusion trajectories inside the upper tundish nozzle.…”