Simulations of the Ladle Teeming Process and Verification With Pilot Experiment

Inclusions in molten steel have received worldwide concern due to their serious influence on both the steel product quality and the steel production process. These inclusions may come from the deoxidation process, reoxidation by air and/or slag due to an entrainment during steel transfer, and so on. They can break up a casting process by clogging a nozzle. A good knowledge on both steel flow and inclusion behavior is really important to understand nozzle clogging, as well as to take some possible measures to alleviate clogging. In this thesis, steel flow and inclusion behavior during a teeming process were investigated by mathematical simulations with verification by pilot-plant experiments.Firstly, steel flow phenomena during a ladle teeming process were studied. Different turbulence models, including the low Reynolds number k-ɛ model and the realizable k-ɛ model both with an enhanced wall treatment (EWT) and a standard wall function (SWF), were used to simulate this process. All of these turbulence model predictions generally agreed well with the experimental results. The velocity distributions in the nozzle were also predicted by these turbulence models. A large difference of the boundary-layer velocity predicted with these two near wall treatment methods was found. At the late stage of the teeming process, the drain sink flow phenomena were studied. The combination of an inclined ladle bottom and a gradually expanding nozzle was found to be an effective way to alleviate a drain sink flow during teeming.Then, inclusion behavior during a teeming stage was studied. A Lagranian method was used to track the inclusions in steel flow and compare the behaviors of different-size inclusions. In addition, a statistical analysis was conducted by the use of a stochastic turbulence model to investigate the behaviors of different-size inclusions in different nozzle regions. Inclusions with a diameter smaller than 20μm were found to have a similar trajectory and velocity distribution in the nozzle. However, inertia force and buoyancy force were found to play an important role for the behavior of large-size inclusions or clusters. The statistical analysis results indicate that the regions close to the connection between different angled nozzle parts seem to be very sensitive for an inclusion deposition.

[1]  P. Jönsson,et al.  Effect of Interfacial Energy on the Drain Sink Formation Height , 2009 .

[2]  Maofa Jiang,et al.  Transient Flow and Inclusion Removal in Gas Stirred Ladle during Teeming Process , 2010 .

[3]  R. Morales,et al.  Mathematical simulation of fluid dynamics during steel draining operations from a ladle , 2006 .

[4]  Yuhua Pan,et al.  Numerical studies on the parameters influencing steel ladle heat loss rate, thermal stratification during holding and steel stream temperature during teeming , 2003 .

[5]  P. Jönsson,et al.  Prediction and Disarming of Drain Sink Formation during Unsteady-state Bottom Teeming , 2009 .

[6]  S. Mazumdar,et al.  Entrainment during Tapping of a Model Converter Using Two Liquid Phases , 1995 .

[7]  S. C. Koria,et al.  Model studies of slag carry-over during drainage of metallurgical vessels , 1994 .

[8]  K. Kuwana,et al.  Scale-Model Experiment and Numerical Simulation of a Steel Teeming Process , 2008 .

[9]  W. Pluschkell,et al.  Model investigations of slag flow during last stages of ladle teeming , 1987 .

[10]  Y. Sahai,et al.  Effect of slag cover on heat loss and liquid steel flow in ladles before and during teeming to a continuous casting tundish , 1992 .

[11]  J. M. Camplin,et al.  Mathematical Modelling of Thermal Stratification and Drainage of Steel Ladles , 1992 .

[12]  George S. Springer,et al.  The formation of a dip on the surface of a liquid draining from a tank , 1967, Journal of Fluid Mechanics.

[13]  Carl-Erik Grip,et al.  Prediction of Emptying Flows in Ladles and Verification with Data from Trace Element Plant Trials , 1997 .

[14]  Marcela B. Goldschmit,et al.  Experimental and numerical analysis of ladle teeming process , 2004 .

[15]  Roderick I. L. Guthrie,et al.  Slag entraining vortexing funnel formation during ladle teeming: similarity criteria and scale-up relationships , 2002 .

[16]  Arun S. Mujumdar,et al.  A comparative study of five low Reynolds number k–ε models for impingement heat transfer , 2005 .

[17]  Keh-Chin Chang,et al.  A Modified Low-Reynolds-Number Turbulence Model Applicable to Recirculating Flow in Pipe Expansion , 1995 .

[18]  D. Sichen,et al.  Fluid Flow and Heat Transfer in the Ladle during Teeming , 2011 .

[19]  Seppo Louhenkilpi,et al.  A model for predicting the melt temperature in the ladle and in the Tundish as a function of operation parameters during continuous casting , 2005 .