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Turbulent Flow Phenomena and Ce2O3 Behavior during a Steel Teeming Process
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
2013 (English)In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 53, no 5, 792-801 p.Article in journal (Refereed) Published
Abstract [en]

Steel flow phenomena and Ce2O3 inclusion behavior are presented in this paper. A three-dimensional model was developed to describe the steel flow phenomena and the inclusion behavior during a teeming process. The Kim-Chen modified k-ɛ turbulent model was used to simulate the turbulence properties and the Height-of-Liquid model was used to capture the interface between gas and steel. A Lagranian method was then used to track the inclusions and to compare the behaviors of different-size inclusions in the steel flow. In addition, a statistical analysis was carried out by the use of a stochastic turbulence model to investigate the behaviors of different-size inclusions at different nozzle regions. The results show that the steel flow was the most turbulent at the connection part of the straight pipe part and the expanding part of the nozzle. All inclusions with a diameter smaller than 20 μm 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 behaviors of large-size inclusions/clusters. The statistical analysis results indicate that the regions close to the connection region between different angled nozzle parts seem to be very sensitive with respect to deposition of inclusions.

Place, publisher, year, edition, pages
2013. Vol. 53, no 5, 792-801 p.
Keyword [en]
steel flow, ladle teeming, numerical simulation, inclusion behavior, CFD, clogging, deposition
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-118566DOI: 10.2355/isijinternational.53.792ISI: 000319547200008Scopus ID: 2-s2.0-84879208887OAI: oai:DiVA.org:kth-118566DiVA: diva2:607115
Note

Updated from "Accepted" to "Published" QC 20130705

Available from: 2013-02-21 Created: 2013-02-20 Last updated: 2017-12-06Bibliographically approved
In thesis
1. Numerical Study on Steel Flow and Inclusion Behavior during a Ladle Teeming Process
Open this publication in new window or tab >>Numerical Study on Steel Flow and Inclusion Behavior during a Ladle Teeming Process
2013 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

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.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. xii, 38 p.
Keyword
steel flow, ladle teeming, numerical simulation, inclusion behavior, CFD, clogging, deposition.
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-118848 (URN)978-91-7501-662-7 (ISBN)
Presentation
2013-03-21, Sefström (M131), Brinellvägen 23, KTH, Stockholm, 09:30 (English)
Opponent
Supervisors
Note

QC 20130305

Available from: 2013-03-05 Created: 2013-03-01 Last updated: 2013-03-05Bibliographically approved
2. A Study on Particle Motion and Deposition Rate: Application in Steel Flows
Open this publication in new window or tab >>A Study on Particle Motion and Deposition Rate: Application in Steel Flows
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Non-metallic inclusions in molten steel have received worldwide attention due to their serious influence on both the steel product quality and the steel production process. These inclusions may come from the de-oxidation process, the re-oxidation by air and/or slag due to an entrainment during steel transfer, and so on. The presence of some inclusion types can cause a termination of a casting process by clogging a nozzle. Thus, a good knowledge of the inclusion behavior and deposition rate in steel flows is really important to understand phenomena such as nozzle clogging. In this thesis, inclusion behaviors and deposition rates in steel flows were investigated by using mathematical simulations and validation by experiments.

A ladle teeming process was simulated and Ce2O3 inclusion behavior during a teeming stage was studied. A Lagrangian method was used to track the inclusions in a steel flow and to compare the behaviors of inclusions of different sizes. In addition, a statistical analysis was conducted by the use of a stochastic turbulence model to investigate the behaviors of different-sized inclusions in different nozzle regions. The results show that inclusions with a diameter smaller than 20 μm were found to have similar trajectories and velocity distributions in the nozzle. The 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 region close to the connection region of the straight pipe and the expanding part of the nozzle seems to be very sensitive for an inclusion deposition.

In order to know the deposition rate of non-metallic inclusions, an improved Eulerian particle deposition model was developed and subsequently used to predict the deposition rate of inclusions. It accounts for the differences in properties between air and liquid metals and considers Brownian and turbulent diffusion, turbophoresis and thermophoresis as transport mechanisms. A CFD model was firstly built up to obtain the friction velocity caused by a fluid flow. Then, the friction velocity was put into the deposition model to calculate the deposition rate.

For  the  case  of  inclusion/particle  deposition  in  vertical  steel  flows,  effects  on  the deposition rate of parameters such as steel flow rate, particle diameter, particle density, wall roughness and temperature gradient near a wall were investigated. The results show that the steel flow rate/friction velocity has a very important influence on the rate of the deposition of large particles, for which turbophoresis is the main deposition mechanism. For small particles, both the wall roughness and thermophoresis have a significant influence on the particle deposition rate. The extended Eulerian model was thereafter used to predict the inclusion deposition rate in a submerged entry nozzle (SEN). Deposition rates of different-size inclusions in the SEN were obtained. The result shows that the steel flow is non-uniform in the SEN of the tundish. This leads to an uneven distribution of the inclusion deposition rates at different locations of the inner wall of the SEN. A large deposition rate was found to occur at the regions near the SEN inlet, the SEN bottom and the upper region of two SEN ports.

For the case of an inclusion/particle deposition in horizontal straight channel flows, the deposition rates of particles at different locations of a horizontal straight pipe cross- section were found to be different due to the influence of gravity and buoyancy. For small particles with a small particle relaxation time, the gravity separation is important for their deposition  behaviors  at  high  and  low  parts  of  the  horizontal  pipe  compared  to  the turbophoresis. For large particles with a large particle relaxation time, turbophoresis is the dominating deposition mechanism.

 

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. xii, 47 p.
Keyword
steel flow, ladle teeming, continuous casting, non-metallic inclusion behavior, particle deposition, nozzle clogging, numerical simulation.
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-161915 (URN)978-91-7595-448-6 (ISBN)
Public defence
2015-04-17, Sal B2, Brinellvägen 23, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20150326

Available from: 2015-03-26 Created: 2015-03-19 Last updated: 2017-03-07Bibliographically approved

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