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Numerical Study on Steel Flow and Inclusion Behavior during a Ladle Teeming Process
KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
2013 (Engelska)Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
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.

Ort, förlag, år, upplaga, sidor
Stockholm: KTH Royal Institute of Technology, 2013. , s. xii, 38
Nyckelord [en]
steel flow, ladle teeming, numerical simulation, inclusion behavior, CFD, clogging, deposition.
Nationell ämneskategori
Metallurgi och metalliska material
Identifikatorer
URN: urn:nbn:se:kth:diva-118848ISBN: 978-91-7501-662-7 (tryckt)OAI: oai:DiVA.org:kth-118848DiVA, id: diva2:608914
Presentation
2013-03-21, Sefström (M131), Brinellvägen 23, KTH, Stockholm, 09:30 (Engelska)
Opponent
Handledare
Anmärkning

QC 20130305

Tillgänglig från: 2013-03-05 Skapad: 2013-03-01 Senast uppdaterad: 2013-03-05Bibliografiskt granskad
Delarbeten
1. Simulations of the LadleTeeming Process and Verification With Pilot Experiment
Öppna denna publikation i ny flik eller fönster >>Simulations of the LadleTeeming Process and Verification With Pilot Experiment
2013 (Engelska)Ingår i: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 84, nr 3, s. 276-287Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The ladle teeming process was investigated by 2D axis-symmetrical mathematical models and a pilot-plant experiment. Different turbulence models, including the low Reynolds number k-epsilon model and the realizable k-epsilon 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. At the late stage of the teeming process, the drain sink flow phenomenon was 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.

Nyckelord
drain sink, fluid flow, ladle, numerical simulation, pilot-plant experiment, teeming
Nationell ämneskategori
Metallurgi och metalliska material
Identifikatorer
urn:nbn:se:kth:diva-118658 (URN)10.1002/srin.201200155 (DOI)000315822700010 ()2-s2.0-84875200702 (Scopus ID)
Anmärkning

QC 20130404

Tillgänglig från: 2013-02-21 Skapad: 2013-02-21 Senast uppdaterad: 2017-12-06Bibliografiskt granskad
2. Turbulent Flow Phenomena and Ce2O3 Behavior during a Steel Teeming Process
Öppna denna publikation i ny flik eller fönster >>Turbulent Flow Phenomena and Ce2O3 Behavior during a Steel Teeming Process
2013 (Engelska)Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 53, nr 5, s. 792-801Artikel i tidskrift (Refereegranskat) 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.

Nyckelord
steel flow, ladle teeming, numerical simulation, inclusion behavior, CFD, clogging, deposition
Nationell ämneskategori
Metallurgi och metalliska material
Identifikatorer
urn:nbn:se:kth:diva-118566 (URN)10.2355/isijinternational.53.792 (DOI)000319547200008 ()2-s2.0-84879208887 (Scopus ID)
Anmärkning

Updated from "Accepted" to "Published" QC 20130705

Tillgänglig från: 2013-02-21 Skapad: 2013-02-20 Senast uppdaterad: 2017-12-06Bibliografiskt granskad

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