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The Use of an Enhanced Eulerian Deposition Model to Investigate Nozzle Clogging During Continuous Casting of Steel
KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi. Swedish Defence Research Agency, Sweden.
KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
2014 (Engelska)Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 45, nr 6, s. 2414-2424Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Nozzle clogging caused by the build-up of non-metallic inclusions on ceramic walls is a serious industrial problem during continuous casting of steel. The current theoretical study uses the extended Eulerian model to predict the inclusion deposition rate in a submerged entry nozzle (SEN). The model considers Brownian and turbulent diffusion, turbophoresis, and thermophoresis as transportation mechanisms. First, the steel flow in a tundish was simulated using a three-dimensional CFD model. The obtained flow parameter in a SEN was then put into the Eulerian deposition model to predict the deposition rate of non-metallic inclusions. Thereafter, the deposition rates of different-size inclusions in the SEN were predicted and compared. 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. In addition, large size inclusions among the size of inclusions considered show a large deposition rate, due to the strong effect of turbophoresis.

Ort, förlag, år, upplaga, sidor
2014. Vol. 45, nr 6, s. 2414-2424
Nyckelord [en]
Computational fluid dynamics, Computer simulation, Continuous casting, Deposition, Deposition rates, Nozzles, Continuous casting of steels, Deposition modeling, Industrial problem, Non-metallic inclusions, Submerged entry nozzles, Three-dimensional CFD model, Transportation mechanism, Turbulent diffusion
Nationell ämneskategori
Metallurgi och metalliska material
Identifikatorer
URN: urn:nbn:se:kth:diva-158819DOI: 10.1007/s11663-014-0145-5ISI: 000345089900043Scopus ID: 2-s2.0-84920255184OAI: oai:DiVA.org:kth-158819DiVA, id: diva2:783888
Anmärkning

QC 20150127

Tillgänglig från: 2015-01-27 Skapad: 2015-01-12 Senast uppdaterad: 2017-12-05Bibliografiskt granskad
Ingår i avhandling
1. A Study on Particle Motion and Deposition Rate: Application in Steel Flows
Öppna denna publikation i ny flik eller fönster >>A Study on Particle Motion and Deposition Rate: Application in Steel Flows
2015 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
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.

 

Ort, förlag, år, upplaga, sidor
Stockholm: KTH Royal Institute of Technology, 2015. s. xii, 47
Nyckelord
steel flow, ladle teeming, continuous casting, non-metallic inclusion behavior, particle deposition, nozzle clogging, numerical simulation.
Nationell ämneskategori
Metallurgi och metalliska material
Identifikatorer
urn:nbn:se:kth:diva-161915 (URN)978-91-7595-448-6 (ISBN)
Disputation
2015-04-17, Sal B2, Brinellvägen 23, KTH, Stockholm, 10:00 (Engelska)
Opponent
Handledare
Anmärkning

QC 20150326

Tillgänglig från: 2015-03-26 Skapad: 2015-03-19 Senast uppdaterad: 2017-03-07Bibliografiskt granskad

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