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On some positive effects of swirling flow for the continuous cast mould billets
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
2007 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

Continuous caster moulds are the last and most important stage in the steelmaking process, where inclusions can either be generated or removed. With increasing casting speed using conventional immersion nozzles critical problems, such as unstable bulk mould flow have been noticed. Mould flux entrapment due to vortex and shearing action from the oscillating surface waves have become of particular concern. It is therefore necessary to have a calm inlet flow at the entrance of the mould. Recently, it has been acknowledged that a swirl blade placed at the upstream of the immersion nozzle effectively resolves the problems arising from unstable bulk mould flow. Therefore, to increase the knowledge of effect of swirling flow on the flow pattern in the mould, fundamental mathematical models of a billet mould equipped with a swirl blade in the nozzle have been developed. The model was used to study the effect of divergent angle of the immersion nozzle and mould aspect ratio on the flow field and temperature distribution inside billets moulds. Data from water model experiments were used to verify the mathematical model predictions. A fairly good agreement was found between physical modeling data and predictions, which ensured that the numerical model is reliable. Thereafter, the differences between square and round billet moulds were studied. Next, the effect of changing aspect ratio of the rectangular mould on the fluid flow and heat transfer, while keeping mould surface area constant, was studied. Two types of immersion nozzles, bottomless and conventional, were also analyzed during the research. The model moulds were changed gradually from a square billet with an aspect ratio of 1x1 to a rectangular billet with an aspect ratio of 3x1. First, the temperature and velocity distributions were calculated. Later, unsteady calculations were done to determine velocity fluctuations on the meniscus level for two types of nozzles and several moulds geometries.

Place, publisher, year, edition, pages
Stockholm: KTH , 2007. , vi, 37 p.
Keyword [en]
swirling flow, round mould, divergent angle, aspect ratio, temperature distribution, velocity fluctuations, continuous casting of steel, mathematical modeling, CFD
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-4453OAI: oai:DiVA.org:kth-4453DiVA: diva2:12354
Presentation
2007-05-14, B3, KTH, Brinellvägen 23, Stockholm, 10:00
Opponent
Supervisors
Note

QC 20101110

Available from: 2007-06-26 Created: 2007-06-26 Last updated: 2014-07-10Bibliographically approved
List of papers
1. Development of flow field and temperature distribution during changing divergent angle of the nozzle when using swirl flow in a square continuous casting billet mould
Open this publication in new window or tab >>Development of flow field and temperature distribution during changing divergent angle of the nozzle when using swirl flow in a square continuous casting billet mould
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2007 (English)In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 47, no 1, 80-87 p.Article in journal (Refereed) Published
Abstract [en]

Recently, positive effects of swirl flow have been investigated, related to specific billet moulds with particular divergent angles in the immersion nozzles. (1-7)) Literature review showed that a systematic study of changes in the divergent angle in the immersion nozzle for continuous casting moulds had not been carried out. Therefore, in the present work we aim to investigate the development of flow field and temperature distribution inside the mould and on the meniscus while changing the divergent angle of the immersion nozzle. Swirl flow was used in the nozzle and the liquid entered a 3D square billet mould. Both physical and mathematical modelling was carried out to simulate nine different divergent angles between 0 and 160 degrees. The overall results of the study showed that a change in divergent angle has an effect on the flow pattern as well as the temperature distribution of the liquid steel in the mould. More specifically it was found that in the case of 100 degrees divergent angle nozzle billet we can observe a major shift of lower circulation compared to that of the 80 degrees nozzle billet. Furthermore, a noticeable increase of the temperature near the meniscus, for a square billet, and radial velocity component, for a round billet, was found when using the 100 degrees divergent angle nozzle compared to the 80 degrees divergent angle nozzle. Additionally, a uniform velocity and heat distribution was observed within a distance of 200 mm below the nozzle exit for nozzle outlets with 100 degrees divergent angles and larger.

Keyword
swirl flow, divergent angle of the immersion nozzle, billet continuous casting mould
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-14183 (URN)10.2355/isijinternational.47.80 (DOI)000245601400011 ()2-s2.0-34247189008 (Scopus ID)
Note

QC 20150629

Available from: 2010-07-23 Created: 2010-07-23 Last updated: 2017-12-12Bibliographically approved
2. Effect of nozzle angle on flow field and temperature distribution in a billet mould when using swirl flow
Open this publication in new window or tab >>Effect of nozzle angle on flow field and temperature distribution in a billet mould when using swirl flow
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2008 (English)In: STEEL RES INT, ISSN 1611-3683, Vol. 79, no 1, 31-39 p.Article in journal (Refereed) Published
Abstract [en]

Recently, interesting effects have been noted in studies of swirl flow, particularly regarding billet moulds when considering a specific divergent angle of the immersion nozzle. Therefore, in the present work a numerical analysis and water model study of the mould region of a continuous casting apparatus are performed with changing the outlet divergent angles of the immersion nozzle using swirling flow in the pouring tube, to control the heat and mass transfer in the continuous casting mould. To make our studies consistent with the previous research, which was done based on a square billet, this time we investigate round billets. The results show that the distance from the meniscus of the centres of both the lower and upper circulation loops decreases systematically with increasing the divergent angle. This, in turn, leads to: (i) a more active heat and mass transport near the meniscus (particularly over 100 degrees); (ii) a gradual change from a concentric circulation to a more clearly logarithmic spiral from the mould wall to the nozzle on the meniscus, which leads to more active heat and mass transfer; (iii) a decreased penetration depth of nozzle outlet flow (even at a comparatively small divergent angle such as 20 degrees) and a superheat dissipation in the melt.

Keyword
swirl flow, divergent angle immersion nozzle, round billet mould, continuous casting
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-14184 (URN)10.2374/SRI07SP023 (DOI)000253276600005 ()2-s2.0-39049156424 (Scopus ID)
Note

QC 20100723

Available from: 2010-07-23 Created: 2010-07-23 Last updated: 2016-05-02Bibliographically approved
3. Flow field development during changing aspect ratio of the billet CC caster using swirl flow
Open this publication in new window or tab >>Flow field development during changing aspect ratio of the billet CC caster using swirl flow
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(English)Article in journal (Refereed) In press
National Category
Subatomic Physics
Identifiers
urn:nbn:se:kth:diva-7356 (URN)
Note

QC 20101110

Available from: 2007-06-26 Created: 2007-06-26 Last updated: 2014-07-10Bibliographically approved

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