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Some Aspects of Improving Initial Filling Conditions and Steel Cleanliness by Flow Pattern Control Using a Swirling Flow in the Uphill Teeming Process
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The flow pattern has widely been recognized to have an impact on the exogenous non-metallic inclusion generation in the gating system and mold flux entrapment in the uphill teeming process. Thus, a well-controlled flow pattern during the teeming process can improve the quality of ingots and further increase the yield during steel production. The current study focused on investigating and optimizing the flow pattern of steel in the gating system and molds to improve steel cleanliness during the initial filling moment. A mathematical model considering a trumpet was initially compared to a reduced model only considering part of the runner channel. Thereafter, the influence of swirl blades implemented at the bottom of the vertical runner on the improvement of initial filling conditions in the molds was investigated in a model considering the entire mold system including a trumpet. The effects of a swirl blade orientation on a swirling flow were further discussed. The simulation results, when utilizing swirl blades, were also verified by plant trials performed at Scana Steel. In addition, a new novel swirling flow generation component, TurboSwirl, was studied in a model considering the entire mold system including a trumpet. The model was based on modifications of the refractory geometry at the elbow of the runners near the mold without the usage of an inserted flow control device in the gating system. Owing to its great potential for improving the flow pattern of steel during the initial filling moment, the effect of TurboSwirl on steel cleanliness was also studied. The results showed that the initial filling conditions during the uphill teeming process can be improved by using a swirl blade or a TurboSwirl in the gating system. This makes it possible to further decrease the initial position of mold powder bags. In addition, it reduces the possibilities of exogenous non-metallic inclusion generation in the gating system as well as mold flux entrapment in the mold during the uphill teeming process. However, the utilization of swirl blades created a considerable amount of droplets when steel entered the molds during the first couple of seconds, which also was verified by the plant trials. The introduction of TurboSwirl showed a greater potential than a swirl blade due to a more evenly distributed swirling flow. The DPM model adopted in the simulations revealed that the TurboSwirl can improve steel cleanliness by increasing the non-metallic inclusion collision rate both with respect to Stokes and turbulent collisions.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. , xii,, 61 p.
Keyword [en]
uphill teeming, ingot casting, flow pattern, swirl blade, TurboSwirl, realizable k-ε model, CFD.
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-117718ISBN: 978-91-7501-596-5 (print)OAI: oai:DiVA.org:kth-117718DiVA: diva2:602744
Public defence
2013-02-22, B1, Brinellvägen 23, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20130204

Available from: 2013-02-04 Created: 2013-02-03 Last updated: 2013-02-04Bibliographically approved
List of papers
1. Mathematical Modeling of Initial Filling Moment of Uphill Teeming Process Considering a Trumpet
Open this publication in new window or tab >>Mathematical Modeling of Initial Filling Moment of Uphill Teeming Process Considering a Trumpet
2011 (English)In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 51, no 9, 1461-1467 p.Article in journal (Refereed) Published
Abstract [en]

The flow pattern in the uphill teeming process has been found to be closely related to the quality of ingots and further affects the yield of ingots production, which is crucial for steel making process. The formation of non-metallic inclusion and entrapment of mold flux has been considered to be affected by the flow pattern in the gating system and molds by many previous researchers. The emphasis of this study is focused on the flow pattern of steel in the gating system and molds during the initial stage of the mold filling process. A three dimensional model of two molds gating system for 6.2 ton ingots from Scana Steel is adopted in the present work. A reduced geometry including one mold and a runner is also used for comparison with the present results. In addition, the realizable k-epsilon model was used to study the flow pattern in uphill teeming process. The predictions were compared with practical filling information from industrial data and results from previous researches. It concludes that a reduced geometry with homogenous inlet condition fails to describe the fluctuating conditions present as the steel enters the mold. However, the trends are very similar when comparing the (hump height-surface height) evolution over time. The maximum wall shear stress fluctuates with a descending trend. A special attention should be made in choosing refractory at center stone, the horizontal runner and the vertical runner at elbow, where the wall shear stress values are highest or with long exposure time.

Keyword
gating system, uphill teeming, ingot casting, realizable k-epsilon model, CFD, mathematical modeling
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-45211 (URN)10.2355/isijinternational.51.1461 (DOI)000295391700014 ()2-s2.0-80054086283 (Scopus ID)
Note
QC 20111028Available from: 2011-10-28 Created: 2011-10-28 Last updated: 2017-12-08Bibliographically approved
2. Modeling of Initial Mold Filling with Utilization of Swirl Blades
Open this publication in new window or tab >>Modeling of Initial Mold Filling with Utilization of Swirl Blades
2012 (English)In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 52, no 6, 1066-1071 p.Article in journal (Refereed) Published
Abstract [en]

 The flow pattern in the uphill teeming process has been found to be closely related to the quality of ingots regarding the formation of non-metallic inclusions and entrapment of mold flux. The filling conditions can be improved by the utilization of a swirl blade in the runner. The emphasis of this study is to investigate the flow pattern of steel in the gating system and molds with swirl blades implemented at the bottom of the vertical runners during the initial stage of the mold filling process based on the authors' previous study. A two-mold gating system was adopted in the study and different orientations of the swirl blade were studied. In addition, same calculation method and boundary conditions were used to study the flow pattern in the uphill teeming. The results show that more calm filling conditions with less fluctuations are achieved in the molds with the implementation of swirl blades. However, a chaotic initial filling condition with a considerable amount of droplets is created when steel enters the molds. In addition, the orientation of the swirl blades affects the flow pattern of the steel. From the current results it is clear that a parallel placement of the swirl blade is better than a perpendicular placement of the swirl blade. Moreover, the fluctuations of the hump height decrease as the filling proceeds. In addition, the implementation of swirl blades can decrease and stabilize the wall shear stress value in the gating system.

Keyword
gating system, uphill teeming, ingot casting, swirl blade, flow pattern, realizable k-epsilon model, CFD, mathematical modeling
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-74699 (URN)000305593800015 ()2-s2.0-84863097257 (Scopus ID)
Note

QC 20120717

Available from: 2012-02-03 Created: 2012-02-03 Last updated: 2017-12-08Bibliographically approved
3. Plant Trials with Utilization of Swirl Blades at Scana Steel
Open this publication in new window or tab >>Plant Trials with Utilization of Swirl Blades at Scana Steel
2012 (English)Report (Other academic)
Series
Rapport Jernkontoret, T024-183
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-117721 (URN)
Note

QC 20130204

Available from: 2013-02-04 Created: 2013-02-04 Last updated: 2013-02-04Bibliographically approved
4. Uphill Teeming Utilizing TurboSwirl to Control Flow Pattern in Mold
Open this publication in new window or tab >>Uphill Teeming Utilizing TurboSwirl to Control Flow Pattern in Mold
2013 (English)In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 84, no 9, 837-844 p.Article in journal (Refereed) Published
Abstract [en]

The flow pattern has widely been recognized to have an impact on the exogenous non-metallic inclusion generation in the gating system and mold flux entrapment in the mold in the uphill teeming process. The possible solutions of the flow pattern control are required to be reliable and practical in order to improve the yield and the ingot quality in the steel production. In this work, a mathematical model of a new novel swirling flow generation component, TurboSwirl, was studied to investigate the flow pattern of steel in the gating system and molds based on the authors' previous study. The same calculation method and boundary conditions were adopted. The results show that a much calmer initial filling condition with less fluctuations is achieved in the mold with a swirling flow by using the TurboSwirl compared to previous studies. In addition, the initial position of the mold powder bags can further be lowered in the mold due to a decreased hump height. Moreover, the difference between the hump height and the surface height in the present model has a maximum value of 83 mm, which gives a lower risk of mold flux entrapment. Furthermore, the maximum wall shear stress value can generally be lowered with less fluctuations after the first hump formation in the mold at 2.5 s from the teeming start. In conclusion, the initial filling conditions can be substantially improved by the use of TurboSwirl flow pattern control. In this work, a new novel swirling flow generation component, TurboSwirl, is presented for the next generation of ingot casting. Due to its great potential in enhancing the steel cleanliness, it is highly recommended to apply this component in the steel producing industry so as to further improve the yield and quality of ingots.

Keyword
flow pattern, ingot casting, mathematical modeling, realizable k-ε model, TurboSwirl
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-117722 (URN)10.1002/srin.201200263 (DOI)000327745700002 ()2-s2.0-84883542473 (Scopus ID)
Funder
Vinnova
Note

QC 20131204. Updated from submitted to published.

Available from: 2013-02-04 Created: 2013-02-04 Last updated: 2017-12-06Bibliographically approved
5. Effect of TurboSwirl on Steel Cleanliness during Ingot Filling
Open this publication in new window or tab >>Effect of TurboSwirl on Steel Cleanliness during Ingot Filling
(English)Manuscript (preprint) (Other academic)
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-117723 (URN)
Note

QS 2013

Available from: 2013-02-04 Created: 2013-02-04 Last updated: 2013-02-04Bibliographically approved

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