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Modeling of Initial Mold Filling in Uphill Teeming Process Considering a Trumpet
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
2012 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The flow pattern in the uphill teeming process has been found to be closely related to the quality of ingots and further to affect the yield of ingot production, which is crucial for the 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 aim of this study is to investigate the flow pattern of steel in the gating system and molds during the initial filling stage. In addition, to study the utilization of swirl blade implemented at the bottom of the vertical runner on the improvement of initial filling condition in the mold. A three dimensional model of two molds gating system for 6.2 ton ingots from Scana Steel was adopted in the present work. A reduced geometry model including one mold and a runner, based on the method from previous researchers, was also used for comparison with the current more extensive model. Moreover, a reduced geometry model including one swirl blade and a runner was simulated to find effects of an increased-length vertical runner on the flow pattern improvement at the vertical runner outlet. Flow pattern, hump height and wall shear stress were respectively studied.

A reduced geometry with homogenous inlet conditions 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 implementation of swirl blades gives a chaotic initial filling condition with a considerable amount of droplets being created when steel enters the molds during the first couple of seconds. However, a more calm filling condition with less fluctuation is achieved at the molds after a short while. Moreover, the orientation of the swirl blades affects he flow pattern of the steel. A proper placement of a swirl blade improves the initial filling conditions. The utilization of swirl blades might initially result in larger hump height. However, it gives fewer fluctuations as the casting proceeds. In the model without swirl blades, the maximum wall shear stress fluctuates with a descending trend as the filling proceeds. An implementation of swirl blades can decrease and stabilize the wall shear stress in the gating system. A special attention should be made in choosing refractory at the center stone, the horizontal runner near center stone and the vertical runner at the elbow. This is where the wall shear stress values are highest or where the exposure times are long.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. , xii, 28 p.
Keyword [en]
gating system; uphill teeming; ingot casting; swirl blade; flow pattern; realizable k-ε model; CFD; mathematical modeling.
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-73948OAI: oai:DiVA.org:kth-73948DiVA: diva2:489109
Presentation
2012-02-24, MAVES konferensrum, Brinellvägen 23, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20120203Available from: 2012-02-03 Created: 2012-02-02 Last updated: 2012-02-03Bibliographically 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

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