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A Study of the Initial Mould Filling during Up-hill Ingot Casting
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The fluid flow in the mould during up-hill teeming is of great importance for the quality of the cast ingot and thereby the quality of the final steel products. At the early stage of the filling of an up-hill teeming mould, liquid steel flows with a high velocity from the runner into the mould. The resulting turbulence on the meniscus can lead to entrainment of mould flux. The entrained mould flux might subsequently end up as defects in the final product. It is therefore very important to get a less turbulent and more stable inlet flow in the entrance region of the mould, to minimize the interactions between the steel and the mould flux. It has been acknowledged recently that a swirling motion, induced using a helix shaped swirl blade in the submerged entry nozzle, is remarkably effective to control the fluid flow pattern in both the slab and billet type continuous casting moulds. The focus in this thesis is the effect of a swirling flow, generated through a helix shaped swirl blade inserted into the runner system of the up-hill casting system, as a new method of reducing the deformation of the rising surface and the unevenness of the flow during filling of the up-hill teeming mould. The study covers a theoretical part, including mathematical modelling and water modelling experiments. Moreover, a part with some novel plant trials to test the swirling technology at the steel plants of Ovako bar in Hofors and Scana steel in Björneborg. The swirl blade has two features: (1) to generate a swirling flow in the entrance nozzle and (2) to suppress the uneven flow developed after flowing through a bend. Water modelling was used to assert the effect of the swirl blade on rectifying of tangential and axial velocities in the filling tube for the up-hill teeming and also to verify the results from the numerical calculations. The effect of swirl in combination with a diverged nozzle was also investigated in a similar way, i. e. with water model trials and numerical calculations. The earlier studies, using water as a fluid, have shown that the placement of a swirl blade in the vertical part of the runner channel, at the entrance to the mould, will be beneficial for a calm initial filling of the ingot during casting. Later, the plant trials were carried out to test if it would be possible to place a ceramic swirl blade in the runner channel during filling of ingots and to investigate the effect of a widening of the entry nozzle. Because of constrains of the current design of the runner systems at the steel plants it was not possible to place the swirl blade at the entrance. Instead, the swirl blade was placed in the horizontal part of the runner system. The initial experiments with swirl blade in the runner showed that no production disturbances were found. More specifically, no problems with unusual refractory wear or cracks in the refractory were found. Also, the mould powder consumption was found to decrease when using the swirl blade in combination with an inlet with a 6° diverged nozzle. Thus, it was concluded that the use of swirl blade has a potential in the future to be used to influence the initial filling conditions in a positive way. In addition to the plant trials with swirl blade, separate trials of changing the inlet angle from 1.7° to 6° or 10° showed that the widened inlet area resulted in a decrease in mould powder consumption. However, the decrease was not to the same extent as for the case with swirl blade.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. , x, 70 p.
Keyword [en]
swirling flow, up-hill teeming, nozzle, casting, fluid flow, modelling, CFD, LDA, swirl, ingot casting, filling, red eye
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-105384ISBN: 978-91-7501-561-3 (print)OAI: oai:DiVA.org:kth-105384DiVA: diva2:570743
Public defence
2012-11-30, B3, Brinellvägen 23, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20121120

Available from: 2012-11-20 Created: 2012-11-20 Last updated: 2012-11-20Bibliographically approved
List of papers
1. Effect of nozzle swirl blade on flow pattern in runner during uphill teeming
Open this publication in new window or tab >>Effect of nozzle swirl blade on flow pattern in runner during uphill teeming
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2006 (English)In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 46, no 11, 1645-1651 p.Article in journal (Refereed) Published
Abstract [en]

Recent research has found a swirling flow induced by a twist-tape swirl blade inserted in the submerged entry nozzle of both slab and billet continuous casting molds to be remarkably effective for controlling the fluid-flow pattern in mold filling. The objective of the work reported on in this paper was to investigate usage of the swirl blade in the filling of molds in uphill teeming. Both mathematical and physical modeling were employed. Resulting velocity predictions and measurements corresponding to different positions in the water model were compared. Specific focus was on manipulation of the flow pattern by the swirl blade and its affect on flow unevenness, i.e. tangential and axial velocities. Good agreement was observed between the calculated and experimental results. The study's findings strongly suggest that equipping the entry nozzle of the uphill-teeming mold with a swirl blade would be a highly effective means of reducing flow unevenness during filling.

Keyword
Casting, CFD, Fluid flow, LDA, Modeling, Nozzle, Swirling flow, Uphill teeming
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-6743 (URN)10.2355/isijinternational.46.1645 (DOI)000242258800014 ()2-s2.0-33846391274 (Scopus ID)
Note
QC 20100909Available from: 2007-01-18 Created: 2007-01-18 Last updated: 2017-12-14Bibliographically approved
2. Effect of nozzle type and swirl on flow pattern for initial filling conditions in the mould for up-hill teeming
Open this publication in new window or tab >>Effect of nozzle type and swirl on flow pattern for initial filling conditions in the mould for up-hill teeming
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2007 (English)In: Steel Research International, ISSN 1611-3683, Vol. 78, no 3, 254-259 p.Article in journal (Refereed) Published
Abstract [en]

With increasingly more stringent requirements on steel quality and productivity in uphill teeming production, it is vital to attain more desirable fluid flow conditions in the filling of the mould. In this investigation, physical and mathematical modelling was carried out to study the effects of nozzle type and utilization of a swirl generator in the inlet nozzle on the flow pattern in the ingot mould during the initial filling period. Specific focus was on the effects on the resultant hump and axial velocities. Three cases were considered: 1) a straight nozzle, 2) a divergent nozzle, and 3) a divergent nozzle combined with a swirl generator. It was found that usage of the divergent nozzle, compared to the straight nozzle, resulted in a smaller hump and lower axial velocities in the bath. For the combination of divergent nozzle and swirl generator, these findings were even more pronounced, with the hump practically eliminated, and the axial velocities, as well as the turbulence at the meniscus, significantly lower. The findings of the study suggest that a divergent nozzle combined with a swirling flow generated in the nozzle could be used in the up-hill teeming process in purpose to get calmer initial filling conditions.

Keyword
Casting, Fluid flow, Modelling, Mould, Nozzle, Swirling flow
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-6744 (URN)000246043900013 ()2-s2.0-34047244029 (Scopus ID)
Note
QC 20101115. Uppdaterad från Accepted till Published (20101115).Available from: 2007-01-18 Created: 2007-01-18 Last updated: 2012-11-20Bibliographically approved
3. A First Attempt to Implement a Swirl Blade in Production of Ingots
Open this publication in new window or tab >>A First Attempt to Implement a Swirl Blade in Production of Ingots
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2010 (English)In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 50, no 12, 1763-1769 p.Article in journal (Refereed) Published
Abstract [en]

Plant trials were carried out to test if it would be possible to place a ceramic swirl blade in the runner channel during filling of ingots The initial experiments showed that no production disturbances were found More specifically no problems with unusual refractory wear or cracks in the refractory were found Thus it was concluded that the use of swirl blade has a potential in the future to be used to influence the initial filling conditions Also mathematical modeling was done in order to illustrate how it was possible to improve the layout of the runner system in order to increase the potential for use of swirl for the current plant conditions The results showed that the meniscus was not dampened as much when the swirl blade is positioned in a horizontal direction in the runner channel compared to the results of a previous physical modeling study where the swirl blade was placed in a vertical direction just before the steel entered the mold However if a horizontally positioned swirl blade is used in combination with an inlet with an angle of 15 degrees the hump height at the initial filling stage can be lowered from 100 to 58 mm compared to a case without a swirl blade This illustrates the potential to apply mold powder closer to the bottom without risking reoxidation due to reactions with steel and mold powder

Keyword
swirl, ingot, casting, modeling, plant trials
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-30536 (URN)000285666400006 ()2-s2.0-79952045044 (Scopus ID)
Note
QC 20110303Available from: 2011-03-03 Created: 2011-02-28 Last updated: 2017-12-11Bibliographically approved
4. Use of a Swirl Blade in Productio of Ingots with Focus on the Influence on the Red-Eye Diameter
Open this publication in new window or tab >>Use of a Swirl Blade in Productio of Ingots with Focus on the Influence on the Red-Eye Diameter
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2010 (English)Manuscript (preprint) (Other academic)
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-105389 (URN)
Note

QS 2012

Available from: 2012-11-20 Created: 2012-11-20 Last updated: 2012-11-20Bibliographically approved

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