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Effect of nozzle type and swirl on flow pattern for initial filling conditions in the mould for up-hill teeming
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.ORCID iD: 0000-0003-1919-9964
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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.

Place, publisher, year, edition, pages
2007. Vol. 78, no 3, 254-259 p.
Keyword [en]
Casting, Fluid flow, Modelling, Mould, Nozzle, Swirling flow
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-6744ISI: 000246043900013Scopus ID: 2-s2.0-34047244029OAI: oai:DiVA.org:kth-6744DiVA: diva2:11541
Note
QC 20101115. Uppdaterad från Accepted till Published (20101115).Available from: 2007-01-18 Created: 2007-01-18 Last updated: 2012-11-20Bibliographically approved
In thesis
1. Effect of swirling blade on flow pattern in nozzle for up-hill teeming
Open this publication in new window or tab >>Effect of swirling blade on flow pattern in nozzle for up-hill teeming
2006 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

The fluid flow in the mold during up-hill teeming is of great importance for the quality of the cast ingot and therefore the quality of the final steel products. At the early stage of the filling of an up-hill teeming mold, liquid steel enters, with high velocity, from the runner into the mold and the turbulence on the meniscus could lead to entrainment of mold flux. The entrained mold flux might subsequently end up as defects in the final product. It is therefore very important to get a mild and stable inlet flow in the entrance region of the mold. It has been acknowledged recently that 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 molds. This result in increased productivity and quality of the produced steel. Due to the result with continuous casting there is reason to investigate the swirling effect for up-hill teeming, a casting method with similar problem with turbulence.

With this thesis we will study the effect of swirling flow generated through a swirl blade inserted into the entry nozzle, 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 mold. The swirling blade has two features: (1) to generate a swirling flow in the entrance nozzle and (2) to suppress the uneven flow, generated/developed after flowing through the elbow. The effect of the use of a helix shaped swirl blade was studied using both numerical calculations and physical modelling. Water modelling was used to assert the effect of the swirling 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 diverged nozzle was also investigated in a similar way, i. e. with water model trials and numerical calculations.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006. x, 33 p.
Series
ISRN KTH/MSE--06/68--SE+APRMETU/AVH
Keyword
swirling flow, up-hill teeming, nozzle, casting, fluid flow, modelling, CFD, LDA.
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-4269 (URN)978-91-7178-521-3 (ISBN)
Presentation
2007-01-19, Sal B2, KTH, Brinellvägen 23, Stockholm, 11:00
Opponent
Supervisors
Note
QC 20101115Available from: 2007-01-18 Created: 2007-01-18 Last updated: 2010-11-15Bibliographically approved
2. A Study of the Initial Mould Filling during Up-hill Ingot Casting
Open this publication in new window or tab >>A Study of the Initial Mould Filling during Up-hill Ingot Casting
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
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:nbn:se:kth:diva-105384 (URN)978-91-7501-561-3 (ISBN)
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

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