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Attachment of Alumina on the Wall of Submerged Entry Nozzle During Continuous Casting of Al-Killed Steel
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Northeastern University, China.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. (ENHETEN PROCESSER)ORCID iD: 0000-0002-3548-8638
2016 (English)In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 47, no 3, 2015-2025 p.Article in journal (Refereed) PublishedText
Abstract [en]

The mechanisms of the formation of different attachments on the walls of submerged entry nozzle (SEN) were studied for the processes of Al-killed steel (Ca-treated, HSLA) and ultra-low carbon Al-killed steel (ULC). To understand the mechanism, the types of inclusions in the steel taken in tundish and in bloom (or slab) were identified. In the case of ULC, the reoxidation product, micro-alumina particles were found to be the source of attachment on the inner wall of the SEN. To avoid reoxidation of the steel by the top slag, removal of the slag could be considered in order to improve the situation. No attached layer was found on the outer surface of the SEN after casting of the ULC steel. In the case of HSLA steel, an attached layer composed of plate-like alumina crystals was found in some trials. The entrainment of oxygen through the mold powder due to improper operation would be the reason for the formation of this type of attachment. The formation of the plate-like crystals was discussed with the help of CFD calculation.

Place, publisher, year, edition, pages
Springer, 2016. Vol. 47, no 3, 2015-2025 p.
Keyword [en]
Alumina, Aluminum, Carbon, Continuous casting, Nozzles, Slags, Al-killed steel, Alumina particles, Mold powders, Outer surface, Plate-like crystals, Re-oxidation, Submerged entry nozzles, Ultra low carbon, Low carbon steel
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-186945DOI: 10.1007/s11663-016-0624-yISI: 000375451200050ScopusID: 2-s2.0-84959077209OAI: oai:DiVA.org:kth-186945DiVA: diva2:929283
Note

QC 20160518

Available from: 2016-05-18 Created: 2016-05-16 Last updated: 2016-08-16Bibliographically approved
In thesis
1. Study on the Interaction between Refractory and Liquid Steel Regarding Steel Cleanliness
Open this publication in new window or tab >>Study on the Interaction between Refractory and Liquid Steel Regarding Steel Cleanliness
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The present thesis focuses on the interaction between refractory and liquid steel. The aim of this work is to understand the interaction behavior between refractory and liquid steel regarding steel cleanliness. The effect of different refractories on different inclusions in Al-killed steel was studied in a furnace. The sintering mechanism of filler sand were also investigated in laboratory. In the industrial trials, the attachments of different oxides on the walls of submerged entry nozzle (SEN) were discussed in the cases of high strength low alloy steel (HSLA) and ultra-low carbon steel (ULC).

It is found that the effect of alumina and spinel refractory on all the three types of inclusions is very little, while MgO refractory influences the inclusions depending on the activity of dissolved oxygen in liquid steel. At low oxygen level, alumina inclusions could transform into spinel inclusions with the help of MgO refractory, while the effect on spinel and calcium aluminate inclusions is not evident. On the other hand, when the activity of dissolved oxygen is high enough, the evolution of spinel inclusions from alumina inclusions could not be seen.

The reaction between chromite and silica grains leading to liquid formation is the main mechanism for the sintering of filler sand. The factors viz. steel composition, silica size and content, operation temperature and process holding time have a strong influence on the sintering of the filler sand. Smaller size and higher content of silica in sand, steel grades containing higher Mn and Al contents, higher temperature and longer holding time would result in serious sintering. The choice of the sand needs to take those factors into account.

The results show that solid alumina particles are always agglomerated on the inner wall of SEN in the case of ULC steel. The top slag with high FeO and MnO contents is considered as the main reason of this kind of attachments. The removal of slag might be a good method to avoid the attachments. In the case of HSLA steel, liquid calcium aluminate inclusions could attach on the inner wall of SEN as well. The smoothness of the inner wall of the SEN holds the key of liquid attachments. In addition, the attachment situation on the outer wall of SEN depends on the operations. The oxygen entrainment through the mold powder would result in the formation of plate-like alumina attachments. The control of reoxidation due to oxygen entrainment would help to avoid this situation.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. 48 p.
Keyword
refractory, inclusions, Al-killed steel, submerged entry nozzle, clogging
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-190071 (URN)978-91-7729-006-3 (ISBN)
Public defence
2016-09-15, Sal F3, Lindstedtsvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20160816

Available from: 2016-08-16 Created: 2016-08-04 Last updated: 2016-08-16Bibliographically approved

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