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Study on the formation of open-eye and slag entrainment in gas stirred ladle
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
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2007 (English)In: Steel Research International, ISSN 1611-3683, Vol. 78, no 12, 849-856 p.Article in journal (Refereed) Published
Abstract [en]

Laboratory experiments were carried out to study the phenomena related to open-eye formation in ladle treatment. Ga-In-Sn alloy with a melting temperature of 283 K was used to simulate the liquid steel, while MgCl2-Glycerol(87%) solution as well as HCl solution were used to simulate the ladle slag. No open-eye was formed at lower gas flow rates, but, occurred when gas flow reached a critical rate. This critical gas flow rate was found to depend significantly on the height of the top liquid. No noticeable amount of top liquid was observed in any of the samples taken from the metal bulk during gas stirring. To confirm this aspect, samples of slag-metal interface were taken around the open-eye in an industrial gas stirred steel ladle. No entrapped slag droplet was found in the solidified steel within the region between the interface and 2 cm from the interface. The accordance of the laboratory and industrial results suggests that the entrainment of slag into the steel bulk around the open-eye cannot be considered as the major contribution to inclusion formation.

Place, publisher, year, edition, pages
2007. Vol. 78, no 12, 849-856 p.
Keyword [en]
cold model, inclusion, slag entrapment, Ga-In-Sn alloy, open-eye, steel-slag interface
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-17211ISI: 000252709300002Scopus ID: 2-s2.0-38049165244OAI: oai:DiVA.org:kth-17211DiVA: diva2:335254
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2010-08-12Bibliographically approved
In thesis
1. Formation of Inclusions and their Development during Secondary Steelmaking
Open this publication in new window or tab >>Formation of Inclusions and their Development during Secondary Steelmaking
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Al–O relations in iron were investigated. Pure iron with varying Al content was equilibrated at 1873 K. The oxygen content of iron with higher Al content than 1.0 mass % was found to be much lower than previous works, while the oxygen content for Al content less than 1 mass% was found to be slightly higher. Further, a classification procedure of inclusions was developed using the commercial software INCA Feature. Three classes were made, spinel, TP-(CaO-Al2O3), and (CaO-Al2O3) class, corresponding to the inclusions found during degassing at Uddeholm Tooling. The results showed that the spinel phase disappeared after degassing along with a reduction in numbers for the two phase inclusion (TP-(CaO-Al2O3)). Pure calcium aluminates however showed an increasing trend in a majority of the heats. The chemical development of inclusions at OVAKO Steel in Hofors, Sweden was also established. According to the morphologies and compositions, the inclusions were classified into 5 different types, namely, (1) alumina inclusions, (2) calcium aluminate, (3) spinel+calcium aluminate, (4) calcium aluminate surrounded by a CaS shell, and (5) spinel+calcium aluminate surrounded by a CaS shell. Thereafter refractory lining samples with attached slag layer were taken from used ladles at the two steel plants. The morphologies of the slag layers and the phases present were examined. The precipitated phases found in the refractory were 3CaO.Al2O3, MgO.Al2O3 and CaO in the case of Ovako Steel and 3CaO.Al2O3 and 2CaO.SiO2 in the case of Uddeholm Tooling. To help the understanding, model calculations using THERMOCALC were carried out. The model predictions differed somewhat from the experimental observation, the predicted major phases were in line with the EDS analysis on the refractory samples. Finally experiments were carried out to study the slag entrainment related to the open-eye during ladle treatment. Ga-In-Sn alloy was used to simulate the liquid steel, while MgCl2-Glycerol(87%) solution was used to simulate the ladle slag. No noticeable amount of top liquid was observed in any of the samples taken from the metal bulk during gas stirring. To confirm this aspect, slag-metal interface samples were taken from an industrial gas stirred steel ladle. No entrapment was found in the steel. The accordance of the laboratory and industrial results suggests that the entrainment of slag into the steel bulk around the open-eye cannot be considered as the major contribution to inclusion formation.

Place, publisher, year, edition, pages
Stockholm: KTH, 2009. xi, 38 p.
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-10420 (URN)978-91-7415-276-0 (ISBN)
Public defence
2009-04-24, Sal F3, KTH, Lindstedtsvägen 26, Stockholm, 10:00 (English)
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Supervisors
Note
QC 20100812Available from: 2009-05-13 Created: 2009-05-13 Last updated: 2010-08-12Bibliographically approved

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