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Effect of Temperature on Oxygen Activity during Ladle Treatment
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
2008 (English)In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 48, no 4, 438-445 p.Article in journal (Refereed) Published
Abstract [en]

The effect of temperature on oxygen activity in steel was studied in plant trials where temperature and oxygen activity were measured at two depths and at the same time during different parts of ladle refining. The results show that large temperature gradients exist towards the surface of the steel melt for the sampling occasion when no slag is present on the steel surface, as can be expected. It was also observed that the oxygen activity is higher in the lower measurement position than in the upper during the majority of the ladle refining. This is explained by the oxygen activity's temperature dependence. By using the data from this study and previously reported plant trials it was shown that Si-SiO2 or Al-Al2O3 equilibrium controls the oxygen activity.

Place, publisher, year, edition, pages
2008. Vol. 48, no 4, 438-445 p.
Keyword [en]
oxygen activity; temperature; steel; ladle; deoxidation; equilibrium
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-8122DOI: 10.2355/isijinternational.48.438ISI: 000255321600008Scopus ID: 2-s2.0-46749107601OAI: oai:DiVA.org:kth-8122DiVA: diva2:13359
Note

QC 20100708. Uppdaterad från accepted till published (20100708).

Available from: 2008-03-19 Created: 2008-03-19 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Thermodynamic Aspects on Inclusion Composition and Oxygen Activity during Ladle Treatment
Open this publication in new window or tab >>Thermodynamic Aspects on Inclusion Composition and Oxygen Activity during Ladle Treatment
2008 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Two industrial studies and one set of lab scale trials have been done. In addition, a theoretical study has been done. The main focus has been on non metallic inclusion composition during the ladle refining operation in industrial steel production. Sampling has been done together with careful inclusion determination. The inclusion composition is related to different variables. In the industrial trials samples have been taken at different steps during the ladle refining period. Steel and slag composition as well as temperature and oxygen activity have been determined.

The thesis is based on five supplements with different major objectives, all related to the inclusion composition. The equilibrium top slag-steel bulk and inclusions-steel bulk were investigated by comparison between calculated and measured oxygen activity values. The oxygen activity and relation to temperature has also been discussed as well as oxygen activity and temperature gradients. The effect of vacuum pressure on inclusion composition has been evaluated in a theoretical study as well as lab scale trials. The inclusion composition has been studied during the industrial ladle treatment process. The inclusion composition was related to top slag composition and other parameters during ladle treatment.

The major findings in the thesis are the lack of equilibrium conditions with respect to top-slag and steel bulk before vacuum treatment. The inclusions have been found to be closer to equilibrium with the steel bulk. Al/Al2O3 equilibrium has been found to control the oxygen activity after Al-deoxidation. Evaluation of inclusion composition during the ladle refining has revealed that the majority of the inclusions showed a continuous composition change throughout the ladle refining process, from high Al2O3, via MgO-spinel to finally complex types rich in CaO and Al2O3. The final inclusion composition after vacuum treatment was found to be close to the top slag composition. Vacuum pressure has been found to have a theoretical effect on inclusion composition at very low pressures.

Place, publisher, year, edition, pages
Stockholm: KTH, 2008. xii, 68 p.
Keyword
Ladle treatment, thermodynamics, inclusions, steel, slag, equilibrium, ladle treatment, vacuum, oxide activity, oxygen activity.
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-4673 (URN)978-91-7178-904-4 (ISBN)
Public defence
2008-04-08, B3, Materialvetenskap, Brinellvägen 23, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20100712Available from: 2008-03-19 Created: 2008-03-19 Last updated: 2010-07-12Bibliographically approved

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