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The Influence of Vacuum Treatment on Inclusion Composition: Theoretical Study
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.
2010 (English)In: High Temperature Materials and Processes, ISSN 0334-6455, E-ISSN 2191-0324, Vol. 29, no 3, 179-187 p.Article in journal (Refereed) Published
Abstract [en]

A theoretical study has been conducted into how inclusion composition is influenced by vacuum treatment. Software for computational thermodynamics has been used to simulate how the conditions in a steel melt changed as a result of a decreased pressure. A case study was made on a low sulphur bearing steel (1.4% Cr, 1.0%C). The calculations show the effect of sulphur, oxygen, carbon and temperature on precipitated phases in the steel melt. The result shows that at low pressure, formation of carbon monoxide takes place. For 5 ppm O and 10 ppm S the CO-gas becomes thermodynamically stable below 40 torr. Oxide phases will be reduced and CaS will be the stable phase.

Place, publisher, year, edition, pages
2010. Vol. 29, no 3, 179-187 p.
Keyword [en]
vacuum, inclusions, calcium aluminates
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-8123ISI: 000283965900007Scopus ID: 2-s2.0-78149246585OAI: oai:DiVA.org:kth-8123DiVA: diva2:13360
Note
QC 20100709. Uppdaterad från submitted till published (20101210). Tidigare submitted till Steel Research International, med titeln "The Influence of Vacuum Treatment on Inclusion Composition: Part 1: Theoretical Study".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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