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The Effect of Ladle Treatment on Inclusion Composition in Tool Steel Production
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
Uddeholm Tooling AB.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
2008 (English)In: Steel Research International, ISSN 1611-3683, Vol. 79, no 4, 261-270 p.Article in journal (Refereed) Published
Abstract [en]

An in-depth SEM-investigation of the inclusion composition change in the ladle refining process during tool steel production was done. Plant trials were carried out at Uddeholm Tooling AB in Hagfors, Sweden. A series of samples was taken during ladle refining, from deslagging through vacuum treatment. The goal was evaluating the effects of the top slag and other process parameters on the inclusion composition during ladle refining. The main conclusion was that normal variations in the process have a large influence on inclusion composition. Furthermore, it was concluded that the MgO content in the top slag had a large influence on the inclusion, composition throughout the whole ladle refining process. Also, the SiO2 content in the ladle slag originating from the EAF-slag, had a noticeable effect on the inclusions. The inclusions belonging to the system Al2O3-CaO-MgO-SiO2 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.

Place, publisher, year, edition, pages
2008. Vol. 79, no 4, 261-270 p.
Keyword [en]
inclusions; composition; ladle; refining; tool steel; vacuum
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-8121DOI: 10.1002/srin.200806350ISI: 000256177900003Scopus ID: 2-s2.0-43749110004OAI: oai:DiVA.org:kth-8121DiVA: diva2:13358
Note

QC 20100712. Uppdaterad från in press till published 20100712.

Available from: 2008-03-19 Created: 2008-03-19 Last updated: 2017-06-14Bibliographically 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
2. A study of slag-steel-inclusion interaction during Ladle treatment
Open this publication in new window or tab >>A study of slag-steel-inclusion interaction during Ladle treatment
2006 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

The thesis is based on two supplements with two major objectives. In the first supplement equilibrium top slag-steel bulk and inclusions-steel bulk were investigated by comparison between calculated and measured oxygen activity values. This was done by applying different oxide activity models for slags combined with thermodynamic calculations. In the second supplement the inclusion composition is studied during the ladle refining process. The inclusion composition is related to top slag composition and other parameters during ladle

treatment.

The work was carried out by collecting data during well controlled sampling procedures at two different steel plants. Extensive inclusion analyses in Scanning Electron Microscope, SEM, were done. The data was used together with thermodynamics for a description of the interaction between slag-steel-inclusion interaction during ladle treatment.

Evaluation of inclusion composition during the ladle refining have revealed that the majority of the inclusions belonged to the system Al2O3-CaO-MgO-SiO2 and 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 composition after vacuum treatment was found to be close to the top slag composition. Small process parameter changes and practical variations during ladle refining were proven to give large differences of the inclusion composition.

Finally, it was concluded that equilibrium does not exist between top slag and steel bulk, with respect to oxygen, for the studied conditions. However, the equilibrium does exist between the steel bulk and inclusion.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006. x, 28 p.
Series
ISRN KTH/MSE--06/46--SE+APRMETU/AVH
Keyword
Ladle treatment, steel, slag, inclusions, ladle, refining, vacuum, tool steel, oxide activity, slag models, oxygen, equilibrium
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-4018 (URN)91-7178-403-9 (ISBN)
Presentation
2006-06-15, B2, Materialteknik, Brinellvägen 23, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20101109Available from: 2006-06-01 Created: 2006-06-01 Last updated: 2010-11-09Bibliographically approved

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