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A study of slag-steel-inclusion interaction during Ladle treatment
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
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 [en]
Ladle treatment, steel, slag, inclusions, ladle, refining, vacuum, tool steel, oxide activity, slag models, oxygen, equilibrium
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-4018ISBN: 91-7178-403-9 (print)OAI: oai:DiVA.org:kth-4018DiVA: diva2:10404
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
List of papers
1. Equilibrium between slag, steel and inclusions during ladle treatment: comparison with production data
Open this publication in new window or tab >>Equilibrium between slag, steel and inclusions during ladle treatment: comparison with production data
2007 (English)In: Ironmaking & steelmaking, ISSN 0301-9233, Vol. 34, no 4, 312-324 p.Article in journal (Refereed) Published
Abstract [en]

The primary purpose of the investigation was to determine whether equilibrium conditions exist between slag and steel and inclusions and steel after silicon deoxidation and aluminium deoxidation. In doing so, the performance of three different models for predicting oxide component activities was also evaluated. The results from the oxide activity models were used to calculate oxygen activities in the steel melt. Industrial data such as steel, slag and inclusion component concentrations, as well as temperature, were used as input to the calculations. One general conclusion drawn was that although the results from the different models showed similar trends, the models did not predict the same actual values for specific calculations. Predicted theoretical equilibrium oxygen activity values were compared with plant measurements of oxygen activity. Here, it was found that the oxygen activity values pertaining to the equilibrium between steel and inclusions were higher than corresponding measured values. The calculations for the equilibrium between the top slag and steel melt, however, resulted in theoretical oxygen activity values considerably lower than corresponding measurements. It was thus concluded that equilibrium conditions did not exist between the top slag and the steel bulk with respect to oxygen. Overall, the models proved useful in predicting oxide activities, but the lack of equilibrium between top slag and molten steel made the calculation of oxygen activity difficult.

Keyword
models; activity; slag; steel; oxygen; oxide; SLAGS
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-8120 (URN)10.1179/174328107X168039 (DOI)000248541700006 ()2-s2.0-35348944450 (Scopus ID)
Note
QC 20100707Available from: 2008-03-19 Created: 2008-03-19 Last updated: 2010-07-07Bibliographically approved
2. The Effect of Ladle Treatment on Inclusion Composition in Tool Steel Production
Open this publication in new window or tab >>The Effect of Ladle Treatment on Inclusion Composition in Tool Steel Production
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.

Keyword
inclusions; composition; ladle; refining; tool steel; vacuum
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-8121 (URN)10.1002/srin.200806350 (DOI)000256177900003 ()2-s2.0-43749110004 (Scopus ID)
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

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