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Comparison between measured CaO and Al2O3 normalised to CaO-Al2O3 in top slag, calcium aluminate inclusions, and results of theoretical calculations
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
(Materials Research and Development, Ovako Hofors AB)
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.ORCID iD: 0000-0001-5031-919X
2013 (English)In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 40, no 5, 369-375 p.Article in journal (Refereed) Published
Abstract [en]

This study sets out to compare the wt-% CaOslag and Al 2O3 slag in the binary system of CaO-Al 2O3 that were measured in the top slag before teeming, the CaOincl and Al2O3 incl in calcium aluminates that were analysed by scanning electron microscopy of the steel samples and the CaOcalc and Al2Ocalc 3 that were achieved from theoretical calculations using the total measured elements in the top slag and steel before teeming. The CaO incl and Al2O3 incl in all of the calcium aluminate inclusions of this study did not have the same ratio; in the opposite, they covered a large range. The average CaOincl and Al 2O3 incl in all samples had nearly similar compositions that were close to the border of the phase Ca12Al 14O33 in the binary phase diagram of CaO-Al 2O3. The CaOslag and Al2O 3 slag in all samples had almost similar compositions that were close to the border of the phase Ca3Al2O6 in the binary phase diagram of CaO-Al2O3. The results of theoretical calculations were close to the CaOslag and Al 2O3 slag, but they did not follow the same maximum and minimum tendencies of CaOslag and Al2O 3 slag.

Place, publisher, year, edition, pages
UK, 2013. Vol. 40, no 5, 369-375 p.
Keyword [en]
CaO, Al2O3, Top slag, Calcium aluminate, Inclusions, Theoretical calculations
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-101467DOI: 10.1179/1743281212Y.0000000046ISI: 000320448900007Scopus ID: 2-s2.0-84880640021OAI: oai:DiVA.org:kth-101467DiVA: diva2:547858
Note

QC 20150629

Available from: 2012-08-29 Created: 2012-08-29 Last updated: 2017-12-07Bibliographically approved
In thesis
1. Slag, Steel, Ladle and Non-metallic Inclusions Equilibria in an ASEA-SKF Ladle Furnace
Open this publication in new window or tab >>Slag, Steel, Ladle and Non-metallic Inclusions Equilibria in an ASEA-SKF Ladle Furnace
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This study explores the possibility of prediction and modification of some of the physicochemical properties of non-metallic inclusions by considering top slag-steel-ladle equilibria in an ASEA-SKF ladle furnace. To test the reliability of an available computational thermodynamic computer program, the first sub project was done. It was concluded that LiMeS, an interface for Thermo-Calc, is a useful tool for slag-steel equilibrium calculations. The second sub project was set out to find some model/s that could calculate the most accurate oxygen activity of molten steel compared to the measured one. This study concluded that both Wagner’s and Turkdogan's equations are useful. It was further seen that increasing the Al contents in the molten steel, increasing the CaO/Al2O3 ratio in the top slag, and reducing the temperature, resulted in reduction of the oxygen activity of the molten steel. In the third sub project a comparison was made between measured CaO and Al2O3 (normalised to CaO-Al2O3) in top slag, calcium aluminate inclusions, and the results of theoretical calculations. The average contents of CaO and Al2O3 in all inclusions were close to the composition of the phase Ca12Al14O33 and the contents of CaO and Al2O3 in the slags were close to the composition of the phase Ca3Al2O6 in the binary phase diagram of CaO-Al2O3. The forth sub project set out to study the effect of vacuum degassing time on non-metallic inclusions. It was concluded that during the vacuum degassing process the share of calcium aluminates compared to spinels, Ca content of the oxides, and the average equivalent circle diameters of the oxides were increasing, and oxides tended to form spherical shapes. Finally, based on the preceding four sub projects, the fifth sub project aimed to optimize the steel treatment in an ASEA-SKF ladle furnace. The final results showed that by adding 200 kg fluorite to the top slag of 1200 kg, it was possible to achieve a sulphur content of less than 10 ppm in the steel and a sulphur ratio between slag and steel of 1570, and at the same time reduce the oxygen activity of the molten steel and the degassing time.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. xiv, 62 p.
Keyword
Clean steel, Top slag, Non-Metallic Inclusions, Oxides, Vacuum Degassing, Deoxidation, Desulphurization, Equilibrium, Computational Thermodynamics, Scanning electron microscopy
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-102149 (URN)978-91-7501-489-0 (ISBN)
Public defence
2012-10-05, sal B2,, Brinellvägen 23, KTH, Stockholm, 13:15 (English)
Opponent
Supervisors
Note

QC 20120917

Available from: 2012-09-17 Created: 2012-09-10 Last updated: 2012-09-18Bibliographically approved

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Selleby, Malin

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