Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Formation of Inclusions and their Development during Secondary Steelmaking
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Al–O relations in iron were investigated. Pure iron with varying Al content was equilibrated at 1873 K. The oxygen content of iron with higher Al content than 1.0 mass % was found to be much lower than previous works, while the oxygen content for Al content less than 1 mass% was found to be slightly higher. Further, a classification procedure of inclusions was developed using the commercial software INCA Feature. Three classes were made, spinel, TP-(CaO-Al2O3), and (CaO-Al2O3) class, corresponding to the inclusions found during degassing at Uddeholm Tooling. The results showed that the spinel phase disappeared after degassing along with a reduction in numbers for the two phase inclusion (TP-(CaO-Al2O3)). Pure calcium aluminates however showed an increasing trend in a majority of the heats. The chemical development of inclusions at OVAKO Steel in Hofors, Sweden was also established. According to the morphologies and compositions, the inclusions were classified into 5 different types, namely, (1) alumina inclusions, (2) calcium aluminate, (3) spinel+calcium aluminate, (4) calcium aluminate surrounded by a CaS shell, and (5) spinel+calcium aluminate surrounded by a CaS shell. Thereafter refractory lining samples with attached slag layer were taken from used ladles at the two steel plants. The morphologies of the slag layers and the phases present were examined. The precipitated phases found in the refractory were 3CaO.Al2O3, MgO.Al2O3 and CaO in the case of Ovako Steel and 3CaO.Al2O3 and 2CaO.SiO2 in the case of Uddeholm Tooling. To help the understanding, model calculations using THERMOCALC were carried out. The model predictions differed somewhat from the experimental observation, the predicted major phases were in line with the EDS analysis on the refractory samples. Finally experiments were carried out to study the slag entrainment related to the open-eye during ladle treatment. Ga-In-Sn alloy was used to simulate the liquid steel, while MgCl2-Glycerol(87%) solution was used to simulate the ladle slag. No noticeable amount of top liquid was observed in any of the samples taken from the metal bulk during gas stirring. To confirm this aspect, slag-metal interface samples were taken from an industrial gas stirred steel ladle. No entrapment was found in the steel. The accordance of the laboratory and industrial results suggests that the entrainment of slag into the steel bulk around the open-eye cannot be considered as the major contribution to inclusion formation.

Place, publisher, year, edition, pages
Stockholm: KTH , 2009. , xi, 38 p.
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-10420ISBN: 978-91-7415-276-0 (print)OAI: oai:DiVA.org:kth-10420DiVA: diva2:217063
Public defence
2009-04-24, Sal F3, KTH, Lindstedtsvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20100812Available from: 2009-05-13 Created: 2009-05-13 Last updated: 2010-08-12Bibliographically approved
List of papers
1. Aluminum Deoxidation Equilibrium of Molten Iron-Aluminum Alloy with Wide Aluminum Composition Range at 1873 K
Open this publication in new window or tab >>Aluminum Deoxidation Equilibrium of Molten Iron-Aluminum Alloy with Wide Aluminum Composition Range at 1873 K
Show others...
2009 (English)In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 49, no 10, 1483-1489 p.Article in journal (Refereed) Published
Abstract [en]

Al-0 equilibria in molten Fe-Al alloys were experimentally investigated. Molten steel with varying Al content (0.01-10 mass%) was equilibrated with a pure Al2O3(S) crucible at 1873 K in an Ar atmosphere with 3 vol% H-2, The oxygen content of steel with Al content higher than 1.0 mass% was found to be much lower than that found in previous works, while the oxygen content for Al content less than I mass% was found to be slightly higher, resulting in a smaller equilibrium constant. The interaction parameters as well as the equilibrium constant of the Al-O equilibria in molten steel at 1 873 K were reevaluated in the present study. The equilibrium for the Al deoxidation of molten steel was well represented up to 10.0 mass% Al using the reevaluated parameters.

Keyword
deoxidation; aluminum; equilibrium constant; interaction parameters
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-24058 (URN)000271176100004 ()2-s2.0-73949144089 (Scopus ID)
Note
QC 20100812Available from: 2010-08-12 Created: 2010-08-12 Last updated: 2017-12-12Bibliographically approved
2. Identification of inclusions using the results of INCA feature analysis and its application on the inclusions found in ladle treatment
Open this publication in new window or tab >>Identification of inclusions using the results of INCA feature analysis and its application on the inclusions found in ladle treatment
(English)In: Steel Grips - Journal of Steel and Related Materials, ISSN 1611-4442, E-ISSN 1866-8453Article in journal (Other academic) Submitted
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-24062 (URN)
Note
QC 20100812Available from: 2010-08-12 Created: 2010-08-12 Last updated: 2017-12-12Bibliographically approved
3. Origins of non-metallic inclusions and their chemical development during ladle treatment
Open this publication in new window or tab >>Origins of non-metallic inclusions and their chemical development during ladle treatment
2008 (English)In: STEEL RESEARCH INTERNATIONAL, ISSN 1611-3683, Vol. 79, no 2, 124-132 p.Article in journal (Refereed) Published
Abstract [en]

In the present work, steel, slag and refractory samples were taken from the ladle at OVAKO Steel in Hofors, Sweden. The steel samples were analysed in LOM, SEM and OES PDA. The chemical compositions of the inclusions were determined by EDS. According to the morphologies and compositions, the inclusions were classified into 5 different types, namely, (1) type-1, alumina inclusions, (2) type-2, calcium aluminate, (3) type-3, spinel+calcium aluminate, (4) type-4, calcium aluminate surrounded by a CaS shell, and (5) spinel+calcium aluminate surrounded by a CaS shell. Ladle glaze was found to be a major supplier of the inclusions, while the inclusions brought over from EAF could be another important source. The results of OES PDA showed that removal of inclusions took place mostly during the vacuum degassing period.

Keyword
inclusions, bearing steel, ladle glaze
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-17394 (URN)10.2374/sri07sp081-79-2008-124-132 (DOI)000254195800009 ()2-s2.0-39749138910 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2011-01-17Bibliographically approved
4. Slag‐refractory reaction during ladle refining and teeming
Open this publication in new window or tab >>Slag‐refractory reaction during ladle refining and teeming
2009 (English)In: Steel Grips - Journal of Steel and Related Materials, ISSN 1611-4442, E-ISSN 1866-8453, Vol. 7, no 2, 129-135 p.Article in journal (Other academic) Published
Abstract [en]

Refractory lining samples with slag layer were taken from used ladles at two steel plants, Ovako Steel and Uddeholm Tooling. The morphologies of the slag layers and the phases present were examined. The appearances and phases of the glaze layers were found to be somewhat different in the ladles from the two steel plants. The precipitated phases found in the refractory were 3CaO-Al2O3, MgO-Al2O3 and CaO in the case of Ovako Steel, and 3CaO-Al2O3 and 2CaO-SiO2 in the case of Uddeholm Tooling. To help the understanding, model calculations using commercial software Thermocalc were carried out. Although the model predictions differed somewhat from the experimental observation, the predicted major phases were in line with the EDS analysis on the refractory samples. Cold model study using both water and Ga-In-Sn alloy to simulate liquid steel were also performed. The results would be able to explain the thick slag line of the ladle and the serious erosion even far below the slag line. Both the slag line and the glaze layer below the slag line would be a potential source of non-metallic inclusions.

Keyword
Inclusions, refractory, ladle glaze, morphology, cold model
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-24063 (URN)10.5161/steel/2009/g02288 (DOI)
Note
QC 20100812. QC 20120130Available from: 2010-08-12 Created: 2010-08-12 Last updated: 2017-12-12Bibliographically approved
5. Study on the formation of open-eye and slag entrainment in gas stirred ladle
Open this publication in new window or tab >>Study on the formation of open-eye and slag entrainment in gas stirred ladle
Show others...
2007 (English)In: Steel Research International, ISSN 1611-3683, Vol. 78, no 12, 849-856 p.Article in journal (Refereed) Published
Abstract [en]

Laboratory experiments were carried out to study the phenomena related to open-eye formation in ladle treatment. Ga-In-Sn alloy with a melting temperature of 283 K was used to simulate the liquid steel, while MgCl2-Glycerol(87%) solution as well as HCl solution were used to simulate the ladle slag. No open-eye was formed at lower gas flow rates, but, occurred when gas flow reached a critical rate. This critical gas flow rate was found to depend significantly on the height of the top liquid. No noticeable amount of top liquid was observed in any of the samples taken from the metal bulk during gas stirring. To confirm this aspect, samples of slag-metal interface were taken around the open-eye in an industrial gas stirred steel ladle. No entrapped slag droplet was found in the solidified steel within the region between the interface and 2 cm from the interface. The accordance of the laboratory and industrial results suggests that the entrainment of slag into the steel bulk around the open-eye cannot be considered as the major contribution to inclusion formation.

Keyword
cold model, inclusion, slag entrapment, Ga-In-Sn alloy, open-eye, steel-slag interface
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-17211 (URN)000252709300002 ()2-s2.0-38049165244 (Scopus ID)
Note
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2010-08-12Bibliographically approved

Open Access in DiVA

fulltext(2108 kB)2689 downloads
File information
File name FULLTEXT01.pdfFile size 2108 kBChecksum SHA-512
fe323f978da8a89b78f5576f931e926ae74c97f1155c8a243eea4addece2d26d70cff1236a4dc2e2271fc606a5050c87f6a9d6bcb04a6f8724a0375329ec5af4
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Thunman, Mikael
By organisation
Materials Science and Engineering
Metallurgy and Metallic Materials

Search outside of DiVA

GoogleGoogle Scholar
Total: 2689 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 830 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf