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
A Mathematical and Experimental Study of Inclusion Behaviour at a Steel-Slag Interface
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
2007 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The aim of this thesis work is to increase the knowledge of inclusion behavior at the steel-slag interface by mathematical modeling and in-situ Confocal Scanning Laser Microscope experiments. Mathematical models based on the equation of motion predicting liquid and solid inclusion behavior was first investigated. Four main forces, the buoyancy force, the added mass force, the rebound force and the drag force, act on the inclusion as it crosses the interface. There are three types of behavior an inclusion at the steel-slag interface can adopt. These are a) pass, which means that the inclusion is separated to the slag, b) remain, where the inclusion stays at the interface without being fully transferred to the slag or c) oscillate, and the inclusion rises and descends at the interface until the motion is dampened out by the interfacial forces. The studies showed the importance of accurate experimental physical property data. Application of the models to industrial conditions illustrated that useful plots could be made showing the industry how to optimize their interfacial properties in the ladle and tundish to obtain maximum inclusion separation.

In-situ Confocal Scanning Laser Microscope (CSLM) experiments were carried out in order to study agglomeration of liquid and semi liquid inclusions at the steel-gas and steel-slag interfaces and in the slag. Liquid-liquid inclusion agglomeration at steel-gas and steel-slag interfaces was seen to not occur without using force. However, when already transferred to the slag the inclusions agglomerated freely due to a higher free energy force. Comparison of experimental and theoretical agglomeration force showed good agreement between experiments and theory.

The main conclusion of this work is that inclusion separation is a complex field of study and there exist no model that takes everything into account. Here the tendency for inclusion transfer and how to manipulate the physical properties for inclusion separation together with agglomeration experiments have been studied. For the future maybe coupling of models for computational fluid dynamics, agglomeration, inclusion separation, dissolution and slag entrainment in addition with experimental physical property data can provide a better overview and understanding.

Place, publisher, year, edition, pages
Stockholm: KTH , 2007. , vii, 58 p.
Series
KTH/MSE, 2007:60
Keyword [en]
mathematical modeling, inclusion separation, tundish, ladle, slag, steel-slag interface, CSLM experiments, agglomeration, physical properties
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-4574ISBN: 978-91-7178-781-1 (print)OAI: oai:DiVA.org:kth-4574DiVA: diva2:12934
Public defence
2007-12-19, Sal B2, KTH, Brinellvägen 23, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20100823Available from: 2007-12-12 Created: 2007-12-12 Last updated: 2010-08-23Bibliographically approved
List of papers
1. Solid inclusion transfer at a steel-slag interface with focus on tundish conditions
Open this publication in new window or tab >>Solid inclusion transfer at a steel-slag interface with focus on tundish conditions
2005 (English)In: ISIJ International, ISSN 0915-1559, Vol. 45, no 11, 1597-1606 p.Article in journal (Refereed) Published
Abstract [en]

The separation of non-metallic inclusions from the steel to the slag phase in the ladle during secondary steel making operations and in the tundish and mold during casting is very crucial to the production of clean steel. In this work a theoretical study of the separation of solid inclusions, alumina and others, at the steelslag interface applied to the actual conditions in the tundish has been carried out. The theoretical model is based on the equation of motion with the following forces acting on an inclusion as it tries to cross the interface between the metal and the slag; buoyant, added mass, rebound and drag force. A sensitivity analysis study was carried out in order to clarify which of the parameters in the model that had the largest influence on the inclusion displacement. The results showed that the interfacial tensions (sigma(MI), sigma(IS), sigma(MS)) and the slag viscosity (us) have the largest influence on the predicted displacement. It was also concluded that the overall wettability should be positive and that the slag viscosity should be as low as possible to obtain the most favorable conditions for inclusion transfer at the steel-slag interface.

Keyword
Inclusions; Modeling; Physical properties and tundish; Slag; Steel; Transfer; Buoyancy; Drag; Ladle metallurgy; Slags; Steel; Surface tension; Interfaces (materials)
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-7800 (URN)10.2355/isijinternational.45.1597 (DOI)000233421700011 ()2-s2.0-31144438556 (Scopus ID)
Note
QC 20100823Available from: 2007-12-12 Created: 2007-12-12 Last updated: 2012-03-21Bibliographically approved
2. A mathematical model to study liquid inclusion behavior at the steel-slag interface
Open this publication in new window or tab >>A mathematical model to study liquid inclusion behavior at the steel-slag interface
2005 (English)In: ISIJ International, ISSN 0915-1559, Vol. 45, no 12, 1838-1847 p.Article in journal (Refereed) Published
Abstract [en]

The separation of non-metallic inclusions at the interface between the steel and the slag in the ladle, tundish and mold is an essential part of the production of clean steel. It is therefore, of great importance to have a deep understanding of the phenomena controlling the transfer of inclusions from the steel to the slag layer. In this work a mathematical model, derived from the equation of particle motion, have been used to study the transfer of liquid inclusions to slags. The effects of the drag, added mass, buoyancy and rebound force on the inclusion transfer are considered. The model relies, to a great extent, on the availability of accurate information of the magnitude of a number of physical properties of the involved phases. Among those properties, the interfacial tension between the phases and the slag viscosity were found to be the most critical. Due to the fact that the availability of experimentally obtained high-temperature physical property data, relevant to the industrial conditions, is scarce in the literature several different model descriptions have been used in this work to estimate these properties. The mathematical model has been used to investigate the separation of liquid non-metallic inclusions, of different size and composition, to a number of different industrial ladle slag compositions.

Keyword
Mathematical model; Non-metallic incluions; Physicl properties; Steel making; Buoyancy; Interfaces (materials); Liquids; Slags; Steelmaking; Model descriptions; Non-metallic incluions; Physicl properties; Non-metallic incluions; Physicl properties Engineering main heading:
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-7801 (URN)10.2355/isijinternational.45.1838 (DOI)000234202600009 ()2-s2.0-33244489368 (Scopus ID)
Note
QC 20100823Available from: 2007-12-12 Created: 2007-12-12 Last updated: 2012-03-21Bibliographically approved
3. In situ studies of agglomeration between Al2O3-CaO inclusions at metal/gas, metal/slag interfaces and in slag
Open this publication in new window or tab >>In situ studies of agglomeration between Al2O3-CaO inclusions at metal/gas, metal/slag interfaces and in slag
Show others...
2008 (English)In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 35, no 8, 589-599 p.Article in journal (Refereed) Published
Abstract [en]

Studies of inclusion behaviour at the metal/slag interface is of great importance for the steel industry in order to achieve better control of both the size and amount of the inclusions, as well as improving the steel quality and the casting process. In this work agglomeration of liquid Al2O3-CaO particles at both steel/argon gas and steel/slag interfaces was studied with a confocal scanning laser microscope. In addition, agglomeration of liquid Al2O3-CaO-SiO2 inclusions present in the slag was investigated. The results showed that liquid inclusions more easily agglomerated to semiliquid inclusions than to liquid inclusions. Moreover, the agglomeration of liquid particles was found to be improved remarkably when the particles were present in the slag compared to when they were in the steel/slag interface.

Keyword
Inclusions, Agglomeration, Metal/slag interface, In situ experiments, Capillary force, multicomponent silicate melts, low-carbon steels, killed steels, particles, surface, dissolution, behavior, tension, alloys, time
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-18053 (URN)10.1179/174328108x284589 (DOI)000261735800004 ()2-s2.0-55849118773 (Scopus ID)
Note
QC 20100823Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
4. Application of a model for liquid inclusion separation at a steel-slag interface for laboratory and industrial situations
Open this publication in new window or tab >>Application of a model for liquid inclusion separation at a steel-slag interface for laboratory and industrial situations
2008 (English)In: Steel Research International, ISSN 1611-3683, Vol. 79, no 11, 826-834 p.Article in journal (Refereed) Published
Abstract [en]

A mathematical model based on the equations of particle motion was used to predict inclusion behavior observed at steel-slag interface in an in-situ Confocal Scanning Laser Microscope. The results show that the model can be used to explain some phenomena observed in the experiments. In addition, a parameter study was done in order to illustrate how the model can be used to study the effect of physical properties on the inclusion behavior at the slag-steel interface for some typical industrial ladle metallurgy conditions. Furthermore, to study the effect of steel temperature, sulfur and oxygen content in the steel, slag and inclusion density as well as initial inclusion velocity on the inclusions behavior at the slag-steel interface. The results show that the temperature and initial velocity was of less importance and that the oxygen content in the steel had a larger influence on the inclusion behavior than the sulfur content in the steel.

Keyword
CSLM experiments; Ladle refining; Mathematical model; Non-metallic inclusions; Physical properties; Equations of motion; Inclusions; Ladle metallurgy; Ladles; Mathematical models; Oxygen; Slags; Steel; Steel research; Sulfur; Surface chemistry; Confocal scanning laser microscopes; CSLM experiments; In-situ; Inclusion behaviors; Inclusion densities; Initial velocities; Ladle refining; Liquid inclusions; Non-metallic inclusions; Oxygen contents; Parameter studies; Particle motions; Steel interfaces; Steel temperatures; Sulfur contents; Steel metallurgy
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-7803 (URN)10.2374/SRI08SP006 (DOI)000261160600004 ()2-s2.0-57049156122 (Scopus ID)
Note
QC 20100823Available from: 2007-12-12 Created: 2007-12-12 Last updated: 2010-08-23Bibliographically approved

Open Access in DiVA

fulltext(15108 kB)2694 downloads
File information
File name FULLTEXT01.pdfFile size 15108 kBChecksum MD5
22ed85411caf1bc4eb501d583301ea155aa6a45d4d659f9855563dea9011c1d45f90cece
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Wikström, Jenny
By organisation
Materials Science and Engineering
Metallurgy and Metallic Materials

Search outside of DiVA

GoogleGoogle Scholar
Total: 2694 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: 774 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