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Modeling micro-inclusion growth and separation in gas-stirred ladles
KTH, Superseded Departments, Materials Science and Engineering.
KTH, Superseded Departments, Materials Science and Engineering.
2002 (English)In: Scandinavian journal of metallurgy, ISSN 0371-0459, Vol. 31, no 2, 134-147 p.Article in journal (Refereed) Published
Abstract [en]

Mathematical models of inclusion behavior in stirred ladles are useful both for increasing our fundamental understanding of the growth and removal of inclusions as well as for future use in process control. This study reports on some efforts to use both static and dynamic modeling to better understand inclusion behavior in gas-stirred ladles. A computational-fluid-dynamics mathematical model of a gas-stirred ladle was developed earlier. In the investigation covered in this report, instantaneous fluid-flow results from the model were used in combination with inclusion growth and removal theories in order to study the importance of bubbles on inclusion flotation. The study results proved to be highly dependent on the theory used to describe bubble flotation. The model of the gas-stirred ladle was also used together with the inclusion theories to study the transient behavior of inclusions during growth and removal. The dynamic simulation results indicated that inclusion concentration gradients exist. The most important research task in the near future is to verify static and dynamic modeling results of inclusion behavior during stirring with experimental data. Here, the authors feel that carefully performed plant trials could provide useful information.

Place, publisher, year, edition, pages
2002. Vol. 31, no 2, 134-147 p.
Keyword [en]
gas-stirring, inclusions, ladle, modeling, secondary refining
National Category
Metallurgy and Metallic Materials
URN: urn:nbn:se:kth:diva-7512DOI: 10.1034/j.1600-0692.2002.310208.xISI: 000175885700008OAI: diva2:12560

QC 20110921

Available from: 2004-11-15 Created: 2004-11-15 Last updated: 2013-02-27Bibliographically approved
In thesis
1. Growth and removal of inclusions during ladle refining
Open this publication in new window or tab >>Growth and removal of inclusions during ladle refining
2004 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The overall purpose of this thesis work has been to further our understanding of the growth and removal of inclusions in gas- and induction-stirred ladles. The primary focus has been on alumina inclusions.

Growth mechanisms were studied using data from fundamental mathematical models of gas- and induction-stirred ladles. The results showed the turbulence mechanism to be the most dominant in alumina inclusion growth. The dynamic growth and removal of inclusions in a gas-stirred ladle was studied using mathematical modelling. The model results showed concentration gradients of inclusions. The effect was most obvious in the steel flow past the removal sites: top slag, ladle refractory, and gas plume (bubble flotation). A new removal model was developed for large spherical caps bubbles.

In order to verify the predicted concentration gradients for the size population of inclusions, three experiments were carried out in production. The sampling equipment enabled sampling at five different positions and different locations at the same time. The results showed that concentration gradients of inclusions do exist both in induction-stirred and gas-stirred ladles. A theoretical analysis showed that the drag force on the inclusions to be the dominating force and that therefore inclusions follow the fluid flow.

The cluster behaviour of alumina inclusions were examined on steel samples taken in an industrial-scale deoxidation experiment in a ladle. The samples were examined by microscope and the results used to study cluster growth. It was found that there was rapid cluster growth due to collision during stirring and that at the end of the deoxidation experiment a majority of the small inclusions were bound in clusters. The cluster growth data determined using the microscopic results were compared with predicted cluster-growth data. A method was developed for converting the experimental data observed per unit area into data given per unit volume and vice versa. An expression for the collision diameter of the cluster was also developed. The results showed that the predicted cluster growth agreed well with the microscopic observations for the assumptions made in the growth model.

Place, publisher, year, edition, pages
Stockholm: Materialvetenskap, 2004
Meteorology, inclusions, steel, ladle, cluster growth, modelling, Meteorologi
National Category
Meteorology and Atmospheric Sciences
urn:nbn:se:kth:diva-45 (URN)91-7283-886-8 (ISBN)
Public defence
2004-11-15, B3, KTH, Brinellvägen 23, Stockholm, 10:00
Available from: 2004-11-15 Created: 2004-11-15 Last updated: 2014-03-20

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Söder, MatsJönsson, PärJonsson, Lage
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