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Relationship between motion of bubbles and agglomeration of inclusions into clusters during solidification of continuously cast steel
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Casting of Metals.ORCID iD: 0000-0001-6477-5487
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The possibility of cluster formation during solidication of steel is explored to explain structures that are seen on the fracture surface of the steel. A hypothesis is built that postulates porosities provide favourable locations for inclusions to agglomerate and form clusters.  A thermodynamic model is constructed to describe precipitation of porosity and inclusions. Formation of inclusions follow a nucleation and growth mechanism. Porosities on the other hand are the product of pressure balance in the liquid.  Motion of pores and inclusions is analysed based on the drag force and  surface  stresses. Gradient of surface tension is also identied as a driving force which acts on the pore surface and would cause motion. It is shown that relative motion of pores and inclusions coupled with  the inclusion tendency to get attached on pore surface makes or a viable mechanism explaining agglomeration of inclusion particles to clusters

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. , 38 p.
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-174077ISBN: 978-91-7595-685-5 (print)OAI: oai:DiVA.org:kth-174077DiVA: diva2:857589
Presentation
2015-10-09, Sal M131 Sefström, Brinellvägen 23, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20150930

Available from: 2015-09-30 Created: 2015-09-29 Last updated: 2015-12-15Bibliographically approved
List of papers
1. On the Relationship Between Inclusions and Pores, Part I: Precipitation
Open this publication in new window or tab >>On the Relationship Between Inclusions and Pores, Part I: Precipitation
2012 (English)In: Transactions of the Indian Institute of Metals, ISSN 0972-2815, Vol. 65, no 6, 791-794 p.Article in journal (Refereed) Published
Abstract [en]

Formation mechanism and clustering of TiN-Al2O3 inclusions precipitated during solidification of austenitic stainless steel is analyzed in this paper. Steel sample are taken from a continuously cast bloom. Clustering of inclusions was examined with a hypothesis that inclusions gather inside the pores. Precipitation of the inclusions occurs through segregation in the residual melt in the interdendritic area. Size and mean distance of the inclusion particles are calculated with mass balance. Impact fracture test in cryogenic temperature reveals clusters of inclusions inside pores on the fracture surface. Size and distribution of the inclusions are examined using light optical microscopy and scanning electron microscopy. Inclusion's composition is investigated with energy dispersive X-ray spectroscopy analysis. Differential thermal analysis and differential scanning calorimetry Tests determined the transformation temperatures. Results of the experiments are in good agreement with theoretical analysis.

Keyword
Solidification, Inclusions, Steel, Nucleation, Cluster
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-107066 (URN)10.1007/s12666-012-0224-8 (DOI)000310461100049 ()2-s2.0-84897098067 (Scopus ID)
Note

QC 20150630

Available from: 2012-12-07 Created: 2012-12-06 Last updated: 2015-09-30Bibliographically approved
2. On the relationship between inclusions and pores, Part II: Dendritic structure, pressure drop in the liquid and pore precipitation
Open this publication in new window or tab >>On the relationship between inclusions and pores, Part II: Dendritic structure, pressure drop in the liquid and pore precipitation
2014 (English)In: 6th International Conference on Solidification and Gravity, 2014, Vol. 790-791, 302-307 p.Conference paper, Published paper (Refereed)
Abstract [en]

There is a relationship between pores and inclusions. Inclusions and pores are both formed during solidification inside the interdendritic melt. As hypothesis goes, porosity moves to absorb inclusions and form clusters. Focus of this paper is how solidified dendritic structure affects pore precipitation in austenitic stainless steel. Steel sample is a continuously cast bloom. Temperature profile and width of the mushy zone of the strand is modeled according to a constant temperature at the strands surface. Thermal analysis has been performed with differential thermal analysis (DTA) and differential scanning calorimeter (DSC). Primary dendrite arm spacing (PDAS) is measured with light optical microscopy (LOM) and scanning electron microscopy (SEM). PDAS is represented as the weight average of the distance between parallel sets of primary dendrite stems. Pressure field is calculated based on Darcy's law. Pore formation is described through segregation of the gas components and pressure field in the liquid.

Series
6th International Conference on Solidification and Gravity, ISSN 0255-5476
Keyword
Porosity, Pressure, Segregation, Solidification, Surface, Austenitic stainless steel, Continuous casting, Differential scanning calorimetry, Differential thermal analysis, Liquids, Scanning electron microscopy, Segregation (metallography), Surfaces, Constant temperature, Dendritic structures, Differential scanning calorimeters, Differential thermal analyses (DTA), Light optical microscopies, Primary dendrite, Primary dendrite arm spacings, Temperature profiles, Surface segregation
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-167554 (URN)10.4028/www.scientific.net/MSF.790-791.302 (DOI)2-s2.0-84901408673 (Scopus ID)9783038350934 (ISBN)
Conference
2 September 2013 through 5 September 2013, Miskolc, Lillafured
Note

QC 20150608

Available from: 2015-06-08 Created: 2015-05-22 Last updated: 2015-09-30Bibliographically approved
3. Pores and clustering of inclusions in the continuous casting of steel: Precipitation
Open this publication in new window or tab >>Pores and clustering of inclusions in the continuous casting of steel: Precipitation
(English)Manuscript (preprint) (Other academic)
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-174087 (URN)
Note

QS 2015

Available from: 2015-09-30 Created: 2015-09-30 Last updated: 2015-09-30Bibliographically approved

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Safavi Nick, Arash

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