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Densities and viscosities of slags: modeling and experimental investigations
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
2006 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

The present dissertation describes part of the efforts directed towards the development of computational tools to support process modeling. This work is also a further development of the Thermoslag software developed in the Division of Materials Process Science, KTH.

The essential parts of the thesis are

a) development of a semi-empirical model for the estimation of the molar volumes/densities of multicomponent slags with a view to incorporate the same in the model for viscosities and

b) further development of the viscosity model for application towards fluorid- containing slags, as for example, mould flux slags.

The model for the estimation of molar volume is based on a correlation between the relative integral molar volume of a slag system and the relative integral molar enthalpies of mixing of the same system. The integral molar enthalpies of the relevant systems could be evaluated from the Gibbs energy data available in the Thermoslag software. The binary parameters were evaluated from experimental measurements of the molar volumes. Satisfactory correlations were obtained in the case of the binary silicate and aluminate systems. The model was extended to ternary and multi component systems by computing the molar volumes using the binary parameters. The model predictions showed agreements with the molar volume data available in literature. The model was used to estimate the molar volumes of industrial slags as well as to trace the trends in molar volume due to compositional variations. The advantage of the present approach is that it would enable prediction of molar volumes of slags that are compatible with the thermodynamic data available.

With a view to extend the existing model for viscosities to F--containing slags, the viscosities of mould flux slags for continues casting in steel production have been investigated in the present work. The measurements were carried out utilizing the rotating cylinder method. Seven mould fluxes used in the Swedish steel industry and the impact of Al2O3 pick up by mould flux slags on viscosities were included in the study. The results showed that even relatively small additions of Al2O3 are related with a significant increase in viscosity

Place, publisher, year, edition, pages
Stockholm: KTH , 2006. , x, 58 p.
Series
ISRN KTH/MSE--06/23--SE+THMETU/AVH
Keyword [en]
density, nolar volume, thermodynamics, enthalpies, model, slags, oxide melts, viscosity, mould flux, continuous casting
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-3926ISBN: 91-7178-336-9 (print)OAI: oai:DiVA.org:kth-3926DiVA: diva2:10040
Presentation
2006-04-28, Sal B3, KTH, Brinellvägen 23, Stockholm, 14:00
Opponent
Supervisors
Note
QC 20101123Available from: 2006-04-27 Created: 2006-04-27 Last updated: 2010-11-23Bibliographically approved
List of papers
1. Estimation of molar volumes of some binary slags from enthalpies of mixings
Open this publication in new window or tab >>Estimation of molar volumes of some binary slags from enthalpies of mixings
2007 (English)In: Steel research, ISSN 0177-4832, Vol. 78, no 2, 102-108 p.Article in journal (Refereed) Published
Abstract [en]

In an effort to interlink the thermo chemical and thermo physical properties of slags, the present workwas undertaken to derive the molar volumes of complex slags from the enthalpies of mixing of thecorresponding slags. As a first step, binary systems of the following oxides were investigated; Al2O3,CaO, FeO, MgO, MnO, and SiO2. An empirical correlation was derived between the enthalpies ofmixing and molar volumes. A comparison of the computed results on the basis of the aboverelationship with the experimental data on molar volumes available in literature shows that theagreement between the calculated results and measured densities is satisfactory in the case of mostof the binary systems, within the limits of experimentally uncertainties. The advantage of the presentapproach is that it would enable prediction of molar volumes of slags that are compatible with thethermodynamic data available.

National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-5611 (URN)10.2374/SRI06SP102-78-2007-102 (DOI)
Note

QC 20100812. Uppdaterad från Submitted till Published.

Available from: 2006-04-27 Created: 2006-04-27 Last updated: 2016-12-19Bibliographically approved
2. A Thermodynamic Approach to a Density Model for Oxide Melts
Open this publication in new window or tab >>A Thermodynamic Approach to a Density Model for Oxide Melts
2007 (English)In: Steel research, ISSN 0177-4832, Vol. 78, no 4, 290-298 p.Article in journal (Refereed) Published
Abstract [en]

In an attempt to estimate the densities of complex slags, a model based on the thermodynamics ofslags developed earlier by the present authors is extended to ternary and multi-component systemsin the present work. The molar volumes of ternary and higher order systems were derived from therelative integral molar enthalpies of mixing of the corresponding slags. The higher order of slagsystems has been predicted by using the parameters from the related binary sub-systems, whichhave been evaluated earlier. Comparisons of calculated results with experimental data on molarvolumes available in literature show a satisfying agreement for a number of systems, within the limitsof experimental uncertainties. The model presents a promising method to compute the molar volumeof slag systems where no experimental data is available using the abundance of thermodynamicdata available. The model would also enable the generation of density data for slags containingAl2O3, CaO, FeO, MgO, MnO, and SiO2 compatible with the corresponding thermodynamic data.

Keyword
Density, Enthalpies, Model, Molar volume, Oxide melts, Slags, Thermodynamics
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-7110 (URN)10.2374/SRI06SP108-78-2007-290 (DOI)000246510800003 ()2-s2.0-34248138538 (Scopus ID)
Note
QC 20100812Available from: 2007-05-15 Created: 2007-05-15 Last updated: 2011-11-07Bibliographically approved
3. Viscosity Measurements of Some Mould Flux Slags
Open this publication in new window or tab >>Viscosity Measurements of Some Mould Flux Slags
2007 (English)In: ISIJ International, ISSN 0915-1559, Vol. 47, no 10, 1533-1540 p.Article in journal (Refereed) Published
Abstract [en]

Continuous casting has been the dominating process for steel casting over the past decades. During the process, mould fluxes are added to enable a smooth functioning of the process, enabling better process performance and products with less defects. The viscosity of the mould flux slag is a key parameter determining the optimum casting conditions.Several experimental studies have earlier been carried out in order to determine viscosity data for mould flux slags, both industrial ones as well as synthetic slags with compositions close to industrial mould fluxes. However, the continuous evolving of new steel grades, casting dimensions and product quality in the steel industry also demands better control and development of the mould fluxes. In industrial practice for clean steel production, the Al2O3 pick up has generally been observed to be about 2–4%. In view of this, the present study was initiated to experimentally investigate the viscosity of mould fluxes used in Swedish steel industry and the effect of dissolution of alumina in the same. The industrial implications of the slag viscosities measured in the present work are discussed.Viscosities of mould fluxes for continuous casting in steel production have been measured by the rotating cylinder method. Seven industrial mould fluxes, with different compositions, used were included in the study. The effect of the Al2O3 content in the mould fluxes was also investigated. Even relatively small additions of Al2O3 show a significant increase in viscosity. The measurements were carried out in the temperature range of 1373 to 1673 K.

Keyword
viscosity; mould flux; continuous casting; slags
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-7111 (URN)10.2355/isijinternational.47.1533 (DOI)000250375700022 ()2-s2.0-37249011786 (Scopus ID)
Note
QC 20100812. Tidigare titel: Viscosities of some Mould Flux Slags. Uppdaterad från Submitted till Published 20100812.Available from: 2007-05-15 Created: 2007-05-15 Last updated: 2010-08-12Bibliographically approved

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