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Viscosity Measurements of Some Mould Flux Slags
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
2007 (English)In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, 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.

Place, publisher, year, edition, pages
2007. Vol. 47, no 10, 1533-1540 p.
Keyword [en]
viscosity; mould flux; continuous casting; slags
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-7111DOI: 10.2355/isijinternational.47.1533ISI: 000250375700022Scopus ID: 2-s2.0-37249011786OAI: oai:DiVA.org:kth-7111DiVA: diva2:12025
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: 2017-12-14Bibliographically approved
In thesis
1. Densities and viscosities of slags: modeling and experimental investigations
Open this publication in new window or tab >>Densities and viscosities of slags: modeling and experimental investigations
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
density, nolar volume, thermodynamics, enthalpies, model, slags, oxide melts, viscosity, mould flux, continuous casting
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-3926 (URN)91-7178-336-9 (ISBN)
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
2. Investigations of Slag Properties and Reactions
Open this publication in new window or tab >>Investigations of Slag Properties and Reactions
2007 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

The present dissertation describes 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 fluoride- and manganese containing slags, as for example, mould flux slags and manganese slags used in ferromanganese production.

c) estimating fluoride emissions from industrial slags and mould fluxes.

d) study the reaction between carbon particles, hematite containing slags and in oxygen containing atmosphere.

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 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 continuous 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.

A similar experimental technique was employed to estimate the viscosity of twelve synthetic slags corresponding to composition of the raw materials used in ferromanganese production. The flow rate of the liquid slag, which is determined by the slag viscosity, is an important parameter affecting the reduction rate of manganese oxide. The results show a clear correlation between manganese oxide content and viscosity. An increase of MnO in the slag lowers the viscosity. The measured viscosities have also been connected to the structure of the silicates.

The fluoride loss from the binary slag systems Al2O3-SiO2, CaO-SiO2 and MgOSiO2 with additions of CaF2 was studied by thermogravimetric (TGA) studies. The Arrhenius activation energy for the evaporation reaction of fluorides was found to be dependent on temperature and slag chemistry for the slags studied. A correlation between the activation energy for fluoride evaporation and activity of SiO2 in the slag melt was established. This relationship obtained for the binary systems appears also to be suitable for the ternary systems Al2O3-CaO-SiO2 with CaF2 addition, which indicates a possibility to estimate the fluoride emissions from industrial slags and mould fluxes.

A Confocal Scanning Laser Microscopy was used to investigate the reaction between carbon particles in hematite containing slags and in oxygen containing atmosphere. Experiments with varying temperature and slags with varying FeOx content were carried out. The general trends were that the particle size decrease was more rapid with increase of FeOx amount and/or temperature was increased.

Place, publisher, year, edition, pages
Stockholm: KTH, 2007. x, 80 p.
Series
KTH/MSE, 2007:14
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-4378 (URN)978-91-7178-650-0 (ISBN)
Public defence
2007-05-25, Salongen, KTHB, Osquars backe 31, STOCKHOLM, 10:00
Opponent
Supervisors
Note
QC 20100812Available from: 2007-05-15 Created: 2007-05-15 Last updated: 2010-08-12Bibliographically approved

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