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An Experimental Study to Improve the Casting Performance of Steel Grades Sensitive for Clogging
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy. (Division of Processes)ORCID iD: 0000-0001-6996-5001
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this study, the goal is to optimize the process and to reduce the clogging tendency during the continuous casting process. The focus is on clogging when the refractory base material (RBM) in the SEN is in contact with the liquid steel. It is difficult or impossible to avoid non-metallic inclusions in the liquid steel, but by a selection of a good RBM in the SEN clogging can be reduced.

 

Different process steps were evaluated during the casting process in order to reduce the clogging tendency. First, the preheating of the SEN was studied. The results showed that the SEN can be decarburized during the preheating process. In addition, decarburization of SEN causes a larger risk for clogging. Two types of plasma coatings were implemented to protect the RBM, to prevent reactions with the RBM, and to reduce the clogging tendency. Calcium titanate (CaTiO3) mixed with yttria stabilized zirconia (YSZ) plasma coatings were tested in laboratory and pilot plant trials, for casting of aluminium-killed low-carbon steels. For casting of cerium alloyed stainless steels, YSZ plasma coatings were tested in laboratory, pilot plant and industrial trials. The results showed that the clogging tendency was reduced when implementing both coating materials.

 

It is also of importance to produce clean steel in order to reduce clogging. Therefore, the steel cleanliness in the tundish was studied experimentally. The result showed that inclusions originated from the slag, deoxidation products and tundish refractory and that they were present in the tundish as well as in the final steel product.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2017. , p. 60
Keywords [en]
Preheating, Decarburization, RBM, Clogging, SEN, Plasma sprayed coating, CaTiO3, YSZ, Continuous casting, Pilot plant trials, Industrial plant trials, Clean steel, Tundish, Non-metallic inclusions, MISS
National Category
Metallurgy and Metallic Materials
Research subject
Materials Science and Engineering
Identifiers
URN: urn:nbn:se:kth:diva-202539ISBN: 978-91-7729-275-3 (print)OAI: oai:DiVA.org:kth-202539DiVA, id: diva2:1077205
Public defence
2017-03-28, Kollegiesalen, KTH, Brinellvägen 8, Stockholm, 10:00 (English)
Opponent
Supervisors
Projects
VINNOVA
Funder
VINNOVA, Jernkontoret TO23
Note

QC 20170227

Available from: 2017-02-28 Created: 2017-02-26 Last updated: 2017-02-28Bibliographically approved
List of papers
1. Studies of the decarburisation phenomena duringpreheating of submerged entry nozzles (SEN) incontinuous casting processes
Open this publication in new window or tab >>Studies of the decarburisation phenomena duringpreheating of submerged entry nozzles (SEN) incontinuous casting processes
2016 (English)In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 44, no 2, p. 108-116Article in journal (Refereed) Epub ahead of print
Abstract [en]

Decarburisation of the submerged entry nozzles (SEN) during the preheating process wasinvestigated based on plant trials and thermodynamic modelling at three different steel plants.During the trials the preheating processes were mapped, the temperature profiles wereregistered and post-mortem studies of the SENs with scanning electron microscopy wereperformed. Typically, the glass/silicon powder will form a dense and protective layer inside theSEN when heated over 1100°C. However, this study found that the temperature distributioninside the SEN did not always reach this critical temperature. Thus, decarburisation of the SENwas found at all steel plants. The overall results illustrate that the control of the preheatingprocess needs to be improved at all steel plants. It is suggested that future research should befocused on the development of new coating materials to prevent decarburisation of therefractory base material, which would decrease the chances of clogging during casting.

Place, publisher, year, edition, pages
Taylor & Francis Group, 2016
Keywords
Continuous casting, Industrial plant trials, Preheating, Decarburisation, Submerged entry nozzle
National Category
Metallurgy and Metallic Materials
Research subject
Materials Science and Engineering
Identifiers
urn:nbn:se:kth:diva-185229 (URN)10.1080/03019233.2016.1156900 (DOI)000396713200004 ()2-s2.0-84978536154 (Scopus ID)
Projects
Förbättrad processteknik vid stränggjutning av stål speciellt känsliga för igensättning
Funder
VINNOVA
Note

QCR 20160531

QC 20170331

Available from: 2016-04-14 Created: 2016-04-14 Last updated: 2017-11-30Bibliographically approved
2. Studies of new coating materials to prevent clogging of the submerged entry nozzle (SEN) during continuous casting of Al-killed low carbon steels
Open this publication in new window or tab >>Studies of new coating materials to prevent clogging of the submerged entry nozzle (SEN) during continuous casting of Al-killed low carbon steels
Show others...
2016 (English)In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812Article in journal (Refereed) Epub ahead of print
Abstract [en]

The possibility to reduce clogging in the submerged entry nozzle (SEN) when casting Alkilledlow carbon steel has been evaluated. The coating materials have been tested inlaboratory trials and pilot plant trials. Totally, 2 mixes of the coating material has been tested;containing 4.8 and 9.1 % CaTiO3 mixed with yttria stabilised zirconia (YSZ) powder. Thechemical composition was analysed by using an FEG-SEM equipped with EDS.The major result showed that alumina reacted with CaTiO3 in the temperature interval from1550-1600°C. In addition, the clogging ratio showed a decreased clogging tendency forcoated nozzles compared to standard nozzles. Also, the results showed that an approximatelythree times higher steel mass could be teemed through the coated nozzles before cloggingoccurred compared to trials with uncoated standard nozzles. Overall, it is concluded thatplasma sprayed CaTiO3 coatings can reduce the clogging tendency during the continuouscasting process.

Place, publisher, year, edition, pages
Taylor & Francis, 2016
Keywords
Clogging, Submerged entry nozzle, Pilot plant trials, Al-killed steel, Calcium titanate, Coating, Plasma spraying
National Category
Metallurgy and Metallic Materials
Research subject
Materials Science and Engineering
Identifiers
urn:nbn:se:kth:diva-185230 (URN)10.1179/1743281215Y.0000000065 (DOI)000396713200005 ()2-s2.0-84978477102 (Scopus ID)
Projects
Förbättrad processteknik vid stränggjutning av stål speciellt känsliga för igensättning
Funder
VINNOVA, TO2352 JK
Note

QC 201611123

Available from: 2016-04-14 Created: 2016-04-14 Last updated: 2017-11-30Bibliographically approved
3. Implementation of an YSZ coating material to prevent clogging of the submerged entry nozzle (SEN) during continuous casting of Ce-treated steels
Open this publication in new window or tab >>Implementation of an YSZ coating material to prevent clogging of the submerged entry nozzle (SEN) during continuous casting of Ce-treated steels
Show others...
2018 (English)In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 45, no 2, p. 105-113Article in journal (Refereed) Published
Abstract [en]

The possibility to reduce clogging in the submerged entry nozzle (SEN) during continuous casting of Ce alloyed stainless steels has been studied. This was done by implementing a new plasma coating material, consisting of yttria stabilized zirconia (YSZ). The coating was first tested in pilot-plant trials; where the amount of steel teemed through the plasma coated nozzles was monitored. Thereafter, samples of the coatings from the nozzles were studied using a FEG-SEM equipped with EDS. In addition, the coating material was tested in industrial trials where the performance was judged with respect to the clogging tendency detected as the movement of the stopper rod. The results from both the pilot-plant trials and industrial trials showed that the use of an YSZ coating led to a decreased clogging tendency during the casting in comparison to when using an uncoated SEN. Specifically, the pilot-plant trials showed that the clogging factor was lowered when implementing the YSZ coatings. Furthermore, the industrial trials showed that the clogging tendency, measured by the stopper rod movements, were lower when implementing the YSZ coating.

Place, publisher, year, edition, pages
Taylor & Francis, 2018
Keywords
Continuous casting, Clogging, Rare earth metals, Submerged entry nozzle, New coating material, Plasma coating, Yttria stabilised zirconia, Stainless steel, Pilot-plant trials, Industrial plant trials
National Category
Metallurgy and Metallic Materials
Research subject
Metallurgical process science
Identifiers
urn:nbn:se:kth:diva-196661 (URN)10.1080/03019233.2016.1245916 (DOI)000438587100002 ()2-s2.0-84994187845 (Scopus ID)
Projects
JERNKONTORETS FORSKNING, Delrapport från pilotförsök och industriförsök med ZrO2-belagda dysor och gjutrör genomförda hos ComdiCast AB respektive Outokumpu Stainless AB, Förbättrad processteknik vid stränggjutning av stål speciellt känsliga för igensättningar, Kommitté JK 23052
Funder
VINNOVA, Kommitté JK 23052
Note

QC 20161129

Available from: 2016-11-17 Created: 2016-11-17 Last updated: 2018-08-02Bibliographically approved
4. Post-mortem Studies of Submerged Entry Nozzles (SEN) Coated with Yttria Stabilized Zirconia (YSZ)
Open this publication in new window or tab >>Post-mortem Studies of Submerged Entry Nozzles (SEN) Coated with Yttria Stabilized Zirconia (YSZ)
Show others...
2015 (English)In: The 6th International Congress on the Science and Technology of Steelmaking, Continuous Casting, Beijing, China, 12-14 May, 2015., Chinese Society for Metals , 2015, Vol. 1, p. 469-472Conference paper, Published paper (Refereed)
Abstract [en]

During continuous casting of Ce-treated stainless steel grades an accumulation of inclusions at the submerged entry nozzle’s (SEN) internal wall can cause disturbances or even prevent the molten steel flow. Plasma sprayed yttria stabilized zirconia (YSZ) coating of the SEN’s inlet and stopper rod have been implemented in order to decrease the clogging effect. The coating thickness was 210 µm and the plant trials were conducted during continuous casting of slabs. The clogging tendency was measured by the stopper rod position during the casting process. The results of the measured positions were then compared to experimentally determined information from samples cut out from the SEN’s inlet after casting. Specifically, the samples were analysed using a field emission gun scanning electron microscope (FEG-SEM) equipped with an energy dispersive X-ray spectrometry (EDS). Sample with the dimensions of ̴15x10x5 mm were electrolytic extracted before analysis. The chemical composition at the interface between the solidified steel and refractory base materials were analysed, and traces of the YSZ coating were determined.

The movement of the stopper position indicated that the clogging tendency was reduced for the coated SEN. However, the FEG-SEM analyses showed that clogging of the SEN had occurred during the casting.

Place, publisher, year, edition, pages
Chinese Society for Metals, 2015
Keywords
post-mortem, plasma sprayed coating, yttria stabilised zirconia, rare earth metals, clogging, submerged entry nozzle, continuous casting
National Category
Metallurgy and Metallic Materials
Research subject
Materials Science and Engineering
Identifiers
urn:nbn:se:kth:diva-178014 (URN)2-s2.0-84983130380 (Scopus ID)978-7-111-50125-1 (ISBN)
Conference
The 6th International Congress on the Science and Technology of Steelmaking (ISC2015)
Funder
VINNOVA, TO23 - Jernkontoret
Note

Förstaförfattaren är anställd i Stålindustrins forskarskola med finansiering från Region Dalarna, Region Gävleborg, Länsstyrelsen Gävleborg, Sandvikens kommun, Jernkontoret och Högskolan Dalarna.

QC 20170227

Available from: 2015-12-02 Created: 2015-12-02 Last updated: 2017-02-27Bibliographically approved
5. Experimental Study of non-metallic inclusions behaviour in the Tundish during Continuous Casting of Steel
Open this publication in new window or tab >>Experimental Study of non-metallic inclusions behaviour in the Tundish during Continuous Casting of Steel
Show others...
(English)Manuscript (preprint) (Other academic)
Abstract [en]

The tundish has been experimentally mapped to study reactions between the molten steel and the cover powder as well as between the steel and the tundish lining. Steel samples were collected before casting, in the tundish during the casting process, and after casting. During sampling in the tundish the MISS sampler was used in order to make an in-depth study of two parallel positions of the steel/slag and steel/refractory interfaces. Thereafter, the samples were analysed with SEM in combination with EDS to determine the size and compositions of inclusions. The inclusion data were mapped in ternary phase diagrams to determine the origin of the inclusions. The results showed that two main inclusions groups, slag and deoxidation products, could be found in the samples. In addition, the samples contained inclusions that had been formed due to interactions with the refractory lining material. 

Keywords
tundish, clean steel, continuous casting, industrial plant trials, slag/steel interface, refractory/steel interface, non-metallic inclusions
National Category
Metallurgy and Metallic Materials
Research subject
Metallurgical process science
Identifiers
urn:nbn:se:kth:diva-202562 (URN)
Note

QC 20170228

Available from: 2017-02-27 Created: 2017-02-27 Last updated: 2017-02-28Bibliographically approved

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Citation style
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  • modern-language-association-8th-edition
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  • nn-NO
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Output format
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