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An Experimental Study to Improve the Casting Performance of Steel Grades Sensitive for Clogging
Dalarna University, School of Technology and Business Studies, Materials Technology. KTH, Tillämpad processmetallurgi.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. , 60 p.
Keyword [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
Steel Forming and Surface Engineering
Identifiers
URN: urn:nbn:se:du-25727ISBN: 978-91-7729-275-3 (print)OAI: oai:DiVA.org:du-25727DiVA: diva2:1130466
Public defence
2017-03-28, Kollegiesalen, KTH, Brinellvägen 8, 10:00 (English)
Opponent
Supervisors
Projects
VINNOVA
Funder
VINNOVA, Jernkontoret TO23]
Available from: 2017-08-09 Created: 2017-08-09 Last updated: 2017-08-09Bibliographically approved
List of papers
1. Studies of the decarburisation phenomena during preheating of submerged entry nozzles (SEN) in continuous casting processes
Open this publication in new window or tab >>Studies of the decarburisation phenomena during preheating of submerged entry nozzles (SEN) in continuous casting processes
2017 (English)In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 44, no 2, 108-116 p.Article in journal (Refereed) Published
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, 2017
Keyword
Continuous casting, Industrial plant trials, Preheating, Decarburisation, Submerged entry nozzle
National Category
Metallurgy and Metallic Materials
Research subject
Steel Forming and Surface Engineering, Studier angående bildningsmekanismer för igensättningar i gjutrör
Identifiers
urn:nbn:se:du-21260 (URN)10.1080/03019233.2016.1156900 (DOI)000396713200004 ()
Conference
6th International Congress on the Science and Technology of Steelmaking, ICS 2015
Projects
Jernkontoret TO23052
Funder
VINNOVA
Note

Ingår i Jernkontorets forskning: Strategiskt stålforskningsprogram för Svergie 2007-2012. 

Projekttittel: Förbättrad processteknik vid stränggjutning av stål speciellt känsliga för ingensättning.

Available from: 2016-03-22 Created: 2016-03-21 Last updated: 2017-08-09Bibliographically 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...
2017 (English)In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 44, no 2, 117-127 p.Article in journal (Refereed) Published
Abstract [en]

The possibility to reduce clogging in the submerged entry nozzle (SEN) when casting Al killed low carbon steel has been evaluated. The coating materials have been tested in laboratory 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. The chemical composition was analysed by using an FEG-SEM equipped with EDS.The major result showed that alumina reacted with CaTiO3 in the temperature interval from 1550-1600°C. In addition, the clogging ratio showed a decreased clogging tendency for coated nozzles compared to standard nozzles. Also, the results showed that an approximately three times higher steel mass could be teemed through the coated nozzles before clogging occurred compared to trials with uncoated standard nozzles. Overall, it is concluded that plasma sprayed CaTiO3 coatings can reduce the clogging tendency during the continuous casting process.

Place, publisher, year, edition, pages
Maney Publishing, 2017
Keyword
Clogging; Submerged entry nozzle; Pilot plant trials; Al-killed steel; Calcium titanate; Coating; Plasma spraying
National Category
Metallurgy and Metallic Materials
Research subject
Steel Forming and Surface Engineering, Studier angående bildningsmekanismer för igensättningar i gjutrör
Identifiers
urn:nbn:se:du-21364 (URN)10.1179/1743281215Y.0000000065 (DOI)000396713200005 ()
Projects
Förbättrad processteknik vid stränggjutning av stål speciellt känsliga för igensättning
Funder
VINNOVA, TO2352 JK
Note

Finansiering för färdigställande av artikel har erhållits från Stålindustrins forskarskola i sammarbete med SSAB i Oxelösund. 

Stålindustrins forskarskola: Huvudman och sammanhållande i arbetet är Högskolan Dalarna. Satsningen finansieras av Jernkontoret, Region Dalarna, Region Gävleborg, Länsstyrelsen Gävleborg, Högskolan Dalarna, Sandvikens kommun samt samverkande företag. Samarbeten har hittills etablerats med SSAB, Sandvik, Outokumpu, Böhler-Uddeholm, Åkers Sweden, Triple-Steelix och data M Scandinavia. Luleå Tekniska Universitet samt Högskolan i Gävle är viktiga akademipartners.

Available from: 2016-04-14 Created: 2016-04-14 Last updated: 2017-08-09Bibliographically 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...
2016 (English)In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, 1-9 p.Article in journal (Other academic) Epub ahead of print
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.

Keyword
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
Steel Forming and Surface Engineering, Studier angående bildningsmekanismer för igensättningar i gjutrör
Identifiers
urn:nbn:se:du-23393 (URN)10.1080/03019233.2016.1245916 (DOI)
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
Available from: 2016-11-17 Created: 2016-11-17 Last updated: 2017-08-09Bibliographically 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 (ICS2015), China, May 12-14, 2015 in Beijing / [ed] Organized by The Chinese Society for Metals (CSM), 2015Conference 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.

Keyword
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
Steel Forming and Surface Engineering, Studier angående bildningsmekanismer för igensättningar i gjutrör
Identifiers
urn:nbn:se:du-20333 (URN)
Conference
The 6th International Congress on the Science and Technology of Steelmaking (ICS2015), China, May 12-14, 2015 in Beijing
Funder
VINNOVA, TO23-Jernkontoret
Available from: 2015-12-01 Created: 2015-12-01 Last updated: 2017-08-09Bibliographically approved

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Citation style
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  • harvard1
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  • Other locale
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Output format
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