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Steel Cleanliness: Deviations during the CAS-OB process
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
2017 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

Different types of deviations in the CAS-OB (composition adjustment by sealed argon bubbling - oxygen blowing) process at SSAB in Luleå are known to occur. Therefore, SSAB Europe in Luleå started this project with the task to investigate deviations during the CAS-OB process, to see how the deviations affect the steel cleanliness in terms of non-metallic inclusions. The aim of this project has been to locate unwanted deviations from the standard practice associated with the CAS-OB process. This study is restricted to Al-killed and calcium treated steel grades only.

In this study has 34 different steel heats, including four references, 25 deviations and five steel heats from previous studies and reclaims been investigated. Totally, 18 steel samples have been retrieved from 14 different steel heats. The steel samples have been prepared and analyzed per the standards SS111114 and SS111116 to retrieve inclusion drawings and PC-mic results.

Several types of unwanted deviations in the CAS-OB process has been detected, including; cooling the steel heats with steel scrap after calcium treatment and multiple of small additives of aluminum late in the process. The results indicate that cooling with scrap after the calcium treatment worsen the steel cleanliness in terms of non-metallic inclusions and should therefore be avoided. Furthermore, multiple of small aluminum additions late in the process is likely a contributing parameter to increase the projected length of the inclusions.

Adding alloying elements after the calcium treatment to adjust the composition is another frequently occurring deviation from the practice, and in many cases, extra calcium is added after the alloys. The results from this study implies that it is preferable not to add any extra calcium if extra additions of alloying elements are necessary, since it seems to generate larger inclusions.

Place, publisher, year, edition, pages
2017.
Keywords [en]
Steel cleanliness, Inclusions, CAS-OB, Deviations
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-215639OAI: oai:DiVA.org:kth-215639DiVA, id: diva2:1148550
External cooperation
SSAB AB Luleå
Subject / course
Process Science of Materials
Educational program
Master of Science in Engineering - Materials Design and Engineering
Presentation
2017-09-14, Calphad, Stockholm, 13:00 (English)
Supervisors
Examiners
Available from: 2017-10-18 Created: 2017-10-11 Last updated: 2017-10-18Bibliographically approved

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The full text will be freely available from 2027-09-14 13:00
Available from 2027-09-14 13:00

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CiteExportLink to record
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Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
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Language
  • de-DE
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Output format
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