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Regulation of Nitrogen Content in High Alloyed Stainless Steels during the AOD Process
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
2019 (English)Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
Abstract [en]

As a final step in the argon oxygen decarburisation (AOD) process, argon- and nitrogen gas is blown through the melt. To regulate the nitrogen content in the steel melt during this step a reliable model is needed. With data from 31 heats of the duplex stainless steel SAF2507 collected at Sandvik Materials Technology (SMT), different models are investigated. This is done by looking at the partial pressure of the nitrogen gas and the nitrogen content achieved during each heat. By calculating the nitrogen solubility in the steel melt with different models and then using Sieverts’s law, a partial pressure for the nitrogen gas is obtained for each heat and compared with the data. With adjustments done for a model obtained from J. Kijac et al., more reliable results are attained than by the model used today at SMT. It should be kept in mind that this model is based on the theory with diluted solution and is therefore not optimal for high alloyed steels, and it is suggested to develop a model from a software based on real solution such as Thermo-Calc.

Abstract [sv]

I slutskedet av AOD-processen blåses argon- och kvävgas genom stålsmältan. En pålitlig modell behövs för att reglera kvävehalten i stålsmältan under det här steget. Olika modeller undersöks med data från 31 charger av det duplexa rostfria stålet SAF2507 samlad från Sandvik Materials Technology (SMT). Undersökningen sker genom att titta på partialtrycket av kvävgasen och kvävehalten som uppnåddes för varje charge. Genom att beräkna kvävelösligheten i stålsmältan med olika modeller och sedan använda Sieverts lag, kan ett partialtryck för kvävgas räknas ut för varje charge och jämföras med datan. Mer exakta resultat är uppnådda med en justerad modell hämtad från J. Kijac et al. jämfört med den modell använd på SMT idag. Att ha i åtanke är att denna modell är baserad på teori med antagande om utspädd lösning, vilket inte är optimalt för höglegerade stål och ett förslag är att utveckla en modell med hjälp av ett mjukvaruprogram som baseras på äkta lösning såsom Thermo-Calc.

Place, publisher, year, edition, pages
2019. , p. 32
Series
TRITA-ITM-EX ; 2019:519
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-254419OAI: oai:DiVA.org:kth-254419DiVA, id: diva2:1332065
External cooperation
Sandvik Materials Technology Sandvik AB
Educational program
Master of Science in Engineering - Materials Design and Engineering
Supervisors
Examiners
Available from: 2019-07-09 Created: 2019-06-27 Last updated: 2019-07-09Bibliographically approved

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