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A Study of Nitrogen Pickup from the Slag during Waiting Time of Ladle Treatment
KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Mikro-modellering.ORCID-id: 0000-0001-5080-8401
KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Mikro-modellering.ORCID-id: 0000-0002-3548-8638
2014 (Engelska)Ingår i: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 85, nr 4, s. 689-696Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

An investigation of the nitrogen pickup of liquid steel from ladle slag after vacuum degassing was made. Nitride capacities, C-N, of a number of ladle slags were determined at controlled nitrogen and oxygen potentials at 1873K. The nitride capacities in the composition range studied were found to be very low. In accordance with the literature, the nitride capacity was found to increase with increasing SiO2 content. Industrial trials were performed. The nitrogen content of the steel was determined before and after vacuum degassing as well as after the waiting period. Three different trends of the variation of nitrogen content in the steel were observed. Both the laboratory study and the industrial trials revealed that the transfer of nitrogen from slag to steel was not the reason for nitrogen pickup in the steel subsequent to vacuum degassing.

Ort, förlag, år, upplaga, sidor
2014. Vol. 85, nr 4, s. 689-696
Nyckelord [en]
nitrogen pickup, nitride capacity, ladle slag, vacuum degassing
Nationell ämneskategori
Metallurgi och metalliska material
Identifikatorer
URN: urn:nbn:se:kth:diva-146155DOI: 10.1002/srin.201300211ISI: 000333909700021Scopus ID: 2-s2.0-84898069553OAI: oai:DiVA.org:kth-146155DiVA, id: diva2:722531
Anmärkning

QC 20140609

Tillgänglig från: 2014-06-09 Skapad: 2014-06-09 Senast uppdaterad: 2017-12-05Bibliografiskt granskad
Ingår i avhandling
1. Sulfur and nitrogen in ladle slag
Öppna denna publikation i ny flik eller fönster >>Sulfur and nitrogen in ladle slag
2016 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

The present work deals with some aspects of slags related to secondary metallurgy in the steelmaking process. More specifically the focus is given to sulfur and nitrogen in ladle slags. Even though slags have been fairly well-researched in the past, the available data for these elements in typical ladle slag compositions is rather scarce. In some cases the available data is in discordance. There are also inconsistencies between the literature data and what is commonly observed in the industrial processes.

Sulfide capacities were measured at steelmaking temperatures, 1823–1873 K, in ladle slags. The data was found to be in reasonable agreement with the industrial process norms. The sulfide capacity was found to increase with the basic oxides CaO and MgO; and decrease with the acidic components Al2O3 and SiO2. The sulfide capacity was also found to increase with temperature.

The dependence of sulfide capacity on the oxygen partial pressure, for slags containing multivalent elements, was investigated experimentally at 1873 K with a slag containing vanadium oxide. A strong dependence of oxygen partial pressure was observed. The sulfide capacity increase by more than two orders of magnitude when the oxygen partial pressure was increased from 4.6×10-16 atm to 9.7×10-10 atm.

The nitrogen solubility and the effect of carbon was investigated in typical ladle slags and the CaO–MgO–SiO2 system at 1873 K. Carbon increases the nitrogen solubility substantially. In the absence of carbon, the nitrogen solubility is extremely low. Low concentrations of cyanide was detected in the carbon saturated slag. This was much lower than the total nitrogen content and formation of cyanide cannot explain the large increase.

The possibility of removing sulfur with oxidation from used ladle slag was investigated experimentally at 1373–1673 K. The sulfur removal of mostly solid slag was found to be a slow process, and would not suitable for industrial practice. At 1673 K the slag was mostly liquid and more than 85% of the sulfur was removed after 60 min of oxidation in pure oxygen atmosphere.

 

Ort, förlag, år, upplaga, sidor
Stockholm: KTH Royal Institute of Technology, 2016. s. vi, 74
Nationell ämneskategori
Metallurgi och metalliska material
Forskningsämne
Teknisk materialvetenskap
Identifikatorer
urn:nbn:se:kth:diva-182981 (URN)978-91-7595-845-3 (ISBN)
Disputation
2016-04-01, Sal F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (Engelska)
Opponent
Handledare
Anmärkning

QC 20160229

Tillgänglig från: 2016-02-26 Skapad: 2016-02-24 Senast uppdaterad: 2016-02-29Bibliografiskt granskad

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