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A Study of Nitrogen Pickup from the Slag during Waiting Time of Ladle Treatment
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.ORCID iD: 0000-0001-5080-8401
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.ORCID iD: 0000-0002-3548-8638
2014 (English)In: Steel Research International, ISSN 1611-3683, Vol. 85, no 4, 689-696 p.Article in journal (Refereed) 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.

Place, publisher, year, edition, pages
2014. Vol. 85, no 4, 689-696 p.
Keyword [en]
nitrogen pickup, nitride capacity, ladle slag, vacuum degassing
National Category
Metallurgy and Metallic Materials
URN: urn:nbn:se:kth:diva-146155DOI: 10.1002/srin.201300211ISI: 000333909700021ScopusID: 2-s2.0-84898069553OAI: diva2:722531

QC 20140609

Available from: 2014-06-09 Created: 2014-06-09 Last updated: 2016-02-29Bibliographically approved
In thesis
1. Sulfur and nitrogen in ladle slag
Open this publication in new window or tab >>Sulfur and nitrogen in ladle slag
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
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.


Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. vi, 74 p.
National Category
Metallurgy and Metallic Materials
Research subject
Materials Science and Engineering
urn:nbn:se:kth:diva-182981 (URN)978-91-7595-845-3 (ISBN)
Public defence
2016-04-01, Sal F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)

QC 20160229

Available from: 2016-02-26 Created: 2016-02-24 Last updated: 2016-02-29Bibliographically approved

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