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Equilibrium between slag, steel and inclusions during ladle treatment: comparison with production data
KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
2007 (Engelska)Ingår i: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 34, nr 4, s. 312-324Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The primary purpose of the investigation was to determine whether equilibrium conditions exist between slag and steel and inclusions and steel after silicon deoxidation and aluminium deoxidation. In doing so, the performance of three different models for predicting oxide component activities was also evaluated. The results from the oxide activity models were used to calculate oxygen activities in the steel melt. Industrial data such as steel, slag and inclusion component concentrations, as well as temperature, were used as input to the calculations. One general conclusion drawn was that although the results from the different models showed similar trends, the models did not predict the same actual values for specific calculations. Predicted theoretical equilibrium oxygen activity values were compared with plant measurements of oxygen activity. Here, it was found that the oxygen activity values pertaining to the equilibrium between steel and inclusions were higher than corresponding measured values. The calculations for the equilibrium between the top slag and steel melt, however, resulted in theoretical oxygen activity values considerably lower than corresponding measurements. It was thus concluded that equilibrium conditions did not exist between the top slag and the steel bulk with respect to oxygen. Overall, the models proved useful in predicting oxide activities, but the lack of equilibrium between top slag and molten steel made the calculation of oxygen activity difficult.

Ort, förlag, år, upplaga, sidor
2007. Vol. 34, nr 4, s. 312-324
Nyckelord [en]
models; activity; slag; steel; oxygen; oxide; SLAGS
Nationell ämneskategori
Metallurgi och metalliska material
Identifikatorer
URN: urn:nbn:se:kth:diva-8120DOI: 10.1179/174328107X168039ISI: 000248541700006Scopus ID: 2-s2.0-35348944450OAI: oai:DiVA.org:kth-8120DiVA, id: diva2:13357
Anmärkning
QC 20100707Tillgänglig från: 2008-03-19 Skapad: 2008-03-19 Senast uppdaterad: 2017-12-14Bibliografiskt granskad
Ingår i avhandling
1. Thermodynamic Aspects on Inclusion Composition and Oxygen Activity during Ladle Treatment
Öppna denna publikation i ny flik eller fönster >>Thermodynamic Aspects on Inclusion Composition and Oxygen Activity during Ladle Treatment
2008 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

Two industrial studies and one set of lab scale trials have been done. In addition, a theoretical study has been done. The main focus has been on non metallic inclusion composition during the ladle refining operation in industrial steel production. Sampling has been done together with careful inclusion determination. The inclusion composition is related to different variables. In the industrial trials samples have been taken at different steps during the ladle refining period. Steel and slag composition as well as temperature and oxygen activity have been determined.

The thesis is based on five supplements with different major objectives, all related to the inclusion composition. The equilibrium top slag-steel bulk and inclusions-steel bulk were investigated by comparison between calculated and measured oxygen activity values. The oxygen activity and relation to temperature has also been discussed as well as oxygen activity and temperature gradients. The effect of vacuum pressure on inclusion composition has been evaluated in a theoretical study as well as lab scale trials. The inclusion composition has been studied during the industrial ladle treatment process. The inclusion composition was related to top slag composition and other parameters during ladle treatment.

The major findings in the thesis are the lack of equilibrium conditions with respect to top-slag and steel bulk before vacuum treatment. The inclusions have been found to be closer to equilibrium with the steel bulk. Al/Al2O3 equilibrium has been found to control the oxygen activity after Al-deoxidation. Evaluation of inclusion composition during the ladle refining has revealed that the majority of the inclusions showed a continuous composition change throughout the ladle refining process, from high Al2O3, via MgO-spinel to finally complex types rich in CaO and Al2O3. The final inclusion composition after vacuum treatment was found to be close to the top slag composition. Vacuum pressure has been found to have a theoretical effect on inclusion composition at very low pressures.

Ort, förlag, år, upplaga, sidor
Stockholm: KTH, 2008. s. xii, 68
Nyckelord
Ladle treatment, thermodynamics, inclusions, steel, slag, equilibrium, ladle treatment, vacuum, oxide activity, oxygen activity.
Nationell ämneskategori
Metallurgi och metalliska material
Identifikatorer
urn:nbn:se:kth:diva-4673 (URN)978-91-7178-904-4 (ISBN)
Disputation
2008-04-08, B3, Materialvetenskap, Brinellvägen 23, Stockholm, 10:00
Opponent
Handledare
Anmärkning
QC 20100712Tillgänglig från: 2008-03-19 Skapad: 2008-03-19 Senast uppdaterad: 2010-07-12Bibliografiskt granskad
2. A study of slag-steel-inclusion interaction during Ladle treatment
Öppna denna publikation i ny flik eller fönster >>A study of slag-steel-inclusion interaction during Ladle treatment
2006 (Engelska)Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

The thesis is based on two supplements with two major objectives. In the first supplement equilibrium top slag-steel bulk and inclusions-steel bulk were investigated by comparison between calculated and measured oxygen activity values. This was done by applying different oxide activity models for slags combined with thermodynamic calculations. In the second supplement the inclusion composition is studied during the ladle refining process. The inclusion composition is related to top slag composition and other parameters during ladle

treatment.

The work was carried out by collecting data during well controlled sampling procedures at two different steel plants. Extensive inclusion analyses in Scanning Electron Microscope, SEM, were done. The data was used together with thermodynamics for a description of the interaction between slag-steel-inclusion interaction during ladle treatment.

Evaluation of inclusion composition during the ladle refining have revealed that the majority of the inclusions belonged to the system Al2O3-CaO-MgO-SiO2 and showed a continuous composition change throughout the ladle refining process, from high Al2O3, via MgO-spinel to finally complex types rich in CaO and Al2O3. The final composition after vacuum treatment was found to be close to the top slag composition. Small process parameter changes and practical variations during ladle refining were proven to give large differences of the inclusion composition.

Finally, it was concluded that equilibrium does not exist between top slag and steel bulk, with respect to oxygen, for the studied conditions. However, the equilibrium does exist between the steel bulk and inclusion.

Ort, förlag, år, upplaga, sidor
Stockholm: KTH, 2006. s. x, 28
Serie
ISRN KTH/MSE--06/46--SE+APRMETU/AVH
Nyckelord
Ladle treatment, steel, slag, inclusions, ladle, refining, vacuum, tool steel, oxide activity, slag models, oxygen, equilibrium
Nationell ämneskategori
Metallurgi och metalliska material
Identifikatorer
urn:nbn:se:kth:diva-4018 (URN)91-7178-403-9 (ISBN)
Presentation
2006-06-15, B2, Materialteknik, Brinellvägen 23, Stockholm, 10:00
Opponent
Handledare
Anmärkning
QC 20101109Tillgänglig från: 2006-06-01 Skapad: 2006-06-01 Senast uppdaterad: 2010-11-09Bibliografiskt granskad

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