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Effects of slag composition and cooling rate on formation of glaze on MgO refractory
KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Mikro-modellering.
KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Mikro-modellering.
KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Mikro-modellering.ORCID-id: 0000-0002-3548-8638
2010 (Engelska)Ingår i: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 37, nr 1, s. 27-34Artikel i tidskrift (Refereegranskat) Published
##### Abstract [en]

The formation of a slag glaze layer on dense and porous MgO rods was studied by dipping MgO rods into liquid slag at 1873 K and thereafter cooling the rods at a predetermined cooling rate. Three different slag compositions and three different cooling rates were employed. It was found that the phases formed upon cooling were mostly dependent on slag composition and to a minor extent on the cooling rate. The initially liquid slag was transformed into crystalline phases for all the samples except the ones terminated at 1573 K and one of the samples with high cooling rate. In addition, the three slags were equilibrated at 1773, 1673 and 1573 K in order to get an understanding of the equilibrium phases and their relationship during cooling. On the basis of the experimental results, the mechanism regarding entrainment of exogenous inclusions from the refractory lining was also discussed.

##### Ort, förlag, år, upplaga, sidor
2010. Vol. 37, nr 1, s. 27-34
##### Nationell ämneskategori
Metallurgi och metalliska material
##### Identifikatorer
ISI: 000273918200005Scopus ID: 2-s2.0-77949456990OAI: oai:DiVA.org:kth-19141DiVA, id: diva2:337188
##### Ingår i avhandling
1. Some Fundamental Aspects Concerning Secondary Steelmaking
Öppna denna publikation i ny flik eller fönster >>Some Fundamental Aspects Concerning Secondary Steelmaking
2011 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
##### Abstract [en]

The present thesis deals with some aspects concerning secondary metallurgy of steel where there is little or very inconsistent information in the literature. More specifically, it is devoted to the studies on high temperature phase equilibria in the Al2O3-CaO-MgO-SiO2 system, the formation of ladle glaze and the thermodynamics of magnesium in liquid iron.

First, the solidification of different slags on MgO based refractories was studied in order to reveal the mechanism behind the formation of “ladle glaze”. The formation of the slag glaze layer was studied by dipping MgO rods, dense or porous, into liquid slags at 1873 K. The rods were thereafter cooled at a predetermined rate. From a later SEM-EDS microscopy, it was found that the initial slag composition had the most profound effect on the phases found in the solidified slag layer. It was found that the type of MgO rod used and cooling speed had a minor impact on the morphology on the solidified samples. In addition, the slags used in the study were equilibrated at 1773 K, 1673 K and 1573 K in order to get an understanding of the equilibrium phases and their relationship during cooling. On the basis of the experimental results, the mechanism regarding entrainment of exogenous inclusions from the refractory lining was also discussed.

Secondly, phase diagram studies in the high basicity region of the Al2O3-CaO-MgO-SiO2 system were performed using the quench technique followed by EPMA analysis. The main focus in the study was to find the liquidus surfaces for MgO and CaO saturation at 1773 and 1873 K. Based on the experimental data, phase diagrams for the 25, 30 and 35 mass percent alumina sections were constructed for silica contents generally less than 20 mass percent.. The results generally agreed very well with previous, well established phase diagrams. In addition, the activities of MgO, CaO and Al2O3 were estimated using the phase diagram information.

At last, the thermodynamics of magnesium in liquid iron at 1823 K were studied. In a pre-study, the thermodynamics of Ag-Mg solutions were studied, necessary for the Fe-Mg system. For the Ag-Mg system, two different experimental techniques were used; the vapor pressure method and the gas equilibration technique. The temperature range of the Ag-Mg study was 1573 to 1823 K. It was found that the excess Gibbs energy of this system can be described quite well with a sub-regular solution model. In the Fe-Mg study, the partition of Mg between liquid iron and liquid silver were studied at 1823 K. Using the results from the pre-study, the activity coefficient of Mg in liquid iron and the self-interaction parameter $\xi\frac{Mg}{Mg}$were determined at 1823 K.

##### Ort, förlag, år, upplaga, sidor
Stockholm: KTH Royal Institute of Technology, 2011. s. 44
Materialteknik
##### Identifikatorer
urn:nbn:se:kth:diva-31131 (URN)978-91-7415-901-1 (ISBN)
##### Disputation
2011-04-01, Sal D2, Lindstedtsvägen 5, KTH, Stockholm, 10:00 (Engelska)

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##### Av författaren/redaktören
Gran, JimmyThunman, MikaelSichen, Du
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Mikro-modellering
##### I samma tidskrift
Ironmaking & steelmaking
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Metallurgi och metalliska material

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