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Three Dimensional Evaluations of REM Clusters in Stainless Steel
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.
2014 (Engelska)Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 54, nr 6, s. 1266-1273Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

It is known that clusters in liquid steel have a harmful effect on the casting process and the quality of the final steel product. In this study, clusters. of rare earth metals (REM) were investigated in steel samples of a S30185 stainless steel grade from a pilot trial (PT, 250 kg) and from an industrial heat (IH, 100 t). Samples were taken from the liquid steel at different holding times after the addition of mischmetal. Thereafter, REM clusters collected on film filters after electrolytic extraction and filtration were investigated in three dimensions (3D) by SEM in combination with EDS. The morphology, composition, number and size of clusters in PT and IH steel samples were analyzed and compared as a function of holding time. It was found that typical clusters with regular and irregular inclusions were the main type of clusters (69%-98%) in all PT and IH steel samples. The composition of inclusions in clusters corresponded mostly to REM-oxides. The size of clusters that were observed in different samples varied mainly from 2 to 23 mu m. In addition, the size and number of most clusters in PT are larger than those in IH samples. Furthermore, the formation mechanisms and evolution of different type of REM clusters were discussed in both PT and IH heats.

Ort, förlag, år, upplaga, sidor
2014. Vol. 54, nr 6, s. 1266-1273
Nyckelord [en]
stainless steel, REM clusters, electrolytic extraction, cluster size distribution
Nationell ämneskategori
Materialteknik Metallurgi och metalliska material
Identifikatorer
URN: urn:nbn:se:kth:diva-145670DOI: 10.2355/isijinternational.54.1266ISI: 000337984000013Scopus ID: 2-s2.0-84904977580OAI: oai:DiVA.org:kth-145670DiVA, id: diva2:719509
Forskningsfinansiär
Vinnova
Anmärkning

QC 20140808. Updated from manuscript to article in journal.

Tillgänglig från: 2014-05-26 Skapad: 2014-05-26 Senast uppdaterad: 2017-12-05Bibliografiskt granskad
Ingår i avhandling
1. Three Dimensional Determinations of Inclusions in Ferroalloys and Steel Samples
Öppna denna publikation i ny flik eller fönster >>Three Dimensional Determinations of Inclusions in Ferroalloys and Steel Samples
2014 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

As the requirements on material properties increase, there has been a demand on an additional knowledge on the effect of impurities in the ferroalloyson the steel cleanness. Thus, the number, morphology, size and composition of inclusions in sixdifferent ferroalloys (FeTi, FeNb, FeSi,SiMn, LC and HC FeCr) were investigatedin this study. This was done in three dimensions (3D) by using a SEM in combination with EDS after electrolytic extraction of the ferroalloy samples. Theresults show that thenon-metallic and metallic inclusions can besuccessfully analyzed on the surface of a film filterafter a separation of the inclusions from the matrix. Overall, the inclusions canbe divided into two categories depending on the melting point. Furthermore, the possible transformation of different kinds of inclusions after their addition to the liquid steel canalso be determined.

The inclusions and clusters in steel samples of two similar steel grades of high-silicon non-calcium treated (HSiNC) stainless steels were also investigated and compared during ladle treatment and continuous casting. Samples of liquid steel and slag were taken at different stages of the ladle treatment and casting during two plant trials: a low Al steel (LAl) and a high Al steel (HAl). Spherical (SP), irregular and regular (IR) inclusions and clusters (CL) were observed in the samples from both heats. It wasfound that the morphology and composition of inclusions and clusters in both heats were significantly changed during the ladle treatment and casting. Most of inclusions (44-98%) in a low Al steel are MgO-CaO-SiO2-Al2O3spherical inclusions. The compositions of irregular and regularinclusions and clusters in steel samples of a high Al steel were mostly MgO·Al2O3spinel, but also complex sphericalinclusions containing Al2O3-MgO-CaO-SiO2. In addition, the phase stabilitydiagram based on Darken’s quadratic formalism and Redlich-Kister type polynomial was estimated for both heats at a non-infinite solution.

It is known that clusters in liquid steel have a harmful effect on the casting process and the quality of the final steel product. Therefore, clusters of rare earth metals (REM) were investigated in steel samples of a S30185 stainless steel grade from a pilot trial (PT, 250 kg) and from an industrial heat (IH, 100 t). Samples were taken from the liquid steel at differentholding times after the addition of a mischmetal. The morphology, composition, number and size of clusters in PT and IH steel samples were analyzed and compared as a function of the holding time. It was found that typical clusters with regular and irregular inclusions were the main type of clusters (69%-98%) in all PT and IH steel samples. The composition of inclusions in clusters corresponded mostly to REM-oxides. The size of clusters that were observed in different samples varied mainly from 2 to 23 μm. In addition, the size and number of most clusters in PT are larger than those in IH samples.

Largesize inclusions are recognized to be crucially harmful for the mechanical properties of steel products. Therefore, predictionsof the maximum size of Al2O3-CaO spherical inclusions in an Fe-10 mass% Ni alloy have been examined based on two dimensional (2D) and three dimensional (3D) investigations. The effects of the number of measurements and unit volume on the estimated 3D results were also investigated.

Ort, förlag, år, upplaga, sidor
Stockholm: KTH Royal Institute of Technology, 2014. s. vii, 67
Nyckelord
Three dimensional, Ferroalloy, Inclusion, Spinel inclusion, T hermodynamic calculation, REM clusters, Formation mechanism, Statistical analysis, Maximum size
Nationell ämneskategori
Metallurgi och metalliska material
Identifikatorer
urn:nbn:se:kth:diva-145225 (URN)978-91-7595-156-0 (ISBN)
Disputation
2014-06-11, Sal B1, Brinellvägen 23, KTH, Stockholm, 10:00 (Engelska)
Opponent
Handledare
Anmärkning

QC 20140526

Tillgänglig från: 2014-05-26 Skapad: 2014-05-14 Senast uppdaterad: 2014-05-26Bibliografiskt granskad

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Bi, YanyanKarasev, AndreyJönsson, Pär G.
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