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  • 151.
    Bonvalet, Manon
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Sauvage, Xavier
    Normandie Univ, UNIROUEN, INSA Rouen, CNRS, Groupe de Physique des Matériaux, 76000, Rouen, France.
    Blavette, Didier
    Normandie Univ, UNIROUEN, INSA Rouen, CNRS, Groupe de Physique des Matériaux, 76000, Rouen, France.
    Intragranular nucleation of tetrahedral precipitates and discontinuous precipitation in Cu-5wt%Ag2019Ingår i: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 164, s. 454-463Artikel i tidskrift (Refereegranskat)
  • 152.
    Bonvalet-Rolland, Manon
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap. KTH Royal Inst Technol, Dept Mat Sci & Engn, Stockholm, Sweden..
    Philippe, Thomas
    CNRS, Ecole Polytech, Phys Matiere Condensee, F-91120 Palaiseau, France..
    Ågren, John
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Kinetic theory of nucleation in multicomponent systems: An application of the thermodynamic extremum principle2019Ingår i: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 171, s. 1-7Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Nucleation kinetics in a multicomponent supersaturated solid solution is examined. Attachment rate of atoms to a nucleus of a size close to the critical one is determined combining a thermodynamic extremum principle and the Fokker-Planck equation. Two limiting cases are examined; when bulk diffusion controls the nucleation kinetics and when the process is limited by the interfacial mobility. The mixed regime is also treated. Moreover, the growth law in multicomponent alloys is derived in the general case, when both mechanisms are considered. Additionally, the attachment rate is derived, in the classical framework, from a new macroscopic growth equations and the fundamental role of the interfacial mobility is examined. These new general expressions, for the attachment rates and the growth laws, determined either applying the thermodynamic extremum principle or derived from the classical formalism are found to be consistent.

  • 153.
    Borgenstam, Annika
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallografi.
    Edmonds, D.
    Hillert, Mats
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallografi.
    Eutectoids with cementite as the major constituent in Fe-C-M alloys2016Ingår i: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 103, s. 280-289Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The addition of a third element to hypereutectoid Fe-C alloys may cause inclusions of a minor constituent in the precipitate of cementite from austenite even if the initial austenite is supersaturated only with cementite. Cementite will often become the major constituent of this kind of microstructure. For Fe-C-Cu alloys this has been explained as the result of precipitation from supersaturated cementite. An alternative mechanism could be that the mixture of cementite and a minor constituent forms by simultaneous and cooperative growth of the two phases, i.e., by a reaction that may be regarded as eutectoid. This mechanism has already been applied to explain the occurrence of eutectoid colonies with cementite as the major constituent and a minor constituent for which there was no supersaturation initially. This phenomenon has been observed in hypereutectoid ternary Fe-C alloys with Al, Mn or Si. The necessary requirements on the ordinary isothermal phase diagram are now examined with a graphical method based on the slopes of tie-lines. It predicts the phenomenon in all cases where it has been observed, including Fe-C-Cu and not in the Fe-C-Ni and Fe-C-Cr systems where it has not been observed. The requirements become more evident when the calculated phase equilibria are plotted as an isothermal phase diagram with the alloy content as a function of the carbon activity instead of carbon content. Finally, a comparison is made with bainite in Fe-C alloys where ferrite is the major and cementite the minor constituent. The same two explanations have been proposed for that case.

  • 154.
    Borgenstam, Annika
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallografi.
    Hillert, Mats
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallografi.
    Kinetics of bainite transformation in steels2012Ingår i: Phase Transformations in Steels, Elsevier, 2012, Vol. 1, s. 468-501Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    The main kinetic features of the formation of bainite are discussed, firstly in relation to two incompatible hypotheses for the growth mechanism of bainitic ferrite. One is based on diffusionless growth of bainitic ferrite but diffusional growth of Widmanstätten ferrite. The other is based on the assumption that there is only one kind of acicular ferrite and it grows under simultaneous diffusion of carbon into the interior of the parent austenite. The kinetics of the first stage of bainite formation, the growth of acicular ferrite, is treated in detail because it has been subject to the more intensive research. The kinetics of the reactions by which cementite forms and the subsequent reactions, by which the transformation to bainite is completed, have been subject to less research.

  • 155.
    Borgh, Ida
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallografi.
    Aspects of Structural Evolution in Cemented Carbide – Carbide Size, Shape and Stability2013Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Cemented carbide is a composite material used in applications like cutting tools and rock drilling inserts. The material commonly consists of WC grains embedded in a Co-rich binder phase and the material properties strongly depend on the WC grain size. Hence, to tailor the properties it is important to understand the fundamental mechanisms of grain coarsening. At the same time, the higher demands on material properties today also require new solutions. In the present work, some different aspects of structural evolutions in cemented carbides have been investigated.

    The first part of the work considers WC grain coarsening by means of size, size distribution and shape. Some efforts of the work have been to evaluate the effects of C-activity and initial WC powder size and distribution on the coarsening behavior in the material using different characterization techniques, e.g. scanning electron microscopy, and electron backscattered diffraction. Additionally, two earlier developed models are used and evaluated with the experimental data. The results indicate that the C-activity will affect size, size distribution and shape of the WC grains. It was also observed that the initial WC powder size and size distribution will have a large influence on the WC grain coarsening. The statistical shape was found to fit a spherical approximation but for individual grains both faceted and non-faceted shapes was observed. Steps and planar defects were observed supporting that the nucleation of new atomic layers is the main rate limiting mechanism for grain coarsening.

    The second part of this work considers the carbide phase stability in the (Ti,Zr)C system. The phase stability was investigated after synthesizing and aging a mixed (Ti,Zr)C using X-ray diffraction and different types of electron microscopy techniques. A decomposed lamellar structure was found with a composition variation of approximately 10% between the 50-75 nm thick lamellas. The experimental investigations were supported by computational work and the results were in good agreement. Additionally, two cemented carbide related systems were studied. A miscibility gap was found in the two investigated systems, (Ti,Zr,W)(C,N)-Co or Fe-graphite, and the effect of N2-gas pressure was investigated suggesting a critical N2-gas pressure below 0.1 bar.

  • 156.
    Borgh, Ida
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallografi.
    Hedström, Peter
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallografi.
    Blomqvist, Andreas
    Ågren, John
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallografi.
    Odqvist, Joakim
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallografi.
    Synthesis and phase separation of (Ti,Zr)C2014Ingår i: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 66, s. 209-218Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Synthesis and phase separation of (Ti,Zr)C were investigated in the present work. The (Ti,Zr)C phase was synthesized at 2200 C and subsequently aged at 1300 C for different times. The microstructure was investigated using X-ray diffraction and electron microscopy, and supplemented by first-principles calculations. The (Ti,Zr)C phase separates into a lamellar nanostructure with alternating Ti- and Zr-rich face-centered cubic domains as well as non-stoichiometric TiC and ZrC. The lamellar structure is a consequence of phase separation within the miscibility gap that is directionally constrained by high coherency stresses, as indicated by the first-principles calculations. Moreover, the increased hardness due to the phase separation suggests that the mixed carbide could be used as a strengthening constituent in, for example, cemented carbides.

  • 157.
    Borgh, Ida
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallografi.
    Hedström, Peter
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallografi.
    Borgenstam, Annika
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallografi.
    Ågren, John
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallografi.
    Odqvist, Joakim
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallografi.
    Effect of carbon activity and powder particle size on WC grain coarsening during sintering of cemented carbides2014Ingår i: International journal of refractory metals & hard materials, ISSN 0958-0611, E-ISSN 2213-3917, Vol. 42, s. 30-35Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Liquid-phase sintering is an important step in the production of cemented carbides. During sintering, the average WC grain size increases, leading to a coarser structure, which affects the performance of the final product. The coarsening occurs by dissolution of small grains and growth of large grains. In the present work, the effect of high carbon activity during sintering on the WC grain coarsening has been evaluated using electron backscattered diffraction (EBSD) and the results have been compared with a previous work where sintering was performed at a lower carbon activity. A more homogeneous grain size distribution was observed in alloys sintered at a high carbon activity. In addition, the effect of the initial powder particle size distribution was investigated. It was found that the coarsening rate of a WC powder with an initial small average grain size is significantly higher as compared to the coarsening rate for a powder with a larger initial average grain size. The results obtained emphasize the importance of considering the complete particle size distribution in order to predict coarsening.

  • 158.
    Borgh, Ida
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallografi.
    Hedström, Peter
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallografi.
    Odqvist, Joakim
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallografi.
    Borgenstam, Annika
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallografi.
    Ågren, John
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallografi.
    Gholinia, Ali
    Winiarski, Bartlomiej
    Withers, Philip J.
    Thompson, George E.
    Mingard, Ken
    Gee, Mark G.
    On the three-dimensional structure of WC grains in cemented carbides2013Ingår i: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 61, nr 13, s. 4726-4733Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the present work, the size distribution and shape of WC grains in cemented carbides (WC-Co), with different Co contents, have been investigated in three dimensions. Direct three-dimensional (3-D) measurements, using focused ion beam serial sectioning and electron backscattered diffraction (EBSD), were performed and a 3-D microstructure was reconstructed. These measurements were supplemented by two-dimensional (2-D) EBSD and scanning electron microscopy on extracted WC grains. The data from 2-D EBSD collected on planar sections were transformed to three dimensions using a recently developed statistical method based on an iterative inverse Saltykov procedure. This stereological analysis revealed that the assumed spherical shape of WC grains during the Saltykov method is reasonable and the estimated 3-D size distribution is qualitatively in good agreement with the actual distribution measured from 3-D EBSD. Although the spherical assumption is generally fair, the WC grains have both faceted and rounded surfaces. This is a consequence of the relatively low amount of liquid phase during sintering, which makes impingements significant. Furthermore, the observed terraced surface structure of some WC grains suggests that 2-D nucleation is the chief coarsening mechanism to consider.

  • 159.
    Borgh, Ida
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallografi.
    Hedström, Peter
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallografi.
    Persson, Tomas
    Norgren, Susanne
    Borgenstam, Annika
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallografi.
    Ågren, John
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallografi.
    Odqvist, Joakim
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallografi.
    Microstructure, grain size distribution and grain shape in WC-Co alloys sintered at different carbon activities2014Ingår i: International Journal of Refractory Metals and Hard Materials, ISSN 0958-0611, Vol. 43, s. 205-211Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The properties of cemented carbides strongly depend on the WC grain size and it is thus crucial to control coarsening of WC during processing. The aim of this work was to study the effect of sintering at different carbon activities on the final microstructure, as well as the coarsening behavior of the WC grains, including the size distribution and the shape of WC grains. These aspects were investigated for five WC-Co alloys sintered at 1410 C for 1 h at different carbon activities in the liquid, in the range from the graphite equilibrium (carbon activity of 1) to the eta (M6C) phase equilibrium (carbon activity of 0.33). The grain size distribution was experimentally evaluated for the different alloys using EBSD (electron backscatter diffraction). In addition, the shape of the WC grains was evaluated for the different alloys. It was found that the average WC grain size increased and the grain size distribution became slightly wider with increasing carbon activity. Comparing the two three-phase (WC-Co-eta and WC-Co-graphite) alloys a shape change of the WC grains was observed with larger grains having more planar surfaces and more triangular shape for the WC-Co-graphite alloy. It was indicated that in alloys with a relatively low volume fraction of the binder phase the WC grain shape is significantly affected by impingements. Moreover, after 1 h of sintering the WC grains are at a non-equilibrium state with regards to grain morphology.

  • 160.
    Borgh, Ida
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallografi.
    Norgren, Susanne
    Borgenstam, Annika
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallografi.
    Ågren, John
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallografi.
    Influence of nitrogen Gas pressure on the miscibility Gap in the Ti-Zr carbonitride system2012Ingår i: International Journal of Refractory Metals and Hard Materials, ISSN 0263-4368, Vol. 32, s. 11-15Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The microstructure of cemented carbides with a gradient structure at the surface consists of WC, cubic carbonitrides and a binder phase. The carbonitrides can, for example, consist of Ti(C,N)-Zr(C,N) where it is reasonable to believe that there is a miscibility gap with Ti-rich and Zr-rich carbonitrides. In the present work, the effect of the N-2-gas pressure on the equilibrium composition of the miscibility gap in the (Ti,Zr)(C,N) system has been investigated. In the study, the carbonitride system is in equilibrium with: WC, liquid binder, graphite and, N-2-gas of different pressures. Both Fe and Co are used as binder phase to study the effect of the binder phase. The results verify that there is a miscibility gap in the carbonitride system and that the region of the miscibility gap will change when N is introduced. There is a critical N-2-gas pressure lower than 0.1 bar and above that pressure the compositions of the carbonitride are rather constant as a result of the formation of a surface rim.

  • 161.
    Brandberg Hurtig, Jenny
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Mikro-modellering.
    Sichen, Du
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Mikro-modellering.
    Hydrogen pick-up after vacuum degassing2015Ingår i: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 42, nr 1, s. 49-54Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The present work aimed at determining the major source for hydrogen pick-up of the steel after vacuum degassing but before casting. Samples of slag and metal were taken at different stages during ladle treatment at SSAB. Hydrogen increase after vacuum treatment was observed. Moisture contents of the industrial slags were analysed and their water capacities were calculated. It could be seen that the hydrogen increase was correlated to the amount of moisture in the slag and the water capacity. The study showed that the slag containing most water was also the heat having the largest hydrogen increase. The slag with most water had the highest water capacity. It could be concluded that the major source for hydrogen increase after degassing was due to the slag-metal reaction.

  • 162. Breidi, A.
    et al.
    Fries, S. G.
    Palumbo, M.
    Ruban, Andrei
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik. Materials Center Leoben Forschung GmbH, Leoben, Austria.
    First-principles modeling of energetic and mechanical properties of Ni-Cr, Ni-Re and Cr-Re random alloys2016Ingår i: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 117, s. 45-53Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We apply the exact-muffin-tin-orbitals (EMTO) method to investigate structural properties, formation enthalpies, mechanical stability and polycrystalline moduli in Ni-Re, Ni-Cr and Cr-Re disordered fcc, bcc and hcp phases. Substitutional disorder is treated by using the coherent potential approximation (CPA). We predict the alloy lattice parameters in good agreement with the experiment. We find a continuous softening, as a function of Cr composition, of the tetragonal shear modulus C' in fcc Ni-Cr phase indicating mechanical instability in Cr-rich Ni-Cr alloys. On the other hand, we show that the mechanical stability of fcc Ni-Re alloys persists through the whole composition range. We observe an intriguing behaviour of the Young's modulus vs. the intrinsic ductility curve in Ni-rich Ni-Re fcc phase.

  • 163. Brennhaugen, David D. E.
    et al.
    Mao, Huahai
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Termodynamisk modellering.
    Louzguine-Luzgin, Dmitri V.
    Arnberg, Lars
    Aune, Ragnhild E.
    Predictive modeling of glass forming ability in the Fe-Nb-B system using the CALPHAD approach2017Ingår i: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 707, s. 120-125Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Accurate values needed for the most commonly used indicators of good Glass Forming Ability (GFA) in alloys, i.e. the liquidus (T-l), crystallization (T-x) and glass transition (T-g) temperatures, are only available after successful production of the metallic glass of interest. This has traditionally made discovery of new metallic glasses an expensive and tedious procedure, based on trial-and-error methodology. The present study aims at testing the CALPHAD (Computer Coupling of Phase Diagrams and Thermochemistry) approach for predicting GFA in the Fe-Nb-B system by the use of the Thermo-Calc software and the thermodynamic database TCFE7. The melting temperatures and phase stabilities were calculated and combined with data for an atomic size mismatch factor, lambda, in order to identify and map potential high-GFA regions. Selected compositions in the identified regions were later produced by suction casting and melt spinning, and the potential success verified using X-Ray Diffraction (XRD). Differential Scanning Calorimetry (DSC) was also used to compare thermodynamic calculations for the model predictions, and evaluate standard GFA indicators. The model is found to fit well with literature data, as well as predict new bulk glassy compositions at and around Fe70.5Nb7B22.5. These results show promise in further predictive use of the model.

  • 164.
    Briland, Ida
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Reduction kinetics of regenerated iron oxide from scale with hydrogen: Reduction kinetics related to the Flash Ironmaking technology2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Möjligheten och reduktionsgraden av regenererad järnoxid från glödskal kopplat till FIM-tekniken (Flash ironmaking) har studerats. Det finns lovande miljöfördelar med att minska järnoxiden med FIM-teknik som ett alternativ till BF-processen. Det finns lite information om reduktion av fint pulver med FIM eftersom tekniken är under utveckling. Att reducera järnoxid från glödskal med väte i FIM är attraktiva, därför att glödskal är en stor biprodukt på 33 miljoner ton per år som produceras över hela världen. Reduktionskinetiken för regenererad järnoxid från glödskal med en partikelstorlek av 0,56 um reducerad med väte utvärderades. Materialet reducerades i en LFR inom temperaturintervallet 600-900 ° C, partialtryck av H2 inom 0,1-0,6 atm och uppehållstid inom 1,5-7,5 s. Den kemiska sammansättningen av proverna analyserades med ICP-OES. Över 90% reduktionsgrad uppnåddes med en metalliseringsgrad av 94%. Det var uppenbart att temperaturen, partialtrycket av H2 och uppehållstiden påverkade reduktionshastigheten. Reduktionshastigheten kan beskrivas med en kärnbildnings- och tillväxthastighetsekvation med en Avrami-parameter på 0,5, partialtryckberoende av 1,4 och aktiveringsenergin 137 kJ / mol. Reduktionsgraden uppnådde tillräcklig nivå för att fastställa att FIM-tekniken kan bli en reduktionsprocess för glödskal i framtiden.

  • 165.
    Broberg, Gunnar
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Investigation of the Continuous Casting Initialisation of Duplex 22052019Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Den här uppsatsen har fokuserat på hur icke-stationära parametrar förändras med tiden viduppstarten av stränggjutningen samt hur dessa påverkar den gjutna produkten. Uppstartenav stränggjutningen är komplex och den påverkar kvaliteten på den gjutna produkten. Entabell som visar hur lång tid det tar för parametrar relaterade till uppstarten avstränggjutningen att nå stationärt tillstånd har tagits fram. Idag saknas detaljerad data för hurtotala syrehalten och inneslutningsbilden i stålet förändras under uppstarten avstränggjutningen. Därför har det icke-stationära beteendet under uppstarten avstränggjutningen kartlagts för den totala syrehalten och inneslutningarna i det duplexa stålet2205. Utöver kartläggningen, så har även användningen av ett extra långt skyddsrörundersökts, med syfte att minska den icke-stationära tiden för totala syrehalten.Undersökning var begränsad till provtagning i gjutlådan. Stålprover i gjutlådan togs från fleracharger och från gjutna slabs. Vidar så togs även två prover från ett valsat band, ett med enkantspricka och ett utan. Proverna från gjutlådan analyserades för totala syrehalten med LECOTC600 och inneslutningarna analyserades med OES/PDA. Proverna från gjutna slabsen och detvalsade bandet analyserades med SEM för inneslutningar. Resultaten visade att ståletgenomgår en reoxidation under fyllningen av gjutlådan. I genomsnitt så ledde reoxidationentill en 3,4 gångers ökning av den totala syrehalten jämfört med skänkugnsnivån. Resultatenvisar även att 50 ton måste gjutas för att syrenivån ska återgå till skänkugnsnivån. Därtill visaranalysen av inneslutningarna att reoxidationen både bidrar till fler och förändrar kemisksammansättning. Liknande kemisk sammansättning påträffades i prover från gjutlådan och idet valsade band provet med en kantspricka. Slutligen så kunde det visas att användningen avett extra långt skyddsrör minskade reoxidationen med i snitt 12 procent.

  • 166.
    Broberg, Gunnar
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Ahlbäck, Anton
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Wirhed, Oliver
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Study of an innovative ladle shroud to decrease slag carry over due to vortex formation2017Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
  • 167.
    Brusewitz Lindahl, Bonnie
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Termodynamisk modellering.
    Liu, Xuan L.
    Liu, Zi-Kui
    Selleby, Malin
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Termodynamisk modellering.
    A thermodynamic re-assessment of Al-V toward an assessment of the ternary Al-Ti-V system2015Ingår i: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, Vol. 51, s. 75-88Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Titanium alloys are highly sought after due to their excellent mechanical properties. One of the most commonly used Ti alloys is Ti-6Al-4V, which contains 6% Al and 4% V by weight. Despite the popularity of this alloy, no thermodynamic description of the ternary Al-Ti-V system has been published in the open literature. In this work an assessment procedure of the ternary Al-Ti-V system was initiated based on the binary descriptions by Witusiewitcz et al. (J. Alloys Compds. 465 (2008) 64-77 [1]) for (Al-Ti), Gong et al. (Int. J. Mater. Res. 95 (2004) 978-986 [2]) for (Al-V) and Saunders (COST 507, 2 (1998) 297-298 [3]) for (Ti-V). When combining the three binary systems and looking at the extrapolated ternary isothermal sections, it was found that there was a very large miscibility gap in the bcc phase. The origin of this miscibility gap was mainly the Al-V system and therefore it was decided to reassess this system. The Al-V system was reassessed according to available experimental data along with the enthalpies of formation of all compounds as well as the enthalpies of mixing for all terminal phases obtained by first-principles calculations based on the density functional theory. For the Al8V5 phase there are two different sets of data for the enthalpies of formation. These two sets are investigated in this work and it is found that the set not used by Gong et al. in their assessment of the Al-V binary system gives better extrapolations. The final description produced improved extrapolated ternary isothermal sections.

  • 168.
    Bu, Junfu
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jönsson, Pär G.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Zhao, Z.
    Transport properties of BaZr0.5Ce0.3Y0.2O3-δ proton conductor prepared by spark plasma sintering2016Ingår i: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 42, nr 3, s. 4393-4399Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Dense BaZr0.5Ce0.3Y0.2O3-δ (BZCY532) proton conductors were prepared by a spark plasma sintering method. Their conductivities were determined in different atmospheres: dry air, wet N2 and wet H2. Moreover, the potential electronic conductivity contribution to the total conductivity was also identified by testing their total conductivities at different oxygen partial pressures (1-10-24 atm) in combination with an XPS analysis. It is found that the prepared dense BZCY532 ceramics are good proton conductors at 600 °C. In addition, the Ce3+ concentration in the dense BZCY532 ceramics is around 3.5 atm% of the total Ce element, and the electronic contribution to the total conductivity can be neglected after a postheat treatment.

  • 169.
    Bu, Junfu
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jönsson, Pär G.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Zhao, Zhe
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    BaZr0.5Ce0.3Ln0.2O3-δ(Ln=Y, Sm, Gd, Dy) based electrolytes used for intermediate temperature solid oxide fuel cellsManuskript (preprint) (Övrigt vetenskapligt)
  • 170.
    Bu, Junfu
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jönsson, Pär G.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Zhao, Zhe
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Yttrium doped hafnium oxide Hf0.69Y0.31O2-δ used for solid oxide fuel cell electrolytes and electronic materialsManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    An Yttrium doped hafnium oxide Hf0.69Y0.31O2-δ (YSH orYDH) is obtained by a modified solid state reactionmethod, where freeze drying is implemented to reduce theagglomeration. Refinement result shows that YSH is influorite cubic crystal with lattice parameter a = b = c =5.140674 Å (Figure 1). Based on this, the ionic radius ofY3+ in YSH for 8 coordination is 0.1006 nm, confirms theprevious prediction that it should be smaller than 0.1015nm. The YSH ceramic material with relative density of>97.5% can be obtained by conventional sintering at 1650℃ for 10hrs. Its conductivity is only 3.65×10-5 s cm-1 at700 ℃ (Figure 2), which is too low for solid oxide fuelcell application. However, its high dielectric constant22.03 (Figure 3a, average value, which is 1.4 times largerthan the pure Hafnia) and low dielectric loss over a widefrequency range and DC potential make it very promisingfor the microelectronic device application.

  • 171.
    Bu, Junfu
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Jönsson, Pär Göran
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Zhao, Zhe
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap. Shanghai Institute of Technology, China.
    Electrical conductivities of translucent BaZr(X)Ce0.8-XY0.2O3-delta (x=0.5, 0.6, 0.7) ceramics2016Ingår i: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 115, s. 87-90Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The electrical conductivities of translucent BaZr0.5Ce0.3Y0.2O3-delta (x = 0.5, BZCY532), BaZr0.6Ce0.2Y0.2O3-delta (x = 0.6, BZCY622) and BaZr0.7Ce0.1Y0.2O3-delta(x = 0.7, BZCY712) proton conductors were investigated systematically in different atmospheres and also at different oxygen partial pressures. The obtained results indicate that translucent BZCY532, BZCY622 and BZCY712 ceramics are pure oxygen-ion and proton conductors without unfavorable electronic conduction. In addition, they represent promising proton conductors to be used as intermediate temperature solid oxide fuel cell electrolytes.

  • 172.
    Bubenko, Clara
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Magnil, Karl
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Olofsson, Melker
    An Investigation of Stainless Steels for Long-term Use in Liquid Sodium at up to 700°C2019Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Det svenska företaget Azelio har utvecklat en stirlingmotor som drivs av solenergi. Då tillgången på solenergi är begränsad till dagtid har Azelio också utvecklat en termisk lagringsenhet (TES). Den termiska lagringsenheten absorberar och lagrar solenergi och kan därmed förse stirlingmotorn med värme även under natten. Stirlingmotorn driver i sin tur en generator vilken producerar elektricitet under hela dygnet. Natrium används som värmeledningsfluid (HTF) mellan TES och stirlingmotorn, vid temperaturer över 600°C. Vid dessa temperaturer är natrium högreaktivt och fenomen såsom kryp och korrosion kan uppstå, vilka kan påverka egenskaperna hos omgivande material. Genom att jämföra högtemperaturstålet 253 MA med andra kommersiella stål, eftersöks en kvalificerad och prisvärd legering som kan motstå flytande natrium vid dessa temperaturer. Från en omfattande litteraturstudie skapades en lista med möjliga kandidater. Materialen analyserades sedan i huvudsak utifrån ingående legeringselements påverkan på dess egenskaper. Analysen visar på att 153 MA har några betydande fördelar jämfört med 253 MA, såsom en mer stabil mikrostruktur vid de angivna temperaturerna. Detta arbete rekommenderar därför 153 MA för vidare undersökning och testning.

  • 173.
    Buffington, Jack
    KTH, Skolan för industriell teknik och management (ITM), Industriell ekonomi och organisation (Inst.), Industriell marknadsföring.
    The Beverage Can in the United States: Achieving a 100% Recycled Aluminum Can through Supply Chain Innovation2012Ingår i: JOM: The Member Journal of TMS, ISSN 1047-4838, E-ISSN 1543-1851, Vol. 64, nr 8, s. 923-932Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The purpose of this research is to analyze why recycled content is low (33-50%) in the aluminum can in the United States when it is technically possible to have a product that is made from 100% recycled material. A comprehensive literature review is conducted, followed by identification of five propositions determined with respect to the research problem. With respect to aluminum can recycling (and its research), there is a greater focus on the role of the consumer than the producer in the aluminum can supply chain system, which may impact on the role of innovation in addressing the problem. The upstream primary aluminum supply chain is vertically integrated and efficient within itself, but not integrated with the downstream secondary aluminum can market. Given the importance of the secondary aluminum market in the United States, there are significant recycling/efficiency/sustainability opportunities to address. As opposed to a dominant focus on consumers and their recycling habits, this study focuses on the aggregate aluminum can supply chain to apply innovation to the solution.

  • 174.
    Buffington, Jack
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Industriell ekonomi och organisation (Inst.), Industriell marknadsföring.
    Peterson, Ray
    Defining a Closed-Loop US Aluminum Can Supply Chain Through Technical Design and Supply Chain Innovation2013Ingår i: JOM: The Member Journal of TMS, ISSN 1047-4838, E-ISSN 1543-1851, Vol. 65, nr 8, s. 941-950Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The purpose of this study is to conduct a supply chain material flow analysis (MFA) for the U.S. aluminum can market, consistent with studies conducted for the overall worldwide aluminum industry. A technical definition of the use of alloys 5182 and 3104 is conducted by metallurgists for use in the "aluminum can" MFA. Four propositions are created: technical, economic, and supply chain factors are as important to secondary aluminum recycling in an aluminum can as higher recycling rates (P-1); the development of a unialloy aluminum can will increase reuse rates, but recycling rates must increase for this to happen (P-2); a closed-loop aluminum can supply chain is not able to be fully realized in today's environment but is very useful for understanding improvement through both supply and demand (P-3); and UBC supply can improve through a "voluntary deposit-refund system" approach (P-4).

  • 175.
    Buffington, John
    KTH, Skolan för industriell teknik och management (ITM), Industriell ekonomi och organisation (Inst.), Industriell marknadsföring.
    The Viability of a "Voluntary Refund-Deposit System" for Aluminum Can Recycling in the U.S.2014Ingår i: Light Metals 2014, Wiley-Blackwell, 2014, s. 913-918Kapitel i bok, del av antologi (Övrigt vetenskapligt)
    Abstract [en]

    The concept of a voluntary deposit system is developed and modeled in this paper in comparison to the current state of a voluntary non-deposit (R<inf>1</inf>) and mandatory refund-deposit (R<inf>2</inf>) hybrid system in the U.S. The R<inf>3</inf> model is found to be optimal in comparison through an increase in the recycling rate, a reduction in operating costs, and the creation of a larger surplus to be used to pay for an IT-based tracking system and research grants to enable future innovations in the collection and processing of recyclables. In the R<inf>3</inf> model, consumers are only burdened if they choose to not recycle, or they wish to have the convenience of curbside pick-up.

  • 176.
    Bölke, Kristofer
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    IRONARC; a New Method for Energy Efficient Production of Iron Using Plasma Generators2015Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The most widely used process to reduce iron ore and to produce pig iron is the blast furnace. The blast furnace is a large source of CO2 emissions since it is a coal based process and due to that the main energy source and reducing agent is coke, it is difficult to reduce these further. IRONARC is a new method used to produce pig iron by reducing iron ore and all the energy used for heating comes from electricity, which gives the opportunity to use renewable resources. The process uses plasma generators that inject gas at high temperature and velocity into a slag that consists of iron oxides. The iron oxides are reduced in two steps that appear by using gas as reduction agent in the first step and carbon in the second step.   It exists in a smaller pilot plant scale and this project was the first step in the future upscaling of the IRONARC process.

    Computational Fluid Dynamics (CFD) modelling was used and the goal was to determine the penetration depth of the IRONARC pilot plant process by numerical simulation in the software ANSYS FLUENT. The penetration depth is of importance because to be able to scale up the process it is important to know the flow pattern and the structure of the flow in the process, which is dependent on how far into the slag the gas reaches.

    Two numerical models were made. First an air-water model that described the initial penetration of air injected into water. The air-water simulation was made with parameters and data from an experiment found in literature. This was done to build an accurate CFD model for the penetration depth in FLUENT and validate the model with the results of the penetration depth from the experiment. The air-water simulation gave good and promising results and yielded the same result regarding the penetration depth as the experiment.  The model for the penetration depth was then used with the IRONARC geometry and parameters. After simulation the penetration depth of the IRONARC process was determined. For the future, the penetration depth of the pilot plant needs to be measured and compared with the simulated result for the penetration depth. 

  • 177.
    Bölke, Kristofer
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Ersson, Mikael
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Imris, Matej
    ScanArc Plasma Technol AB, SE-81321 Hofors, Sweden..
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Importance of the Penetration Depth and Mixing in the IRONARC Process2018Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 58, nr 7, s. 1210-1217Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    One of the most important parameters for gas injection into liquid baths is the penetration depth of the gas into the bath. This is due to that it strongly influences the flow structure and hence the stirring and plume behavior in metallurgical processes. The IRONARC process is a new energy efficient process for reduction of iron oxide to produce pig iron. The future goal is to continuously scale up the process to an industrial scale from the current pilot scale. In this process, gas is injected horizontally through a submerged nozzle into a slag bath. Hence, the penetration depth is of great importance since it greatly affect several parameters in this process. Moreover, this information is essential when scaling up the reactor from a pilot scale to an industrial scale. In this work, the penetration depth of gas injection into water in a small scale side blown converter was studied numerically. Two different approaches with different multiphase models were tested, namely the Volume of Fluid (VOF) model and Eulerian multiphase model (EE). The penetration depth could be accurately determined for both numerical models, with a small expected deviation of 13.9% from the physical experiment results. Also, the simulation time was shorter for the Eulerian multiphase model. The penetration depth was then determined for the IRONARC pilot plant process. The results show that the plume is detached from the nozzle wall, which in turn results in a better energy usage of the gas along with a small refractory wear.

  • 178.
    Cao, Weimin
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Theoretical and experimental studies of surface and interfacial phenomena involving steel surfaces2010Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The present work was initiated to investigate the surface- and interfacial phenomena for iron and slag/iron systems. The aim was to understand the mechanism of the effect of surface active elements on surface and interfacial properties. In the present work, the adsorption of oxygen and sulfur on iron surface as well as adatom surface movements were studied based on the ab initio method. BCC iron melting phenomena and sulfur diffusion in molten iron were investigated by Monte Carlo simulations. The impact of oxygen potential on interfacial mass transfer was carried out by X-ray sessile drop method.

    Firstly, the structural, electronic and magnetic properties as well as thermodynamic stability were studied by Density functional theory (DFT). The hollow site was found to be the most stable adsorption site both for oxygen and sulfur adsorbed on iron (100) surface, which is in agreement with the experiment. The relaxation geometries and difference charge density of the different adsorption systems were calculated to analyze the interaction and bonding properties between Fe and O/S. It can be found that the charge redistribution was related to the geometry relaxation. In addition, the sulfur coverage is considered from a quarter of one monolayer (1ML) to a full monolayer. It was found that the work function and its change Δφ increased with S coverage, in very good agreement with experiment. Due to a recent discussion regarding the influence of charge transfer on Δφ, it is shown in the present work that the increase in Δφ can be explained by the increasing surface dipole moment as a function of S coverage. S strongly interacts with the surface Fe layer and decreases the surface magnetic moment as the S coverage increases.

    Secondly, a two dimensional (2D) gas model based on density functional calculations combined with thermodynamics and statistical physics, was proposed to simulate the movement of the surface active elements, viz. oxygen and sulfur atoms on the Fe(100) surface. The average velocity of oxygen and sulfur atoms was found to be related to the vibration frequencies and energy barrier in the final expression developed. The calculated results were based on the density function and thermodynamics & statistical physics theories. In addition, this 2D gas model can be used to simulate and give an atomic view of the complex interfacial phenomena in the steelmaking refining process.

    A distance dependent atomistic Monte Carlo model was developed for studying the iron melting phenomenon as well as effect of sulfur on molten iron surface. The effect of boundary conditions on the melting process of an ensemble of bcc iron atoms has been investigated using a Lennard-Jones distance dependent pair potential. The stability of melting process was energetically and spatially analyzed under fixed wall and free surface conditions and the effects of short and long-range interactions were discussed. The role of boundary conditions was significantly reduced when long-range interactions were used in the simulation. This model was further developed for investigating the effect of sulfur on molten iron surface. A combination of fixed wall and free surface boundary condition was found to well-represent the molten bath configuration while considering the second nearest neighbor interactions. Calculations concerning the diffusion of sulfur on molten surface were carried out as a function of temperature and sulfur concentration. Our results show that sulfur atoms tended to diffuse away from the surface into the liquid bulk and the diffusion rate increased by increasing temperature.

    Finally, impact of oxygen potential on sulfur mass transfer at slag/metal interface, was carried out by X-ray sessile drop method. The movement of sulfur at the slag/metal interface was monitored in dynamic mode at temperature 1873 K under non-equilibrium conditions. The experiments were carried out with pure iron and CaO-SiO2-Al2O3-FeO slag (alumina saturated at the experimental temperature) contained in alumina crucibles with well-controlled partial pressures of oxygen and sulfur. As the partial pressure of oxygen increased, it was found that interfacial velocity as well as the oscillation amplitude increased. The thermo-physical and thermo-chemical properties of slag were also found to influence interfacial velocity.

     

  • 179.
    Cao, Weimin
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Using and validation of the DFT method for oxygen adsorbed on the iron (100) surface2010Ingår i: Transactions of the Institution of Mining and Metallurgy Section C - Mineral Processing and Extractive Metallurgy, ISSN 0371-9553, E-ISSN 1743-2855, Vol. 119, nr 2, s. 67-70Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Electronic and structural properties of atomic oxygen adsorbed on the iron (100) surface are examined using density functional theory calculations. The oxygen adsorbed on the iron (100) surface is investigated at the three adsorption sites top, bridge and hollow sites respectively. Adsorption energy, work function and surface geometries were calculated, the hollow site was found to be the most stable adsorption site, which is in agreement with the experiment. In addition, the difference charge density of the different adsorption system was calculated to analyse the interaction and bonding properties between Fe and O. It can be found out that the charge redistribution was related to the geometry relaxation. The calculated results are compared with the experimental and other theoretical results.

  • 180.
    Cao, Weimin
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Delin, Anna
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Calculation of Oxygen and Sulfur Average Velocity on the Iron Surface: A Two-dimensional Gas Model Study2010Ingår i: Steel Research International, ISSN 1611-3683, Vol. 81, nr 11, s. 949-952Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the present work, a two-dimensional (2D) gas model is derived and used to simulate the average velocity of individual atoms of the surface active elements oxygen and sulfur on the Fe(100) surface. The average velocity of oxygen and sulfur atoms was found to be related to the vibration frequencies and minimal energy barrier. The calculated results are based on data from density functional calculations combined with thermodynamics and statistical physics. The calculated average velocity of oxygen on the Fe (100) is lower than that of sulphur. This is because of the stronger interaction between oxygen and the first iron layer. We conclude that our simple 2D gas model may be useful for simulating and understanding the complex interfacial phenomena in the steelmaking refining process from an atomic point of view.

  • 181.
    Cao, Weimin
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Muhmood, Luckman
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Sulfur Transfer at Slag/Metal Interface-Impact of Oxygen Potential2012Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 43, nr 2, s. 363-369Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the present work, the interfacial movement resulting from sulfur mass transfer at the slag/metal interface was monitored by X-ray sessile drop method in dynamic mode at temperature 1873 K (1600 A degrees C) under nonequilibrium conditions. The experiments were carried out with pure iron and CaO-SiO2-Al2O3-FeO slag (alumina saturated at the experimental temperature) contained in alumina crucibles with well-controlled partial pressures of oxygen and sulfur. The impact of oxygen potential on the droplet oscillation as sulfur from the gas phase reaches the metal drop through the intermediate slag phase was monitored. The interfacial velocity was investigated. It was found that the increases of interfacial velocity and the maximum oscillation time were mainly attributed to the partial pressure of oxygen increases. The experiment results were explained by previous ab initio calculations. The thermo-physical and thermo-chemical properties of slag were also found to influence interfacial velocity.

  • 182.
    Carlsson, Leo
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Using Multilayer Perceptrons asmeans to predict the end-pointtemperature in an Electric ArcFurnace2015Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
  • 183.
    Carlsson, Leo
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Samuelsson, Peter
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Jönsson, Pär G.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Using statistical modeling to predict the electrical energy consumption of an electric arc furnace producing stainless steel2020Ingår i: Metals, ISSN 2075-4701, Vol. 10, nr 1, artikel-id 36Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The non-linearity of the Electric Arc Furnace (EAF) process and the correlative behavior between the process variables impose challenges that have to be considered if one aims to create a statistical model that is relevant and useful in practice. In this regard, both the statistical modeling framework and the statistical tools used in the modeling pipeline must be selected with the aim of handling these challenges. To achieve this, a non-linear statistical modeling framework known as Artificial Neural Networks (ANN) has been used to predict the Electrical Energy (EE) consumption of an EAF producing stainless steel. The statistical tools Feature Importance (FI), Distance Correlation (dCor) and Kolmogorov–Smirnov (KS) tests are applied to investigate the most influencing input variables as well as reasons behind model performance differences when predicting the EE consumption on future heats. The performance, measured as kWh per heat, of the best model was comparable to the performance of the best model reported in the literature while requiring substantially fewer input variables.

  • 184.
    Carlsson, Sofia
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Grain refinement of aluminium by titanium diboride particles: The importance of nucleation, growth restriction, and cooling rate2019Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Kornförfining av aluminium med titandiboridpartiklar, TiB2, genom användning av Ti/B kornförfinare är standard inom aluminiumindustrin. Det är dock inte helt utrett hur denna kornförfining går till. Rådande tillsatsmängder av kornförfinare är därför sällan optimala och alltför stora tillsatsmängder av kornförfinare är vanligt förkommande. Denna studie undersöker kornförfining av aluminium med titandiborid med målet att skapa en metod och/eller modell som kan användas för att underlätta optimering av tillsatsmängder. Fokus ligger på hur olika parametrar influerar kornförfiningen och inkluderar kylningshastighet, egenskaperna hos de kärnbildande partiklarna, och tillväxthämning. Experiment med olika testmetoder utfördes för att undersöka detta. Studien visar hur de undersökta parametrarna påverkar kornförfiningen och hur dessa kan användas till att optimera tillsatsmängden av kornförfinare. En modell användbar för att hantera de skillnader nominellt identiska kornförfinare uppvisar i sin förmåga att producera korn presenteras. Slutsatsen betonar vikten av att optimera tillsatsmängden av kornförfinare, både av materialmässiga och miljömässiga skäl, och hur detta kan uppnås genom ändringar i undersökta parametrar.

  • 185. Cedervall, Johan
    et al.
    Andersson, Mikael Svante
    Sarkar, Tapati
    Delczeg-Czirjak, Erna K.
    Bergqvist, Lars
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Materialfysik, MF. KTH, Centra, SeRC - Swedish e-Science Research Centre.
    Hansen, Thomas C.
    Beran, Premysl
    Nordblad, Per
    Sahlberg, Martin
    Magnetic structure of the magnetocaloric compound AlFe2B22016Ingår i: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 664, s. 784-791Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The crystal and magnetic structures of AlFe2B2 have been studied with a combination of X-ray and neutron diffraction and electronic structure calculations. The magnetic and magnetocaloric properties have been investigated by magnetisation measurements. The samples have been produced using high temperature synthesis and subsequent heat treatments. The compound crystallises in the orthorhombic crystal system Cmmm and it orders ferromagnetically at 285 K through a second order phase transition. At temperatures below the magnetic transition the magnetic moments align along the crystallographic a-axis. The magnetic entropy change from 0 to 800 kA/m was found to be - 1.3 J/K kg at the magnetic transition temperature.

  • 186.
    Cendekia, Bintang Bergas
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi. KTH Royal Institute of technology.
    The Effect of Electromagnetic Stirring and Flow Control Devices on Eight-Strand Tundish Performance2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The strand similarity and inclusion removal capability are two critical parameters to measure the performance of multi-strand tundish in clean steel production. In this work, the effect of two flow regulators, i.e., Flow Control Devices (FCD) and Electromagnetic Stirring (EMS) on eight-strand tundish performance have been investigated by establishing a water model and conducting numerical simulations of water model. The water model was focused on revealing the effect of stirring while the simulation was employed to investigate the effect of two FCDs, namely baffle wall and turbo-stopper. The analysis of strand similarity and inclusion removal were conducted by analyzing flow characteristics derived from Combined Model of Residence Time Distribution (RTD) curve and observing the flow movement in the tundish model. In addition, the tundish capability to remove inclusions was also studied by injecting inclusion particles using Discrete Phase Model (DPM) in ANSYS Fluent. Experiment results cause the Combined Model needs to be modified. This modification was employed when analyzing tundish configuration involving stirring. By using the modified Combined Model, the stirring can significantly increase the well-mix volume to almost 100% as it annihilates dead zone. The stirring also increases the similarity between strands and makes the RTD curve more similar to ideal mixing curve.  However, the problem of short-circuiting flow need to be solved and care should be taken into consideration regarding the selection of stirring direction as well as bath surface condition when implementing EMS in reality. The simulation results show that the addition of baffle wall and turbo-stopper are beneficial to improve mixing as well as to avoid the short-circuiting flow. Furthermore, compared to individual FCD, the combination of baffle wall and turbo-stopper results in the best performance to remove inclusions by providing surface-directed flow and generating a higher plug flow.

  • 187.
    Chandrasekaran, Dilip
    et al.
    KTH, Tidigare Institutioner, Materialvetenskap.
    Nygårds, Mikael
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    A study of the surface deformation behaviour at grain boundaries in an ultra-low-carbon steel2003Ingår i: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 51, nr 18, s. 5375-5384Artikel i tidskrift (Refereegranskat)
  • 188.
    Chang, Tingru
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Yt- och korrosionsvetenskap.
    Herting, Gunilla
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Yt- och korrosionsvetenskap.
    Goidanich, S.
    Sánchez Amaya, J. M.
    Arenas, M. A.
    Le Bozec, N.
    Jin, Y.
    Leygraf, Christopher
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Yt- och korrosionsvetenskap.
    Odnevall Wallinder, Inger
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Yt- och korrosionsvetenskap.
    The role of Sn on the long-term atmospheric corrosion of binary Cu-Sn bronze alloys in architecture2019Ingår i: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 149, s. 54-67Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The role of Sn on the atmospheric corrosion performance of binary Cu-Sn bronze alloys (4–6 wt.% Sn) compared with Cu metal used in outdoor architecture is elucidated in terms of microstructure, native surface oxide composition, patina evolution, corrosion rates, appearance and metal release. Results are presented for non-exposed surfaces and surfaces exposed at different urban and marine sites in Europe up to 5 years and based on multi-analytical findings from microscopic, spectroscopic, electrochemical and chemical investigations. Alloying influenced the corrosion, aesthetic appearance and patina evolution, differently for urban and marine sites, whereas no effects were observed on the release pattern.

  • 189.
    Chang, Tingru
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap. Univ Sci & Technol Beijing, Natl Ctr Mat Serv Safety, Beijing 100083, Peoples R China.
    Herting, Gunilla
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Jin, Ying
    Univ Sci & Technol Beijing, Natl Ctr Mat Serv Safety, Beijing 100083, Peoples R China..
    Leygraf, Christofer
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Odnevall Wallinder, Inger
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    The golden alloy Cu5Zn5Al1Sn: Patina evolution in chloride-containing atmospheres2018Ingår i: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 133, s. 190-203Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The influence of chloride deposition on the formation, evolution and barrier properties of the patina formed on CuSZn5Al1Sn used for architectural cladding is explored via long-term marine field exposures and laboratory investigations. The presence of Cu2O, ZnO, Al2O3 and SnO2 within the inner part of the patina and intercalation of SnO2, Zn-5(CO3)(2)(OH)(6), Zn6Al2(OH)(16)CO3 center dot 4H(2)O, Zn-5(OH)(8)Cl-2 center dot H2O within its outer part, predominantly composed of Cu-2(OH)(3)Cl, significantly reduce the chloride-induced corrosion compared with Cu metal. The intercalation of zinc-rich corrosion products within the patina and not at the top-surface explain their marginal influence on the runoff process that mainly occurs at the outmost surface.

  • 190.
    Chang, Tingru
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Yt- och korrosionsvetenskap. University of Science and Technology Beijing, China.
    Wallinder, Inger Odnevall
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Yt- och korrosionsvetenskap.
    Jin, Ying
    Leygraf, Christofer
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemi, Yt- och korrosionsvetenskap.
    The golden alloy Cu-5Zn-5Al-1Sn: A multi-analytical surface characterization2018Ingår i: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 131, s. 94-103Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The golden alloy Cu-5Zn-5Al-1Sn has found many applications because of its appearance and resistance to tarnishing. The microstructure and multi-component surface oxide of Cu-5Zn-5Al-1Sn have been investigated through a multi-analytical approach. Compared to commercial Cu metal, Cu-5Zn-5Al-1Sn has significantly smaller grains and higher fraction of coherent twin boundaries. The 5-10 nm thick oxide formed after diamond polishing has four identified sub-oxides all contributing to the overall corrosion resistance. Cu2O is mainly located in the outer part, followed by ZnO, SnO2 and Al2O3 closer to the alloy substrate. The latter three possess barrier properties, while Cu2O exhibits a more complex structure.

  • 191.
    Chang, Zhongwen
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Multiscale modelling of radiation-enhanced diffusion phenomena in metals2015Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    A multiscale modelling framework and an experiment campaign are used to study void swelling and Cu precipitation under irradiation. Several aspects regarding defect and solute diffusion under irradiation have been studied in this thesis.

    First, a self-diffusion model in bcc Fe has been constructed in order to describe the non-linear effects, especially the magnetic transition, around the Curie temperature. First principles calculations are applied to obtain the parameters in the model. The paramagnetic state is simulated by statistical sampling of randomly arranged spin states on each atom. The model fits well with the experimental observations.

    Then, a combination of atomistic calculations and the finite element method (FEM) is developed in order to solve the diffusion equations of point defects, which are under the influence of a dislocation strain field. The dislocation bias, a key parameter in void swelling models, is hence obtained numerically. The method has been applied in different structural lattices. In the bcc materials, anomalous bias factors have been found for both edge- and screw dislocations. For the edge dislocations, the traditional assumption that the dislocation bias value is proportional to the Burgers vector has been proven not appropriate. For the screw dislocation, a negative bias value is obtained. This implies that vacancies, instead of self-interstitials, are preferentially absorbed into the screw dislocations. Thus a possible complementary mechanism is here introduced for explaining the long swelling incubation time before the steady swelling in bcc materials compared to that in fcc materials.

    Edge dislocations in fcc materials split into partial dislocations due to their  relatively low stacking fault energy. This feature complicates the analytical derivation of the dislocation bias. However, by transforming the analytical dislocation-point defect interaction energies to discrete interaction maps numerically applied in the FEM method, it is possible to perform a systematic study on typical fcc materials, i.e. Cu, Ni and Al. The impacts on the dislocation bias from elastic constants and stacking fault energy have been studied. It is found that the partial splitting distance is the dominating factor that determines the dislocation bias. A prediction method has been hence developed to obtain the dislocation bias of the austenitic alloys, for which it is difficult to use an atomistic description of the interaction maps. A prediction of about 8% dislocation bias of a typical austenitic 316 alloy has been made without performing specific atomistic calculations in the austenitic alloys.

    Finally, Cu precipitation under irradiation has been studied using both experiment and simulations. Cast iron and FeCu alloy samples were irradiated for a week with 2 MeV electrons. The resistivity of the samples was measured in situ. The microstructure of the samples was then examined by atom probe tomography. No Cu precipitation was found in the cast iron sample while small Cu clusters are observed in the FeCu model alloy. To simulate the clustering process, Kinetic Monte Carlo (KMC) and rate theory methods are used. Both the KMC and rate theory simulations show clearly the Cu clustering process in the FeCu alloy but not in cast iron within the irradiation dose.

  • 192.
    Chang, Zhongwen
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Messina, Luca
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Sandberg, Nils
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Yousfi, Amine
    Toijer, Elin
    Thuvander, Mattias
    Boizot, Bruno
    Brysbaert, Gauthier
    Metayer, Vincent
    Gorse-Pomonti, Dominique
    Olsson, Pär
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Electron irradiation accelerated Cu precipitation in cast iron and an FeCu model alloyManuskript (preprint) (Övrigt vetenskapligt)
  • 193.
    Chang, Zhongwen
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Olsson, Pär
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Terentyev, D
    Nuclear Materials Science Institute, Belgium.
    Sandberg, N
    Swedish Radiation Safety Authority, Sweden.
    Multiscale calculation of dislocation bias in fcc Ni and bcc Fe model lattices2014Ingår i: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, ISSN 0168-583X, E-ISSN 1872-9584Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In order to gain more insights on void swelling, dislocation bias is studied in this work. Molecular staticsimulations with empirical potentials are applied to map the dislocation–point defects interactionenergies in both fcc Ni and bcc Fe model lattices. The interaction energies are then used to numericallysolve the diffusion equation and obtain the dislocation bias. The importance of the dislocation core regionis studied under a the temperature range 573–1173 K and the dislocation densities 1012—1015 m-2. Theresults show that larger dislocation bias is found in the fcc Ni than in the bcc Fe under differenttemperatures and dislocation densities. The anisotropic interaction energy model is used to obtain thedislocation bias and the result is compared to that obtained using the atomistic interaction model, thecontribution from the core structure is then shown in both the Ni lattice and the Fe lattice.

  • 194.
    Chang, Zhongwen
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Sandberg, Nils
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik. Swedish Radiation Safety Authority, Sweden.
    Dmitry, Terentyev
    Samuelsson, Karl
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Bonny, Giovanni
    Olsson, Pär
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Assessment of the dislocation bias in fcc metals and extrapolation to austenitic steels2015Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 465Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A systematic study of dislocation bias has been performed using a method that combines atomistic and elastic dislocation-point defect interaction models with a numerical solution of the diffusion equation with a drift term. Copper, nickel and aluminium model lattices are used in this study, covering a wide range of shear moduli and stacking fault energies. It is found that the dominant parameter for the dislocation bias in fcc metals is the width of the stacking fault ribbon. The variation in elastic constants does not strongly impact the dislocation bias value. As a result of this analysis and its extrapolation, the dislocation bias of the widely applied austenitic stainless steels of 316 type is predicted to be about 0.1 at temperature close to the swelling peak (815 K) and typical dislocation density of 1014 m-2. This is in line with the bias calculated using the elastic interaction model, which implies that the prediction method can be used readily in other fcc systems even without EAM potentials. By comparing the bias values obtained using atomistic- and elastic interaction energies, about 20% discrepancy is found, therefore a more realistic bias value for the 316 type alloy is 0.08 in these conditions.

  • 195.
    Chang, Zhongwen
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Terentyev, Dmitry
    Nuclear Materials Science Institute, Belgium.
    Sandberg, Nils
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik. Swedish Radiation Safety Authority, Sweden.
    Samuelsson, Karl
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Olsson, Pär
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Anomalous bias factors of dislocations in bcc iron2015Ingår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 461, s. 221-229Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Dislocation bias factors in bcc Fe have been calculated based on atomistic interaction energy maps on three kinds of dislocations, namely the a0/2〈1 1 1〉{1 1 0} screw, a0/2〈1 1 1〉{1 1 0} and a0〈1 0 0〉{0 0 1} edge dislocations. The results show that the dislocation bias is higher for the a0/2〈1 1 1〉 edge dislocation than for the a0〈1 0 0〉 edge dislocation, even though the latter possesses a larger Burgers vector. This indicates the importance of the dislocation core contribution. For the a0/2〈1 1 1〉{1 1 0} screw dislocation, a negative dislocation bias has been obtained, which implies a more efficient absorption of vacancies than of SIAs. The effect of coexistence of both edge- and screw dislocations are assessed by a total bias. A possible complementary mechanism for explaining the long swelling incubation time in bcc metals is suggested and discussed.

  • 196.
    Chanouian, Serg
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    What If We Tilt the AOD?: Developing a numerical and physical model of a downscaled AOD converter to investigate flow behaviour when applying an inclination.2019Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Den dominerande processen för kolfärskning vid skrot baserad rostfri ståltillverkning är AOD- processen (Argon Oxygen Decarburisation). Processen går igenom tre steg, kolfärskning, reducering av krom och svavelrening där de största utmaningarna ligger i att oxidera kol utan att oxidera krom. I praktiken gör detta genom att injicera en blandning av argon och syrgas från sidan av AOD-konvertern för att sänka partial trycket av den kolmonoxid som bildas när kol oxideras. Syftet är att göra det mer termodynamiskt fördelaktigt att oxidera kol i systemet. Den injicerade blandgasen har olika förhållanden under kolfärskning med en hög andel syrgas i början som sedan sänks genom processen tills bara argon injiceras. Tidigare studier har visat att kolfärskningen är en funktion av konverterns ålder där ju äldre en konverter är desto snabbare går kolfärskning. Enligt studierna har det visats att 8-10% mindre syrgas eller användning av reducerings medel kan uppnås i en gammal konverter vilket har väckt ett intresse för vidare studier. I detta arbete har en av två metoder prövats för att undersöka om man kan applicera det som sker i en gammal konverter till en ny. En numerisk modell av en nerskalad AOD-konverter har utvecklats och validerats mot en vattenmodell då konvertern vinklas. En 75-tons konverter nerskalades till en vattenmodell där vinklarna 0, 5.5 och 14° studerades med fokus på blandningstid och penetrations djup. Vattenmodellen gjordes om till en numerisk modell som använde Euler-Euler metoden i ANSYS Fluent. Modellerna visade likheter gällande penetrationsdjup, flödes struktur och blandnings tid men kräver en del justeringar innan en uppskalning samt koppling till termodynamisk modellering kan ske.

  • 197.
    Chen, Chao
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Some Aspects on Macroscopic Mixing in a Tundish2015Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Two aspects on macroscopic mixing in a continuous flow system – metallurgical tundish were studied. Specifically, 1) the first focus was on salt solution tracer mixing, which is important for tundish design from perspectives of tracer technology and Residence Time Distributions (RTD) as well as for the understanding of the macroscopic mixing in tundishes. The different amounts of salt solution tracer mixing in a tundish were studied by using both physical models and mathematical models. The disturbance of KCl salt tracer on the flow in the tundish with respect to different amounts is like the “butterfly effect”, i.e. only a slight increase of the amount of tracer, the flow field might be disturbed. This, in turn, will result in a shifted RTD curve. 2) The second focus was on Eulerian modeling of inclusions macroscopic transport and removal, which is important for tundish design from perspectives of inclusions removal and to provide information of macroscopic removal of inclusions. In the study, an approach that combined the meso-scale inclusions deposition at turbulent boundary layers of steel-slag interface and the macroscopic transport of inclusions in the tundish was used. The theoretical calculation results showed that the effect of the roughness on the deposition velocity of small inclusions (radius of 1 μm) were more pronounced than that for the big inclusions (up to the radius of 9 μm). The dynamic inclusions removal studies showed that the tundish with a weir and a dam exhibited a better performance with respect to the removal of bigger inclusions (radii of 5 μm, 7 μm and 9 μm) than that of the case without weirs and dams. However, the tundish without weirs and dams showed a higher removal ratio of smaller inclusions (radius of 1 μm).

  • 198.
    Chen, Chao
    et al.
    State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, China.
    Cheng, Guoguang
    State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, China.
    Sun, Haibo
    State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, China.
    Hou, Zibing
    State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, Chaina.
    Wang, Xinchao
    State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing.
    Zhang, Jiaquan
    State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, China.
    Effects of Salt Tracer Amount, Concentration and Kind on the Fluid Flow Behavior in a Hydrodynamic Model of Continuous Casting Tundish2012Ingår i: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 83, nr 12, s. 1141-1151Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The hydrodynamic modeling method that widely used to simulate the fluid flow was reconsidered and discussed in this paper. The effects of injected salt tracer amount, concentration and kind on the fluid flow behavior in a hydrodynamic model tundish were investigated. The results were compared with the mathematical modeling calculation results, that the tracer density effect was eliminated. The residence time distribution (RTD) curve of tracer introduced deviated to the left side of the calculated curve, besides the deviation was increased as dimensionless tracer amount (the ratio of tracer amount to hydrodynamic model tundish volume) increased from 0.202 × 10−3 to 1.008 × 10−3. The results of tracer concentration study were similar, namely the deviation was increased with concentration increased; on the other hand, the deformation of a “stair-shape” RTD curve occurred when tracer concentration was much lower (at dimensionless tracer amount of 0.168 × 10−3 with converting to saturated solution). Besides, the effect of tracer kind on the accuracy of hydrodynamic modeling was also studied; the measurements of KCl solution with lower density than that of NaCl solution exhibited more of accuracy. Finally, the optimized tracer in hydrodynamic model tundish of present work is saturated KCl solution with dimensionless tracer amount of 0.202 × 10−3.

  • 199.
    Chen, Chao
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi. State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing.
    Jonsson, Lage
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi. FOI, Swedish Defence Research Agency, Division of CBRN Defence and Security.
    Tilliander, Anders
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Cheng, Guoguang
    State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    A CFD Model Study of the Macroscopic Transport and Dynamic Removal of Inclusions at a Steel-Slag Interface for Different Tundish DesignsManuskript (preprint) (Övrigt vetenskapligt)
  • 200.
    Chen, Chao
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi. State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, China .
    Jonsson, Lage
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi. Swedish Def Res Agcy, FOI, Div CBRN Def & Secur, Sweden.
    Tilliander, Anders
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Cheng, Guoguang
    State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    A Mathematical Modeling Study of Tracer Mixing in a Continuous Casting Tundish2015Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 46, nr 1, s. 169-190Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A mathematical model based on a water model was developed to study the tracer mixing in a single strand tundish. The mixing behavior of black ink and KCl solution was simulated by a mixed composition fluid model, and the data were validated by water modeling results. In addition, a model that solves the scalar transport equation (STE) without any physical properties of the tracer was studied and the results were compared to predictions using the density-coupled model. Furthermore, the mixing behaviors of different amounts of KCl tracers were investigated. Before the model was established, KCl tracer properties such as the KCl molecule diffusion (KMD), the water molecule self-diffusion (WSD) in KCl solution, and the KCl solution viscosity (KV) were evaluated. The RTD curve of 250 mL KCl for the KMD case was closer to the water modeling results than that of the case implemented with only density. Moreover, the ensemble average deviation of the RTD curves of the cases implemented with KMD+ WSD, KMD+ KV, and KMD+ WSD+ KV to the KMD case is less than 0.7 pct. Thus, the water self-diffusion and KV were neglected, while the KCl density and KMD were implemented in the current study. The flow pattern of black ink was similar to the STE result i. e., the fluid flowed upwards toward the top surface and formed a large circulating flow at the outlet nozzle. The flow behavior of the 100, 150, and 250 mL KCl cases exhibited a strong tendency to sink to the tundish bottom, and subsequently flow through the holes in the dam. Thereafter, it propagated toward the outlet nozzle. Regarding the KCl tracer amount, the tracer concentration propagated to the outlet nozzle much faster for the larger amount case than for the smaller amount cases. However, the flow pattern for the 50 mL KCl case was somewhat different. The fluid propagated to the top surface which acted like black ink during the initial injection, and subsequently the fluid flowed throughout the holes at a much slower pace. The breakthrough time and peak concentration of RTD curves of model predictions and water modeling results showed a good agreement (all difference within 12.5 pct) for the 100, 150, and 250 mL KCl cases.

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