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  • 51.
    Andersson, Erik
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Johansson, Andreas
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    The effect of driving force in Gibbs energy on the fraction of martensite2013Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The background to this bachelor thesis is an on-going project within the VINN Excellence Center Hero-m. The task in this thesis is to perform a literature survey about the martensite transformation and investigate how the resulting fraction depends on cooling below the Ms-temperature. Instead of calculating the undercooling for each of the known fractions of martensite the driving force will be evaluated. Several efforts have been made through the years to describe the relationships between fraction transformed austenite and temperature. The approaches to the first models were empirical and derived from collections of data regarding the amount of retained austenite at different quenching temperatures. Lately, studies have been made to derive a thermodynamical relationship using how the Gibbs energy is affected by increments in volume transformed austenite. Two equations are derived by calculating the resulting driving force at different known quenching temperatures and the respective percentage transformed martensite found in previous works. The data for the steels used show a characteristic slope when linearised. A trend for the steels which have a high characteristic slope is that they also have a high Ms temperature, and the steels which have a low characteristic slope tend to have a low Ms. Previous relationships which describe the martensitic transformation have considered the importance of the Ms temperature only in it being a starting temperature for the transformation. To further incorporate the Ms temperature in the equations presented, further research of the martensitic transformation is required. The approach in this thesis of using thermodynamically calculated data is a base for further investigation of the range of the martensite transformation.

  • 52. Andersson, G.
    et al.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    "Steel eco-cycle" - A Swedish cross-pollination environmental research program2013Ingår i: Materials Science and Technology Conference and Exhibition 2013, MS and T 2013, Warrendale , 2013, s. 1784-1791Konferensbidrag (Refereegranskat)
    Abstract [en]

    In 2004, Swedish steel industry launched the first truly holistic research program in one of the world's most energy intensive industries with the aim to drastically increase the energy and resource efficiency by governing and reinforce (closing) the loop in the steel life cycle. The inter-disciplinary approach of the program has led to a significant cross-pollination in environmental steel technology and related areas apart from the impact in the educational field. The program, alongside the development of resource-efficient production of steel, has led to offshoots in aluminium remelting industry, recovery of rare earths from magnetic scrap and recovery of lead from CRT glasses. The research efforts led to the successful recovery of vanadium and magnetically important manganese nanoferrites from (waste) steel slags. The results, in fact, even provide insights into declarations of human attitudes, future raw material prognoses, process optimizations and pilot plant trials along with instrument and model developments.

  • 53.
    Andersson, Henrik C.M.
    et al.
    Swedish Institute for Metals Research.
    Sandström, Rolf
    Swedish Institute for Metals Research.
    Segle, P.
    SAQ Kontroll.
    Andersson, Peter
    SAQ Kontroll.
    Creep crackgrowth in ex service weld metal of 0.5CrMoV1999Ingår i: Cape 99: Wilderness, Cape province, South Africa, 12-16 April (1999), 1999Konferensbidrag (Refereegranskat)
    Abstract [en]

    Accurate assessment of the integrity of high temperature components will be of ever increasing importance. The reason for this is that many power plants have reached and exceeded their design life and the number of detected defects increases. This is accentuated by the improvement of the methods for non-destructive testing which means that more and smaller defects will be detected. The possibility to assess the influence of defects on the integrity of high temperature components, will be of vital importance to maintain safe and cost effective power plants.

    The aim of the present work is to increase the understanding of the influence of service exposure on the remaining life of components in a high temperature plant. The investigation aims to creep test exserviceweld material, 14MoV 6 3, from a Swedish power plant. Thematerial has been in service for a period of about 80 000 hours at atemperature of 530-540 °C and with a nominal hoop stress of 52MPa.Both uniaxial and compact tension creep tests have been performedat a temperature of 550 °C. The stress range used was between 130MPa and 170 MPa for the uniaxial creep tests. For the creep crack growth tests the reference stress was ranging between 122 MPa and146 MPa.

    A remaining life assessment according to the R5 procedure is included, where material data from the present experimental study is used. The analysis suggests that a defect or a crack with a depth of 2 mm and a length of 5 mm can be left unattended for a season of service under the condition that the service parameters are not changed. A comparison with the assessment of cracks, found in the same plant as the material for the experimental studies came from, and their known extension during service, is included. A parametric study where load level and type of initial defect/crack are varied is also included.

  • 54.
    Andersson, Joel
    et al.
    GKN Aerosp Engine Syst, SE-46181 Trollhattan, Sweden.;Univ West, Dept Engn Sci, SE-46186 Trollhattan, Sweden.;Chalmers, Dept Mat & Mfg Technol, SE-41296 Gothenburg, Sweden..
    Raza, Shahzad
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Eliasson, Anders
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Surreddi, Kumar Babu
    Chalmers, Dept Mat & Mfg Technol, SE-41296 Gothenburg, Sweden..
    SOLIDIFICATION OF ALLOY 718, ATI 718PLUS (R) AND WASPALOY2014Ingår i: 8TH INTERNATIONAL SYMPOSIUM ON SUPERALLOY 718 AND DERIVATIVES / [ed] Ott, E Banik, A Andersson, J Dempster, I Gabb, T Groh, J Heck, K Helmink, R Liu, X WusatowskaSarnek, A, JOHN WILEY & SONS INC , 2014, s. 181-192Konferensbidrag (Refereegranskat)
    Abstract [en]

    Alloy 718, ATI 718Plus (R) and Waspaloy have been investigated in terms of what their respective solidification process reveals. Differential thermal analysis was used to approach the task together with secondary electron and back scattered electron detectors equipped with an energy dispersive X-ray spectroscopy detector. These experimental methods were used to construct pseudo binary phase diagrams that could aid in explaining solidification as well as liquation mechanisms in processes such as welding and casting. Furthermore, it was seen that Waspaloy has the smallest solidification range, followed by Alloy 718, and finally ATI 718Plus (R) possessing the largest solidification interval in comparison.

  • 55.
    Andersson, Margareta
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Appelberg, Jesper
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Tilliander, Anders
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Nakajima, Keiji
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Shibata, Hiroyuki
    Tohoku University, Institute of Multidisciplinary Research for Advanced Materials.
    Kitamura, Shinya
    Tohoku University, Institute of Multidisciplinary Research for Advanced Materials.
    Jonsson, Lage
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Some Aspects on Grain Refining Additions with Focus on Clogging during Casting2006Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 46, nr 6, s. 814-823Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Some ideas of how to study optimum conditions for implementation of grain refining in liquid steel processing with focus on how to avoid clogging are discussed. It is assumed that the inclusions most beneficial for grain refining are known from studies by physical metallurgists. The challenge for a process metallurgist is how to provide a homogeneous distribution of grain refiners at the onset of solidification. Four different ways of providing information to succeed with this are discussed. Thermodynamic modeling can be used to predict what additions to make to create potential grain refiners, if relevant thermodynamic data is available. Mathematical fluid-flow modeling can be used to study where to add potential grain refiners. It is discussed that the tundish is the most appropriate reactor to add grain refiners, since enough time is given to a complete mixing of the grain refiner into the steel before the steel enters the mold. By using the scanning laser microscopy technique it is possible to study which potential grain refiners has the lowest attraction forces between each other. This is important in order to minimise growth of inclusions when they collide during transport in the tundish, which can lead to the formation of larger inclusions that do not serve as useful grain refiners. Finally, it is suggested that laboratory experiments are carried out in order to study the tendency for nozzle clogging, before the use of grain refiners is tested in industrial scale.

  • 56.
    Andersson, Margareta A.T.
    et al.
    KTH, Tidigare Institutioner, Materialvetenskap.
    Hallberg, Malin
    Jonsson, Lage
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Slag-metal reactions during ladle treatment with focus on desulphurisation2002Ingår i: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 29, nr 3, s. 224-232Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Within several cooperative projects, KTH (Royal Institute of Technology), Ovako Steel AB, and MEFOS have investigated the desulphurisation of bearing steel during vacuum degassing. The work includes thermodynamic calculations of the slag-metal equilibrium, CFD modelling of slag-metal reactions, and plant trials. Results from the various studies are presented and discussed in this paper. Models for predicting slag properties (sulphide capacity, viscosity, and oxide activities) in liquid slags as functions of slag composition and temperature have been used for the calculation of data which have been employed in static and dynamic modelling of sulphur refining. The results from static modelling show that the method allows fast and easy evaluation of the theoretical desulphurisation conditions during degassing at Ovako Steel AB, as well as theoretical determination of the parameters that have the greatest influence on the equilibrium sulphur distribution. The conclusion from dynamic modelling is that the vacuum degassing operation can be described dynamically with the present knowledge of sulphide capacity, sulphur distribution, viscosity, and oxide activities of ladle slags if this knowledge is combined with fluid flow modelling to derive the overall kinetics. The presented model approaches have been found useful in understanding the sulphur refining process at Ovako Steel AB. The dynamic modelling concept is also believed to have potential for dynamic descriptions of other slag-metal reactions in steelmaking.

  • 57.
    Andersson, Margareta
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Hallberg, Malin
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jonsson, Lage
    KTH, Tidigare Institutioner, Tillämpad processmetallurgi.
    Jönsson, Pär
    KTH, Tidigare Institutioner, Tillämpad processmetallurgi.
    Slag/metal reactionsduring ladle treatment with focus on desulphurisation2000Ingår i: 6thInternational Conference on Molten Slags, Fluxes and Salts, 2000Konferensbidrag (Refereegranskat)
  • 58.
    Andersson, Nils
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Tilliander, Anders
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jonsson, Lage
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Fundamental decarburisation model of AOD process2013Ingår i: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 40, nr 5, s. 390-397Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A mathematical fluid flow model of gas injection in an argon–oxygen decarburisation (AOD) converter process has been coupled with a high temperature thermodynamic model. The current model is a further enhancement of an earlier developed three-dimensional, three-phase model, to also include some thermodynamics of the process. The model is based on fundamental transport equations and includes separate solutions for the steel, slag and the gas phases and their coupling by friction. The AOD model has been used to predict the first injection stage of decarburisation in an AOD converter. The predictions have been found to agree well with the corresponding results from an industrial process control model. One of the important observations from the simulations was that large concentration gradients of carbon exist in the AOD at an early stage and as the first injection step approaching its end the carbon gradients diminish. Also, the results show, in accordance with theory, that the local decarburisation rate is decreased at elevated pressures.

  • 59.
    Andersson, Nils
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Tilliander, Anders
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jonsson, Lage
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Investigating the effectof slag on decarburization in an AOD converter using a fundamental model2013Ingår i: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 84, nr 2, s. 169-177Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A high-temperature thermodynamics model has been coupled with a fundamental mathematical model describing the fluid flow, where boundary conditions were chosen based on data for an industrial AOD converter. Using this model, the effect of both slag phases (a liquid part and a solid part) on the decarburization was studied. More specifically, the separation of chromium oxide to liquid slag as well as the effect of the amount of rigid top slag (solid)on the decarburization was investigated. The liquid slag was considered with respect to the uptake of chromium oxide, while the rigid top slag was only considered with respect to the increase of the metallostatic pressure in the steel melt. The results suggest that separation of chromium oxide to liquid slag results in a decreased decarburization rate. The same conclusion can be drawn with respect to the amount of solid top slag.

  • 60.
    Andersson, Nils
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Tilliander, Anders
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jonsson, Lage
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Preliminary investigation of influence of temperature on decarburisation using fundamental AOD model2013Ingår i: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 40, nr 7, s. 551-558Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A high temperature thermodynamics model was earlier coupled with a fundamental mathematical model describing the fluid flow in an argon–oxygen decarburisation (AOD) converter and was initially validated for an idealised temperature description. More specifically, a linear average temperature relation was used such that the temperature would be isolated from other effects such as reactions and mixing. Thereafter, the effect of the starting temperature on the decarburisation was studied. The purpose is to provide some initial knowledge about how temperature affects the decarburisation in an AOD converter. The results suggest that the thermodynamic limit for carbon concentration after reaching the carbon removal efficiency (CRE) maxima is vertically translated downwards at higher temperatures. Furthermore, when plotting the mass ratio between CO and CO2, there is an indication of a point that may relate to a CRE maximum.

  • 61.
    Andersson, Nils Å. I.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Coupling of a fundamental mathematical fluid flow model with computational thermodynamics model to study the decarburisation2012Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
  • 62.
    Andersson, Nils Å. I.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Tilliander, Anders
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jonsson, Lage T. I.
    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.
    A fundamental decarburization model of the AOD processIngår i: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812Artikel i tidskrift (Övrigt vetenskapligt)
  • 63.
    Andersson, Nils Å. I.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Tilliander, Anders
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jonsson, Lage T. I.
    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.
    An in-Depth Model-Based Analysis of Decarburization in the AOD Process2012Ingår i: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 83, nr 11, s. 1039-1052Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A previously reported flow and reaction model for an argon-oxygen decarburization converter was extended to also include a thermodynamic description. An in-depth study of the model results has been conducted to answer how concentrations of elements and species in the converter at different locations change with time. This may contribute to the understanding of the mechanisms of the refining procedure in the argon-oxygen decarburization process. The refining procedure includes several step-wise changes of an injected gas composition to higher and higher inert gas ratio, called step changes. A step change leads to a decreased partial pressure of carbon monoxide and maintains the decarburization at a higher efficiency. The results shows early and late concentration profiles for the first injection step and suggests a way to determine when a step change should be made. Moreover, the step change could be determined by calculating the carbon concentration profiles and deciding when the carbon concentration gradients start to diminish.

  • 64.
    Andersson, Nils Å. I.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Tilliander, Anders
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jonsson, Lage T. I.
    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.
    Investigating the effect of slag on decarburization in an AOD coverter using a fundamental modelIngår i: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344XArtikel i tidskrift (Övrigt vetenskapligt)
  • 65.
    Andersson, Nils Å. I.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Tilliander, Anders
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jonsson, Lage T. I.
    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.
    Preliminary investigation of temperatur dependencies on decarburization in a fundamental AOD modelIngår i: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812Artikel i tidskrift (Övrigt vetenskapligt)
  • 66.
    Andersson, Oscar
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Industriell produktion. KTH, Centra, XPRES, Excellence in production research.
    Budak, Nesrin
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    Melander, Arne
    KTH, Skolan för industriell teknik och management (ITM), Industriell produktion. KTH, Centra, XPRES, Excellence in production research.
    Palmquist, Niclas
    Experimental measurements and numerical simulations of distortions of overlap laser-welded thin sheet steel beam structures2017Ingår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 61, nr 5, s. 927-934Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Distortions of mild steel structures caused by laser welding were analyzed. One thousand-millimeter U-beam structures were welded as overlap joints with different process parameters and thickness configurations. Final vertical and transverse distortions after cooling were measured along the U-beam. Significant factors, which affect distortions, were identified. Heat input per unit length, weld length, and sheet thickness showed a significant effect on welding distortions. Furthermore, the welding distortions were modeled using FE simulations. A simplified and computationally efficient simulation method was used. It describes the effect of shrinkage of the weld zone during cooling. The simulations show reasonable computation times and good agreement with experiments.

  • 67.
    Appelberg, Jesper
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Nakajima, Keiji
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Shibata, H.
    Tilliander, Anders
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    In situ studies of misch-metal particle behavior on a molten stainless steel surface2008Ingår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 495, nr 1-2, s. 330-334Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The use of misch-metal is widely spread among the stainless steel producers. Casting problems like clogging are common when using these additions. Information about Ce-La-Al-O particles formed due to the addition of misch-metal in the ladle is scarce in the open literature. The aim of this study is to increase the knowledge of the particle behavior and the particle characteristics in two stainless steels resulting from the addition of misch-metal. The in situ particle behavior has been studied using a Confocal Laser Scanning Microscope.

  • 68. Arai, Y.
    et al.
    Emi, Toshihiko
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallernas gjutning.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallernas gjutning.
    Shibata, H.
    In-situ observed dynamics of peritectic solidification and delta/gamma transformation of Fe-3 to 5 At. Pct Ni alloys2005Ingår i: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 36A, nr 11, s. 3065-3074Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The characteristics of liquid -> delta ferrite and delta ferrite -> gamma austenite transformation in Fe-3.50 at. pct Ni alloy, and of the peritectic solidification of Fe-4.83 and 5.01 at. pct Ni alloys, have been dynamically observed in situ with a confocal scanning laser microscope (CSLM) combined with an infrared image furnace (IIF). The unique sequence, morphologies, and rates of these transformations have been determined at a temperature gradient of 4 K/mm and growth rates of 2 to 3 mu m/s, in unidirectional solidification experiments. These observations have been discussed in terms of the constitutional undercooling description of solidification theory.

  • 69.
    Arvhult, Carl
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Gueneau, Christine
    Univ Paris Saclay, CEA, DEN, SCCME, F-91191 Gif Sur Yvette, France..
    Gosse, Stephane
    Univ Paris Saclay, CEA, DEN, SCCME, F-91191 Gif Sur Yvette, France..
    Selleby, Malin
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Thermodynamic assessment of the Ni-Te system2019Ingår i: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 54, nr 16, s. 11304-11319Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A thermodynamic assessment of the Ni-Te system has been performed using the Calphad method, based on experimental data available in the literature. The proposed description has been developed for use in the modeling of fission-product-induced internal corrosion of stainless steel cladding in Generation IV nuclear reactors. DFT calculations were performed to obtain 0 K properties of solid phases to assist the thermodynamic optimization. The ionic liquid two-sublattice model was used, and most solution phases were modeled using interstitial metal sub-lattices. With a strict number of parameters, the resulting description satisfactorily reproduces all thermodynamic properties and high-temperature phase transitions. The metastable miscibility gap in the Ni-rich liquid that is experimentally suggested is not present in the final description. The phase exhibits a metastable order-disorder transition between the CdI2 and NiAs types of interstitial nickel distribution. The CdI2 prototype is the stable space group at room temperature. Low-temperature ordering phase transitions have been disregarded in this description, since they are not of interest to the application of corrosion in nuclear reactors.

  • 70.
    Arzpeyma, Niloofar
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Modeling of Post Combustion in Ovako electric arc furnace (EAF)Manuskript (preprint) (Övrigt vetenskapligt)
  • 71.
    Arzpeyma, Niloofar
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Numerical Study of the Gas Flow and Heat Transfer during Electromagnetic Stirring and Post Combustion in EAFs2014Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The effect of electromagnetic stirring on scrap melting and post combustion in two different electric arc furnaces (EAFs) have been studied using numerical modelling. The effect of electromagnetic stirring on melting of a piece of scrap located at the eccentric bottom tapping (EBT) region of an EAF has been studied. The results were compared to a condition in which the only source term for momentum transfer was buoyancy. It was shown that the use of electromagnetic stirring can contribute to a better heat transfer rate at the melt–scrap interface. The Grashof and Nusselt number for both electromagnetic stirring and natural convection were estimated, and were compared with those estimated in previous studies. The post combustion (PC) inside a duct system of an EAF has been studied considering combustion of hydrogen and carbon monoxide. The aim was to study the effect of air leakage through the airgap and fan power on post combustion of the off–gas leaving the furnace. Furthermore, to see how much uncombusted can be captured after the air gap. It was shown a higher off-gas mass flow rate and a higher power of the outlet fan led to a higher combustion of CO and H2. Moreover, a backward modeling of the flow was done to estimate the off–gas composition at the furnace outlet. The post combustion inside the same EAF used in the previous part has been studied. The domain consists of the fluid region above the melt bath. The oxy fuel reactions and combustion of CO were taken into account. The oxy-fuel reactions in a both simplified and a more accurate form (JC) were studied. The results showed less combustion of CO in the latter form. Using the results of the off–gas composition at the outlet, an attempt was made to estimate the flow rate of CO arising from the bath. Different flow rates of CO from the melt and air flow rate through the roof were assumed. In both burner mode and burner + lancing mode, the calculated concentration of CO2 was higher than that calculated in the previous part. The reason could be that the dissociation of CO2 to CO and O2 at high temperatures, and the de-post combustion of CO2 due to the reaction with carbon in the melt and in the electrodes were not considered.

  • 72.
    Arzpeyma, Niloofar
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Ersson, Mikael
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Mathematical Modeling of Postcombustion in an Electric Arc Furnace (EAF)2019Ingår i: METALS, ISSN 2075-4701, Vol. 9, nr 5, artikel-id 547Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Numerical modeling was used to study the capability of postcombustion in an electric arc furnace (EAF) equipped with virtual lance burners. The CO flow rate at the molten bath surface was estimated using the off-gas data obtained close to the outlet of an EAF. Then, the effect of the secondary oxygen flow rate on postcombustion was studied. The results show a CO flow rate of 0.6 kgs(-1) and 0.8 kgs(-1) for operation modes of burner and burner + lancing. Increase of the secondary oxygen flow rates of 60% and 70% result in 17% and 7% increase in the postcombustion ratio (PCR) for the burner and burner lancing modes, respectively.

  • 73.
    Arzpeyma, Niloofar
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Ersson, Mikael
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Modeling of post combustion inside the off-gas duct system of the Ovako electric arc furnace2014Ingår i: CDF 2014: 10th International Conference on CFD in Oil & Gas, Metallurgical and Process Industries, SINTEF, Trondheim, Norway, 17-19 June 2014, Proceedings, 2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    In order to study the post combustion (PC) inside the duct system of an electric arc furnace (EAF), a three-dimensional computational fluid-dynamics (CFD) model was developed. The reactions between the off gas species (oxygen and hydrogen) and oxygen which leaked into the duct, through the air gap, was considered. The off-gas composition, the off –gas velocity and the outlet pressure were considered as parameters affecting the PC. The results showed that there was a considerable amount of the uncombusted CO to be captured. The highest CO concentration was found at the central part of the duct. The results also showed that a higher off-gas mass flow rate and a higher power of the outlet fan led to a higher combustion of CO and H2. An off-gas analysis probe was then installed after the air gap, where the tip of the probe was placed according to the predicted high CO concentration area found in the simulations. Thereafter, the measured off-gas composition was used to predict the off-gas composition at the outlet of the EAF.

  • 74.
    Arzpeyma, Niloofar
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Widlund, Ola
    Ersson, Mikael
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Mathematical Modeling of Scrap Melting in an EAF Using Electromagnetic Stirring2013Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 53, nr 1, s. 48-55Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Numerical modeling has been used to investigate the influence of electromagnetic stirring on melting of a single piece of scrap in an eccentric bottom tapping (EBT) electric arc furnace (EAF). The heat transfer and fluid flow in the melt for both conditions with and without electromagnetic stirring were studied. The buoyancy and electromagnetic forces were considered as the source terms for momentum transfer in the studied conditions. The enthalpy-porosity technique was applied to track the phase change of a scrap piece defined in the EBT region of the furnace. Different scrap sizes, preheating temperatures, stirring directions and force magnitudes were considered, and the heat transfer coefficient was estimated from the heat transfer rate at the melt-scrap interface. The results showed that electromagnetic stirring led to a reduced melting time and an increased heat transfer coefficient by a factor of four. The results for Nusselt number versus Grashof number for natural convection and Reynolds number for electromagnetic stirring were compared with those obtained through correlations from previous studies.

  • 75.
    ASUMADU, TABIRI KWAYIE
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    MACRO INCLUSION RESEARCH: DETECTION AND EVALUATION OF MACRO INCLUSIONS IN SPECIAL STEELS2012Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
  • 76.
    Aune, Ragnhild E.
    KTH, Tidigare Institutioner                               , Metallurgi.
    Thermodynamic studies of some high temperature systems1997Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
  • 77.
    Aune, Ragnhild Elizabeth
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Experimental designs toward an understanding of process phenomena in steelmaking2006Ingår i: Iron and Steel Technology, ISSN 1547-0423, Vol. 3, nr 12, s. 137-146Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Various experimental studies towards the understanding of different process phenomena in iron and steelmaking were presented. Thermal diffusivity measurement was carried out at various temperature to monitor the structural changes occurring in coke. X-ray diffraction measurements were carried out to determine the average crystallite size of graphite along the structural c-axis and in the structural ab plane. It was observed that the apparent thermal diffusivity during the cooling cycle is larger than the heating cycle. Many experiments were also conducted in a high-temperature x-ray diffraction unit, to study the rate of graphitization at any given temperature for a given coke sample. An experimental design for the investigation of the mechanism of reduction in the blast furnace shaft, and the role of coke by dynamic x-ray photography was also carried out. The heating and melting of a mold flux during continuous casting were also simulated in specially designed laboratory.

  • 78. Avazkonandeh-Gharavol, M. H.
    et al.
    Haddad-Sabzevar, M.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallernas gjutning.
    Effect of partition coefficient on microsegregation during solidification of aluminium alloys2014Ingår i: International Journal of Minerals, Metallurgy and Materials, ISSN 1674-4799, E-ISSN 1869-103X, Vol. 21, nr 10, s. 980-989Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the modeling of microsegregation, the partition coefficient is usually calculated using data from the equilibrium phase diagrams. The aim of this study was to experimentally and theoretically analyze the partition coefficient in binary aluminum-copper alloys. The samples were analyzed by differential thermal analysis (DTA), which were melted and quenched from different temperatures during solidification. The mass fraction and composition of phases were measured by image processing and scanning electron microscopy (SEM) equipped with an energy-dispersive X-ray spectroscopy (EDS) unit. These data were used to calculate as the experimental partition coefficients with four different methods. The experimental and equilibrium partition coefficients were used to model the concentration profile in the primary phase. The modeling results show that the profiles calculated by the experimental partition coefficients are more consistent with the experimental profiles, compared to those calculated using the equilibrium partition coefficients.

  • 79. Avazkonandeh-Gharavol, M. H.
    et al.
    Haddad-Sabzevar, M.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Experimental analysis of partition coefficient in Al-Mg alloys2016Ingår i: Iranian Journal of Materials Science and Engineering, ISSN 1735-0808, Vol. 13, nr 2, s. 62-72Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Because the partition coefficient is one of the most important parameters affecting microsegregation, the aim of this research is to experimentally analyse the partition coefficient in Al-Mg alloys. In order to experimentally measure the partition coefficient, a series of quenching experiments during solidification were carried out. For this purpose binary Al-Mg alloys containing 6.7 and 10.2 wt-% Mg were melted and solidified in a DTA furnace capable of quenching samples during solidification. Cooling rates of 0.5 and 5 KJmin were used and samples were quenched from predetermined temperatures during solidification. The fractions and compositions of the phases were measured by quantitative metallography and SEM/EDX analyses, respectively. These results were used to measure the experimental partition coefficients. The resultant partition coefficients were used to model the concentration profile in the primary phase and the results were compared with equilibrium calculations and experimental profiles. The results of calculations based on the experimental partition coefficients show better consistency with experimental concentration profiles than the equilibrium calculations.

  • 80. Avazkonandeh-Gharavol, M. H.
    et al.
    Haddad-Sabzevar, M.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallernas gjutning.
    On the microsegregation of Al-Mg alloys by thermal analysis and numerical modeling2014Ingår i: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 610, s. 462-471Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Knowledge about solid fraction versus temperature during solidification is crucial for the control of solidification processes. In the present paper solidification sequence and path of Al-Mg binary alloys containing 6.7 and 10.2 wt.% Mg was investigated by a series of DTA and quenching experiments and numerical modeling in 0.5 and 5 K min(-1) cooling rates. Experimental results show that at both cooling rates, Al-6.7 wt.% Mg solidifies with a single phase structure, but Al-10.2 wt.% Mg solidifies with a two phase structure. According to the results of numerical modeling, good agreement between calculated solidification curves and experimental solid fractions, but poor correlation with concentration profiles. The source of discrepancies is discussed according to different theories of microsegregation.

  • 81.
    Ayedh, H. M.
    et al.
    Norway.
    Nipoti, R.
    Italy.
    Hallén, Anders
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Elektronik, Integrerade komponenter och kretsar.
    Svensson, B. G.
    Norway.
    Kinetics modeling of the carbon vacancy thermal equilibration in 4H-SiC2018Ingår i: International Conference on Silicon Carbide and Related Materials, ICSCRM 2017, Trans Tech Publications, 2018, s. 233-236Konferensbidrag (Refereegranskat)
    Abstract [en]

    The carbon vacancy (VC) is a major limiting-defect of minority carrier lifetime in n-type 4H-SiC epitaxial layers and it is readily formed during high temperature processing. In this study, a kinetics model is put forward to address the thermodynamic equilibration of VC, elucidating the possible atomistic mechanisms that control the VC equilibration under C-rich conditions. Frenkel pair generation, injection of carbon interstitials (Ci’s) from the C-rich surface, followed by recombination with VC’s, and diffusion of VC’s towards the surface appear to be the major mechanisms involved. The modelling results show a close agreement with experimental deep-level transient spectroscopy (DLTS) depth profiles of VC after annealing at different temperatures.

  • 82.
    Aytekin, Kasim
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Characterization of machinability in lead-free brass alloys2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Ny lagstiftning har lagt fokus på den tociska naturen av bly som legeringselement I mässingsprodukter. Vattenförsörjningssystem är av största oro där misstänkt blyläckage från mässingsprodukter hotar människors hälsa, världen över.

    Denna studie har utförts i syfte att karaktärisera bearbetbarheten av blyfria mässingslegeringar för att förse industrin med nödvändig information och underlätta att ersätta dagens blyade alternativ. Karaktäriseringen har fokuserat på två specifika bearbetningsprocesser, nämligen svarvning och borrning där intresset har legat hos skärkraftsgenerering och spånbildning. Svarvtesterna riktade sig mot att jämföra tre olika legeringar, CW511L, AquaNordicÒ och CW625N. De två förstnämnda är blyfria och CW625N är en medelblyhaltig mässingslegering. Borrtesterna riktade sig mot att karaktärisera vilken effekt borrgeometrier har på skärkraftsgenerering och spånbildning. Huvudfokus lades på inverkan av spånvinkel och borrdiameter. Borrtesterna utfördes endast på AquaNordicÒ.

    Resultaten har visat att, signifikant högre skärkrafter genereras vid svarvning av blyfria legeringar jämfört med blyfria. Det fanns emellertid ingen signifikant skillnad mellan de båda blyfria legeringarna avseende skärkrafter, medan spånbildning förbättrades för AquaNordicÒ . Borrtesterna har å andra sidan visat att bearbetningen hos den blyfria AquaNordicÒ -legeringen kan förbättras genom att öka på spånvinkeln och minska borrdiameter.

    Baserat på resultaten från det här avhandlingsarbetet har man dragit slutsatsen att bearbetningen av blyfria mässingslegeringar är tillräckligt bra för att kunna antas av industrin. Förbättring är dock nödvändig för att ersätta de blyeade alternativen helt.

  • 83.
    Babu, Prasath
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap. Indian Institute of Science, Bangalore, India.
    Vamsi, K. V.
    Karthikeyan, S.
    On the formation and stability of precipitate phases in a near lamellar γ-TiAl based alloy during creep2018Ingår i: Intermetallics (Barking), ISSN 0966-9795, E-ISSN 1879-0216, Vol. 98, s. 115-125Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The formation, evolution and stability of metastable phases observed in the γ-TiAl based alloy Ti-47Al-2Cr-2Nb was studied under creep deformation with stress applied at two different hard orientations in a highly textured as-cast + HIPed material. Previously we have reported that the metastable phase Ti(Al,Cr)2 with C14 Laves phase structure forms at the γ-α2 interface which acts as sink for the alloying elements ejected from the dissolving α2 phase and also expected to effectively control the interface stresses through short range diffusion and modifications in the chemical composition [1]. Ab initio density functional theory based calculations were carried out to evaluate the effect of choice of lattice position and site occupancy of aluminium atoms in the Ti(Al,Cr)2 structure on the lattice parameter variation and thermodynamic stability. C14 with the composition 25 at. % Al was found to have lattice parameter values close to the inter-planar spacing of <110>γ and <10-10>α2 which would have a lower misfit with C14 across the interface. From the cohesive energy calculations, Laves phase C14 with a constrained lattice parameter due to the adjoining phases, exhibits higher stability than the B2 and L10 structures across a range of compositions studied. Electron diffraction simulations of C14 with a composition of 25% Al compared with the experimental data suggest that the structure C14 has taken up either a random site occupancy compared to a specific choice of ordering to minimize the interfacial stress. Though the experimental evidences do not strongly support a long-range ordering theory in C14, short-range ordering could be a tangible choice for alleviating interface misfits. The ability of C14 to assume different lattice parameters at and far from the α2-γ interface also suggest that the C14 acts as buffer layer between α2 and γ phases in the presence of local stresses, although this is not the thermodynamically expected phase at the temperature of creep experiment.

  • 84.
    Bai, Haitong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    A Study of the Swirling Flow Pattern when Using TurboSwirl in the Casting Process2016Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Tidigare studier visar att ett roterande flöde kan ge en mer likformig hastighetsfördelning och en lugnare fyllning i både göt- och stränggjutning av stål. De befintliga metoderna för att generera ett roterande flöde har vissa begränsningar. En ny metod för att generera det roterande flödet, en så kallad TurboSwirl, föreslogs nyligen. I detta arbete undersöktes ett konvergent munstycke med olika vinklar för att se hur detta påverkade det roterande flödet som genererades i anordningen. Resultaten visar att skjuvspänningen i systemet kan reduceras genom att ändra munstyckets vinkel mellan 40º till 60º. En lägre maximal axiell hastighet kan också uppnås med en mindre konvergent vinkel på munstycket. Det är även möjligt att påverka den maximala axiella hastigheten och skjuvspänningen i systemet genom att förflytta den vertikala kanalen i anordningen. Vattenmodellexperiment har utförts för att validera simuleringsresultaten. Det kraftigt roterande flödet kunde endast beskrivas väl av Reynolds Stress Model (RSM). Validering utfördes också genom att mäta den radiella hastigheten i den vertikala kanalen med en Ultrasonic Velocity Profiler (UVP). TurboSwirl-anordningen vändes och kopplades till gjutröret för att generera det roterande flödet. Detta studerades både med numeriska modeller och med vattenmodellering. Ett periodiskt asymmetriskt roterande flöde observerades både i numeriska modellerna och i vattenmodellerna. För att modellera detta periodiska flöde så användes detached eddy simulation (DES) modellen. Resultaten då denna modell användes stämmer väl med de experimentella mätningarna. Denna nya design med TurboSwirl kan uppnå liknande styrka på det roterande flödet som när elektromagnetisk omrörning användes. Det resulterande roterande flödet leder till en lägre axiell hastighet i gjutröret samt en lugnare yta och ett lugnare flöde i kokillen.

  • 85.
    Bai, Haitong
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Ersson, Mikael
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jonsson, Par
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Effect of TurboSwirl Structure on an Uphill Teeming Ingot Casting Process2015Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 46, nr 6, s. 2652-2665Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To produce high-quality ingot cast steel with a better surface quality, it would be beneficial for the uphill teeming process if a much more stable flow pattern could be achieved in the runners. Several techniques have been utilized in the industry to try to obtain a stable flow of liquid steel, such as a swirling flow. Some research has indicated that a swirl blade inserted in the horizontal and vertical runners, or some other additional devices and physics could generate a swirling flow in order to give a lower hump height, avoid mold flux entrapment, and improve the quality of the ingot products, and a new swirling flow generation component, TurboSwirl, was introduced to improve the flow pattern. It has recently been demonstrated that the TurboSwirl method can effectively reduce the risk of mold flux entrapment, lower the maximum wall shear stress, and decrease velocity fluctuations. The TurboSwirl is built at the elbow of the runners as a connection between the horizontal and vertical runners. It is located near the mold and it generates a tangential flow that can be used with a divergent nozzle in order to decrease the axial velocity of the vertical flow into the mold. This stabilizes flow before the fluid enters the mold. However, high wall shear stresses develop at the walls due to the fierce rotation in the TurboSwirl. In order to achieve a calmer flow and to protect the refractory wall, some structural improvements have been made. It was found that by changing the flaring angle of the divergent nozzle, it was possible to lower the axial velocity and wall shear stress. Moreover, when the vertical runner and the divergent nozzle were not placed at the center of the TurboSwirl, quite different flow patterns could be obtained to meet to different requirements. In addition, the swirl numbers of all the cases mentioned above were calculated to ensure that the swirling flow was strong enough to generate a swirling flow of the liquid steel in the TurboSwirl.

  • 86.
    Bai, Haitong
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Ersson, Mikael
    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.
    An Experimental and Numerical Study of Swirling Flow Generated by TurboSwirl in an Uphill Teeming Ingot Casting Process2016Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 56, nr 8, s. 1404-1412Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A swirling flow has been demonstrated to be beneficial for making the flow pattern even and to reduce turbulence during filling in ingot casting. A new swirling flow generation device, TurboSwirl, was applied to improve the flow pattern of the liquid steel as it flows into the mold so that a more stable flow could be obtained. A water model was built including the TurboSwirl with different flaring angles of the divergent nozzle, according to a former numerical study indicating that a much more beneficial flow pattern could be obtained by reducing the flaring angle. To validate the mathematical model, the air-core vortex formed in the water model experiment was used, and the length of the vortex was measured and compared to the numerical predictions. Different turbulence models including the standard k-epsilon, realizable k-epsilon and Reynolds stress model were tested. It was found that only the Reynolds stress model could most accurately simulate the high swirling flow including a vortex. In addition, the radial velocity of the water around the vortex was measured by an ultrasonic velocity profiler (UVP). The experimental results revealed a high turbulence of the swirling flow and strong fluctuations of the vortex. The radial velocity of the water around the upper part of the vortex could be predicted well compared to the experimental results by the UVP measurements.

  • 87.
    Bai, Haitong
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Ersson, Mikael
    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.
    Experimental Validation and Numerical Analysis of the Swirling Flow in a Submerged Entry Nozzle and Mold by using a Reverse TurboSwirl in a Billet Continuous Casting Process2016Ingår i: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344XArtikel i tidskrift (Refereegranskat)
    Abstract [en]

    As an alternative to some traditional methods to generate a swirling flow in the continuous casting process, the use of a new swirling flow generator, TurboSwirl, was studied. Specifically, a reversed TurboSwirl device was designed as part of a submerged entry nozzle (SEN) for a round billet continuous casting process. Mathematical modelling was used to investigate this new design and a water model experiment was carried out to validate the mathematical model. The predicted velocities by the turbulence models: realizable k-ε model, Reynold stress model (RSM) and detached eddy simulation (DES) were compared to the measured results from an ultrasound velocity profile (UVP) method. The DES model could give the best prediction inside the SEN and had a deviation less than 3.1% compared to the measured results. Moreover, based on the validated mathematical model and the new design of the SEN, the effect of the swirling flow generated by the reverse TurboSwirl on the flow field of the SEN and mold was compared to the design of the electromagnetic swirl flow generator (EMSFG). A very strong swirling flow in the SEN and a stable flow pattern in the mold could be obtained by the reverse TurboSwirl compared to the EMSFG. 

  • 88.
    Bai, Haitong
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Ersson, Mikael
    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.
    Numerical Study of the Application for the Divergent Reverse TurboSwirl Nozzle in the Billet Continuous Casting ProcessManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    The swirling flow is demanded from the submerged entry nozzle (SEN) to the mold for the continuous casting process. A new design of the SEN is applied by using the reverse TurboSwirl. The TurboSwirl has been proved that it can provide a more stable flow pattern of the liquid steel in the mold. It also can supply a strong enough swirling flow compared to other swirling flow generation methods. Furthermore, a divergent nozzle is added to replace the bottom part of the straight SEN. This new divergent reverse TurboSwirl nozzle (DRTSN) could gain a more beneficial flow pattern in the mold compared to the straight nozzle. The numerical results reveals that a stronger swirling flow can be gained at the SEN outlet with a calmer flow field and active meniscus flow. It is also found that the swirl intensity in the SEN is independent of the casting speed. Lower casting speed is more desired due to a lower maximum wall shear stress. The DRTSN is connected to the tundish by an elbow and a horizontal runner. Longer horizontal runner can supply a more uniform velocity profile and symmetrical flow pattern in the mold. 

  • 89. Bai, Q.
    et al.
    Guo, Z.
    Cui, X.
    Yang, X.
    Yanhua, L.
    Jin, L.
    Sun, Y.
    Experimental investigation on the solidification rate of water in open-cell metal foam with copper fins2018Ingår i: Energy Procedia, Elsevier Ltd , 2018, s. 210-214Konferensbidrag (Refereegranskat)
    Abstract [en]

    This study focused on the effect of inserting fins into metal foam on the solidification rate. To this aim, a well-designed experimental system with solid-liquid interface visualization was built. Metal foam samples with different fin intervals were prepared for experiments. Solidification process of water saturating in finned metal foam under bottom cooling was experimentally investigated. Results showed that inserting fins into metal foam can make a promotional improvement on solidification rate of water. The solid-liquid interface became curved after inserting fins, compared with metal foam sample without fins. Besides, changing the interval has little effect on the solidification rate. 

  • 90. Bai, Q.
    et al.
    Guo, Z.
    Li, H.
    Yang, Xiaohu
    KTH, Skolan för kemivetenskap (CHE).
    Jin, L.
    Yan, Jerry
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik, Energiprocesser.
    Experimental investigation on the solidification behavior of phase change materials in open-cell metal foams2017Ingår i: Energy Procedia, Elsevier Ltd , 2017, Vol. 142, s. 3703-3708Konferensbidrag (Refereegranskat)
    Abstract [en]

    This study presented an experimental investigation on solidification behavior of fluid saturated in highly porous open-cell copper foams. Particular attention has been made on the effect of pore parameters (pore density and porosity) on the solidification behavior. A purposely-designed apparatus was built for experimental observations. Results showed that the copper foam had a great effect on solidification and the full solidification time can be saved up to 50%, especially preventing the decrease in solidification rate during the later stage of phase change. The smaller the porosity is, the faster the solidification rate will be. Pore density was found to have little influence upon the solidification rate. In addition, the local natural convection does exist but it has a slight effect on solidification, leading to the slant of the solid-liquid interface.

  • 91.
    Ballesteros, Antonio
    et al.
    JRC Petten, Holland.
    Hein, Hieronymus
    AREVA Gmbh Germany.
    May, Johannes
    AREVA Gmbh Germany.
    Planman, Tapio
    VTT Finland.
    Todeshini, Patrick
    EdF France.
    Brumowski, Milan
    UJV Czech Republic.
    Roudén, Jenny
    Gillemot, Ferenc
    MTA Hungary.
    Chaouadi, Rachid
    SCK-CEN, Belgium.
    Efsing, Pål
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    Altstadt, Eberhard
    Forschung Center Rossendorff, Germany.
    Reactor Pressure vessel surveillance2014Ingår i: Nuclear Engineering International, ISSN 0029-5507, Vol. 59, nr 12, s. 19-20Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This publication summarizes techniques suitable for surveillance program for the objective of  long term operation (LTO) on European NPPs and provides recommendations on reactor pressure vessel (RPV) irradiation surveillance based on the work preformed in the work package 7 "Surveillance guidelines" of the LONGLIFE international project. The LONGLIFE project "treatment of long term irradiation embrittlement effects in RPV safety assessment" was 50% funded by the Euratom 7th framework programme of the European commision. The project coordinated by the Helmholtz-centrum Dresden Rossendorf successfully finalized in 2014.

  • 92. Ban-Ya, S.
    et al.
    Hino, M.
    Hayashi, M.
    Sano, N.
    Fredriksson, Patrik
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Comments on "Evaluation of thermodynamic activity of metallic oxide in a ternary slag from the sulphide capacity of the slag"2005Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 45, nr 11, s. 1754-1757Artikel i tidskrift (Refereegranskat)
  • 93.
    Barsoum, Zuheir
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Numerical Analysis and Measurement of Residual Stresses in Multi Pass Welding - Influence on Fatigue Root Crack Propagation2006Ingår i: TRENDS IN WELDING RESEARCH, PROCEEDINGS / [ed] David SA; DebRoy T; Lippold JC; Smartt HB; Vitek JM, MATERIALS PARK: ASM INTERNATIONAL , 2006, s. 589-594Konferensbidrag (Refereegranskat)
    Abstract [en]

    The purpose of this study is to investigate the residual stresses near the weld root and the weld toe for multi-pass welded tube-to-plates, and the influence of residual stresses on multiaxial fatigue of tubular joints. Two different tubular joint configurations were studied; a three-pass single-U weld groove for maximum weld penetration and a two-pass fillet (no groove) welded tube-to-plates for minimum weld penetration. An axi-symmetric finite element model was developed to calculate the temperature distribution, HAZ, penetration depth and the residual stress distribution for the sequentially coupled thermo-mechanical analysis. The calculated geometry and the temperature distribution of the fusion zone showed good agreement with the micro samples of the welds. The calculated residual stresses was compared with experimental results and showed qualitatively good agreement. The "design root crack" is under compressive stresses in both configuration, -230 MPa for the single-U weld groove and -120 MPa for the fillet weld, respectively. Also the weld toe, transition between weld and tube, is under compressive stresses. Multi-axial fatigue tests were performed in order to study weld root crack propagation. The tube structures were loaded with a static internal pressure in order to separate the design root crack and initiate the crack growth. The fatigue tests show that, depending on the size of the static imposed internal pressure, different crack paths are received.

  • 94.
    Barsoum, Zuheir
    et al.
    KTH. Nordic Welding Engineering AB, Nansta 208, Forsa, Sweden.
    Stenberg, Thomas
    KTH. Nordic Welding Engineering AB, Nansta 208, Forsa, Sweden.
    Lindgren, E.
    Fatigue properties of cut and welded high strength steels-Quality aspects in design and production2018Ingår i: Procedia Engineering, Elsevier, 2018, Vol. 213, s. 470-476Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this study, several aspects regarding effect of quality on the fatigue strength in welded cut HSS have been investigated and are discussed. A novel numerical algorithm has been developed which assesses the welded surface and calculates and quantifies weld quality parameters and the presence of defects which are critical in fatigue applications. The algorithm is designed for implementation in serial production. It will provide robust and reliable feedback on the quality being produced, which is essential if high strength steels are utilized and high quality welds are necessary for the structural integrity of the welded component. Two welding procedures which can increase the weld quality in as welded conditions have been assessed. It was found that by using these methods, the fatigue strength can be increased with 20% compared to normal weld quality. Furthermore, two fatigue assessment methods ability to account for increased weld quality in low cycle and high cycle fatigue applications has been studied. One of these methods showed sufficient accuracy in predicting the fatigue strength with small scatter and also account for increased weld quality. The influence of surface quality on cut edges was studied and the fatigue strength was estimated using international standards and a fatigue strength model for cut edges. It was found that the fatigue strength in testing was 15-70% higher compared to the estimation, thus proving a weak link between the international standard and fatigue strength.

  • 95.
    Basirat, Mitra
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallernas gjutning.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallernas gjutning.
    An Insight into the Effect of Deformation on Carbide Dissolution in the Band Structure of Bearing Steel2013Ingår i: Diffusion In Solids And Liquids VIII, Trans Tech Publications Inc., 2013, s. 171-176Konferensbidrag (Refereegranskat)
    Abstract [en]

    Dendritic segregation in deformed samples remains in the form of band structure, which is a high-strained region. The present work investigates the effect of the uphill diffusion process, occurring during deformation, on the dissolution of carbide particles in the band structure. A series of hot compression tests are performed on the cast structure of bearing steel by using a hydraulic testing machine, MTS 810. Cylindrical specimens are deformed in a temperature range of 800 degrees C to 900 degrees C and at strain rates of 5s(-1) and 0.5s(-1). In order to eliminate the recovery process, samples are immediately quenched after the compression. The microsegregation of Cr, Mo, Mn and Si are investigated in the band structure, which shows a tendency of uphill diffusion during deformation process. The results show that the volume fraction of carbides varies with the increased straining. The results also show that deformation causes the fragmentation, dispersion of pearlite in the dendrites and the dissolution of spheroidized carbides in the band structure.

  • 96.
    Basirat, Mitra
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallernas gjutning.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallernas gjutning.
    Disorder Structure formation during plastic defroamtion of pure copper2012Ingår i: International journal of material science, ISSN 0973-4589, Vol. 7, nr 3, s. 169-182Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effect of the deformation process at 300˚C on the cast structure of pure copper is investigated. The temperature measurements during compression test are performed by a new experimental method developed earlier [1]. The deformed structure is studied with the aid of optical and transmission electron microscopy. Micrographs show the formation of deformed bands with high internal energy, due to many lattice defects. The strain energy calculations are based on an energy balance and the data obtain from micrograph studies performed by optical and transmission electron microscopy. It is found that there is a significant difference in the strain energy values obtained in the present work compared to the values available in the literature.  The strain energy values obtained in the band structure of the present work are 17.4% to 24% of the heat of fusion of Cu. Such high energy is sufficient to change the normal FCC structure to a disordered atomic structure in the highly deformed regions, during plastic deformation.

  • 97.
    Basirat, Mitra
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallernas gjutning.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallernas gjutning.
    Effect of deformation on microsegregation in cast structure of bearing steel2012Ingår i: TMS 2012 141st Annual Meeting & Exhibition - Supplemental Proceedings, Vol 2: Materials Properties, Characterization, And Modeling, 2012, Vol. 2, s. 309-316Konferensbidrag (Refereegranskat)
    Abstract [en]

    Microsegregation changes in the cast structure of a five-ton ingot of ball bearing steel are investigated by a series of hot compression tests. Cylindrical specimens are deformed at a temperature range of 800 degrees C to 900 degrees C and strain rates of 0.5 s(-1). Samples are quenched after the compression in order to eliminate the homogenization time. Subsequently they are analysed with the aid of Electron Microprobe Analysis (EMPA) in order to investigate the effect of hot compression on microsegregation of Mo, Cr, Mn and Si. It is found that highly segregated regions are regions for formation of deformation bands. It seems that the degree of microsegregation increases by increasing the deformation. An attempt is made to estimate the diffusion coefficients of alloying elements during the deformation process. The increase of microsegregation during deformation is explained by tendency for uphill diffusion.

  • 98.
    Basirat, Mitra
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallernas gjutning.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallernas gjutning.
    Plastic Deformation and Recrystallization in Incoloy 825Manuskript (preprint) (Övrigt vetenskapligt)
  • 99.
    Basu, Somnath
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Studies on dephosphorisation during steelmaking2007Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    This work is aimed at understanding the thermodynamic principles influencing the phosphorus partition between slag and steel during steelmaking, particularly during refining of high-phosphorus hot metal using the basic oxygen steelmaking (BOS) process. Mapping of the slag path has been carried out using a mass balance model based on input conditions and off-gas analysis, which has been validated by intermediate measurements of slag and metal composition in an industrial basic oxygen furnace (BOF). The slag composition is found to vary over a wide range of basicity (%CaO/%SiO2) and iron oxide content. The partition of phosphorus increases with progress of refining but reduces during the intermediate period, corresponding to a decrease in iron oxide concentration and formation of “dry slag”. The phosphorus partition ratio increases again towards the end of the process. The equilibrium partition ratios for such conditions have been theoretically estimated using slag “model(s)”, based on the estimated slag compositions. It is seen that the partition ratio of phosphorus remains within 45% – 60% of the equilibrium value, showing a gradual decrease with progress of the refining process.

    Equilibrium phosphorus partition ratios for slags containing low concentrations of MnO and Al2O3 have been experimentally determined, over the ranges of basicity and iron oxide concentration approximately corresponding to that observed in the typical BOS process. It is seen that the equilibrium phosphorus partition ratio is practically independent of basicity greater than 2.5 – 2.6, over the entire range of temperature and FeOx concentration studied. Variation of the activity of P2O5 with basicity and FeOx concentration has been investigated to explain the trends observed in the variation of phosphorus partition ratio. It is seen that the activity coefficient of P2O5 is lowest, and hence most conducive for removal of phosphorus from steel, over certain finite ranges of basicity and iron oxide concentration. It follows that the efficiency of dephosphorisation is likely to be maximum if the basic oxygen steelmaking process is operated within these ranges. Simultaneous with this work, mathematical correlations have been developed for estimation of P2O5 activity coefficient and phosphorus partition ratio as functions of slag composition. The correlations are compared with those proposed by earlier workers and are found to result in better predictions over certain composition ranges.

  • 100.
    Basu, Somnath
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Lahiri, Ashok Kumar
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    A model for activity coefficient of P2O5 in BOF slag and phosphorus distribution between liquid steel and slag2007Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 47, nr 8, s. 1236-1238Artikel i tidskrift (Refereegranskat)
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