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  • 51. Sato, T.
    et al.
    Bjurström, Martin
    KTH, Superseded Departments, Metallurgy.
    Jönsson, Pär
    KTH, Superseded Departments, Materials Science and Engineering.
    Iguchi, M.
    Swinging motion of bath surface induced by side gas injection2004In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 44, no 11, p. 1787-1792Article in journal (Refereed)
    Abstract [en]

    Cold model experiments were carried out to understand a swinging motion of the bath in the AOD process. Water and air were used as the working fluids. A water bath contained in a cylindrical vessel was agitated by side gas injection using an L-shaped lance. Under a certain blowing condition the surface of the bath swung in the vertical direction like a liquid column oscillating in a U-shaped tube. The preferable occurrence condition of this swinging motion was correlated with the size of a plume eye on the bath surface and the vessel diameter. Empirical equations were proposed for the period and amplitude of the swinging motion.

  • 52. Schwind, M.
    et al.
    Helander, T.
    Ågren, John
    KTH, Superseded Departments, Metallurgy.
    On zigzag shaped diffusion paths in multi-phase diffusion couples2001In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 44, no 3, p. 415-421Article in journal (Refereed)
  • 53. Schwind, M.
    et al.
    Kallqvist, J.
    Nilsson, J. O.
    Ågren, John
    KTH, Superseded Departments, Metallurgy.
    Andren, H. O.
    sigma-phase precipitation in stabilized austenitic stainless steels2000In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 48, no 10, p. 2473-2481Article in journal (Refereed)
    Abstract [en]

    Experimental observations of sigma-phase precipitation in two stabilized austenitic stainless steers, AISI 321 and AISI 347, aged up to 80,000 h at temperatures between 500 and 800 degrees C, are compared with the results obtained from a simple model of the process. The model is based on the assumption that diffusion of alloying elements from inside austenite grains to sigma-phase particles at grain boundaries limits the rate of formation, and this is supported by the presence of zones depleted in chromium at grain boundaries revealed by TEM/EDS. The full multicomponent thermodynamic behaviour of the system is taken into account using the DICTRA software and the influence of grain shape is discussed. The predictions of the model are in fair agreement with experimentally estimated Volume fractions of sigma-phase.

  • 54. Schwind, M.
    et al.
    Ågren, John
    KTH, Superseded Departments, Metallurgy.
    A random walk approach to Ostwald ripening2001In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 49, no 18, p. 3821-3828Article in journal (Refereed)
    Abstract [en]

    We investigate a numerical model of Ostwald ripening in which matter is discretised. The model is based on transport by random walk and certain rules at the phase interfaces which mimic the continuous solution of the diffusion and moving boundary problem. In the limit of low volume fractions the results from our simulations agree quantitatively with the results predicted by the Lifshitz-Slyosov-Wagner theory. In contrast to the LSW model, the volume fraction of particles enters our model as part of the diffusion problem and it may therefore be confidently used to investigate what happens when the volume fraction of particles increases.

  • 55.
    Seetharaman, Seshadri
    et al.
    KTH, Superseded Departments, Metallurgy.
    Sichen, Du
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Jönsson, Pär
    KTH, Superseded Departments, Applied Process Metallurgy.
    Jonsson, Lage
    KTH, Superseded Departments, Applied Process Metallurgy.
    Modelling of Metallurgical Reactions Towards Process Simulations2000Conference paper (Refereed)
  • 56. Stolyarova, V.L
    et al.
    Aune, Ragnhild, E
    KTH, Superseded Departments, Metallurgy.
    Seetharaman, Seshadri
    KTH.
    High-temperature Mass Spectrometric Study of the Vaporization of Dysprosium Trifluoride1996In: Rapid Communications in Mass Spectrometry, ISSN 0951-4198, E-ISSN 1097-0231, Vol. 10, no 5, p. 501-508Article in journal (Refereed)
    Abstract [en]

    The high-temperature Knudsen effusion method was used to study the vaporization processes and thermodynamic properties of dysprosium trifluoride in the temperature range 1280-1440 K. Data on the partial vapour pressure of DyF3 as a function of temperature and the enthalpy of sublimation of DyF3 were obtained. Using the value of the enthalpy of formation of solid DyF3, available in the literature, the enthalpy of formation of the gaseous molecule of dysprosium trifluoride and its atomization energy were calculated. At 1382 K, the partial vapour pressure of Dy2F6 over dysprosium trifluoride was obtained and the Gibbs energy of the gaseous reaction (Dy2F6)=(2DyF3) was evaluated.

  • 57. Tao, L
    et al.
    Blasiak, Wlodzimierz
    Fakhrai, Reza
    KTH, Superseded Departments, Metallurgy.
    Use of a Computer Model for Evaluation of Combustion and NOx Control Alternatives in a Kraft Recovery Boiler1998In: TAPPI Proceedings, 1998Conference paper (Other academic)
  • 58. Thornton, K.
    et al.
    Ågren, John
    KTH, Superseded Departments, Metallurgy.
    Voorhees, P. W.
    Modelling the evolution of phase boundaries in solids at the meso- and nano-scales2003In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 51, no 19, p. 5675-5710Article, review/survey (Refereed)
    Abstract [en]

    Phase boundaries play an important role in setting the properties of multicomponent materials at both the meso- and nano-scales. In this review, we provide an overview of the modelling methods utilized in state-of-the-art research and engineering applications. We review the current physical understanding of how phase boundaries evolve, focusing on multicomponent systems. The recent advances in numerical modelling, fueled by powerful computers, have provided accurate and robust results that allow problems that are beyond the reach of analytic methods to be addressed. While the approaches used in engineering-oriented applications employ simplified microstructures, it is found that such models are quite useful in many problems. The ability to simulate realistic microstructures will further increase the power of materials modelling. We also highlight the differences between the sharp interface and diffuse interface approaches for modelling microstructural evolution. In addition, we identify future research topics in this area.

  • 59.
    Tilliander, Anders
    KTH, Superseded Departments, Metallurgy.
    Modeling of fluid flow and heat transfer characteristics in AOD nozzles2000Licentiate thesis, comprehensive summary (Other scientific)
  • 60.
    Tilliander, Anders
    et al.
    KTH, Superseded Departments, Metallurgy.
    Jonsson, Lage
    KTH, Superseded Departments, Metallurgy.
    Jönsson, Pär
    KTH, Superseded Departments, Metallurgy.
    A nozzle model considering the effect of density variations using the equation of stateIn: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916Article in journal (Other academic)
  • 61.
    Tilliander, Anders
    et al.
    KTH, Superseded Departments, Metallurgy.
    Jönsson, Pär
    KTH, Superseded Departments, Metallurgy.
    Jonsson, T L I
    KTH, Superseded Departments, Metallurgy.
    Lille, Simon
    KTH, Superseded Departments, Metallurgy.
    An experimental and numerical study of fluid flow in AOD Nozzles2002In: Iron & steelmaker, ISSN 0275-8687, Vol. 29, no 2, p. 51-57Article in journal (Refereed)
    Abstract [en]

    A mathematical model of a nozzle used in AOD converters was developed in a previous study. In the work covered in this article, an attempt was made to verify velocity predictions from the nozzle model through a comparison of measurements. Experiments were performed at AGA AB's laboratories using a laser doppler anemometer (LDA) to measure axial velocities at the outlet of a nozzle having the same dimensions as nozzles used in industrial AOD converters. The model predictions agreed well with measured data. An attempt was also made to compare turbulent kinetic energy predictions from the k-ε turbulence model with turbulence predictions calculated using an analytical expression that uses measured velocity fluctuation values. The positive results from this comparison indicate that the model can produce fairly reliable predictions of turbulence at the nozzle outlet. The results from this study are promising regarding use of the nozzle model to calculate boundary condition input values pertaining to the nozzle inlet that will be required for an AOD converter model currently being developed.

  • 62. Tolochko, O.
    et al.
    Ågren, John
    KTH, Superseded Departments, Metallurgy.
    Thermodynamic properties of supercooled Fe-B liquids - A theoretical and experimental study2000In: Journal of phase equilibria (Print), ISSN 1054-9714, E-ISSN 1544-1032, Vol. 21, no 1, p. 19-24Article in journal (Refereed)
    Abstract [en]

    The two-level model, recommended at the Ringberg 95 workshop, is applied to extrapolate the thermodynamic properties of liquid Fe-B alloys to large undercooling and to analyze the crystallization of glassy Fe85B15 alloys obtained by melt spinning. The new method yields practically the same phase diagram as the SGTE database but a superior result when evaluating the heat capacity, entropy, and crystallization heat at large undercooling. These properties are compared in the low-temperature range (700 to 800 K) with the experimental data obtained for an Fe85B15 metallic glass by scanning calorimetry. A good agreement between experiments and calculations is obtained when the observed magnetic transition at 530 K is taken into account.

  • 63.
    Tripathi, Nagendra N.
    et al.
    KTH, Superseded Departments, Metallurgy.
    Nzotta, M.
    Sandberg, A.
    Sichen, Du
    KTH, Superseded Departments, Materials Science and Engineering.
    Effect of ladle age on formation of nonmetallic inclusions in ladle treatment2004In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 31, no 3, p. 235-240Article in journal (Refereed)
    Abstract [en]

    An experimental study was carried out at Uddeholm Tooling, Hagfors, Sweden to examine the impact of ladle glaze on the formation of non-metallic inclusions during the ladle treatment process. Steel samples were taken at various stages of the process and from ladles of different ages. Inclusion numbers were counted under an optical microscope. It was found that the total number of inclusions increased with the ladle age before deoxidation and at the end of the ladle treatment. The increase was substantial after the ladle had been used more than 18 times. Inclusions having the smallest sizes were found to make a large contribution to this increase. This observation was further confirmed by the difference between total oxygen content and dissolved oxygen content in the steel samples, which also showed an increase with ladle age. Analysis by SEM-EDX revealed two types of inclusions before casting, namely, inclusions consisting only of an oxide solution having a composition very close to 3CaO.Al2O3, and inclusions consisting of the same oxide solution as well as MgO phase. This finding was in accordance with the reported result that both 3CaO.Al2O3 and MgO were present in the slag infiltrated layer of the ladle glaze. It was concluded that ladle glaze is the foremost source of non-metallic inclusions in tool steel during ladle treatment.

  • 64. Uhrenius, B.
    et al.
    Bergstrom, L.
    Ågren, John
    KTH, Superseded Departments, Metallurgy.
    Westin, G.
    Nygren, M.
    Salwen, A.
    Inorganic interfacial engineering: processing of hard materials2004In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 47, no 4, p. 317-331Article in journal (Refereed)
    Abstract [en]

    Inorganic interfacial engineering may be regarded as the core of powder metallurgical processing of hard materials. The present paper reviews recent results from an interdisciplinary research effort, BRIIE ( the Brinell Centre for Inorganic Interfacial Engineering), a joint effort between five industrial companies, three universities, two research institutes and VINNOVA ( the Swedish Agency for Innovation Systems). The research involves experimental work on the aqueous processing of powders and the use of surface actants is reviewed as well as the colloidal processing of ceramics. Pressing and sintering of agglomerated powders have been studied both theoretically and experimentally. Models for the simulation of pressing and sintering of hard metal powders are developed. Results on ceramic materials obtained by spark plasma sintering and their resistance to thermal shock are reported.

  • 65.
    Xu, Zhihui
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Ågren, John
    KTH, Superseded Departments, Metallurgy.
    An analysis of piling-up or sinking-in behaviour of elastic-plastic materials under a sharp indentation2004In: Philosophical Magazine, ISSN 1478-6435, E-ISSN 1478-6443, Vol. 84, no 23, p. 2367-2380Article in journal (Refereed)
    Abstract [en]

    Finite-element simulation has been carried out to investigate the piling-up or sinking-in behaviour of elastic - plastic strain-hardening materials under a sharp indentation. An empirical model is proposed to relate the contact area to the material parameter E/sigma(y) and the experimental parameter h(e)/h(max). Materials with E/sigma(y)

  • 66. Yokoya, S.
    et al.
    Jönsson, Pär G.
    KTH, Superseded Departments, Metallurgy.
    Sasaki, K.
    Tada, K.
    Takagi, Shigeo
    KTH, Superseded Departments, Metallurgy.
    Iguchi, M.
    The effect of swirl flow in an immersion nozzle on the heat and fluid flow in a billet continuous casting mold2004In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 33, no 1, p. 22-28Article in journal (Refereed)
    Abstract [en]

    A numerical analysis and a water model study of the mold region of a billet continuous caster was performed with a novel injection concept using swirling flow in the pouring tube, to control the heat and mass transfer in the continuous casting mold. The following results were found: A weak impinging flow can be observed near the corner of the mold wall, which results in the promotion of uniform heat and mass transfer all around across the plane, particularly at the casting corner. An upward flow directed from the vicinity of the nozzle outlet to the meniscus can be observed near the corner of the upper part of the mold, which leads to the active heat and mass transfer into the meniscus. A uniform velocity and heat distribution can be obtained within a short distance of 200 mm downward from the outlet of the nozzle. Quite different mold flow patterns are observed between the divergent and straight immersion nozzles. Heat and mass transport in the mold using the divergent nozzle is much more reasonable than that using the straight nozzle.

  • 67.
    Ågren, John
    KTH, Superseded Departments, Metallurgy.
    On the classification of phase transformations2002In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 46, no 12, p. 893-898Article in journal (Refereed)
    Abstract [en]

    The various classification schemes, based on thermodynamics, microstructure or mechanism, are discussed and criticized from a practical as well as a more fundamental point of view. For example, it is generally not meaningful to consider first and second-order transformations as equivalent with heterogeneous and homogeneous transformations, respectively.

  • 68.
    Ågren, John
    et al.
    KTH, Superseded Departments, Metallurgy.
    Hayes, F. H.
    Höglund, Lars
    KTH, Superseded Departments, Materials Science and Engineering.
    Kattner, U. R.
    Legendre, B.
    Schmid-Fetzer, R.
    Applications of computational thermodynamics2002In: Zeitschrift für Metallkunde, ISSN 0044-3093, Vol. 93, no 2, p. 128-142Article in journal (Refereed)
    Abstract [en]

    The major tools used in applying computational thermodynamics to various problems in materials science are briefly presented and several practical examples are given as illustrations. Solutions to industrial problems, pertaining to the processing of and microstructure development in several different materials, are shown with answers given in graphical form. Solutions to kinetic problems linked with diffusion are also treated. The last section is devoted to the problem of interfacing between thermodynamic computations and applications oriented software.

12 51 - 68 of 68
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