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  • 1.
    Adolfi, Sofia
    et al.
    KTH, Superseded Departments, Casting of Metals.
    Lagerstedt, Anders
    KTH, Superseded Departments, Casting of Metals.
    Sarnet, Jan
    Scana Steel Björneborg AB.
    Fredriksson, Hasse
    KTH, Superseded Departments, Casting of Metals.
    Macrosegregation In Ingot Cast Tool Steel2004Report (Other academic)
  • 2.
    Antonsson, Tomas
    KTH, Superseded Departments, Casting of Metals.
    On the interaction between liquid/ solid during sintering and solidification2003Doctoral thesis, comprehensive summary (Other scientific)
  • 3.
    Antonsson, Tomas
    et al.
    KTH, Superseded Departments, Casting of Metals.
    Ekbom, Lars B.
    KTH, Superseded Departments, Casting of Metals.
    Eliasson, Anders
    KTH, Superseded Departments, Casting of Metals.
    Fredriksson, Hasse
    KTH, Superseded Departments, Casting of Metals.
    Liquid Ni-Fe penetration and recrystallisation in tungsten2003In: International journal of refractory metals & hard materials, ISSN 0958-0611, E-ISSN 2213-3917, Vol. 21, no 3-4, p. 159-170Article in journal (Refereed)
    Abstract [en]

    Melt penetration in grain boundaries of solid tungsten has been investigated. Solid tungsten rods have been exposed to a nickel-iron melt saturated with tungsten and the penetration depth and the shape of the liquid channels have been examined. The solid tungsten samples have been treated in different ways like cold working, annealing and recrystallisation, before melt exposure. Important parameters for the penetration process are stresses, surface tensions, solution and kinetic effects. A new theoretical model for the penetration mechanism in cold worked samples is proposed. Rapid recovery of the grains in the penetrated areas of the cold worked samples was observed. This is discussed, as well.

  • 4.
    Elfsberg, Jessica
    KTH, Superseded Departments, Casting of Metals.
    Oscillation Mark Formation in Continuous Casting Processes2003Licentiate thesis, comprehensive summary (Other scientific)
  • 5.
    Elfsberg, Jessica
    et al.
    KTH, Superseded Departments, Casting of Metals.
    Fredriksson, Hasse
    KTH, Superseded Departments, Casting of Metals.
    Oscillation Mark Formation on Continuously Cast Copper2003Report (Other academic)
  • 6.
    Elfsberg, Jessica
    et al.
    KTH, Superseded Departments, Casting of Metals.
    Fredriksson, Hasse
    KTH, Superseded Departments, Casting of Metals.
    Theoretical Study of Oscillation Mark Formation in Continuous Casting Processes2003Report (Other academic)
  • 7.
    Elfsberg, Jessica
    et al.
    KTH, Superseded Departments, Casting of Metals.
    Widell, Björn
    KTH, Superseded Departments, Casting of Metals.
    Fredriksson, Hasse
    KTH, Superseded Departments, Casting of Metals.
    Experimental Study of the Formation of Oscillation Marks in Continuous Casting of Steel Billets2002In: 4th European Continuous Casting Conference, Oct 14-15 2002, Birmingham,England, 2002Conference paper (Other academic)
  • 8.
    Eliasson, Anders
    et al.
    KTH, Superseded Departments, Casting of Metals.
    Hailom Yosef, Futsum
    KTH, Superseded Departments, Casting of Metals.
    Fredriksson, Hasse
    KTH, Superseded Departments, Casting of Metals.
    Dynamic temperature measurements and solidification structures in centrfugally casted IN718.2003Conference paper (Other academic)
  • 9.
    Fredriksson, Hasse
    et al.
    KTH, Superseded Departments, Casting of Metals.
    Elfsberg, Jessica
    KTH, Superseded Departments, Casting of Metals.
    Thoughts about the Initial Solidification Process during Continuous Casting of Steel2002In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 31, p. 292-297Article in journal (Other academic)
    Abstract [en]

    The initial solidification during continuous casting is very important for the surface quality of the strand. Oscillation marks are formed by the movement of the mould. One mainly distinguishes between two different types of marks, namely folding marks and overflow marks. The formation of these can be described by the heat flow and the surface tension balance. A theoretical analysis outlining the most important parameters controlling the formation of these marks is presented. A metallographic analysis of the formation was also performed. The theory and observations have been used to analyse the effect of casting speed and oscillation frequency on the formation of different types of marks. It is shown that a meniscus is formed at the top of the growing shell. The maximum height of the meniscus determines the ideal distance between the marks. The mould frequency is related to this height. A frequency that is far from ideal causes overflow marks and folding marks with macrosegregation and cracks. The distance between the marks is, in such cases, not constant. The depth of the marks is calculated from the heat flow and the surface tension balance.

  • 10.
    Hailom Yosef, Futsum
    et al.
    KTH, Superseded Departments, Casting of Metals.
    Fredriksson, Hasse
    KTH, Superseded Departments, Casting of Metals.
    On the solidification behaviour of ferritic stainless steels2003Report (Other academic)
  • 11.
    Kron, Jenny
    KTH, Superseded Departments, Casting of Metals.
    Air gap formation and hot tearing in solidification processing of Al- and Cu-base alloys2004Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Shrinkage in a solidifying metal has been studiedexperimentally as well as theoretically. The main focus hasbeen to examine the mechanisms causing an air gap to formbetween a casting and a mould, and hot crack formation to occurin a solidifying metal.

    ¨The formation of an air gap has been experimentallystudied during solidification of Al- and Cu-based alloys in acylindrical mould. The displacements of the casting and themould causing an air gap have been measured duringsolidification and cooling of the casting. The temperaturedistribution was measured simultaneously. Mathematicalmodelling has been performed to increase the understanding ofthe solidification process and the strains formed in thesolidifying metal contributing to the formation of an air gapbetween casting and mould. Most of the work was dedicated todevelop a new model to describe the strain duringsolidification, but traditional theory was used for themodelling work as well.

    The model suggested in this work includes non-equilibriumeffects on the solidification process and the shrinkage. Theformation and condensation of lattice defects formed in thesolid phase during solidification and its effect on thesolidification process as well as on the material shrinkageresulting in air gap formation was considered. The results fromthe modelling work show good agreement with the experimentalresults. The conclusion is that it is important to includethese non-equilibrium effects in modelling of shrinkage duringsolidification.

    The same conclusion was drawn from results of experimentalwork with high temperature tensile testing of in situsolidified samples and the development of a new theory for hotcrack formation. It was found that a super saturation oflattice defects formed during the solidification processenhances the nucleation and growth of hot cracks duringcooling.

  • 12.
    Magnusson, Lena
    et al.
    KTH, Superseded Departments, Casting of Metals.
    Adolfi, Sofia
    Fredriksson, Hasse
    A Thermodynamic Analysis of the Inoculation Process in Cast IronIn: International Journal of Cast Metals Research, ISSN 1364-0461, E-ISSN 1743-1336Article in journal (Refereed)
  • 13.
    Sarnet, Jan
    et al.
    KTH, Superseded Departments, Casting of Metals.
    Widell, Björn
    KTH, Superseded Departments, Casting of Metals.
    Influence of Various Heating and Forging Routes on the Microstructure of 3%Ni-Steels2003Conference paper (Refereed)
  • 14.
    Tinoco, José
    KTH, Superseded Departments, Casting of Metals.
    On the Spray Forming of Metals, the Formation of Porosity and the Heat Evolution during Solidification2003Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    This thesis deals with the heat evolution duringsolidification and its relation to the formation of porosity.It intends to improve the current understanding of theformation of porosity in cast materials with special interestin nodular cast iron and the spray forming process. Twodifferent systems, a Fe-based alloy, Cast iron, and a Ni-basedalloy, Inconel 625, are examined. The effect on the heatevolution of the morphology and the processing parameters inspray forming are treated.

    An evaluation of the microstructural features, segregationbehavior and physical properties such as latent heat of fusionis performed byusing thermal analysis under cooling ratesranging from 0.1 to 104 K/s. In order to achieve this amodified differential thermal analysis (DTA) equipment, amirror furnace and levitation casting are used. Results arepresented in terms of the fraction of solidified, the coolingrate and the microstructure observed. The measured latent heatof fusion is not constant throughout the solidificationprocess. Variations in morphology and cooling rate affect therelease of the latent heat.

    A thermodynamic model is used to describe the experimentalobservations and to explain the formation of pores in nodularcast iron by taking into consideration the formation of latticedefects during the liquid/solid transformation. In this casethe formation of porosity is regarded as a consequence ofchanges in the volume fraction ratio graphite/ during thesolidification process.

    A numerical model of the spray forming process is developedby means of CFD modelling and compared with experimentalmeasurements performed in an industrial facility. Stagnationpressure measurements provided information about the gas flowvelocity and an analysis of the overspray powder providedinformation about the particle thermal history. Evaluation ofthe deposit was also performed. It is observed that the processconditions in spray forming promote non-equilibriumsolidification even though solidification at the deposit occursat a lower rate. In this case the porosity formed near theinterface substrate/deposit depends largely on the substratetemperature. The presence of certain reactive elements, such astitanium, affects the porosity levels in the rest of thedeposit.

    Keywords:Thermal Analysis, Nodular Cast Iron, Inconel625, CFD, Flow Assesment, Multiphase Flow, Spray Deposition,Microporosity, Superalloys

  • 15.
    Tinoco, José
    et al.
    KTH, Superseded Departments, Casting of Metals.
    Widell, Björn
    KTH, Superseded Departments, Casting of Metals.
    Fredriksson, Hasse
    KTH, Superseded Departments, Casting of Metals.
    Fuchs, Laszlo
    Modeling the in-flight events during metal spray forming2004In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 365, no 1-2, p. 302-310Article in journal (Refereed)
    Abstract [en]

    In this work, the in-flight events occurring during deposition over a rotating substrate were modeled. The calculations were performed by solving the momentum and enthalpy equations for the gas. A Lagrangian approach was used to obtain the trajectories and thermal history of the droplets. A modified heat capacity model was used to simulate the release of latent heat due to the solidification of the droplets. Turbulent particle dispersion was not considered. The results showed that the droplet temperature strongly depends on the droplet diameter and on its location in the spray since the relative velocity between the gas and the droplets varies largely depending on the location. An estimation of the state of the spray is presented in terms of mass and thermal averages. The results showed that the average fraction of solid obtained in the spray depends on the initial conditions, such as gas temperature and particle size distribution parameters.

  • 16. Vinet, Bernard
    et al.
    Magnusson, Lena
    KTH, Superseded Departments, Casting of Metals.
    Fredriksson, Hasse
    KTH, Superseded Departments, Casting of Metals.
    Desré, Pierrre Jean
    Correlations between surface and interface energies with respect to crystal nucleation2002In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 255, no 2, p. 363-374Article in journal (Refereed)
    Abstract [en]

    The energetic chemical and structural properties of interfaces between solid and liquid metals are of great interest in numerous applications. However, solid-liquid interfacial energies of metals are often determined by nucleation experiments, requiring particular attention to the measurements so obtained. The purpose of this paper is to conduct an analysis of the level of liquid undercooling of 3d-, 4d-, and 5d-transition metals, as well as of other common undercooled elements, through a critical survey of thermophysical data and experimental results. As already pointed out for the liquid-vapor surface energy sigma(LV), the solid-liquid interface energy sigma(LS) determined from the maximum amount of liquid undercooling is well connected to the position of the element in the periodic table, leading to the individualization of each behavior, including the size of the critical nucleus. The beta ratio of sigma(LS)/sigma(LV) is demonstrated to be an interesting dimensionless number by which to classify the elements into distinctive groups. No significant unexplained anomaly is identified, except for Co, supporting the belief that Turnbull's classical theory furnishes a robust support to describe the crystal nucleation in pure elements.

  • 17.
    Yeddu, Hemantha Kumar
    KTH, Superseded Departments, Casting of Metals.
    Effect of mould oscillation parameters on oscillation mark formation in continuous cast steels2004Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 18.
    Åberg, Jonas
    et al.
    KTH, Superseded Departments, Materials Processing.
    Widell, Björn
    KTH, Superseded Departments, Casting of Metals.
    Uniaxial material damping measurements using a fiber optic lattice: a discussion of its performance envelope2004In: Experimental mechanics, ISSN 0014-4851, E-ISSN 1741-2765, Vol. 44, no 1, p. 33-36Article in journal (Refereed)
    Abstract [en]

    Damping is the internal transfer of kinetic energy to other forms of energy. Today, most methods use either bending or torsional vibration to measure damping. This means that the strain field in the specimen is nonhomogeneous. If the damping of the tested material is linear, strain-independent, the values acquired with these traditional methods will be equal to the intrinsic material damping of the material. If, however, the damping is strain-dependent, nonlinear, the measured value will be an average of the damping of the specimen, and not equal to its intrinsic material damping. To address this problem, a method is required to experimentally determine the damping in uniaxial tension in order to produce the same strain level in all parts of the test specimen and hence obtain a measurement of the intrinsic material damping. Using such a method, it is possible to view the material damping as the phase angle between the stress and the strain in a harmonic oscillation. In this paper, a method is suggested for measuring this phase shift in uniaxial tension to determine the material damping properties. It uses a tensile test machine, an optical fiber Bragg grating technique and a lock-in amplifier. Measurements with the phase shift technique have been suggested previously, but its performance envelope has been overestimated. In this paper, the performance envelope is discussed and restricted. It is shown that the envelope depends on the specimen length, loss factor and test frequency. An optical strain measurement method is also believed to help avoid many electrical measurement problems seen with the originally proposed method.

  • 19.
    Åberg, Jonas
    et al.
    KTH, Superseded Departments, Casting of Metals.
    Widell, Björn
    KTH, Superseded Departments, Casting of Metals.
    Bergström, Thomas
    KTH, Superseded Departments, Casting of Metals.
    Fredriksson, Hasse
    KTH, Superseded Departments, Casting of Metals.
    Measurement of intrinsic material damping using differential calorimetry on specimens under uniaxial tension2004In: Thermochimica Acta, ISSN 0040-6031, E-ISSN 1872-762X, Vol. 411, no 2, p. 125-131Article in journal (Refereed)
    Abstract [en]

    A method has been developed to measure the intrinsic damping capacity of metals. A specimen is subjected to a cyclic uniaxial stress, to give a prescribed energy input. The amount of energy that is stored in the specimen is measured using differential calorimetry, i.e. the difference in temperature between the specimen under stress and a non-stressed reference sample is measured. The experiments were performed in an insulated vacuum container to reduce convective losses. The heating rate, together with the energy input, is used as a measure of the intrinsic material damping in the specimen. The method has been developed by testing an aluminium based and a stainless steel alloy. It is possible to distinguish the difference in damping between these two alloys.

1 - 19 of 19
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