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  • 1.
    Akbarnejad, Shahin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jonsson, Lage
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Kennedy, M. W.
    Aune, R. E.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Analysis on Experimental Investigation and Mathematical Modelling of Incompressible Flow through Ceramic Foam FiltersManuscript (preprint) (Other academic)
  • 2.
    Akbarnejad, Shahin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Jonsson, Lage Tord Ingemar
    Kennedy, Mark William
    Aune, Ragnhild Elizabeth
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Analysis on Experimental Investigation and Mathematical Modeling of Incompressible Flow Through Ceramic Foam Filters2016In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 47, no 4, p. 2229-2243Article in journal (Refereed)
    Abstract [en]

    This paper presents experimental results of pressure drop measurements on 30, 50, and 80 pores per inch (PPI) commercial alumina ceramic foam filters (CFF) and compares the obtained pressure drop profiles to numerically modeled values. In addition, it is aimed at investigating the adequacy of the mathematical correlations used in the analytical and the computational fluid dynamics (CFD) simulations. It is shown that the widely used correlations for predicting pressure drop in porous media continuously under-predict the experimentally obtained pressure drop profiles. For analytical predictions, the negative deviations from the experimentally obtained pressure drop using the unmodified Ergun and Dietrich equations could be as high as 95 and 74 pct, respectively. For the CFD predictions, the deviation to experimental results is in the range of 84.3 to 88.5 pct depending on filter PPI. Better results can be achieved by applying the Forchheimer second-order drag term instead of the Brinkman-Forchheimer drag term. Thus, the final deviation of the CFD model estimates lie in the range of 0.3 to 5.5 pct compared to the measured values.

  • 3.
    Akbarnejad, Shahin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Saffari Pour, Mohsen
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jonsson, Lage
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Significance of Fluid Bypassing Effect on Darcy and Non-Darcy Permeability Parameters of Ceramic Foam FiltersManuscript (preprint) (Other academic)
  • 4.
    Akbarnejad, Shahin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Saffari Pour, Mohsen
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Jonsson, Lage Tord Ingemar
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Jönsson, Pӓr Göran
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Effect of Fluid Bypassing on the Experimentally Obtained Darcy and Non-Darcy Permeability Parameters of Ceramic Foam Filters2017In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 48, no 1, p. 197-207Article in journal (Refereed)
    Abstract [en]

    Ceramic foam filters (CFFs) are used to remove solid particles and inclusions from molten metal. In general, molten metal which is poured on the top of a CFF needs to reach a certain height to build the required pressure (metal head) to prime the filter. To estimate the required metal head, it is necessary to obtain permeability coefficients using permeametry experiments. It has been mentioned in the literature that to avoid fluid bypassing, during permeametry, samples need to be sealed. However, the effect of fluid bypassing on the experimentally obtained pressure gradients seems not to be explored. Therefore, in this research, the focus was on studying the effect of fluid bypassing on the experimentally obtained pressure gradients as well as the empirically obtained Darcy and non-Darcy permeability coefficients. Specifically, the aim of the research was to investigate the effect of fluid bypassing on the liquid permeability of 30, 50, and 80 pores per inch (PPI) commercial alumina CFFs. In addition, the experimental data were compared to the numerically modeled findings. Both studies showed that no sealing results in extremely poor estimates of the pressure gradients and Darcy and non-Darcy permeability coefficients for all studied filters. The average deviations between the pressure gradients of the sealed and unsealed 30, 50, and 80 PPI samples were calculated to be 57.2, 56.8, and 61.3 pct. The deviations between the Darcy coefficients of the sealed and unsealed 30, 50, and 80 PPI samples found to be 9, 20, and 31 pct. The deviations between the non-Darcy coefficients of the sealed and unsealed 30, 50, and 80 PPI samples were calculated to be 59, 58, and 63 pct.

  • 5.
    Alevanau, Aliaksandr
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Ersson, Mikael
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Kantarelis, Efthymios
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
    Kuznechik, Olgerd
    Belarussian State University.
    Vyhoniailo, Oleksandr
    Mechanically assisted low temperature pyrolysis of hydrocarbons2014In: Proceedings of the XVII International Conference Foundations & Advances in Nonlinear Science, September 29 - October 3, Minsk 2014, 2014Conference paper (Refereed)
    Abstract [en]

    We report experimental setups and conditions leading to pyrolysis (cracking) of such gaseous hydrocarbons as methane, mixed propane and butane, at the temper-atures of the heater below 200oC. The process was mechanically assisted by putting the substances being decomposed into a dynamic interaction with the tin and bismuth alloy. The alloy had periodically changing phase state thus creating fractal interfaces between its surface and the gases. Interaction of the gases with mechanically produced fractal surfaces of the alloy made possible gas decomposition even at lower temperatures of the heater (150oC). At this temperature the heater couldn't melt the alloy in the heated volume with the gas.

  • 6. Alexis, J.
    et al.
    Ramirez, M.
    Trapaga, G.
    Jönsson, Pär
    KTH, Superseded Departments, Materials Science and Engineering.
    Modeling of a DC electric arc furnace - Heat transfer from the arc2000In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 40, no 11, p. 1089-1097Article in journal (Refereed)
    Abstract [en]

    A mathematical model describing heat and fluid flow in an electric are has been developed and used to predict heat transfer from the are to the steel bath in a DC Electric Are Furnace. The are model takes he separate contributions to the heat transfer from each involved mechanism into account, i.e. radiation, convection, condensation and energy transported by electrons. The model predicts heat transfer for different currents and are lengths. Model predictions show that are efficiency is higher for lower power input. The model also predicts shear stresses and current density distribution at the steel surface. This information can be used as boundary condition input to simulate the effect of heating with electrodes in a DC EAF on the heat and fluid flow in the steel bath.

  • 7.
    Alexis, Jonas
    et al.
    Swerea-Mefos.
    Jonsson, Lage
    KTH, Superseded Departments, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, Superseded Departments, Applied Process Metallurgy.
    Heat and fluid-flow models for stirring conditionsin ladle furnaces and their practical implications in secondary refiningoperations1997In: Clean Steel 5, Vol 1,  2-4 June 1997, Balatonszeplak,Hungary, Balatonszeplak, 1997, p. 49-58Conference paper (Refereed)
  • 8.
    Alexis, Jonas
    et al.
    Swerea-Mefos.
    Jönsson, Pär
    KTH, Superseded Departments, Applied Process Metallurgy.
    Jonsson, Lage
    KTH, Superseded Departments, Applied Process Metallurgy.
    A model of an induction-stirred ladle accounting for slag and surface deformation1999In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 39, no 8, p. 772-778Article in journal (Refereed)
  • 9.
    Alexis, Jonas
    et al.
    Swerea-Mefos.
    Jönsson, Pär
    KTH, Superseded Departments, Metallurgy.
    Jonsson, Lage
    Heating and electromagnetic stirring in a ladle furnace – a simulationmodel2000In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 40, no 11, p. 1098-1104Article in journal (Refereed)
    Abstract [en]

    A three-dimensional simulation model coupling heating and induction stirring in an ASEA-SKF ladle furnace was developed. Data of the heat transfer from the area to the steel bath were predicted in a separate model and included as boundary conditions in a ladle model. The are model considers the contributions of heat transferred by of each of the following mechanisms: radiation, convection, condensation and energy transported by electrons. Predictions were made to simulate the change of temperature distribution in the ladle during simultaneous heating with electrodes and stirring by induction. A first attempt was made to compare the predictions with measured temperatures from a 100 t ASEA-SKF ladle. The agreement was found to be fairly good when heat-flux data for a 25 cm are length were used as input to the ladle model. This indicates that the model can be used for more in-depth studies of the effects of heating for ladles that are inductively stirred.

  • 10. Almcrantz, M.
    et al.
    Andersson, Margareta A.T.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Determination of inclusion characteristics in the Asea-SKF process using the modified spark-induced OES technique as a complement in studying the influence of top slag composition2005In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 76, no 9, p. 624-634Article in journal (Refereed)
    Abstract [en]

    The spark-induced modified optical emission spectroscopy (OES) technique developed by Ovako Steel makes it possible to rapidly determine inclusion characteristics in steel samples. In earlier investigations using the modified spark-induced OES technique for steel samples taken from billets, predicted oxygen contents agreed well with results from conventional melt extraction analyses. In this investigation, samples taken during ladle treatment in an ASEA-SKF ladle furnace were analysed using the modified OES technique. When comparing the results with inclusion characteristics determined by conventional analysis, similar trends were found. Plant trials were also carried out where three different top slag compositions were used. The purpose was to evaluate if the modified OES technique can be used to study the effect of changes in the refining operation on inclusion characteristics. Results indicated that the modified OES technique could be used to determine the effect of a changed slag composition on the inclusion characteristics in the steel. Since the modified OES method provides rapid feedback of inclusion characteristics, it has the potential of being used for faster optimisation of ladle refining operations.

  • 11.
    Andersson, Annika
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Andersson, Margareta A.T.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär G
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    A study of some elemental distributions between slag and hot metal during tapping of the blast furnace2004In: Steel research, ISSN 0177-4832, Vol. 75, no 5, p. 294-301Article in journal (Refereed)
    Abstract [en]

    This paper investigates the distribution of elements between slag and hot metal from a blast furnace through calculation of distribution coefficients from actual production data. First, samples of slag and hot metal tapped from a commercial blast furnace were taken continually at 10-minute intervals for a production period of 68 hours. Distribution coefficients of manganese, silicon, sulphur and vanadium were then calculated from the results of the sample analyses. A major conclusion drawn from examination of the results was that the behaviour of the studied elements was as could be expected when approaching the equilibrium reactions from thermodynamic theory. The distributions of the elements in the slag-metal system showed clear tendencies which did not appear to be influenced by the operational conditions of the furnace. For example, for manganese, vanadium and sulphur, it was found that a higher basicity led to a decreased distribution coefficient L-Mn and L-V, but an increased L-S, which is according to theory. Another observed relationship was that slag basicity increased with an increased carbon content in the hot metal, which indicated that SiO2 was reduced to [Si] when the oxygen potential decreased. Furthermore, it was found that sulphur and silica behaviour likened that of acidic slag components, while the manganese oxide and vanadium oxide behaviour was similar to that of basic slag components.

  • 12. Andersson, Annika J.
    et al.
    Andersson, Margareta A. T.
    KTH, Superseded Departments, Materials Science and Engineering.
    Jönsson, Pär G.
    KTH, Superseded Departments, Materials Science and Engineering.
    Variation in hot metal and stag composition during tapping of blast furnace2004In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 31, no 3, p. 216-226Article in journal (Refereed)
    Abstract [en]

    To determine the quality of the hot metal and the thermal conditions inside the blast furnace, the composition of the hot metal and slag must be known. Obtaining representative metal and slag samples during tapping is thus highly important to blast furnace operation. The study covered in the present report focused on hot metal and slag composition variation during tapping from a commercial blast furnace. From the results, optimal sampling time points for obtaining elemental concentrations that can be taken as representative for the whole tapping sequence were identified. It was furthermore concluded, that the reliability of hot metal composition data is significantly improved by averaging elemental concentrations determined from two samples, each taken at a particular time point. One sampling, however, was found to be adequate for slag. Results from the study also showed a fairly strong correlation between amounts of silicon and carbon, sulphur and carbon, and silicon and sulphur in the hot metal, while a weaker correlation between hot metal temperature and each of these elements was observed.

  • 13.
    Andersson, Margareta
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Appelberg, Jesper
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Tilliander, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    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, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Some Aspects on Grain Refining Additions with Focus on Clogging during Casting2006In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 46, no 6, p. 814-823Article in journal (Refereed)
    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.

  • 14.
    Andersson, Margareta A.T.
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Berlin, D.
    Jönsson, Pär
    KTH, Superseded Departments, Materials Science and Engineering.
    Lownertz, M.
    The influence of different calcium-based additions on desulphurisation and inclusion characteristics2001In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 30, no 3, p. 127-135Article in journal (Refereed)
    Abstract [en]

    The size, distribution, and composition of inclusions during the desulphurisation and deoxidation steps were studied in laboratory experiments. 3 different calcium-based desulphurisation mixtures were used. The number of inclusions and composition of inclusions were then determined using optical microscopy and scanning electron microscopy, respectively. The results show that 2 of the 3 proposed desulphurisation mixtures managed to render lower and roughly equivalent inclusion counts. The results also show that the composition of the inclusions in all 3 samples varied from the beginning to the end of the desulphurisation process. A desulphurisation mixture consisting of Al, CaO, CaCO3 and CaSi produced the overall best results with respect to desulphurisation and inclusion characteristics.

  • 15.
    Andersson, Margareta A.T.
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Hallberg, Malin
    Jonsson, Lage
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Slag-metal reactions during ladle treatment with focus on desulphurisation2002In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 29, no 3, p. 224-232Article in journal (Refereed)
    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.

  • 16.
    Andersson, Margareta
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Hallberg, Malin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jonsson, Lage
    KTH, Superseded Departments, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, Superseded Departments, Applied Process Metallurgy.
    Slag/metal reactionsduring ladle treatment with focus on desulphurisation2000In: 6thInternational Conference on Molten Slags, Fluxes and Salts, 2000Conference paper (Refereed)
  • 17.
    Andersson, Nils
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Tilliander, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jonsson, Lage
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Fundamental decarburisation model of AOD process2013In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 40, no 5, p. 390-397Article in journal (Refereed)
    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.

  • 18.
    Andersson, Nils
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Tilliander, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jonsson, Lage
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Investigating the effectof slag on decarburization in an AOD converter using a fundamental model2013In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 84, no 2, p. 169-177Article in journal (Refereed)
    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.

  • 19.
    Andersson, Nils
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Tilliander, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jonsson, Lage
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Preliminary investigation of influence of temperature on decarburisation using fundamental AOD model2013In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 40, no 7, p. 551-558Article in journal (Refereed)
    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.

  • 20.
    Andersson, Nils Å. I.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Tilliander, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jonsson, Lage T. I.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    A fundamental decarburization model of the AOD processIn: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812Article in journal (Other academic)
  • 21.
    Andersson, Nils Å. I.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Tilliander, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jonsson, Lage T. I.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    An in-Depth Model-Based Analysis of Decarburization in the AOD Process2012In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 83, no 11, p. 1039-1052Article in journal (Refereed)
    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.

  • 22.
    Andersson, Nils Å. I.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Tilliander, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jonsson, Lage T. I.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Investigating the effect of slag on decarburization in an AOD coverter using a fundamental modelIn: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344XArticle in journal (Other academic)
  • 23.
    Andersson, Nils Å. I.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Tilliander, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jonsson, Lage T. I.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Preliminary investigation of temperatur dependencies on decarburization in a fundamental AOD modelIn: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812Article in journal (Other academic)
  • 24.
    Appelberg, Jesper
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Shibata, H.
    Tilliander, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    In situ studies of misch-metal particle behavior on a molten stainless steel surface2008In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 495, no 1-2, p. 330-334Article in journal (Refereed)
    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.

  • 25.
    Arzpeyma, Niloofar
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Ersson, Mikael
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Modeling of post combustion inside the off-gas duct system of the Ovako electric arc furnace2014In: CDF 2014: 10th International Conference on CFD in Oil & Gas, Metallurgical and Process Industries, SINTEF, Trondheim, Norway, 17-19 June 2014, Proceedings, 2014Conference paper (Refereed)
    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.

  • 26.
    Arzpeyma, Niloofar
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Widlund, Ola
    Ersson, Mikael
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Mathematical Modeling of Scrap Melting in an EAF Using Electromagnetic Stirring2013In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 53, no 1, p. 48-55Article in journal (Refereed)
    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.

  • 27.
    Aune, Ragnhild E.
    et al.
    Norwegian Univ Sci & Technol NTNU, Norway.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    The Seetharaman Seminar June 14-15, 2010 in Stockholm, Sweden: Materials Processing Towards Properties2010In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 81, no 10, p. 811-Article in journal (Other academic)
  • 28.
    Bai, Haitong
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Ersson, Mikael
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jonsson, Par
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Effect of TurboSwirl Structure on an Uphill Teeming Ingot Casting Process2015In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 46, no 6, p. 2652-2665Article in journal (Refereed)
    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.

  • 29.
    Bai, Haitong
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Ersson, Mikael
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    The physical and mathematical modelling of swirling flow by turboswirl in an uphill teeming ingot casting process2015In: Proceedings of the 6th International Congress on the Science and Technology of Steelmaking, ICS 2015, Chinese Society for Metals , 2015, p. 473-476Conference paper (Refereed)
    Abstract [en]

    Ingot casting is widely used to produce some certain specialty steel grades. During the process of teeming the liquid steel from the ladle to the mould for a final solidification, the high velocity of the liquid steel can result in an uneven flow pattern either in the vertical and horizontal runners or in the mould. This can cause some serious problems, such as a high erosion of refractory walls or a mould flux entrapment. Here, some research indicate that a swirling flow is beneficial for making the flow pattern even and for reducing turbulence in the runners. Recently, a new swirling flow generation component, TurboSwirl, was applied to improve the flow pattern of the liquid steel as it flows into the mould so that a more stable flow could be obtained. The TurboSwirl is located on the intersection of the horizontal and vertical runners near the mould. It generates a tangential flow that can be used with an expanding nozzle with a flaring angle in order to decrease the vertical flow velocity. Moreover, a mathematical model has been developed to optimize the geometry of the physical model. The results shows that a much more beneficial flow pattern can be obtained by reducing the flaring angle or moving the vertical runner to an off-center position of the TurboSwirl, according to the numerical models. Therefore, a water modelling experiment was built, including the TurboSwirl, one mould and the runners. Tracers will be mixed into the water to detect the flow pattern and the velocity of the fluid would be recorded by a digital motion analysis recorder for later analysis. Firstly, different flaring angles of the expanding nozzle were simulated and compared. The results could supply a good support to the following water modelling experiments and to prove that the TurboSwirl setup produces a much calmer initial filling of the mould, compared to a conventional setup.

  • 30.
    Bai, Haitong
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Ersson, Mikael
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    An Experimental and Numerical Study of Swirling Flow Generated by TurboSwirl in an Uphill Teeming Ingot Casting Process2016In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 56, no 8, p. 1404-1412Article in journal (Refereed)
    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.

  • 31.
    Bai, Haitong
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Ersson, Mikael
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    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 Process2016In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344XArticle in journal (Refereed)
    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. 

  • 32.
    Bai, Haitong
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Ersson, Mikael
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Numerical Study of the Application for the Divergent Reverse TurboSwirl Nozzle in the Billet Continuous Casting ProcessManuscript (preprint) (Other academic)
    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. 

  • 33.
    Bi, Yanyan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Karasev, Andrey
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Investigations of inclusions in ferrochromium alloys2014In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 41, no 10, p. 756-762Article in journal (Refereed)
    Abstract [en]

    Ferrochromium alloys are commonly added during different stages of steelmaking processes according to the specific steel grade being produced. Depending upon the ferrochromium quality, the addition can also lead to a supply of deleterious inclusions to the liquid steel. Therefore, the number, size, morphology and composition of inclusions in LCFeCr and HCFeCr alloys were investigated. The alloy samples were first treated with electrolytic extraction, followed by filtration to gather the inclusions on a film filter. Thereafter, the characteristics of the inclusions and clusters were investigated in three dimensions by SEM in combination with energy dispersive spectroscopy. The results show that the main inclusion types found in LCFeCr alloys are different to those found in HCFeCr alloys. More specifically, the inclusions in LCFeCr alloys were found to consist of Si-Cr-O and Cr-O oxides as well as intermetallic Cr-Fe inclusions. Moreover, the inclusions in HCFeCr alloys were found to consist of Cr-Mn-S, Cr-C-N, Si-Al-Ca-Mg-O and Ca-O-P inclusions. Overall, the inclusions can be divided into two categories depending on the melting point. Furthermore, the possible transformation of different inclusions after their addition to the liquid steel is discussed.

  • 34.
    Bi, Yanyan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Karasev, Andrey
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Three Dimensional Evaluations of REM Clusters in Stainless Steel2014In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 54, no 6, p. 1266-1273Article in journal (Refereed)
    Abstract [en]

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

  • 35.
    Bi, Yanyan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Karasev, Andrey
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Three-dimensional investigations of inclusions in ferroalloys2014In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 85, no 4, p. 659-669Article in journal (Refereed)
    Abstract [en]

    As the requirements on material properties increase, there has been a demand on an additional knowledge on the effect of impurities in the ferroalloys on the properties. Thus, the number, morphology, size, and composition of inclusions in four different ferroalloys (FeTi, FeNb, FeSi, and SiMn) were investigated. This was done in three dimensions (3D) by using scanning electron microscopy in combination with energy dispersive spectroscopy after electrolytic extraction of the ferroalloy samples. The non-metallic and metallic inclusions were successfully analyzed on the surface of film filter. Thereafter, the particle size distribution was plotted for most of the non-metallic inclusions. The non-metallic inclusions were found to be REM oxides in FeTi, FeSi, and SiMn, Al2O3, Ti-Nb-S-O oxides in FeNb and silicon oxides in SiMn. Moreover, the intermetallic inclusions were found to be a Ti-Fe phase in FeTi, Ca-Si, and Fe-Si-Ti phases in FeSi and a Mn-Si phase in SiMn. In addition, the almost pure single metallic phases were found to be Ti in FeTi, Nb in FeNb, and Si in FeSi. As the requirements on material properties increase, the effect of impurities in ferroalloys on the steelmaking process is increasingly becoming more important. The characteristic of inclusions (morphology, number, size, and composition) in ferroalloys investigated in three-dimensional after electrolytic extraction is a good method for studying the evolution of inclusions during steelmaking.

  • 36.
    Bi, Yanyan
    et al.
    KTH.
    Karasev, Andrey V.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Three-dimensional determinations of the non-metallic inclusions in different ferroalloys2014Conference paper (Refereed)
    Abstract [en]

    Ferroalloys are commonly used in the steel industry to alloy or deoxidize the steel during the secondary steelmaking process before casting. Depending upon the ferroalloy quality, the addition can also lead to a supply of deleterious inclusions to the liquid steel. Thus, the number, morphology, size and composition of inclusions in six different ferroalloys (FeTi, FeNb, FeSi, SiMn LCFeCr and HCFeCr) were investigated. This was done in three dimensions (3D) by using SEM in combination with EDS after electrolytic extraction of the ferroalloy samples. Moreover, statistics of extreme values (SEV) were used to determine the largest size of inclusions.

  • 37.
    Bi, Yanyan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Karasev, Andrey Vladimirovich
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Evolution of Different Inclusions during Ladle Treatment and Continuous Casting of Stainless Steel2013In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 53, no 12, p. 2099-2109Article in journal (Refereed)
    Abstract [en]

    The inclusions and clusters in steel samples of two similar steel grades of high-silicon non-calcium treated (HSiNC) stainless steels were investigated and compared during ladle treatment and continuous casting. Samples of liquid steel and slag were taken at different stages of the ladle treatment and casting during two plant trials: Low Al steel (LAI) and High Al steel (HAI). After electrolytic extraction of the steel samples, characteristics of inclusions and clusters (such as morphology, composition, size and number) were investigated in three dimensions (3D) by SEM in combination with EDS. Moreover, the composition of typical inclusions and clusters was analyzed on a polished cross section of steel samples. Spherical (SP), irregular and regular (IR) inclusions and clusters (CL) were observed in the samples from both heats. It was found that the morphology and composition of inclusions and clusters in both heats were significantly changed during the ladle treatment and casting. Most of inclusions (44-98%) in a Low Al steel are MgO-CaO-SiO2-Al2O3 spherical inclusions. The compositions of IR inclusions and clusters in steel samples of a High Al steel were mostly MgO center dot Al2O3 spinet, but also the complex SP inclusions containing Al2O3-MgO-CaO-SiO2. In addition, phase stability diagram based on Darken's quadratic formalism and Redlich-Kister type polynomial was estimated for both heats at a non-infinite solution.

  • 38. Bjurstrom, M.
    et al.
    Tilliander, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Iguchi, M.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Physical-modeling study of fluid flow and gas penetration in a side-blown AOD converter2006In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 46, no 4, p. 523-529Article in journal (Refereed)
    Abstract [en]

    The main fluid-flow pattern that results in a converter with side gas injection was studied using physical modeling. Having roughly the same viscosity as liquid steel, water was used in the experiments. The velocity of the water was determined for different positions in the vessel symmetry plane by laser Doppler velocimetry. Experiments were performed using combinations of three different bath heights and four different gas-flow rates. The results showed penetration of the gas plume into the steel bath both at the tuyere and bath level to increase with an increased gas-flow rate. Also, the penetration depth of the gas both at the tuyere and bath surface level were more affected by an increased gas-flow rate than an increased bath height. Finally, the overall fluid-flow pattern in the system was found to change both with an increased bath height and an increased gas-flow rate.

  • 39.
    Björklund, Johan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Andersson, Margareta
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Equilibrium between slag, steel and inclusions during ladle treatment: comparison with production data2007In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 34, no 4, p. 312-324Article in journal (Refereed)
    Abstract [en]

    The primary purpose of the investigation was to determine whether equilibrium conditions exist between slag and steel and inclusions and steel after silicon deoxidation and aluminium deoxidation. In doing so, the performance of three different models for predicting oxide component activities was also evaluated. The results from the oxide activity models were used to calculate oxygen activities in the steel melt. Industrial data such as steel, slag and inclusion component concentrations, as well as temperature, were used as input to the calculations. One general conclusion drawn was that although the results from the different models showed similar trends, the models did not predict the same actual values for specific calculations. Predicted theoretical equilibrium oxygen activity values were compared with plant measurements of oxygen activity. Here, it was found that the oxygen activity values pertaining to the equilibrium between steel and inclusions were higher than corresponding measured values. The calculations for the equilibrium between the top slag and steel melt, however, resulted in theoretical oxygen activity values considerably lower than corresponding measurements. It was thus concluded that equilibrium conditions did not exist between the top slag and the steel bulk with respect to oxygen. Overall, the models proved useful in predicting oxide activities, but the lack of equilibrium between top slag and molten steel made the calculation of oxygen activity difficult.

  • 40.
    Björklund, Johan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Andersson, Margareta
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    The Influence of Vacuum Treatment on Inclusion Composition: Laboratory Study2010In: High Temperature Materials and Processes, ISSN 0334-6455, E-ISSN 2191-0324, Vol. 29, no 3, p. 189-202Article in journal (Refereed)
    Abstract [en]

    A series of lab scale trials have been carried out with the aim of investigating the effect of vacuum treatment on inclusion chemistry. A ball bearing steel grade (1.47 wt% Cr, 0.96 wt% C) has been melted in a controlled atmosphere in magnesia and alumina crucibles. A laboratory vacuum furnace, which makes it possible to carry out sampling during vacuum treatment, was used. Samples were taken before and during vacuum treatment. Thereafter, the inclusion compositions in the samples were determined using SEM in combination with EDS. The inclusions found were mainly sulphides containing both manganese and chromium. In addition to these, MgO-Al2O3 oxides were found with varying contents of calcium. Furthermore, a few, calcium sulphides were found. Additionally, it was possible to find a small difference in the average inclusion composition in the samples taken before and during vacuum. More specifically, it was seen that the composition of the inclusions becomes more sulphide-rich during vacuum treatment. The change of average inclusion composition was not as large as suggested from theoretical computations and oxides were found at the same extent during vacuum as before. Another finding was that the inclusions from the trial where an alumina crucible was used contained no magnesia, but that the inclusions contained magnesia when a magnesia crucible was used. Even though the effect of vacuum treatment on the inclusion compositions was found to be small, it was concluded that vacuum treatment could not to be neglected when studying inclusions influenced by top slag/metal reactions.

  • 41.
    Björklund, Johan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Andersson, Margareta
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    The Influence of Vacuum Treatment on Inclusion Composition: Theoretical Study2010In: High Temperature Materials and Processes, ISSN 0334-6455, E-ISSN 2191-0324, Vol. 29, no 3, p. 179-187Article in journal (Refereed)
    Abstract [en]

    A theoretical study has been conducted into how inclusion composition is influenced by vacuum treatment. Software for computational thermodynamics has been used to simulate how the conditions in a steel melt changed as a result of a decreased pressure. A case study was made on a low sulphur bearing steel (1.4% Cr, 1.0%C). The calculations show the effect of sulphur, oxygen, carbon and temperature on precipitated phases in the steel melt. The result shows that at low pressure, formation of carbon monoxide takes place. For 5 ppm O and 10 ppm S the CO-gas becomes thermodynamically stable below 40 torr. Oxide phases will be reduced and CaS will be the stable phase.

  • 42.
    Björklund, Johan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Andersson, Margareta
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Nzotta, Mselly
    Uddeholm Tooling AB.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    The Effect of Ladle Treatment on Inclusion Composition in Tool Steel Production2008In: Steel Research International, ISSN 1611-3683, Vol. 79, no 4, p. 261-270Article in journal (Refereed)
    Abstract [en]

    An in-depth SEM-investigation of the inclusion composition change in the ladle refining process during tool steel production was done. Plant trials were carried out at Uddeholm Tooling AB in Hagfors, Sweden. A series of samples was taken during ladle refining, from deslagging through vacuum treatment. The goal was evaluating the effects of the top slag and other process parameters on the inclusion composition during ladle refining. The main conclusion was that normal variations in the process have a large influence on inclusion composition. Furthermore, it was concluded that the MgO content in the top slag had a large influence on the inclusion, composition throughout the whole ladle refining process. Also, the SiO2 content in the ladle slag originating from the EAF-slag, had a noticeable effect on the inclusions. The inclusions belonging to the system Al2O3-CaO-MgO-SiO2 showed a continuous composition change throughout the ladle refining process, from high Al2O3, via MgO-spinel to finally complex types rich in CaO and Al2O3.

  • 43.
    Björklund, Johan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Miki, Takahiro
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Andersson, Margareta
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Effect of Temperature on Oxygen Activity during Ladle Treatment2008In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 48, no 4, p. 438-445Article in journal (Refereed)
    Abstract [en]

    The effect of temperature on oxygen activity in steel was studied in plant trials where temperature and oxygen activity were measured at two depths and at the same time during different parts of ladle refining. The results show that large temperature gradients exist towards the surface of the steel melt for the sampling occasion when no slag is present on the steel surface, as can be expected. It was also observed that the oxygen activity is higher in the lower measurement position than in the upper during the majority of the ladle refining. This is explained by the oxygen activity's temperature dependence. By using the data from this study and previously reported plant trials it was shown that Si-SiO2 or Al-Al2O3 equilibrium controls the oxygen activity.

  • 44.
    Bu, Junfu
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Wang, Cao
    Zhao, Zhe
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Novel BaZr0.5Ce0.3Y0.2O3-δ based proton conductors prepared by spark plasma sinteringManuscript (preprint) (Other academic)
  • 45.
    Bu, Junfu
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Zhao, Z.
    Transport properties of BaZr0.5Ce0.3Y0.2O3-δ proton conductor prepared by spark plasma sintering2016In: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 42, no 3, p. 4393-4399Article in journal (Refereed)
    Abstract [en]

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

  • 46.
    Bu, Junfu
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Zhao, Zhe
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    BaZr0.5Ce0.3Ln0.2O3-δ(Ln=Y, Sm, Gd, Dy) based electrolytes used for intermediate temperature solid oxide fuel cellsManuscript (preprint) (Other academic)
  • 47.
    Bu, Junfu
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Zhao, Zhe
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy. Shanghai Institute of Technology, China.
    Ionic conductivity of dense BaZr(0.5)Ce(0.3)Ln(0.2)O(3-delta) (Ln = Y, Sm, Gd, Dy) electrolytes2014In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 272, p. 786-793Article in journal (Refereed)
    Abstract [en]

    BaZr(0.5)Ce(0.3)Ln(0.2)O(3-delta) (BZCLn532, Ln = Y, Sm, Gd, Dy) based electrolytes were successfully synthesized by a cost-effective solid-state reactive sintering (SSRS) method while using 1.0 wt.% NiO as a sintering aid. Dense pellets of BZCLn532 compounds can be prepared at sintering temperatures of 1600 degrees C (BZCY532) and 1400 degrees C (BZCS532, BZCG532 and BZCD532). The conductivities of the dense BZCLn532 ceramics were tested in dry and wet air at temperatures of 700 degrees C-200 degrees C. On the basis of the obtained results, it could be concluded that the BZCY532-based electrolyte show promise for use as oxygen-ion conductors and proton conductors in intermediate temperature solid oxide fuel cells (ITSOFCs).

  • 48.
    Bu, Junfu
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Zhao, Zhe
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Ceramics.
    Preparation of 30 mol.% Y-doped hafnia (Hf0.7Y0.3O2-delta) using a modified solid-state reaction method2015In: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 41, no 2, p. 2611-2615Article in journal (Refereed)
    Abstract [en]

    A pure and well-crystallized Hf0.7Y0.3O2-delta (YSH) powder was synthesized using a modified solid-state reaction method. Water-based milling and freeze drying process were implemented to facilitate powder synthesis and final densification process. The improved powder performance, in aspects of phase development and sintering behaviour, was investigated by systematic comparison between different powder processing procedures. Dense YSH ceramic material with a relative density of 0.975 was successfully obtained using conventional sintering at 1650 degrees C for 10 h. XRD, SEM and EDS were employed to characterize the synthesized powder and dense YSH ceramics. Dense YSH ceramic possesses a fluorite cubic structure with an a value of 5.1406 angstrom, and the ionic radius of Y3+ in YSH was determined to be 0.1006 nm.

  • 49.
    Bu, Junfu
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Zhao, Zhe
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy. Shanghai Institute of Technology, China .
    Sintering behaviour of the protonic conductors BaZr(x)Ce(0.8-x)Ln(0.2)O(3-delta) (x=0.8, 0.5, 0.1; Ln=Y, Sm, Gd, Dy) during the solid-state reactive-sintering process2015In: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 41, no 2, p. 2558-2564Article in journal (Refereed)
    Abstract [en]

    The protonic conductors BaZr(x)Ce(0.8-x)Ln(0.2)O(3-delta) (x=0.8, 0.5, 0.1; Ln=Y, Sm, Gd, Dy) were successfully prepared using a solid-state reactive-sintering method. NiO (1 wt.%) was added as a sintering aid, and it was proven that NiO produced tremendous enhancement in the densification process. The morphologies of the variously doped BaZr(0.8)Ln(0.2)O(3-delta), BaZr(0.5)Ce(0.3)Ln(0.2)O(3-delta) and BaZr(0.1)Ce(0.7)Ln(0.2)O(3-delta) ceramics, as well as their sintering behaviour, were investigated. The results show that the Ce content in the BaZr(0.8)Ln(0.2)O(3-delta), BaZr(0.5)Ce(0.3)Ln(0.2)O(3-delta) and BaZr(0.1)Ce(0.7)Ln(0.2)O(3-delta) compounds influences the sintering temperature significantly, and a larger Ce content will lead to a lower sintering temperature. In addition, ionic radii of the dopants that are similar to the ionic radii of the B-site will also result in a lowered sintering temperature. Based on the present study, NiO has no influence on the lattice parameters.

  • 50.
    Bu, Junfu
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Zhao, Zhe
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    The effect of NiO on the conductivities of BaZr0.5Ce0.3Y0.2O3-δ based electrolytesManuscript (preprint) (Other academic)
1234567 1 - 50 of 407
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