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  • 1. Andersson, A. J.
    et al.
    Andersson, Margareta A.T.
    KTH, Superseded Departments, Materials Science and Engineering.
    Jonsson, P. G.
    Use of an optimisation model for the burden calculation for the blast furnace process2004In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 33, no 3, p. 172-182Article in journal (Refereed)
    Abstract [en]

    The aim of a burden calculation in the blast furnace process is to compute the amounts of burden materials to be charged for obtaining desired hot-metal and slag composition. Burden calculations are normally based on trial-and-error instead of optimisation. In this study, the use of an optimisation model for a typical blast furnace operation is presented. The yield factors of some components, such as Mn, Si, S, P and V, used in the model have been determined. The more common distribution coefficients have also been studied. Both the yield factor and distribution coefficient values were generally good and showed stable behaviour for repeated periods under similar operational conditions. In this study, the model was found to be an excellent tool for determining burden material amounts and hot-metal and slag compositions for a blast furnace under steady and normal operation conditions. Using an optimising burden calculation model is time efficient, because it demands only 1 calculation procedure instead of a couple calculations as in the case with a trial-and-error method.

  • 2. Andersson, A. M. T.
    et al.
    Jonsson, Lage T. I.
    KTH, Superseded Departments, Materials Science and Engineering.
    Jonsson, P. G.
    A model of reoxidation from the top slag and the effect on sulphur refining during vacuum degassing2003In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 32, no 3, p. 123-136Article in journal (Refereed)
    Abstract [en]

    A 2-dimensional fluid-flow model covering 3 phases (steel, slag and gas) has been augmented to include thermodynamic equations to study simultaneous reoxidation and desulphurization, including macro kinetic behaviour. The numerical simulations were isothermal. Predicted steel and slag component concentrations were compared with plant data from vacuum degassing and the agreement was found to be quite good. When the initial FeO content in the slag was increased, the predicted desulphurization rate decreased, the final sulphur content in the steel increased, and aluminium loss increased. When the temperature was increased, the predicted aluminium loss decreased somewhat. The effect of changes in temperature on the predicted final sulphur content was influenced by the initial FeO content in the top slag. The results show that the model can be used for future work on the dynamic modelling of slag/metal reactions if the initial FeO content is less than 3-4% (by weight).

  • 3.
    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.

  • 4. Bustnes, J. A.
    et al.
    Sichen, Du
    KTH, Superseded Departments, Materials Science and Engineering.
    Seetharaman, Seshadri
    KTH, Superseded Departments, Materials Science and Engineering.
    Investigation of the kinetics of reduction of manganese tungstate by hydrogen2000In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 29, no 4, p. 151-155Article in journal (Refereed)
    Abstract [en]

    The present work was carried out as a part of a research program studying the reduction kinetics of some transition metal tungstates. Manganese tungstate was reduced by hydrogen under isothermal conditions in the temperature range 883-1183 K. The reaction was round to take place in a single step with MnO and W as the solid products. The activation energy for the reduction of manganese tungstate was evaluated to be 92 kJ mol(-1) using the initial reaction rates. This activation energy was compared with the activation energies of the other transition metal tungstates in the light of bond strength of the metal-oxygen bonds.

  • 5. Dupin, N.
    et al.
    Sundman, Bo
    KTH, Superseded Departments, Materials Science and Engineering.
    A thermodynamic database for Ni-base superalloys2001In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 30, no 3, p. 184-192Article in journal (Refereed)
    Abstract [en]

    A thermodynamic database has been developed for Ni-base superalloys. Following the CALPHAD procedure, it is based on the assessment of thermodynamic behaviour of the relevant constituting sub-systems of the complex system of interest. The current database contains 7 elements: Al, Co, Cr, Ni, Ti, W, Re. The thermodynamics of the gamma and gamma' phases are modelled with a single Gibbs energy function taking into account the crystallographic relation between these two phases. The formalism of the thermodynamic models used is briefly introduced. A few phase diagrams calculated with the current database in assessed binary and ternary systems are presented. Some experiments available in higher order systems are compared with the results of calculations with the current database. The ability of extrapolation of the database is verified for solid state equilibria as well as for solidification behaviour (liquidus temperature and partition ratios). The introduction of Mo and Ta to the current database is in progress. Other elements (Nb, Fe, Zr, Hf, C, B, . . .) are planed to be introduced.

  • 6.
    Ekbom, Lars B.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Antonsson, Tomas
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Ekbom, M
    Computer simulation of solution and growth processes during the initial stage of liquid phase sintering of tungsten heavy metal2005In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 34, no 5, p. 312-316Article in journal (Refereed)
    Abstract [en]

    In the initial stage of liquid phase sintering, particle dissolution and growth processes occur. The melting matrix penetrates the solid particle agglomerates. A fraction of the particles dissolves in the liquid matrix phase and the original powder size will initially be reduced. At the same time the agglomerates of particles are effectively separated. In a second stage larger particles grow in equilibrium with the matrix, whilst smaller, pure particles dissolve into the matrix and the mean particle size increases. When an equilibrium is reached, the solid particles start to grow in the liquid matrix phase in accordance with the ripening process. The initial stages of liquid phase sintering have been investigated by short time sintering under microgravity and are presented in a series of micrographs. Mathematical models for the 3 stages have been developed. Computer simulations of these different stages in the solution and growth processes have been used to visualise the change in particle size distribution.

  • 7. Emi, T.
    et al.
    Seetharaman, Seshadri
    KTH, Superseded Departments, Materials Science and Engineering.
    Future steelmaking plant with minimized energy consumption and waste evolution2000In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 29, no 5, p. 185-193Article in journal (Refereed)
    Abstract [en]

    A view is presented on future BF-BOF type and EF type steelmaking plants. The former and the latter include, respectively, rationalized process steps for a mass production and small lot production of quality steels at reduced costs. Integration of the 2 types of plants is discussed for better synergy effects. Emphasis is placed on minimizing the consumption of primary energy and evolution of wastes such as dust, slag and gases, with a consideration given for maximized utilization of the wastes. Metallurgical key issues for future R & D to achieve improved productivity and wastes evolution are also suggested.

  • 8.
    Eriksson, Robert
    et al.
    KTH, Superseded Departments, Metallurgy.
    Jönsson, Pär
    KTH, Superseded Departments, Materials Science and Engineering.
    Gustafsson, A.
    Determination of inclusion characteristics in 'low-carbon' steel during up-hill teeming2004In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 33, no 3, p. 160-171Article in journal (Refereed)
    Abstract [en]

    Clean steel production requires good control of the size distribution and the composition of the inclusions at all stages of the steel making process. So far, there exists very little information on the behavior of the inclusion population during ingot casting of steel. Therefore, this study focus on providing information on the inclusion population before and during up-hill teeming of 'low-carbon' steel, based on plant trails carried out at Ovako Steel's facilities in Hofors, Sweden. Liquid steel samples were acquired from the casting ladle just before the start of the filling of the ingot molds and from the rising steel in the molds during the filling of the molds. Thereafter, the inclusion compositions for the different size classes were determined using a scanning electron microscope equipped with energy dispersive X-ray. It was found that the inclusion compositions were more complex in the samples taken in the mold in comparison to the ones taken in the ladle. In some cases large exogenous inclusions most likely formed due to a reaction with the mold flux were found. When a mold was filled without mold flux reoxidation of the steel due to reaction with the atmosphere took place. The inclusion size distributions were also determined using light optical microscopy and classified according to the Swedish standard SS111116 (JK chart II). The number of inclusions found in the sample taken in the mold were higher than in the sample taken in the ladle. The general conclusions are that more in-depth research is necessary to understand the reactions taking place during filling of an ingot.

  • 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.
    Fredriksson, Hasse
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Hansson, K.
    Olsson, A.
    On the mechanism of liquid copper penetration into iron grain boundaries2001In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 30, no 1, p. 41-50Article in journal (Refereed)
    Abstract [en]

    The penetration of liquid copper into iron grain boundaries has been experimentally analysed. During the penetration, Cu diffuses into the iron grains. In this case, a Kirkendall effect is created, leading to vacancies which diffuse to the grain boundaries where they condense. A grain boundary crack is formed, which will be filled with liquid Cu. The driving force for penetration of the Cu-liquid into the grain boundary is the condensation of vacancies and the surface/interface free energy change. A theoretical model describing the penetration rate is derived and a good agreement between theory and experiments was achieved. The model is general and can be used to explain liquid metal embrittlement.

  • 11.
    Fredriksson, Patrik
    KTH, Superseded Departments, Metallurgy.
    Differential thermal analysis of the iron-platinum system2004In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 33, no 3, p. 183-188Article in journal (Refereed)
    Abstract [en]

    In the present work, a phase diagram investigation of binary Fe-Pt alloys was carried out by means of the differential thermal analysis method. 12 different alloys were investigated with a NETZSCH STA 449C Jupiter((C))DCS unit in the temperature range of 300-1673 K and 3 alloys with a Setaram HTC 1800 K-DSC 2000 K calorimeter in the temperature range of 3001988 K, respectively. The measurements were carried out in Ar as well as H-2 atmospheres. The results obtained show a good agreement with previous investigations and bring new information for order/disorder phase transitions for FePt and FePt3 alloys, respectively, in the temperature range 1420-1610 K. Use of He instead of H-2 in some of the trials showed that the impact of hydrogen on the measurements was insignificant.

  • 12.
    Fredriksson, Patrik
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Seetharaman, Seshadri
    KTH, Superseded Departments, Materials Science and Engineering.
    On the standard Gibbs energy of formation of CoO2004In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 33, no 6, p. 305-309Article in journal (Refereed)
    Abstract [en]

    The standard Gibbs energy of formation of CoO was determined by the galvanic cell (-) Pt, Fe(s), 'FeO'(s)//ZrO2 (partially stabilised//CoO(s), Co(s), Pt (+) with CaO or Y2O3) in the temperature range 1052-1488 K. The results are compared with earlier reported values. An equation for the standard Gibbs energy change for the reactions Co(s) + 1/2O(2)(g) = CoO(s) and Co(s) + (O) under bar (Co, fcc) = CoO(s) is recommended based on the present

  • 13.
    Fredriksson, Patrik
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Seetharaman, Seshadri
    KTH, Superseded Departments, Materials Science and Engineering.
    Thermodynamic studies of some Fe-Pt alloys by the solid electrolyte galvanic cell method2001In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 30, no 4, p. 258-264Article in journal (Refereed)
    Abstract [en]

    In the present investigation, the thermodynamic activities of iron in iron-platinum solid alloys were measured by the solid electrolyte galvanic cell method in the temperature range 1073-1273 K. The galvanic cell employed can be represented as (-) Pt, Fe(s), Feto(s) // ZrO2(11 mol pct CaO) // FetO(s), Fe-Pt alloys, Pt(+) The experimental set-up as well as the satisfactory performance of the galvanic cell were validated by measuring the standard Gibbs energy of formation of CoO in equilibrium with Cc in the same temperature range by replacing the working electrode by a Co, CoO mixture. 6 different Fe-Pt alloys covering the entire composition range were studied and the results are compared with earlier thermodynamic studies available in the literature. The present experimental results are found to be in general agreement with those of Alcock and Kubik. The values were fitted into a regular solution description in order to estimate the enthalpies of mixing Pt and Fe in the solid alloys.

  • 14.
    Grip, Carl-Erik
    et al.
    Luleå Tekniska Universitet.
    Jonsson, Kjell Olov
    Eriksson, Sven
    Jonsson, Lage
    MEFOS, Luleå, Sweden.
    Jönsson, Pär
    KTH, Superseded Departments, Applied Process Metallurgy.
    Pan, Yuhua
    Theoretical and practical study of thermal stratification and drainage in ladles of different geometry2000In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 29, no 1, p. 30-38Article in journal (Refereed)
    Abstract [en]

    SSAB Lulea, SSAB Oxelosund, MEFOS and Lulea University of Technology have cooperated in developing theoretical models for prediction of thermal stratification and drainage in steel ladles. Predicted results have been verified by measurements done in production ladles with heat weighs of 105 and 200 tonne as well as in a 7-tonne pilot plant ladle. The thermal stratification was measured by thermocouples at different depths. The drainage flow was studied by means of tracer experiments. Numerical simulation models of the steel flow were developed for 7, 105 and 200 tonne steel ladles. The agreement between predictions and measurements was found to be good. The conclusion is that CFD simulation gives a good prediction of stratification and drainage flows in production ladles.

  • 15.
    Grip, Carl-Erik
    et al.
    Luleå Tekniska Universitet.
    Jonsson, Lage
    MEFOS, Luleå, Sweden.
    Physical behavior of slag in a 107-tonne ladle: production scale experiments and theoretical simulation2003In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 32, no 3, p. 113-122Article in journal (Refereed)
    Abstract [en]

    The combined movement of steel, slag and gas in a ladle has been studied with the aid of a multiphase CFD model and measurements in production scale. Comparison of model data and measurements in a production ladle has been carried out for three cases: The ‘open eye’ created during gas stirring, the mixing of top slag during gas stirring in the CAS-OB and finally for studying sculling phenomena. It was found that the simulated ‘open eye’ appears as a central slag-free zone with a surrounding ‘splash zone’ characterized by the fact that steel is found on top of the slag. The simulated ‘open eye’ corresponds to the ‘splash zone’. The predicted gas stirring in CAS-OB gives an efficient stirring of the top slag also. This was confirmed by noting that slag samples taken from the ladle seem to be representative of the mean slag composition. Finally, streamlines during stirring have been compared with sculling and wear observed in the production ladle. Good agreement was obtained.

  • 16. Gustavsson, J.
    et al.
    Andersson, Margareta A.T.
    KTH, Superseded Departments, Materials Science and Engineering.
    Jönsson, Pär
    KTH, Superseded Departments, Materials Science and Engineering.
    Effect of selected model parameters on predicted RAFT data2002In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 31, no 5, p. 328-341Article in journal (Refereed)
    Abstract [en]

    A new raceway adiabatic flame temperature (RAFT) model has been developed where the effect of injected BOF slag has been considered. A parameter study was performed to evaluate the influence of (i) coke temperature factor, (ii) degree of silica reduction, (iii) coal powder burning degree, (iv) reduction degree of some components in injected BOF slag when leaving raceway, (v) enthalpy of coke burning and (vi) Cp value of coke. The coke burning enthalpy was found to have the largest influence on the absolute value of RAFT. In Swedish blast furnaces, the RAFT is usually kept relatively constant by adjusting the oxygen content in the blast. Therefore, the exchange ratios between the oxygen content in blast and the injected material to retain RAFT were predicted. The burning degree of coal powder was found to have the largest influence when coal powder was evaluated. Silica and silicon carbide reduction was found to have the largest influence when a change of BOF slag rate was evaluated.

  • 17. Gustavsson, J.
    et al.
    Hahlin, P.
    Jönsson, Pär
    KTH, Superseded Departments, Materials Science and Engineering.
    Meltdown behaviour of pellets reduced in a laboratory reduction furnace2003In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 32, no 2, p. 100-111Article in journal (Refereed)
    Abstract [en]

    The meltdown behaviour of pellets reduced under different conditions in a reduction under load furnace has been examined. The pellet type, temperature increase rate, the gas flow and the applied load over the crucible were varied between trials. Samples from 12 trials interrupted just before meltdown were studied under an optical microscope and it was found that all iron oxides in the samples were reduced to iron. After the etching of the samples the carbon content was estimated. The carbon content differs within the samples as well as between the samples. A correlation exists between the average carbon content in a sample and the meltdown temperature. Some differences in the iron structure and the carbon content between the crucible wall and the crucible centre are discussed. Because no big difference in carbon content was found between the crucible wall and the crucible centre most of the carbon in the samples probably dissolves in the metal by a gas reaction where CO gas forms carbon and CO2 .

  • 18. Hallberg, M.
    et al.
    Jonsson, P. G.
    Jonsson, Lage T. I.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Eriksson, R.
    Process model of inclusion separation in a stirred steel ladle2005In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 34, no 1, p. 41-56Article in journal (Refereed)
    Abstract [en]

    A mathematical model, which can be used as a process model in production, was developed to predict total oxygen content and size distribution of non-metallic inclusions in an agitated steel melt. Using a given pre-deoxidation total-oxygen-content value and calculated velocity and turbulence data (induction or gas stirring), model output can be generated as a function of stirring time. Predicted initial inclusion size distributions were in good agreement with inclusion size distributions quantitatively determined by light optical microscopy and classification according to the Swedish standard SS 11 11 16. Results from simulations carried out for the two types of stirring indicated that the model can predict total oxygen content and inclusion size distribution as a function of time for induction and gas stirring in an acceptable way.

  • 19. Hansson, K.
    et al.
    Droujevski, M.
    Fredriksson, Hasse
    KTH, Superseded Departments, Materials Science and Engineering.
    Hot ductility of an Fe-10%Ni alloy during penetration of copper2002In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 31, no 4, p. 256-267Article in journal (Refereed)
    Abstract [en]

    Today's available theories for hot crack formation are based on the fact that hot cracks are formed in the presence of liquid films in the interdendritic areas or at the grain boundaries, which are exposed to tensile stress. Copper is well known to cause hot shortness in steels. In order to study how the liquid embrittles the material, high-temperature tensile tests were performed at two strain rates during the penetration of liquid copper into Fe-10%Ni. The penetration distance was measured in samples that were exposed to strain without fracturing. The ductility (area reduction), strain and ultimate tensile stress were determined. Microprobe analysis was performed on the fractured samples. The transition temperature of ductility was found at 1400-1450degreesC without copper penetration whereas it occurred at 1025-1078degreesC during the penetration of copper, i.e. copper starts to embrittle at a temperature below its melting point. The microprobe measurements showed that the diffusion rate of copper into Fe-10%Ni was enhanced when the lattice was strained. The results are discussed in terms of a new theory concerning vacancy formation and condensation as the dominating mechanism for hot crack formation during solidification.

  • 20.
    Hellberg, Per
    et al.
    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
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Mathematical modelling of the injection of coke oven gas into a blast furnace tuyere2005In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 34, no 5, p. 269-275Article in journal (Refereed)
    Abstract [en]

    A fundamental mathematical model of the tuyere in a blast furnace has been developed earlier. In this study, the model is mainly used to predict the combustion reactions in the tuyere when coke oven gas is injected through lances located inside the tuyere. The combustion reaction is modelled using a simple reaction scheme with 3 possible reactions that can occur. The influence of the following parameters on the predicted velocities, temperatures and composition of the gas at the tuyere outlet is studied in this paper: (i) injection amount of coke oven gas, (ii) the use of 1 or 2 injection lances and (iii) the influence of the injection angles when using 2 injection lances. It is concluded that the maximum injecting amount using 1 and 2 lances is 10,000 nm(3)/h and 15,000 m(3)/h, respectively. The combustion conditions are better when using 2 injection lances are compared to 1 injection lance and the predicted results are not affected to a large degree when the injection angles are changed.

  • 21.
    Jansson, Sune
    et al.
    Arvika Gjuteri AB.
    Brabie, Voicu
    Dalarna University, Campus Borlänge.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Corrosion mechanism and kinetic behaviour of MgO-C refractory material in contact with CaO-Al2O3-SiO2-MgO slag2005In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 34, no 5, p. 283-292Article in journal (Refereed)
    Abstract [en]

    The rate of dissolution of solid MgO-C into liquid CaO-Al2O3-SiO2-MgO slag at different temperatures was studied under conditions of forced convection by rotating cylindrical refractory specimens in a stationary crucible containing molten slag. The corrosion rate was calculated from the change in diameter of the cylindrical refractory specimens. The specimens were rotated for 15-120 min at a speed of 100-400 rpm in the molten slag. The rate of corrosion was found to increase with an increase in temperature and rod rotation speed, and to decrease when the slag was nearly saturated with MgO. The experimental results support the assumption that the diffusion of magnesium oxide through the slag-phase boundary layer controls the corrosion process. The corrosion mechanism seems to be the dissolution of refractory material into the slag followed by penetration of pores and grain boundaries and dispersion of the grains into the slag.

  • 22. Jauhiainen, Anu
    et al.
    Jonsson, Lage
    KTH, Superseded Departments, Applied Process Metallurgy.
    Modelling of alloy mixing into steel - The influence of porous plugplacement in the ladle bottom on the mixing of alloys into steel in agas-stirred ladle – A comparison made by numerical simulation2001In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 30, p. 242-253Article in journal (Refereed)
  • 23.
    Jönsson, Pär
    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.
    A model of gas-stirred ladle1995In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 24, no 5-6, p. 194-206Article in journal (Refereed)
    Abstract [en]

    Background/aims: A research program with the objective of studying the separation of non-metallic inclusions is currently being undertaken by the Swedish Steel Producers' Association. The aim is to develop a pc-based model that can easily be used by the participating steel companies. important inputs to the model are, among other parameters, data for steel velocities and dissipation of turbulent kinetic energy. Results and conclusion: A 2-dimensional two-phase mathematical model for a gas-stirred ladle has been developed. This model differs from existing models in that the nozzle and plume areas have been modeled more realistically. The predicted data of gas fraction and velocity in a water model agree well with experimental data found in the literature. The calculated surface velocities in an argon gas-stirred ladle are of the same order of magnitude as experimental data. However, the experimental surface velocity measurements are not sufficiently accurate to permit a closer comparison. Predicted bubble rising velocities for an argon-stirred steel ladle agree well with existing experimental data.

  • 24. Luo, C. H.
    et al.
    Ståhlberg, Ulf
    KTH, Superseded Departments, Production Engineering.
    An alternative way for evaluating the deformation of MnS inclusions in hot rolling of steel2002In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 31, no 3, p. 184-190Article in journal (Refereed)
    Abstract [en]

    The behavior of MnS inclusions during flat hot rolling of steel has been studied. Experiments were carried out in a four-high mill. The workpiece was up to a nominal reduction in height of 85% in four passes, at rolling temperatures of 700-1200degreesC with interpass reheating. The relative plasticity and orientation of inclusions were quantitatively assessed by means of an image-processing tool. Finite element analyses were performed in order to scrutinize the concept of 'relative plasticity', which is based on dimensional change of the inclusion, Furthermore, inclusion reorientation is discussed.

  • 25. Mahmoudi, J.
    et al.
    Vynnycky, M.
    Fredriksson, Hasse
    KTH, Superseded Departments, Materials Science and Engineering.
    Modelling of fluid flow, heat transfer and solidification in the strip casting of a copper base alloy - (III). Solidification - a theoretical study2001In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 30, no 3, p. 136-145Article in journal (Refereed)
    Abstract [en]

    A finite-volume model has been developed and applied to analyse the solidification process of pure copper in the mould region of a continuous strip casting machine. The model was produced with the commercial program GFX, which allows this non-linear, turbulent problem to be simulated using a modified version of the k-epsilon turbulence model. The fluid flow, temperature and heat flux distributions in the mould region of the easter were computed. The shape and location of the solidification front were also determined. The effects of operating parameters, such as casting speed, superheat and the assumed values for the latent heal of fusion on the shape and location of the solidification front were investigated.

  • 26. Morales, R.
    et al.
    Tavera, F. J.
    Aune, Ragnhild E.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Hydrogen reduction of complex oxides - a novel route toward the production of nanograined alloys and intermetallics2005In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 34, no 2, p. 108-115Article in journal (Refereed)
    Abstract [en]

    One of the major obstacles in the incorporation of nanomaterials in high technology is the lack of new processes for the bulk production of the materials with compositions tailored to suit the application. Oxides can potentially be reduced to metals, intermetallics or alloys by hydrogen or natural gas. The formation of homogeneous alloys and intermetallics by this method has been confirmed by a number of experimental studies. The kinetics of hydrogen reduction of pure oxides of transition metals as well as complex tungstates, molybdates, titanates, aluminates and chromate were investigated by thermogravimetry. The formation of homogeneous alloys and intermetallics was confirmed by these studies. Arrhenius activation energies of the reduction reactions could be linked to the stabilities of the complex oxides. The products were found to have nanograin structure. Bulk processing through hydrogen reduction route was examined in the case of iron molybdate using a fluidized bed reactor.

  • 27. Mukai, K.
    et al.
    Matsushita, Taishi
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Motion of fine particles in liquid caused by interfacial tension gradient in relation to metals separation technologies2005In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 34, no 2, p. 137-142Article in journal (Refereed)
    Abstract [en]

    Some ideas for promoting the metal separation process are proposed based on the consideration of the force caused by interfacial tension gradient as a driving force. The force drives the particle toward the direction of the lower interfacial tension side, which has been confirmed by water model experiments. Therefore, it is possible to move fine metal particles by producing interfacial tension gradient between fine metal particles and molten slag. The force in molten slag-metal (iron) system was evaluated under some assumptions. The evaluation indicates that the force is enough large to engulf the fine metal particle by the interface between metal particle and slag for promoting metal separation process.

  • 28. Neelakantan, V. N.
    et al.
    Sridhar, S.
    Mills, K. C.
    Sichen, Du
    KTH, Superseded Departments, Materials Science and Engineering.
    Mathematical model to simulate the temperature and composition distribution inside the flux layer of a continuous casting mould2002In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 31, no 3, p. 191-200Article in journal (Refereed)
    Abstract [en]

    A model is presented to predict the mass transport and heat transfer in a continuous casting mould flux bed. Physically consistent micromodels for carbon burning, evaporation of volatiles and thermophysical properties in the mould flux layer have been combined with a one-dimensional finite-difference model of the continuous casting mould flux bed. The sensitivity of the model to bed height, flux consumption rate, carbon burning and powder particle size is investigated for a mould flux composition corresponding to an industrial casting powder.

  • 29. Nzotta, M. M.
    et al.
    Andreasson, M.
    Jönsson, Pär
    KTH, Superseded Departments, Materials Science and Engineering.
    Seetharaman, Seshadri
    KTH, Superseded Departments, Materials Science and Engineering.
    A study on the sulphide capacities of steelmaking slags2000In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 29, no 4, p. 177-184Article in journal (Refereed)
    Abstract [en]

    This report is on the application of a mathematical model for the predictions of sulphide capacities of steelmaking slags. The model was Verified earlier on laboratory scale. Predictions agreed well with experimental data. In this work, an attempt was made to calculate sulphide capacities from plant data (chemical analyses of steel and slag). Difficulty was encountered in determining the oxygen activity in the steel melt as well as the activity of alumina in the slag phase when calculating the sulphur distribution ratio. However, good agreement was obtained between predicted and experimentally determined sulphur distribution data, when the activity of oxygen in the metal phase was assumed to be 1x10(-4) for the model calculations.

  • 30. Sheng, Dong-Yuan
    et al.
    Söder, Mats
    KTH, Superseded Departments, Materials Science and Engineering.
    Jönsson, Pär
    KTH, Superseded Departments, Materials Science and Engineering.
    Jonsson, Lage
    Modeling micro-inclusion growth and separation in gas-stirred ladles2002In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 31, no 2, p. 134-147Article in journal (Refereed)
    Abstract [en]

    Mathematical models of inclusion behavior in stirred ladles are useful both for increasing our fundamental understanding of the growth and removal of inclusions as well as for future use in process control. This study reports on some efforts to use both static and dynamic modeling to better understand inclusion behavior in gas-stirred ladles. A computational-fluid-dynamics mathematical model of a gas-stirred ladle was developed earlier. In the investigation covered in this report, instantaneous fluid-flow results from the model were used in combination with inclusion growth and removal theories in order to study the importance of bubbles on inclusion flotation. The study results proved to be highly dependent on the theory used to describe bubble flotation. The model of the gas-stirred ladle was also used together with the inclusion theories to study the transient behavior of inclusions during growth and removal. The dynamic simulation results indicated that inclusion concentration gradients exist. The most important research task in the near future is to verify static and dynamic modeling results of inclusion behavior during stirring with experimental data. Here, the authors feel that carefully performed plant trials could provide useful information.

  • 31.
    Sheng, D.Y.
    Westinghouse Electric Sweden.
    Modelling micro-inclusion growth and separation in gas-stirred ladles2002In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 31, no 2, p. 134-Article in journal (Refereed)
  • 32. Solhed, Henrik
    et al.
    Jonsson, Lage
    KTH, Superseded Departments, Applied Process Metallurgy.
    An investigation of slag floatation and entrapment in acontinuous-casting tundish using fluid-flow simulations, sampling and physicalmetallurgy2003In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 32, p. 15-32Article in journal (Refereed)
  • 33. Ssemakula, H.
    et al.
    Ståhlberg, Ulf
    KTH, Superseded Departments, Production Engineering.
    Grain size as influenced by process parameters in copper extrusion2001In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 30, no 4, p. 232-237Article in journal (Refereed)
    Abstract [en]

    Today, different methods and materials are investigated for the manufacturing of large canisters meant for encapsulation of nuclear waste. One method of interest includes hot extrusion of coarse-grained copper ingots. It has been shown that the grain size in the final product must be small in order to enable ultrasonic testing and to guarantee high resistance towards creep and corrosion. Different codes are being developed for predicting the final grain size as influenced by temperature, strain and strain rate. In the present work, these parameters have been determined by simulations for different material elements during extrusion of cylindrical copper billets. Elements, located at various distances from the central axis of the initial workpiece, were traced from the inlet to the outlet of the die by utilizing the FE-code FORM2D. In this way, the parameters describing the deformation history of the elements were determined as functions of time. Experiments corresponding to the simulations were carried out. Starting with billets in as-cast condition, the final grain sizes were evaluated. It is concluded that the initial grain size of an as-cast cylindrical billet is heavily decreased for all the extrusion conditions studied. The investigation was carried out for different working temperatures, 550, 650 and 750 degreesC and extrusion ratios, 10 and 15. The final grain size was found within the interval 23-37 mum. The smallest grain size was, for each working condition, located close to the surface of the extrudate where the largest strains and temperature increases occurred. Low extrusion temperatures gave the best results.

  • 34.
    Sterneland, Therese
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Aune, Ragnhild E.
    KTH, Superseded Departments, Materials Science and Engineering.
    Seetharaman, Seshadri
    KTH, Superseded Departments, Materials Science and Engineering.
    Thermodynamic investigation of Co-Cr alloys. II.: Heat capacity measurements in the temperature interval 318-1660 K2003In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 32, no 5, p. 233-240Article in journal (Refereed)
    Abstract [en]

    The thermodynamic properties of several Co-Cr alloys have been determined in the temperature interval 318-1660 K using differential scanning calorimetric (DSC) technique. The compositional range of the alloys investigated extended from 10 to 90 wt% Cr. Heat capacity equations, C-p (J/mol K) = A + B . T (K), were derived in the temperature interval of interest to fit the experimental data. The experimental Cp values are compared with those from the Neumann-Kopp rule. The phase transformations observed in the present measurements are discussed in the light of the phase diagram <LF>information available in the literature for the Co-Cr binary system.

  • 35.
    Söder, Mats
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Jönsson, Pär
    KTH, Superseded Departments, Materials Science and Engineering.
    Alexis, Jonas
    KTH, Superseded Departments, Materials Science and Engineering.
    Most relevant mechanisms of inclusion growth in an induction-stirred ladle2002In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 31, no 3, p. 210-220Article in journal (Refereed)
    Abstract [en]

    The purpose of this study has been to theoretically evaluate which inclusion growth mechanisms are important in an inductively stirred ladle. This has been done using data from a computational fluid dynamics model of a real ladle. The data was utilized as the input to the different collision equations. It was concluded that diffusion of oxygen and deoxidant to the inclusion surface, diffusion coalescence and Brownian motion collisions contribute very little to growth of inclusions during the stirring period in the ladle. This was in accordance with earlier findings in the literature. This study also showed that laminar shear collisions could be excluded from a growth model. The major growth mechanism is turbulent collisions. It was also shown that a 700-A stirring current leads to more growth due to turbulent collisions than a 500-A stirring current. The importance of a correct value of the collision efficiency coefficient for turbulent collisions was pointed out. If a large difference in inclusion size exists then collisions due to difference in buoyancy (Stokes collisions) also need to be considered in a growth model. Finally, it is concluded that the variation in fluid flow and turbulent properties in different parts of the ladle should be incorporated into a growth model, since it can affect average turbulent collision volumes by 25-30%.

  • 36.
    Tripathi, Nagendra
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Sichen, Du
    KTH, Superseded Departments, Materials Science and Engineering.
    Non-metallic inclusions in the ingot and final products of a medium-carbon tool steel2004In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 33, no 6, p. 362-369Article in journal (Refereed)
    Abstract [en]

    The present work was carried out at Uddeholm Tooling AB, Sweden to study the inclusion characteristics in the ingot and the final product of a 'medium-carbon' tool steel. Steel samples were taken during the mould filling, after casting and from the final product. The inclusion populations in the steel samples were examined under a light optical microscope. The chemical compositions of the inclusions were analysed using a scanning electron microscope attached with EDX The steel samples taken during the mould filling were found to contain alumina-based inclusions, originated from the erosion of the closing gates, the inner nozzle and the outer nozzle. The analyses of the steel samples from the solidified ingot revealed a non-uniform distribution of inclusions. The inclusion population was found to be highest in the centre part of the ingot and lowest between the central line and the mould wall. The steel samples from the bars of the final products were taken at an identical position in each case, corresponding to the central part of the ingot. The inclusion populations were found to be somewhat higher in the final product in comparison with the populations before casting. The inclusion populations in the final products were also found to increase with the ladle age.

  • 37. Wang, X. D.
    et al.
    Li, W. C.
    Seetharaman, Seshadri
    KTH, Superseded Departments, Materials Science and Engineering.
    Thermodynamic study and synthesis of gamma-aluminum oxynitride2002In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 31, no 1, p. 1-6Article in journal (Refereed)
    Abstract [en]

    This paper presents the results of the investigation of the thermodynamic properties of I-aluminum oxynitride (AION). The phase relations and thermodynamic properties of NON were analyzed and the Gibbs energies of NON with different compositions and temperatures were calculated by a thermodynamic quasi-parabola rule. Potential phase diagrams of Al-O-N system at different conditions have also been calculated. The synthesis conditions of NON have been determined. NON was synthesized by sintering the starting materials at 25MPa in N-2 flow at 2073K for 3h. Crystal characteristics and microstructures of AION were determined.

  • 38.
    Yang, Weihong
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Blasiak, Wlodzimierz
    KTH, Superseded Departments, Materials Science and Engineering.
    Combustion performance and numerical simulation of a high-temperature air-LPG flame on a regenerative burner2004In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 33, no 2, p. 113-120Article in journal (Refereed)
    Abstract [en]

    High-temperature air combustion is attracting great interest in the metallurgical industry lately as its claimed benefits include large energy saving, low air emissions, increased product quality and increased productivity. This paper presents a numerical study of combustion performance in a semi-industrial test furnace equipped with a regenerative burner and with a conventional turbulent jet burner. The numerical calculation is also validated by experiment. In this regard, flow field was calculated with k-epsilon turbulence model, the model of combustion employed the eddy dissipation concept with a two-step mechanism to describe chemical reactions; radiation was handled using the discrete transfer method. The results indicate that equipping a furnace with high-cycle regenerative burner systems can provide more uniform gas temperature profiles, a higher energy utilizing efficiency, a low NOx emission, a larger flame, the low maximum local heat release and the possibility of low combustion noise.

  • 39.
    Yang, Weihong
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
    Mörtberg, Magnus
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
    Blasiak, Wlodzimierz
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
    Influences of flame configurations on flame properties and NO emissions in combustion with high-temperature air2005In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 34, no 1, p. 7-15Article in journal (Refereed)
    Abstract [en]

    High-temperature air combustion using the high-cycle generator is attracting great interest in mettalurgical industries. Flame configurations play a very important role when a modern regenerative burner system is adopted in an industrial furnace because multi-burners are required. Numerical studies of combustion in a semi-industrial scale test furnace equipped with two sets of two-flame high-cycle regenerative system have been performed and results were compared with experimental values. Influences of flame configurations on combustion properties and NO emissions of LPG with high-temperature air were numerical studies as well as excess air ratio. The flame volume and size were figured out by a parameter named as oxidation mixture ratio. It is found that the flame configurations have strong influences on the combustion and flame properties as well as NO emission. Increasing the excess air ratio leads to increasing of NO emission. Lesser the ratio of fuel/air injection momentum larger is the NO production.

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

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

  • 41. Zhu, M-Y
    et al.
    Jones, T
    Sichen, Du
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Modelling study of slag foaming by chemical reactio2001In: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 30, p. 51-56Article in journal (Refereed)
1 - 41 of 41
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