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  • 1. Abas, R. Abdul
    et al.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Thermal diffusivity of sintered stainless steel-alumina composites2006In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 37, no 4, p. 513-518Article in journal (Refereed)
    Abstract [en]

    Thermal diffusivity measurements were carried out as a function of temperature on sintered AISI 304 stainless steel-alumina composites having various compositions (0.001, 0.01, 0, 1, 1, 2, 3, 5, 7, 8, and 10 wt pct Al2O3). The measurements were carried out between room temperature and 1473 K. The thermal diffusivity and the thermal conductivity were found to increase with temperature in all the composite specimens. The thermal diffusivity was found to decrease with increasing weight fraction of alumina. This tendency can clearly be seen at temperatures above 755 K. The experimental results are in good agreement with the simple rule of mixture, the Eucken equation, and the Ohm's law model developed by Hayashi et al. at weight fractions of alumina below 5 wt pct. Beyond this composition, the thermal diffusivity/conductivity shows a large discrepancy from the models. This could probably be attributed to the accumulation of alumina particles during cooled pressing and sintering.

  • 2.
    Abdul Abas, Riad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Thermal Diffusivity of Sintered Stainless steel-Alumina Composite2006In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 37, no 4, p. 513-518Article in journal (Refereed)
    Abstract [en]

    Thermal diffusivity measurements were carried out as a function of temperature on sintered AISI 304 stainless steel-alumina composites having various compositions (0.001, 0.01, 0, 1, 1, 2, 3, 5, 7, 8, and 10 wt pct Al2O3). The measurements were carried out between room temperature and 1473 K. The thermal diffusivity and the thermal conductivity were found to increase with temperature in all the composite specimens. The thermal diffusivity was found to decrease with increasing weight fraction of alumina. This tendency can clearly be seen at temperatures above 755 K. The experimental results are in good agreement with the simple rule of mixture, the Eucken equation, and the Ohm’s law model developed by Hayashi et al. at weight fractions of alumina below 5 wt pct. Beyond this composition, the thermal diffusivity/conductivity shows a large discrepancy from the models. This could probably be attributed to the accumulation of alumina particles during cooled pressing and sintering.

  • 3.
    Ahmed, Hesham
    et al.
    Department of Materials Science and Engineering, Royal Institute of Technology.
    El-Geassy, Abdel Hady
    Central Metallurgical Research and Development Institute (CMRDI), Helwan, Cairo.
    Seetharaman, Seshadri
    Kungliga tekniska högskolan, KTH.
    Kinetics of Reduction of NiO–WO3 Mixtures by Hydrogen2010In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 41, no 1, p. 161-172Article in journal (Refereed)
    Abstract [en]

    The kinetics of reduction of the oxide mixtures of Ni-W with different Ni/(Ni-W) molar ratios within the range of 923 K to 1173 K in flowing hydrogen gas was investigated by means of thermogravimetric analysis under isothermal conditions. The products were examined by X-ray diffraction, scanning electron microscope (SEM), and electron dispersion spectroscopy (EDS) analyses. Five different oxide mixtures apart from the pure oxides were studied in the present work. The results indicate that the reduction reaction proceeds through three consecutive steps that are as follows:NiO-WO3→Ni-WO3→Ni-WO2→Ni-WFrom the experimental results, the Arrhenius activation energies of the three steps were evaluated for all of the studied compositions. The activation energy for the first step was calculated to be approximately 18 kJ/mol. For the second and third stages, the activation energy values varied from 62 to 38 kJ/mol for the second stage and 51 to 34 kJ/mol for the third stage depending on the Ni/(Ni + W) molar ratio in the precursors; the activation energy increased with increasing ratios. SEM images showed that the grain size of the final product was dependent on the Ni/(Ni + W) molar ratio; smaller grains were formed at higher nickel contents.

  • 4.
    Ahmed, Hesham M.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    El-Geassy, A. H. A.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Kinetics of Reduction of NiO-WO3 Mixtures by Hydrogen2010In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 41, no 1, p. 161-172Article in journal (Refereed)
    Abstract [en]

    The kinetics of reduction of the oxide mixtures of Ni-W with different Ni/(Ni-W) molar ratios within the range of 923 K to 1173 K in flowing hydrogen gas was investigated by means of thermogravimetric analysis under isothermal conditions. The products were examined by X-ray diffraction, scanning electron microscope (SEM), and electron dispersion spectroscopy (EDS) analyses. Five different oxide mixtures apart from the pure oxides were studied in the present work. The results indicate that the reduction reaction proceeds through three consecutive steps that are as follows: NiO-WO3 -> Ni-WO3 -> Ni-WO2 -> Ni-W From the experimental results, the Arrhenius activation energies of the three steps were evaluated for all of the studied compositions. The activation energy for the first step was calculated to be approximately 18 kJ/mol. For the second and third stages, the activation energy values varied from 62 to 38 kJ/mol for the second stage and 51 to 34 kJ/mol for the third stage depending on the Ni/(Ni + W) molar ratio in the precursors; the activation energy increased with increasing ratios. SEM images showed that the grain size of the final product was dependent on the Ni/(Ni + W) molar ratio; smaller grains were formed at higher nickel contents.

  • 5.
    Ahmed, Hesham M.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    El-Geassy, Abdel-Hady
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Kinetic Studies of the Hydrogen Reduction of NiO-WO3 precursors in a Fluidized-bed reactorIn: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916Article in journal (Other academic)
  • 6.
    Ahmed, Hesham M.
    et al.
    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.
    Reduction-Carburization of NiO-WO3 Under Isothermal Conditions Using H2-CH4 Gas Mixture2010In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 41, no 1, p. 173-181Article in journal (Refereed)
    Abstract [en]

    Ni-W-C ternary carbides were synthesized by simultaneous reduction–carburization of NiO-WO3 oxide precursors using H2-CH4 gas mixtures in the temperature range of 973 to 1273 K. The kinetics of the gas–solid reaction were followed closely by monitoring the mass changes using the thermogravimetric method (TGA). As a thin bed of the precursors were used, each particle was in direct contact with the gas mixture. The results showed that the hydrogen reduction of the oxide mixture was complete before the carburization took place. The nascent particles of the metals formed by reduction could react with the gas mixture with well-defined carbon potential to form a uniform product of Ni-W-C. Consequently, the reaction rate could be conceived as being controlled by the chemical reaction. From the reaction rate, Arrhenius activation energies for reduction and carburization were evaluated. Characterization of the carbides produced was carried out using X-ray diffraction and a scanning electron microscope (SEM) combined with electron dispersion spectroscopy (SEM-EDS) analyses. The grain sizes also were determined. The process parameters, such as the temperature of the reduction–carburization reaction and the composition of the gas mixture, had a strong impact on the carbide composition as well as on the grain size. The results are discussed in light of the reduction kinetics of the oxides and the thermodynamic constraints.

  • 7.
    Ahmed, Hesham
    et al.
    Department of Materials Science and Engineering, Royal Institute of Technology.
    Seetharaman, Seshadri
    Kungliga tekniska högskolan, KTH.
    Reduction-Carburization of NiO-WO3 Under Isothermal Conditions Using H2-CH4 Gas Mixture2010In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 41, no 1, p. 173-181Article in journal (Refereed)
    Abstract [en]

    Ni-W-C ternary carbides were synthesized by simultaneous reduction–carburization of NiO-WO3 oxide precursors using H2-CH4 gas mixtures in the temperature range of 973 to 1273 K. The kinetics of the gas–solid reaction were followed closely by monitoring the mass changes using the thermogravimetric method (TGA). As a thin bed of the precursors were used, each particle was in direct contact with the gas mixture. The results showed that the hydrogen reduction of the oxide mixture was complete before the carburization took place. The nascent particles of the metals formed by reduction could react with the gas mixture with well-defined carbon potential to form a uniform product of Ni-W-C. Consequently, the reaction rate could be conceived as being controlled by the chemical reaction. From the reaction rate, Arrhenius activation energies for reduction and carburization were evaluated. Characterization of the carbides produced was carried out using X-ray diffraction and a scanning electron microscope (SEM) combined with electron dispersion spectroscopy (SEM-EDS) analyses. The grain sizes also were determined. The process parameters, such as the temperature of the reduction–carburization reaction and the composition of the gas mixture, had a strong impact on the carbide composition as well as on the grain size. The results are discussed in light of the reduction kinetics of the oxides and the thermodynamic constraints.

  • 8.
    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.

  • 9.
    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.

  • 10.
    Albertsson, Galina Jelkina
    et al.
    Division of Materials Process Science, Royal Institute of Technology (KTH).
    Teng, Lidong
    Division of Materials Process Science, Royal Institute of Technology (KTH).
    Engström, Fredrik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Seetharaman, Seshadri
    Division of Materials Process Science, Royal Institute of Technology (KTH).
    Effect of the heat treatment on the chromium partition in CaO-MgO-SiO2-Cr2O3 synthetic slags2013In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 44, no 6, p. 1586-1597Article in journal (Refereed)
    Abstract [en]

    Mg-spinel phase is known to be important for control of Cr leaching from Cr-containing slags. The objective of the present study is to get an understanding of the phase relationships in the CaO-MgO-SiO2-Cr2O3 system with a view to control the precipitation of Cr-spinel in the slag phase. The equilibrium phases in CaO-MgO-SiO2-Cr2O3 slag system in the range of 1673 K to 1873 K (1400 °C to 1600 °C) have been investigated experimentally and compared with the results from thermodynamic calculations. The slag compositions close to the industrial slag systems were chosen. The Cr2O3 and MgO contents in the slag were fixed to be 6 and 8 wt pct, respectively. The basicity (CaO/SiO2) of the slag was varied in the range of 1.0 to 2.0. The slags were synthesized at a pre-determined oxygen partial pressure (10-4) or air (2.13 × 104 Pa) at a temperature above the liquidus temperature. The samples were then soaked at targeted temperatures for 24 hours in controlled atmosphere in order to achieve the equilibrium state before quenching in water. Four different heat-treatment regimes (defined as Ia, Ib, II.a and II.b) in Section II-D) were used in the present experiments. The lower oxygen partial pressure was maintained by a suitable mixture of CO and CO2 gases. Phases present and their compositions in the quenched slags were studied using scanning electron microscopy coupled with energy-dispersive spectroscopy and X-ray diffraction techniques. The chromium content in the phases present was analyzed using wavelength-dispersive spectrometer. The experimental results obtained are compared with the calculation results from Factsage software. The size of spinel crystals increased drastically after slow-cooling from 1873 K (1600 °C) followed by annealing at 1673 K (1400 °C) for 24 hours (heating regimes II) compared to samples being quenched directly after soaking at 1873 K (1600 °C) (heating regime I.a). It was found that the amount of foreign elements in the spinel phase, and other phases decreased after soaking at oxygen partial pressure of 10-4 Pa resulting in phases with less defects and foreign oxide contents compared to those treated in air. The size of spinel crystals was found to be larger in samples with lower basicity

  • 11.
    Allertz, Carl
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Selleby, Malin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Sichen, Du
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    The Effect of Oxygen Potential on the Sulfide Capacity for Slags Containing Multivalent Species2016In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 47, no 5, p. 3039-3045Article in journal (Refereed)
    Abstract [en]

    The dependence of sulfide capacity on the oxygen partial pressure for slags containing multivalent species was investigated experimentally using a slag containing vanadium oxide. Copper-slag equilibration experiments were carried out at 1873 K (1600 A degrees C) in the approximate oxygen partial pressure range 10(-15.4) to 10(-9) atm. The sulfide capacity was found to be strongly dependent on the oxygen potential in this slag system, increasing with the oxygen partial pressure. The sulfide capacity changed by more than two orders of magnitude over the oxygen partial pressure range. The effect of changing oxygen partial pressure was found to be much greater than the effect of changing slag composition at a fixed oxygen partial pressure.

  • 12.
    Allertz, Carl
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Sichen, Du
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Sulfide Capacity in Ladle Slag at Steelmaking Temperatures2015In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 46, no 6, p. 2609-2615Article in journal (Refereed)
    Abstract [en]

    Sulfide capacity measurements were conducted at 1823 K and 1873 K (1550 degrees C and 1600 degrees C) for the quaternary Al2O3-CaO-MgO-SiO2 system, for typical compositions used in the ladle in steelmaking. A copper-slag equilibrium was used under controlled oxygen and sulfur potentials. The sulfide capacity is strongly dependent on the composition and it was found to increase with the basic oxides, while it decreases with increase of the acidic components. It was found that CaO is more effective in holding sulfur in the slag compared to MgO when replacing SiO2. For the present slag compositions, Al2O3 and SiO2 behaved similar with respect to sulfur, and no considerable effect could be recorded when replacing one for the other. The sulfide capacity was also found to be strongly dependent on the temperature, increasing with temperature. The present results were compared with industrial data from the ladle, after vacuum treatment, and they were in good agreement.

  • 13. Antonsson, T.
    et al.
    Fredriksson, Hasse
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Processing.
    The effect of cooling rate on the solidification of INCONEL 7182005In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 36, no 1, p. 85-96Article in journal (Refereed)
    Abstract [en]

    The superalloy INCONEL 718 (IN718) is a commonly used material in aerospace and turbine components. The advantage of this type of material with sluggish precipitation-hardening kinetics is that IN718 is readily weldable. Both wrought and cast parts are used and welded together. While the alloy has been studied previously, new production processes such as laser treatment demand better knowledge of the solidification process in IN718. especially at high cooling rates. In this investigation. the solidification process was studied over a wide range of cooling rated by three different experimental techniques: differential thermal analysis (DTA), mirror furnace (MF), and levitation casting. The solidification sequence and the reaction temperatures were identified. The microstructure and the change in growth morphology were also studied. Segregation measurements were performed, and the distribution of Nb was analyzed in detail for the different types of samples. because of its strong impact on the solidification sequence and microstructure. New observations are that the latent heat decreases and the effective partition coefficient increases with increasing cooling rate. The diffusion rate also seems to be enhanced in the first part of primary solidified dendrites. It is suggested that the new observations can be explained by an increased number of lattice defects formed in the solid as the cooling rate increases.

  • 14.
    Bagherpour-Torghabeh, Hamed
    et al.
    Shahid Bahonar Univ Kerman, Sch Engn, Dept Met & Mat Sci, JomhooriEslami Blvd, Kerman, Iran..
    Raiszadeh, Ramin
    Shahid Bahonar Univ Kerman, Sch Engn, Dept Met & Mat Sci, JomhooriEslami Blvd, Kerman, Iran..
    Doostmohammadi, Hamid
    Shahid Bahonar Univ Kerman, Sch Engn, Dept Met & Mat Sci, JomhooriEslami Blvd, Kerman, Iran..
    Removal of Bifilms from Al Melts by Stirring in Unbaffled and Baffled Crucibles2018In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 49, no 6, p. 3456-3469Article in journal (Refereed)
    Abstract [en]

    The free surface of aluminum melt, during stirring under different rotation speeds in unbaffled and baffled crucibles, was simulated numerically using a RANS turbulence model coupled with a particle-tracking method. The effect of mechanical stirring of Al melts containing 0.3, 0.7, and 4.5 wt pct Mg in unbaffled and baffled crucibles on the rate of elimination of bifilms from the melt was also investigated using a reduced pressure test. The results showed that the stirring increased the rate of removal of bifilms from the melt due to an increase in the rate of formation of cracks on the bifilms. Using baffles in the crucible accelerated the rate of removal of bifilms by changing the pattern of movement of bifilms in the melt. The critical stirring speeds, above which the oxide layer on the Al melt could submerge into the bulk liquid, were determined by the simulation. It was confirmed by the experimental results to be about 158 and 420 RPM for the unbaffled and baffled crucibles, respectively.

  • 15.
    Bagherpour-Torghabeh, Hamed
    et al.
    Shahid Bahonar Univ Kerman, Dept Met & Mat Sci, Jomhoori Eslami Blvd, Kerman 7616914111, Iran.;Shahid Bahonar Univ Kerman, Mineral Ind Res Ctr, Jomhoori Eslami Blvd, Kerman 7616914111, Iran..
    Raiszadeh, Ramin
    Shahid Bahonar Univ Kerman, Dept Met & Mat Sci, Jomhoori Eslami Blvd, Kerman 7616914111, Iran.;Shahid Bahonar Univ Kerman, Mineral Ind Res Ctr, Jomhoori Eslami Blvd, Kerman 7616914111, Iran.;Shahid Bahonar Univ Kerman, Sch Engn, Dept Met & Mat Sci, Jomhoori Eslami Blvd, Kerman, Iran..
    Doostmohammadi, Hamid
    Shahid Bahonar Univ Kerman, Dept Met & Mat Sci, Jomhoori Eslami Blvd, Kerman 7616914111, Iran.;Shahid Bahonar Univ Kerman, Mineral Ind Res Ctr, Jomhoori Eslami Blvd, Kerman 7616914111, Iran..
    Role of Mechanical Stirring of Al-Mg Melt in the Healing of Bifilm Defect2017In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 48, no 6, p. 3174-3184Article in journal (Refereed)
    Abstract [en]

    The effect of mechanical stirring of aluminum melts containing 0.3, 0.7, and 4.5 wt pct Mg with a graphite rotor with different rotation speeds of 85 and 220 RPM on the behavior of bifilms was investigated using a reduced pressure test. The results showed that the mechanical stirring at 85 RPM accelerated the healing of the bifilms by increasing the rate of formation of cracks on the bifilms and hence accelerated the consumption of their atmosphere and provided enough Mg for the transformation of the alumina layers of the bifilms to spinel. Mechanical stirring with a high speed of 220 RPM caused aspiration of the surface oxide into the melt to form new bifilms which counteracted the healing of the previously presented bifilms.

  • 16.
    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.

  • 17. Basu, S.
    et al.
    Lahiri, A. K.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Activity of Ferric Oxide in Steelmaking Slag2010In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 41, no 2, p. 414-419Article in journal (Refereed)
    Abstract [en]

    Refining reactions in steelmaking primarily involve oxidation of impurity element(s). The oxidation potential of the slag and the activity of oxygen in the metal (h(O)) are the major factors controlling these chemical reactions. In turn, the oxidation potential of the slag is influenced strongly by the equilibrium distribution of oxygen between ferrous and ferric oxides. We recently investigated the activity coefficient of FeO in steelmaking slag and the effect of chemical composition thereon. This work is focused on estimation of the activity coefficient of Fe2O3.

  • 18. Basu, S.
    et al.
    Lahiri, A. K.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Activity of iron oxide in steelmaking slag2008In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 39, no 3, p. 447-456Article in journal (Refereed)
    Abstract [en]

    Most refining reactions in steelmaking involve oxidation of impurity element(s). The product(s) of oxidation either dissolve in the slag or escape as gaseous phase. The activities of oxygen in the metal (h (O)), and that of "FeO" in slag (a (FeO)), are major factors controlling these chemical reactions. The activities of oxygen and "FeO" are thermodynamically related, provided equilibrium distribution of oxygen between the slag and the metal is attained. This enables direct estimation of one parameter from the other. A thorough knowledge of the variation in activity of FeO, and factors affecting the same, is therefore of great importance in the process metallurgy of steelmaking. The present work experimentally measures the activity of FeO in steelmaking slags and attempts to develop a correlation for estimation of gamma(FeO) as a function of temperature and chemical composition of the slag.

  • 19.
    Basu, Somnath
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Lahiri, Ashok Kumar
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Phosphorus partition between liquid steel and CaO-SiO2-FeOx-P2O5-MgO slag containing 15-25 %FeO2007In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 38, no 4, p. 623-630Article in journal (Refereed)
    Abstract [en]

    CaO-SiO2-FeO2-P2O5-MgO bearing slags are typically used in the basic oxygen steelmaking (BOS) process. The partition ratio of phosphorus between slag and steel is an index of the phosphorus holding capacity of the slag, which determines the phosphorus content achievable in the finished steel. The influence of factors such as FeO content and basicity on the phosphorus partition ratio was investigated at two different temperatures. The partition ratio initially increased with basicity but remained constant beyond a basicity of 2.5 to 2.6. An increase in the FeO content up to 18 to 20 mass pct was beneficial for the phosphorus partition at a basicity level of 2 to 3, but a higher concentration of FeO resulted in a decrease in the phosphorus partition ratio; the FeO concentration corresponding to this transition varied with basicity and temperature. At even lower basicities, however, the equilibrium phosphorus partition showed either no change, or a marginally decreasing trend, with an increase in the FeO content.

  • 20.
    Basu, Somnath
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Lahiri, Ashok Kumar
    KTH.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Phosphorus partition between liquid steel and CaO-SiO2-P2O5-MgO slag containing low FeO2007In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 38, no 3, p. 357-366Article in journal (Refereed)
    Abstract [en]

    CaO-SiO2-FeOx-P2O5-MgO bearing slags are typical in the basic oxygen steelmaking (BOS) process. The partition ratio of phosphorus between slag and steel is an index of the phosphorus holding capacity of the slag, which determines the phosphorus content achievable in the finished steel. The influences of FeO concentration and basicity on the equilibrium phosphorus partition ratios were experimentally determined at temperatures of 1873 and 1923 K, for conditions of MgO saturation. The partition ratio initially increased with basicity but attained a constant value beyond basicity of 2.5. An increase in FeO concentration up to approximately 13 to 14 mass pet was beneficial for phosphorus partition.

  • 21.
    Bellét, M
    et al.
    Jönköping University, School of Engineering, JTH. Research area Materials and Manufacturing - Casting.
    Bay, F
    Chenot, J
    Decultieux, F
    Menai, M
    Levaillant, C
    Schmidt, P
    Svensson, Ingvar L
    Jönköping University, School of Engineering, JTH. Research area Materials and Manufacturing - Casting. Jönköping University, School of Engineering, JTH, Mechanical Engineering.
    Thermomechanics of the cooling stage in casting processes: three-dimensional finite element analysis and experimental validation1996In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 27, no 1, p. 81-99Article in journal (Refereed)
  • 22.
    Berg, Martin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Lee, Jaewoo
    Hyundai Steel, 1480 Bukbusaneop Ro, Dangjin Si 31719, Chungnam, South Korea..
    Sichen, Du
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Partitioning of Calcium Between Liquid Silver and Liquid Iron2018In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 49, no 3, p. 949-952Article in journal (Refereed)
    Abstract [en]

    The partitioning of calcium between liquid silver and liquid iron at 1823 K and 1873 K (1550 degrees C and 1600 degrees C) was studied experimentally using a closed molybdenum container. The calcium potential in the container was controlled by the composition of the alloys in equilibrium. The results agreed well with previous experimental measurements and indicated that the effect of temperature was not very pronounced in the temperature range studied.

  • 23.
    Berg, Martin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Lee, Jaewoo
    Sichen, Du
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling. KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy. KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Study on the Equilibrium Between Liquid Iron and Calcium Vapor2017In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 48, no 3, p. 1715-1720Article in journal (Refereed)
    Abstract [en]

    The solubility of calcium in liquid iron at 1823 K and 1873 K (1550 A degrees C and 1600 A degrees C) as a function of calcium potential was studied experimentally. The measurements were performed using a closed molybdenum holder in which liquid calcium and liquid iron were held at different temperatures. The results indicate a linear relationship between the activity of calcium, relative to pure liquid calcium, and the mole fraction of dissolved calcium in liquid iron, with a negligible temperature dependency in the ranges studied. The activity coefficient of calcium in liquid iron at infinite dilution, was calculated as 1551.

  • 24.
    Beskow, Kristina
    et al.
    Department of Materials Science and Engineering, Division of Metallurgy, Royal Institute of Technology.
    Nurni, Viswanathan
    Jonsson, Lage T.I.
    Department of Materials Science and Engineering, Division of Metallurgy, Royal Institute of Technology.
    Sichen, Du U.
    Department of Materials Science and Engineering, Division of Metallurgy, Royal Institute of Technology.
    Study of the deoxidation of steel with aluminum wire injection in a gas-stirred ladle2001In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 32, no 2, p. 319-328Article in journal (Refereed)
    Abstract [en]

    In the present work, the deoxidation of liquid steel with aluminum wire injection in a gas-stirred ladle was studied by mathematical modeling using a computational fluid dynamics (CFD) approach. This was complemented by an industrial trial study conducted at Uddeholm Tooling AB (Hagfors, Sweden). The results of the industrial trials were found to be in accordance with the results of the model calculation. In order to study the aspect of nucleation of alumina, emphasis was given to the initial period of deoxidation, when aluminum wire was injected into the bath. The concentration distributions of aluminum and oxygen were calculated both by considering and not considering the chemical reaction. Both calculations revealed that the driving force for the nucleation of Al2O3 was very high in the region near the upper surface of the bath and close to the wire injection. The estimated nucleation rate in the vicinity of the aluminum wire injection point was much higher than the recommended value for spontaneously homogeneous nucleation, 103 nuclei/(cm3/s). The results of the model calculation also showed that the alumina nuclei generated at the vicinity of the wire injection point are transported to other regions by the flow.

  • 25.
    Beskow, Kristina
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Viswanathan, N. N.
    Jonsson, Lage
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Sichen, Du
    KTH, Superseded Departments, Materials Science and Engineering.
    Study of the deoxidation of steel with aluminum wire injection in a gas-stirred ladle2001In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 32, no 2, p. 319-328Article in journal (Refereed)
    Abstract [en]

    In the present work, the deoxidation of liquid steel with aluminum wire injection in a gas-stirred ladle was studied by mathematical modeling using a computational fluid dynamics (CFD) approach. This was complemented by an industrial trial study conducted at Uddeholm Tooling AB (Hagfors, Sweden). The results of the industrial trials were found to be in accordance with the results of the model calculation. In order to study the aspect of nucleation of alumina, emphasis was given to the initial period of deoxidation, when aluminum wire was injected into the bath. The concentration distributions of aluminum and oxygen were calculated both by considering and not considering the chemical reaction. Both calculations revealed that the driving force for the nucleation of Al2O3 was very high in the region near the upper surface of the bath and close to the wire injection. The estimated nucleation rate in the vicinity of the aluminum wire injection point was much higher than the recommended value for spontaneously homogeneous nucleation, 10(3) nuclei/(cm(3)/s). The results of the model calculation also showed that the alumina nuclei generated at the vicinity of the wire injection point are transported to other regions by the flow.

  • 26.
    Brandberg, Jenny
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Sichen, Du
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Water vapor solubility in ladle-refining slags2006In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 37, no 3, p. 389-393Article in journal (Refereed)
    Abstract [en]

    A thermo-gravimetric technique was used to determine the hydrogen solubilities of some Al2O3-CaO-MgO-SiO2 quaternary slags. The focus of the work was to determine the water capacities in slags having lower SiO2 concentrations, which were relevant to industrial practices. The majority of the experiments were carried out in the temperature interval 1747 to 1827 K with water pressure of 157 mbar. The reliability of the experiments was confirmed using a quenching technique. The temperature was found to have a negligible effect on the water solubilities. The composition of the slag did not seem to significantly affect the water capacity. However, as the slag composition approached CaO saturation, a considerable increase of the solubility was noticed.

  • 27.
    Bustnes, J.A.
    et al.
    LKAB, Research & Development, 983 81 Malmberget.
    Nurni, Viswanathan
    Sichen, Du U.
    LKAB, Research & Development, 983 81 Malmberget.
    Seetharaman, Seshadri
    Division of Metallurgy, Department of Materials Science and Technology, Royal Institute of Technology.
    Investigation on reduction of CoAI2O4 by hydrogen gas using TGA2000In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 31, no 3, p. 540-542Article in journal (Refereed)
  • 28.
    Cao, Weimin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Muhmood, Luckman
    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.
    Sulfur Transfer at Slag/Metal Interface-Impact of Oxygen Potential2012In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 43, no 2, p. 363-369Article in journal (Refereed)
    Abstract [en]

    In the present work, the interfacial movement resulting from sulfur mass transfer at the slag/metal interface was monitored by X-ray sessile drop method in dynamic mode at temperature 1873 K (1600 A degrees C) under nonequilibrium conditions. The experiments were carried out with pure iron and CaO-SiO2-Al2O3-FeO slag (alumina saturated at the experimental temperature) contained in alumina crucibles with well-controlled partial pressures of oxygen and sulfur. The impact of oxygen potential on the droplet oscillation as sulfur from the gas phase reaches the metal drop through the intermediate slag phase was monitored. The interfacial velocity was investigated. It was found that the increases of interfacial velocity and the maximum oscillation time were mainly attributed to the partial pressure of oxygen increases. The experiment results were explained by previous ab initio calculations. The thermo-physical and thermo-chemical properties of slag were also found to influence interfacial velocity.

  • 29.
    Carlberg, Torbjorn
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Jarfors, Anders E. W.
    School of Engineering, Jönköping University, 55111 Jönköping, Sweden .
    On Vertical Drag Defects Formation During Direct Chill (DC) Casting of Aluminum Billets2014In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 45, no 1, p. 175-181Article in journal (Refereed)
    Abstract [en]

    During air-slip direct chill casting of aluminum billets, one of the major defects occurring includes traces along the billet called vertical drags (VDs). If the VDs are too deep or too many, then they cause scraping of the billets. As in the subsequent extrusion process, the surface quality is known to impair both the productivity and quality of the profiles. In cast-house practice, many theories circulate about the causes of VD defects and how to avoid them, but in the literature, no thorough treatments have been made to explain this phenomenon. In the current study, the outer appearance, structure around, and compositions at the defects are analyzed. A theory for the formation of the defects, their cause, and how their appearance is coupled to different alloy types is presented. The segregation in the vicinity of the defects is discussed based on deformation of semisolid materials and coupled to Reynolds dilatancy in granular materials. The theory can explain differences between 6063 and 6005 alloys.

  • 30.
    Carlberg, Torbjörn
    et al.
    Mid Sweden University, Sundsvall, Sweden.
    Jarfors, Anders
    Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    On vertical drag defects formation during direct chill (DC) casting of aluminum billets2014In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 45, no 1, p. 175-181Article in journal (Refereed)
    Abstract [en]

    During air-slip direct chill casting of aluminum billets, one of the major defects occurring includes traces along the billet called vertical drags (VDs). If the VDs are too deep or too many, then they cause scraping of the billets. As in the subsequent extrusion process, the surface quality is known to impair both the productivity and quality of the profiles. In cast-house practice, many theories circulate about the causes of VD defects and how to avoid them, but in the literature, no thorough treatments have been made to explain this phenomenon. In the current study, the outer appearance, structure around, and compositions at the defects are analyzed. A theory for the formation of the defects, their cause, and how their appearance is coupled to different alloy types is presented. The segregation in the vicinity of the defects is discussed based on deformation of semisolid materials and coupled to Reynolds dilatancy ingranular materials. The theory can explain differences between 6063 and 6005 alloys.

  • 31.
    Casas, Jesús M.
    et al.
    Dept of Mining Engineering, University of Chile, Santiago, Chile.
    Vargas, T.
    Dept of Chemical Engineering, University of Chile, Santiago, Chile.
    Martínez, Joaquín
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena.
    Moreno, Luis
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Engineering.
    Bioleaching model of a copper-sulfide ore bed in heap and dump configurations1998In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 29, no 4, p. 899-909Article in journal (Refereed)
    Abstract [en]

    A two-dimensional (2-D) model for a heap or dump bioleaching of a copper ore containing mainly chalcocite and pyrite has been developed. The rate of the mineral sulfide dissolution was related to the rate of oxidation by bacteria attached onto the ore surface. The latter was calculated using the model of Michaelis-Menten, where both temperature and dissolved oxygen in the leach solution were taken into account by the kinetic equation. Oxygen transport through the ore bed was associated with natural air convection originating from the decrease in gas density inside the ore bed, which was attributable not only to heating, but also to humidification and decrease in the oxygen concentration. The model was used to estimate air-velocity fields and profiles of temperature and oxygen concentrations as well as mineral conversions during the bioleaching operation for ore beds with different pyrite contents, bacterial populations, widths, heights, and permeabilities. The model provides a useful tool for the design, improvement, and optimization of industrial operating conditions.

  • 32.
    Chen, Chao
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy. State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, China .
    Jonsson, Lage
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy. Swedish Def Res Agcy, FOI, Div CBRN Def & Secur, Sweden.
    Tilliander, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Cheng, Guoguang
    State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    A Mathematical Modeling Study of Tracer Mixing in a Continuous Casting Tundish2015In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 46, no 1, p. 169-190Article in journal (Refereed)
    Abstract [en]

    A mathematical model based on a water model was developed to study the tracer mixing in a single strand tundish. The mixing behavior of black ink and KCl solution was simulated by a mixed composition fluid model, and the data were validated by water modeling results. In addition, a model that solves the scalar transport equation (STE) without any physical properties of the tracer was studied and the results were compared to predictions using the density-coupled model. Furthermore, the mixing behaviors of different amounts of KCl tracers were investigated. Before the model was established, KCl tracer properties such as the KCl molecule diffusion (KMD), the water molecule self-diffusion (WSD) in KCl solution, and the KCl solution viscosity (KV) were evaluated. The RTD curve of 250 mL KCl for the KMD case was closer to the water modeling results than that of the case implemented with only density. Moreover, the ensemble average deviation of the RTD curves of the cases implemented with KMD+ WSD, KMD+ KV, and KMD+ WSD+ KV to the KMD case is less than 0.7 pct. Thus, the water self-diffusion and KV were neglected, while the KCl density and KMD were implemented in the current study. The flow pattern of black ink was similar to the STE result i. e., the fluid flowed upwards toward the top surface and formed a large circulating flow at the outlet nozzle. The flow behavior of the 100, 150, and 250 mL KCl cases exhibited a strong tendency to sink to the tundish bottom, and subsequently flow through the holes in the dam. Thereafter, it propagated toward the outlet nozzle. Regarding the KCl tracer amount, the tracer concentration propagated to the outlet nozzle much faster for the larger amount case than for the smaller amount cases. However, the flow pattern for the 50 mL KCl case was somewhat different. The fluid propagated to the top surface which acted like black ink during the initial injection, and subsequently the fluid flowed throughout the holes at a much slower pace. The breakthrough time and peak concentration of RTD curves of model predictions and water modeling results showed a good agreement (all difference within 12.5 pct) for the 100, 150, and 250 mL KCl cases.

  • 33.
    Chen, Chao
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Taiyuan University of Technology, China; University of Science and Technology Beijing, China.
    Ni, Peiyuan
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Jonsson, L. T. I.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Swedish Defence Research Agency, Sweden.
    Tilliander, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Cheng, G.
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    A Model Study of Inclusions Deposition, Macroscopic Transport, and Dynamic Removal at Steel–Slag Interface for Different Tundish Designs2016In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 47, no 3, p. 1916-1932Article in journal (Refereed)
    Abstract [en]

    This paper presents computational fluid dynamics (CFD) simulation results of inclusions macroscopic transport as well as dynamic removal in tundishes. A novel treatment was implemented using the deposition velocity calculated by a revised unified Eulerian deposition model to replace the widely used Stokes rising velocity in the boundary conditions for inclusions removal at the steel–slag interface in tundishes. In this study, the dynamic removal for different size groups of inclusions at different steel–slag interfaces (smooth or rough) with different absorption conditions at the interface (partially or fully absorbed) in two tundish designs was studied. The results showed that the dynamic removal ratios were higher for larger inclusions than for smaller inclusions. Besides, the dynamic removal ratio was higher for rough interfaces than for smooth interfaces. On the other hand, regarding the cases when inclusions are partially or fully absorbed at a smooth steel–slag interface, the removal ratio values are proportional to the absorption proportion of inclusions at the steel–slag interface. Furthermore, the removal of inclusions in two tundish designs, i.e., with and without a weir and a dam were compared. Specifically, the tundish with a weir and a dam exhibited a better performance with respect to the removal of bigger inclusions (radii of 5, 7, and 9 μm) than that of the case without weir and dam. That was found to be due to the strong paralleling flow near the middle part of the top surface. However, the tundish without weir and dam showed a higher removal ratio of smaller inclusions (radius of 1 μm). The reason could be the presence of a paralleling flow near the inlet zone, where the inclusions deposition velocities were much higher than in other parts.

  • 34.
    Chychko, Andrei
    et al.
    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.
    Foaming in Electric Arc Furnace: Part I: Laboratory Studies of Enthalpy changes of Carbonate Additions to Slag Melts2011In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 42, no 1, p. 20-29Article in journal (Refereed)
    Abstract [en]

    In the present work, a modified thermal analysis technique was used for studying the heat effect of slag foaming with carbonates addition. Experiments were conducted by sinking limestone and dolomite pieces of defined shapes (together with iron sinkers) in molten slag and monitoring the temperature changes accompanying the decomposition of carbonates. The heat effects of dolomite and limestone decompositions were determined at 1623 K (1350 A degrees C) and 1673 K (1400 A degrees C). It was found that the decomposition energy for dolomite and limestone for the studied slag composition is in the range of 56 to 79 pct of theoretical values, which is linked to the energy-saving effect of slag foaming. No influence of sample shape on decomposition energy was found for both limestone and dolomite.

  • 35.
    Chychko, Andrei
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Teng, Lidong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Seetharaman, Seshadri
    Foaming in Electric Arc Furnace: Part II: Foaming visualization and Comparison with Plant trials2012In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 43, no 5, p. 1078-1085Article in journal (Refereed)
    Abstract [en]

    The kinetics of slag foaming by limestone particles was studied at 1773 K (1500 A degrees C) with the aid of an X-ray imaging system. Two models were implemented to describe the decrease in foam height with the time on the basis of the lowering of the average temperature and CaO shell formation during decomposition reaction. The energy impact of carbonate additions was studied on an industrial scale in a 100-ton electric arc furnace (EAF). It was found that, in the case of the addition of carbonates after the scrap is completely molten, the heat effects for limestone and dolomite (2255 and 2264 kJ/kg, respectively) were only 70 pct from theoretical values. Comparing these values with similar additions during the scrap melting stage shows that the energy requirements in the case of carbonate additions to steel bath are much smaller. It was found from the trial heats with dolomite addition to the steel bath that the partial substitution of lime by raw dolomite can be made without an increase in energy consumption.

  • 36.
    Deng, Tengfei
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Du, Sichen
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Study of Lime Dissolution Under Forced Convection2012In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 43, no 3, p. 578-586Article in journal (Refereed)
    Abstract [en]

    Dissolution of different CaO cubes under force convection in liquid CaO-"FeO"-SiO2 slag was studied at 1873 K (1600 A degrees C). A linear relationship between normalized lengths and time was obtained after the experiment. It was evidently observed that the removal of the interface layer(s) including 2CaO center dot SiO2 by shear stress was the main mechanism for the dissolution. A stirring rate of approximately 100 rpm was found to be efficient to remove the interface layer(s). The limes with different structures had different dissolution rates.

  • 37.
    Deng, Tengfei
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Nortier, Patrice
    Ek, Mattias
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Du, Sichen
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Limestone Dissolution in Converter Slag at 1873 K (1600 degrees C)2013In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 44, no 1, p. 98-105Article in journal (Refereed)
    Abstract [en]

    Decomposition and dissolution of limestone in slag at 1873 K (1600 A degrees C) were studied. The limestone samples were in the shape of cubes (11 mm x 11 mm x 11 mm approximately). The decomposition was carried out both in argon and in slag under argon atmosphere. In order to gain an insight into the phenomenon of slow decomposition, the decomposition process of CaCO3 was simulated using Comsol. The results showed evidently that the decomposition of calcium carbonate was controlled mostly by heat transfer. It was also found that the decomposition product CaO had very dense structure, whether the sample was decomposed in slag or in argon. The slow decomposition and the dense CaO layer would greatly hinder the dissolution of lime in the slag. The present results clearly indicate that the addition of limestone instead of lime would not be beneficial in the converter process.

  • 38.
    Deng, Zhiyin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Northeastern University, China.
    Zhu, M.
    Zhou, Y.
    Sichen, Du
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Attachment of Alumina on the Wall of Submerged Entry Nozzle During Continuous Casting of Al-Killed Steel2016In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 47, no 3, p. 2015-2025Article in journal (Refereed)
    Abstract [en]

    The mechanisms of the formation of different attachments on the walls of submerged entry nozzle (SEN) were studied for the processes of Al-killed steel (Ca-treated, HSLA) and ultra-low carbon Al-killed steel (ULC). To understand the mechanism, the types of inclusions in the steel taken in tundish and in bloom (or slab) were identified. In the case of ULC, the reoxidation product, micro-alumina particles were found to be the source of attachment on the inner wall of the SEN. To avoid reoxidation of the steel by the top slag, removal of the slag could be considered in order to improve the situation. No attached layer was found on the outer surface of the SEN after casting of the ULC steel. In the case of HSLA steel, an attached layer composed of plate-like alumina crystals was found in some trials. The entrainment of oxygen through the mold powder due to improper operation would be the reason for the formation of this type of attachment. The formation of the plate-like crystals was discussed with the help of CFD calculation.

  • 39.
    Deng, Zhiyin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling. School of Metallurgy, Northeastern Unviersity, China.
    Zhu, Miaoyong
    School of Metallurgy, Northeastern Unviersity, China.
    Du, Sichen
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Effect of Refractory on Nonmetallic Inclusions in Al-killed Steel2016In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 47, no 5, p. 3158-3167Article in journal (Refereed)
  • 40.
    Domeij, Björn
    et al.
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Hernando, Juan Carlos
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Diószegi, Attila
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing.
    Size distribution of graphite nodules in hypereutectic cast irons of varying nodularity2018In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 49, no 5, p. 2487-2504Article in journal (Refereed)
    Abstract [en]

    An SGI was machined into 400 g cylindrical pieces and remelted in an electrical resistance furnace protected by Ar gas to produce materials ranging from SGI to CGI. The graphite morphology was controlled by varying the holding time at 1723 K (1450 °C) between 10 and 60 minutes. The discrete sectional size distribution of nodules by number density was measured on cross sections of the specimens and translated to volumetric distribution by volume fraction. Subpopulations of nodules were distinguished by fitting Gaussian distribution functions to the measured distribution. Primary and eutectic graphite, were found to account for most of the volume of nodular graphite in all cases. For holding times of 40 minutes and greater, corresponding to nodularity roughly below 40 pct, the primary subpopulation was very small and difficult to distinguish, leaving eutectic nodules as the dominant subpopulation. The mode and standard deviation of the two subpopulations were roughly independent of nodularity. Moreover, the nodular and vermicular graphite were segregated in the microstructure. In conclusion, the results suggest that the parallel development of the vermicular eutectic had small influence on the size distribution of eutectic graphite nodules.

  • 41.
    Dong, Zhihua
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. Chongqing University, China.
    Chen, D.
    Long, M.
    Li, Wei
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Chen, H.
    Vitos, Levente
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. Uppsala University, Sweden; Wigner Research Center for Physics, Hungary.
    Computation of Phase Fractions in Austenite Transformation with the Dilation Curve for Various Cooling Regimens in Continuous Casting2016In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 47, no 3, p. 1553-1564Article in journal (Refereed)
    Abstract [en]

    A concise model is applied to compute the microstructure evolution of austenite transformation by using the dilation curve of continuously cast steels. The model is verified by thermodynamic calculations and microstructure examinations. When applying the model, the phase fractions and the corresponding transforming rates during austenite transformation are investigated at various cooling rates and chemical compositions. In addition, ab initio calculations are performed for paramagnetic body-centered-cubic Fe to understand the thermal expansion behavior of steels at an atomic scale. Results indicate that by increasing the cooling rate, the final volume fraction of ferrite/pearlite will gradually increase/decrease with a greater transforming rate of ferrite. The ferrite fraction increases after austenite transformation with lowering of the carbon content and increasing of the substitutional alloying fractions. In the austenite transformation, the thermal expansion coefficient is sequentially determined by the forming rate of ferrite and pearlite. According to the ab initio theoretical calculations for the single phase of ferrite, thermal expansion emerges from magnetic evolution and lattice vibration, the latter playing the dominant role. The theoretical predictions for volume and thermal expansion coefficient are in good agreement with the experimental data.

  • 42.
    Dong, Zhihua
    et al.
    Chongqing Univ, Coll Mat Sci & Engn, Chongqing 400044, Peoples R China.;Royal Inst Technol, Dept Mat Sci & Engn, Appl Mat Phys, SE-10044 Stockholm, Sweden..
    Chen, Dengfu
    Chongqing Univ, Coll Mat Sci & Engn, Chongqing 400044, Peoples R China..
    Long, Mujun
    Chongqing Univ, Coll Mat Sci & Engn, Chongqing 400044, Peoples R China..
    Li, Wei
    Royal Inst Technol, Dept Mat Sci & Engn, Appl Mat Phys, SE-10044 Stockholm, Sweden..
    Chen, Huabiao
    Chongqing Univ, Coll Mat Sci & Engn, Chongqing 400044, Peoples R China..
    Vitos, Levente
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Royal Inst Technol, Dept Mat Sci & Engn, Appl Mat Phys, SE-10044 Stockholm, Sweden.;Wigner Res Ctr Phys, Res Inst Solid State Phys & Opt, H-1525 Budapest, Hungary..
    Computation of Phase Fractions in Austenite Transformation with the Dilation Curve for Various Cooling Regimens in Continuous Casting2016In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 47, no 3, p. 1553-1564Article in journal (Refereed)
    Abstract [en]

    A concise model is applied to compute the microstructure evolution of austenite transformation by using the dilation curve of continuously cast steels. The model is verified by thermodynamic calculations and microstructure examinations. When applying the model, the phase fractions and the corresponding transforming rates during austenite transformation are investigated at various cooling rates and chemical compositions. In addition, ab initio calculations are performed for paramagnetic body-centered-cubic Fe to understand the thermal expansion behavior of steels at an atomic scale. Results indicate that by increasing the cooling rate, the final volume fraction of ferrite/pearlite will gradually increase/decrease with a greater transforming rate of ferrite. The ferrite fraction increases after austenite transformation with lowering of the carbon content and increasing of the substitutional alloying fractions. In the austenite transformation, the thermal expansion coefficient is sequentially determined by the forming rate of ferrite and pearlite. According to the ab initio theoretical calculations for the single phase of ferrite, thermal expansion emerges from magnetic evolution and lattice vibration, the latter playing the dominant role. The theoretical predictions for volume and thermal expansion coefficient are in good agreement with the experimental data.

  • 43. Dong, Zhihua
    et al.
    Li, Wei
    Long, Mujun
    Gui, Lintao
    Chen, Dengfu
    Huang, Yunwei
    Vitos, Levente
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Effect of Temperature Reversion on Hot Ductility and Flow Stress-Strain Curves of C-Mn Continuously Cast Steels2015In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 46, no 4, p. 1885-1894Article in journal (Refereed)
    Abstract [en]

    The influence of temperature reversion in secondary cooling and its reversion rate on hot ductility and flow stress-strain curve of C-Mn steel has been investigated. Tensile specimens were cooled at various regimes. One cooling regime involved cooling at a constant rate of 100 degrees C min(-1) to the test temperature, while the others involved temperature reversion processes at three different reversion rates before deformation. After hot tensile test, the evolution of mechanical properties of steel was analyzed at various scales by means of microstructure observation, ab initio prediction, and thermodynamic calculation. Results indicated that the temperature reversion in secondary cooling led to hot ductility trough occurring at higher temperature with greater depth. With increasing temperature reversion rate, the low temperature end of ductility trough extended toward lower temperature, leading to wider hot ductility trough with slightly reducing depth. Microstructure examinations indicated that the intergranular fracture related to the thin film-like ferrite and (Fe, Mn)S particles did not changed with varying cooling regimes; however, the Widmanstatten ferrite surrounding austenite grains resulted from the temperature reversion process seriously deteriorated the ductility. In addition, after the temperature reversion in secondary cooling, the peak stress on the flow curve slightly declined and the peak of strain to peak stress occurred at higher temperature. With increasing temperature reversion rate, the strain to peak stress slightly increased, while the peak stress showed little variation. The evolution of plastic modulus and strain to peak stress of austenite with varying temperature was in line with the theoretical prediction on Fe. (C) The Minerals, Metals & Materials Society and ASM International 2015

  • 44.
    Dong, Zhihua
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. Chongqing University, China.
    Li, Wei
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Long, Mujun
    Gui, Lintao
    Chen, Dengfu
    Huang, Yunwei
    Vitos, Levente
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. Uppsala University, Sweden.
    Effect of Temperature Reversion on Hot Ductility and Flow Stress-Strain Curves of C-Mn Continuously Cast Steels2015In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 46, no 4, p. 1885-1894Article in journal (Refereed)
    Abstract [en]

    The influence of temperature reversion in secondary cooling and its reversion rate on hot ductility and flow stress-strain curve of C-Mn steel has been investigated. Tensile specimens were cooled at various regimes. One cooling regime involved cooling at a constant rate of 100 degrees C min(-1) to the test temperature, while the others involved temperature reversion processes at three different reversion rates before deformation. After hot tensile test, the evolution of mechanical properties of steel was analyzed at various scales by means of microstructure observation, ab initio prediction, and thermodynamic calculation. Results indicated that the temperature reversion in secondary cooling led to hot ductility trough occurring at higher temperature with greater depth. With increasing temperature reversion rate, the low temperature end of ductility trough extended toward lower temperature, leading to wider hot ductility trough with slightly reducing depth. Microstructure examinations indicated that the intergranular fracture related to the thin film-like ferrite and (Fe, Mn)S particles did not changed with varying cooling regimes; however, the Widmanstatten ferrite surrounding austenite grains resulted from the temperature reversion process seriously deteriorated the ductility. In addition, after the temperature reversion in secondary cooling, the peak stress on the flow curve slightly declined and the peak of strain to peak stress occurred at higher temperature. With increasing temperature reversion rate, the strain to peak stress slightly increased, while the peak stress showed little variation. The evolution of plastic modulus and strain to peak stress of austenite with varying temperature was in line with the theoretical prediction on Fe.

  • 45.
    El-Bealy, Mostafa Omar
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Modeling of Heat Transfer and Interdendritic Strain for Exuded Surface Segregation Layer in the Direct Chill Casting of Aluminum Alloys2016In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 47, no 1, p. 630-648Article in journal (Refereed)
    Abstract [en]

    This investigation on the formation of exuded surface segregation layer "ESSL" is intended to provide experimental and simulated comparison to verify the model developed previously by El-Bealy. Preliminary verification and calibration of the previous 2D mathematical model are demonstrated by quantitative errors between the previous measurements and predictions of temperature and macrosegregation. Also, the results from these comparisons reveal that the errors are in the reasonable and within allowable limits. These comparisons lead to the fact that the exuded surface segregation layer mostly forms on the middle slice of broad sheet ingot face and in the early stages of mold zone. The model predictions point out also that the different interdendritic strain hypotheses associated with fluctuations of mold cooling conditions. This affects the interdendritic liquid flow between the equiaxed crystals which influences the severity of ESSL formation and its macrosegregation level. The mechanism of ESSL with heat flow and interdendritic strain generation has been analyzed and discussed. The quantitative comparisons between the pervious experimental results and numerical simulation in this investigation reveal also several solutions to prevent this defect for future work.

  • 46.
    El-Bealy, Mostafa Omar
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Processing.
    On the Formation of Interdendritic Internal Cracks During Dendritic Solidification of Continuously Cast Steel Slabs2012In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 43, no 6, p. 1488-1516Article in journal (Refereed)
    Abstract [en]

    In this study of solidification during the continuous casting of steel slabs, the effect of the different spray cooling conditions on the interdendritic internal cracks formed between the columnar dendrites has been examined by a metallographic study of the slab samples and by performing a set of mathematical analyses. The metallographic study involved plant trials to measure the slab surface temperature within different secondary spray cooling conditions. Also, macro/microexaminations of the collected samples from plant trials, measurements of dendrite arm spacing, and interdendritic distance between the columnar dendrites, as well as a segment length of interdendritic crack, have been performed. The experimental results show that the morphology of the interdendritic cracks described by the segment width and length fluctuate with the distance from the slab surface based on the secondary spray cooling conditions. A one-dimensional mathematical model of the heat transfer, solidification, structure evolution, interdendritic strain, and elementary interdendritic area (EIA) has been developed. This model takes into account also calculating the width of interdendritic crack. The model predictions are in a good agreement with the measurements. The results pointed out also that this criterion can be considered as the most important tool to measure the inner quality of the continuously cast steel slabs. Therefore, it helps also to define the required mechanism and reduction level of hot working deformation to close these interdendritic internal cracks. The formation mechanism of these cracks during the dendritic solidification of continuously cast steel slabs has been discussed and the available solutions have been proposed.

  • 47.
    El-Bealy, Mostafa Omar
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Processing.
    On the Formation of Macrosegregation and Interdendritic Cracks During Dendritic Solidification of Continuous Casting of Steel2014In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 45, no 3, p. 988-1017Article in journal (Refereed)
    Abstract [en]

    The aim of the current article is to elucidate the significant effects of macrosegregation distribution and its level on the different stages of interdendritic crack formation during dendritic solidification in continuously cast steel slabs. Couple formations of macrosegregation and interdendritic crack phenomena during dendritic solidification of peritectic carbon steels have been investigated by metallographic study of collected slab samples and by performing a set of mathematical analyses. The metallographic study involved plant trails to measure slab surface temperature of different secondary spray cooling conditions. Also, macro-microexaminations, measurements of dendrite arm spacing, macrosegregation analysis, and interdendritic distance between the dendrites of collected samples from plant trials have been performed. The experimental results show a fluctuation of carbon segregation with respect to distance from slab surface. These results also reveal that the interdendritic cracks vary with this fluctuation in various nano, macro, and microscales based on the cooling conditions. A mathematical model of heat transfer, solidification, structure evolution, interdendritic strain, macrosegregation, and elementary interdendritic area "EIA" has been developed. This model takes also into account the calculating of interdendritic distance between the dendrites "IDD" to evaluate the interdendritic crack width. The model predictions of different thermal and solidification phenomena show a good agreement with measurements. The results pointed out also that the coupled effect of interdendritic strain and macrosegregation phenomena and their distributions can be considered as the most important tools to evaluate the surface and internal interdendritic cracks in continuously cast steel slabs. The formation mechanisms of different types of interdendritic crack with interdendritic strain patterns and fluctuation of macrosegregation levels during various cooling zones have been explained, and the possible solutions to these problems have been discussed.

  • 48.
    El-Bealy, Mostafa Omar
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. MTC, Egypt.
    Transient Simulation of Mold Heat Transfer and Solidification Phenomena of Continuous Casting of Steel2016In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 47, no 5, p. 3013-3038Article in journal (Refereed)
    Abstract [en]

    A comprehensive model of heat transfer and solidification phenomena has been developed including microstructure evolution and fluctuation macrosegregation in continuously cast steel slabs with an objective of evaluation of various mold cooling conditions. The study contains plant trials, metallographic examinations, and formulation of mathematical modeling. The plant trials involved sample collection from three slab casters in use at two different steel plants. The metallographic study combined measurements of dendrite arm spacings and macrosegregation analysis of collected samples. A one-dimensional mathematical model has been developed to characterize the thermal, solidification phases, microstructure evolution, interdendritic strain, and therefore, the macrosegregation distributions. Two cooling approaches were proposed in this study to evaluate the Newtonian heat transfer coefficient in various mold regions. The first approach is a direct estimation approach (DEA), whereas the second one is a coupled approach of the interfacial resistor model and direct estimation approach (CIR/DEA). The model predictions and standard analytical models as well as the previous measurements were compared to verify and to calibrate the model where good agreements were obtained. The comparison between the model predictions and the measurements of dendrite arm spacings and fluctuated carbon concentration profiles were performed to determine the model accuracy level with different cooling approaches. Good agreements were obtained by different accuracy levels with different cooling approaches. The model predictions of thermal parameters and isotherms were analyzed and discussed.

  • 49.
    Elfsberg, Jessica
    et al.
    Royal Institute of Technology, Sweden.
    Matsushita, Taishi
    Royal Institute of Technology, Sweden.
    X-ray observation of gas evolution, flotation, and emulsification of molten carbon steel immersed in mold flux2011In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 42, no 2, p. 265-268Article in journal (Refereed)
    Abstract [en]

    At two interfacial-tension measurement experiments with the same experimental conditions, steel samples and mold flux samples of the same compositions were melted in crucibles from the same batch. During the first experiment, the steel drop melted far below its liquidus and then was emulsified. At the second experiment, the steel melted at the expected temperature but did not emulsify. The difference that can be identified is the mass of the steel samples.

  • 50.
    Elfsberg, Jessica
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Matsushita, Taishi
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    X-Ray Observation of Gas Evolution, Flotation, and Emulsification of Molten Carbon Steel Immersed in Mold Flux2011In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 42, no 2, p. 265-268Article in journal (Refereed)
    Abstract [en]

    At two interfacial-tension measurement experiments with the same experimental conditions, steel samples and mold flux samples of the same compositions were melted in crucibles from the same batch. During the first experiment, the steel drop melted far below its liquidus and then was emulsified. At the second experiment, the steel melted at the expected temperature but did not emulsify. The difference that can be identified is the mass of the steel samples.

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