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  • 1.
    Akbarnejad, Shahin
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Jonsson, Lage Tord Ingemar
    Kennedy, Mark William
    Aune, Ragnhild Elizabeth
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Analysis on Experimental Investigation and Mathematical Modeling of Incompressible Flow Through Ceramic Foam Filters2016Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 47, nr 4, s. 2229-2243Artikel i tidskrift (Refereegranskat)
    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.

  • 2.
    Akbarnejad, Shahin
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Saffari Pour, Mohsen
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Jonsson, Lage Tord Ingemar
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Jönsson, Pӓr Göran
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Effect of Fluid Bypassing on the Experimentally Obtained Darcy and Non-Darcy Permeability Parameters of Ceramic Foam Filters2017Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 48, nr 1, s. 197-207Artikel i tidskrift (Refereegranskat)
    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.

  • 3.
    Akbarnejad, Shahin
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Sheng, Dong-yuan
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Processer.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Processer.
    A Computational Fluid Dynamics Study on Physical Refining of Steel Melts by Filtration2023Ingår i: Metals, ISSN 2075-4701, Vol. 13, nr 6, artikel-id 1022Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, a previous experimental investigation on physical refining of steel melts by filtration was numerically studied. To be specific, the filtration of non-metallic alumina inclusions, in the size range of 1-100 & mu;m, was stimulated from steel melt using a square-celled monolithic alumina filter. Computational fluid dynamics (CFD) studies, including simulations of both fluid flow and particle tracing using the one-way coupling method, were conducted. The CFD predicted results for particles in the size range of & LE;5 & mu;m were compared to the published experimental data. The modeled filtration setup could capture 100% of the particles larger than 50 & mu;m. The percentage of the filtered particles decreased from 98% to 0% in the particle size range from 50 & mu;m to 1 & mu;m.

  • 4.
    Akbarnejad, Shahin
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Processer.
    Sheng, Dongyuan
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Processer.
    Jönsson, Pär Göran
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Processer.
    A Computational Fluid Dynamics Study on Physical Refining of Steel Melts by FiltrationManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    In this paper, a previous experimental investigation on physical refining of steel melts by filtration was numerically studied. To be specific, filtration of non-metallic alumina inclusions, in the size range of 1 to 100 [μm], from steel melt by using a square-celled monolithic alumina filter was simulated. Computational fluid dynamics (CFD) studies, including simulations of both fluid flow and particle tracing using one-way coupling method, were conducted. The CFD predicted results for particles in the size range  5 [μm] were compared to the published experimental data. The modelled filtration setup could capture 100 % of the particles larger than 50 [μm]. The percentage of the filtered particles decreases from 98% to 0% in the particle size range of 50 [μm] to 1[μm].

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  • 5.
    Akbarnejad, Shahin
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Tilliander, Anders
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Processer.
    Sheng, Dongyuan
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Processer.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Processer.
    Effect of Batch Dissimilarity on Permeability of Stacked Ceramic Foam Filters and Incompressible Fluid Flow: Experimental and Numerical Investigation2022Ingår i: Metals, ISSN 2075-4701, Vol. 12, nr 6, s. 1001-, artikel-id 1001Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ceramic foam filters (CFFs) are used to remove inclusions and/or solid particles from molten metal. In general, the molten metal poured on the top of a CFF should reach a certain height to form the pressure (metal head) required to prime the filter. For estimating the required metal head and obtaining the permeability coefficients of the CFFs, permeability experiments are essential. Recently, electromagnetic priming and filtration of molten aluminum with low and high grades of CFF, i.e., 30, 50 and 80 pore per inch (PPI) CFFs, have been introduced. Since then, there has been interest in exploring the possibility of obtaining further inclusion entrapment and aluminum refinement by using electromagnetic force to prime and filter with stacked CFFs. The successful execution of such trials requires a profound understanding concerning the permeability parameters of the stacked filters. Such data were deemed not to exist prior to this study. As a result, this study presents experimental findings of permeability measurements for stacks of three 30, three 50 and three 80 PPI commercial alumina CFFs from different industrial batches and compares the findings to numerically modelled data as well as previous research works. Both experimental and numerical findings showed a good agreement with previous results. The deviation between the experimentally and numerically obtained data lies in the range of 0.4 to 6.3%.

  • 6.
    Alekseeva, Ekaterina
    et al.
    Peter Great St Petersburg Polytech Univ, Sci & Technol Complex New Technol & Mat, Inst Adv Engn Technol, Polytech Skaya 29, St Petersburg 194064, Russia..
    Karasev, Andrey
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Jönsson, Pär G.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Alkhimenko, Aleksey
    Peter Great St Petersburg Polytech Univ, Sci & Technol Complex New Technol & Mat, Inst Adv Engn Technol, Polytech Skaya 29, St Petersburg 194064, Russia..
    Effect of Inclusions on the Corrosion Properties of the Nickel-Based Alloys 718 and EP7182020Ingår i: Metals, ISSN 2075-4701, Vol. 10, nr 9, artikel-id 1177Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Inclusions in steels and alloys are known to lower the resistance to deformation, as well as to lower the mechanical, corrosion and other properties. Studies of inclusions in nickel-based alloys are important since these materials could suffer from corrosion degradation in harsh operational conditions. This, in fact, could lead to a pitting initiation around the inclusions. Two industrial Ni-based alloys (alloy 718 and EP718) were investigated to determine the harmful effects of different inclusions on the corrosion resistance of Ni-based alloys. Specifically, the inclusion characteristics (such as composition, morphology, size, number and location) were determined for inclusions collected on film filters after electrolytic extraction and dissolution of a metal matrix around different inclusions on surfaces of metal samples after electrolytic extraction (EE). It was found that both Ni-based alloys contain various inclusion types: carbides (large size NbTi-C and small multicomponent carbides), nitrides TiNb-N and sulphides (TiNb-S in EP718 alloy). The most harmful effects on the corrosion resistance of metal were detected around sulphides and small carbides containing Mo, W, Cr. Dissolution effects were also observed around large carbides and nitrides, especially around inclusions larger than 10 mu m. Moreover, the dissolution of a matrix around inclusions and clusters located on the grain boundaries were found to be 2.1-2.7 times larger compared to inclusions found inside of grains of the given alloy samples.

  • 7.
    Alevanau, Aliaksandr
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Ersson, Mikael
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Kantarelis, Efthymios
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Kuznechik, Olgerd
    Belarussian State University.
    Vyhoniailo, Oleksandr
    Mechanically assisted low temperature pyrolysis of hydrocarbons2014Ingår i: Proceedings of the XVII International Conference Foundations & Advances in Nonlinear Science, September 29 - October 3, Minsk 2014, 2014Konferensbidrag (Refereegranskat)
    Abstract [en]

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

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  • 8.
    Al-Saadi, Munir
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap. R&D Metallurgy, AB Sandvik Materials Technology, SE-811 81 Sandviken, Sweden.
    Hulme-Smith, Christopher
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Processer.
    Sandberg, Fredrik
    R&D Metallurgy, AB Sandvik Materials Technology, SE-811 81 Sandviken, Sweden.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Processer.
    Hot Deformation Behaviour and Processing Map of Cast Alloy 825Manuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Alloy 825 is a nickel-based alloy that is commonly used in applications where both high strength and corrosion resistance are required. Applications include tanks in the chemical, food and petrochemical industries and oil and gas pipelines. Components made from Alloy 825 are often manufactured using hot deformation. However, there is no systematic study to optimise the processing conditions reported in literature. In this study, a processing map for as-cast Alloy 825 is established to maximise the power dissipation efficiency of hot deformation and correlate the processing conditions to final materials properties. The hot deformation behaviour of equiaxed Alloy 825 is characterized on the basis of the dynamic materials model and compression data in the temperature range of 950 °C to 1250 °C at an interval of 50°C and strain rate range of 0.01 s-1 to 10 s-1 to a true strain of 0.7 using a Gleeble-3500 thermomechanical simulator. Flow stress is modelled by the constitutive equation based on a hyperbolic sine function. The deformed material is characterized using Vickers hardness, optical microscopy and scanning electron microscopy, including electron backscattered diffraction. The true stress-true strain curves exhibit peak stresses followed by softening due to occurrence of dynamic recrystallization. The value of stress exponent in the hyperbolic sine-based constitutive equation, n=5.0. This suggests that the rate-limiting mechanism of deformation is climb (diffusion)-mediated dislocation glide. The activation energy for plastic flow in the temperature range tested is about 450 kJ mole-1, and the relationship between flow stress and temperature-compensated strain rate (via the Zener-Hollomon parameter) was found to be valid across this temperature range. The maximum power dissipation efficiency is over 35%. The highest efficiency is observed over temperature range of 1100 °C – 1250 °C and a strain rate of 0.01 s-1 – 0.1s-1. These are the optimum conditions for hot working. The optimum processing parameters for good strain hardening are obtained in the temperature range of between  950 °C  and  1100 °C with a strain rate between  0.3/s  and 10.0/s. 

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  • 9.
    Al-Saadi, Munir
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Hulme-Smith, Christopher
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Processer.
    Sandberg, Fredrik
    AB Sandvik Materials Technology.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Processer.
    Hot Deformation Behaviour and Processing Map of Cast Alloy 8252021Ingår i: Journal of materials engineering and performance (Print), ISSN 1059-9495, E-ISSN 1544-1024Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Alloy 825 is a nickel-based alloy that is commonly used in applications where both high strength and corrosion resistance are required, such as tanks in the chemical, food and petrochemical industries and oil and gas pipelines. Components made from Alloy 825 are often manufactured using hot deformation. However, there is no systematic study to optimise the processing conditions reported in literature. In this study, a processing map for as-cast Alloy 825 is established to maximise the power dissipation efficiency of hot deformation in the temperature range of 950 to 1250 °C at an interval of 50 °C and strain rate range of 0.01s−1 to 10.0s−1 to a true strain of 0.7 using a Gleeble-3500 thermomechanical simulator. The processing conditions are also correlated to the Vickers hardness of the final material, which is also characterised using optical microscopy and scanning electron microscopy, including electron backscattered diffraction. The true stress-true strain curves exhibit peak stresses followed by softening due to occurrence of dynamic recrystallization. The activation energy for plastic flow in the temperature range tested is approximately 450 kJ mol−1, and the value of the stress exponent in the (hyperbolic sine-based) constitutive equation, n=5.0, suggests that the rate-limiting mechanism of deformation is dislocation climb. Increasing deformation temperature led to a lower Vickers hardness in the deformed material, due to increased dynamic recrystallization. Raising the strain rate led to an increase in Vickers hardness in the deformed material due to increased work hardening. The maximum power dissipation efficiency is over 35%, obtained for deformation in the temperature range 1100-1250 °C and a strain rate of 0.01s−1-0.1s−1. These are the optimum conditions for hot working.

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  • 10.
    Al-Saadi, Munir
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Sandberg, Fredrik
    Karasev, Andrey
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Jonsson, Stefan
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Microstructure characterisation in alloy 8252018Konferensbidrag (Refereegranskat)
  • 11.
    Al-Saadi, Munir
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Karasev, Andrey
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Sandberg, Fredrik
    Comparative Study of Microstructures Evolution of Columnar and Equiaxed Grain Structurs in Alloy 825 after Hot Compression2018Ingår i: 3rd InternationalConference on Ingot Casting, Rolling and Forging, ICRF2018, in Stockholm, 16-19October, 2018, artikel-id 114Konferensbidrag (Refereegranskat)
  • 12.
    Al-Saadi, Munir
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Processer. Sandvik Materials Technology AB.
    Mu, Wangzhong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Strukturer.
    Hulme-Smith, Christopher
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Processer.
    Sandberg, Fredrik
    Sandvik Materials Technology AB.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Processer.
    Effect of Trace Magnesium Additions on the Dynamic Recrystallization in Cast Alloy 825 after One-Hit Hot-Deformation2021Ingår i: Metals, ISSN 2075-4701, Vol. 11, nr 1, artikel-id 36Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Alloy 825 is widely used in several industries, but its useful service life is limited by both mechanical properties and corrosion resistance. The current work explores the effect of the addition of magnesium on the recrystallization and mechanical behavior of alloy 825 under hot compression. Compression tests were performed under conditions representative of typical forming processes: temperatures between 1100 and 1250 °C and at strain rates of 0.1–10 s−1 to a true strain of 0.7. Microstructural evolution was characterized by electron backscattered diffraction. Dynamic recrystallization was found to be more prevalent under all test conditions in samples containing magnesium, but not in all cases of conventional alloy 825. The texture direction ⟨101⟩ was the dominant orientation parallel to the longitudinal direction of casting (also the direction in which the samples were compressed) in samples that contained magnesium under all test conditions, but not in any sample that did not contain magnesium. For all deformation conditions, the peak stress was approximately 10% lower in material with the addition of magnesium. Furthermore, the differences in the peak strain between different temperatures are approximately 85% smaller if magnesium is present. The average activation energy for hot deformation was calculated to be 430 kJ mol−1 with the addition of magnesium and 450 kJ mol−1 without magnesium. The average size of dynamically recrystallized grains in both alloys showed a power law relation with the Zener–Hollomon parameter, DD~Zn, and the exponent of value, n, is found to be 0.12. These results can be used to design optimized compositions and thermomechanical treatments of alloy 825 to maximize the useful service life under current service conditions. No experiments were conducted to investigate the effects of such changes on the service life and such experiments should now be performed.

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  • 13.
    Al-Saadi, Munir
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap. R&D, AB Sandvik Materials Technology, SE-811 81 Sandviken.
    Sandberg, Fredrik
    R&D, AB Sandvik Materials Technology, SE-811 81 Sandviken.
    Hulme-Smith, Christopher
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Modelling of strengthening mechanisms in wrought nickel-based 825 alloy subjected to solution annealing2021Ingår i: Metals, ISSN 2075-4701, Vol. 11, nr 5, s. 771-20Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Wrought nickel‐based Alloy 825 is widely used in the oil and gas industries, attributed toits high strength at temperatures up to 540 °C. However, differences in mechanical properties arisein finished components due to variations in both grain size and dislocation density. Numerous ex‐perimental studies of the strengthening mechanisms have been reported and many models havebeen developed to predict strengthening under thermomechanical processing. However, there aredebates surrounding some fundamental issues in modeling and the interpretation of experimentalobservations. Therefore, it is important to understand the evolution of strain within the materialduring the hot‐forging process. In addition, there is a lack of research around the behavior duringhot deformation and subsequent stabilization of Alloy 825. This article investigates the origin of thisstrength and considers a variety of strengthening mechanisms, resulting in a quantitative predictionof the contribution of each mechanism. The alloy is processed with a total forging strain of 0.45, 0.65,or 0.9, and subsequent annealing at a temperature of 950 °C, reflecting commercial practice. Themicrostructure after annealing is similar to that before annealing, suggesting that static recovery isdominant at this temperature. The maximum yield strength and ultimate tensile strength were348 MPa and 618 MPa, respectively, obtained after forging to a true strain of 0.9, with a ductility of40%. The majority of strengthening was attributed to grain refinement, the dislocation densities thatarise due to the large forging strain deformation, and solid solution strengthening. Precipitatestrengthening was also quantified using the Brown and Ham modification of the Orowan bowingmodel. The results of yield strength calculations are in excellent agreement with experimental data,with less than 1% difference. The interfacial energy of Ti(C,N) in the face‐centered cubic matrix of. These results can bethe current alloy has been assessed for the first time, with a value of 0.8 mJm−2used by future researchers and industry to predict the strength of Alloy 825 and similar alloys, es‐pecially after hot‐forging.

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  • 14.
    Al-Saadi, Munir
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi. R&D, AB Sandvik Materials Technology, SE-811 81Sandviken, Sweden..
    Sandberg, Fredrik
    R&D, AB Sandvik Materials Technology, SE-811 81Sandviken, Sweden..
    Hulme-Smith, Christopher
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Karasev, Andrey
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    A study of the static recrystallization behaviour of cast Alloy 825 after hot-compressions2019Ingår i: Journal of Physics: Conference Series, 2019, Vol. 1270, artikel-id 012023Konferensbidrag (Refereegranskat)
    Abstract [en]

    The static recrystallization behaviour of a columnar and equiaxed Alloy 825 material was studied on a Gleeble-3800 thermo-simulator by single-hit compression experiments. Deformation temperatures of 1000-1200 °C, a strain of up to 0.8, a strain rate of 1s-1, and relaxation times of 30, 180, and 300 s were selected as the deformation conditions to investigate the effects of the deformation parameters on the SRX behaviour. Furthermore, the influences of the initial grain structures on the SRX behaviors were studied. The microstructural evolution was studied using optical microscopy and EBSD. The EBSD measurements showed a relaxation time of 95 % for fractional recrystallization grains, 𝑡95, in both structures, was less than 30 seconds at the deformation temperatures 1100 °C and 1200 °C. However, fewer than 95% of recrystallized grains recrystallized when the deformation temperature was lowered to 1000 °C. From the grain-boundary misorientation distribution in statically recrystallized samples, the fraction of high-angle grain boundaries decreased with an increasing deformation temperature from 1000 °C to 1200 °C for a given relaxation time. This was attributed to grain coarsening

  • 15.
    Al-Saadi, Munir
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap. R&D, AB Sandvik Materials Technology, SE-811 81Sandviken, Sweden..
    Sandberg, Fredrik
    R&D, AB Sandvik Materials Technology, SE-811 81Sandviken, Sweden..
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Processer.
    Hulme-Smith, Christopher
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Processer.
    Influence of Strain Magnitude on Microstructure, Texture and Mechanical Properties of Alloy 825 during hot-forgingManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Alloy 825 is a nickel-base alloy that is common in applications with high stresses and corrosive environments. It is commonly processed by hot forging, but there are few data about how hot forging affects the microstructure, which is critical for both mechanical and corrosion performance. Here, the alloy was hot forged in a commercial thermomechanical process to three industrially-relevant strains and the microscture was examined using scanning electron microscopy and EBSD. The tensile properties were also measured after thermomechanical treatment. Dynamic recrystallization was prevalent during the process, so increasing the forging strain leads to smaller grains and also higher dislocation density. Data were combined to allow the 0.2% proof stress to be calculated as a function of forging strain. All forging strains were sufficient to meet the criteria of the relevant industrial standard for this material. The maximum yield strength and ultimate tensile strength were obtained after forging to a true strain of 0.9 were 413 MPa and 622 MPa, respecitvely, with a ductlity of 40%. This may be used to tailor thermomechanical treatments to achieve precise mechanical properties and serve as a basis for future studies into the corrosion performance of this alloy as a function of forging strain.

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  • 16.
    Andersson, Nils
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Tilliander, Anders
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jonsson, Lage
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Fundamental decarburisation model of AOD process2013Ingår i: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 40, nr 5, s. 390-397Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A mathematical fluid flow model of gas injection in an argon–oxygen decarburisation (AOD) converter process has been coupled with a high temperature thermodynamic model. The current model is a further enhancement of an earlier developed three-dimensional, three-phase model, to also include some thermodynamics of the process. The model is based on fundamental transport equations and includes separate solutions for the steel, slag and the gas phases and their coupling by friction. The AOD model has been used to predict the first injection stage of decarburisation in an AOD converter. The predictions have been found to agree well with the corresponding results from an industrial process control model. One of the important observations from the simulations was that large concentration gradients of carbon exist in the AOD at an early stage and as the first injection step approaching its end the carbon gradients diminish. Also, the results show, in accordance with theory, that the local decarburisation rate is decreased at elevated pressures.

  • 17.
    Andersson, Nils
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Tilliander, Anders
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jonsson, Lage
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Investigating the effectof slag on decarburization in an AOD converter using a fundamental model2013Ingår i: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 84, nr 2, s. 169-177Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A high-temperature thermodynamics model has been coupled with a fundamental mathematical model describing the fluid flow, where boundary conditions were chosen based on data for an industrial AOD converter. Using this model, the effect of both slag phases (a liquid part and a solid part) on the decarburization was studied. More specifically, the separation of chromium oxide to liquid slag as well as the effect of the amount of rigid top slag (solid)on the decarburization was investigated. The liquid slag was considered with respect to the uptake of chromium oxide, while the rigid top slag was only considered with respect to the increase of the metallostatic pressure in the steel melt. The results suggest that separation of chromium oxide to liquid slag results in a decreased decarburization rate. The same conclusion can be drawn with respect to the amount of solid top slag.

  • 18.
    Andersson, Nils
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Tilliander, Anders
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jonsson, Lage
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Preliminary investigation of influence of temperature on decarburisation using fundamental AOD model2013Ingår i: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 40, nr 7, s. 551-558Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A high temperature thermodynamics model was earlier coupled with a fundamental mathematical model describing the fluid flow in an argon–oxygen decarburisation (AOD) converter and was initially validated for an idealised temperature description. More specifically, a linear average temperature relation was used such that the temperature would be isolated from other effects such as reactions and mixing. Thereafter, the effect of the starting temperature on the decarburisation was studied. The purpose is to provide some initial knowledge about how temperature affects the decarburisation in an AOD converter. The results suggest that the thermodynamic limit for carbon concentration after reaching the carbon removal efficiency (CRE) maxima is vertically translated downwards at higher temperatures. Furthermore, when plotting the mass ratio between CO and CO2, there is an indication of a point that may relate to a CRE maximum.

  • 19.
    Andersson, Nils Å. I.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Tilliander, Anders
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jonsson, Lage T. I.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jönsson, Pär G.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    An in-Depth Model-Based Analysis of Decarburization in the AOD Process2012Ingår i: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 83, nr 11, s. 1039-1052Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A previously reported flow and reaction model for an argon-oxygen decarburization converter was extended to also include a thermodynamic description. An in-depth study of the model results has been conducted to answer how concentrations of elements and species in the converter at different locations change with time. This may contribute to the understanding of the mechanisms of the refining procedure in the argon-oxygen decarburization process. The refining procedure includes several step-wise changes of an injected gas composition to higher and higher inert gas ratio, called step changes. A step change leads to a decreased partial pressure of carbon monoxide and maintains the decarburization at a higher efficiency. The results shows early and late concentration profiles for the first injection step and suggests a way to determine when a step change should be made. Moreover, the step change could be determined by calculating the carbon concentration profiles and deciding when the carbon concentration gradients start to diminish.

  • 20.
    Arzpeyma, Niloofar
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap. Kobolde & Partners AB, S-11860 Stockholm, Sweden..
    Alam, Moudud
    Dalarna Univ, Sch Informat & Engn, S-79188 Falun, Sweden..
    Gyllenram, Rutger
    Kobolde & Partners AB, S-11860 Stockholm, Sweden..
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Model Development to Study Uncertainties in Electric Arc Furnace Plants to Improve Their Economic and Environmental Performance2021Ingår i: Metals, ISSN 2075-4701, Vol. 11, nr 6, artikel-id 892Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A statistical model is developed in order to simulate the melt composition in electric arc furnaces (EAFs) with respect to uncertainties in (1) scrap composition, (2) scrap weighing and (3) element distribution factors. The tramp element Cu and alloying element Cr are taken into account. The model enables simulations of a charge program as well as backwards estimations of the element concentrations and their variance in scrap. In the backwards calculation, the maximum likelihood method is solved by considering three cases corresponding to the involved uncertainties. It is shown that the model can estimate standard deviations for elements so that the real values lie within the estimated 95% confidence interval. Moreover, the results of the model application in each target product show that the estimated scrap composition results in a melt composition, which is in good agreement with the measured one. The model can be applied to increase our understanding of scrap chemical composition and lower the charged material cost and carbon footprint of the products.

  • 21.
    Arzpeyma, Niloofar
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Ersson, Mikael
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Mathematical Modeling of Postcombustion in an Electric Arc Furnace (EAF)2019Ingår i: Metals, ISSN 2075-4701, Vol. 9, nr 5, artikel-id 547Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Numerical modeling was used to study the capability of postcombustion in an electric arc furnace (EAF) equipped with virtual lance burners. The CO flow rate at the molten bath surface was estimated using the off-gas data obtained close to the outlet of an EAF. Then, the effect of the secondary oxygen flow rate on postcombustion was studied. The results show a CO flow rate of 0.6 kgs(-1) and 0.8 kgs(-1) for operation modes of burner and burner + lancing. Increase of the secondary oxygen flow rates of 60% and 70% result in 17% and 7% increase in the postcombustion ratio (PCR) for the burner and burner lancing modes, respectively.

  • 22.
    Arzpeyma, Niloofar
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Ersson, Mikael
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Modeling of post combustion inside the off-gas duct system of the Ovako electric arc furnace2014Ingår i: CDF 2014: 10th International Conference on CFD in Oil & Gas, Metallurgical and Process Industries, SINTEF, Trondheim, Norway, 17-19 June 2014, Proceedings, 2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    In order to study the post combustion (PC) inside the duct system of an electric arc furnace (EAF), a three-dimensional computational fluid-dynamics (CFD) model was developed. The reactions between the off gas species (oxygen and hydrogen) and oxygen which leaked into the duct, through the air gap, was considered. The off-gas composition, the off –gas velocity and the outlet pressure were considered as parameters affecting the PC. The results showed that there was a considerable amount of the uncombusted CO to be captured. The highest CO concentration was found at the central part of the duct. The results also showed that a higher off-gas mass flow rate and a higher power of the outlet fan led to a higher combustion of CO and H2. An off-gas analysis probe was then installed after the air gap, where the tip of the probe was placed according to the predicted high CO concentration area found in the simulations. Thereafter, the measured off-gas composition was used to predict the off-gas composition at the outlet of the EAF.

  • 23.
    Arzpeyma, Niloofar
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap. Kobolde & Partners AB, Stockholm 11860, Sweden.
    Gyllenram, Rutger
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap. Kobolde & Partners AB, Stockholm 11860, Sweden.
    Jönsson, Pär G.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Development of a Mass and Energy Balance Model and Its Application for HBI Charged EAFs2020Ingår i: Metals, ISSN 2075-4701, Vol. 10, nr 3, artikel-id 311Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A static mass and energy balance model combined with a MgO saturation slag model is developed for electric arc furnaces. The model parameters including distribution ratios and dust factors are calibrated for a specific furnace using experimental data. Afterward, the model is applied to study the effect of charging different amounts of hot briquetted iron (HBI) on energy consumption, charged slag former amount, and slag composition. The following results were obtained per each 1% increase of HBI additions: (i) a 0.16 Nm(3)/t decrease in the amount of injected oxygen for metal oxidation, (ii) a 1.29 kWh/t increase in the electricity consumption, and (iii) a 34 kg increase in the amount of the slag.

  • 24.
    Arzpeyma, Niloofar
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Widlund, Ola
    Ersson, Mikael
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Mathematical Modeling of Scrap Melting in an EAF Using Electromagnetic Stirring2013Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 53, nr 1, s. 48-55Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Numerical modeling has been used to investigate the influence of electromagnetic stirring on melting of a single piece of scrap in an eccentric bottom tapping (EBT) electric arc furnace (EAF). The heat transfer and fluid flow in the melt for both conditions with and without electromagnetic stirring were studied. The buoyancy and electromagnetic forces were considered as the source terms for momentum transfer in the studied conditions. The enthalpy-porosity technique was applied to track the phase change of a scrap piece defined in the EBT region of the furnace. Different scrap sizes, preheating temperatures, stirring directions and force magnitudes were considered, and the heat transfer coefficient was estimated from the heat transfer rate at the melt-scrap interface. The results showed that electromagnetic stirring led to a reduced melting time and an increased heat transfer coefficient by a factor of four. The results for Nusselt number versus Grashof number for natural convection and Reynolds number for electromagnetic stirring were compared with those obtained through correlations from previous studies.

  • 25.
    Aune, Ragnhild E.
    et al.
    Norwegian Univ Sci & Technol NTNU, Norway.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    The Seetharaman Seminar June 14-15, 2010 in Stockholm, Sweden: Materials Processing Towards Properties2010Ingår i: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 81, nr 10, s. 811-Artikel i tidskrift (Övrigt vetenskapligt)
  • 26.
    Bai, Haitong
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Ersson, Mikael
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jonsson, Par
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Effect of TurboSwirl Structure on an Uphill Teeming Ingot Casting Process2015Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 46, nr 6, s. 2652-2665Artikel i tidskrift (Refereegranskat)
    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.

  • 27.
    Bai, Haitong
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Ersson, Mikael
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Numerical study of an application of a divergent reverse TurboSwirl nozzle in the billet continuous casting process2019Ingår i: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 46, nr 2, s. 148-158Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The swirling flow has widely been investigated for liquid steel flowing in the continuous casting process. In this paper, a new design of the submerged entry nozzle (SEN) is applied by using a reverse TurboSwirl device with a divergent nozzle. This divergent reverse TurboSwirl nozzle (DRTSN) is shown to gain a more beneficial flow pattern compared to the straight nozzle. A stronger swirling flow can be obtained at the SEN outlet, which leads to a calmer flow field and an appropriately active meniscus flow that could improve the heat and mass transfer near the meniscus. The swirl number in the SEN is independent of the casting speed, while a lower casting speed yields a lower maximum wall shear stress. The DRTSN is connected to the tundish by an elbow and a horizontal runner. A longer horizontal runner supplies a more uniform velocity profile and a more symmetrical flow pattern.

  • 28.
    Bai, Haitong
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Ersson, Mikael
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    The physical and mathematical modelling of swirling flow by turboswirl in an uphill teeming ingot casting process2015Ingår i: Proceedings of the 6th International Congress on the Science and Technology of Steelmaking, ICS 2015, Chinese Society for Metals , 2015, s. 473-476Konferensbidrag (Refereegranskat)
    Abstract [en]

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

  • 29.
    Bai, Haitong
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Ersson, Mikael
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jönsson, Pär G.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    An Experimental and Numerical Study of Swirling Flow Generated by TurboSwirl in an Uphill Teeming Ingot Casting Process2016Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 56, nr 8, s. 1404-1412Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A swirling flow has been demonstrated to be beneficial for making the flow pattern even and to reduce turbulence during filling in ingot casting. A new swirling flow generation device, TurboSwirl, was applied to improve the flow pattern of the liquid steel as it flows into the mold so that a more stable flow could be obtained. A water model was built including the TurboSwirl with different flaring angles of the divergent nozzle, according to a former numerical study indicating that a much more beneficial flow pattern could be obtained by reducing the flaring angle. To validate the mathematical model, the air-core vortex formed in the water model experiment was used, and the length of the vortex was measured and compared to the numerical predictions. Different turbulence models including the standard k-epsilon, realizable k-epsilon and Reynolds stress model were tested. It was found that only the Reynolds stress model could most accurately simulate the high swirling flow including a vortex. In addition, the radial velocity of the water around the vortex was measured by an ultrasonic velocity profiler (UVP). The experimental results revealed a high turbulence of the swirling flow and strong fluctuations of the vortex. The radial velocity of the water around the upper part of the vortex could be predicted well compared to the experimental results by the UVP measurements.

  • 30.
    Bai, Haitong
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Ersson, Mikael
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jönsson, Pär G.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Experimental Validation and Numerical Analysis of the Swirling Flow in a Submerged Entry Nozzle and Mold by using a Reverse TurboSwirl in a Billet Continuous Casting Process2016Ingår i: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344XArtikel i tidskrift (Refereegranskat)
    Abstract [en]

    As an alternative to some traditional methods to generate a swirling flow in the continuous casting process, the use of a new swirling flow generator, TurboSwirl, was studied. Specifically, a reversed TurboSwirl device was designed as part of a submerged entry nozzle (SEN) for a round billet continuous casting process. Mathematical modelling was used to investigate this new design and a water model experiment was carried out to validate the mathematical model. The predicted velocities by the turbulence models: realizable k-ε model, Reynold stress model (RSM) and detached eddy simulation (DES) were compared to the measured results from an ultrasound velocity profile (UVP) method. The DES model could give the best prediction inside the SEN and had a deviation less than 3.1% compared to the measured results. Moreover, based on the validated mathematical model and the new design of the SEN, the effect of the swirling flow generated by the reverse TurboSwirl on the flow field of the SEN and mold was compared to the design of the electromagnetic swirl flow generator (EMSFG). A very strong swirling flow in the SEN and a stable flow pattern in the mold could be obtained by the reverse TurboSwirl compared to the EMSFG. 

  • 31.
    Bai, Haitong
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Ni, Peiyuan
    Northeastern Univ, Sch Met, Key Lab Ecol Met Multimet Intergrown Ores, Educ Minist, Shenyang 110819, Liaoning, Peoples R China.;Osaka Univ, Grad Sch Engn, Dept Mat & Mfg Sci, 2-1 Yamadaoka, Suita, Osaka 5650871, Japan..
    Ersson, Mikael
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Zhang, Tingan
    Northeastern Univ, Sch Met, Key Lab Ecol Met Multimet Intergrown Ores, Educ Minist, Shenyang 110819, Liaoning, Peoples R China..
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Effect of swirling flow tundish submerged entry nozzle outlet design on multiphase flow and heat transfer in mould2019Ingår i: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Effect of a swirling flow SEN (submerged entry nozzle) outlet design on the multiphase flow and heat transfer in a mould was investigated by using numerical simulation. It was found that different SEN outlet designs could form different flow patterns and temperature distributions on the upper of the mould. The enlarged outlet SEN design had an effect to decrease the horizontal velocity of liquid steel flowing out the SEN outlet, reducing the steel flow velocity towards the solidification front. Although a higher velocity was found near the slag/steel interface with the enlarged outlet SEN, but the turbulent kinetic energy was lower. The reason was that less circulation flows were formed in the region of the mould top. The weak horizontal flow towards the solidification front with the enlarged outlet SEN induced lower wall shear stresses, at the same time it also formed a lower temperature distribution near the solidified shell.

  • 32.
    Bi, Yanyan
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Karasev, Andrey
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jönsson, Pär G.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Investigations of inclusions in ferrochromium alloys2014Ingår i: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 41, nr 10, s. 756-762Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 33.
    Bi, Yanyan
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Karasev, Andrey
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jönsson, Pär G.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Three Dimensional Evaluations of REM Clusters in Stainless Steel2014Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 54, nr 6, s. 1266-1273Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 34.
    Bi, Yanyan
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Karasev, Andrey
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jönsson, Pär G.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Three-dimensional investigations of inclusions in ferroalloys2014Ingår i: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 85, nr 4, s. 659-669Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 35.
    Bi, Yanyan
    et al.
    KTH.
    Karasev, Andrey V.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jönsson, Pär G.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Three-dimensional determinations of the non-metallic inclusions in different ferroalloys2014Konferensbidrag (Refereegranskat)
    Abstract [en]

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

  • 36.
    Bi, Yanyan
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Karasev, Andrey Vladimirovich
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jönsson, Pär G.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Evolution of Different Inclusions during Ladle Treatment and Continuous Casting of Stainless Steel2013Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 53, nr 12, s. 2099-2109Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 37.
    Björklund, Johan
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Andersson, Margareta
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    The Influence of Vacuum Treatment on Inclusion Composition: Laboratory Study2010Ingår i: High Temperature Materials and Processes, ISSN 0334-6455, E-ISSN 2191-0324, Vol. 29, nr 3, s. 189-202Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 38.
    Björklund, Johan
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Andersson, Margareta
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    The Influence of Vacuum Treatment on Inclusion Composition: Theoretical Study2010Ingår i: High Temperature Materials and Processes, ISSN 0334-6455, E-ISSN 2191-0324, Vol. 29, nr 3, s. 179-187Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 39.
    Bolívar Caballero, José Juan
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Processer.
    Han, Tong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Processer.
    Svanberg, Rikard
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Processer.
    Zaini, Ilman Nuran
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Processer.
    Yang, Hanmin
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Processer.
    Gond, Ritambhara
    Department of Chemistry, Uppsala University, Lägerhyddsvägen 1, 751 21 Uppsala, Sweden, Lägerhyddsvägen 1.
    Cao, Pengcheng
    Kanthal AB, Sörkvarnsvägen 3, 734 27 Hallstahammar, Sweden, Sörkvarnsvägen 3.
    Lewin, Thomas
    Kanthal AB, Sörkvarnsvägen 3, 734 27 Hallstahammar, Sweden, Sörkvarnsvägen 3.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Processer.
    Yang, Weihong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Processer.
    Advanced application of a geometry-enhanced 3D-printed catalytic reformer for syngas production2023Ingår i: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 287, artikel-id 117071Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Catalyst research on reforming processes for syngas production has mainly focused on the active metals and support materials, while the effect of the catalyst's geometry on the reforming reactions has been poorly studied. The application of 3D-printed materials with enhanced geometries has recently started to be studied in heterogeneous catalysis and is of interest to be implemented for reforming biomass and plastic waste to produce H2-rich syngas. In this study, a geometry-enhanced 3D-printed Ni/Al2O3/FeCrAl-based monolithic catalyst with a periodic open cellular structure (POCS) was designed and fabricated. The catalyst was used for batch steam reforming biomass pyrolysis volatiles for syngas production at different parameters (temperature and steam-to-carbon ratio). The results showed complete reforming of pyrolysis volatiles in all experimental cases, a high H2 yield of ≈ 7.6 wt% of biomass was obtained at the optimized steam-to-carbon ratio of 8 and a reforming temperature of 800 °C, which is a higher yield compared to other batch reforming tests reported in the literature. Moreover, CFD simulation results in COMSOL Multiphysics demonstrated that the POCS configuration improves the reforming of pyrolysis volatiles for tar/bio-oil reforming and H2 production thanks to enhanced mass and heat transfer properties compared to the regular monolithic single-channel configuration.

  • 40.
    Bu, Junfu
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jönsson, Pär G.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Zhao, Zhe
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi. Shanghai Institute of Technology, China.
    Ionic conductivity of dense BaZr(0.5)Ce(0.3)Ln(0.2)O(3-delta) (Ln = Y, Sm, Gd, Dy) electrolytes2014Ingår i: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 272, s. 786-793Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 41.
    Bu, Junfu
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jönsson, Pär G.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Zhao, Zhe
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Keramteknologi.
    Preparation of 30 mol.% Y-doped hafnia (Hf0.7Y0.3O2-delta) using a modified solid-state reaction method2015Ingår i: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 41, nr 2, s. 2611-2615Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 42.
    Bu, Junfu
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jönsson, Pär G.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Zhao, Zhe
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi. Shanghai Institute of Technology, China .
    Sintering behaviour of the protonic conductors BaZr(x)Ce(0.8-x)Ln(0.2)O(3-delta) (x=0.8, 0.5, 0.1; Ln=Y, Sm, Gd, Dy) during the solid-state reactive-sintering process2015Ingår i: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 41, nr 2, s. 2558-2564Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 43.
    Bu, Junfu
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jönsson, Pär Göran
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Zhao, Zhe
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap. Shanghai Institute of Technology, China.
    Dense and translucent BaZrxCe0.8-xY0.2O3-delta (x=0.5, 0.6, 0.7) proton conductors prepared by spark plasma sintering2015Ingår i: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 107, s. 145-148Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Dense and translucent BaZrxCe0.8-xY0.2O3-delta (x = 0.5, 0.6, 0.7) proton conductors were firstly and successfully prepared by Spark Plasma Sintering (SPS) at a temperature of 1350 degrees C without sintering aids' addition. XRD, SEM and EDS were applied to determine the phase purity, morphology and element composition of prepared pellets, respectively. Moreover, the sintering behaviors of these proton conductors were monitored and analyzed through the on-line sintering curves. The obtained results indicate that a lowered sintering temperature (<1400 degrees C) and a fast cooling rate (>= 200 degrees C/min) represent two key parameters to prepare dense Ce-containing BaZrO3-BaCeO3 based proton conductors.

  • 44.
    Bu, Junfu
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Jönsson, Pär Göran
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Zhao, Zhe
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap. Shanghai Institute of Technology, China.
    Electrical conductivities of translucent BaZr(X)Ce0.8-XY0.2O3-delta (x=0.5, 0.6, 0.7) ceramics2016Ingår i: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 115, s. 87-90Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The electrical conductivities of translucent BaZr0.5Ce0.3Y0.2O3-delta (x = 0.5, BZCY532), BaZr0.6Ce0.2Y0.2O3-delta (x = 0.6, BZCY622) and BaZr0.7Ce0.1Y0.2O3-delta(x = 0.7, BZCY712) proton conductors were investigated systematically in different atmospheres and also at different oxygen partial pressures. The obtained results indicate that translucent BZCY532, BZCY622 and BZCY712 ceramics are pure oxygen-ion and proton conductors without unfavorable electronic conduction. In addition, they represent promising proton conductors to be used as intermediate temperature solid oxide fuel cell electrolytes.

  • 45.
    Bu, Junfu
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Jönsson, Pär Göran
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Zhao, Zhe
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    The effect of NiO on the conductivity of BaZr0.5Ce0.3Y0.2O3-delta based electrolytes2016Ingår i: RSC Advances, E-ISSN 2046-2069, Vol. 6, nr 67, s. 62368-62377Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effects of NiO on the sintering behaviors, morphologies and conductivities of BaZr0.5Ce0.3Y0.2O3-delta (BZCY532) based electrolytes were systematically investigated. 1 wt% NiO powder was added by different methods during the sample preparation: (i) added during ball-milling before a powder mixture calcination (named BZCY(Ni) 532), (ii) no NiO addition in the whole preparation procedure (named BZCY532) and (iii) added after a powder mixture calcination (named BZCY532(Ni)). The conductivities of these three kinds of dense BZCY532 ceramics were investigated in dry air, wet N-2 and wet H-2 atmospheres, respectively. Moreover, the electronic contributions to the total conductivities were also identified in a broad oxygen partial pressure range. According to the achieved results, it can be concluded that the dense BZCY(Ni) 532 ceramics showed the best enhanced oxygen and proton conductivities, followed by the BZCY532(Ni) and BZCY532 ceramics. Furthermore, the BZCY(Ni) 532 and BZCY532 ceramics showed a tiny electronic conductivity, when the testing temperatures were lower than 800 degrees C. However, the BZCY532(Ni) ceramics revealed an obvious electronic conduction when they were tested at temperatures of 600-800 degrees C. Therefore, it is preferable to add the NiO during powder preparation, which can lower the sintering temperature and also increase the conductivity of BZCY532-based electrolytes.

  • 46.
    Bu, Junfu
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Zhao, Zhe
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi. Department of Materials Science and Engineering, Shanghai Institute of Technology, China.
    Preparation of Potential Protonic Conductor Yttria Doped Hafnia by Using the Modified Solid State Reaction Method2014Ingår i: ECS Transactions, 2014, Vol. 59 (1), s. 315-320Konferensbidrag (Refereegranskat)
    Abstract [en]

    A pure and well crystalized yttrium doped hafnium oxide Hf0.69Y0.31O2-δ (YSH) is obtained by using a modified solid state reaction method, where a water-based milling medium and freeze drying are implemented to reduce the agglomeration. The mean sizes of the YSH powder, which is obtained through a traditional alcohol-based milling method, is more than 1 um. However, the powder size can be reduced to 100 nm by using the water-based milling method. In addition, the calcination temperature can be lowered 200 °C to get a pure phase by using the water-based milling method, compared to the alcohol-based milling method. The relative density of YSH ceramic materials can reach to 97.5% by conventional sintering at 1650 °C after during 10 h.

    Ladda ner fulltext (pdf)
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  • 47.
    Bu, Junfu
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jönsson, Pär
    Zhao, Zhe
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Preparation of Protonic Conductor BaZr0.5Ce0.3Ln0.2O3-δ (Ln = Y, Sm, Gd, Dy) by using a Solid State Reactive Sintering Method2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    A pure and well crystalized yttrium doped hafnium oxide Hf0.69Y0.31O2-δ (YSH) is obtained by using a modified solid state reaction method, where a water-based milling medium and freeze drying are implemented to reduce the agglomeration. The mean sizes of the YSH powder, which is obtained through a traditional alcohol-based milling method, is more than 1 um. However, the powder size can be reduced to 100 nm by using the water-based milling method. In addition, the calcination temperature can be lowered 200 ℃ to get a pure phase by using the water-based milling method, compared to the alcohol-based milling method. The relative density of YSH ceramic materials can reach to 97.5% by conventional sintering at 1650 ℃ after during 10 h.

    Ladda ner fulltext (pdf)
    fulltext
  • 48.
    Bu, Junfu
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Zhao, Zhe
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Transport properties of BaZr0.5Ce0.3Y0.2O3-δ proton conductor prepared by spark plasma sintering2016Ingår i: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 42, nr 3, s. 4393-4399Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 49.
    Bölke, Kristofer
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Ersson, Mikael
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Andersson, Nils A. I.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Imris, Matej
    ScanArc Plasma Technol AB, SE-81321 Hofors, Sweden..
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Experimental Determinations of Mixing Times in the IronArc Pilot Plant Process2019Ingår i: Metals, ISSN 2075-4701, Vol. 9, nr 1, artikel-id 101Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    IronArc is a newly developed technology and an emerging future process for pig iron production. The long-term goal with this technology is to reduce the CO2 emissions and energy consumption compared to existing technologies. The production rate of this process is dependent on the stirring, which was investigated in the pilot plant process by measuring the mixing time in the slag bath. Moreover, slag investigations were done both based on light optical microscope studies as well as by Thermo-Calc calculations in order to determine the phases of the slag during operation. This was done because the viscosity (which is another important parameter) is dependent on the liquid and solid fractions of the slag. The overall results show that it was possible to determine the mixing time by means of the addition of a tracer (MnO2 powder) to the slag. The mixing time for the trials showed that the slag was homogenized after seconds. For two of the trials, homogenization had already been reached in the second sample after tracer addition, which means <= 8 s. The phase analysis from the slag indicated that the slag is in a liquid state during the operation of the process.

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    Bölke, Kristofer
    et al.