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  • 301.
    Nordquist, Annie
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Iguchi, Manabu
    Yokota, Shinichiro
    Jonsson, Lage
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    A physical model study of swirl phenomena in a top blown bath2006In: Steel Research International, ISSN 1611-3683, Vol. 77, p. 234-241Article in journal (Refereed)
    Abstract [en]

    The present study is focused on swirl motion in a top blown water model, where a deep water swirl motion is observed. During the experiments, the top lance, with cylindrical nozzles, was placed above the water surface and thereby produced an external force on the bath. The effect on how different parameters, such as nozzle diameter and the distance between the bath surface and nozzle exit, i.e. the lance height, affect the swirl motion were studied. More specifically, the amplitude and period of the swirl as well as the starting and damping time of the swirl were determined. The amplitude was found to increase with an increased nozzle diameter and gas flow, while the period had a constant value of about 0.5 s for all nozzle diameters, gas flows and lance heights. The starting time for the swirl motion was found to decrease with an increased gas flow, while the damping time was found to be independent of gas flow rate, nozzle diameter, lance height and ratio of depth to diameter.

  • 302.
    Nordquist, Annie
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Kumbhat, Nitesh
    Jonsson, Lage
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    The effect of nozzle diameter, lance height and flow rate on penetration depth in a top-blown water model2006In: Steel Research International, ISSN 1611-3683, Vol. 77, p. 82-90Article in journal (Refereed)
    Abstract [en]

    This work aimed at investigating the penetration depth in a water model during lance blowing. A study of accessible literature was carried out to summarise previous work that had studied penetration depth. Based on the literature study an experimental plan was devised consisting of experiments focused on studying the effect of nozzle diameter, lance height and flow rate on the penetration depth. However, the primary focus was on studying the effect of small nozzle diameters on the penetration depth, which has not previously been reported in the literature. It was found that the results of the experiments in general agreed well with previous work, namely: the penetration depth increases with decreasing nozzle diameter, decreasing lance height and increasing gas flow rate. All equations known previously were used to calculate the penetration depth based on current experimental data. Thereafter, it was deduced which of the empirical relationships best fitted the experimental data. The jet momentum number was also determined from the experimental data and it was found that the penetration depth increased with an increased jet momentum number. However, for smaller nozzle diameters there was a considerable deviation. Therefore, a new correlation was suggested, heuristically derived from a macroscopic energy conservation consideration, and it was shown to result in better agreement between experiments and predictions for small nozzle diameters.

  • 303. Nordqvist, A.
    et al.
    Tilliander, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Gronlund, K.
    Runnsjo, G.
    Jonsson, P.
    Characterisation of metal droplets sampled during top lance blowing2009In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 36, no 6, p. 421-431Article in journal (Refereed)
    Abstract [en]

    Laboratory trials were performed in an induction furnace to study droplet formation during lance blowing. Oxygen was blown on a molten iron bath consisting of iron alloyed with carbon and silicon. Iron droplets were collected using a specially designed sampler. The average iron droplet composition and the oxide layer thickness were determined using scanning electron microscopy combined with energy dispersed spectroscopy. In addition, the concentration gradient of elements was determined using electron probe microanalysis. It should be noted that a special technique had to be developed in order to prepare the droplet sample. The size distribution and composition of the droplets were also determined using the microprobe. The carbon was found to be homogeneously distributed throughout the droplet independently of the size of the droplet. For the experiments using both carbon and silicon it was found that the silicon in most droplets could be found in the periphery of the droplets. It was also found that the tendency was that both the carbon content as well as the silicon content in the droplets decreased with a decreased droplet size. Thus, it was concluded that it is necessary to modify top blown decarburisation processes so that a maximum area between droplet and atmosphere is obtained.

  • 304.
    Nordqvist, Annie
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Tilliander, A.
    Grönlund, K.
    Runnsjö, Gunilla
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Characterization of metal droplets sampled during top lance blowing2006In: Sohn International Symposium Advanced Processing of Metals and Materials: Vol 2 - THERMO AND PHYSICOCHEMICAL PRINCIPLES, WARRENDALE: MINERALS, METALS & MATERIALS SOC , 2006, p. 351-362Conference paper (Refereed)
    Abstract [en]

    Laboratory trials were performed in an induction furnace to study droplet formation during lance blowing. Compressed air was blown on a molten iron bath consisting of iron alloyed with carbon and silicon. Steel droplets were collected using a specially designed sampler. The average steel droplet composition and the oxide layer thickness were determined using scanning electron microscopy combined with energy dispersed spectroscopy. In addition, the concentration gradient of elements was deter-mined using a microprobe. It should be noted that a special technique had to be developed in order to prepare the droplet sample. The size distribution and composition of the droplets was also determined using the microprobe. It was found that the carbon content in the droplets was lower than the carbon content in the bulk.

  • 305. Ono, Hideki
    et al.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Agawa, Shingo
    Ibuta, Toshio
    Maruo, Ryota
    Usui, Tateo
    Formation Conditions of Ti2O3, MgTi2O4, Mg2TiO4, and MgAl2O4 in Ti-Mg-Al Complex Deoxidation of Molten Iron2015In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 86, no 3, p. 241-251Article in journal (Refereed)
    Abstract [en]

    The relationships of the compounds in the Mg-Ti-Al-O system in equilibrium with molten iron are investigated at temperatures ranging from 1873 to 1973 K, and the thermodynamic calculations are conducted in avoiding Al2O3 or spinel MgAl2O4 formation and for inclusion control. The equilibrium relations between the compounds (Mg2TiO4, MgTi2O4, or MgAl2O4) and the composition of solutes in steel are clarified. The conditions are shown that the transformation of the stable compound from Mg-Ti spinel to Mg-Al spinel occurs at Mg contents ranging from 1 to 10 ppm by mass. It is also found, on the Mg-Ti spinel, the stable compound is transformed from inverse-spinel Mg2TiO4 to normal-spinel MgTi2O4 at Ti = about 60 ppm by mass. In addition, the stable compound is transformed from MgTi2O4 to Ti2O3 at Ti about 1000 ppm by mass.

  • 306. Ono, Hideki
    et al.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Ibuta, Toshio
    Usui, Tateo
    Equilibrium Relationship between the Oxide Compounds in MgO-Al2O3-Ti2O3 and Molten Iron at 1 873K2010In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 50, no 12, p. 1955-1958Article in journal (Refereed)
    Abstract [en]

    It is important to determine the equilibrium relationship between the oxide compounds in MgO-Al2O3-Ti2O3 and molten iron to avoid Al2O3 or MgO Al2O3 formation and for inclusion control In this study we investigated the formation conditions of MgTi2O4 in preference to MgAl2O4 at 1 873 K The phase stability regions of MgAl2O4 and MgAl2O4 or Ti2O3 were determined at 1 873 K in MgO-Al2O3-Ti2O3 At a low titanium content of less than 0 1 mass% and when [mass ppm Mg]=3 MgAl2O4 forms at more than [massc%Al]=0 08 and the region of MgAl2O4 formation widens as the titanium content of the molten iron decreases Accordingly it is necessary to lower the Al content and to adjust the Ti content to an appropriate concentration range to form MgTi2O4 instead of MgAl2O4

  • 307. Ono, Hideki
    et al.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Maruo, Ryota
    Agawa, Shingo
    Usui, Tateo
    Formation Conditions of Mg2TiO4 and MgAl2O4 in Ti-Mg-Al Complex Deoxidation of Molten Iron2009In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 49, no 7, p. 957-964Article in journal (Refereed)
    Abstract [en]

    It is important to study the complex deoxidation equilibrium of molten iron in Ti-Mg-Al system from the view point of inclusion control. The equilibrium experiments between molten iron and TiOx-MgO-Al2O3 slag and the thermodynamic calculation on the complex deoxidation are conducted at 1973 K in the present study. The liquid phase region of TiOx-MgO-Al2O3 system in equilibrium with molten iron is clarified at 1973 K. The equilibrium compounds which are coexisted with the slag on the liquidus curve in the system are identified to be Mg2TiO4, and MgAl2O4. The equilibrium relation between the deoxidation products (Mg2TiO4 or MgAl2O4) and the composition of solute elements in steel is investigated, and the conditions that Mg2TiO4 forms instead of MgAl2O4 nor Al2O3 are examined in the complex deoxidation of Ti-Mg-Al system. When the aluminum content of molten iron is under 4 mass ppm, Mg2TiO4 forms over the wide concentration range. The concentration range of MgAl2O4 formation widens as the aluminum content of molten iron increases. It is necessary to increase Mg content and to decrease Al content in order to form Mg2TiO4 in the Ti-Mg-Al complex deoxidation of molten iron in the range Ti<0.01 mass%. However, it is difficult in the range of Ti>0.01 mass% to form Mg2TiO4.

  • 308.
    Pal, Mayur
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Modeling of induction stirred ladles2012Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Over the years numerous computational fluid dynamics models have been developed in order to study the fluid flow in gas and induction stirred ladles. These models are used to gain insight in the industrial processes used in ladle treatment of steel. A unified model of an induction stirred Ladle in two and three dimensions is presented. Induction stirring of molten steel is a coupled multi-physics phenomena involving electromagnetic and fluid flow. Models presented in this thesis gives a more accurate description of the real stirring conditions and flow pattern, by taking into account the multi-physics behavior of the induction stirring process in an induction stirred ladle. This thesis presents a formulation of coupled electromagnetic and fluid flow equations. The coupled electromagnetic and fluid flow equations are solved using the finite element method in two and three-dimensions. The simulation model is used to predict values of steel velocities and magnetic flux density. The simulation model is also used to predict the effect of increased current density on flow velocity. Magnetic flux density values obtained from the model are verified against experimental values.

     

  • 309.
    Pal, Mayur
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Eriksson, Robert
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    A computational fluid dynamics model of a 20Kg induction stirred laboratory scaled ladle2005In: Proceedings of the COMSOL Multiphysics User´s Conference 2005 Stockholm, 2005Conference paper (Refereed)
    Abstract [en]

    Over the years numerous Computational fluid dynamics models [1,2,3,4,5,6,7,8] have been developed, in order to study the fluid flow in gas and induction stirred ladles. These models were used to gain more insight in the industrial processes used in ladle treatment of steel. In this paper a computational fluid dynamics model of a 20 Kg laboratory scaled induction ladle (Situated at the Dept. of Material Science and Engineering - KTH) is presented. This particular laboratory furnace can be equipped with an electromagnetic stirrer, which can be used to agitate the steel melt. The CFD model so developed will make it feasible to have information about the fluid flow in this particular laboratory furnace. This information would promote the analysis of experimental results and the implementation of new strategies. The objective of this paper is to obtain an understanding and insight of the ladle refining process by solving the electromagnetic force field and predict the flow pattern produced by these force fields using a single straight induction stirrer, with the help of 20Kg laboratory scaled furnace. The size of this 20Kg laboratory scaled furnace is very small compared to the size of electromagnetic stirrer because of which the magnetic field inside the ladle will essentially be two dimensional. The magnetic field component in third dimension (Y-direction) is very small compared to other two (X and Z direction) hence a two dimensional model also provides a better understating of the model. The flow field produced by a straight induction stirrer is of complex nature due to the three dimensional electromagnetic force and the flow phenomenon. In order to provide more information about the stirring of molten steel within the ladle, which is essentially a three-dimensional phenomenon, a three-dimensional model is also presented incorporating equations governing the fluid flow as well as the electromagnetic forces in the system. Both the models two and three – dimensional are developed in two parts. First, the calculation of electromagnetic forces, which is done with the help of FEMLAB3.1 and second, using these electromagnetic forces (Lorenz forces) as the source term for solving incompressible Navier stokes equation to compute the velocity profile of the agitated melt, which is done by combining the Electromagnetic module with Chemical Engineering module of commercial software FEMLAB 3.1. The CFD model so developed is verified using experimental measurements of the magnetic flux in the laboratory furnace. This CFD model of the induction ladle is developed with the possible extension of the model in mind, i.e. it should be easy to expand the model to incorporate temperature as well as transport of chemical species and non – metallic inclusions.

  • 310.
    Pal, Mayur
    et al.
    Carbonate Research Shell International Exploration and Production, Rijswijk, Netherlands.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Multiphysics modeling of an induction-stirred ladle in two and three dimensions2012In: International Journal for Numerical Methods in Fluids, ISSN 0271-2091, E-ISSN 1097-0363, Vol. 70, no 11, p. 1378-1392Article in journal (Refereed)
    Abstract [en]

    A unified model of an induction-stirred ladle in two and three dimensions is presented. Induction stirring of molten steel is a coupled multiphysics phenomena involving electromagnetic and fluid flow. Models presented in this paper gives a more accurate description of the real stirring conditions and flow pattern by taking into account the multiphysics behavior of the induction-stirring process in an induction-stirred ladle. This paper presents formulation of coupled electromagnetic and fluid flow equations. The coupled electromagnetic and fluid flow equations are solved with the use of the finite element method in two and three dimensions. The model is used to predict values of steel velocities and magnetic flux density. The model is also used to predict the effect of increased current density on flow velocity. Magnetic flux density values obtained from the model are verified against the experimental values.

  • 311.
    Pal, Mayur
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Kholmatov, Shavkat
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Numerical simulation of induction stirred ladle2006In: Proceedings of the COMSOL User´s Conference 2006 Birmingham, 2006Conference paper (Refereed)
    Abstract [en]

    Induction ladle plays an important role in a broad range of metal-processing operations. The treatment of steel in the ladle is as old as the use of ladles in steelmaking. The main purpose for ladle treatment of hot metal and liquid steel include desulphurization, deoxidation, alloying, and inclusion shape control. Over last few years efforts are made to develop simulation models of induction ladle [1]-[8], in order to study heat transfer and fluid flow in gas and induction stirred ladles. These models provide more information about the industrial processes used in ladle treatment of steel. In this paper a simulation model of a laboratory scaled induction ladle is presented. The simulation model so developed will make it feasible to have information about the fluid flow phenomenon and thermal heat transfer. In order to perform the numerical simulation of the furnace, physical processes involved are expressed as a coupled-nonlinear system of partial differential equations arising from a thermal-magneto-hydrodynamic problem. The simulation model is formulated in a twodimensional domain. The equations of electromagnetic model to describe magnetic diffusion inside the ladle through magnetic stirrer are expressed by well known system of Maxwell’s equations. Moreover, the heat equations governing the induction heating are provided. The hydrodynamic model for fluid flow in the molten metal is described by wellknown incompressible Navier-Stokes equation.Numerical simulation are performed by solving the coupled system of equations using the commercial software COMSOL Multiphysics® application mode by combining Electromagnetics, Fluid Dynamics and Heat transfer modules.

     

  • 312.
    Persson, Fredrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    A Study of Factors Affecting the Particle Size for Water Atomised Metal Powders2012Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The production of metal powders by water atomisation is a well established process, which can be used to produce a wide range of particle sizes. A careful control of the particle size distribution is necessary, to atomise powders with a high quality and at a low production cost. Therefore, it is necessary to have a substantial knowledge of the relation between operational parameters and the particle size, to be able to produce water atomised metal powders with consistent and high yields.

    The main purpose with this thesis was to increase the knowledge about factors which affect the mass median particle size (d50) for water atomised metal powders. The specific objectives with the study were to develop a theoretical d50 model and to investigate the relation between the particle size and the physical properties of the liquid metal.

    Pilot scale experiments for liquid iron showed that alloy additions of carbon and sulphur decreased the d50 value, at a maintained liquid steel temperature before atomisation. Moreover, it was indicated that the reduced particle size at increased %C and %S contents may be related to a decreased viscosity and surface tension of the liquid metal, respectively. An alternative explanation could be that raised superheats at increased carbon contents increased the total available time for atomisation, which may have contributed to a reduction of the d50 value.

    The theoretical d50 model developed in this work showed a very good correlation to the current experimental data. The model considers the influence of surface tension, viscosity, melt stream diameter, water pressure, water jet angle and water to metal ratio. This model was further used to analyse how the d50 value was influenced by the viscosity and the surface tension. A reduced viscosity from 4∙9 to 2∙1 mPa s decreased the d50 value with 33%. In addition, the particle size was estimated to decrease with 21% by decreasing the surface tension from 1840 to 900 mN m-1.

  • 313.
    Persson, Fredrik
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Eliasson, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Prediction of particle size for water atomised metal powders: parameter study2012In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 55, no 1, p. 45-53Article in journal (Refereed)
    Abstract [en]

    This work aims to investigate how some significant atomising parameters influence the mass median particle size d50 of water atomised metal powders. More specifically, these were water pressure, melt flowrate, water jet angle, liquid metal viscosity and surface tension. Existing models for the prediction of d50 during water atomisation were reviewed. The selected models were fitted and compared with atomising experiments of liquid iron containing 0.5–4.4%C. Experimental results and model calculations were used in a parameter study to investigate how the different parameters influenced d50. The effect on d50 was large for the water pressure, medium for the viscosity and low for the melt flowrate and surface tension. Model calculations indicate that the jet angle has a large effect on d50, which should be verified by additional studies. The model proposed by Bergquist (B. Bergquist: Powder Metall., 1999, 42, 331–343) showed the best agreement with the current experimental data.

  • 314. Persson, Fredrik
    et al.
    Eliasson, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Oxidation of Water Atomized Metal Powders2014In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 85, no 12, p. 1629-1638Article in journal (Refereed)
    Abstract [en]

    This study focuses on the oxidation of water atomized metal powders. Pilot plant experiments were performed using liquid iron alloyed with manganese and carbon. The powder particle shape and the oxides were determined using optical and scanning electron microscopy with energy dispersive X-ray microanalysis. The oxygen in the atomized powders was mainly present as thin surface oxide layers, which were determined to increase from 10 to 40-60 nm, at increased particle sizes from 10 to 750 mu m. In addition, manganese oxides were observed to be unevenly distributed at the surface of several particles for iron powders alloyed with 0.3mass% Mn. Experimental data indicated that between 10 and 20% of the manganese was present as oxides in the powders. However, equilibrium calculations predicted a strong driving force for oxidation of manganese. More specifically, it was estimated that only 4% of the initial manganese content remained in the final atomized powders.

  • 315. Persson, Fredrik
    et al.
    Eliasson, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär Göran
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Influence of liquid metal properties on water atomised iron powders2012In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 52, no 12, p. 2130-2138Article in journal (Refereed)
    Abstract [en]

    The main focus of the present study was the influence of liquid metal properties on the particle size during water atomisation. Experiments for liquid iron showed that alloy additions of carbon and sulphur decreased the particle size. Moreover, it was indicated that the reduced d50 value at increased %C and %S contents may be related to a decreased viscosity and surface tension respectively. An alternative mechanism could be that raised superheats at increased carbon contents increased the total available time for atomisation. This may also have decreased the particle size. The influence of surface tension and viscosity on the d50 value was further analysed with a theoretical d50 model proposed in a previous work. A reduced viscosity from 6.8 to 4.3 mPa s decreased the d50 value with 33%. In addition, the particle size was estimated to decrease with 27% by decreasing the surface tension from 1 850 to 900 mN m-1.

  • 316.
    Persson, Fredrik
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär G
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Eliasson, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Influence of liquid metal properties for water atomised metal powders2012Manuscript (preprint) (Other academic)
    Abstract [en]

    The main focus of the present study was the influence of liquid metal properties on the particle size during water atomisation. Experiments for liquid iron showed that alloy additions of carbon and sulphur decreased the particle size. Moreover, it was indicated that the reduced d50 value at increased %C and %S may be related to a decreased viscosity and surface tension respectively. An alternative mechanism could be that raised superheats at increased carbon contents increased the total available time for atomisation. This may also have decreased the particle size. The influence of surface tension and viscosity on the d50 value was further analysed with a theoretical d50 model proposed in a previous work. A reduced viscosity from 4∙9 to 2∙1 mPa s decreased the d50 value with 33%. In addition, the particle size was estimated to decrease with 21% by decreasing the surface tension from 1840 to 900 mN m-1.

  • 317.
    Pirouznia, Pouyan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Processing. Dalarna Univ, Dept Mat Sci & Engn, SE-79188 Falun, Sweden.;Voestalpine Precis Strip AB, Res & Dev Dept, SE-68428 Munkfors, Sweden..
    Andersson, Nils A. I.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy. KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Processing.
    Tilliander, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy. KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Processing.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Processing.
    The Impact of the Gas Inlet Position, Flow Rate, and Strip Velocity on the Temperature Distribution of a Stainless-Steel Strips during the Hardening Process2019In: METALS, ISSN 2075-4701, Vol. 9, no 9, article id 928Article in journal (Refereed)
    Abstract [en]

    A non-uniform temperature across the width of martensitic stainless-steel strips is considered to be one of the main reasons why the strip exhibits un-flatness defects during the hardening process. Therefore, the effect of the gas inlet position in this process, on the temperature distribution of the steel strip was investigated numerically. Furthermore, an infrared thermal imaging camera was used to compare the model predictions and the actual process data. The results showed that the temperature difference across the width of the strip decreased by 9% and 14% relative to the calculated temperature and measured values, respectively, when the gas inlet position was changed. This temperature investigation was performed at a position about 63 mm from the bath interface. Moreover, a more symmetrical temperature distribution was observed across the width of the strip. In addition, this study showed that by increasing the amount of the hydrogen flow rate by 2 Nm(3)/h, a 20% reduction of temperature difference across the width of strip was predicted. Meanwhile, the results show that the effect of the strip velocity on the strip temperature is very small.

  • 318.
    Pirouznia, Pouyan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Andersson, Nils
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Tilliander, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Jönsson, Pär Göran
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    A mathematical model of martempering of thin martensitic stainless steel strips2015In: Proceedings of the 6th International Congress on the Science and Technology of Steelmaking, ICS 2015, Chinese Society for Metals , 2015, p. 1027-1030Conference paper (Refereed)
    Abstract [en]

    The martempering process produces thin martensitic stainless steel strips and is widely used for production of valve- and spring steel. Industrial trials were conducted in collaboration with Böhler Uddeholm Precision Strip, Munkfors, Sweden. These trials suggested that the quenching step is critical to control, in order to reduce uneven temperature gradients which will lead to distortions or unevenness. To investigate this, computational modelling of the temperature was performed to estimate the current situation for the conventional martempering process based on physical theories together with Comsol Multiphysics and using a steady state modeling approach. The model boundary conditions were based upon temperature measurements in the real process. Furthermore, the strip was modelled as it comes out of the heating furnace, which is filled with hydrogen gas and continues into a molten lead-bismuth bath for quenching. Thus, the temperature profile was obtained for the strip as well as its surroundings; The results show that a better insight of the martempering line could be achieved. The model results can be used to investigate disturbances in the normal operation. Furthermore, the temperature profiles can be used to optimize the process and possibly to reduce the energy consumption.

  • 319.
    Rahaman, Moshiour
    et al.
    Ferritico, Brinellvagen 85, S-10044 Stockholm, Sweden..
    Mu, Wangzhong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Odqvist, Joakim
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy. Ferritico, Brinellvägen 85, S-10044 Stockholm, Sweden.
    Hedström, Peter
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Ferritico, Brinellvägen 85, S-10044 Stockholm, Sweden.
    Machine Learning to Predict the Martensite Start Temperature in Steels2019In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 50A, no 5, p. 2081-2091Article in journal (Refereed)
    Abstract [en]

    The martensite start temperature (M-s) is a critical parameter when designing high-performance steels and their heat treatments. It has, therefore, attracted significant interest over the years. Numerous methodologies, such as thermodynamics-based, linear regression and artificial neural network (ANN) modeling, have been applied. The application of data-driven approaches, such as ANN modeling, or the wider concept of machine learning (ML), have shown limited technical applicability, but considering that these methods have made significant progress lately and that materials data are becoming more accessible, a new attempt at data-driven predictions of the M-s is timely. We here investigate the usage of ML to predict the M-s of steels based on their chemical composition. A database of the M(s)vs alloy composition containing 2277 unique entries is collected. It is ensured that all alloys are fully austenitic at the given austenitization temperature by thermodynamic calculations. The ML modeling is performed using four different ensemble methods and ANN. Train-test split series are used to evaluate the five models, and it is found that all four ensemble methods outperform the ANN on the current dataset. The reason is that the ensemble methods perform better for the rather small dataset used in the present work. Thereafter, a validation dataset of 115 M-s entries is collected from a new reference and the final ML model is benchmarked vs a recent thermodynamics-based model from the literature. The ML model provides excellent predictions on the validation dataset with a root-mean-square error of 18, which is slightly better than the thermodynamics-based model. The results on the validation dataset indicate the technical usefulness of the ML model to predict the M-s in steels for design and optimization of alloys and heat treatments. Furthermore, the agility of the ML model indicates its advantage over thermodynamics-based models for M-s predictions in complex multicomponent steels. (C) The Author(s) 2019

  • 320.
    Roos, Erik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    A study of Factors Influencing Nozzle Clogging of Special Steel Grades during Continuous Casting2014Licentiate thesis, comprehensive summary (Other academic)
  • 321.
    Roos, Erik
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Karasev, Andrey
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    An Experimental and Thermodynamic Study of Non-Metallic Inclusions in High Si Stainless Steels Regarding Clogging During Casting2014In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 85, no 10, p. 1410-1417Article in journal (Refereed)
    Abstract [en]

    Clogging of high Si-containing stainless steel grades was studied by metallographic examinations of steel samples from clogged and non-clogged heats as well as by thermodynamic modeling using Thermo-Calc and FactSage. Morphology, composition, number and size of inclusions and clusters in the steel samples were determined on a polished surface of the steel samples by using a scanning electron microscope equipped with energy-dispersive X-ray spectrometer. The results showed that the content of Al in ferroalloys added during ladle treatment should be controlled to avoid a formation of spinel MgO-Al2O3 inclusions in liquid steel and a resulting clogging during casting. The thermodynamic calculations showed that the Al content in a melt during ladle treatment and casting should not be larger than 0.003% to obtain < 1% of MgO-Al2O3 inclusions in the liquid steel for a 1.9% silicon content. Moreover, calculations also showed that if the Si content increased from 1.9% (non-clogging heats) to 2.65% (clogging heats), the number of MgO-Al2O3 inclusions decreased slightly. Moreover, it was found that an increased amount of FeSi additions for correction of Si content in the melt increase the Al content. As a result, the number of spinels and clusters increases, which is the primary cause for clogging during casting of these steel grades.

  • 322.
    Roos, Erik
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Karasev, Andrey
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär Goran
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Effect of Si and Ce Contents on the Nozzle Clogging in a REM Alloyed Stainless Steel2015In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 86, no 11, p. 1279-1288Article in journal (Refereed)
    Abstract [en]

    The influence of the cerium and silicon contents on the castability of a REM-alloyed stainless steel was investigated by using pilot scale experiments. The trials were carried out with three different silicon concentrations: i) low (LSi; Si < 0.5%); ii) middle (MSi; Si approximate to 0.8-1.4%); and iii) high (HSi; Si approximate to 1.5-1.9%). During the casting, the liquid steel was teemed out through a zirconia nozzle located at the bottom of the furnace. The results showed that the nozzle clogging did drastically increase with increasing concentrations of Si and Ce up to levels larger than the critical contents (>= 1.5% Si and >= 0.05% Ce) in the cast HSi steel. In addition, the Ce content in a cast steel was found to increase linearly with an increased concentration of Si, due to the determinant effect of the Si content on an initial content of O in the melt before an addition of mischmetal. Finally, it was found that the concentration of insoluble Ce (Ce-insol.) determines the amount of inclusions and clusters in steel samples. Overall, soluble Ce concentrations larger than 250 ppm were found to be an important reason for fast nozzle clogging during casting.

  • 323.
    Sadat, Elaheh Sadat
    et al.
    Amirkabir Univ Technol, Elect Engn Dept, Tehran 158754413, Iran.
    Faez, Karim
    Amirkabir Univ Technol, Elect Engn Dept, Tehran 158754413, Iran.
    Saffari Pour, Mohsen
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology. KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy. Sharif Univ Technol, Dept Mech Engn, Tehran 1458889694, Iran.
    Entropy-Based Video Steganalysis of Motion Vectors2018In: Entropy, ISSN 1099-4300, E-ISSN 1099-4300, Vol. 20, no 4, article id 244Article in journal (Refereed)
    Abstract [en]

    In this paper, a new method is proposed for motion vector steganalysis using the entropy value and its combination with the features of the optimized motion vector. In this method, the entropy of blocks is calculated to determine their texture and the precision of their motion vectors. Then, by using a fuzzy cluster, the blocks are clustered into the blocks with high and low texture, while the membership function of each block to a high texture class indicates the texture of that block. These membership functions are used to weight the effective features that are extracted by reconstructing the motion estimation equations. Characteristics of the results indicate that the use of entropy and the irregularity of each block increases the precision of the final video classification into cover and stego classes.

  • 324.
    Safavi Nick, Reza
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Mathematical Model of the Solid Flow Behavior in a Real Dimension Blast Furnace2012Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    A mathematical model based on the continuum mechanic concept has been developed to describe the profile of solid particles in an industrial scale blast furnace. The focus is the in-furnace conditions and its characteristics such as the shape and size of the deadman. The Navier-Stokes differential equation for multi-phase multi-dimensional space has been used to describe the behavior of existing phases. The equation has been modified to make it possible to describe the dual nature of the solid phase in the system. This has been done by applying the concept of the solid surface stress to describe the intergranular surface interactions between particles. More specifically, this term is added as an extra term to the Navier-Stokes equation to describe the particle-particle interactions. This extra term in behave as a breaking force when the particles are sliding down in the furnace. During the descending movement in the furnace it is shown that the particles change their profile from a V-shape to a Wshape, due to the characteristics of the deadman. Moreover, the velocity magnitude is higher at the outer surface of the deadman for higher grid-slabs in this region than the near-wall cells. However, the situation changes as solid particles moving to even lower levels of the grid-slabs at the outer surface of the deadman in comparison to near-wall cells. It has also been shown that an increase in the magnitude of the effective pressure reduces the velocity magnitude of descending particles. Furthermore, since different phases co-exist in a blast furnace, the volume fraction plays an important role in the blast furnace. Therefore, the influence of three different packing densities (0.68, 0.71 and 0.74 respectively) on the profile of the flow through the upper part of the blast furnace from the throat to the tuyeres level has been studied. It is shown that an increase in the volume fraction of the solid phase lead to a decrease in the velocity magnitude. This decrease is due to an increase in the solid volume fraction, which will increase the resident time of the particles inside a blast furnace. In addition, it is shown that the velocity magnitude of the solid phase decreases from the throat to the belly of the furnace, for the studied conditions. However, after belly the velocity magnitude increases again.

  • 325.
    Safavi Nick, Reza
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Tilliander, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jonsson, Lage T. I.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    A mathematical model of the solid flow behavior in a real dimension blast furnace: Effects of the solid volume fraction on the velocity profile2013In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 84, no 10, p. 999-1010Article in journal (Refereed)
    Abstract [en]

    A mathematical model based on the continuum mechanic concept has been developed to describe the profile of solid particles in a blast furnace with respect to the in-furnace conditions and characteristics, e.g., the shape and size of the deadman. The Navier-Stokes differential equation for multi-phase multi-dimensional space has been used to describe the behavior of existing phases. The equation has been modified to make it possible to describe the dual nature of the solid phase in the system by applying the concept of the solid surface stress to characterize the inter-granular surface interactions between particles. Since different phases co-exist in a blast furnace, the volume fraction plays an important role in a blast furnace. Therefore, the influence of three different packing densities (0.68, 0.71, and 0.74, respectively) on the profile of the flow in the upper part of a furnace down to the tuyeres level has been studied. It is shown that an increase in the volume fraction of the solid phase lead to a decrease in magnitude of the velocity. The decrease in the magnitude of the velocity due to an increase in the solid volume fraction will increase the resident time of the particles inside a blast furnace. In addition, it is shown that the solid phase velocity magnitude decreases from the throat to the belly of the furnace for the studied conditions. However, after belly the velocity magnitude increases.

  • 326.
    Safavi Nick, Reza
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Tilliander, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jonsson, Lage T. I.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Effect of Particle Properties on the Solid Flow Profile in a Blast Furnace2009In: Journal of Iron and Steel Research International, ISSN 1006-706X, E-ISSN 2210-3988, Vol. 16, no Part 2 Suppl. 2, p. 1112-1115Article in journal (Refereed)
    Abstract [en]

    An ironmaking blast furnace is one of the most complex reactors working with a multiphase flow involving gas, liquid and solid. The solid phase is the most important phase among these three phases. Consequently, investigating the velocity profile of solid particles as a primary phase in the blast furnace is one of the major research focus during the last decay. Since the major outbreak of computer development during the last twenty years, mathematical modeling and numerical Solution plays an important role in the engineering development. Therefore, the solid particle behavior is modeled based on general conservation laws to investigate the profile of solid particles. The different properties of solid particles have different effect on the velocity profile of solid particles. Therefore, in this article, the effect of particle properties such as diameter, viscosity, density and volume fraction. on velocity profile of solid particles and blast furnace operation has been studied and reported.

  • 327.
    Safavi Nick, Reza
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Tilliander, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jonsson, Tord Lage Ingemar
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär Göran
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Mathematical Model of Solid Flow Behavior in a Real Dimension Blast Furnace2013In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 53, no 6, p. 979-987Article in journal (Refereed)
    Abstract [en]

    A mathematical model based on the continuum mechanic concept has been developed to describe the profile of solid particles in an industrial scale blast furnace with respect to the in-furnace conditions and its characteristics such as the shape and size of the deadman. The Navier-Stokes differential equation for multi-phase multi-dimensional space has been used to describe the behavior of existing phases. The surface stress tensor has been defined as an extra term and added to the Navier-Stokes equation to describe the particle-particle interactions. This extra term in the Navier-Stokes equation behave as a breaking force when the particles are sliding down. It is shown that the particles change their profile from a V-shape to a W-shape due to the characteristics of the deadman. Moreover, the velocity magnitude is higher at the outer surface of the deadman for higher grid-slabs in this region than the near-wall cells. However, the situation changes as solid particles moving to even lower level of grid-slabs at the outer surface of the deadman in comparison to near-wall cells. It has also been shown that an increase in the magnitude of the effective pressure reduces the velocity magnitude of descending particles.

  • 328.
    Samuelsson, Peter
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Ternstedt, Patrik
    Tilliander, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Appell, Anders
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Use of Physical Modelling to Study How to Increase the Production Capacity by Implementing a Novel Oblong AOD Converter2017In: Ironmaking and Steelmaking: Processes, Products and ApplicationsArticle in journal (Refereed)
    Abstract [en]

    There is no known example of an AOD converter with oblong cross sections in the literature. Changing the geometry of the converter vessel, from the traditional circular cross sections, to increase converter volume could potentially influence the performance of the converter and in particular the decarburisation rate. Due to physical limitations in an existing melt shop the only available way to increase the tapped weight and hence the productivity was to consider a modified converter cross section, namely an oblong cross section. A change in cross section could potentially influence the decarburisation performance and in the worst case counteract the intended increase in productivity. In order to study the feasibility of implementing an oblong converter, physical modelling was used to establish whether it would be suitable to change the AOD geometry from a circular cross section to a novel oblong cross section to increase the converter volume and thus the productivity. Specifically, the aim was to use physical modelling to study the fluid flow of the proposed converter configuration (geometry and number of tuyeres) and the potential influence on the decarburisation rate. Two water models linearly scaled down to a 1:4.6 dimension in comparison to a production converter were employed using water containing 𝑁𝑎𝑂𝐻 and gas injected through six or eight tuyeres as fluids. In the model one tuyere was used for injection of 𝐶𝑂2 gas, while air was injected through the remaining five or seven tuyeres. The reaction of 𝐶𝑂2 and 𝑁𝑎𝑂𝐻 (𝐶𝑂2 + 2𝑁𝑎𝑂𝐻 ⇄ 𝑁𝑎&𝐶𝑂3 + 𝐻2𝑂) was indirectly measured by detecting the pH value of the water in the model. The purpose of the model was to simulate the decarburisation part of the converter process as any prolongation of the decarburisation will defeat the purpose of increasing the productivity. The mixing time is considered to be a good indicator of the decarburisation as the kinetics will be diffusion controlled in the latter parts of the process. According to our experience, the thermodynamics of decarburisation will not be dependent on the converter shape. The following three converter figurations were studied: i) a circular converter with six tuyeres, ii) an oblong converter with six tuyeres, and iii) an oblong converter with eight tuyeres. The mixing time, defined as the time to reach 95% of the final 𝐶𝑂2 concentration, can be used to evaluate the different converter configurations. The average 𝐶𝑂2 concentrations based on several experiments, calculated based on pH measurements in the water, differed by less than 5% between the circular and oblong models after 165 s of injection of air and 𝐶𝑂2. The results also showed that no difference in mixing time could be found when using 6 and 8 tuyeres, respectively in the oblong model. In fact, the 𝐶𝑂2 concentrations in the oblong model differed by less than 2% after 165 s of injection of air and 𝐶𝑂2 between six and eight tuyeres. Based on the findings, it has been observed that the influence of converter geometry on mixing time is small, it was concluded that decarburisation rate is likely to be the same irrespectively of converter geometry. Thus it is possible to construct an oblong converter to increase the productivity.

  • 329.
    Sarma, Darbha Subraanranya
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Karasev, Andrey
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    On the Role of Non-metallic Inclusions in the Nucleation of Acicular Ferrite in Steels2009In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 49, no 7, p. 1063-1074Article in journal (Refereed)
    Abstract [en]

    The effects of non-metallic inclusions in nucleating acicular ferrite in steels during cooling from a weld or cooling from an austenitic temperature are reviewed. The influence of the acicular ferrite (AF) structure on mechanical properties of steels such as strength and toughness is briefly mentioned. The different factors affecting the formation of acicular ferrite, such as the soluble content of alloying elements in steel, cooling rate from austenitizing temperature, austenite grain size and inclusion characteristics in steel, are discussed. The mechanisms of acicular ferrite formation on non-metallic inclusions, such as reduction of interfacial energy, mismatch strain between the inclusion and ferrite/austenite, thermal strains at the inclusions and changes in matrix composition near the inclusions are also discussed. Finally, the effects of inclusion characteristics, such as size, number and composition are described and their effectiveness in nucleating acicular ferrite is discussed.

  • 330.
    Schmidt, Christoffer
    et al.
    KTH.
    Andersson, Nils A. I.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Tilliander, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Processing.
    Ljungqvist, P.
    Measurement techniques for meltdown control in a stainless steel AC electric arc furnace2017In: ESSC and DUPLEX 2017 - 9th European Stainless Steel Conference - Science and Market and 5th European Duplex Stainless Steel Conference and Exhibition, Associazione Italiana di Metallurgia , 2017Conference paper (Refereed)
    Abstract [en]

    A method for vibrational evaluations of spectrogram data from pilot plant measurements was established for obtaining a consistent analysis of the molten scrap state. Not knowing the meltdown progress inside the furnace results in an inefficient power scheduling, which affects refractory life, process time and energy losses. Hence, there exists potential to control the furnace power so that it is kept high while there is sufficient amounts of scrap inside furnace to absorb the input energy. Thus, harmonic distortions of the electric current and measurements of the sound and vibrations emitted from the furnace were correlated to the molten state of the scrap. By using this method, a reduction in melting time in the order of minutes per heat can be obtained. The method was found to give stable signals and it was judged to be a good candidate for implementation in industry. Furthermore, the developed method is universal and may be applied for other types of signals and combined into intelligent soft sensor systems. 

  • 331.
    Schmidt, Christoffer
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Andersson, Nils Å. I.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Ljungqvist, P.
    Tilliander, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Estimation of the molten state of scrap in an electric arc furnace by vibration measurements2015In: Proceedings of the 6th International Congress on the Science and Technology of Steelmaking, ICS 2015, Chinese Society for Metals , 2015, p. 279-282Conference paper (Refereed)
    Abstract [en]

    Knowing molten state of the scrap in the electric arc furnace is very important for process control. Because of the harsh environment of the furnace new measurement techniques must be developed to measure the molten state. This paper looks at vibrations emitted from the furnace with the use of accelerometers, looking for correlations with the molten state. It was found that 87% of the heats have increasing vibrations with the respect to time. Also, 47% of the heats have a coefficient of determination (R2) of more than 0.5 between vibrations and time. Further evaluation must be conducted to see if this can be related to the scrap content in the furnace.

  • 332.
    Sheng, D.Y.
    et al.
    Westinghouse Electric Sweden.
    Söder, Mats
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, Superseded Departments, Applied Process Metallurgy.
    Jonsson, Lage
    KTH, Superseded Departments, Applied Process Metallurgy.
    Recent Efforts in Sweden to Study InclusionCharacteristics During Ladle Refining2000In: ISBN91-7170-606-2, Trita Met 85 June 2000, Stockholm- Helsinki, 2000Conference paper (Refereed)
  • 333. Shibata, Hiroyuki
    et al.
    Watanabe, Yusuke
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Kitamura, Shin-ya
    Degree of Undercooling and Contact Angle of Pure Iron at 1 933 K on Single-crystal Al2O3, MgO, and MgAl2O4 under Argon Atmosphere with Controlled Oxygen Partial Pressure2009In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 49, no 7, p. 985-991Article in journal (Refereed)
    Abstract [en]

    Solid or molten oxides are considered to act as nucleation sites during continuous steel casting. The influence of the kind of oxide crystal and atmospheric oxygen partial pressure on the degree of undercooling and contact angle of pure molten iron on oxide substrates was measured by the sessile drop method. On Al2O3 and MgAl2O4 substrates, we found that the change in the degree of undercooling was dependent on the existence of a reaction layer and its thickness. On an MgO substrate, since no reaction layer formed, the degree of undercooling was small and was governed by the lattice misfit parameter. The equilibrium contact angle of a molten iron drop on the FeAl2O4 layer formed between the Al2O3 substrate and drop was about 100 degrees; a similar contact angle was obtained on MgAl2O4. The contact angle on MgO changed during observation due to the evaporation of Mg.

  • 334. Solhed, Henrik
    et al.
    Jonsson, Lage
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    A theoretical and experimental study of continuous-casting tundishes focusing on slag-steel interaction2002In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 33, no 2, p. 173-185Article in journal (Refereed)
    Abstract [en]

    A model of a tundish has been developed that takes into account the steel, slag, and refractory phases, Predicted temperatures and velocities in the steel and refractory from the model were earlier found to agree well with measured velocities and temperatures. The model was also used to determine the optimal location of flow devices, making the temperature distribution in the steel more even and enhancing the removal of inclusions to the slag. In this study, the focus was on using the model to study the slag/steel interface in the tundish. Predictions showed that slag is dispersed into the steel close to the interface as well as close to the ladle shroud. In order to confirm these predictions. the momentary interfacial solidification sampling (MISS) method was developed. Using this method, a sample of the steel/slag interface could be taken that represented almost an instantaneous picture of the interface. The MISS sampler was used for sampling low-carbon steel in the tundish. Samples were analyzed using ultrasonic testing, optical microscopy, and scanning electron microscopy (SEM). Analysis results confirmed the presence of nonmetallic particles close to the slag/steel interface and close to the ladle shroud, as suggested by the modeling results. The analyses also showed that the slag/steel interface is very irregular, despite the low velocities.

  • 335. Solhed, Henrik
    et al.
    Jonsson, Lage
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Modeling of the Steel/Slag Interface in a Continuous Casting Tundish2006In: Int. Symp. On Advanced Fluid/Solid Science andTechnology in Experimental Mechanics, Sapporo, 2006, p. 381-Conference paper (Refereed)
  • 336.
    Solhed, Henrik
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jonsson, Lage
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Modelling of the steel/slag interface in a continuous casting tundish2008In: Steel Research International, ISSN 1611-3683, Vol. 79, no 5, p. 348-357Article in journal (Refereed)
    Abstract [en]

    It is very important to understand the underlying physical phenomena at the steel/slag interface in a continuous casting tundish in order to control reoxidation and deoxidation phenomena that can occur. Aiming to investigate probable sources of exogenous inclusions originating from the covering slag, an existing mathematical model of the tundish was augmented to include key physical parameters needed for the prediction of the physical behaviour of steel/slag mixing phenomena. Results showed a recirculation flow in the inlet region to be responsible for both the entrainment of steel drops into the slag and slag fragments into the steel. The highest concentration of slag in the steel was found to be in the area behind the inlet where slag fragment sizes are smaller due to a high degree of turbulent energy dissipation. Likewise, higher concentrations of steel in the slag, consisting of smaller steel droplets, were only found in the inlet region and along the walls. The results indicate that only small slag fragments of approximately 10-50 microns from the covering slag reach the outlet.

  • 337.
    Song, Zhili
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    A Numerical Investigation on VOD Nozzle Jets2011Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The metallurgic process, Vacuum Oxygen Decarburization (VOD) process, is used for producing stainless steels with ultra-low carbon grades. In a VOD process, an oxygen lance is equipped with a De Laval nozzle which injects high speed oxygen gas. The aim of this work is to increase the knowledge of the flow behavior in the harsh environment of VOD vessels. Two real VOD nozzles from industry were numerically studied and compared at different temperatures and ambient pressures.

     Flow patterns of the oxygen jet under different ambient pressures were studied and the flow information at different positions from the nozzle was analyzed. In addition, the study compared the effects of different ambient temperatures on the jet velocity and the dynamic pressure. The predictions revealed that the modeling results obtained with the CFD modeling showed an incorrect flow expansion, which agreed well with the results from the De Laval theory. Moreover, a little under-expansion is somewhat helpful to improve the dynamic pressure. The jet dynamic pressure and its width for the specific nozzle geometry have also been studied. It has been observed that a variation in the ambient pressure can influence the jet momentum and its width. In addition, a high ambient temperature has a positive effect on the improvement of the jet dynamic pressure.

    For the comparison between the two nozzles concerned, the modeling results showed that one of the nozzles was more applicably proper for lower pressures, displaying a more stable flow pattern. Furthermore, it was found that a change in ambient pressure has a stronger effect on the jet force than a change in ambient temperature. In addition, it was proved that the profiles of the dynamic pressure at a certain blowing distance fit well to Multi-Gaussian curves.

     

  • 338.
    Song, Zhili
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Ersson, Mikael
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    A Study of Post Combustion in a BOF converter2013Report (Other academic)
  • 339.
    Song, Zhili
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Ersson, Mikael
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    A study of post-combustion in an AOD flue2014In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 85, no 7, p. 1173-1184Article in journal (Refereed)
    Abstract [en]

    An investigation on the post-combustion phenomena in an argon oxygen decarburization (AOD) system containing a converter and a flue has been conducted. An AOD converter is mainly characterized by nozzles installed at the lower side of the converter. The nozzles are intended to inject the decarburization gas of oxygen mixed with an inert gas such as argon. The injection promotes stirring and lowers the partial pressure of CO in the converter. For the AOD converter of interest in the current work, a fan is installed in the end of the AOD flue to help extract the off-gas from the converter. The influence of different fan gauge pressures as well as temperatures of the gas mixture, containing the generated CO and argon, on the post-combustion in the whole AOD system was studied. The realizable k-epsilon model was employed as the turbulence model. In addition, the reaction and radiation were also taken into account by use of the species transport model and the discrete ordinate model. It was indicated from the modeling results that the post-combustion was only present in the flue for the present modeling conditions. Moreover, a critical fan gauge pressure was found, which could yield a maximum post-combustion in the flue gas. Finally, no obvious change on the post-combustion was shown if the inlet gas mixture temperature was varied between 1500 and 1700 degrees C.

  • 340.
    Song, Zhili
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Ersson, Mikael
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Mathematical comparison of two VOD nozzle jets2011In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 51, no 10, p. 1637-1646Article in journal (Refereed)
    Abstract [en]

    Studies of physical phenomena in a jet caused by VOD (Vacuum Oxygen Decarburization) nozzles have been carried out. The VOD process is a metallurgical process where the steel-making route is controlled under vacuum environment with oxygen top blowing. In this work, two VOD nozzle models have been employed for an investigation based on two real De Laval geometries used in industry. Numerical modeling was used to study oxygen blowing states of the nozzles at different temperatures and ambient pressures. The nozzle models were numerically computed with two dimensional domains, where vacuum conditions and temperatures were specifically defined. The modeling results showed that one of the nozzles was more applicably proper for lower pressures, displaying a more stable flow pattern. Furthermore, it was found that a change in ambient pressure has a stronger effect on the jet force than a change in ambient temperature. In addition, it was proved that the profiles of the dynamic pressure at a certain blowing distance fit well to Multi-Gaussian curves.

  • 341.
    Song, Zhili
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Ersson, Mikael
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Mathematical Modeling of VOD Oxygen Nozzle Jets2011In: Steel Research International, ISSN 1611-3683, Vol. 82, no 3, p. 249-259Article in journal (Refereed)
    Abstract [en]

    This study has focused on numerically exploring the oxygen flow in the convergent-divergent De Laval nozzle. The De Laval nozzle has been commonly used as oxygen outlet at the lance tip in the vacuum oxygen decarburization (VOD) process. The nozzle geometry used in an active VOD plant was investigated by isentropic nozzle theory as well as by numerical modeling. Since an optimal nozzle design is only valid for a certain ambient pressure, one VOD nozzle will be less efficient for a large part of the pressure cycle. Different ambient pressures were used in the calculations that were based on the De Laval nozzle theory. Flow patterns of the oxygen jet under different ambient pressures were studied and the flow information at different positions from the nozzle was analyzed. In addition, the study compared the effects of different ambient temperatures on jet velocity and dynamic pressure. The predictions revealed that the modeling results obtained with the CFD modeling showed incorrect flow expansion, which agreed well with the results from the De Laval theory. Moreover, a little under-expansion is somewhat helpful to improve the dynamic pressure. The jet dynamic pressure and its width for the specific nozzle geometry have also been studied. It has been observed that an altering ambient pressure can influence the jet momentum and its width. In addition, a high ambient temperature has a positive effect on the improvement of the jet dynamic pressure.

  • 342.
    Song, Zhili Jack
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Modeling of Gas Flows in Steelmaking Decarburization Processes2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The purpose of the current study is to increase the understanding of different steelmaking processes at the decarburization stages by use of mathematical modeling. More specifically, two De-Laval nozzles from a VOD (Vaccum Oxygen Decarburization) process, which is used for producing stainless steels with ultra-low carbon grades, was investigated for different vessel pressures. Moreover, the post combustion phenomena in a BOF or LD (Linz-Donawitz) process as well as an AOD (Argon Oxygen Decarburization) process were studied focusing on the decarburization stage.

    Two industrial VOD nozzles were numerically studied and compared at different temperatures and ambient pressures. Flow patterns of the oxygen jet under different ambient pressures were predicted and the flow information at different positions from the nozzle was analyzed. In addition, the effects of different ambient temperatures on the jet velocity and the dynamic pressure were compared. The predictions revealed that a little under-expansion is somewhat helpful to improve the dynamic pressure. The jet dynamic pressure and its width for the specific nozzle geometry were also studied. It was observed that a variation in the ambient pressure can influence the jet momentum and its width. In addition, a high ambient temperature was found to have a positive effect on the improvement of the jet dynamic pressure. Furthermore, it was found that a change in ambient pressure has a stronger effect on the jet force than a change in the ambient temperature. In addition, it was proved that the profiles of the dynamic pressure at a certain blowing distance fit well to Multi-Gaussian distribution.

    Post combustion in a BOF/LD and an AOD process during decarburization was also studied. Two mathematical models were created to show the post combustion phenomenon inside the converters, respectively. For the CFD modeling of the two processes, the realizable k-ɛ model, the species transport model and the discrete ordinate were adopted to calculate the turbulence, gas reaction and radiation present in the gas phase in the converter. For the BOF/LD modeling, a series of plant tests were conducted to collect data, which were used in the current model. These include the off-gas information, emissivity data, oxygen blowing parameters and the chemical composition

    of steel. After the simulation, the predicted flow pattern and detailed information of the gases taking part in the post combustion were compared to plant data. Specifically, the off-gas data from the plant was used for the model verification. The measured CO2 concentration was 15-20 wt% and the predicted value from the modeling was 16.7 wt%.

    For the AOD converter of interest in the current work, a fan is installed in the end of the AOD flue to help extract the off-gas from the converter. The influence of different fan gauge pressures as well as temperatures of the gas mixture, containing the generated CO and argon, on the post combustion in the whole AOD system was studied. It was indicated from the modeling results that the post combustion was only present in the flue for the present modeling conditions. Moreover, a critical fan gauge pressure (approx.. -550 Pa) was found which could yield a maximum post combustion in the flue gas.

    For both two models (BOF/LD and AOD), simulations indicated that a change of the converter temperature from 1500 to 1700 °C did not influence the post combustion reaction to a large degree. In addition, these two models can be regarded as the first step for a future more in-depth modeling work of the post combustion.

  • 343. Steneholm, K.
    et al.
    Andersson, M.
    KTH.
    Tilliander, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Removal of hydrogen, nitrogen and sulphur from tool steel during vacuum degassing2013In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 40, no 3, p. 199-205Article in journal (Refereed)
    Abstract [en]

    The removal of hydrogen, nitrogen and sulphur during vacuum degassing of a tool steel grade was studied. Both slag and steel samples were collected before and after vacuum treatment for 10 heats. From these, the chemical compositions of steel and slag were determined. Thereafter, the removal rates of sulphur, hydrogen and nitrogen were calculated. For sulphur and hydrogen only first order reaction models were considered. However, for nitrogen both first order and second order kinetic models were studied. The results showed that the removal of hydrogen and nitrogen can be described with first order reaction models. However, the removal rate of sulphur follows the equilibrium sulphur content at all stages during the vacuum degassing. It is also clear that after 10 min of degassing the hydrogen and nitrogen removal is more or less finished for the studied steel grade. However, the sulphur refining can still be carried out for longer times to reach lower values.

  • 344.
    Steneholm, Karin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Andersson, Margareta A. T.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Nzotta, Mselly
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Effect of top slag composition on inclusion characteristics during vacuum degassing of tool steel2007In: Steel Research International, ISSN 1611-3683, Vol. 78, no 7, p. 522-530Article in journal (Refereed)
    Abstract [en]

    The focus of the study was to investigate the effect of the chemical composition of the top slag on the inclusion chemical composition during vacuum treatment of a plastic mould tool steel. Sampling was done before and after vacuum degassing. The chemical composition of the inclusions was determined by using SEM combined with EDX. The results showed that several inclusion compositions were found before vacuum degassing, while only one main composition of inclusions was present after vacuum degassing. Furthermore, the composition of the top slag was found to have a great influence on the composition of the inclusions found in samples taken after vacuum degassing. The present study also shows that the vacuum degassing effectively reduces the number of inclusions in steel. Finally, the thermodynamic calculations of the activities using Wagner's equation were found to predict a lower oxygen activity value than the calculations made using the Thermo-Calc software.

  • 345.
    Steneholm, Karin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Andersson, Margareta A.T.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Change of inclusion characteristics during vacuum degassing of tool steel2006In: Steel Research International, ISSN 1611-3683, Vol. 77, no 6, p. 392-400Article in journal (Refereed)
    Abstract [en]

    The inclusion characteristics were studied during vacuum degassing by interrupting the operation at five different times after the start of operation. Slag and steel samples were collected and thereafter assessed with respect to steel and slag composition, total oxygen content, size distribution of inclusions and chemical composition of inclusions. The main conclusion is that the number of inclusions in the different size classes as well as the total oxygen content seem to reach a minimum value after around ten minutes of vacuum degassing. Furthermore, it seems to be a consistent trend that, during vacuum degassing, the top slag influences the inclusion composition.

  • 346.
    Storm, Per
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Lager, Thomas
    Samuelsson, Peter
    Managing the manufacturing-R & D interface in the process industries2013In: R &D Management, ISSN 0033-6807, E-ISSN 1467-9310, Vol. 43, no 3, p. 252-270Article in journal (Refereed)
    Abstract [en]

    In the perspective of value creation and capture, firms in the future must not only be excellent in developing commodities or innovative functional products; they must also be able to manufacture them in a competitive cost structure within the framework of a proper business model. Deploying a conceptual model of the material transformation system in the process industries, the relationship between firms' manufacturing and innovation activities has been explored in three case studies representing the food, mineral and steel industries. Using the methodology of Quality Function Deployment, each firm's position on the model structure has been condensed into a matrix relating the manufacturing system's characterizing variables to the firm's raw material innovation, innovation of process technology and product innovation. The importance of the area of process innovation stands out in all these firms, and among the individual variables product flexibility' ranked highest in all of them. It is recommended that in the development of corporate innovation strategies, the productmarket perspective ought to be supplemented by a processmanufacturing perspective. Combining the information from both perspectives and striking a proper balance ought to be beneficial in overbridging the manufacturingR&D interface.

  • 347.
    Strandh, Jenny
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    A study of solid and liquid inclusion separation at the steel-slag interface2005Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    This thesis work aimed to provide a better knowledge of inclusion behavior at the steel-slag interface. All results are based on mathematical modeling of liquid and solid inclusion separation to the slag. The model descriptions of the inclusion transfer are based on the equation of motion at the system. It is assumed that the inclusion transfer is governed by four forces acting on the inclusion as it has reached the steel-slag interface. These are the buoyancy force, the added mass force, the drag force and the rebound force. The models assume two cases of inclusion separation depending on the inclusion Reynolds number. In the case where Reynolds number is larger or equal to unity, Re≥1, a steel film is formed between the inclusion and the slag. This steel film must first be drained before the inclusion can separate to the slag. If Reynolds number, Re<1, then no steel film is formed and the inclusion will be in direct contact with the slag. The mathematical models also propose three types of inclusion behavior as the inclusion crosses the steel-slag interface. The inclusion can either, pass and separate to the slag, oscillate at the interface with the possibility of reentering the steel bath with the steel flow or it can remain at the interface not completely separated to the slag. A parameter study for 20 μm inclusions showed that the most important parameters controlling the inclusion behavior at the steel-slag interface are the slag viscosity and the interfacial tensions between the phases. For 100μm inclusions also the inclusion density affects the inclusion behavior. The models were applied to ladle and tundish conditions. Since the slags in the chosen industrial conditions have not been studied experimentally before, estimations of the important physical property parameters were made. Future measurements will therefore be needed in order to make predictions of inclusion transfer behavior at the steel-slag interface which are more relevant for the industry. The main conclusion is that useful plots can be made in order to illustrate the tendency for the inclusion transfer and how to manipulate the physical property parameters in order to increase the inclusion separation in ladles and tundishes.

  • 348.
    Strandh, Jenny
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Eriksson, Robert
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    A mathematical model to study liquid inclusion behavior at the steel-slag interface2005In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 45, no 12, p. 1838-1847Article in journal (Refereed)
    Abstract [en]

    The separation of non-metallic inclusions at the interface between the steel and the slag in the ladle, tundish and mold is an essential part of the production of clean steel. It is therefore, of great importance to have a deep understanding of the phenomena controlling the transfer of inclusions from the steel to the slag layer. In this work a mathematical model, derived from the equation of particle motion, have been used to study the transfer of liquid inclusions to slags. The effects of the drag, added mass, buoyancy and rebound force on the inclusion transfer are considered. The model relies, to a great extent, on the availability of accurate information of the magnitude of a number of physical properties of the involved phases. Among those properties, the interfacial tension between the phases and the slag viscosity were found to be the most critical. Due to the fact that the availability of experimentally obtained high-temperature physical property data, relevant to the industrial conditions, is scarce in the literature several different model descriptions have been used in this work to estimate these properties. The mathematical model has been used to investigate the separation of liquid non-metallic inclusions, of different size and composition, to a number of different industrial ladle slag compositions.

  • 349.
    Strandh, Jenny
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Eriksson, Robert
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Solid inclusion transfer at a steel-slag interface with focus on tundish conditions2005In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 45, no 11, p. 1597-1606Article in journal (Refereed)
    Abstract [en]

    The separation of non-metallic inclusions from the steel to the slag phase in the ladle during secondary steel making operations and in the tundish and mold during casting is very crucial to the production of clean steel. In this work a theoretical study of the separation of solid inclusions, alumina and others, at the steelslag interface applied to the actual conditions in the tundish has been carried out. The theoretical model is based on the equation of motion with the following forces acting on an inclusion as it tries to cross the interface between the metal and the slag; buoyant, added mass, rebound and drag force. A sensitivity analysis study was carried out in order to clarify which of the parameters in the model that had the largest influence on the inclusion displacement. The results showed that the interfacial tensions (sigma(MI), sigma(IS), sigma(MS)) and the slag viscosity (us) have the largest influence on the predicted displacement. It was also concluded that the overall wettability should be positive and that the slag viscosity should be as low as possible to obtain the most favorable conditions for inclusion transfer at the steel-slag interface.

  • 350. Stuer, Michael
    et al.
    Carry, Claude Paul
    Bowen, Paul
    Zhao, Zhe
    KTH, School of Chemical Science and Engineering (CHE), Chemistry. KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Ceramics. KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Comparison of apparent activation energies for densification of alumina powders by pulsed electric current sintering (spark plasma sintering) and conventional sintering-toward applications for transparent polycrystalline alumina2017In: Journal of Materials Research, ISSN 0884-2914, E-ISSN 2044-5326, Vol. 32, no 17, p. 3309-3318Article in journal (Refereed)
    Abstract [en]

    In the quest for high real in-line transmittances for transparent polycrystalline alumina (PCA), we need defect free processing. One of the biggest advances in producing high density defect free ceramics over recent years has been the advent of spark plasma sintering (SPS) or pulsed electric current sintering. The production of PCA with high transmittances >60% has been demonstrated, but the mechanisms behind this fast, pressure aided sintering method are still much debated. Here, we investigate the sintering of doped a-alumina powders using traditional and pulsed electric current dilatometry. We demonstrate that at the final sintering stage, there is no major difference in the sintering mechanisms between conventional sintering and SPS sintering. High densification rates occurring in SPS are shown to be related to powder reorientation at the very early sintering stage and viscous-flow dominated densification in the intermediate sintering cycle. This paper clarifies what parameters in the processing-sintering domain have to be improved for even higher real in-line transmittances for PCA.

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