| 1. |
- Andersson, Margareta, et al.
(author)
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Some Aspects on Grain Refining Additions with Focus on Clogging during Casting
- 2006
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In: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 46:6, s. 814-823
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Journal article (peer-reviewed)abstract
- Some ideas of how to study optimum conditions for implementation of grain refining in liquid steel processing with focus on how to avoid clogging are discussed. It is assumed that the inclusions most beneficial for grain refining are known from studies by physical metallurgists. The challenge for a process metallurgist is how to provide a homogeneous distribution of grain refiners at the onset of solidification. Four different ways of providing information to succeed with this are discussed. Thermodynamic modeling can be used to predict what additions to make to create potential grain refiners, if relevant thermodynamic data is available. Mathematical fluid-flow modeling can be used to study where to add potential grain refiners. It is discussed that the tundish is the most appropriate reactor to add grain refiners, since enough time is given to a complete mixing of the grain refiner into the steel before the steel enters the mold. By using the scanning laser microscopy technique it is possible to study which potential grain refiners has the lowest attraction forces between each other. This is important in order to minimise growth of inclusions when they collide during transport in the tundish, which can lead to the formation of larger inclusions that do not serve as useful grain refiners. Finally, it is suggested that laboratory experiments are carried out in order to study the tendency for nozzle clogging, before the use of grain refiners is tested in industrial scale.
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| 2. |
- Appelberg, Jesper, et al.
(author)
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In situ studies of misch-metal particle behavior on a molten stainless steel surface
- 2008
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In: Materials Science & Engineering. - : Elsevier BV. - 0921-5093 .- 1873-4936. ; 495:1-2, s. 330-334
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Journal article (peer-reviewed)abstract
- The use of misch-metal is widely spread among the stainless steel producers. Casting problems like clogging are common when using these additions. Information about Ce-La-Al-O particles formed due to the addition of misch-metal in the ladle is scarce in the open literature. The aim of this study is to increase the knowledge of the particle behavior and the particle characteristics in two stainless steels resulting from the addition of misch-metal. The in situ particle behavior has been studied using a Confocal Laser Scanning Microscope.
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| 3. |
- Bjurstrom, M., et al.
(author)
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Physical-modeling study of fluid flow and gas penetration in a side-blown AOD converter
- 2006
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In: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 46:4, s. 523-529
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Journal article (peer-reviewed)abstract
- The main fluid-flow pattern that results in a converter with side gas injection was studied using physical modeling. Having roughly the same viscosity as liquid steel, water was used in the experiments. The velocity of the water was determined for different positions in the vessel symmetry plane by laser Doppler velocimetry. Experiments were performed using combinations of three different bath heights and four different gas-flow rates. The results showed penetration of the gas plume into the steel bath both at the tuyere and bath level to increase with an increased gas-flow rate. Also, the penetration depth of the gas both at the tuyere and bath surface level were more affected by an increased gas-flow rate than an increased bath height. Finally, the overall fluid-flow pattern in the system was found to change both with an increased bath height and an increased gas-flow rate.
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| 4. |
- Ersson, Mikael, 1977-, et al.
(author)
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A Mathematical Model of an Impinging Air Jet on a Water Surface
- 2008
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In: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 48:4, s. 377-384
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Journal article (peer-reviewed)abstract
- A fundamental mathematical model of the flow field and surface deformation caused by an impinging jet in a top blown reactor has been developed. The results have been validated against water model experiments. More specifically, the predicted penetration depth has been found to agree well with surface deformation measurements and predictions using analytical equations. Furthermore, the predictions of the location of a vortex have been found to agree fairly well with PIV measurements. Calculations were also done to compare the widely used standard k-ε model against the realizable extension of the standard k-ε model to calculate the turbulent conditions of the flow. It was found that the penetration depth caused by the impinging jet on the liquid surface is relatively unaffected by the choice of turbulence model employed. However, when the main re-circulation loop in the bath was investigated there was a clear distinction in the flow fields produced when the two different turbulence models were used.
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| 5. |
- Ersson, Mikael, et al.
(author)
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Coupled thermodynamic and kinetic modeling of a top-blown bath
- 2006
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In: Sohn International Symposium Advanced Processing of Metals and Materials, Vol 2. - 0873396359 ; , s. 271-281
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Conference paper (peer-reviewed)abstract
- A fundamental mathematical model of lance blowing on a bath surface has been developed with a purpose to increase the understanding of various phenomena in top blown oxygen converters. The model is based on the Navier-Stokes equations and turbulence is predicted using the k-epsilon model. In the present model the deformation of the liquid surface, caused by the impinging gas jet, is described using a VOF formulation. The mathematical model results have been verified by comparing predicted penetration-depth data with experimental results from physical model trials. The fluid dynamic modeling has also been coupled with the thermodynamic modeling to predict the reaction rate/distribution occurring in the vessel. The focus has been on carbon and a qualitative comparison of the predicted carbon content in the hot spot area and in droplets with experimental data from laboratory trials has been done.
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| 6. |
- Ersson, Mikael, 1977-, et al.
(author)
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Dynamic Coupling of Computational Fluid Dynamics and Thermodynamics Software : Applied on a Top Blown Converter
- 2008
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In: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 48:2, s. 147-153
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Journal article (peer-reviewed)abstract
- A novel modeling approach is presented where a computational fluid dynamics software is coupled to thermodynamic databases to obtain dynamic simulations of metallurgical process phenomena. The modeling approach has been used on a fundamental model of a top-blown converter. Reactions between gas-steel, gas-slag, steel-slag and gas-steel-slag have been considered. The results show that the mass transport in the surface area is totally controlled by convection. Also, that a large amount of CO produced during the decarburization might slow down the rate of decarburization in droplets ejected from the bath. For the present simulation conditions reflecting laboratory experiments, it was also seen that the amount of slag (FeO and/or SiO2) created is close to zero, i.e. only gas (CO+CO2) is created as the oxygen jet hits the steel bath. It was also illustrated how an extrapolation of the decarburization rate, sampled from a few seconds of simulation, could be done to get a rough estimate of the carbon content at a later stage in the process as long as the carbon content is relatively high. The overall conclusion is that it is possible to make a dynamic coupling of the Thermo-Calc databases and a CFD software to make dynamic simulations of metallurgical processes such as a top-blown converter.
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| 7. |
- Ersson, Mikael, 1977-, et al.
(author)
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Dynamic Modeling of Steel, Slag and Gas Reactions during Initial Blowing in a Top-Blown Converter
- 2008
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In: ISIJ International. - 0915-1559 .- 1347-5460.
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Journal article (other academic/artistic)abstract
- A dynamic modeling approach is presented where a computational fluid dynamics software is coupled to a thermodynamics software to obtain simulations of reactions between steel, slag and gas in a top-blown converter. For each simulation the transport of momentum, energy and mass of species as well as the thermodynamic equilibrium in each cell containing at least two phases was treated. The overall conclusion is that the present calculation procedure is successful for dynamic simulations of interaction between an oxygen gas jet with a melt and a slag. The predicted rate of decarburization was found to agree well with experimental data from laboratory trials. In addition, four cases where simulated for which the temperature, the dissolved carbon content and the dissolved oxygen content were varied. The most important findings from these comparisons were that: i) a higher initial oxygen concentration in the melt yields a larger decarburization rate, ii) carbon content also plays a big role for the desiliconization where a low carbon content is required for desiliconization to take place, iii) decarburization and desiliconization is largely influenced by the temperature at which reactions take place, where low temperature favors desiliconization and iv) the region affected by a lower carbon/silicon concentration (hot-spot region) directly below the jet was approximately 10 mm for the current setup.
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| 8. |
- Ersson, Mikael, 1977-, et al.
(author)
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Fluid Flow in a Combined Top and Bottom Blown Reactor
- 2006
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In: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 46:8, s. 1137-1142
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Journal article (peer-reviewed)abstract
- Physical modeling was done to study the flow field in a cylindrical bath agitated by bottom purging, top lance blowing and a combination of both injection types. A particle image velocimetry (PIV) system has been used to capture the velocity field of all three cases mentioned above. Special attention was paid to the recirculation loop. Top blowing creates a re-circulation loop in a relatively small volume close to the surface, compared to bottom- and combined-blowing. Increasing bottom flow rate moves the center of the re-circulation loop downwards into the liquid. When top blowing is combined with bottom blowing the center of the re-circulation loop is moved downwards into the liquid with increasing top lance flow rate.
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| 9. |
- Hallgren, Line, et al.
(author)
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Effect of nozzle type and swirl on flow pattern for initial filling conditions in the mould for up-hill teeming
- 2007
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In: Steel Research International. - : Wiley. - 1611-3683. ; 78:3, s. 254-259
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Journal article (peer-reviewed)abstract
- With increasingly more stringent requirements on steel quality and productivity in uphill teeming production, it is vital to attain more desirable fluid flow conditions in the filling of the mould. In this investigation, physical and mathematical modelling was carried out to study the effects of nozzle type and utilization of a swirl generator in the inlet nozzle on the flow pattern in the ingot mould during the initial filling period. Specific focus was on the effects on the resultant hump and axial velocities. Three cases were considered: 1) a straight nozzle, 2) a divergent nozzle, and 3) a divergent nozzle combined with a swirl generator. It was found that usage of the divergent nozzle, compared to the straight nozzle, resulted in a smaller hump and lower axial velocities in the bath. For the combination of divergent nozzle and swirl generator, these findings were even more pronounced, with the hump practically eliminated, and the axial velocities, as well as the turbulence at the meniscus, significantly lower. The findings of the study suggest that a divergent nozzle combined with a swirling flow generated in the nozzle could be used in the up-hill teeming process in purpose to get calmer initial filling conditions.
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| 10. |
- Nordqvist, A., et al.
(author)
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Characterisation of metal droplets sampled during top lance blowing
- 2009
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In: Ironmaking & steelmaking. - : Informa UK Limited. - 0301-9233 .- 1743-2812. ; 36:6, s. 421-431
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Journal article (peer-reviewed)abstract
- 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.
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| 11. |
- Safavi Nick, Reza, et al.
(author)
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Effect of Particle Properties on the Solid Flow Profile in a Blast Furnace
- 2009
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In: Journal of Iron and Steel Research International. - 1006-706X .- 2210-3988. ; 16:Part 2 Suppl. 2, s. 1112-1115
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Journal article (peer-reviewed)abstract
- 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.
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| 12. |
- Swartling, Maria, et al.
(author)
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Heat Transfer Study of Blast Furnace 2 at SSAB Oxelösund
- 2009
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In: Journal of Iron and Steel Research International. - 1006-706X .- 2210-3988. ; 16:Part 2 Suppl. 2, s. 1131-1136, s. 1131-1136
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Journal article (peer-reviewed)abstract
- This paper presents a heat transfer study, based on the actual conditions of the hearth of Blast Furnace 2 at SSAB Oxelosund in Sweden. Initially, an experimental study was carried out. The temperature of the cold surfaces of the bottom and wall lining were measured with a hand-held thermocouple. The aim of the overall study was to find a method to determine the outer surface temperature, based on lining temperature readings from permanently installed thermocouples. A heat transfer model was developed, using the established correlations from the experimental study as boundary conditions. With the model, it is possible to calculate a complete two-dimensional temperature profile of the hearth lining at any given time. The permanently installed thermocouples are used to validate the model, by comparing calculated and measured temperatures; the accuracy of the model is plus/minus 3 degrees difference.
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| 13. |
- Ternstedt, Patrik, 1979-, et al.
(author)
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Physical Modeling of Side-Blown Converters
- 2006
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In: Proc. InternationalConference on Advanced Fluid/Solid Science and Technologyin Experimental Mechanics, Sapporo, Japan, Sept. 11-14, 2006.
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Conference paper (other academic/artistic)abstract
- In order to increase the knowledge of the metallurgical process in an AOD converter, physical modeling has been done. The work has been focused on the chemical reactions, measuring the pH level in a NaOH solution with injection of CO2 gas. Also, some trials have been made to investigate the effect of the slag phase upon the flow field using PIV measurement. The effect of different ratios of solid/liquid slag on the flow field and slag entrapment has been studied. It was found that the mass transfer product of CO2 in water, kwA, increase with an increased gas flow rate and bath height. Furthermore, the effect of slag layer on the flow field was also found necessary to consider in order to more realistically resemble the actual system in an industrial AOD. Here, it was found necessary to take the solid fraction of the slag into account to describe the viscosity of an AOD slag.
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| 14. |
- Wikström, Jenny, et al.
(author)
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In situ studies of agglomeration between Al2O3-CaO inclusions at metal/gas, metal/slag interfaces and in slag
- 2008
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In: Ironmaking & steelmaking. - : Informa UK Limited. - 0301-9233 .- 1743-2812. ; 35:8, s. 589-599
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Journal article (peer-reviewed)abstract
- Studies of inclusion behaviour at the metal/slag interface is of great importance for the steel industry in order to achieve better control of both the size and amount of the inclusions, as well as improving the steel quality and the casting process. In this work agglomeration of liquid Al2O3-CaO particles at both steel/argon gas and steel/slag interfaces was studied with a confocal scanning laser microscope. In addition, agglomeration of liquid Al2O3-CaO-SiO2 inclusions present in the slag was investigated. The results showed that liquid inclusions more easily agglomerated to semiliquid inclusions than to liquid inclusions. Moreover, the agglomeration of liquid particles was found to be improved remarkably when the particles were present in the slag compared to when they were in the steel/slag interface.
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| 15. |
- Wikström, Jenny, et al.
(author)
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In situ studies of the agglomeration phenomena for calcium-alumina inclusions at liquid steel-liquid slag interface and in the slag
- 2008
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In: Materials Science & Engineering. - : Elsevier BV. - 0921-5093 .- 1873-4936. ; 495:1-2, s. 316-319
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Journal article (peer-reviewed)abstract
- Studies of inclusion behavior at the metal-slag interface are of great importance for the steel industry in order to obtain better control of the size and of inclusions as well as improving the steel quality and casting process. In this work the agglomeration of liquid Al2O3-CaO particles at the liquid steel-liquid slag interfaces are studied with a confocal scanning laser microscope. In addition, the agglomeration of liquid Al2O3-CaO inclusions already transferred to the slag is investigated. It is found that agglomeration of the liquid inclusions at the steel-slag interface could only take place when the inclusions were forced towards each other, while the agglomeration of liquid particles was seen to be noticeably enhanced when the particles were already in the slag.
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| 16. |
- Zhang, Zhi, 1982-, et al.
(author)
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Physical modeling of a sampler filling for molten steel
- 2009
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In: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 49:10, s. 1522-1529
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Journal article (peer-reviewed)abstract
- In recent years, much attention has been paid to determining not only the composition, but also the inclusion characteristics from liquid steel samples extracted from a ladle or a tundish. Here, a crucial point is that the steel sampler is filled and solidified without changing the inclusion characteristics that exist at steel making temperatures. Therefore, one of the first steps to investigate is the flow pattern inside samplers during filling in order to obtain a more in-depth knowledge of the sampling process. In this paper, this is done using physical modeling of a lollipop-shaped sampler. More specifically, particle image velocimetry was employed to capture the flow field and calculate the velocity vectors during the entire experiment. The filling rate at the pin part of the sampler was varied during the experiments. It was found that due to the geometry change at the transition from the inlet pin to the body part of the sampler, the flow is very chaotic at the initial filling stage. Furthermore, vortexes are formed in the water sampler vessel during all the fillings and the height of the vortex center varies with the filling rate. Overall, it was found that the flow patterns in the lollipop-shaped sampler vessel can be characterized into three distinct flow regions: the upper vortexes region, the lower horizontal flow region and the middle nozzle flow region.
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