| 1. |
- Dahlin, Anders, et al.
(författare)
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Influence of ladle slag additions on BOF process performance
- 2012
-
Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 39:5, s. 378-385
-
Tidskriftsartikel (refereegranskat)abstract
- A plant trial has been performed, with recycling of ladle slag to the LD converter at SSAB EMEA, Lulea, Sweden. The effect of ladle slag addition on the slag and steel composition, together with the slag weight, was investigated with sampling both during the blow and at blow end. The addition of ladle slag resulted in an increase in slag weight between 1 and 2 t throughout the blow and an increase of 3 wt-% in the slag Al2O3 content. This indicated that the ladle slag melted during the initial stages of the blow and enhanced the early slag formation. Lime additions were reduced with 3.5 kg t(-1) liquid steel without drawbacks on the phosphorus or sulphur refining. Heats with added ladle slag had an increase in blowing time with similar to 4% and an increased tendency for slopping. However, this can be handled by different lance and addition programmes.
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| 2. |
- Dahlin, Anders, et al.
(författare)
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Influence of ladle slag additions on BOF process under production conditions
- 2012
-
Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 39:5, s. 318-326
-
Tidskriftsartikel (refereegranskat)abstract
- The influence of recycled ladle slag on the basic oxygen furnace (BOF) process under production conditions was investigated in plant trials. More specifically, 25 heats with ladle slag additions and 23 heats without ladle slag additions were studied. Both steel and slag samples were collected, from which the chemical compositions were determined. In addition, several process parameters were monitored. Overall, it was found that recirculation of ladle slag during normal production conditions works fine. On the positive side, it was seen that the steel quality concerning the phosphorus and sulphur contents of liquid steel has, in accordance with previous studies, not been affected by the ladle slag additions. Furthermore, no major differences in the slag composition occur when the recycling of ladle slag to BOF is performed. Finally, in comparison to previous studies, the increased tendency for slopping when adding ladle slag could be eliminated with a change in the lance schedule. However, on the negative side, it was seen that the addition of ladle slag leads to an increased blowing time due to lower iron ore additions. Moreover, the slag weight at tapping increased due to an increased weight of added slag formers.
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| 3. |
- Samuelsson, Peter, et al.
(författare)
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Use of Physical Modelling to Study How to Increase the Production Capacity by Implementing a Novel Oblong AOD Converter
- 2017
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Ingår i: Ironmaking and Steelmaking: Processes, Products and Applications. - 0301-9233.
-
Tidskriftsartikel (refereegranskat)abstract
- 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 ???? and gas injected through six or eight tuyeres as fluids. In the model one tuyere was used for injection of ??2 gas, while air was injected through the remaining five or seven tuyeres. The reaction of ??2 and ???? (??2 + 2???? ⇄ ??&??3 + ?2?) 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 ??2 concentration, can be used to evaluate the different converter configurations. The average ??2 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 ??2. 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 ??2 concentrations in the oblong model differed by less than 2% after 165 s of injection of air and ??2 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.
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| 4. |
- Akbarnejad, Shahin, et al.
(författare)
-
Effect of Batch Dissimilarity on Permeability of Stacked Ceramic Foam Filters and Incompressible Fluid Flow : Experimental and Numerical Investigation
- 2022
-
Ingår i: Metals. - : MDPI AG. - 2075-4701. ; 12:6, s. 1001-
-
Tidskriftsartikel (refereegranskat)abstract
- Ceramic foam filters (CFFs) are used to remove inclusions and/or solid particles from molten metal. In general, the molten metal poured on the top of a CFF should reach a certain height to form the pressure (metal head) required to prime the filter. For estimating the required metal head and obtaining the permeability coefficients of the CFFs, permeability experiments are essential. Recently, electromagnetic priming and filtration of molten aluminum with low and high grades of CFF, i.e., 30, 50 and 80 pore per inch (PPI) CFFs, have been introduced. Since then, there has been interest in exploring the possibility of obtaining further inclusion entrapment and aluminum refinement by using electromagnetic force to prime and filter with stacked CFFs. The successful execution of such trials requires a profound understanding concerning the permeability parameters of the stacked filters. Such data were deemed not to exist prior to this study. As a result, this study presents experimental findings of permeability measurements for stacks of three 30, three 50 and three 80 PPI commercial alumina CFFs from different industrial batches and compares the findings to numerically modelled data as well as previous research works. Both experimental and numerical findings showed a good agreement with previous results. The deviation between the experimentally and numerically obtained data lies in the range of 0.4 to 6.3%.
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| 5. |
- Andersson, Margareta, et al.
(författare)
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Some Aspects on Grain Refining Additions with Focus on Clogging during Casting
- 2006
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Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 46:6, s. 814-823
-
Tidskriftsartikel (refereegranskat)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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| 6. |
- Andersson, Nils, et al.
(författare)
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Fundamental decarburisation model of AOD process
- 2013
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Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 40:5, s. 390-397
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Tidskriftsartikel (refereegranskat)abstract
- A mathematical fluid flow model of gas injection in an argon–oxygen decarburisation (AOD) converter process has been coupled with a high temperature thermodynamic model. The current model is a further enhancement of an earlier developed three-dimensional, three-phase model, to also include some thermodynamics of the process. The model is based on fundamental transport equations and includes separate solutions for the steel, slag and the gas phases and their coupling by friction. The AOD model has been used to predict the first injection stage of decarburisation in an AOD converter. The predictions have been found to agree well with the corresponding results from an industrial process control model. One of the important observations from the simulations was that large concentration gradients of carbon exist in the AOD at an early stage and as the first injection step approaching its end the carbon gradients diminish. Also, the results show, in accordance with theory, that the local decarburisation rate is decreased at elevated pressures.
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| 7. |
- Andersson, Nils, et al.
(författare)
-
Investigating the effectof slag on decarburization in an AOD converter using a fundamental model
- 2013
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Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 84:2, s. 169-177
-
Tidskriftsartikel (refereegranskat)abstract
- A high-temperature thermodynamics model has been coupled with a fundamental mathematical model describing the fluid flow, where boundary conditions were chosen based on data for an industrial AOD converter. Using this model, the effect of both slag phases (a liquid part and a solid part) on the decarburization was studied. More specifically, the separation of chromium oxide to liquid slag as well as the effect of the amount of rigid top slag (solid)on the decarburization was investigated. The liquid slag was considered with respect to the uptake of chromium oxide, while the rigid top slag was only considered with respect to the increase of the metallostatic pressure in the steel melt. The results suggest that separation of chromium oxide to liquid slag results in a decreased decarburization rate. The same conclusion can be drawn with respect to the amount of solid top slag.
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| 8. |
- Andersson, Nils, et al.
(författare)
-
Preliminary investigation of influence of temperature on decarburisation using fundamental AOD model
- 2013
-
Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 40:7, s. 551-558
-
Tidskriftsartikel (refereegranskat)abstract
- A high temperature thermodynamics model was earlier coupled with a fundamental mathematical model describing the fluid flow in an argon–oxygen decarburisation (AOD) converter and was initially validated for an idealised temperature description. More specifically, a linear average temperature relation was used such that the temperature would be isolated from other effects such as reactions and mixing. Thereafter, the effect of the starting temperature on the decarburisation was studied. The purpose is to provide some initial knowledge about how temperature affects the decarburisation in an AOD converter. The results suggest that the thermodynamic limit for carbon concentration after reaching the carbon removal efficiency (CRE) maxima is vertically translated downwards at higher temperatures. Furthermore, when plotting the mass ratio between CO and CO2, there is an indication of a point that may relate to a CRE maximum.
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| 9. |
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| 10. |
- Andersson, Nils Å. I., et al.
(författare)
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An in-Depth Model-Based Analysis of Decarburization in the AOD Process
- 2012
-
Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 83:11, s. 1039-1052
-
Tidskriftsartikel (refereegranskat)abstract
- A previously reported flow and reaction model for an argon-oxygen decarburization converter was extended to also include a thermodynamic description. An in-depth study of the model results has been conducted to answer how concentrations of elements and species in the converter at different locations change with time. This may contribute to the understanding of the mechanisms of the refining procedure in the argon-oxygen decarburization process. The refining procedure includes several step-wise changes of an injected gas composition to higher and higher inert gas ratio, called step changes. A step change leads to a decreased partial pressure of carbon monoxide and maintains the decarburization at a higher efficiency. The results shows early and late concentration profiles for the first injection step and suggests a way to determine when a step change should be made. Moreover, the step change could be determined by calculating the carbon concentration profiles and deciding when the carbon concentration gradients start to diminish.
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| 11. |
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| 12. |
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| 13. |
- Appelberg, Jesper, et al.
(författare)
-
In situ studies of misch-metal particle behavior on a molten stainless steel surface
- 2008
-
Ingår i: Materials Science & Engineering. - : Elsevier BV. - 0921-5093 .- 1873-4936. ; 495:1-2, s. 330-334
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Tidskriftsartikel (refereegranskat)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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| 14. |
- Berlin, Daniel, 1993-, et al.
(författare)
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Supply chain collaboration in circular supply chains : The example of Swedish steel recycling
- 2019
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Ingår i: Operations adding value to society. - Helsinki. ; , s. 1657-1666
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The aim of this paper is to investigate the role of supply chain collaboration between buyers and suppliers in the reverse flow of a system of circular supply chains. The empirical context is Swedish unalloyed steel recycling, i.e. recycling of steel with a low proportion of additional components. The paper applies a framework on mechanisms of coordination and supply chain flows to discuss the underlying rationale for how the Swedish steel recycling industry organizes coordination. At the activity level, it is shown how the inherent uncertainty of reverse flows is handled through voluntary cross-industrial cooperation and standardization.
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| 15. |
- Bjurstrom, M., et al.
(författare)
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Physical-modeling study of fluid flow and gas penetration in a side-blown AOD converter
- 2006
-
Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 46:4, s. 523-529
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Tidskriftsartikel (refereegranskat)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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| 16. |
- Chanouian, Serg, et al.
(författare)
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A Fundamental Investigation of Decarburization Reactions in the Argon–Oxygen Decarburization Converter Using Coupled Computational Fluid Dynamics and Thermodynamics Databases
- 2022
-
Ingår i: Steel Research International. - : John Wiley and Sons Inc. - 1611-3683 .- 1869-344X. ; 93:12
-
Tidskriftsartikel (refereegranskat)abstract
- Metallurgical converters such as the argon–oxygen decarburization (AOD) converter generally utilize gas blowing for the mixing and refinement of liquid steel. Due to the harsh environment of the complex and opaque system, it is common practice to study the stirring of the process through physical and numerical models. Effective mixing in the bath has an important role in refinement such as decarburization and has been vividly studied before. However, high-temperature chemical reactions that also play a major role are sparsely investigated. With the help of modeling, a computational fluid dynamics model coupled with chemical reactions is developed, allowing the study of both dynamic fluid transport and chemical reactions. Herein, the chemical reactions for a single gas bubble in the AOD are investigated. The study shows that a 60 mm oxygen gas bubble rapidly reacts with the melt and is saturated with carbon in 0.2–0.25 s at low-pressure levels. The saturation time is affected by the pressure and the composition of the injected gas bubble. The impact of ferrostatic pressure on the reactions is more significant at larger depth differences.
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| 17. |
- Chanouian, Serg, et al.
(författare)
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Inclination Effect on Mixing Time in a Gas–Stirred Side–Blown Converter
- 2021
-
Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 92:10, s. 2100044-
-
Tidskriftsartikel (refereegranskat)abstract
- Small-scale physical models are commonly used to investigate gas-stirred processes in steelmaking practice. The argon oxygen decarburization (AOD) converter is among various processes widely used in the metallurgy field and utilizes side blowing of oxygen and inert gas for mixing in the bath. Herein, the effect of the converter inclination on mixing time and jet-penetration length with a side-blown physical model is investigated. Scaling with the modified Froude number is applied on data from a real industrial AOD converter to achieve a system with reasonable gas flow rates. During the experiments, water is used to simulate liquid steel and air is blown through side-mounted nozzles for stirring. A NaCl tracer is added and subsequent conductivity measurements are used to measure mixing time. Overall, the penetration length is shown to be independent of inclination angle. The mixing time is found to be influenced by the change of bath height to diameter ratio, change of geometry in the bath volume, gas flow rate, and the intensified wave motion at the interface caused by the inclination of the vessel. The mixing time increase with 14% when 14° angle is applied.
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| 18. |
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| 19. |
- Chen, Chao, et al.
(författare)
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A Mathematical Modeling Study of the Influence of Small Amounts of KCl Solution Tracers on Mixing in Water and its Residence Time Distribution in a Continuous Flow Reactor-Metallurgical Tundish
- 2015
-
Ingår i: Chemical Engineering Science. - : Pergamon Press. - 0009-2509 .- 1873-4405. ; 137, s. 914-937
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- In an earlier research (Chen et al., 2015a) a mathematical model was established to simulate tracer mixing (a KCl solution). The predicted Residence Time Distribution (RTD) curves showed good agreements with experimental RID curves for larger amounts of tracer additions. However, for smaller additions (50 mL) of a KCl solution into water, the predicted RID curves tended to deviate from the experimental RTD curves for a tundish (a continuous flow reactor). The current paper focuses on the possibilities that the predictability for smaller additions could be resolved by using a suitable turbulence model. The performance of five different turbulence models representing different modeling techniques and levels of complexity were tested in combination with using a density-coupled mixed composition fluid model to simulate the mixing, i.e. the following models: LVEL, Chen-Kim k-epsilon, MMK k-epsilon, Explicit Algebraic Reynolds Stress Model (EARSM), and Large Eddy Simulation (LES): Wall-Adapting Local Eddy-viscosity (WALE). The results indicate that models that tend to resolve turbulence structures renders better predictions of the mixing process of smaller tracer amounts. In addition, the influence of different tracer amounts on the flow in tundish was assessed. The simulation results for 75 mL, 100 mL, 150 mL, and 250 mL KCl tracer additions were compared. The results showed that in an upward flow the tracer will, sooner or later (dependent on the tracer amount), sink to the bottom. This is due to the higher density of the tracer compared to the density of water. From a physical modeling perspective, this issue is like the "butterfly effect". It is showed that for a slight increase of the amount of tracer, the flow field might be disturbed. This, in turn, will result in a shifted RTD curve.
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| 20. |
- Chen, Chao, et al.
(författare)
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A Mathematical Modeling Study of Tracer Mixing in a Continuous Casting Tundish
- 2015
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Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science. - : Springer-Verlag New York. - 1073-5615 .- 1543-1916. ; 46:1, s. 169-190
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Tidskriftsartikel (refereegranskat)abstract
- A mathematical model based on a water model was developed to study the tracer mixing in a single strand tundish. The mixing behavior of black ink and KCl solution was simulated by a mixed composition fluid model, and the data were validated by water modeling results. In addition, a model that solves the scalar transport equation (STE) without any physical properties of the tracer was studied and the results were compared to predictions using the density-coupled model. Furthermore, the mixing behaviors of different amounts of KCl tracers were investigated. Before the model was established, KCl tracer properties such as the KCl molecule diffusion (KMD), the water molecule self-diffusion (WSD) in KCl solution, and the KCl solution viscosity (KV) were evaluated. The RTD curve of 250 mL KCl for the KMD case was closer to the water modeling results than that of the case implemented with only density. Moreover, the ensemble average deviation of the RTD curves of the cases implemented with KMD+ WSD, KMD+ KV, and KMD+ WSD+ KV to the KMD case is less than 0.7 pct. Thus, the water self-diffusion and KV were neglected, while the KCl density and KMD were implemented in the current study. The flow pattern of black ink was similar to the STE result i. e., the fluid flowed upwards toward the top surface and formed a large circulating flow at the outlet nozzle. The flow behavior of the 100, 150, and 250 mL KCl cases exhibited a strong tendency to sink to the tundish bottom, and subsequently flow through the holes in the dam. Thereafter, it propagated toward the outlet nozzle. Regarding the KCl tracer amount, the tracer concentration propagated to the outlet nozzle much faster for the larger amount case than for the smaller amount cases. However, the flow pattern for the 50 mL KCl case was somewhat different. The fluid propagated to the top surface which acted like black ink during the initial injection, and subsequently the fluid flowed throughout the holes at a much slower pace. The breakthrough time and peak concentration of RTD curves of model predictions and water modeling results showed a good agreement (all difference within 12.5 pct) for the 100, 150, and 250 mL KCl cases.
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| 21. |
- Chen, Chao, et al.
(författare)
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A Model Study of Inclusions Deposition, Macroscopic Transport, and Dynamic Removal at Steel–Slag Interface for Different Tundish Designs
- 2016
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Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science. - : Springer. - 1073-5615 .- 1543-1916. ; 47:3, s. 1916-1932
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents computational fluid dynamics (CFD) simulation results of inclusions macroscopic transport as well as dynamic removal in tundishes. A novel treatment was implemented using the deposition velocity calculated by a revised unified Eulerian deposition model to replace the widely used Stokes rising velocity in the boundary conditions for inclusions removal at the steel–slag interface in tundishes. In this study, the dynamic removal for different size groups of inclusions at different steel–slag interfaces (smooth or rough) with different absorption conditions at the interface (partially or fully absorbed) in two tundish designs was studied. The results showed that the dynamic removal ratios were higher for larger inclusions than for smaller inclusions. Besides, the dynamic removal ratio was higher for rough interfaces than for smooth interfaces. On the other hand, regarding the cases when inclusions are partially or fully absorbed at a smooth steel–slag interface, the removal ratio values are proportional to the absorption proportion of inclusions at the steel–slag interface. Furthermore, the removal of inclusions in two tundish designs, i.e., with and without a weir and a dam were compared. Specifically, the tundish with a weir and a dam exhibited a better performance with respect to the removal of bigger inclusions (radii of 5, 7, and 9 μm) than that of the case without weir and dam. That was found to be due to the strong paralleling flow near the middle part of the top surface. However, the tundish without weir and dam showed a higher removal ratio of smaller inclusions (radius of 1 μm). The reason could be the presence of a paralleling flow near the inlet zone, where the inclusions deposition velocities were much higher than in other parts.
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| 22. |
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| 23. |
- Chen, Chao, 1989-, et al.
(författare)
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Mathematical modelling of molten alloy mixing in a continuous casting tundish - A hydrodynamic study
- 2015
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Ingår i: Proceedings of the 6th International Congress on the Science and Technology of Steelmaking, ICS 2015. - : Chinese Society for Metals. ; , s. 407-411
-
Konferensbidrag (refereegranskat)abstract
- The emergence of the nozzle clogging have inspired steelmakers to optimize the alloying routine from alloying in ladle to alloying in tundish or in continuous casting mould. Meanwhile, wire injection in tundish has been shown to be successful for postalloying and tundish temperature adjustment. However, there is limited information on the continuous feeding of alloy in tundishes. There are three aspects to be considered: a) "alloy melting", b) "alloy particle dispersion" and c) "liquid alloy mixing". In the present paper, the "liquid alloy mixing" process is studied using CFD (Computational Fluid Dynamics) from a hydrodynamic perspective. In the simulation, the molten alloy is described by the density coupled mixed composition fluid model, which has been verified and validated by water modelling experiments using black ink and KCl tracer mixing in water as a priori. In the present model, the density of the liquid alloy is assumed to be 1.15 or 0.85 times of that of the liquid steel. Thereafter, the denser alloy injection at two positions has been studied, i.e. near the inlet (L1) and at the centre of the tundish (L2). The results indicate that the breakthrough time for the mass fraction of alloy at the outlet are about 100s for both locations. The difference is when the alloy was injected at the center (L2), there is a bypassing flow above the dam. As a result, the mass fraction of alloy at the outlet increases rapidly but the homogeneity in the tundish bath is reduced. Moreover, the denser alloy injection with different velocities was studied. The result shows that the mixing is slightly enhanced during the initial injection stage for the big velocity case. Besides, a test simulation on the mixing of a lighter alloy indicates that the alloy is floating to the top surface.
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| 24. |
- Chen, Chao, 1989-
(författare)
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Some Aspects on Macroscopic Mixing in a Tundish
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Two aspects on macroscopic mixing in a continuous flow system – metallurgical tundish were studied. Specifically, 1) the first focus was on salt solution tracer mixing, which is important for tundish design from perspectives of tracer technology and Residence Time Distributions (RTD) as well as for the understanding of the macroscopic mixing in tundishes. The different amounts of salt solution tracer mixing in a tundish were studied by using both physical models and mathematical models. The disturbance of KCl salt tracer on the flow in the tundish with respect to different amounts is like the “butterfly effect”, i.e. only a slight increase of the amount of tracer, the flow field might be disturbed. This, in turn, will result in a shifted RTD curve. 2) The second focus was on Eulerian modeling of inclusions macroscopic transport and removal, which is important for tundish design from perspectives of inclusions removal and to provide information of macroscopic removal of inclusions. In the study, an approach that combined the meso-scale inclusions deposition at turbulent boundary layers of steel-slag interface and the macroscopic transport of inclusions in the tundish was used. The theoretical calculation results showed that the effect of the roughness on the deposition velocity of small inclusions (radius of 1 μm) were more pronounced than that for the big inclusions (up to the radius of 9 μm). The dynamic inclusions removal studies showed that the tundish with a weir and a dam exhibited a better performance with respect to the removal of bigger inclusions (radii of 5 μm, 7 μm and 9 μm) than that of the case without weirs and dams. However, the tundish without weirs and dams showed a higher removal ratio of smaller inclusions (radius of 1 μm).
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| 25. |
- Compañero, Reinol Josef, et al.
(författare)
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Appraising the value of compositional information and its implications to scrap-based production of steel
- 2023
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Ingår i: Mineral Economics. - : Springer Nature. - 2191-2203 .- 2191-2211.
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Tidskriftsartikel (refereegranskat)abstract
- The current nature of steel design and production is a response to meet increasingly demanding applications but without much consideration of end-of-life scenarios. The scrap handling infrastructure, particularly the characterization and sorting, is unable to match the complexity of scrapped products. This is manifested in problems of intermixing and contamination in the scrap flows, especially for obsolete scrap. Also, the segmentation of scrap classes in standards with respect to chemical compositions is based on tolerance ranges. Thus, variation in scrap composition exists even within the same scrap type. This study applies the concept of expected value of perfect information (EPVI) to the context of steel recycling. More specifically, it sets out to examine the difference between having partial and full information on scrap composition by using a raw material optimization software. Three different scenarios with different constraints were used to appraise this difference in terms of production and excess costs. With access to perfect information, production costs decreased by 8–10%, and excess costs became negligible. Overall, comparing the respective results gave meaningful insights on the value of reestablishing the compositional information of scrap at the end of its use phase. Furthermore, the results provided relevant findings and contribute to the ongoing discussions on the seemingly disparate prioritization of economic and environmental incentives with respect to the recycling of steel.
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| 26. |
- Compañero, Reinol Josef, et al.
(författare)
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Circular Steel: How Information and Actor Incentives Impact the Recyclability of Scrap
- 2021
-
Ingår i: Journal of Sustainable Metallurgy. - : Springer Nature. - 2199-3823 .- 2199-3831.
-
Tidskriftsartikel (refereegranskat)abstract
- Recycling plays a vital role in preserving resources like steel and consequently in a circular economy. Scrap dealers and steel mills, the main business units in this system, often encounter opposing financial and sustainability incentives in using scrap as feedstock because regular sorting and scrap-preparation infrastructure cannot deal with the increasing complexity of steel scrap. Mismatches between the inputs and the target composition of the recycled steel result in trade-offs that favor the economics at the expense of resource efficiency. By examining literature and interviewing several actors, different scrap characteristics were identified as dimensions of scrap quality. Quality is typically associated with chemical composition, which is important, but this study aims to elaborate the concept of quality further and to connect it to the realities of scrapyard operations. Industry actors have different definitions for desired content, physical condition, shape and size, and homogeneity, based on their needs. Very few studies examine these details. Additionally, the relationship of quality and the level of information about the characteristics of the material was established. Having more definitive information on scrap increases opportunities for resource-efficient actions. This work offers an alternative perspective on how to address issues pertinent to recycling.
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| 27. |
- Eriksson, Robert, et al.
(författare)
-
An experimental study of the velocity field during filling of an ingot mould
- 2003
-
Ingår i: Steel research. - : Wiley. - 0177-4832 .- 1611-3683. ; 74:7, s. 423-430
-
Tidskriftsartikel (refereegranskat)abstract
- In the present study the velocity field in a 1:3 scale water model of a 4.2-tonne ingot mould was determined using Laser Doppler Anemometry (LDA). The velocity was measured in the horizontal and vertical directions at several different locations along the centre plane of the model. The effect of different volumetric flow rates and water temperatures was also investigated. The reproducibility of the measurements was found to be satisfactory, since the mean velocity at any measurement location had an average difference of around 10% between two fillings. The effect of different volumetric flow rates showed that while decreasing the flow rate, the mean velocity at the bottom turned from an upward direction to a downward direction. At the top of the model the difference between the mean velocities for the different flow rates was less pronounced. An influence of the temperature on the mean velocity could be observed. However, further studies are required to verify this result.
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| 28. |
- Ersson, Mikael, 1977-, et al.
(författare)
-
A Mathematical Model of an Impinging Air Jet on a Water Surface
- 2008
-
Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 48:4, s. 377-384
-
Tidskriftsartikel (refereegranskat)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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| 29. |
- Ersson, Mikael, et al.
(författare)
-
Coupled thermodynamic and kinetic modeling of a top-blown bath
- 2006
-
Ingår i: Sohn International Symposium Advanced Processing of Metals and Materials, Vol 2. - 0873396359 ; , s. 271-281
-
Konferensbidrag (refereegranskat)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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| 30. |
- Ersson, Mikael, 1977-, et al.
(författare)
-
Dynamic Coupling of Computational Fluid Dynamics and Thermodynamics Software : Applied on a Top Blown Converter
- 2008
-
Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 48:2, s. 147-153
-
Tidskriftsartikel (refereegranskat)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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| 31. |
- Ersson, Mikael, 1977-, et al.
(författare)
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Dynamic Modeling of Steel, Slag and Gas Reactions during Initial Blowing in a Top-Blown Converter
- 2008
-
Ingår i: ISIJ International. - 0915-1559 .- 1347-5460.
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)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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| 32. |
- Ersson, Mikael, et al.
(författare)
-
Dynamic modelling of steel, slag and gas during initial blowing in a top-blown converter
- 2011
-
Ingår i: Steel Grips - Journal of Steel and Related Materials. - 1611-4442 .- 1866-8453. ; :9, s. 41-47
-
Tidskriftsartikel (refereegranskat)abstract
- A coupling between computational fluid dynamics (CFD) and thermodynamics has recently been done. In the current model improvement, a more realistic model was developed, where the numbers of gas species and slag phases were increased. 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. Read how this calculation procedure can handle dynamic simulations of interaction between an oxygen gas jet, a melt and a slag. How is the agreement between the predicted rate of decarburization and experimental data? Which findings were achieved from the simulation of four cases varying the temperature, the dissolved carbon content and the dissolved oxygen content?
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| 33. |
- Ersson, Mikael, 1977-, et al.
(författare)
-
Fluid Flow in a Combined Top and Bottom Blown Reactor
- 2006
-
Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 46:8, s. 1137-1142
-
Tidskriftsartikel (refereegranskat)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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| 34. |
- Ersson, Mikael, et al.
(författare)
-
Review on CFD Simulation and Modeling of Decarburization Processes
- 2018
-
Ingår i: Steel Research International. - : WILEY-V C H VERLAG GMBH. - 1611-3683 .- 1869-344X. ; 89:1
-
Forskningsöversikt (refereegranskat)abstract
- Over the last few decades, a number of CFD models have been dedicated to increasing the understanding of the decarburization processes in steelmaking. However, these processes are highly complex with large variations in time and length, and this makes the systems extremely demanding to simulate. Several reports have been published where parts of the processes have been investigated numerically, but to date no models have been presented that can handle the entire complexity of the processes. Here, a review of the research performed on the subject from 1998 to 2016 is given. A table summarizing the models used and the key focus of the studies is given, and it can be concluded that the effort put in so far to investigate the decarburization in steelmaking is substantial, but not complete. The currently available numerical models give an insight into process parameters such as reactions, mixing time, temperature distribution and thermal losses, off-gas post combustion and de-dusting, and also nozzle configuration. With the recent developments in numerical modeling and the increase in hardware capability, the future of simulation and modeling of the decarburization processes in steelmaking seems bright.
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| 35. |
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| 36. |
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| 37. |
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| 38. |
- Gauffin, Alicia, 1984-
(författare)
-
Improved mapping of steel recycling from an industrial perspective
- 2015
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The results from this study show that it is possible to obtain data series on the steel scrap collection based on mass balance model on the crude steel production figures by steelmaking reactor type and additional knowledge on process metallurgy as well as information on inputs and outputs into the reactors with an area correlation coefficient of 0,91 compared to data obtained from trade statistics. Furthermore, the study shows that based on a new method it is possible to calculate the time duration of mass flows on a continuous basis. Furthermore, two complementary statistical dynamic material flow models that can be used to calculate the societal recycling rates of steel was constructed. These statistical models contribute to a standardized way of obtaining consistent results. The new models are able to segregate the non-recirculated amounts of steel into the hibernating steel stock available for future collection from the amounts of losses based on statistics. The results show that it is possible to calculate the amounts of steel scrap available for steelmaking at a given point in time. In addition, based on the new models it is possible to calculate recycling trends in society. Also, the models are able to calculate robust forecasts on the long-term availability of steel scrap, and test if forecast demand of steel scrap exceeds a full recovery. This due to that the steel scrap generation is a function of the collection rate of steel scrap. Also, a method for obtaining representative samplings on the alloy content in steel scrap called random sampling analysis (RSA) was developed. The results from the RSA show that it is possible to optimize the recovery of valuable elements in the production process of steelmaking based on the information on the composition of steel scrap.
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| 39. |
- Gauffin, Alicia, et al.
(författare)
-
KTH Steel Scrap Model : Iron and Steel Flow in the Swedish Society 1889–2010
- 2013
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Ingår i: Journal for Manufacturing Science and Production. - : Walter de Gruyter GmbH. - 2191-0375 .- 2191-4184. ; 13:1/2, s. 47-54
-
Tidskriftsartikel (refereegranskat)abstract
- KTH Steel Scrap Model calculates material flows of iron and steel in the Swedish society based on statistics, mass balance and mass flow analysis and industry knowledge. The material flows of iron and steel were calculated for external scrap consumption, internal scrap, domestic steel scrap arising and net flow of iron and steel into the Swedish society. Model output on external steel scrap consumption and domestic steel scrap arising was compared to an earlier analysis done by Jernkontoret for the timeline 1980–2009. The results show that mass balance calculations are area wise corresponding to consumption figures based on trade statistics. In addition the difference in trend is assumed to be mainly due to stocking effect. Furthermore it is shown that mass balance and mass flow models could be used as a tool to calculate apparent scrap consumption based on crude steel production figures by process type.
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| 40. |
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| 41. |
- Gauffin, Alicia, et al.
(författare)
-
The Global Societal Steel Scrap Reserves and Amounts of Losses
- 2016
-
Ingår i: Resources. - : MDPI AG. - 2079-9276. ; 5:3
-
Tidskriftsartikel (refereegranskat)abstract
- In this study a newly developed method called the Progressing and Backcasting models were used to evaluate the annual resource utilizations of steel scrap in Sweden and globally. The model results show that it is possible to assess the amounts of steel scrap available for steelmaking at a given point in time, based on statistical dynamic material flow models. By a better mapping of the available amounts of steel scrap reserves on a country basis, it is possible to ease the trade of scrap across country boarders. This in turn can optimize the supply of recyclable metals as a raw material used in the industry. The results for Swedish steel consumption show that export bans used to secure the domestic market of steel scrap do damage the internal market due to increased amounts of losses. This suggests that export bans should be lifted to optimize recycling in countries. The model results also show that the global losses of steel are higher than for an industrialized country such as Sweden. Furthermore, the results show that the Backcasting and Progressing models can be used to calculate robust forecasts on the long term availability of steel scrap assets. This information could be used for future structural plans of scrap consuming steelmaking mills and waste management facilities. Hence, it is possible to contribute to a sustainable industrial development and a circular economy.
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| 42. |
- Gauffin, Alicia, et al.
(författare)
-
Time-varying losses in material flows of steel using dynamic material flow models
- 2017
-
Ingår i: Resources, Conservation and Recycling. - : Elsevier. - 0921-3449 .- 1879-0658. ; 116, s. 70-83
-
Tidskriftsartikel (refereegranskat)abstract
- A method for annual evaluation of recycling rates in material flows was established to enable a consistent analysis of resource utilizations. The algorithm to calculate the time-varying losses was derived based on a sound statistical approach that would be viable for both historical data and future predictions. This method eliminates the need for adjustable parameters and is solely based on input data of the material consumption and scrap collection. This article describes the model methodology and the calculation procedures to classify the societal scrap reserve from the amounts of losses, based on statistics. These statistical models contribute to establish a standardized method to obtain consistent results. Based on the method the lifetime of steel data was for the first time calculated on an annual basis for the steel usage as well as for the end of life scrap amount. This was done for the Swedish steel consumption and the global steel consumption between 1900 and 2013 as well as for future predictions between 2013 and 2060. The lifetime of steel was calculated to be higher in an industrialized country such as Sweden compared to the global average value. More specifically, the service lifetimes of EOL steel in Sweden and in the World were calculated to be 35 and 28 years in 2012, respectively. This novel approach of using system specific data on the lifetime of steel on an annual basis enables a possibility to evaluate recycling trends and potentials to increase the recycling rate.
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| 43. |
- Gauffin, Alicia, et al.
(författare)
-
Use of volume correlation model to calculate lifetime of end-of-life steel
- 2015
-
Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 42:2, s. 88-96
-
Tidskriftsartikel (refereegranskat)abstract
- A new mathematical model for calculating the lifetime of steel on an annual basis, called the volume correlation model is presented. The model compares the quantities of scrap collection with the steel consumption as well as evaluates the time difference between the two data sets. The lifetime of steel was calculated for the collected end-of-life steel amounts. The calculations were performed by assuming a full recovery of the steel consumption or a non-re-circulated accumulated steel stock in society denoted the full and true lifetime of steel. Based on the volume correlation model, the lifetime of steel was calculated for the total steel, low alloyed and special steel, and stainless steel in Sweden between 1898 and 2010. Previous studies on the lifetime of steel are based on experimental measurements and numerical calculations. The full lifetime of the total amount of steel from previous studies is 31 and 35 years for the years 2000 and 2006 respectively. Based on the volume correlation model the lifetime for the total steel amount, when assuming a full recovery of the material, was calculated as 34 and 37 years for these two years. This indicates that the lifetime of steel from the volume correlation model is in a similar range, but slightly higher, compared to previously reported data. The present results show that the model could be an alternative method to calculate the lifetime of steel and other recyclable materials on an annual basis. Results show that the lifetime of the total steel amount has continuously increased between 1975 and 2010. This indicates that the accumulated steel stock in society is still large enough to withstand the high collection rate of steel scrap. Furthermore, that there are as yet no lack of untapped resource of end-of-life steel scrap assets in Swedish society.
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| 44. |
- GUO, SHUO, 1987-
(författare)
-
Evaluation of Non-Metallic Inclusions after Deformation and Their Effect on the Machinability of Steel
- 2022
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The presence of non-metallic inclusions (NMIs) have critical effects on both the mechanical properties and machinability of steels. In the present thesis, one focus is to study the characteristics of deformed sulfides (MnS) for a stainless steel (3R65) and a tool steel (42CrMo4). Three groups of MnS inclusions were detected in the samples taken after deformation of the steel: i) type RS (sulfides with a Rod-like geometry), ii) type PS (sulphides with a plate-like geometry) and iii) type OS (oxy-sulfides). Here, the elongated inclusions present in both stainless and tool steels were studied more in detail using SEM to determine the tendency for the inclusions to break. The results showed that three types of elongated MnS inclusions could be identified, namely UU, UB and BB. Here, ‘U’ represents the unbroken edge(s) of inclusion and ‘B’ represents the broken edge(s) of an inclusion. The presence of these three types of inclusions in samples collected both before and after a heat treatment was studied and the results showed that the heat treatment had a very small effect on the morphologies of the elongated MnS inclusions for both stainless steels (containing <0.1 mass % C) and tool steels (containing 0.42 mass % C). In the second part of the thesis, the characteristics of chips after machining of a 157REM Ce-treated steel and a 157C reference steel was studied. Furthermore, the effect of the NMIs on the chip breakability during machining was determined. The results show that a Ce modification of a 157C steel transforms the NMIs from large size elongated inclusions to small size inclusion with a spherical shape. This leads to an improved machinability of 157C steels. In addition, a newly developed weight distribution of chips (WDC) method, based on the chip weight measurements, was used to determine the tendencies for breaking of chips. The results of this investigation showed that the chips that were obtained from the machining of 157C and the 157REM steels could be classified into the following three types: i) type I chips (with a geometry containing one arc) and having a weight of less than 0.08 g, ii) type II chips (with a geometry containing two arcs) and having weights between 0.08 g and 0.15 g, and iii) type III chips (with a geometry containing three or more arcs) and having weights larger than 0.15 g. From industrial experience, it is known that a high amount of small type I chips will lead to a good chip breakability. The results from the machining test show that the fraction of type I chips from machining of the 157REM steel (65 %) is smaller than from machining of the 157C reference steel (80 %) when using a lower feed rate of 0.4 mm/rev. However, when using a higher feed rate of 0.5 mm/rev, 40 % of the chips belong to type I small chips for the 157REM steel and 14 % for the 157C steel. Based on the conditions used in this study and the obtained results, the following is clear in order to reach the best machinability: i) it is most advantageous to use the 157C steel when using a lower feed rate of 0.4 mm/rev and ii) it is most advantageous to use the 157REM steel when using a higher feed rate of 0.5 mm/rev.
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| 45. |
- Guo, Shuo, et al.
(författare)
-
Evaluation of Sulfide Inclusions before and after Deformation of Steel by Using the Electrolytic Extraction Method
- 2021
-
Ingår i: Metals. - : MDPI AG. - 2075-4701. ; 11:4
-
Tidskriftsartikel (refereegranskat)abstract
- The characteristics of elongated MnS have a critical effect on fatigue anisotropy and all mechanical anisotropies. A comparative investigation of nonmetallic inclusions in both stainless steels and tool steels has been carried out in this study. The inclusion characteristics were investigated using electrolytic extraction (EE) followed by scanning electron microscopy combined with energy-dispersive spectroscopy (SEM-EDS). Overall, three types of MnS inclusions (type I (regular), type II (irregular) and type III (Rod)) were found in tool steels in as-cast samples, which had not been heat-treated. Furthermore, three types of MnS inclusions (Rod-like sulfide (RS), Plate-like sulfide (PS) and Oxysulfide (OS)) were found in samples taken after rolling. Based on the breakability of the elongated MnS, three types of inclusions, Type UU, UB and BB, where U represents the undamaged or unbroken edge of an inclusion and B represents the fragment or broken edge of an inclusion, were studied in both stainless steels and tool steels both before and after additional heat treatment. The effect of heat treatment and dissolving the metal layer during the EE process is also discussed. The results show that both processes have a limited effect on the breakability of inclusions in steels with carbon contents <0.42 mass%.
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| 46. |
- Guo, Shuo, et al.
(författare)
-
Evaluation of the chip breakability after machining of Bearing steels based on Weight Distribution Methods
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- It is well known that a modification of non-metallic inclusions (NMIs) to create especially many smaller inclusions is an important way to improve the machinability of steels. The main focus of this study is the use of a REMs element (Ce) in the liquid steel to modify the NMIs, in order to improve the chip breakability and thereby the machining performance. In evaluating the success of this procedure, a newly developed evaluation method to determine the chip breakability based on chip measurements, which is called the method of weight distribution of chips (WDC), was used. Two similar steel grades were studied, where one was REM treated and the other was a reference. The chips obtained in this study during machining of these two steel grades were classified into three types: i) type I chips having the shape of one arc and a weight of less than 0.08 g, ii) type II chips having the shape of two arcs and weighing between 0.08 g and 0.15 g, and iii) type III chips having a shape consisting of more than three arcs and weights larger than 0.15 g. In order to get the best chip breakability which is good for a fast machining, as many as possible of the chips should be small type I chips. The results show that at a lower feed rate (fn = 0.4 mm/rev), 80 % of chips belong to type I small chips for the reference 157C steel and 65 % of chips belong to type I small chips for the modified 157REM steel. At a higher feed rate (fn = 0.5 mm/rev), the fraction of type I chips is 14 % but it is 40 % in the Ce treated steel grade. Thus, at the lower feed rate the reference 157C steel resulted in the best machinability, but at the higher feed rate, the Ce-treated 157REM steel resulted in the best machinability. This is due to a lower feed rate of 0.4 mm/rev and a lower temperature in the local cutting zone the presence of many MnS inclusions in the reference steel is beneficial to obtain a good chip breakability. However, at the higher feed rate of 0.5 mm/rev and the higher temperature in the local cutting zone, the MnS Inclusions become too soft while the undeformed Ce-containing inclusions remain hard, which enables them to contribute to an improved chip breakability.
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| 47. |
- Hallgren, Line, et al.
(författare)
-
A First Attempt to Implement a Swirl Blade in Production of Ingots
- 2010
-
Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 50:12, s. 1763-1769
-
Tidskriftsartikel (refereegranskat)abstract
- Plant trials were carried out to test if it would be possible to place a ceramic swirl blade in the runner channel during filling of ingots The initial experiments showed that no production disturbances were found More specifically no problems with unusual refractory wear or cracks in the refractory were found Thus it was concluded that the use of swirl blade has a potential in the future to be used to influence the initial filling conditions Also mathematical modeling was done in order to illustrate how it was possible to improve the layout of the runner system in order to increase the potential for use of swirl for the current plant conditions The results showed that the meniscus was not dampened as much when the swirl blade is positioned in a horizontal direction in the runner channel compared to the results of a previous physical modeling study where the swirl blade was placed in a vertical direction just before the steel entered the mold However if a horizontally positioned swirl blade is used in combination with an inlet with an angle of 15 degrees the hump height at the initial filling stage can be lowered from 100 to 58 mm compared to a case without a swirl blade This illustrates the potential to apply mold powder closer to the bottom without risking reoxidation due to reactions with steel and mold powder
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| 48. |
- Hallgren, Line, 1978-
(författare)
-
A Study of the Initial Mould Filling during Up-hill Ingot Casting
- 2012
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The fluid flow in the mould during up-hill teeming is of great importance for the quality of the cast ingot and thereby the quality of the final steel products. At the early stage of the filling of an up-hill teeming mould, liquid steel flows with a high velocity from the runner into the mould. The resulting turbulence on the meniscus can lead to entrainment of mould flux. The entrained mould flux might subsequently end up as defects in the final product. It is therefore very important to get a less turbulent and more stable inlet flow in the entrance region of the mould, to minimize the interactions between the steel and the mould flux. It has been acknowledged recently that a swirling motion, induced using a helix shaped swirl blade in the submerged entry nozzle, is remarkably effective to control the fluid flow pattern in both the slab and billet type continuous casting moulds. The focus in this thesis is the effect of a swirling flow, generated through a helix shaped swirl blade inserted into the runner system of the up-hill casting system, as a new method of reducing the deformation of the rising surface and the unevenness of the flow during filling of the up-hill teeming mould. The study covers a theoretical part, including mathematical modelling and water modelling experiments. Moreover, a part with some novel plant trials to test the swirling technology at the steel plants of Ovako bar in Hofors and Scana steel in Björneborg. The swirl blade has two features: (1) to generate a swirling flow in the entrance nozzle and (2) to suppress the uneven flow developed after flowing through a bend. Water modelling was used to assert the effect of the swirl blade on rectifying of tangential and axial velocities in the filling tube for the up-hill teeming and also to verify the results from the numerical calculations. The effect of swirl in combination with a diverged nozzle was also investigated in a similar way, i. e. with water model trials and numerical calculations. The earlier studies, using water as a fluid, have shown that the placement of a swirl blade in the vertical part of the runner channel, at the entrance to the mould, will be beneficial for a calm initial filling of the ingot during casting. Later, the plant trials were carried out to test if it would be possible to place a ceramic swirl blade in the runner channel during filling of ingots and to investigate the effect of a widening of the entry nozzle. Because of constrains of the current design of the runner systems at the steel plants it was not possible to place the swirl blade at the entrance. Instead, the swirl blade was placed in the horizontal part of the runner system. The initial experiments with swirl blade in the runner showed that no production disturbances were found. More specifically, no problems with unusual refractory wear or cracks in the refractory were found. Also, the mould powder consumption was found to decrease when using the swirl blade in combination with an inlet with a 6° diverged nozzle. Thus, it was concluded that the use of swirl blade has a potential in the future to be used to influence the initial filling conditions in a positive way. In addition to the plant trials with swirl blade, separate trials of changing the inlet angle from 1.7° to 6° or 10° showed that the widened inlet area resulted in a decrease in mould powder consumption. However, the decrease was not to the same extent as for the case with swirl blade.
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| 49. |
- Hallgren, Line, et al.
(författare)
-
Effect of nozzle type and swirl on flow pattern for initial filling conditions in the mould for up-hill teeming
- 2007
-
Ingår i: Steel Research International. - : Wiley. - 1611-3683. ; 78:3, s. 254-259
-
Tidskriftsartikel (refereegranskat)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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| 50. |
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