| 1. |
- Adolfsson, Daniel, et al.
(författare)
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Cementitious phases in ladle slag
- 2011
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Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 82:4, s. 398-403
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Tidskriftsartikel (refereegranskat)abstract
- Ladle slag is an internal by-product generated within the steelmaking industry during the refining of steel. The realisation of beneficial inherent properties of ladle slag as a binder supplement or substitute material is believed to be advantageous with respect to both economy and environment for steelmakers. For this reason, the current study has focused on highlighting the properties of ladle slag that are pertinent to the formation of calcium aluminate hydrates. Three fractions of ladle slag, two of which were based on different slag formers, have been characterised using XRF, XRD and calorimetric analysis. Commonly known hydraulic minerals such as mayenite, tricalcium aluminate and dicalcium silicate were detected during analysis. An important aspect in the utilisation of ladle slag is the slag handling methodology. Therefore, this study also highlights and discusses the need to reconsider slag handling procedures concerning unnecessary exposure to weathering and the possible need for further processing of the slag in order to better employ the inherent hydraulic properties of this material.
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| 2. |
- Ahmed, Hesham, et al.
(författare)
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Composite Pellets – A Potential Raw Material for Iron-Making
- 2014
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Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 85:3, s. 293-306
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Forskningsöversikt (refereegranskat)abstract
- Coke constitutes the major portion of iron-making cost and its production causes severe environmental concerns. In addition, lower energy consumption, lower CO2 emission and waste recycling are driving the Iron and steel making industry to develop “coke free, zero waste or green processes”. In the present article, an overview of possible ways to recognize a reasonable improvement in iron and steel making industry is summarized. The present discussion is focusing on the following approaches: 1. Replacing expensive coke with relatively less expensive alternate fuels having carbon as well as significant amount of hydrogen such as coal, waste plastic and biomass materials.2. Producing agglomerates from cheaper raw materials (secondary resources) as well as improving their performance in BF.3.Making the process towards higher carbon utilization by shifting the wustite equilibrium towards lower CO/CO2 ratio by using high reactive coke or catalytic activated one.4.Recycling the unused CO in the top gas by removing CO2 from the gas stream.Much attention has been paid to carbon composite agglomerates (CCA) as a promising raw material for future iron making. Production, mechanical and chemical suitability, reduction behavior, etc. are being elaborated. In addition, other possible ways to utilize CCA in alternate iron-making process has been explored.
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| 3. |
- Ahmed, Hesham, et al.
(författare)
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Effect of the Ash from H2‐Rich Carbonaceous Materials on the Physicochemical Properties of Raceway Slag and Coke Reactivity
- 2020
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Ingår i: Steel Research International. - : John Wiley & Sons. - 1611-3683 .- 1869-344X. ; 91:11
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Tidskriftsartikel (refereegranskat)abstract
- The iron and steel industry is one of the most important sectors worldwide, and it has a great impact on the global economy; however, this sector is still highly dependent on fossil carbon. To decrease this dependency, approaches to partially replace the injected pulverized coal with secondary, highly reactive, renewable (biomass) and H2‐rich materials have been studied. The injection of such materials is expected to significantly decrease the emitted CO2 from blast furnaces. However, due to the different ash composition of these alternative materials (especially alkali and alkaline earth metals) compared to that of ordinary injected coal, these materials are expected to alter the raceway slag properties and affect the coke reactivity. In the present article, the effect of the ash from different hydrogen‐rich carbonaceous materials on the raceway slag physicochemical properties as well as coke reactivity is reported. The melting characteristics of the ash briquettes in contact with the coke and wettability of the melted ash on the coke surface are determined visually using an optical heating microscope. The effect of the ash on the coke reactivity is studied by means of thermogravimetry under a continuous flow of CO2.
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| 4. |
- Ai, S., et al.
(författare)
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Ab Initio Study on Continuous Evolution of Mechanical Properties in Phase-Transition Region of Low-Carbon Steel
- 2020
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Ingår i: Steel Research International. - : Wiley-VCH Verlag. - 1611-3683 .- 1869-344X.
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Tidskriftsartikel (refereegranskat)abstract
- To control steel quality during continuous casting and subsequent heat treatment, an understanding of the evolution laws of mechanical properties during the austenite transition and the underlying mechanisms is of importance. Herein, the peak separation method is used to investigate the expansion behaviors in low-carbon steel. And the elastic properties of the matrix phase are calculated using the exact muffin-tin orbitals (EMTO) method. A continuous evolution model of high-temperature properties in the phase-transition region is established for ab initio data and experimental results. The evolution laws of the tetragonal shear elastic constant C′ and Young's modulus E agree well with that of the high-temperature strength. The critical temperature for ductility to brittleness is 850 °C. The matrix phase exhibits significantly brittleness character and increases slightly with decreasing temperature in single-phase paramagnetic (PM) γ-Fe region. The straightening zone temperature should be controlled above 950 °C to avoid cracks. In the austenite transition region, the drop rate of the magnetic moment reaches 18.90%. The findings suggest that the evolution law of mechanical properties of steels can be predicted from the elastic properties, especially during the austenite transition process, providing a basis for the prediction of material properties using ab initio methods.
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| 5. |
- Albertsson, Galina, et al.
(författare)
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Effect of Low Oxygen Partial Pressure on the Chromium Partition in CaO-MgO-SiO2-Cr2O3-Al2O3 Synthetic Slag at Elevated Temperatures
- 2013
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Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 84:7, s. 670-679
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Tidskriftsartikel (refereegranskat)abstract
- The objective of the present work is to get an understanding of the impact of Al2O3 addition on the phase relationships in the CaO-MgO-Al2O3-SiO2-Cr2O3 slags at low oxygen partial pressures (P-O2 = 10(-4) Pa), with a view to control the precipitation of Cr-spinel in the slag. The equilibrium phases in CaO-MgO-Al2O3-SiO2-Cr2O3 slag system in the range on 1673-1873 K have been investigated. The compositions close to the industrial slag systems were chosen. The Cr2O3 content was fixed at 6 wt% and MgO at 8 wt%. Al2O3 contents in the slag were varied in the range of 3-12 wt%. The basicity (CaO/SiO2) of slag was set to 1.6. Gas/slag equilibrium technique was adopted. The samples were heated to 1873 K and soaked at this temperature for 24 h. The samples were then slow cooled to 1673 K and equilibrated for an additional 24 h. The oxygen partial pressure was kept at 10(-4) Pa. A gas mixture of CO/CO2 was used to control the oxygen partial pressure. After the equilibration, the samples were quenched in water. The chromium distribution and phase compositions in the quenched slags were studied using SEM-WDS and XRD techniques. The results were compared with the phase equilibrium calculations obtained from FACTSAGE software and the samples equilibrated in air. The size of spinel crystals increased drastically after slow cooling followed by annealing compared to samples being quenched after soaking at 1873 K. It was also found that low oxygen partial pressure had a strong impact on chromium partition. The amount of spinel phase increases with increased Al2O3 content.
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| 6. |
- Allertz, Carl, et al.
(författare)
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A Study of Nitrogen Pickup from the Slag during Waiting Time of Ladle Treatment
- 2014
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Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 85:4, s. 689-696
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Tidskriftsartikel (refereegranskat)abstract
- An investigation of the nitrogen pickup of liquid steel from ladle slag after vacuum degassing was made. Nitride capacities, C-N, of a number of ladle slags were determined at controlled nitrogen and oxygen potentials at 1873K. The nitride capacities in the composition range studied were found to be very low. In accordance with the literature, the nitride capacity was found to increase with increasing SiO2 content. Industrial trials were performed. The nitrogen content of the steel was determined before and after vacuum degassing as well as after the waiting period. Three different trends of the variation of nitrogen content in the steel were observed. Both the laboratory study and the industrial trials revealed that the transfer of nitrogen from slag to steel was not the reason for nitrogen pickup in the steel subsequent to vacuum degassing.
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| 7. |
- Almcrantz, M., et al.
(författare)
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Determination of inclusion characteristics in the Asea-SKF process using the modified spark-induced OES technique as a complement in studying the influence of top slag composition
- 2005
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Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 76:9, s. 624-634
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Tidskriftsartikel (refereegranskat)abstract
- The spark-induced modified optical emission spectroscopy (OES) technique developed by Ovako Steel makes it possible to rapidly determine inclusion characteristics in steel samples. In earlier investigations using the modified spark-induced OES technique for steel samples taken from billets, predicted oxygen contents agreed well with results from conventional melt extraction analyses. In this investigation, samples taken during ladle treatment in an ASEA-SKF ladle furnace were analysed using the modified OES technique. When comparing the results with inclusion characteristics determined by conventional analysis, similar trends were found. Plant trials were also carried out where three different top slag compositions were used. The purpose was to evaluate if the modified OES technique can be used to study the effect of changes in the refining operation on inclusion characteristics. Results indicated that the modified OES technique could be used to determine the effect of a changed slag composition on the inclusion characteristics in the steel. Since the modified OES method provides rapid feedback of inclusion characteristics, it has the potential of being used for faster optimisation of ladle refining operations.
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| 8. |
- Andersson, Emma, et al.
(författare)
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The Effect of CaF2 in the Slag in Ladle Refining
- 2009
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Ingår i: Steel Research International. - 1611-3683 .- 1869-344X. ; 80:8, s. 544-551
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Tidskriftsartikel (refereegranskat)abstract
- Industrial experiments were conducted in ladle treatment at SSAB Oxelosund aiming at a reduction and even elimination of CaF2 as a component in synthetic slag formers. The effects of the presence of CaF2 on sulphur refining, lining wear as well as types and amount of inclusions were examined. The results of the plant trials indicated that the new slag without CaF2 had enough capacity for sulphur removal. On the other hand, the presence of CaF2 as a flux in the slag resulted in profound lining wear. It was also found that both the number and the types of non-metallic inclusions were not affected by the elimination of CaF2 from synthetic slag. The origins of different types of inclusions were also analysed on the basis of the experimental results. The analysis supported the finding that the presence of CaF2 had little effect on inclusions.
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| 9. |
- Andersson, Nils, et al.
(författare)
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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
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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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| 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
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Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 83:11, s. 1039-1052
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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. |
- Bai, Haitong, et al.
(författare)
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Experimental Validation and Numerical Analysis of the Swirling Flow in a Submerged Entry Nozzle and Mold by using a Reverse TurboSwirl in a Billet Continuous Casting Process
- 2016
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Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X.
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Tidskriftsartikel (refereegranskat)abstract
- As an alternative to some traditional methods to generate a swirling flow in the continuous casting process, the use of a new swirling flow generator, TurboSwirl, was studied. Specifically, a reversed TurboSwirl device was designed as part of a submerged entry nozzle (SEN) for a round billet continuous casting process. Mathematical modelling was used to investigate this new design and a water model experiment was carried out to validate the mathematical model. The predicted velocities by the turbulence models: realizable k-ε model, Reynold stress model (RSM) and detached eddy simulation (DES) were compared to the measured results from an ultrasound velocity profile (UVP) method. The DES model could give the best prediction inside the SEN and had a deviation less than 3.1% compared to the measured results. Moreover, based on the validated mathematical model and the new design of the SEN, the effect of the swirling flow generated by the reverse TurboSwirl on the flow field of the SEN and mold was compared to the design of the electromagnetic swirl flow generator (EMSFG). A very strong swirling flow in the SEN and a stable flow pattern in the mold could be obtained by the reverse TurboSwirl compared to the EMSFG.
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| 14. |
- Bergstrom, Jens, et al.
(författare)
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Very High Cycle Fatigue of Two Ductile Iron Grades
- 2016
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Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 87:5, s. 614-621
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Tidskriftsartikel (refereegranskat)abstract
- Two ductile iron grades, EN-GJS-600-3 a ferritic-pearlitic grade, and EN-GJS-600-10 a silicon strengthened ferritic nodular iron grade, are studied in the very high cycle fatigue range using a 20kHz ultrasonic test equipment. Fatigue strengths and SN-curves are achieved, and fracture surfaces and microstructures are investigated. The ferritic grade with higher ductility displays a lower fatigue strength at 10(8) load cycles than the ferritic-pearlitic grade, 142 and 167MPa, respectively. Examination of fracture surfaces shows that fatigue failures are controlled by micropores in both of the ductile iron grades, while the graphite nodule distributions do not seem to influence the difference in fatigue strengths. Prediction of the fatigue strengths, using a model for ductile iron proposed by Endo and Yanase, indicates a large potential for improvement in particular for the ferritic grade.
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| 15. |
- Bi, Yanyan, et al.
(författare)
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Three-dimensional investigations of inclusions in ferroalloys
- 2014
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Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 85:4, s. 659-669
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Tidskriftsartikel (refereegranskat)abstract
- As the requirements on material properties increase, there has been a demand on an additional knowledge on the effect of impurities in the ferroalloys on the properties. Thus, the number, morphology, size, and composition of inclusions in four different ferroalloys (FeTi, FeNb, FeSi, and SiMn) were investigated. This was done in three dimensions (3D) by using scanning electron microscopy in combination with energy dispersive spectroscopy after electrolytic extraction of the ferroalloy samples. The non-metallic and metallic inclusions were successfully analyzed on the surface of film filter. Thereafter, the particle size distribution was plotted for most of the non-metallic inclusions. The non-metallic inclusions were found to be REM oxides in FeTi, FeSi, and SiMn, Al2O3, Ti-Nb-S-O oxides in FeNb and silicon oxides in SiMn. Moreover, the intermetallic inclusions were found to be a Ti-Fe phase in FeTi, Ca-Si, and Fe-Si-Ti phases in FeSi and a Mn-Si phase in SiMn. In addition, the almost pure single metallic phases were found to be Ti in FeTi, Nb in FeNb, and Si in FeSi. As the requirements on material properties increase, the effect of impurities in ferroalloys on the steelmaking process is increasingly becoming more important. The characteristic of inclusions (morphology, number, size, and composition) in ferroalloys investigated in three-dimensional after electrolytic extraction is a good method for studying the evolution of inclusions during steelmaking.
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| 16. |
- Botero Vega, Carlos Alberto, et al.
(författare)
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Additive Manufacturing of a Cold-Work Tool Steel using Electron Beam Melting
- 2020
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Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 19:5, s. 1-6
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Tidskriftsartikel (refereegranskat)abstract
- Metal additive manufacturing (AM) is on its way to industrialization. One of the most promising techniques within this field, electron beam melting (EBM), is nowadays used mostly for the fabrication of high‐performance Ti‐based alloy components for the aerospace and medical industry. Among the industrial applications envisioned for the future of EBM, the fabrication of high carbon steels for the tooling industry is of great interest. In this context, the process windows for dense and crack‐free specimens for a highly alloyed (Cr–Mo–V) cold‐work steel powder are presented in this article. High‐solidification rates during EBM processing lead to very fine and homogeneous microstructures. The influence of process parameters on the resulting microstructure and the chemical composition is investigated. In addition, preliminary results show very promising mechanical properties regarding the as‐built and heat‐treated microstructure of the obtained material.
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| 17. |
- Brämming, Mats, et al.
(författare)
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BOF Process Control and Slopping Prediction Based on Multivariate Data Analysis
- 2016
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Ingår i: Steel Research International. - : Wiley-VCH Verlag. - 1611-3683 .- 1869-344X. ; 87:3, s. 301-310
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Tidskriftsartikel (refereegranskat)abstract
- In a complex industrial batch processes such as the top-blown BOF steelmaking process, it is a complicated task to monitor and act on the progress of several important control parameters in order to avoid an undesired process event such as "slopping" and to secure a successful batch completion such as a sufficiently low steel phosphorous content. It would, therefore, be of much help to have an automated tool, which simultaneously can interpret a large number of process variables, with the function to warn of any imminent deviation from the normal batch evolution and to predict the batch end result. One way to compute, interpret, and visualize this "batch evolution" is to apply multivariate data analysis (MVDA). At SSAB Europe's steel plant in Luleå, new BOF process control devices are installed with the purpose to investigate the possibility for developing a dynamic system for slopping prediction. A main feature of this system is steelmaking vessel vibration measurements and audiometry to estimate foam height. This paper describes and discusses the usefulness of the MVDA approach for static and dynamic slopping prediction, as well as for end-of-blow phosphorous content prediction. Multivariate data analysis (MVDA) methods have been applied on the top-blown BOF steelmaking process, with the main aim to create industrially applicable static (i.e., prior to blow), as well as dynamic in-blow batch models for predicting the slopping probability. The MVDA approach has also been investigated in regard to in-blow prediction of end-of-blow phosphorous content.
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| 18. |
- Brämming, Mats, et al.
(författare)
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Characterization of Slag‐Metal Emulsion and Its Impact on Foaming Behavior and Slopping in the LD Process
- 2019
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Ingår i: Steel Research International. - : John Wiley & Sons. - 1611-3683 .- 1869-344X. ; 90:2
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Tidskriftsartikel (refereegranskat)abstract
- In the Basic Oxygen Steelmaking (BOS) process, a heterogeneous emulsion‐solid mix will form, consisting of an emulsion of liquid slag and metal droplets, in which 2nd phase particles of undissolved fluxes and solid in‐blow precipitates are suspended. When the carbon in the metal droplets reacts with iron oxide, small bubbles of CO gas are formed. If the upward movement of these bubbles is obstructed by the physical properties of the emulsion‐solid mix, foaming will occur. Certain process conditions may lead to an excessive foam growth, in the worst case forcing foam out of the vessel. This undesired process event is known as “slopping”. Extensive studies during recent decades have shown that emulsion characteristics strongly connected to foaming are: viscosity, surface tension, and density. The extent of foaming is also dependent on bubble size; foaming increasing with smaller bubble size. However, investigations into the influence of the mineralogy and morphology of the emulsion‐solid mix on foaming in basic oxygen steelmaking are scarce. In this work, samples from trials in a 6‐tonne pilot plant BOS vessel are examined by XRD and with SEM for the determination of emulsion‐solid mix mineralogy and morphology at different stages of the oxygen blow. The study confirms the importance of tight process control in order to minimize the emulsion‐solid mix apparent viscosity and, hence, the foam height, but this without over‐oxidizing the liquid slag phase, which would result in increased gas generation within the slag‐metal emulsion.
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| 19. |
- Brämming, Mats, et al.
(författare)
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Comparison between vessel vibration and audiometry for slopping control in the top-blown BOS process
- 2011
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Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 82:6, s. 683-692
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Tidskriftsartikel (refereegranskat)abstract
- Excess slag foam growth is a frequent problem in the BOS process. In the worst case, foam is forced out of the vessel and this phenomenon, commonly called slopping, not only results in loss of valuable metal yield but also in equipment damage and lost production time. In order to minimize slopping, accurate estimation of the foam level inside the vessel is an important part of BOS process control. In the top blown BOS vessel, slopping control is achieved using both static and dynamic measures. The most common implemented technique for dynamic foam height estimation and slopping control is the audiometer system. An alternative method, vessel vibration monitoring, has been investigated as part of the work in a RFCS funded research project called IMPHOS. In order to judge the usefulness of this method, parallel vibration and audio measurements have been carried out on 130 tonne as well as on 300 tonne BOS vessels. The results show that during stable process conditions there is good agreement between the two methods with regard to foam height estimation and, as vessel vibration and audiometry are largely independent of each other, a combination of the two is likely to increase significantly the accuracy of slopping prediction. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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| 20. |
- Bölke, Kristofer, et al.
(författare)
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Physical Modeling Study on the Mixing in the New IronArc Process
- 2018
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Ingår i: Steel Research International. - : WILEY-V C H VERLAG GMBH. - 1611-3683 .- 1869-344X. ; 89:7
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Tidskriftsartikel (refereegranskat)abstract
- IronArc is a newly developed technology for pig iron production with the aim to reduce the CO2 emission and energy consumption, compared to a conventional blast furnace route. In order to understand the fluid flow and stirring in the IronArc reactor, water modeling experiments are performed. Specifically, a down scaled acrylic plastic model of the IronArc pilot plant reactor is used to investigate the mixing phenomena and gas penetration depth in the liquid bath. The mixing time is determined by measuring the conductivity in the bath, after a sodium chloride solution is added. Moreover, the penetration depth is determined by analyzing the pictures obtained during the experimental process by using both a video camera and a high speed camera. The results show that the bath movements are strong and that a circular movement of the surface is present. The mixing in the model for the flow rate of 282 NLmin(-1) is fast. Specifically, the average mixing times are 7.6 and 10.2s for a 95% and a 99% homogenization degree, respectively. This is 15% and 18% (per degree of homogenization) faster compared to the case when using 3 gas inlets and the same flow rate.
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| 21. |
- Carlsson, Leo, et al.
(författare)
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Interpretable Machine Learning—Tools to Interpret the Predictions of a Machine Learning Model Predicting the Electrical Energy Consumption of an Electric Arc Furnace
- 2020
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Ingår i: Steel Research International. - : Wiley-VCH Verlag. - 1611-3683 .- 1869-344X.
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Tidskriftsartikel (refereegranskat)abstract
- Machine learning (ML) is a promising modeling framework that has previously been used in the context of optimizing steel processes. However, many of the more advanced ML models, capable of providing more accurate predictions to complex problems, are often impossible to interpret. This makes the domain experts in the steel industry, to a large extent, hesitant to adopt these models. The valuable increase in model accuracy is diminished by the lack of model interpretability. Herein, Shapley additive explanations (SHAP) is applied to an advanced ML model, predicting the electrical energy (EE) consumption of an electric arc furnace (EAF). The insights from SHAP reveal the contributions from each input variable on the EE for every single heat in the prediction domain. These contributions are then evaluated based on process metallurgical experience.
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| 22. |
- Chai, Guocai, 1956-, et al.
(författare)
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Roles of Nitrogen on TWIP in Advanced Austenitic Stainless Steels
- 2022
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Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X.
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Tidskriftsartikel (refereegranskat)abstract
- The influence of nitrogen on the mechanical properties of two high Ni containing advanced austenitic stainless steels with low stacking fault energies is investigated. The results show that increase of nitrogen content greatly increases both strength and elongation of the steel at the same time. At the cryogenic temperature, the steels show a twin induced plasticity behavior. Ab initio calculations indicate that the increase of nitrogen slightly increases the stacking fault energy and consequently the critical shear stress for twin initiation in the steel. However, addition of nitrogen significantly increases the flow stress. This leads to a smaller critical strain for twin initiation and promotes deformation twinning in the high nitrogen steel. This is confirmed by the microstructure investigation. Deformation in steels is a competitive process between slip and twinning. Dislocation slip is dominant at low strain range, but formation of stacking fault and twinning become important in the later stages of deformation. At cryogenic temperature, it is mainly deformation twinning. The influence of nitrogen addition on magnetic property and its effect on deformation twinning are also discussed. The present study increases the understanding for the development of high-performance and low-cost advanced austenitic stainless steels.
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| 23. |
- 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
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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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| 24. |
- Chanouian, Serg, et al.
(författare)
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Inclination Effect on Mixing Time in a Gas–Stirred Side–Blown Converter
- 2021
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Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 92:10, s. 2100044-
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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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| 25. |
- Chen, Chao, et al.
(författare)
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Effects of Salt Tracer Amount, Concentration and Kind on the Fluid Flow Behavior in a Hydrodynamic Model of Continuous Casting Tundish
- 2012
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Ingår i: Steel Research International. - : John Wiley & Sons. - 1611-3683 .- 1869-344X. ; 83:12, s. 1141-1151
-
Tidskriftsartikel (refereegranskat)abstract
- The hydrodynamic modeling method that widely used to simulate the fluid flow was reconsidered and discussed in this paper. The effects of injected salt tracer amount, concentration and kind on the fluid flow behavior in a hydrodynamic model tundish were investigated. The results were compared with the mathematical modeling calculation results, that the tracer density effect was eliminated. The residence time distribution (RTD) curve of tracer introduced deviated to the left side of the calculated curve, besides the deviation was increased as dimensionless tracer amount (the ratio of tracer amount to hydrodynamic model tundish volume) increased from 0.202 × 10−3 to 1.008 × 10−3. The results of tracer concentration study were similar, namely the deviation was increased with concentration increased; on the other hand, the deformation of a “stair-shape” RTD curve occurred when tracer concentration was much lower (at dimensionless tracer amount of 0.168 × 10−3 with converting to saturated solution). Besides, the effect of tracer kind on the accuracy of hydrodynamic modeling was also studied; the measurements of KCl solution with lower density than that of NaCl solution exhibited more of accuracy. Finally, the optimized tracer in hydrodynamic model tundish of present work is saturated KCl solution with dimensionless tracer amount of 0.202 × 10−3.
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| 26. |
- Chychko, Andrei, et al.
(författare)
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Fe2MoO4 as a precursor material for Mo alloying in steel : (Part II): Upscaling test
- 2011
-
Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 82:8, s. 886-897
-
Tidskriftsartikel (refereegranskat)abstract
- The Mo yield when using three different alloying mixtures (MoO3 +C; MoO3 +C + FeOx; and MoO3+ C + CaO) was tested both in laboratory experiments (16 g and 0.5 kg scale) and industrial trials (3 ton scale). The alloying is based on in-situ formation of compounds of Mo in the mixtures from molybdenite concentrate with industrial grade Fe 2O3. Thermogravimetry (TGA) and X-ray diffraction (XRD) analyses were performed to identify the reduction steps and final products of the alloying mixtures. At least two steps of mass change were discovered during the reduction of all tested mixtures by carbon. The Mo yield for MoO3 + C mixture is 93% which was confirmed by both laboratory and industrial experiments. The Mo yield for MoO3 + C + CaO mixture is around 92% during 16 g scale laboratory and 3 ton scale industrial tests. The best results were obtained in the case of the mixture which contained FeOx, MoO3 and C, resulting in the Mo yield up to 98% at all the experiment scale levels. It was found that the combination of both lower evaporation and fast reduction by carbon of the mixture along with further dissolution in steel are necessary to provide high Mo yield during steel alloying. The calculated mass balance of 3 ton trial heats showed that only a small part of initial Mo amount (8-13 ppm) has gone into slag. Copyright
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| 27. |
- Collin, T, et al.
(författare)
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FEM study of fatigue response of 3-sheet spot welded joints
- 2006
-
Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 4:77, s. 292-296
-
Tidskriftsartikel (refereegranskat)abstract
- The commercial software used for predicting fatigue strength for load-carrying spot welds in sheet structures, like car bodies, is mainly developed for two-sheet joints. The purpose of this work was to study the fatigue properties of three-sheet spot welded joints with a dimensioning method used in the automotive industry and to compare such computational results to those obtained from a more accurate method and to experimental data. Eleven three-sheet, single spot welded specimens were studied using a structural stress approach, followed by shell element simulations, similar to those used in commercial software. These results were compared to calculations based on fine meshed solid element models. Fracture mechanics was used to evaluate the loading conditions at the spot welds. Comparison between the results from the different methods and experimental results for three shear loaded specimens, consisting of triple sheets, found in literature showed good correlation. The shell element method in shear loaded cases gives stress intensities within +35% to -5% of the solid element method results. In peel loaded cases the results differ up to -60%, an under-estimation that leads to an increase of estimated fatigue life up to 65 times.
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| 28. |
- Condo, Adolfo Firmino Timoteo, et al.
(författare)
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Study on the Effect of Aging on the Ability of Calcium Carbide for Hot Metal Desulfurization
- 2016
-
Ingår i: Steel Research International. - : Wiley-VCH Verlagsgesellschaft. - 1611-3683 .- 1869-344X. ; 87:9, s. 1137-1143
-
Tidskriftsartikel (refereegranskat)abstract
- Industrial trials and laboratory study are carried out to investigate the effect of aging on the ability of CaC2 in hot metal desulfurization. The industrial trials indicate that the time of storage of calcium carbide within the limit of industrial practice has no appreciable effect on its ability of desulfurization. In the laboratory, samples of CaC2 are prepared by exposing them in air for different times to promote formation of a Ca(OH)(2) outer layer. The thickness of Ca(OH)(2) increases with exposing time. Thereafter, the aged CaC2 samples are employed for desulfurization at 1673 and 1773 K for 8 min. For all the samples after desulfurization, layers of graphite and CaO are found between the remaining CaC2 particles and the outer CaS layer. The desulfurization using CaC2 is found to proceed by the diffusion of calcium vapor through the product layers and then its reaction with dissolved sulfur in the hot metal at the surface. No appreciable difference in the thickness of the CaS layer is found with the samples exposed to air for different times. This finding explains well the industrial results.
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| 29. |
- Condo, Adolfo Firmino Timoteo, et al.
(författare)
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Study on the Equilibrium of Slag and Hot Metal at Tapping with Respect to Sulfur
- 2017
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Ingår i: Steel Research International. - : Wiley. - 1869-344X .- 1611-3683. ; 88:6, s. 1-9
-
Tidskriftsartikel (refereegranskat)abstract
- The blast furnace slag and hot metal were collected from the industrial trials. The collected slag and hot metal samples are re-melted in a graphite crucible and stirred to investigate the sulfur partition at different stirring times. The experimental oxygen potential is well controlled to simulate the blast furnace conditions. The results show evidently that sulfur is transferred from hot metal to slag, which led to an increase in the sulfur partition from its initial value (t=0 min) of 26 -33 at 1743 K, and from 23 to 37 at 1773 K after 30 min of slag-metal reaction. The results strongly indicate non-equilibrium between slag and hot metal at tapping. The sulfide capacities of the slag with typical composition of the slag at tapping are determined. On the basis of the sulfide capacity data, the theoretical sulfur partition is evaluated. The theoretically calculated partition further supports the finding obtained in the stirring experiments. This finding would suggest the possibility of improvement to increase the usage of blast furnace slag in desulfurization.
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| 30. |
- Condo, Adolfo Firmino Timoteo, 1976-, et al.
(författare)
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Sulfide Capacities in the Al2O3-CaO-MgO-SiO2 System
- 2018
-
Ingår i: Steel Research International. - : John Wiley & Sons. - 1611-3683 .- 1869-344X. ; 89:8
-
Tidskriftsartikel (refereegranskat)abstract
- In the present study, the sulfide capacities of the slags in the ternary Al2O3-CaO-SiO2 system at 1873K, and in the quaternary system Al2O3-CaO-MgO-SiO2 at 1823 and 1873K are experimentally measured using copper-slag equilibrium at controlled oxygen partial pressure. The experimental data, which has been unavailable, are needed for the improvement of a sulfide capacity model. An assessment of the available data for sulfide capacities in the Al2O3-CaO-MgO-SiO2 system and its sub lower-order systems are made. Based on this assessment and the present experimental results, the model parameters of the existing sulfide capacity model are re-optimized. The sulfide capacity model can be successfully used in the prediction of the sulfide capacities of multicomponent slags with satisfactory accuracy.
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| 31. |
- Davydenko, Arkadiy, et al.
(författare)
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Characterization of Briquettes Used for Slag Foaming in the EAF during Stainless Steel Production
- 2014
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Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 86:2, s. 137-145
-
Tidskriftsartikel (refereegranskat)abstract
- The modern sustainable stainless steel making industry is characterized by different factors such as an efficient utilization of energy in the Electric Arc Furnace (EAF) by a slag foaming practice and an utilization of waste products from its own production facilities. In this study, the foaming briquettes applied for a combined slag foaming and waste product reduction in the EAF are characterized. The recipes of the briquettes were made based on a literature review and previous experience. Afterwards, the composition and density of briquettes were estimated and compared to calculated data. Moreover, weight reduction experiments were made on a laboratory scale at temperatures up to 1500-°C in an argon atmosphere in order to characterize the products (metal, slag, and gas). Based on these results, the calculations were compared with experimental data. The following main results were found: (i) the density of briquettes can be successfully verified, (ii) briquettes have different mechanical properties depending on the materials used for production of briquettes, and (iii) the briquettes yield in different amounts of metal and gas. Moreover, it was found that light briquettes (without FeCr) produced almost double the amount of gas in comparison with heavy briquettes (containing FeCr); valuable metals can be recovered from briquettes, and recipes of briquettes can be optimized based on the amount of metal droplets in briquettes and the total utilization of carbon. This study is focused on a characterization of briquettes, which are used for slag foaming and waste product reduction in the Electric Arc Furnace (EAF) during the stainless steel production. The experimental data is compared with calculations according to the obtained results.
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| 32. |
- Davydenko, Arkadiy, et al.
(författare)
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Investigation of Slag Foaming by Additions of Briquettes in the EAF during Stainless Steel Production
- 2015
-
Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 86:2, s. 146-153
-
Tidskriftsartikel (refereegranskat)abstract
- Nowadays, an effective application of energy required for stainless steel production in the electric arc furnace (EAF) by a slag foaming practice and recycling of waste products play two of the most significant roles for a sustainable steel production. In this study, briquettes were used to obtain a combined slag foaming and waste product reduction in the EAF process. Briquettes with different densities produced partly from waste products were tested in an industrial scale to study slag foaming in the EAF process during stainless steel production. The slag foaming tendency was determined based on visual estimations of slag foaming, evaluations of the slag density before and after addition of different briquettes, and by calculating a foaming index. The influence of the main parameters of briquettes (composition, density) and the furnace slag (composition, basicity, and, etc.) on slag foaming was studied. It was found that both heavy and light briquettes can be used for slag foaming. The heavy briquettes, with FeCr, produce about half the amount of gas compared to the light briquettes, without FeCr. The main part of the gas, >80%, was generated during the first 2-3min, Moreover, the highest slag foaming rate was obtained for slags with a basicity in the range of 1.31-1.49.
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| 33. |
- Deng, Tengfei, et al.
(författare)
-
Dissolution of Lime in Synthetic 'FeO'-SiO2 and CaO-'FeO'-SiO2 Slags
- 2010
-
Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 81:5, s. 347-355
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Tidskriftsartikel (refereegranskat)abstract
- Dissolution of different CaO samples into molten synthetic 'FeO'-SiO2 and 'FeO'-SiO2-CaO slags was carried out in a closed tube furnace at 1873K. The slag was kept stagnant. It was found that the dissolution rate was very fast when CaO rod was dipped into 'FeO'-SiO2 slag. In the case of 'FeO'-SiO2-CaO slag, the dissolution of CaO rod in the stagnant slag was retarded after the initial period (2 minutes). Only less than 16 percent CaO reacted with the slag, irrespective of the type of lime. Three phase-regions were identified in the reacted part of the lime rod by SEM-EDS analysis. The formation of these regions was explained thermodynamically. A dense layer of 2CaO center dot SiO2 was found to be responsible for the total stop of the dissolution. It could be concluded that constant removal of the 2CaO center dot SiO2 layer would be of essence to obtain a high dissolution rate of lime. In this connection, it was found necessary to study the dissolution of lime in moving slag to reach a reliable conclusion regarding the relevance of the reactivity obtained by water ATSM test to the real reactivity of lime in high temperature slag.
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| 34. |
- Deng, Tengfei, et al.
(författare)
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Experimental Design for the Mechanism Study of Lime Dissolution in Liquid Slag
- 2012
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Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 83:3, s. 259-268
-
Tidskriftsartikel (refereegranskat)abstract
- The applicability of rotating rod technique in the study of lime dissolution in slag was investigated. Both computational fluid dynamic (CFD) and cold model experiments showed that the mass transfer due to radial velocity introduced by forced convection was zero if the rod was long. The mass transfer by forced convection was also less important in comparison with natural convection and diffusion when the rod was half length of the height of the bath. This finding was in accordance with the criteria put forward by the original work that the method could only be applicable when a thin disk (instead of rod) with big diameter and big liquid bath were used. To study the lime dissolution by forced convection a new experimental technique was developed. A cube was placed in the slag that was eccentrically stirred. The whole system, viz. the sample along with the slag could be quenched. The new technique could study the effect of forced convection on the dissolution. The microscopic study on the quenched slag-lime samples could reveal the dissolution mechanism successfully.
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| 35. |
- Deng, Zhiyin, et al.
(författare)
-
Effects of Temperature and Holding Time on the Sintering of Ladle Filler Sand with Liquid Steel
- 2016
-
Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 87:7, s. 921-929
-
Tidskriftsartikel (refereegranskat)abstract
- In the present work the effects of temperature and holding time on the sintering of ladle filler sand are studied. Laboratory experiments are carried out using pellets made of chromite based filler sand and two steel grades containing different contents of Mn and Al. It is found that the liquid steel plays a major role in the sintering behavior. The results also show that the amount of liquid phase in the sintered sand pellets increases with the increase of temperature and holding time. The Al2O3 content increases substantially in the chromite phase (spinel), especially in the region close to the liquid phase, when the temperature is high enough or when the holding time is long enough. Higher content of dissolved Al would accelerate the formation of the alumina-rich chromite.
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| 36. |
- Deng, Zhiyin, et al.
(författare)
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Mechanism Study of the Blocking of Ladle Well Due to Sintering of Filler Sand
- 2015
-
Ingår i: Steel Research International. - : Wiley-VCH Verlagsgesellschaft. - 1611-3683 .- 1869-344X.
-
Tidskriftsartikel (refereegranskat)abstract
- The present work is aimed at a mechanism study of blocking of ladle well by filler sand. Laboratory experiments are carried out using two different chromite-based filler sands. The interaction between the liquid steel and the sand is also studied by using steels containing different contents of Mn and Al. The reaction between the silica phase and the chromite phase is found to be the main mechanism for the sintering of sand. The reaction results in a liquid oxide phase, which becomes the binding phase between the solid oxide grains. The amount of silica phase and its grain size are found to have great impact on the formation of the liquid oxide phase. Faster formation of the liquid oxide phase leads to more serious sintering of the sand. It is found that liquid steel can hardly infiltrate into sand. On the other hand, the presence of steel considerably increases the amount of liquid phase and enhances the sintering of the sand.
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| 37. |
- Dong, Han, et al.
(författare)
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High Nitrogen Steels
- 2023
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Ingår i: Steel Research International. - : WILEY-V C H VERLAG GMBH. - 1611-3683 .- 1869-344X. ; 94:10
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 38. |
- Doostmohammadi, Hamid, et al.
(författare)
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A Comparison of a Two-Dimensional and a Three-Dimensional Method for Inclusion Determinations in Tool Steel
- 2010
-
Ingår i: STEEL RES INT. - : Wiley. - 1611-3683. ; 81:5, s. 398-406
-
Tidskriftsartikel (refereegranskat)abstract
- To produce clean commercial tool steel the non-metallic inclusions characteristics have to be known, since they influence the mechanical properties of steel. In this work, inclusion characteristics in steel samples from plant trials were studied. The samples were collected in the steel plant according the two following methods: (a) 2D investigations of inclusions by a cross sectional method and (b) 3D investigations of inclusions collected on a film filter after electrolytic extraction. More specifically, the chemical composition, morphology, number and size distribution of inclusions in tool steel samples taken from ladle during melt treatment were determined by both methods. In both methods SEM equipped with EDS was used for compositional analysis of inclusions. In addition, in the cross sectional method an automated detection program called 'INCAFeature' was used to collect more statistics of non-metallic inclusions. The composition of inclusions larger than 5 mu m was found to contain 49% CaO based on the results from both methods. However, for smaller inclusions it was found that the accuracy of the 2D method was less than that of the 3D method due to the influence of the metal matrix on the results. In addition, it was found that a critical inclusion size of 4 mu m could be defined for the 3D method, above which the standard deviation in composition determination was very low.
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| 39. |
- Doostmohammadi, Hamid, et al.
(författare)
-
Inclusion Characteristics of Bearing Steel in a Runner after Ingot Casting
- 2010
-
Ingår i: STEEL RES INT. - : Wiley. - 1611-3683 .- 1869-344X. ; 81:2, s. 142-149
-
Tidskriftsartikel (refereegranskat)abstract
- In the uphill teaming method of ingot casting molten metal from the ladle goes into the runner system, which feeds one or several ingot moulds. This method is still important for production of bearing steel. In order to make clean steel, which has a controlled amount of inclusions, good understanding of inclusions characteristics is necessary In this work non-metallic inclusions of steel left in the runner part of an ingot casting system were studied. Inclusion type, size, and morphology were the main focus of this study A scanning electron microscope (SEM) was used to assess inclusion size and morphology The chemical composition of inclusions was determined by SEM equipped with EDS. An automated program called 'INCAFeature' was used to collect statistics of inclusion characteristics. Based on the statistical analysis of inclusion composition, four types of inclusions including oxides, sulfides, carbonitrides and complex inclusions were defined. The inclusion characteristics in the runner were also compared to literature data of inclusions found in ladle and mould samples.
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| 40. |
- Doostmohammadi, Hamid, et al.
(författare)
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Use of Computational Thermodynamic Calculations in Studying the Slag/Steel Equilibrium during Vacuum Degassing
- 2010
-
Ingår i: STEEL RES INT. - : Wiley. - 1611-3683. ; 81:1, s. 31-39
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Tidskriftsartikel (refereegranskat)abstract
- The effectiveness of a ladle refining process for production of tool steel with focus on the top slag is studied using computational thermodynamic calculations. The theoretical assessment was based on compositional data of steel and slag samples collected during trials in a plant equipped with a 65-t EAF, a ladle furnace and a vacuum degasser The calculation of slag-metal equilibrium during ladle treatment was performed for top slag excluding (Case A) and including (Case B) slag carryover and deoxidation products. The predictions showed that slag carryover and deoxidation products in the ladle significantly affect the composition of the top slag. Thus, these conditions must be taken into consideration when predicting the actual top slag composition. It was also found that it is possible to predict the final aluminium and sulphur content in steel based on the same calculation approach.
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| 41. |
- Du, Hongying, et al.
(författare)
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Characterization of Nonmetallic Inclusions in Low-Alloyed Steels Using Pulse Distribution Analysis Optical Emission Spectroscopy and Offline Investigation Methods
- 2021
-
Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 92:11, s. 2100223-
-
Tidskriftsartikel (refereegranskat)abstract
- The characteristics of nonmetallic inclusions (NMIs) in low-alloyed steel samples taken during ladle treatment before and after Ca treatment are evaluated using the pulse distribution analysis optical emission spectroscopy (PDA/OES) method, INCA-Feature investigations of inclusions on a polished surface of steel samples, and 3D investigations of NMIs after electrolytic extraction (EE) of steel samples. The investigation results of NMIs using the different methods were compared. The PDA/OES results show a clear tendency of a change in the average composition and quantity of NMIs during ladle treatment, which correlates well with the results obtained from the other two methods. Overall, it is found that the application of the PDA/OES method is appropriate to enable a fast online evaluation of inclusion compositions and their behaviors during steelmaking. This, in turn, provides the means for establishing an online control and correction of technological operations of the ladle treatment to implement necessary modification of NMIs to improve the cleanliness of steels and avoid clogging problems during casting.
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| 42. |
- Däcker, Carl-Åke, et al.
(författare)
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The influence of mould powder properties on shell formation in continuous casting of steels
- 2010
-
Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 81:10, s. 899-907
-
Tidskriftsartikel (refereegranskat)abstract
- For peritectic steel grades the shell formation is uneven resulting in quality problems such as surface cracks. Production of these steels calls for good control and knowledge of the critical factors for shell formation. By optimisation of process parameters, it is possible to enable production of crack sensitive slabs for heavy plate. This also gives a unique possibility to study the interaction between process parameters and shell formation. The paper presents the results from two large investigations with this ambition covering the total of 27+30 heats of 220 tons of steel at SSAB EMEA-Oxelösund and concludes how surface cracks can be significantly decreased. © 2010 Wiley-VCH Verlag GmbH & Co.
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| 43. |
- Ek, Mattias, et al.
(författare)
-
Study of Penetration Depth and Droplet Behavior in the Case of a Gas Jet Impinging on the Surface of Molten Metal using Liquid Ga-In-Sn
- 2012
-
Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 83:7, s. 678-685
-
Tidskriftsartikel (refereegranskat)abstract
- To study the penetration depth in the case of a gas jet impinging on the surface of liquid steel, cold model experiments were carried out using a liquid alloy GaInSn, which had similar physical properties as liquid steel. A HCl solution was used to simulate the top slag. The top phase was found to have appreciable effect on the penetration depth. Comparison of the experimental data with the predictions of the existing models indicated that most the model predictions deviated from the experimental results at higher lance heights and gas flow rates. New model parameter was suggested based on the present experimental data. The observation of the formation and movement of metal droplets generated by the gas jet was also made. The velocity of the droplet was found to be at a level only about 1% of the terminal velocity. This low velocity suggested that the turbulent viscosity played important role and the droplets could have long resident time in the slag.
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| 44. |
- Ekengren, Jens, 1976-, et al.
(författare)
-
Detecting large inclusions in steels : evaluating methods
- 2009
-
Ingår i: Steel Research International. - : Wiley-VCH Verlagsgesellschaft. - 1611-3683 .- 1869-344X. ; 80:11, s. 854-858
-
Tidskriftsartikel (refereegranskat)abstract
- The distributions of large non-metallic inclusions in two steel grades have been investigated using light optical microscopy, scanning electron microscopy and ultrasonic fatigue testing in the gigacycle range. The different methods have inherently different capabilities for finding inclusions in different size ranges. A measure of the distribution of large inclusions is proposed as the size S at which half of the fatigue specimens are expected to contain at least one inclusion of size S or larger, corresponding to 50% failure probability. Values of S are obtained using the volume distribution estimated by the three methods. Extrapolation from microscopy measurements on surfaces agree with fatigue fractography results regarding density of large inclusions, as measured by the proposed ranking variable S
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| 45. |
- Ekengren, Jens, 1976-, et al.
(författare)
-
Detecting large inclusions in steels : evaluating methods
- 2009
-
Ingår i: Steel Research International. - Weinheim, Germany : Wiley-VCH Verlagsgesellschaft. - 1611-3683 .- 1869-344X. ; 80:11, s. 854-858
-
Tidskriftsartikel (refereegranskat)abstract
- The distributions of large non-metallic inclusions in two steel grades have been investigated using light optical microscopy, scanning electron microscopy and ultrasonic fatigue testing in the gigacycle range. The different methods have inherently different capabilities for finding inclusions in different size ranges. A measure of the distribution of large inclusions is proposed as the size S at which half of the fatigue specimens are expected to contain at least one inclusion of size S or larger, corresponding to 50% failure probability. Values of S are obtained using the volume distribution estimated by the three methods. Extrapolation from microscopy measurements on surfaces agree with fatigue fractography results regarding density of large inclusions, as measured by the proposed ranking variable S.
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| 46. |
- Eklund, Nicklas, et al.
(författare)
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Operation at High Pellet Ratio and Without External Slag Formers – Trials in an Experimental Blast Furnace
- 2009
-
Ingår i: Steel Research International. - 1611-3683 .- 1869-344X. ; 80:6, s. 379-389, s. 379-384
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Tidskriftsartikel (refereegranskat)abstract
- Blast furnaces that operate with pellets and sinter normally use high basicity sinter and acid pellets to balance the slag chemistry. When external additives are used, irregular slag formation occurs due to their uneven distribution in the burden. If basic sinter is used together with a large amount of acid pellets, all additives are incorporated in the iron bearing materials with an improved burden mixture as a consequence. During a campaign in the LKAB Experimental Blast Furnace, pellets and sinter were operated at an ultra low slag volume. A high amount of pellets was balanced with high basicity sinter. An improved blast furnace operation is shown when operating at ultra low slag volume and without external slag formers. During the test period, the blast furnace operation was smooth and stable, and the reductant rate was decreased.
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| 47. |
- El-Bealy, Mostafa Omar
(författare)
-
Advanced solute conservation equations for dendritic solidification processes : Part I: Experiments and theory
- 2013
-
Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 84:6, s. 565-583
-
Tidskriftsartikel (refereegranskat)abstract
- The macrosegregation formed in dendritic equiaxed structure during early stages of solidification of Al-4.5%Cu alloy has been studied by experimental work and by metallurgical study of cast samples taken from the experimental work. An experimental work was conducted to study the coupled effect of natural convection streams, interdendritic strain and mushy permeability of Al-4.5%Cu aluminum alloy solidified in horizontal rectangular parallelepiped cavity at different superheats. The metallurgical study includes macro-microstructure evaluation, measurements of grain size of equiaxed crystals and macrosegregation analysis. This study shows that the level of surface segregation exhibiting as positive segregation varies with superheat whereas the rest of inner ingot areas show the light fluctuation in segregation values. In addition to experimental work, there is a mathematical study which contains a complete derivation of local solute redistribution equations based on Fleming's approach under different solute diffusion mechanisms in the dendritic solid. This derivation includes also the effects of interdendritic strain and mushy permeability on the local solute redistribution distribution. Owing to the length of the study, it is presented in two parts. The first part describes the experimental work and its results as well as a detail derivation of solute conservation equations. This part also involves comparison and discussion between existing and proposed solute conservation equations. The second part contains the mathematical analyses of a two dimensional mathematical model of fluid flow, heat flow, solidification, interdendritic strain and macrosegregation. Also, this part also contains the numerical simulations by using finite difference technique "FDT" to create convection patterns, heat transfer, interdendritic strain, and macrosegregation distributions. This part also includes comparisons between the available measurements and model predications as well as full discussion of different model simulations. The mechanism of interdendritic strain generation and macrosegregation formation during solidification of dendritic equiaxed structure under different diffusion mechanisms in dendritic solid has also been explained and discussed. Macrosegregation in dendritic equiaxed structure during the early stages of solidification of Al-4.5%Cu alloy has been studied experimentally. The metallurgical study includes macro-microstructure evaluation, measurements of grain size of equiaxed crystals, and macrosegregation analysis. In addition to the experimental work, there is a mathematical study which contains a complete derivation of local solute redistribution equations based on Fleming's approach under different solute diffusion mechanisms in the dendritic solid.
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| 48. |
- El-Bealy, Mostafa Omar
(författare)
-
Advanced solute conservation equations for dendritic solidification processes part II : Numerical simulations and comparisons
- 2013
-
Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 84:6, s. 584-606
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Tidskriftsartikel (refereegranskat)abstract
- The mathematical model of derived solute equations in part I for equiaxed dendritic solidification with melt convection streams and interdendritic thermo-metallurgical strain is applied numerically to predict macrosegregation distributions with different diffusing mechanisms in dendritic solid. Numerical and experimental results are present for solidification of a Al-4.5% Cu alloy inside horizontal rectangular cavity at different superheats. The numerical simulations were performed by using simpler method developed by Patanker. The experiments were conducted to measure the cooling curves via thermocouples and the metallurgical examinations to measure the grain size and macrosegregation distributions in Part I. Preliminary validity of the model is demonstrated by the qualitative and quantitative agreements between the measurements and predications of cooling curves and predicted macrosegregation distributions including mushy permeability and interdendritic strain. In addition, several important features of macrosegregation in equiaxed dendritic solidification are identified through this combined experimental and numerical study. Also, quantitative agreements between the numerical simulations and experiments reveal several areas for future research work. The differences and errors between predicted macrosegregation results under different diffusing mechanisms have been discussed. The mathematical model of derived solute equations in Part I for equiaxed dendritic solidification with melt convection streams and thermal is applied numerically to predict macrosegregation distributions with different diffusing mechanisms in dendritic solid. Numerical and experimental results are present for solidification of a Al-4.5% Cu alloy inside horizontal rectangular cavity at different superheats.
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| 49. |
- El-Bealy, Mostafa O.
(författare)
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Air-Water Mist and Homogeneity Degree of Spray Cooling Zones for Improving Quality in Continuous Casting of Steel
- 2011
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Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 82:10, s. 1187-1206
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Tidskriftsartikel (refereegranskat)abstract
- A theoretical investigation used previous experimental works for validation of model predications and for studying the effect of different nozzle designs on the quality of continuously cast steel slabs has been undertaken. This is by optimizing the homogeneity degree of cooling pattern "HDCP'' between a pair of rolls. The idea behind this technique is to maximize the solid shell resistance against thermo-metallurgical and mechanical stresses and therefore minimizes the defects generated in different cooling zones. A 2-D mathematical model of thermal, solidification, solid shell resistance and cooling conditions has been developed. The model determines the temperature distributions, the different phases associated with the solidification and three phase peritectic reaction L + delta -> gamma of Fe-0.12%C steel alloy as well as isotherms. The effect of different cooling patterns for various spray cooling systems on the homogeneity degree and solid shell resistance are examined. In additional to traditional water and air-water (AWM) nozzles, a new design of air-water mist nozzle has been proposed to improve the homogeneity degree of spray cooling system. The results indicate generally that the increasing in the homogeneity degree of cooling conditions is proportional to the increasing in the solid shell resistance and therefore to the improving of slab quality. Model predications of different effects of different nozzle designs on the surface and inner quality levels are compared and discussed in the mold and secondary spray cooling zones.
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| 50. |
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