| 1. |
- Abdul Abas, Riad, et al.
(författare)
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Studies on Graphitisation of Blast Furnace Coke by X-ray Diffraction Analysis and Thermal Diffusivity Measurements
- 2005
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Ingår i: Steel research. - : Wiley. - 0177-4832 .- 1611-3683. ; 77:11, s. 763-769
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Tidskriftsartikel (refereegranskat)abstract
- High temperature XRD and thermal diffusivity experiments were employed to investigate the degree of graphitisation in blast furnace coke. The experiments were conducted between room temperature and 1473 K. X-ray diffraction studies were carried out in order to monitor the degree of graphitisation in the coke samples from the same campaign. In these cases, the degree of graphitisation was followed by the changes in the vertical dimension. The degree of graphitisation was found to be dependent on temperature. On the other hand, the graphitisation at each temperature was instantaneous, even at as low a temperature as 973 K and no dependency on time could be noticed. The thermal diffusivities of the coke samples taken from deeper level of the experimental blast furnace were measured using the laser-flash technique. The results from these measurements showed that thermal diffusivities increased with the degree of graphitisation, which in turn, can be affected by the level in the blast furnace at which the coke sample was taken. The present results indicate that the degree of graphitisation as followed by X-ray diffraction analysis as well as thermal diffusivities can be used to trace the thermal history of coke. DSC measurements show that the heat capacity of the coke increases with temperature towards the heat capacity of graphite, which could be due to the increasing the graphitisation degree of the coke.
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| 2. |
- Andersson, Annika, et al.
(författare)
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A study of some elemental distributions between slag and hot metal during tapping of the blast furnace
- 2004
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Ingår i: Steel research. - : Wiley. - 0177-4832 .- 1611-3683. ; 75:5, s. 294-301
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the distribution of elements between slag and hot metal from a blast furnace through calculation of distribution coefficients from actual production data. First, samples of slag and hot metal tapped from a commercial blast furnace were taken continually at 10-minute intervals for a production period of 68 hours. Distribution coefficients of manganese, silicon, sulphur and vanadium were then calculated from the results of the sample analyses. A major conclusion drawn from examination of the results was that the behaviour of the studied elements was as could be expected when approaching the equilibrium reactions from thermodynamic theory. The distributions of the elements in the slag-metal system showed clear tendencies which did not appear to be influenced by the operational conditions of the furnace. For example, for manganese, vanadium and sulphur, it was found that a higher basicity led to a decreased distribution coefficient L-Mn and L-V, but an increased L-S, which is according to theory. Another observed relationship was that slag basicity increased with an increased carbon content in the hot metal, which indicated that SiO2 was reduced to [Si] when the oxygen potential decreased. Furthermore, it was found that sulphur and silica behaviour likened that of acidic slag components, while the manganese oxide and vanadium oxide behaviour was similar to that of basic slag components.
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| 3. |
- Brandberg, Jenny, et al.
(författare)
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Water capacity model of Al2O3-CaO-MgO-SiO2 quaternary slag system
- 2007
-
Ingår i: Steel research. - : Wiley. - 0177-4832 .- 1611-3683. ; 78:6, s. 460-464
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Tidskriftsartikel (refereegranskat)abstract
- The focus of the present work was to develop a water capacity model for the quaternary slag system Al2O3-CaO-MgO-SiO2. In the model, a silicate melt was considered to consist of two ion groupings, viz. cation grouping and oxygen ion. The water capacity of a melt is supposed to depend on the interactions between the cations in the presence of oxygen ions. These interactions were determined on the basis of the experimentally measured water solubility data. Only binary interactions were employed in the model. For the system CaO-SiO2, disagreement in the literature data was found. Since the interaction between Ca2+ and Si4+ would play an important role, experiments were carried out to determine the water capacities of some CaO-SiO2 slags. For this purpose a thermogravimetric method was employed. Iso-lines of water capacities at constant MgO contents were predicted by the model and compared with the experimental data from literature. The model calculations agreed well with the experimental results.
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| 4. |
- Eriksson, Robert, et al.
(författare)
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An experimental study of the velocity field during filling of an ingot mould
- 2003
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Ingår i: Steel research. - : Wiley. - 0177-4832 .- 1611-3683. ; 74:7, s. 423-430
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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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| 5. |
- Fredriksson, Patrik, et al.
(författare)
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Thermodynamic activities of FeO in some binary FeO-Containing slags
- 2004
-
Ingår i: Steel research. - : Wiley. - 0177-4832 .- 1611-3683. ; 75:4, s. 240-246
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Tidskriftsartikel (refereegranskat)abstract
- In the present investigation, experimental measurements of the thermodynamic activities of iron oxide in the Al2O3-FeO, CaO-FeO and FeO-SiO2 systems were performed in the temperature range 1823-1873 K by using gas equilibration technique. The molten slag, kept in a Pt-crucible was brought to equilibrium with a gas mixture of known oxygen partial pressure. A part of the Fe from the FeO was reduced during the equilibration and got dissolved in the Pt phase. The samples were quenched after the required equilibration time and the slag phase as well as the platinum crucible was subjected to chemical analysis. The activities of FeO in the slag were calculated from the experimental data using thermodynamic information on the Fe-Pt binary metallic system generated and assessed earlier. The experimental results are compared with earlier thermodynamic studies of the slag systems. Reassessment with the KTH slag model is performed and the results are compared with other thermodynamic models, viz. F*A*C*T(TM) and Thermo-Calc(TM) respectively. The experimental activities predicted by the KTH slag model are in good agreement with the experimental data available in the literature. A general agreement between the various models is also observed.
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| 6. |
- Fredriksson, Patrik, et al.
(författare)
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Thermodynamic activities of FeO in some ternary FeO-containing slags
- 2004
-
Ingår i: Steel research. - : Wiley. - 0177-4832 .- 1611-3683. ; 75:6, s. 357-365
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Tidskriftsartikel (refereegranskat)abstract
- Thermodynamic data concerning FeO-containing slags is of importance in ladle refining of steel. With a view to generate a set of reliable and self-consistent thermodynamic data for these slags, experimental determination of the activities of iron oxide in the Al2O3-FeO-SiO2, CaO-FeO-SiO2 and FeO-MgO-SiO2 systems was carried out using the gas equilibration method involving CO-CO2-Ar gas mixtures in the temperature range 1823-1923 K. The slag samples kept in Pt crucibles were quenched after the equilibration and subjected to chemical analysis. The thermodynamic activities of FeO in the slags were calculated from the experimental data. The results are incorporated into a thermodynamic description of silicate melts developed in the present laboratory. The model is based on a Temkin-Lumsden approach and is able to compute the thermodynamics of higher order systems from the lower order ones. The model was updated with the present results and iso-activity contours of FeO in the three component systems are presented at 1873. The capacity of the model to predict the thermodynamic activites in four-, five-, and six-component slags is demonstrated in the case of steelmaking slags.
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| 7. |
- Persson, Mikael, et al.
(författare)
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A Thermodynamic Approach to a Density Model for Oxide Melts
- 2007
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Ingår i: Steel research. - : Wiley. - 0177-4832 .- 1611-3683. ; 78:4, s. 290-298
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Tidskriftsartikel (refereegranskat)abstract
- In an attempt to estimate the densities of complex slags, a model based on the thermodynamics ofslags developed earlier by the present authors is extended to ternary and multi-component systemsin the present work. The molar volumes of ternary and higher order systems were derived from therelative integral molar enthalpies of mixing of the corresponding slags. The higher order of slagsystems has been predicted by using the parameters from the related binary sub-systems, whichhave been evaluated earlier. Comparisons of calculated results with experimental data on molarvolumes available in literature show a satisfying agreement for a number of systems, within the limitsof experimental uncertainties. The model presents a promising method to compute the molar volumeof slag systems where no experimental data is available using the abundance of thermodynamicdata available. The model would also enable the generation of density data for slags containingAl2O3, CaO, FeO, MgO, MnO, and SiO2 compatible with the corresponding thermodynamic data.
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| 8. |
- Persson, Mikael, et al.
(författare)
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Estimation of molar volumes of some binary slags from enthalpies of mixing
- 2007
-
Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 0177-4832. ; 78:2, s. 102-108
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Tidskriftsartikel (refereegranskat)abstract
- In an effort to interlink the thermo chemical and thermo physical properties of slags, the present work was undertaken to derive the molar volumes of complex slags from the enthalpies of mixing of the corresponding slags. As a first step, binary systems of the following oxides were investigated; Al2O3, CaO, FeO, MgO, MnO, and SiO2. An empirical correlation was derived between the enthalpies of mixing and molar volumes. A comparison of the computed results on the basis of the above relationship with the experimental data on molar volumes available in literature shows that the agreement between the calculated results and measured densities is satisfactory in the case of most of the binary systems, within the limits of experimentally uncertainties. The advantage of the present approach is that it would enable prediction of molar volumes of slags that are compatible with the thermodynamic data available.
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| 9. |
- Söder, Mats, et al.
(författare)
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Inclusion growth and removal in gas stirred ladles
- 2004
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Ingår i: Steel research. - : Wiley. - 0177-4832 .- 1611-3683. ; 75:2, s. 128-138
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Tidskriftsartikel (refereegranskat)abstract
- A static modelling approach was used to study the growth and removal of inclusions during gas stirring in a ladle. A mathematical model of a gas-stirred ladle was used to predict the data necessary to calculate growth and removal of inclusions. Results indicated that inclusion growth resulting from laminar shear collisions is negligible in comparison with growth from turbulent and Stokes collisions. Furthermore, the need for a model describing inclusion flotation by spherical-cap bubbles was identified. Since the existing models presented in the literature are only valid for spherical bubbles, a model for the removal of inclusions by spherical-cap bubbles was developed. Inclusion removal to the slag, refractory and by bubble flotation was compared. The mechanism determined to be responsible for the removal of the majority of inclusions larger than 25 μm was Stokes flotation and for the majority of the smaller inclusions, bubble flotation by spherical-cap bubbles (assuming plane contact between the inclusion and the bubble).
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| 10. |
- Wu, Liushun, et al.
(författare)
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The effect of solid particles on liquid viscosity
- 2011
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Ingår i: Steel research. - : Wiley. - 0177-4832 .- 1611-3683. ; 82:4, s. 388-397
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Tidskriftsartikel (refereegranskat)abstract
- The viscosities of solid-liquid mixtures were experimentally determined for silicon oil-paraffin system at room temperature and solid-liquid oxide mixture at steelmaking temperature. The use of oil-paraffin systems was to confirm the results of high temperature measurements, the experimental conditions being very difficult to control. The silicon oil- paraffin mixtures behaved Newtonian until the particle fraction reached 0.15. At this fraction, the mixture started deviate from Newtonian flow; though some average values could still be collected with very high uncertainty. Liquid-2CaO.SiO2 mixtures and liquid-MgO mixtures were studied at steelmaking temperature with carefully prepared particle fractions and well controlled conditions. Liquid-2CaO.SiO2 mixture behaved Newtonian even when the particle fraction reached 0.1. The results of both room temperature measurements and steelmaking temperature measurements were used to examine the applicability of the existing models. Einstein-Roscoe equation was found to be the only model applicably for the systems studied. No modification of the model parameter was found necessary, though the particles were not spherical.
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| 11. |
- Werke, Mats, et al.
(författare)
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Prediciting residual stresses and hardness of a critical component using a combination of numerical and empirical methods
- 2008
-
Ingår i: Steel Research International Journal. - : Wiley-VCH Verlag. - 1611-3683. ; :Sp. Iss. 2, s. 812-819, s. 812-819
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes the experiences gained when using numerical and empirical methods in order to predict the accumulated surface characteristics for a safety component after several forging steps, controlled cooling and blasting. The forging steps were simulated in a sequence using one Finite Element (FE) code. The output forging mesh was used as input to the cooling simulation but was too coarse in order to reflect surface characteristics. The decarburisation effect during cooling that may influence the surface characteristics was not included in the cooling model. An attempt to create a parametric model of the blasting machine with output residual stresses and hardness as a function of input residual stresses, hardness and process parameters indicated the need of further investigation concerning the physical phenomena during blasting in the machine. A new method was developed for analysing the influence of the blasted surface texture on the stress intensity. The measured residual stresses and hardness span caused by variations in the blasting process were successfully used together with the stress intensity factor as input to a fatigue strength analysis. In order to establish a seamless chain of models through the manufacturing sequence further development concerning cooling and blasting models is required.
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| 12. |
- Adolfsson, Daniel, et al.
(författare)
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Cementitious phases in ladle slag
- 2011
-
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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| 13. |
- 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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| 14. |
- 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
-
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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| 15. |
- 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
-
Ingår i: Steel Research International. - : Wiley-VCH Verlag. - 1611-3683 .- 1869-344X.
-
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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| 16. |
- 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
-
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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| 17. |
- Allertz, Carl, et al.
(författare)
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A Study of Nitrogen Pickup from the Slag during Waiting Time of Ladle Treatment
- 2014
-
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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| 18. |
- 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
-
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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| 19. |
- 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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| 20. |
- 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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| 21. |
- 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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| 22. |
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| 23. |
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| 24. |
- 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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| 25. |
- Barsoum, Zuheir, et al.
(författare)
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Fatigue Assessment of Cruciform Joints Welded with Different Methods
- 2006
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Ingår i: Steel Research International. - : Wiley. - 1611-3683. ; 77:12, s. 882-888
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Tidskriftsartikel (refereegranskat)abstract
- The advantages of the relatively new laser welding method are low welding distortions and high productivity, and it opens new opportunities for welding of steel structures in the automotive and heavy machinery industries. There is a need for understanding the fatigue strength and to develop fatigue design curves for laser welded joints. In this paper fatigue testing and weld quality of Hybrid Nd: YAG laser/MAG and MAG welded non-load carrying cruciform joints is examined. Four batches were produced, tested and the results were compared. The local weld geometry of the cruciform welded joints was measured and analysed. The measured parameters were used to calculate the stress concentration factors by implementing FE-models, in order to anticipate the influence of size of weld geometrical parameters on the stress concentrations. Residual stress measurement was carried out close to the toe region using the X-ray diffraction method and weld defects (cold laps) in the cracked specimens was measured.
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| 26. |
- Bergstrom, Jens, et al.
(författare)
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Very High Cycle Fatigue of Two Ductile Iron Grades
- 2016
-
Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 87:5, s. 614-621
-
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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| 27. |
- Berntsson, Tomas, et al.
(författare)
-
Material properties of induction tempered high tensile valve spring wire
- 2006
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Ingår i: Steel Research International. - Düsseldorf : Verlag Stahleisen. - 1611-3683. ; 77:11, s. 836-843
-
Tidskriftsartikel (refereegranskat)abstract
- Most of today's hardened valve spring wires are tempered in a lead bath. The lead bath provides a stable and accurate degree of tempering of the wire, but it has environmental disadvantages and limitations in flexibility. This paper describes how induction heating can replace lead bath and how this may affect the material properties. The study includes FEM-simulations, calculation of the tempering parameter and experiments with induction tempering of three different SiCr valve spring steels carried out under pilot production. The mechanical properties of the test samples were measured. Fatigue testing of one of the steels was performed on finished springs. The results were evaluated by comparing induction-tempered wire with the conventional lead tempered reference wire. The induction tempered wire fulfilled the product requirements and corresponded in performance with the lead tempered wire.
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| 28. |
- Bi, Yanyan, et al.
(författare)
-
Three-dimensional investigations of inclusions in ferroalloys
- 2014
-
Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 85:4, s. 659-669
-
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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| 29. |
- Björklund, Johan, et al.
(författare)
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The Effect of Ladle Treatment on Inclusion Composition in Tool Steel Production
- 2008
-
Ingår i: Steel Research International. - : Wiley. - 1611-3683. ; 79:4, s. 261-270
-
Tidskriftsartikel (refereegranskat)abstract
- An in-depth SEM-investigation of the inclusion composition change in the ladle refining process during tool steel production was done. Plant trials were carried out at Uddeholm Tooling AB in Hagfors, Sweden. A series of samples was taken during ladle refining, from deslagging through vacuum treatment. The goal was evaluating the effects of the top slag and other process parameters on the inclusion composition during ladle refining. The main conclusion was that normal variations in the process have a large influence on inclusion composition. Furthermore, it was concluded that the MgO content in the top slag had a large influence on the inclusion, composition throughout the whole ladle refining process. Also, the SiO2 content in the ladle slag originating from the EAF-slag, had a noticeable effect on the inclusions. The inclusions belonging to the system Al2O3-CaO-MgO-SiO2 showed a continuous composition change throughout the ladle refining process, from high Al2O3, via MgO-spinel to finally complex types rich in CaO and Al2O3.
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| 30. |
- Bohnenkamp, U., et al.
(författare)
-
Evaluation of the density of steels
- 2000
-
Ingår i: Steel research. - : Wiley. - 0177-4832. ; 71:3, s. 88-93
-
Tidskriftsartikel (refereegranskat)abstract
- Data on physical properties of steels have been collected from the open literature and put into a database. The influence of composition on the density of steels has been analyzed. An overview over former studies is given. The steels have been investigated by regression analysis in two groups, i) ferritic and low alloy steels, and ii) austenitic steels. For ferritic steels two models are provided. The first model is based on the assumption that all C is bound in cementite and other solutes are insoluble in cementite, The second model employs the result of a thermodynamic analysis where the amount of cementite and the solubilities in ferrite and cementite were determined with computational thermodynamics. The non-linear effect of Cr and Mn in cementite was computed and regression analysis of the effect of solutes on the density of ferrite was performed. For Ti-stabilized austenitic steels, the amount of TiC and the solubilities were assessed in a thermodynamic analysis. The effect of solutes on the density of austenite was studied by regression analysis. For estimations of the density of steels containing components that are not covered by the regression analysis, the regression coefficients can be supplemented with literature data or theoretically determined values. The results obtained by the present regression analysis are: Cu and Mo increase the density of ferritic steels, and C, Cr, Mn, S, Si, and V decrease it. TiC. C, Cr, Mn, N, Si, and Ti reduce the density of austenitic steels and Cu, Co. Mo, and Ni increase it.
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| 31. |
- Bohnenkamp, U., et al.
(författare)
-
Evaluation of the elastic modulus of steels
- 2000
-
Ingår i: Steel research. - : Wiley. - 0177-4832. ; 71:3, s. 94-99
-
Tidskriftsartikel (refereegranskat)abstract
- Literature data on the physical properties of steels have been collected and put into a database. The elastic modulus of steels has been analyzed as a function of composition. An overview over former studies is given. The steels have been investigated in three groups, martensitic and ferritic steels, ferritic steels separately, and austenitic steels. For the last two groups, a thermodynamic analysis with Thermo-Gale has been performed. Regression analysis on the influence of composition on the elastic modulus was then carried out. The results for ferritic steels reveal that cementite has no effect on the elastic modulus, whereas Cr, Mo, Si, Mn, and Cu increase it. The elastic modulus of austenitic steels is reduced by Ni and Mo and increased by N, NbC, TiC, and Cr. Cr23C6, while statistically significant in the analysis, has no effect on the elastic modulus of austenitic steels, The regression coefficients found can be used to predict the elastic modulus of steels with known composition.
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| 32. |
- Bohnenkamp, U., et al.
(författare)
-
Evaluation of the electrical resistivity of steels
- 2000
-
Ingår i: Steel research. - : Wiley. - 0177-4832. ; 71:10, s. 410-416
-
Tidskriftsartikel (refereegranskat)abstract
- Literature data on the physical properties of sleets have been collected and put into a database. The resistivity of steers has been analyzed as a function of composition and microstructure. An overview over former studies is given. The steels have been investigated in two groups, ferritic steels and austenitic steels. A thermodynamic analysis with ThermoCalc has been performed. Regression analysis on the influence of composition on the resistivity was then carried out. The results for ferritic steels are: Si and Al have the highest elemental resistivity, followed by Mn. Cu, Ni, Mo, and Cr. C precipitated in cementite shows a high coefficient in the analysis when the amount of Fe bound in cementite is not considered separately. C in solution with ferrite shows no significant effect. Cr bound in cementite shows a significant effect but Mn, though present in cementite in comparable amounts, has no significant effect on the resistivity. N and C have the highest elemental resistivity in austenite, followed by the substitutional solutes Nb, Si, Ti, Cu, Ni, Mo, and Cr. The carbides NbC and Tic appear with a higher coefficient in the regression model than can be explained by phase-mixture models providing upper and lower bounds for the resistivity of two-phase alloys. Cr23C6 shows no significant effect. The regression results can be used to predict the resistivity of steels with known composition. The model predicts the resistivity of ferritic steels with a maximum deviation between experimental and computed value of 12 n Omegam and a standard deviation of 5.6 n Omegam. For austenitic steels, the model prediction shows a maximum deviation of 52 mu Omegam and a standard deviation of 20 n Omegam.
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| 33. |
- Botero Vega, Carlos Alberto, et al.
(författare)
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Additive Manufacturing of a Cold-Work Tool Steel using Electron Beam Melting
- 2020
-
Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 19:5, s. 1-6
-
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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| 34. |
- Brämming, Mats, et al.
(författare)
-
BOF Process Control and Slopping Prediction Based on Multivariate Data Analysis
- 2016
-
Ingår i: Steel Research International. - : Wiley-VCH Verlag. - 1611-3683 .- 1869-344X. ; 87:3, s. 301-310
-
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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| 35. |
- Brämming, Mats, et al.
(författare)
-
Characterization of Slag‐Metal Emulsion and Its Impact on Foaming Behavior and Slopping in the LD Process
- 2019
-
Ingår i: Steel Research International. - : John Wiley & Sons. - 1611-3683 .- 1869-344X. ; 90:2
-
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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| 36. |
- Brämming, Mats, et al.
(författare)
-
Comparison between vessel vibration and audiometry for slopping control in the top-blown BOS process
- 2011
-
Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 82:6, s. 683-692
-
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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| 37. |
- Byggnevi, Magnus
(författare)
-
LEFM analysis and service simulation testing of a welded frame structure.
- 2006
-
Ingår i: STEEL RES INT. - : Wiley. - 1611-3683. ; 77:12, s. 857-865
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper the results from fatigue analysis and testing of a welded frame are discussed. The structure contains some typical welds, which can be found on a frame to a wheel loader. The test was carried out with a service load spectrum with an overall stress ratio, R, of about -1. The fatigue cracks started from the root side of the welds in all cases. The test results were correlated with linear elastic fracture mechanics (LEFM) including different assumptions of residual stress distributions.
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| 38. |
- Bölke, Kristofer, et al.
(författare)
-
Physical Modeling Study on the Mixing in the New IronArc Process
- 2018
-
Ingår i: Steel Research International. - : WILEY-V C H VERLAG GMBH. - 1611-3683 .- 1869-344X. ; 89:7
-
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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| 39. |
- Cao, Weimin, 1981-, et al.
(författare)
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Calculation of Oxygen and Sulfur Average Velocity on the Iron Surface : A Two-dimensional Gas Model Study
- 2010
-
Ingår i: Steel Research International. - : Wiley. - 1611-3683. ; 81:11, s. 949-952
-
Tidskriftsartikel (refereegranskat)abstract
- In the present work, a two-dimensional (2D) gas model is derived and used to simulate the average velocity of individual atoms of the surface active elements oxygen and sulfur on the Fe(100) surface. The average velocity of oxygen and sulfur atoms was found to be related to the vibration frequencies and minimal energy barrier. The calculated results are based on data from density functional calculations combined with thermodynamics and statistical physics. The calculated average velocity of oxygen on the Fe (100) is lower than that of sulphur. This is because of the stronger interaction between oxygen and the first iron layer. We conclude that our simple 2D gas model may be useful for simulating and understanding the complex interfacial phenomena in the steelmaking refining process from an atomic point of view.
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| 40. |
- 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
-
Ingår i: Steel Research International. - : Wiley-VCH Verlag. - 1611-3683 .- 1869-344X.
-
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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| 41. |
- Chai, Guocai, et al.
(författare)
-
Mechanisms of Hydrogen Induced Stress Crack Initiation and Propagation in Super Duplex Stainless Steels
- 2009
-
Ingår i: STEEL RESEARCH INTERNATIONAL. - 1611-3683. ; 80:7, s. 482-487
-
Tidskriftsartikel (refereegranskat)abstract
- Austenitic and ferritic duplex stainless steels, DSS, have recently suffered from hydrogen stress induced cracking, HISC, in subsea components with a cathodic protection. This paper provides discussions on possible HISC mechanisms. HISC initiation can occur at the ferritic grain boundaries and phase boundaries at a stress lower than the yield strength, but dominantly at phase boundaries at a stress higher than the yield strength. EBSD analysis shows that HISC in DSS results from the interaction between the dynamic plasticity by creep and hydrogen diffusion. A model on the formation of microstresses in these two phases under creep conditions is proposed, which explains why HISC occurs mainly in the ferritic phase. Discontinuous two-dimensional HISC paths were observed. The austenitic phase acts as obstacles for crack propagation. The fracture covers "valleys" and "peaks" with the cleavage ferrite and the austenite with microfacets or striations due to the hydrogen-enhanced localized-plasticity.
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| 42. |
- Chai, Guocai, 1956-, et al.
(författare)
-
Roles of Nitrogen on TWIP in Advanced Austenitic Stainless Steels
- 2022
-
Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X.
-
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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| 43. |
- Chanouian, Serg, et al.
(författare)
-
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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| 44. |
- Chanouian, Serg, et al.
(författare)
-
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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| 45. |
- Chen, Chao, et al.
(författare)
-
Effects of Salt Tracer Amount, Concentration and Kind on the Fluid Flow Behavior in a Hydrodynamic Model of Continuous Casting Tundish
- 2012
-
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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| 46. |
- Chychko, Andrei, et al.
(författare)
-
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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| 47. |
- Chychko, Andrei, et al.
(författare)
-
MoO3 Evaporation Studies from Binary Systems towards Choice of Mo Precursors in EAF
- 2010
-
Ingår i: Steel Research International. - : Wiley. - 1611-3683. ; 81:9, s. 784-791
-
Tidskriftsartikel (refereegranskat)abstract
- The evaporation rate of molybdenum oxide from mixtures with CaO or MgO was studied in the temperature range 300-1573 K. The investigations were carried out using high temperature X-ray diffraction and thermogravimetry. Further, additions of these precursors to molten steel in the laboratory scale and the Mo yield achieved were determined. The X-ray studies show that the calcium molybdate is formed from the oxide mixture in the temperature interval 773-873K, which precedes the beginning of evaporation of MoO3. Results of thermogravimetric studies with mixtures CaO and MgO with MoO3 as well as the compounds CaMoO4 and MgMoO4 confirm the above results. Addition of various molybdenum precursors, viz, the mixtures of carbon with pure MoO3, CaMoO4 and MgMoO4, as well as oxide mixtures (CaO + MoO3, MgO + MoO3) show that the highest yield was observed for CaMoO4 + C and MoO3 + C mixtures, while MgO + C + MoO3 mixture showed much lower yield.
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| 48. |
- Chychko, Andrei, et al.
(författare)
-
Synthesis and characterization of Fe2MoO4 as a precursor material for Mo alloying in steel
- 2011
-
Ingår i: Steel Research International. - : Wiley. - 1611-3683. ; 82:3, s. 269-276
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Tidskriftsartikel (refereegranskat)abstract
- Iron molybdate (Fe2MoO4) has been studied as a new potential precursor for Mo additions in high alloy steel processing. Fe2MoO4 was synthesized by high temperature reactions between MoO3, FeOx and carbon by holding the mixture first for 23 hours at 873K and then for 16 hours at 1373 K. The Fe2MoO4 syntheses were carried out with pure reagents as well as commercial grade materials supplied by steel industry. A thermodynamic analysis of the stabilities of the various phases in the Fe-Mo-O-C quaternary was carried out. The synthesis processes, leading to the Fe2MoO4 formation from the precursors and further reduction by carbon were studied with the aid of thermogravimetric analysis (TGA), high-temperature X-ray diffraction (HT-XRD) and evolved gas analysis by gas chromatography (GC). The maximum temperature in the case of all the experiments was 1373 K. It was found that the reactions between the precursor components start already above 873 K. The precursor mixture from commercial grade materials offers an economically advantageous process route with high Mo yield in steel.
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| 49. |
- Collin, T, et al.
(författare)
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FEM study of fatigue response of 3-sheet spot welded joints
- 2006
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Ingår i: Steel Research International. - : Wiley. - 1611-3683 .- 1869-344X. ; 4:77, s. 292-296
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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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| 50. |
- 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
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Ingår i: Steel Research International. - : Wiley-VCH Verlagsgesellschaft. - 1611-3683 .- 1869-344X. ; 87:9, s. 1137-1143
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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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