| 1. |
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| 2. |
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| 3. |
- Ahmed, Hesham, et al.
(författare)
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Isothermal reduction kinetics of self-reducing mixtures
- 2017
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Ingår i: Ironmaking & steelmaking. - : Taylor & Francis. - 0301-9233 .- 1743-2812. ; 44:1, s. 66-75
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Tidskriftsartikel (refereegranskat)abstract
- Isothermal reduction of haematite carbon mixtures was investigated at temperatures 750–1100°C under inert atmosphere. Mass loss curves proved the stepwise reduction of haematite to metallic iron. The non-linear feature of haematite to magnetite reduction kinetics was observed and an activation energy of 209 kJ mol−1 was calculated. Irrespective of carbon-bearing material type, reduction rate of magnetite was linear. Activation energy values were calculated to be 293–418 kJ mol−1. Significant increase in the reduction kinetics in the last step (Wustite reduction) was observed and explained by the catalytic effect of freshly formed metallic iron. During the initial stages of wustite reduction, the activation energy values were calculated to be in the range of 251–335 kJ mol−1 for all carbon-bearing materials.
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| 4. |
- Akhtar, Farid, et al.
(författare)
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A new kind of age hardenable martensitic stainless steel with high strength and toughness
- 2007
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Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 34:4, s. 285-289
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Tidskriftsartikel (refereegranskat)abstract
- Following analysis of typical age hardenable martensitic stainless steels, a new kind of maragingstainless was developed. The new maraging stainless steel showed high strength, ultimate tensilestrength (UTS) 5 1670 MPa, high toughness, K IC 5 83·9 MPa m1/2 and hardness as high as 478 HVin the age hardened condition. Microstructural study with an optical and transmission electron microscope revealed the typical microstructure of age hardenable stainless steel containing lathmartensite and precipitates. TixNi precipitates were identified by transmission electron microscopy, which were responsible for the increase in mechanical properties after age hardening. The results of natural salt spray test showed that the corrosion resistance of new maraging stainless steel approached to the corrosion resistance of 304L stainless steel.
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| 5. |
- Alriksson, Stina, 1971-, et al.
(författare)
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Steel industry environmental objectives:stakeholder preference assessment usingconjoint analysis
- 2013
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Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 40:8, s. 605-612
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Tidskriftsartikel (refereegranskat)abstract
- The Swedish steel industry has combined traditional methods such as life cycle analysis with less traditional methods such as preference analysis in order to move towards a closed steel eco cycle. The paper describes the use of conjoint analysis to study preferences of six different stakeholder groups regarding four environmental objectives (reduction in carbon dioxide emissions, reduced use of non-renewable resources, reduced use of non-renewable energy and weight reduction in products) and to identify gaps in preferences between the stakeholder groups. Our results suggested that there was a difference in preference between the stakeholder groups: respondents that were closer to the steel industry favoured all four environmental objectives, while members of public and political decision makers preferred a reduction in carbon dioxide emissions. One of the conclusions of our study is that there is a need of improved information to clients and public on the environmental benefits of product weight reduction.
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| 6. |
- Andersson, Annika J., et al.
(författare)
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Variation in hot metal and stag composition during tapping of blast furnace
- 2004
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Ingår i: Ironmaking & steelmaking. - : Informa UK Limited. - 0301-9233 .- 1743-2812. ; 31:3, s. 216-226
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Tidskriftsartikel (refereegranskat)abstract
- To determine the quality of the hot metal and the thermal conditions inside the blast furnace, the composition of the hot metal and slag must be known. Obtaining representative metal and slag samples during tapping is thus highly important to blast furnace operation. The study covered in the present report focused on hot metal and slag composition variation during tapping from a commercial blast furnace. From the results, optimal sampling time points for obtaining elemental concentrations that can be taken as representative for the whole tapping sequence were identified. It was furthermore concluded, that the reliability of hot metal composition data is significantly improved by averaging elemental concentrations determined from two samples, each taken at a particular time point. One sampling, however, was found to be adequate for slag. Results from the study also showed a fairly strong correlation between amounts of silicon and carbon, sulphur and carbon, and silicon and sulphur in the hot metal, while a weaker correlation between hot metal temperature and each of these elements was observed.
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| 7. |
- Andersson, Margareta A. T., et al.
(författare)
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Optimisation of ladle slag composition by application of sulphide capacity model
- 2000
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Ingår i: Ironmaking & steelmaking. - : Informa UK Limited. - 0301-9233 .- 1743-2812. ; 27:4, s. 286-293
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Tidskriftsartikel (refereegranskat)abstract
- The sulphur distribution ratio for ladle slags at Ovako Steel AB has been determined by calculating the sulphide capacity using the Royal Institute of Technology (KTH) model and the alumina activity via an empirical expression suggested by Ohta and Suite, and by using the well established theories for sulphur refining. A parameter study was carried out based on plant data from a previous study on desulphurisation, The effect of carbon and aluminium in the steel, the temperature of the steel, and alumina and lime in the slag on the sulphur distribution ratio was investigated, it was shown that the Al2O3/CaO ratio had the largest influence on the conditions studied, and that when it increased the sulphur distribution ratio decreased. Based on these results, new plant trials were carried out, in which the alumina content in the slag was changed. The calculated sulphur distribution ratios for these trials were found to be in good agreement with experimentally determined sulphur distribution ratios. It is concluded that the present approach can be used to optimise multicomponent ladle slags with respect to sulphur refining. I&S/1493.
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| 8. |
- Andersson, Margareta A.T., et al.
(författare)
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Slag-metal reactions during ladle treatment with focus on desulphurisation
- 2002
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Ingår i: Ironmaking & steelmaking. - : Informa UK Limited. - 0301-9233 .- 1743-2812. ; 29:3, s. 224-232
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Tidskriftsartikel (refereegranskat)abstract
- Within several cooperative projects, KTH (Royal Institute of Technology), Ovako Steel AB, and MEFOS have investigated the desulphurisation of bearing steel during vacuum degassing. The work includes thermodynamic calculations of the slag-metal equilibrium, CFD modelling of slag-metal reactions, and plant trials. Results from the various studies are presented and discussed in this paper. Models for predicting slag properties (sulphide capacity, viscosity, and oxide activities) in liquid slags as functions of slag composition and temperature have been used for the calculation of data which have been employed in static and dynamic modelling of sulphur refining. The results from static modelling show that the method allows fast and easy evaluation of the theoretical desulphurisation conditions during degassing at Ovako Steel AB, as well as theoretical determination of the parameters that have the greatest influence on the equilibrium sulphur distribution. The conclusion from dynamic modelling is that the vacuum degassing operation can be described dynamically with the present knowledge of sulphide capacity, sulphur distribution, viscosity, and oxide activities of ladle slags if this knowledge is combined with fluid flow modelling to derive the overall kinetics. The presented model approaches have been found useful in understanding the sulphur refining process at Ovako Steel AB. The dynamic modelling concept is also believed to have potential for dynamic descriptions of other slag-metal reactions in steelmaking.
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| 9. |
- Andersson, Nils, et al.
(författare)
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Fundamental decarburisation model of AOD process
- 2013
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Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 40:5, s. 390-397
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Tidskriftsartikel (refereegranskat)abstract
- A mathematical fluid flow model of gas injection in an argon–oxygen decarburisation (AOD) converter process has been coupled with a high temperature thermodynamic model. The current model is a further enhancement of an earlier developed three-dimensional, three-phase model, to also include some thermodynamics of the process. The model is based on fundamental transport equations and includes separate solutions for the steel, slag and the gas phases and their coupling by friction. The AOD model has been used to predict the first injection stage of decarburisation in an AOD converter. The predictions have been found to agree well with the corresponding results from an industrial process control model. One of the important observations from the simulations was that large concentration gradients of carbon exist in the AOD at an early stage and as the first injection step approaching its end the carbon gradients diminish. Also, the results show, in accordance with theory, that the local decarburisation rate is decreased at elevated pressures.
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| 10. |
- Andersson, Nils, et al.
(författare)
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Preliminary investigation of influence of temperature on decarburisation using fundamental AOD model
- 2013
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Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 40:7, s. 551-558
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Tidskriftsartikel (refereegranskat)abstract
- A high temperature thermodynamics model was earlier coupled with a fundamental mathematical model describing the fluid flow in an argon–oxygen decarburisation (AOD) converter and was initially validated for an idealised temperature description. More specifically, a linear average temperature relation was used such that the temperature would be isolated from other effects such as reactions and mixing. Thereafter, the effect of the starting temperature on the decarburisation was studied. The purpose is to provide some initial knowledge about how temperature affects the decarburisation in an AOD converter. The results suggest that the thermodynamic limit for carbon concentration after reaching the carbon removal efficiency (CRE) maxima is vertically translated downwards at higher temperatures. Furthermore, when plotting the mass ratio between CO and CO2, there is an indication of a point that may relate to a CRE maximum.
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| 11. |
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| 12. |
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| 13. |
- Andersson, Stig Peter, et al.
(författare)
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Thermal conductivity of powders used in continuous casting of steel part 1 : Glassy and crystalline slags
- 2015
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Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 42:6, s. 456-464
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Tidskriftsartikel (refereegranskat)abstract
- Measurements of the thermal conductivity (λ) and thermal diffusivity (α) have been carried out on samples of Na2O·SiO2 and four mould slags for temperatures between 295 and 1300 K. These measurements were carried out using the transient plane source (TPS) method (295-373 K) and the transient hot wire (THW) technique (295-1300 K) and the laser pulse (LP) or laser flash method in the case of Na2O·SiO2 Values of l295 were very similar (1.07±0.03 W m-1 K-1) and all samples exhibited a maximum at the critical temperature (Tcrit 51040±10 K) beyond which there was a sharp drop in λTHW with increasing temperature. Measurements were also carried out on semi-crystalline samples with increasing λ and fraction of crystalline phase. These samples also exhibited a sharp drop in the thermal conductivity for temperatures above Tcrit and λTcrit was found to be 1.6±0.05 W m-1 K-1. Thermal conductivity (λLP) values calculated from reported thermal diffusivity (αLP) values were in very good agreement with the measured λTHW values for temperatures between 295 K and Tcrit but λLP values did not decrease with increasing temperature above Tcrit (cf. λTHW). Consequently, it was found that λLP≈7λTHW for mould slags.
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| 14. |
- Andersson, Stig Peter
(författare)
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Thermal conductivity of powders used in continuous casting of steel part 2 : Powders
- 2015
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Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 42:6, s. 465-470
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Tidskriftsartikel (refereegranskat)abstract
- Measurements of the thermal conductivity of casting powders are needed to determine the magnitude of the vertical heat flux in the powder bed of a continuous casting mould. The thermal conductivities and thermal diffusivities of four mould powders have been determined using the transient plane source (TPS) and the transient hot wire (THW) methods. The values reported in this investigation are in good agreement with the results of earlier studies which used the THW method. However, the results were significantly different from λeff values obtained in thermal insulation tests. This was attributed to the large contribution to λeff from gaseous conduction which arises from the large temperature gradient across the sample. It was found that the thermal conductivity (λpowd) of the powders had a mean value of 0.125±0.025 W m-1 K-1 for the four powders studied; this value is in good agreement with two other studies; it increased as the temperature increased with a mean temperature coefficient of (dλ/dT59×10-5 W m-1 K-2 for the range 295-1100 K and increased as the bulk density increased (λ295=0.010+1.69×10-4ρbulk W m-1 K-1).
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| 15. |
- Aune, Ragnhild E., et al.
(författare)
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Thermodynamic approach to physical properties of silicate melts
- 2005
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Ingår i: Ironmaking & steelmaking. - : Informa UK Limited. - 0301-9233 .- 1743-2812. ; 32:2, s. 141-150
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Tidskriftsartikel (refereegranskat)abstract
- The thermophysical properties of silicate melts are strongly structure dependent. It is well known that the viscosity of slags increases with increasing degree of polymerisation of the silicate anion. Even the thermodynamic properties of slags are dependent on the species type and population in the melt. Thus, a link between the thermophysical and thermochemical properties of silicate melts is logically expected. The present paper elucidates the salient features of Darken's excess stability approach to the Gibbs energy of solution as applied to the viscosities of silicate melts. It is demonstrated that the second derivatives of the viscosities of binary silicate melts with respect to composition indicate maxima corresponding to the existence of stable compounds in these systems. The concept has been successfully applied to the following systems: Al2O3-SiO2, CaO-SiO2, FeO-SiO2, MgO-SiO2 and MnO-SiO2. In all cases, the second derivative plots of viscosities with respect to composition show peaks corresponding to the metasilicates. The second derivatives of the activation energies of viscous flow with respect to temperature have earlier been shown to reflect the formation of associates/embryos in homogeneous silicate melts, indicating the readiness of the melt to separate a solid phase. Thermodynamic coupling of thermal diffusivities in the case of the CaO-Al2O3-SiO2 system from laser flash measurements of these slags, as a function of temperature, has been examined as part of the present study. Densities have been estimated from integral molar enthalpies in the case of silicate systems, and the results are presented.
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| 16. |
- Bai, Haitong, 1986-, et al.
(författare)
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Effect of swirling flow tundish submerged entry nozzle outlet design on multiphase flow and heat transfer in mould
- 2019
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Ingår i: Ironmaking & steelmaking. - : TAYLOR & FRANCIS LTD. - 0301-9233 .- 1743-2812.
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Tidskriftsartikel (refereegranskat)abstract
- Effect of a swirling flow SEN (submerged entry nozzle) outlet design on the multiphase flow and heat transfer in a mould was investigated by using numerical simulation. It was found that different SEN outlet designs could form different flow patterns and temperature distributions on the upper of the mould. The enlarged outlet SEN design had an effect to decrease the horizontal velocity of liquid steel flowing out the SEN outlet, reducing the steel flow velocity towards the solidification front. Although a higher velocity was found near the slag/steel interface with the enlarged outlet SEN, but the turbulent kinetic energy was lower. The reason was that less circulation flows were formed in the region of the mould top. The weak horizontal flow towards the solidification front with the enlarged outlet SEN induced lower wall shear stresses, at the same time it also formed a lower temperature distribution near the solidified shell.
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| 17. |
- Bai, Haitong, 1986-, et al.
(författare)
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Numerical study of an application of a divergent reverse TurboSwirl nozzle in the billet continuous casting process
- 2019
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Ingår i: Ironmaking & steelmaking. - : TAYLOR & FRANCIS LTD. - 0301-9233 .- 1743-2812. ; 46:2, s. 148-158
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Tidskriftsartikel (refereegranskat)abstract
- The swirling flow has widely been investigated for liquid steel flowing in the continuous casting process. In this paper, a new design of the submerged entry nozzle (SEN) is applied by using a reverse TurboSwirl device with a divergent nozzle. This divergent reverse TurboSwirl nozzle (DRTSN) is shown to gain a more beneficial flow pattern compared to the straight nozzle. A stronger swirling flow can be obtained at the SEN outlet, which leads to a calmer flow field and an appropriately active meniscus flow that could improve the heat and mass transfer near the meniscus. The swirl number in the SEN is independent of the casting speed, while a lower casting speed yields a lower maximum wall shear stress. The DRTSN is connected to the tundish by an elbow and a horizontal runner. A longer horizontal runner supplies a more uniform velocity profile and a more symmetrical flow pattern.
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| 18. |
- Beheshti, Reza, et al.
(författare)
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Reduction kinetics of commercial haematite pellet in a fixed bed at 1123-1273 K
- 2016
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Ingår i: Ironmaking & steelmaking. - : Taylor & Francis. - 0301-9233 .- 1743-2812. ; 43:5, s. 394-402
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Tidskriftsartikel (refereegranskat)abstract
- In the present study a model for future use in the modelling of moving bed direct reduction reactors has been developed. The model of a fixed bed reactor for the production of sponge iron from haematite incorporates both heat-and mass-transfer, as well as the chemical reduction rate. The model results were compared to the experimental data obtained from a lab scale reactor in the temperature range 1123-1273 K, as well as to the output from a simple model assuming isothermal conditions. The H-2/CO ratio (beta) of the reducing gas was in all cases varied from 0.8 to 2.0. Overall the non-isothermal model developed permits a more accurate representation of the experimental data than the isothermal estimates, with a typical discrepancy of only 1.3%.
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| 19. |
- Beheshti, Reza, et al.
(författare)
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Reduction of commercial hematite pellet in isothermal fixed bed-experiments and numerical modelling
- 2016
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Ingår i: Ironmaking & steelmaking. - : Taylor & Francis. - 0301-9233 .- 1743-2812. ; 43:1, s. 31-38
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Tidskriftsartikel (refereegranskat)abstract
- In the present work, fixed bed reduction experiments were conducted at 1173 K over a range of H-2/CO ratios from 0.8 to 2.0 and subsequently modelled numerically (R). The model consists of two one-dimensional, isothermal and time dependent models. The gas-solid reactions were kinetically modelled using a modified shrinking core approach, and the equations were solved using the commercial software COMSOL Multiphysics H. The simulation results agree with thermal gravity experimental data with an average difference of 2.5%. A sensitivity analysis was conducted using the numerical model to establish the optimum operational conditions. The effects of the reducing gas ratio and flow rate, pellet radius and porosity, and the total bed height on the overall degree of reduction were also investigated.
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| 20. |
- Beskow, Kristina, et al.
(författare)
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A new approach for the study of slag-metal interface in steelmaking
- 2006
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Ingår i: Ironmaking & steelmaking. - : Informa UK Limited. - 0301-9233 .- 1743-2812. ; 33:1, s. 74-80
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Tidskriftsartikel (refereegranskat)abstract
- The main focus of the present work was to develop a sampler to obtain the physical description of the slag-metal interface in the presence of bulk flow. Industrial trial experiments were carried out in the ladles at Uddeholm Tooling, Hagfors, Sweden using the designed sampler. Samples of the slag-metal interface were successfully taken in both gas stirring and induction stirring modes. The similarities of the appearance as well as the micrographs of the samples suggested that the slag-metal interfaces in the two stirring modes were very similar except in the open eye area. In the case of both stirring modes, metal droplets were found in the slag bulk. On the other hand, no appreciable amount of slag was detected in the metal bulk. Further systematic investigation using a large number of samples is required to obtain a quantitative description of the interface.
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| 21. |
- Beskow, Kristina, et al.
(författare)
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A new approach for the study of slag-metal interface in steelmaking
- 2006
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Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 33:1, s. 74-80
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Tidskriftsartikel (refereegranskat)abstract
- The main focus of the present work was to develop a sampler to obtain the physical description of the slag-metal interface in the presence of bulk flow. Industrial trial experiments were carried out in the ladles at Uddeholm Tooling, Hagfors, Sweden using the designed sampler. Samples of the slag-metal interface were successfully taken in both gas stirring and induction stirring modes. The similarities of the appearance as well as the micrographs of the samples suggested that the slag-metal interfaces in the two stirring modes were very similar except in the open eye area. In the case of both stirring modes, metal droplets were found in the slag bulk. On the other hand, no appreciable amount of slag was detected in the metal bulk. Further systematic investigation using a large number of samples is required to obtain a quantitative description of the interface. © 2006 Institute of Materials, Minerals and Mining.
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| 22. |
- Beskow, Kristina, et al.
(författare)
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Impact of slag-refractory lining reactions on the formation of inclusions in steel
- 2004
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Ingår i: Ironmaking & steelmaking. - : Informa UK Limited. - 0301-9233 .- 1743-2812. ; 31:6, s. 514-518
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Tidskriftsartikel (refereegranskat)abstract
- The present study was carried out to investigate the impact of slag-refractory lining reactions on the formation of inclusions during ladle treatment of steel. The experiments were conducted on an industrial scale in the ladle at Uddeholm Tooling AB in Hagfors, Sweden. The inclusion chemistry and population during ladle treatment were studied along with the composition of the ladle glaze, taken from the ladle lining. The inclusions in the steel were classified into four groups according to the Swedish standard SS 111116. SEM/EDS analyses were carried out to identify the phases present in both the inclusions and the ladle glaze. The number of inclusions in the steel before deoxidation was found to increase with the ladle age, i.e. the number of times the ladle had been in use. A similar increase was also found after vacuum degassing and before casting. A great portion of inclusions before casting was found to be supplied by ladle glaze. This observation was further confirmed and explained by thermodynamic analysis. The present results show that ladle glaze is a major source of inclusions in the ladle at Uddeholm Tooling.
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| 23. |
- Beskow, Kristina, et al.
(författare)
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Ladle glaze : major source of oxide inclusions during ladle treatment of steel
- 2004
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Ingår i: Ironmaking & steelmaking. - : Informa UK Limited. - 0301-9233 .- 1743-2812. ; 31:5, s. 393-400
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Tidskriftsartikel (refereegranskat)abstract
- Samples of ladle lining covered by glaze were taken from industrial ladles of different ages at Uddeholm Tooling AB, Hagfors, Sweden. It was found in the samples taken at and below the slag line that a slag infiltrated layer was covered by an outer layer containing many MgO 'islands' of various sizes. The microstructure of the infiltrating slag was the same as the matrix of the outer layer. The slag was found to decompose into the compound 3CaO. Al2O3 and a liquid phase during the cooling process. The former phase along with tiny MgO particles from the ladle glaze was found to be one of the major sources of inclusions during the degassing and flotation periods of ladle treatment. Thermodynamic analysis indicated that the reaction between the ladle glaze and the slag from the electric arc furnace resulted in the formation of MgO-Al2O3 spinel and an oxide solution, which were also the main inclusions found at the initial stages of ladle treatment. Evidence of this reaction was found in the lining samples taken above the slag line.
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| 24. |
- Bi, Yanyan, et al.
(författare)
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Investigations of inclusions in ferrochromium alloys
- 2014
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Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 41:10, s. 756-762
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Tidskriftsartikel (refereegranskat)abstract
- Ferrochromium alloys are commonly added during different stages of steelmaking processes according to the specific steel grade being produced. Depending upon the ferrochromium quality, the addition can also lead to a supply of deleterious inclusions to the liquid steel. Therefore, the number, size, morphology and composition of inclusions in LCFeCr and HCFeCr alloys were investigated. The alloy samples were first treated with electrolytic extraction, followed by filtration to gather the inclusions on a film filter. Thereafter, the characteristics of the inclusions and clusters were investigated in three dimensions by SEM in combination with energy dispersive spectroscopy. The results show that the main inclusion types found in LCFeCr alloys are different to those found in HCFeCr alloys. More specifically, the inclusions in LCFeCr alloys were found to consist of Si-Cr-O and Cr-O oxides as well as intermetallic Cr-Fe inclusions. Moreover, the inclusions in HCFeCr alloys were found to consist of Cr-Mn-S, Cr-C-N, Si-Al-Ca-Mg-O and Ca-O-P inclusions. Overall, the inclusions can be divided into two categories depending on the melting point. Furthermore, the possible transformation of different inclusions after their addition to the liquid steel is discussed.
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| 25. |
- Bjorkvall, J., et al.
(författare)
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Thermodynamic model calculations in multicomponent liquid silicate systems
- 2001
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Ingår i: Ironmaking & steelmaking. - : Informa UK Limited. - 0301-9233 .- 1743-2812. ; 28:3, s. 250-257
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Tidskriftsartikel (refereegranskat)abstract
- A thermodynamic model developed earlier in the present laboratory for oxidic melts was applied to some multicomponent systems, namely CaO-FeO-MgO-SiO2, Al2O3-CaO-MgO-SiO2, Al2O3-FeO-MnO-SiO2, and Al2O3-CaO-FeO-MgO-MnO-SiO2. Model calculations were carried out using only the parameters corresponding to the binary systems, which, in turn, were based on the available thermodynamic information for these systems. The predicted thermodynamic activities of the component oxides in higher order systems were compared with the experimental data published in the literature. In general, the agreement between the model predictions and the experimental values was found to be satisfactory within the limits of experimental uncertainties and limitations of the model calculations. Examples of model predictions for some typical slag compositions, relevant to the Swedish steel industry and used in the blast furnace, electric arc furnace, and ladle furnace are also presented.
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| 26. |
- Björklund, Johan, et al.
(författare)
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Equilibrium between slag, steel and inclusions during ladle treatment : comparison with production data
- 2007
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Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 34:4, s. 312-324
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Tidskriftsartikel (refereegranskat)abstract
- The primary purpose of the investigation was to determine whether equilibrium conditions exist between slag and steel and inclusions and steel after silicon deoxidation and aluminium deoxidation. In doing so, the performance of three different models for predicting oxide component activities was also evaluated. The results from the oxide activity models were used to calculate oxygen activities in the steel melt. Industrial data such as steel, slag and inclusion component concentrations, as well as temperature, were used as input to the calculations. One general conclusion drawn was that although the results from the different models showed similar trends, the models did not predict the same actual values for specific calculations. Predicted theoretical equilibrium oxygen activity values were compared with plant measurements of oxygen activity. Here, it was found that the oxygen activity values pertaining to the equilibrium between steel and inclusions were higher than corresponding measured values. The calculations for the equilibrium between the top slag and steel melt, however, resulted in theoretical oxygen activity values considerably lower than corresponding measurements. It was thus concluded that equilibrium conditions did not exist between the top slag and the steel bulk with respect to oxygen. Overall, the models proved useful in predicting oxide activities, but the lack of equilibrium between top slag and molten steel made the calculation of oxygen activity difficult.
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| 27. |
- Brandberg Hurtig, Jenny, et al.
(författare)
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Hydrogen pick-up after vacuum degassing
- 2015
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Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 42:1, s. 49-54
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Tidskriftsartikel (refereegranskat)abstract
- The present work aimed at determining the major source for hydrogen pick-up of the steel after vacuum degassing but before casting. Samples of slag and metal were taken at different stages during ladle treatment at SSAB. Hydrogen increase after vacuum treatment was observed. Moisture contents of the industrial slags were analysed and their water capacities were calculated. It could be seen that the hydrogen increase was correlated to the amount of moisture in the slag and the water capacity. The study showed that the slag containing most water was also the heat having the largest hydrogen increase. The slag with most water had the highest water capacity. It could be concluded that the major source for hydrogen increase after degassing was due to the slag-metal reaction.
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| 28. |
- Cheng, J., et al.
(författare)
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Determination of macroinclusions during clean steel production
- 2003
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Ingår i: Ironmaking & steelmaking. - : Informa UK Limited. - 0301-9233 .- 1743-2812. ; 30:1, s. 66-72
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Tidskriftsartikel (refereegranskat)abstract
- There are very few macroinclusions in clean steel, but the few that exist are very harmful for material properties of the final steel product. To date, very little information on large, so called macroinclusions in clean steel production has been presented. Therefore, the present study has focused on providing information on these inclusions during different stages of the steelmaking process, based on plant trials carried out at Uddeholm Tooling, Hagfors, Sweden. Macroinclusion size distributions have been determined using optical microscopy and classified according to a modified version of the Swedish standard SS 111116, as well as using immersed ultrasonic scanning. For the sake of completeness, the size distribution of microinclusions has also been determined using optical microscopy. Inclusion compositions were determined using a scanning electron microscope (SEM) equipped with energy dispersive spectroscopy (EDS). Two types of liquid steel sampler were used in the investigation: a rapid solidifying (RS) sampler and the LSHR (liquid sampling hot rolling) sampler, suitable for immersed ultrasonic scanning. The results are critically discussed with respect to process conditions, such as alloy additions that took place during the plant trials.
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| 29. |
- Condo, Adolfo Firmino Timoteo, 1976-, et al.
(författare)
-
Experimental Determination of Sulphide Capacities of Blast Furnace Slags with Higher MgO Contents.
- 2017
-
Ingår i: IRONMAKING & STEELMAKING. - : Taylor & Francis. - 0301-9233 .- 1743-2812.
-
Tidskriftsartikel (refereegranskat)abstract
- Sulfide capacity measurements of slag with MgO content up to 18 mass% were carried out at 1713, 1743 and 1773 K to obtain reliable data for the blast furnace process. In the measurement, slag is equilibrated with copper at controlled oxygen partial pressure for 24h. The sulfide capacities are calculated based on the sulfur analyses for both slag and copper.
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| 30. |
- Dahlin, Anders, et al.
(författare)
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Influence of ladle slag additions on BOF process performance
- 2012
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Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 39:5, s. 378-385
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Tidskriftsartikel (refereegranskat)abstract
- A plant trial has been performed, with recycling of ladle slag to the LD converter at SSAB EMEA, Lulea, Sweden. The effect of ladle slag addition on the slag and steel composition, together with the slag weight, was investigated with sampling both during the blow and at blow end. The addition of ladle slag resulted in an increase in slag weight between 1 and 2 t throughout the blow and an increase of 3 wt-% in the slag Al2O3 content. This indicated that the ladle slag melted during the initial stages of the blow and enhanced the early slag formation. Lime additions were reduced with 3.5 kg t(-1) liquid steel without drawbacks on the phosphorus or sulphur refining. Heats with added ladle slag had an increase in blowing time with similar to 4% and an increased tendency for slopping. However, this can be handled by different lance and addition programmes.
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| 31. |
- Dahlin, Anders, et al.
(författare)
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Influence of ladle slag additions on BOF process under production conditions
- 2012
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Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 39:5, s. 318-326
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Tidskriftsartikel (refereegranskat)abstract
- The influence of recycled ladle slag on the basic oxygen furnace (BOF) process under production conditions was investigated in plant trials. More specifically, 25 heats with ladle slag additions and 23 heats without ladle slag additions were studied. Both steel and slag samples were collected, from which the chemical compositions were determined. In addition, several process parameters were monitored. Overall, it was found that recirculation of ladle slag during normal production conditions works fine. On the positive side, it was seen that the steel quality concerning the phosphorus and sulphur contents of liquid steel has, in accordance with previous studies, not been affected by the ladle slag additions. Furthermore, no major differences in the slag composition occur when the recycling of ladle slag to BOF is performed. Finally, in comparison to previous studies, the increased tendency for slopping when adding ladle slag could be eliminated with a change in the lance schedule. However, on the negative side, it was seen that the addition of ladle slag leads to an increased blowing time due to lower iron ore additions. Moreover, the slag weight at tapping increased due to an increased weight of added slag formers.
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| 32. |
- Dayal, P., et al.
(författare)
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Study of slag/metal interface in ladle treatment
- 2006
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Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 33:6, s. 454-464
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Tidskriftsartikel (refereegranskat)abstract
- In order to gain an insight into the mixing behaviour of slag and metal under different stirring conditions, samples of slag/metal interface were collected from an industrial 65 ton ladle furnace using a new sampling technique. Different stirring conditions and sampling positions in the ladle were chosen. Complementary cold model experiments were also performed. The experimental results strongly suggested that the shear force between the two liquids played an important role in slag-metal mixing. Evidence for the existence of slag droplets each surrounded by a very thin metal film was found in the samples taken under both gas stirred and induction stirred conditions. This observation strongly suggested that slag-metal system behaved similarly as oil-water system, wherein, the shear force owing to the bulk flow led to a packed 'sphere bed' of oil droplets each coated by a thin water film above the water bath. On the basis of the experimental results, preliminary mathematical models were developed to describe the rate of mass exchange at the slag/metal interface. © 2006 Institute of Materials, Minerals and Mining.
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| 33. |
- Dayal, P., et al.
(författare)
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Study of stag/metal interface in ladle treatment
- 2006
-
Ingår i: Ironmaking & steelmaking. - : Informa UK Limited. - 0301-9233 .- 1743-2812. ; 33:6, s. 454-464
-
Tidskriftsartikel (refereegranskat)abstract
- In order to gain an insight into the mixing behaviour of slag and metal under different stirring conditions, samples of slag/metal interface were collected from an industrial 65 ton ladle furnace using a new sampling technique. Different stirring conditions and sampling positions in the ladle were chosen. Complementary cold model experiments were also performed. The experimental results strongly suggested that the shear force between the two liquids played an important role in slag-metal mixing. Evidence for the existence of slag droplets each surrounded by a very thin metal film was found in the samples taken under both gas stirred and induction stirred conditions. This observation strongly suggested that slag-metal system behaved similarly as oil-water system, wherein, the shear force owing to the bulk flow led to a packed 'sphere bed' of oil droplets each coated by a thin water film above the water bath. On the basis of the experimental results, preliminary mathematical models were developed to describe the rate of mass exchange at the slag/metal interface.
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| 34. |
- Deng, Tengfei, et al.
(författare)
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Dissolution mechanism of dolomite in converter slag at 1873K
- 2014
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Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 41:1, s. 75-80
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Tidskriftsartikel (refereegranskat)abstract
- The mechanism of dolomite dissolution in converter slag was studied and found to proceed by two steps: decomposition of dolomite into CaO and MgO and dissolution of the product into the slag. The first step was found to be controlled by heat transfer, which was confirmed by theoretical calculation. The decomposed dolomite had many pores, which allowed easy slag penetration. A discontinuous 2CaO.SiO2 layer along with MgO.Fe2O3 particles was found on the surface of the samples. Some 2CaO.SiO2 islands were found in the vicinity of the samples in the slag, revealing that the dissolution was dominated by peeling-off of the layer of 2CaO.SiO2- MgO.Fe2O3 mixture. 2CaO.SiO2, (Mg, Fe)Oss along with super cooled liquid phases were found inside dolomite samples close to the surface. 2CaO.SiO2 phase was replaced gradually by 3CaO.SiO2 towards the centre of the decomposed sample. While addition of small amounts of dolomite directly into the slag could be considered in steelmaking converter, too much would result in slow dissolution and waste of the raw materials.
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| 35. |
- Ek, Mattias, et al.
(författare)
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A new approach towards dynamic modelling of dephosphorisation in converter process
- 2012
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Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 39, s. 77-84
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Tidskriftsartikel (refereegranskat)abstract
- A new approach was made to model the dephosphorisation process in a 300 tons basic oxygen furnace converter with three argon gas inlets. The main feature of the new approach was to utilise the velocity vectors obtained by computational fluid dynamics (CFD) simulation in a standalone model. The CFD simulation was carried out using commercial software COMSOL Multiphysics. In the standalone model, the steel melt domain was sliced into 1000 cells. The calculated velocity vector in each cell was assumed constant. Based on the imported velocity vectors from the CFD calculation, the mass transfer of carbon and phosphorus was calculated by taking into account the slag-metal reactions. The mass exchange between slag and metal was considered to be dominated by the metal droplet formation due to the oxygen jet. The convergence of the model calculation and the promising comparison between the model prediction and the industrial data strongly suggested that the proposed approach would be a powerful tool in dynamic process control. As a preliminary step, the model only simulated the process after the formation of slag-metal-gas emulsion. Note that the present work is intended to establish a structure of the model. More precise descriptions of other process aspects need to be included before the model can be practically employed in a dynamic controlling system.
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| 36. |
- Ek, Mattias, et al.
(författare)
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Capacities of some CaO-SiO2-FeO-MnO-MgO slags and slag-solid mixtures in capturing phosphorous
- 2013
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Ingår i: Ironmaking & steelmaking. - : Maney Publishing. - 0301-9233 .- 1743-2812. ; 40:4, s. 305-311
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Tidskriftsartikel (refereegranskat)abstract
- Slag is of great importance for dephosphorisation in converter steelmaking. In the present study, slag samples were equilibrated with copper at 1923 K to study their capacities in capturing phosphorous. The phosphate capacities of the slags were calculated. Some of the samples were liquid-solid mixtures. The solid phases in these samples were identified by SEM analysis, and the identified phases were found to agree well with Thermocalc calculations. On the other hand, the fractions of the solid phase did not agree with the Thermocalc calculation. Phosphorous distributions in the different phases were examined, and the phosphate capacities of the samples were evaluated. The MgO content did not show any appreciable impact on the phosphate capacity. The activities of FeO in the pure liquid slag samples were calculated and found to deviate positively from ideality.
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| 37. |
- Ekengard, J., et al.
(författare)
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Distribution of metal droplets in top slags during ladle treatment
- 2008
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Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 35:8, s. 575-588
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Tidskriftsartikel (refereegranskat)abstract
- The investigation focused on the mixing of the metal and slag phases during ladle refining from the point of tapping the EAF to casting. Steel droplet distributions were determined for slag samples taken at different stages in the ladle refining process at two different steel plants in Sweden. The droplet distributions were determined using light optical microscopy and classification according to the standard SS111116. Sample analysis results showed the slag samples taken before vacuum degassing to contain the greatest concentration of steel droplets. The total interfacial area between the steel droplets and slag was determined to be 3-14 times larger than the projected flat interfacial area between the steel and slag. The effects of slag viscosity and reactions between steel and slag on metal droplet formation in slag were also considered.
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| 38. |
- El-Bealy, Mostafa Omar
(författare)
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Spray cooling pattern and microthermomechanical rigidity criterion for improving inner quality in continuously cast steel slabs
- 2013
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Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 40:3, s. 167-188
-
Tidskriftsartikel (refereegranskat)abstract
- A new concept has been developed to assess, and a new technique developed to improve, the microthermomechanical rigidity of the solidifying shell in the secondary cooling zones during continuous casting of steel. This is to maximise the coherent solid shell resistance 'I-c' against thermometallurgical and mechanical stresses at different levels from meniscus. The idea behind this concept is to optimise the degree of homogeneity of the cooling pattern between a pair of rolls. The effect of the degree of homogeneity of the cooling pattern between a pair of rolls 'HDCP', in different spray cooling zones on the different types of centreline segregates has been investigated. A number of plant trials with two different water cooling patterns between a pair of rolls have been performed. The metallographic investigation contains examinations and measurements of the level of centreline segregates of collected samples. A one dimensional (1D) transient finite difference mathematical model of thermal, solidification, solid shell resistance and cooling conditions has been developed to test the different effects of spray patterns on the microthermomechanical rigidity concept and therefore on the mechanism of centreline macrosegregation level. The results indicate that the increase in the degree of homogeneity of the cooling conditions is proportional to the increase in slab internal microquality. The results show that the degree of homogeneity of the cooling pattern affects centreline macrosegregation significantly. This depends significantly on the degree of homogeneity of cooling pattern between a pair of rolls, its location from the meniscus and, generally, on the increase microthermomechanical rigidity concept.
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| 39. |
- Eliasson, Elin, et al.
(författare)
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Formation of potassium slag in olivine fluxed blast furnace pellets
- 2007
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Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 34:5, s. 422-430
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Tidskriftsartikel (refereegranskat)abstract
- Mineralogical evaluation of olivine pellets coated with kaolinite, taken from the LKAB experimental blast furnace, shows significant reactions with potassium. Sampling has revealed strong potassium deposition in pellets in the lower shaft close to the wall, but much less deposition towards the furnace centre. Iron reduction and the deformation of the pellets were enhanced in the zone of high alkali deposition. Thin sections of pellet samples were prepared to distinguish amorphous and crystalline slag phases for a better understanding of the formation of the potassium rich slag. Olivine breaks down to various extents to form a SiO2-FeO-MgO-K2O glass. The kaolinite coating shows strong reaction throughout the cross-section of the lower shaft to form kalsilite (KAlSiO4) and K2O rich glassy slag. Studies of thin sections of the slag products were shown to be very useful in separating amorphous phases such as the K2O rich glass from the crystalline olivine rim.
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| 40. |
- Eriksson, Conny, et al.
(författare)
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Working range of roll pass sequences in wire rod rolling with interstand tensions
- 2004
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Ingår i: Ironmaking & steelmaking. - : Informa UK Limited. - 0301-9233 .- 1743-2812. ; 31:1, s. 81-92
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Tidskriftsartikel (refereegranskat)abstract
- In the high speed rolling of wire rod in blocks, interstand tensions are utilised in order to keep the process stable. However, interstand tensions influence the rolling process, and especially the spread and forward slip, which are dependent of tensions between the stands. By the influence on spread, the tolerances of the rolled product depend on the tensions and usually the interstand tensions are kept as low as possible in order to obtain required tolerances. A narrow spread technology is used to utilise interstand tensions in order to increase the working range of a pass sequence and move the product range towards smaller sizes. By adapting a certain amount of interstand tensions, smaller sizes can be rolled by a given roll pass schedule. A practical problem in this method is the fixed gearings in the common blocks, which require a certain and given level of interstand tensions and corresponding reductions. In the latest generation of blocks, where the stands are arranged in units, two by two, with each unit driven by a dedicated electrical motor, it is possible to introduce 'inter unit' tensions, and by this method extend the working range of the pass sequence. A special computer program for analysis of interstand tensions has been developed by combining a program TENSION, developed at the Royal Institute of Technology in Stockholm, dealing with the basic principles of rolling with interstand tensions, with the recently published program WORKRAN, which analyses the working range of any roll pass sequence built up by common two-symmetrical grooves. From the analysis and experimental data it is shown that interstand tensions at the level of 10% of the yield stress of the material increase the working range in a six stand block by 2% and reduce the lower limit of the exit section area by about 15%. Higher tension levels have a larger effect both on the extension of the working range and on the reduction of the minimum exit area but it becomes more difficult to control the tolerances at higher tension levels. The influence of interstand tensions on the reduction and on the working range of the pass sequence is mainly obtained by the influence on the round passes, while the oval passes have a counteracting effect on the influence of interstand tensions
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| 41. |
- Fredriksson, Patrik, et al.
(författare)
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Thermodynamic studies of stags containing FeO and their impact on ladle refining process
- 2005
-
Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 32:1, s. 47-53
-
Tidskriftsartikel (refereegranskat)abstract
- In the ladle refining process, the FeO content of the ladle slag is of great importance in the chemistry as well as the energetics of the process. Optimisation of the process requires an accurate knowledge of the thermodynamic activities of FeO in the ladle slags. Due to the discrepancies in existing data, renewed attempts are being made at the Royal Institute of Technology to generate reliable data for binary, ternary and multicomponent slags containing FeO at steelmaking temperatures. In order to measure the activities of FeO in the slags, a gas equilibration technique was employed in the present work. The slags, kept in Pt crucibles were equilibrated with a CO-CO2-Ar gas mixture and quenched after equilibration. The chemical composition of the slag was analysed. From knowledge of the thermodynamics of the Fe-Pt system, the 'FeO' activities in the slag were evaluated. The results of the present studies, together with other literature values, were optimised in the slag software THERMOSLAG developed at the Royal Institute of Technology, Sweden. The results of the optimisation are presented. Model calculations were performed with the KTH slag software THERMOSLAG using plant data from Ovako Steel, Hofors, Sweden. It was found that oxygen estimations in the metal from the FeO analyses of slags, obtained by a conventional sampling and analysis method were less reliable. Estimation of the oxygen levels utilising the sulphur partition between the slag and the metal were carried out using the THERMOSLAG software. Reasonable estimations of the oxygen content in the metal confirmed that this could be a very useful tool for the plant operator.
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| 42. |
- Gauffin, Alicia, et al.
(författare)
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Use of volume correlation model to calculate lifetime of end-of-life steel
- 2015
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Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 42:2, s. 88-96
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Tidskriftsartikel (refereegranskat)abstract
- A new mathematical model for calculating the lifetime of steel on an annual basis, called the volume correlation model is presented. The model compares the quantities of scrap collection with the steel consumption as well as evaluates the time difference between the two data sets. The lifetime of steel was calculated for the collected end-of-life steel amounts. The calculations were performed by assuming a full recovery of the steel consumption or a non-re-circulated accumulated steel stock in society denoted the full and true lifetime of steel. Based on the volume correlation model, the lifetime of steel was calculated for the total steel, low alloyed and special steel, and stainless steel in Sweden between 1898 and 2010. Previous studies on the lifetime of steel are based on experimental measurements and numerical calculations. The full lifetime of the total amount of steel from previous studies is 31 and 35 years for the years 2000 and 2006 respectively. Based on the volume correlation model the lifetime for the total steel amount, when assuming a full recovery of the material, was calculated as 34 and 37 years for these two years. This indicates that the lifetime of steel from the volume correlation model is in a similar range, but slightly higher, compared to previously reported data. The present results show that the model could be an alternative method to calculate the lifetime of steel and other recyclable materials on an annual basis. Results show that the lifetime of the total steel amount has continuously increased between 1975 and 2010. This indicates that the accumulated steel stock in society is still large enough to withstand the high collection rate of steel scrap. Furthermore, that there are as yet no lack of untapped resource of end-of-life steel scrap assets in Swedish society.
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| 43. |
- Gran, Jimmy, et al.
(författare)
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Effects of slag composition and cooling rate on formation of glaze on MgO refractory
- 2010
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Ingår i: Ironmaking & steelmaking. - : Informa UK Limited. - 0301-9233 .- 1743-2812. ; 37:1, s. 27-34
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Tidskriftsartikel (refereegranskat)abstract
- The formation of a slag glaze layer on dense and porous MgO rods was studied by dipping MgO rods into liquid slag at 1873 K and thereafter cooling the rods at a predetermined cooling rate. Three different slag compositions and three different cooling rates were employed. It was found that the phases formed upon cooling were mostly dependent on slag composition and to a minor extent on the cooling rate. The initially liquid slag was transformed into crystalline phases for all the samples except the ones terminated at 1573 K and one of the samples with high cooling rate. In addition, the three slags were equilibrated at 1773, 1673 and 1573 K in order to get an understanding of the equilibrium phases and their relationship during cooling. On the basis of the experimental results, the mechanism regarding entrainment of exogenous inclusions from the refractory lining was also discussed.
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| 44. |
- Grip, Carl-Erik
(författare)
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Steel and sustainability : Scandinavian perspective
- 2005
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Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 32:3, s. 235-241
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Tidskriftsartikel (refereegranskat)abstract
- A description is given of practice at the steelplant of SSAB Tunnplat AB in Lulea, Sweden, and of progress in the recycling of residuals and reducing environmental impact. An extensive study of greenhouse gases in steel production to slabs was carried out by SSAB during the years 2000-02. Current and new processes and possible alternatives were studied, as well as the effect of the product programme. Various emission alternatives were considered using a global calculation (SSAB plus combined heat and power (CHP) plant), and conclusions for long term and short term possibilities were discussed. Major efforts have been made recently to develop process integration technology. In Sweden, this has been realised within a national programme for the total processing industry (steel, pulp and paper, petrochemicals, food). There are synergies, as the optimisation problem itself is relatively similar, independent of industry sector.
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| 45. |
- Gustavsson, Joel, et al.
(författare)
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Comparison of calculated equilibrium and operation data for blast furnace with focus on silicon
- 2009
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Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 36:5, s. 341-353
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Tidskriftsartikel (refereegranskat)abstract
- An investigation of reactions involving blast furnace hot metal, slag and gas at equilibrium was carried out. Performed calculations were based on estimated total gas pressures, measured temperatures and hot metal and slag compositions. Calculated element contents of liquid phases were found to be very similar to their corresponding values determined through measurement when formation of the gas phase was suppressed. This resulted in higher equilibrium CO partial pressures compared to the measured total gas pressure in the bustle ring. When only equilibrium conditions were considered, the predicted amount of silicon was much higher than the measured. A comparison of activity coefficients of elements in the hot metal using different calculation models was also carried out. Two different models based on dilute solutions were compared with the TCFe3 database developed for the software Thermo-Calc, which can handle higher alloying concentrations. Considerably different calculation results were found among the different models studied.
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| 46. |
- Hazra, Sujan, et al.
(författare)
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Optimization of high alumina slag practice in blast furnace ironmaking: an industrial approach (PART 1: fundamental aspects)
- 2023
-
Ingår i: Ironmaking & steelmaking. - : Informa UK Limited. - 0301-9233 .- 1743-2812. ; 50:8, s. 1124-1137
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Tidskriftsartikel (refereegranskat)abstract
- The productivity of the blast furnace Ironmaking process is significantly dependent on the slag chemistry. The presence of compounds like Al2O3 in high quantities can make the hearth slag highly viscous and difficult to tap. The objective of part-1 of this study is to provide a comprehensive analysis of the role of high alumina (Al2O3 > 15%) compositions in the blast furnace slags. Slag viscosity, liquidus temperature, activation energy, etc., are critically reviewed with respective solutions to operate under the desired conditions. Flow parameters of the slag are examined to understand the melting-softening phenomena which directly affect the slag tap-to-tap time. The addition of certain additives to the slag system has also been studied with the aim to improve the target properties of the slag. A range of slag compositions and their optimization techniques are discussed in this part to provide greater insight into the topic.
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| 47. |
- Hessling, Oscar, et al.
(författare)
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Experimental study on hydrogen reduction of industrial fines in fluidized bed
- 2021
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Ingår i: Ironmaking & steelmaking. - : Informa UK Limited. - 0301-9233 .- 1743-2812. ; 48:8, s. 936-943
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Tidskriftsartikel (refereegranskat)abstract
- A novel setup of fluidized bed was developed to study the reduction of iron oxides by pure hydrogen. The setup enabled the introduction of powder directly to pure hydrogen atmosphere at experimental temperature. The arrangement was to minimize the experimental uncertainties due to gas switching. Hematite and magnetite powders were studied in the temperature range of 768-888 K. Reduction rates of the two powders were found to be similar. For both powders, the reduction rates were very high before the O/Fe ratio reached 0.5. Thereafter, the reduction was sluggish. SEM analyses revealed that the later stages of reaction was controlled by diffusion through the product layer on bigger particles, irrespective of the type of oxide powder. The results have indicated that both hematite and magnetite powder could be employed in fluidized bed. The results have also suggested that process optimization is essential regarding the sluggish reaction below 0.5 O/Fe ratio.
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| 48. |
- Hjortsberg, Erik, et al.
(författare)
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X-ray microtomography for characterisation of cracks in iron ore pellets after reduction
- 2013
-
Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 40:6, s. 399-406
-
Tidskriftsartikel (refereegranskat)abstract
- This work presents a method, based on X-ray microtomography and three-dimensional (3D) image analysis, of characterising and quantifying crack distribution in iron ore pellets. The aims have been to verify the method and to determine to what extent crack propagation contributes to the decrease in compressive strength that occurs during reduction at 500°C as haematite transforms into magnetite. Raw materials known to cause disintegration problems were selected in order to promote crack propagation. Pellets displayed crack lengths of sizes roughly corresponding to half the pellet diameter already before reduction and, during reduction, a further crack propagation of ∼50% occurred. Through estimations by finite element analysis of the crack size and the pellet geometry, it has been possible to determine that this crack growth most likely is a mechanism that contributes to the decrease in compressive strength. The decrease of ∼90% that was experimentally determined to occur after 30 min of reduction is, however, too large to be explained by crack propagation alone. The study shows that the proposed techniques allow 3D imaging of iron ore pellets and characterisation of cracks. The scans are non-destructive and can be carried out repeatedly, which allows a specific sample to be studied at different stages during a process. Through future use of the proposed method, our aim is to reach a deeper understanding of the mechanisms behind low temperature disintegration of iron ore pellets and the performance of LKAB olivine pellets inside the blast furnace.
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| 49. |
- Hu, Xianfeng, et al.
(författare)
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Thermogravimetric study on carbothermic reduction of chromite ore under non-isothermal conditions
- 2015
-
Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 42:6, s. 409-416
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, the reduction of chromite ore by coke was investigated by means of thermogravimetric analysis under non-isothermal conditions (from room temperature to 1823 K). The fractional reduced samples were examined by SEM/EDS and X-ray diffraction analyses. The experimental results showed that the reduction of iron in the chromite ore started before that of chromium in the ore, and the reduction of chromium and iron in the ore overlapped to some degree. Chromium iron carbide (Cr,Fe)7C3, was found to be the intermediate phase during the reduction, and a chromium gradient was found in the spinel phase of the fractional reduced sample at 1673 K. A four-stage reduction process was proposed: one stage involving the reduction of iron in the chromite ore and three stages involving the reduction of chromium in the ore. The activity aspects of component FeCr2O4 and component MgCr2O4 in the chromite ore were considered. The difficulty in the reduction of the chromite ore is attributed to the fact that, as the reduction proceeds, the activity of the component MgCr2O4 in the fractional reduced ore will decrease to a very low level, which makes further reduction very difficult.
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| 50. |
- Ipek, Nulifer, et al.
(författare)
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Improvement of the electrolytic metal pickling process by inter-electrode insulation
- 2005
-
Ingår i: Ironmaking & steelmaking. - 0301-9233 .- 1743-2812. ; 32:1, s. 87-96
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Tidskriftsartikel (refereegranskat)abstract
- The existing industrial electrolytic steel pickling process is only 30% current efficient. Use of approximate modelling of the process and solution of the model predicts that inter-electrode insulation improves the current and energy efficiency, and this paper describes the experimental work that has validated this prediction. Some of the main results are: (a) the current efficiency varied from 20% without insulation to 100% with complete insulation, (b) the use of just partial insulations yielded a significant improvement in the process efficiency and at the same time maintained good electrolyte mixing and homogeneity which can not be attained with complete insulation. The theoretical foundations of this method and its various consequences are discussed. The method is relatively easy to apply to existing industrial electrolytic pickling tanks, and also provides system control flexibility for optimal pickling of different steel grades. The method's application cost is relatively low and saves investment in new equipment if a retrofit of an existing system is desired.
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