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  • 1.
    Alexis, Jonas
    et al.
    MEFOS − Stiftelsen för Metallurgisk Forskning.
    Jönsson, P.
    Royal Institute of Technology.
    Jonsson, Lage
    MEFOS − Stiftelsen för Metallurgisk Forskning.
    Heating and electromagnetic stirring in a ladle furnace - a simulation model2000Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 40, nr 11, s. 1098-1104Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A three-dimensional simulation model coupling heating and induction stirring in an ASEA-SKF ladle furnace was developed. Data of the heat transfer from the arcs to the steel bath were predicted in a separate model and included as boundary conditions in a ladle model. The arc model considers the contributions of heat transferred by of each of the following mechanisms: radiation, convection, condensation and energy transported by electrons. Predictions were made to simulate the change of temperature distribution in the ladle during simultaneous heating with electrodes and stirring by induction. A first attempt was made to compare the predictions with measured temperatures from a 100 t ASEA-SKF ladle. The agreement was found to be fairly good when heat-flux data for a 25 cm arc length were used as input to the ladle model. This indicates that the model can be used for more in-depth studies of the effects of heating for ladles that are inductively stirred.

  • 2.
    Alexis, Jonas
    et al.
    MEFOS − Stiftelsen för Metallurgisk Forskning.
    Jönsson, P.G.
    KTH.
    Jonsson, Lage
    MEFOS − Stiftelsen för Metallurgisk Forskning.
    A model of an induction-stirred ladle accounting for slag and surface deformation1999Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 39, nr 8, s. 772-778Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A 3 dimensional 2-phase model of an induction stirred ladle has been developed. The model is based on fundamental transport equations and includes the solution of steel- and slag-phase. Predicted velocities are in very good agreement with experimental data. Predicted velocities and turbulent kinetic energy dissipation from the model are shown to have linear relationships with input stirring force for different cylindrical ladles. Linear equations forthese relations are presented. Further calculations have shown that these linear equations also are able to predict velocities for a conical ladle. © 1999 ISIJ.

  • 3.
    Alexis, Jonas
    et al.
    MEFOS − Stiftelsen för Metallurgisk Forskning.
    Ramirez, M.
    Massachusetts Inst. of Technology.
    Trapaga, G.
    Massachusetts Inst. of Technology.
    Jönsson, P.
    Royal Institute of Technology.
    Modeling of a DC Electric Arc Furnace - heat transfer from the arc2000Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 40, nr 11, s. 1089-1097Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A mathematical model describing heat and fluid flow in an electric arc has been developed and used to predict heat transfer from the arc to the steel bath in a DC Electric Arc Furnace. The arc model takes the separate contributions to the heat transfer from each involved mechanism into account, i.e. radiation, convection, condensation and energy transported by electrons. The model predicts heat transfer for different currents and arc lengths. Model predictions show that arc efficiency is higher for lower power input. The model also predicts shear stresses and current density distribution at the steel surface. This information can be used as boundary condition input to simulate the effect of heating with electrodes in a DC EAF on the heat and fluid flow in the steel bath.

  • 4.
    Brämming, Mats
    et al.
    SSAB EMEA.
    Millman, S.
    Tata Steel Research.
    Overbosch, A.
    Tata Steel Research.
    Kapilashrami, A.
    SSAB EMEA.
    Malmberg, Donald
    RISE, Swerea, Swerea MEFOS AB.
    Björkman, B.
    Luleå University of Technology.
    BOS vessel vibration measurement for foam level detection2011Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 51, nr 1, s. 71-79Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the BOS process liquid slag together with dispersed metal droplets, solid particles and process gases form an expanding foam. Certain process conditions may lead to excessive foam growth, forcing foam out through the vessel mouth, an event commonly known as 'slopping'. Slopping results in loss of valuable metal, equipment damage and lost production time. In the early 1980s a system for foam level and slopping control was installed at SSAB's steel plant in Luleå, a system based on the correlation between BOS vessel vibration in a narrow low frequency band and foam development. The technique, in this case with an accelerometer mounted on the trunnion bearing housing, soon showed its usefulness, for example when adapting existing lance patterns to a change in oxygen lance design from a 3-hole to a 4-hole nozzle. Estimating the actual foam height in the BOS vessel was of great importance in the recently completed RFCS funded research project "IMPHOS" (Improving Phosphorus Refining). Based on the earlier positive experiences, it was decided to further develop the vessel vibration measurement technique. Trials on an industrial size BOS vessel type LD/LBE have been carried out, this time with a tri-axial accelerometer mounted on the vessel trunnion. FFT spectrum analysis has been used in order to find the frequency band with best correlation to the foam level development. The results show that there is a correlation between vessel vibration and foam height that can be used for dynamic foam level and slopping control. © 2011 ISIJ.

  • 5.
    Grip, C.E.
    et al.
    SSAB Tunnplåt AB.
    Jonsson, Lage
    RISE, Swerea, Swerea MEFOS AB.
    Jönsson, P.
    KTH.
    Jonsson, K.O.
    SSAB Tunnplåt AB.
    Numerical prediction and experimental verification of thermal stratification during holding in pilot plant and production ladles1999Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 39, nr 7, s. 715-721Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A 3-dimensional CFD-model has been developed to simulate the natural convection flow in ladles. Qualified measurements of temperature and velocities in 107 and 7 tonne ladles have been made to verify the model. The downward convection flow at the ladle wall has been studied using radioactive isotopes and the thermal stratification has been studied by means of continuous temperature measurements. The experimental techniques are complex and additional numerical simulations have been carried out to study the effect of the measurement technique on the measurement error. The result indicates that the measurements are of sufficient accuracy for the validation. The measurements are compared to predictions from the numerical model. The main conclusion is that the theoretical CFD model gives a very accurate estimation of the temperature distribution during holding.

  • 6.
    Grip, C.-E.
    et al.
    SSAB Tunnplåt AB.
    Jonsson, Lage
    MEFOS − Stiftelsen för Metallurgisk Forskning.
    Jönsson, P.G.
    Ovako Steel AB.
    Prediction of emptying flows in ladles and verification with data from trace element plant trials1997Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 37, nr 11, s. 1081-1090Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A three-dimensional mathematical model of a casting ladle based on fundamental transport equations has been developed. The model may be used for predictions of both a standing ladle and a ladle from which steel is teemed into a tundish. An additional feature of the model is that it can predict concentration profiles of tracer elements which are added to the steel. The predicted concentration profiles during teeming are compared to experimental data from plant trials performed at SSAB and the agreement is found to be good. The model is used as a tool in the development of process control models.

  • 7.
    Hilding, T.
    et al.
    Luleå University of Technology.
    Gupta, S.
    University of New South Wales.
    Sahajwalla, V.
    University of New South Wales.
    Björkman, Bo
    Luleå University of Technology.
    Wikström, Jan-Olov
    MEFOS − Metallurgical Research Institute AB.
    Degradation behaviour of a high CSR coke in an Experimental Blast Furnace: Effect of carbon structure and alkali reactions2005Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 45, nr 7, s. 1041-1050Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A high CSR coke was tested in the LKAB's Experimental Blast Furnace (EBF) at Luleå. The evolution of physical and chemical properties of the centre-line coke samples were analysed by Light Optical Microscopy (LOM), BET N2 absorption and SEM/XRF/XRD. Alkali distribution in the EBF cokes was examined by XRF/SEM and EDS. Thermo Gravimetric Analysis (TGA) was used to measure isothermal and non-isothermal CO2 reactivity of the cokes. The crystalline order of carbon and the concentration of alkalis were found to increase as the coke descended through thermal reserve zone to the cohesive zone of the EBF. The crystallite height (Lc) of EBF coke carbon displayed a linear correlation with the measured EBF temperatures demonstrating the strong effect of temperature on carbon structure of coke in the EBF. Alkali concentration of the coke was increased as it descended into the EBF, and was uniformly distributed throughout the coke matrix. The CO2 reactivity of lower zone cokes was found to increase when compared to the reactivity of the upper zones cokes, and was related to the catalytic effect of increased alkalis concentration. The deterioration of coke quality particularly coke strength and abrasion propensity were related to coke graphitisation, alkalization and reactivity, Coke graphitisation is shown to have a strong influence on the coke degradation behaviour in the EBF. © 2005 ISIJ.

  • 8.
    Hooey, Lawrence
    et al.
    RISE, Swerea, Swerea MEFOS AB.
    Bodén, Axel
    RISE, Swerea, Swerea MEFOS AB.
    Wang, Chuan
    RISE, Swerea, Swerea MEFOS AB.
    Grip, C.-E.
    Luleå University of Technology.
    Jansson, B.
    SSAB.
    Design and application of a spreadsheet-based model of the blast furnace factory2010Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 50, nr 7, s. 924-930Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The development and application of a 1-dimensional static blast furnace model, "Masmod", written in a common spreadsheet environment, is described. The model includes blast furnace, hot stove, and burden models with recent additions of other operations including CO2 stripping and top gas recycle. Although blast furnace modelling has become increasingly sophisticated, a relatively simple and flexible model is shown to be useful for evaluating burden options, equipment and operational strategies, and process development. Furthermore the Masmod model has been integrated with global steel plant optimization models and Process Integration models for more complex system analysis and optimization. © 2010 ISIJ.

  • 9.
    Hooey, Lawrence
    et al.
    RISE, Swerea, Swerea MEFOS AB.
    Riesbeck, Johan
    RISE, Swerea, Swerea MEFOS AB.
    Wikström, Jan-Olov
    RISE, Swerea, Swerea MEFOS AB.
    Björkman, B.
    Luleå University of Technology.
    Role of ferrous raw materials in the energy efficiency of integrated steelmaking2014Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 54, nr 3, s. 596-604Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The role of ferrous raw materials and iron ore agglomeration in energy consumption of integrated steelmaking has been evaluated using a system-wide model. Four steelplant cases were defined: typical European steelplant with sinterplant; Nordic steelplant with sinterplant; European steelplant with sinter:pellet ratio of 50%, and Nordic steelplant charging pellets and a small amount of briquettes. Energy consumption in the mining system were estimated from published statistics at 150 MJ/t for lump ore and sinter fines, 650 MJ/t for pellets made from magnetite and 1 050 MJ/t for pellets made from hematite. An integrated steelplant model including all major unit operations was used to calculate overall system energy consumption from iron ore mining to hot rolled coil. Adjustments were made accounting for energy benefit of ground granulated blast furnace slag in cement production, energy required for cement production required for briquetting, and excess BF and BOF gas producing electricity in a 32% efficient power plant. The system-wide net adjusted energy in the first three steeplant cases showed marginal improvement with use of high grade sinter fines and decrease of pellet/sinter ratio to 50% compared to typical European case. Nordic steelplant charging pellets and briquettes had a reduction in system-wide energy of 5% to 8% for charging pellets from hematite or magnetite respectively compared to the typical European steelplant charging sinter and pellets made from hematite ore. Replacement of sinter with pellets was mainly responsible for the improvement with smaller contributions from magnetite ore in pelletizing. © 2014 ISIJ.

  • 10.
    Hu, Xianfeng
    et al.
    RISE - Research Institutes of Sweden, Swerea, Swerea MEFOS AB.
    Sundqvist Okvist, Lena
    RISE - Research Institutes of Sweden, Swerea, Swerea MEFOS AB. Luleå University of Technology, Sweden.
    Aström, Elin
    LKAB, Sweden .
    Forsberg, Fredrik
    LKAB, Sweden; Luleå University of Technology, Sweden.
    Checchia, Paolo
    INFN Sezione di Padova, Italy.
    Bonomi, Germano
    University of Brescia, Italy.
    Calliari, Irene
    University of Padova, Italy.
    Calvini, Piero
    University of Genova, Italy ; Sezione INFN di Genova, Italy.
    Donzella, Antonietta
    University of Brescia, Italy.
    Faraci, Eros
    RINA CONSULTING - Centro Sviluppo Materiali SPA, Italy.
    Gonella, Franco
    INFN Sezione di Padova, Italy.
    Klinger, Joel
    INFN Sezione di Padova, Italy.
    Pagano, Davide
    University of Brescia, Italy.
    Rigoni, Andreo
    University of Padova, Italy.
    Zanuttigh, Pietro
    University of Padova, Italy.
    Ronchese, Paolo
    University of Padova, Italy.
    Urbani, Michele
    University of Padova, Italy.
    Vanini, Sara
    University of Padova, Italy.
    Zenoni, Aldo
    University of Brescia, Italy.
    Zumerle, Gianni
    University of Padova, Italy.
    Exploring the capability of muon scattering tomography for imaging the components in the blast furnace2018Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 58, nr 1, s. 35-42Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Knowing the distribution of the materials in the blast furnace (BF) is believed to be of great interest for BF operation and process optimization. In this paper calibration samples (ferrous pellets and coke) and samples from LKAB’s experimental blast furnace (probe samples, excavation samples and core-drilling samples) were measured by the muon scattering tomography detector to explore the capability of using the muon scattering tomography to image the components in the blast furnace. The experimental results show that it is possible to use this technique to discriminate the ferrous pellets from the coke and it is also shown that the measured linear scattering densities (LSD) linearly correlate with the bulk densities of the measured materials. By applying the Stovall’s model a correlation among the LSD values, the bulk densities and the components of the materials in the probe samples and excavation samples was established. The theoretical analysis indicates that it is potential to use the present muon scattering tomography technique to image the components in various zones of the blast furnace.

  • 11.
    Hutchinson, Bevis
    et al.
    RISE - Research Institutes of Sweden, Material och produktion, KIMAB.
    Lindell, David
    RISE - Research Institutes of Sweden, Material och produktion, KIMAB.
    Barnett, Matthew
    Deakin University, Australia.
    Yielding behaviour of martensite in steel2015Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 55, nr 5, s. 1114-1122Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Although martensite is recognised as a very strong phase in carbon steels, its initial yielding commences at low stresses and the tensile stress-strain curve shows a smooth, rounded form. Evidence is presented from x-ray diffraction to show that this behaviour is due to the presence of intra-granular stresses that are residues after the shear transformation from austenite to martensite. These internal stresses are reduced in magnitude by plastic deformation and also by tempering. Reduction of internal stress due to plasticity is shown by a decrease in XRD line broadening after deformation. A simple model is presented in which the stress-strain behaviour is controlled by relaxation of the internal stresses almost up to the point of the ultimate tensile strength. It demonstrates that only a very small fraction of the material remaining in a purely elastic state provides a large stabilising effect resisting necking. A corollary of this is that the uniform elongation of martensitic steel actually increases with increase in the strength level. Effects of heat treatment are also reproduced in the model, including the increase in conventional yield stress (Rp0.2) that occurs after low temperature tempering.

  • 12.
    Jonsson, Lage
    et al.
    MEFOS − Stiftelsen för Metallurgisk Forskning.
    Jönsson, Pär
    MEFOS − Stiftelsen för Metallurgisk Forskning.
    Modeling of fluid flow conditions around the slag/metal interface in a gas-stirred ladle1996Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 36, nr 9, s. 1127-1134Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A three-phase model of a gas-stirred steel bath covered with a slag layer has been developed. Predicted steel surface velocities have been shown to be in at least five times greater agreement with experimental data compared to predicted velocities from a model which excludes the effect of a slag phase. It has also been shown that it is possible to predict the amount of slag dispersed into the steel.

  • 13.
    Jonsson, Lage
    et al.
    MEFOS − Stiftelsen för Metallurgisk Forskning.
    Sichen, D.
    KTH.
    Jönsson, P.
    Ovako Steel AB.
    A New Approach to Model Sulphur Refining in a Gas-stirred Ladle - A Coupled CFD and Thermodynamic Model1998Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 38, nr 3, s. 260-267Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the present work, a new modelling approach has been put forward to study slag-metal reactions. Sulphur refining in a gas-stirred ladle has been taken as an example. A two-dimensional fluid dynamic model accounting for the steel, slag and argon phases has been incorporated with the thermodynamics of desulphurisation. Comparison of the results of the model calculation with plant data from Ovako Steel indicates that the present approach has great potential. It has opened up the possibility of developing process models based on fundamental equations.

  • 14.
    Jönsson, P.G.
    et al.
    Ovako Stl. AB (an SKF Group Company).
    Jonsson, Lage
    MEFOS − Stiftelsen för Metallurgisk Forskning.
    Sichen, D.
    KTH.
    Viscosities of LF slags and their impact on ladle refining1997Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 37, nr 5, s. 484-491Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study focuses on the viscosities of synthetic slags used in secondary refining operations. Typically, these slags contain mainly CaO, AI2O3, MgO and Si02. The data for LF slag viscosities are used in a model for a gas-stirred ladle to evaluate the effect of viscosity variations on predicted parameters close to the slag/steel interface. The results show that viscosities of LF slags significantly affect ladle refining operations. It is therefore necessary to control the composition of the synthetic slags carefully during production.

  • 15.
    Karlberg, Mats
    RISE, Swerea, Swerea MEFOS AB.
    Modelling of the temperature distribution of coiled hot strip products2011Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 51, nr 3, s. 416-422Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    It has always been of greatest importance to control the temperature distribution in the products throughout the hot strip rolling process including the final coiling operation. A computational model of the latter has been developed and validated, which is presented in this paper. Furthermore, the influences of the different parameters on the transient thermal distribution are evaluated. The formulated model as accounts for twodimensional heat conduction is assuming axi-symmetric conditions. Temperature dependent properties are accounted for results in a nonlinear heat conduction problem that is solved by use of the Finite Element Method (FEM). The calculations have been validated by two full scale measurement campaigns and show a good agreement with measurements. © 2011 ISIJ.

  • 16.
    Leimalm, U.
    et al.
    Luleå University of Technology.
    Forsmo, S.
    LKAB R and D.
    Dahlstedt, A.
    LKAB R and D.
    Ökvist, Lena Sundqvist
    RISE, Swerea, Swerea MEFOS AB.
    Björkman, B.
    Luleå University of Technology.
    Blast furnace pellet textures during reduction and correlation to strength2010Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 50, nr 10, s. 1396-1405Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The blast furnace is the most common means of producing hot metal. As the amounts of reduction agents increases, which influence in-furnace conditions such as ascending gas properties, temperature profiles and the ore-to-coke ratio, new demands are put on the iron-bearing material in terms of both reducibility and mechanical strength. To investigate the possibilities to use the Pellet Multi Press (PMP) equipment for compression strength measurements of reduced pellets and to gain a deeper understanding of the correlation between pellet texture and strength, an initial study of pellets taken from the LKAB Experimental Blast Furnace (EBF) was conducted. Furthermore, the pellet pieces generated after compression tests were characterized using light optical microscopy. In order to correlate the texture of pellet pieces to the pellet texture prior to breakage, a characterization of the chronological pellet texture development during reduction in the EBF was performed. The original pellet texture remained in the beginning of reduction and differences receded through the EBF shaft as wustite and Femet was formed. Occurrence of Femet in the pellet texture increased the compression strength, while less reduced and less sintered textures showed the reverse effect. So far, the results from compression strength tests indicate that disintegration of pellets takes place at a reaction front, at the transition between different texture types of iron oxide or at the location of a visible surface crack. © 2010 ISIJ.

  • 17.
    Leimalm, U.
    et al.
    SSAB Oxelösund.
    Lundgren, M.
    Luleå University of Technology.
    Ökvist, Lena Sundqvist
    RISE, Swerea, Swerea MEFOS AB.
    Björkman, B.
    Luleå University of Technology.
    Off-gas dust in an experimental blast furnace part 1: Characterization of flue dust, sludge and shaft fines2010Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 50, nr 11, s. 1560-1569Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In blast furnace (BF) ironmaking, efforts are made to decrease coke consumption, which can be done by increasing the pulverized coal injection rate (PCR). This will cause changes in ¡n-furnace reduction conditions, burden distribution, demands on raw material strength, etc. In order to maintain stable operation, but also to obtain low amounts of material losses through the off-gas, it is important to understand fines generation and behaviour in the BF Off-gas dust and shaft fines generated in the LKAB Experimental Blast Furnace (EBF) were sampled during operation with olivine pellets and mixtures of acid pellets and sinter as iron-bearing materials. Characterization using XRD, SEM and LOM was focused on fines from iron-bearing materials, coke and slag formers. The results showed that flue dust, mainly <0.5 mm, was mechanically formed and created in the same manner for all investigated samples. Carbon-containing particles dominated in the fractions >0.075 mm and consisted mainly of coke particles from the shaft. Fe-containing particles, as Fe2O 3 from the top of the shaft, formed the major part of flue dust fractions <0.063 mm. Particles from slag formers such as quartzite and limestone were observed in flue dust when slag formers were utilized in the feed. Sludge consisted mainly of chemically formed spherical particles <1 μm precipitated from the ascending gas as the temperature decreased. © 2010 ISIJ.

  • 18.
    Leimalm, U.
    et al.
    Luleå University of Technology.
    Ökvist, Lena Sundqvist
    MEFOS − Metallurgical Research Institute AB.
    Björkman, B.
    Luleå University of Technology.
    Effect of different PCI practice on the texture obtained during reduction of iron oxide pellets2008Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 48, nr 12, s. 1686-1695Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In modern blast furnace ironmaking, producers continuously strive to reduce coke consumption by replacing coke with e.g., an increased amount of injected pulverized coal. A change in pulverized coal injection rate (PCR) and injection coal type will influence the in-furnace conditions and thus the reduction of iron oxides. In the present study, the reduction behaviour of olivine pellets and textures formed were investigated in the LKAB Experimental Blast Furnace (EBF) and in laboratory scale. In the EBF, effects of injection of an low-volatile (LV) and an high-volatile (HV) coal type at different PCR while two types of oxygen supply methods were employed were investigated. The choice of injection coal type was conclusive for the Femet texture formed during reduction, extent of Femet carburization and K distribution in the pellets. The amount of volatile matters in the coal type had a greater effect on the reduction properties than the PCR and oxygen supply method. Laboratory experiments simulating PCR, based on measurements in the EBF, showed that the initial reduction conditions, in terms of temperature level and reduction gas composition, determined the pellet texture up to a reduction degree of at least 60%. The tests carried out in the EBF showed that the pellets were well suited for blast furnace reduction under all the investigated process conditions. The laboratory tests supported this conclusion. © 2008 ISIJ.

  • 19.
    Lundgren, M.
    et al.
    Luleå University of Technology.
    Leimalm, U.
    SSAB Oxelösund.
    Hyllander, G.
    LKAB RandD.
    Ökvist, Lena Sundqvist
    RISE, Swerea, Swerea MEFOS AB.
    Björkman, B.
    Luleå University of Technology.
    Off-gas dust in an experimental blast furnace part 2: Relation to furnace conditions2010Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 50, nr 11, s. 1570-1580Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the blast furnace process, material losses are caused by particles that are blown out of the furnace by the off-gas. In order to reduce these losses, it is important to understand the correlations between furnace conditions and off-gas dust formation. Off-gas dust, as flue dust and sludge, were collected during shaft probe sampling in LKAB Experimental Blast Furnace (EBF). Process data was used to evaluate the relationship between off-gas dust amounts and furnace conditions. The graphitization degree (Lc value) of shaft coke and coke in flue dust was determined using XRD measurements. Solution loss in the shaft had a negligible effect on coke degradation and the coke particles which ended up in the flue dust were mainly derived from abrasion at low temperatures. The amount of alkali and SiO2 in sludge increased with higher PCR and flame temperature, which confirmed that submicron spherical particles in sludge originated from the high temperature area around the raceway. Theoretical critical particle diameters of materials, which could be blown out with the off-gas, were estimated. Flow conditions in the top of the shaft as well as and the properties of fine particles in terms of size and density are important when outflow of mechanical dust, such as flue dust, is concerned. Low off-gas temperatures, and thus lower off-gas velocities, are favourable for low flue dust amounts expelled from the blast furnace. © 2010 ISIJ.

  • 20.
    Malmberg, Donald
    et al.
    RISE, Swerea, Swerea MEFOS AB.
    Hahlin, Pär
    RISE, Swerea, Swerea MEFOS AB.
    Nilsson, E.
    IDE Department.
    Microwave technology in steel and metal industry, an overview2007Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 47, nr 4, s. 533-538Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    In many metallurgical operations, effective analysis of the processes can be very difficult with available technology. This is especially true if the analysis is to be performed on-line and in a harsh environment characterized by high temperatures, dust and liquid metal. Protection of the equipment requires both rugged encapsulation as well as elaborate sampling systems and exposure of the equipment to the hazardous environment must be minimised. Often this result in an increased level of service and maintenance requirements and, in the worst case, the maintenance cost might be so high that the equipment is not installed. Microwave technology is a versatile and powerful tool with many different applications in the scientific community. It is insensitive to dust and fume and, for several years, the technology has been tested at MEFOS and evaluated for different metallurgical processes. It has been applied to slag thickness measurement and slag composition in an induction furnace, 3D imaging of the burden surface in a charging model on pilot scale as well as raceway depth measurements in a Blast Furnace. The idea of using microwave technology for gas analysis in metallurgical processes has also been explored. However, despite its many advantages, microwave technology is still not employed extensively in the steel and metal industries. © 2007 ISIJ.

  • 21.
    Mousa, Elsayed Abdelhady
    et al.
    RISE - Research Institutes of Sweden, Swerea, Swerea MEFOS AB. CMRDI Central Metallurgical Research and Development Institute, Egypt.
    Ahmed, Hesham Mohamed
    Lulea University of Technology, Sweden; CMRDI Central Metallurgical Research and Development Institute, Egypt.
    Wang, Chuan
    RISE - Research Institutes of Sweden, Swerea, Swerea MEFOS AB. Åbo Akademi University, Finland.
    Novel approach towards biomass lignin utilization in ironmaking blast furnace2017Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 57, nr 10, s. 1788-1796Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Growing concerns over fossil CO2 emissions has created a considerable interest in an efficient utilization of renewable biomass in steel industry. Biomass lignin can be used as binder and reducing agent in the blast furnace briquettes. The traditional briquettes consist of various iron oxide-containing residues and cement is used as binder to give the proper mechanical strength. In the present study, cement (C) has been partially and totally substituted with lignin (L) to produce briquettes containing 0-12 wt.% lignin (L/C: 0, 10, 25, 50 and 100%). The mechanical strength has been evaluated based on drop test and tumbler index measurement. The partial replacement of cement with lignin up to 25% (3.0 wt.% lignin in briquettes) was exhibited adequate briquettes strength for blast furnace application. At higher substitution rate (L/C: 50 and 100%), the briquettes strength was sharply decreased. The briquettes with proper mechanical strength (L/C: 0, 10 and 25%) were subjected to self-reduction under inert atmosphere using thermogravimetric technique (TGA). The reduction rate of briquettes increased when increasing the cement substitution with lignin. The reduction took place in two main steps at 500-800°C and 800-940°C. Combined effect of gas diffusion and interfacial reaction were the rate determining step at the first stage while carbon gasification was controlling the second step of reduction. Interrupted reduction tests have been conducted to evaluate the compression strength after reduction. For all briquettes, the increased reduction temperature and lignin content deteriorated the briquette's mechanical strength due to the effect of dehydration and lignin gasification.

  • 22.
    Ramirez Lopez, Pavel Ernesto
    et al.
    RISE - Research Institutes of Sweden, Swerea, Swerea MEFOS AB.
    Jalali, Pooria Nazem
    RISE - Research Institutes of Sweden, Swerea, Swerea MEFOS AB. KTH Royal Institute of Technology, Sweden.
    Sjostrom, Ulf
    RISE - Research Institutes of Sweden, Swerea, Swerea MEFOS AB.
    Jonsson, Par Goran
    KTH Royal Institute of Technology, Sweden.
    Mills, Kenneth C.
    Imperial College London, UK.
    Sohn, Il
    Yonsei University, South Korea.
    Key Lubrication Concepts to Understand the Role of Flow, Heat Transfer and Solidification for Modelling Defect Formation during Continuous Casting2018Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 58, nr 2, s. 201-210Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Surface defects are recurrent problems during Continuous Casting of steel due to the introduction of new grades that are often difficult to cast, as well as the everlasting pursuit for higher quality and improved yield. Accordingly, numerical modelling has become a ubiquitous tool to analyse the formation mechanisms of such defects. However, industrial application of simulations is often hampered by oversimplifications and omissions of important process details such as variations in material properties, specific casting practices or shortcomings regarding fundamental metallurgical concepts. The present manuscript seeks to create awareness on these issues by visiting key notions such as slag infiltration, interfacial resistance and Lubrication Index. This is done from a conceptual point of view based on industrial observations and numerical modelling experiences. The latter allows a re-formulation of outdated concepts and misconceptions regarding the influence of fluid flow, heat transfer and solidification on lubrication and defect formation. Additionally, the manuscript addresses common challenges and constraints that occur during industrial implementation of numerical models such as the lack of high -temperature material data for slags. Finally, the manuscript provides examples of improvements on product quality and process stability that can be achieved through a holistic approach which combines modelling with laboratory tests, experiences from operators and direct plant measurements.

  • 23.
    Safavi Nick, Reza
    et al.
    RISE, Swerea, Swerea MEFOS AB.
    Tilliander, A.
    KTH Royal Institute of Technology.
    Jonsson, T.L.I.
    KTH Royal Institute of Technology.
    Jönsson, P.G.
    KTH Royal Institute of Technology.
    Mathematical model of solid flow behavior in a real dimension blast furnace2013Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 53, nr 6, s. 979-987Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A mathematical model based on the continuum mechanic concept has been developed to describe the profile of solid particles in an industrial scale blast furnace with respect to the in-furnace conditions and its characteristics such as the shape and size of the deadman. The Navier-Stokes differential equation for multi-phase multi-dimensional space has been used to describe the behavior of existing phases. The surface stress tensor has been defined as an extra term and added to the Navier-Stokes equation to describe the particle-particle interactions. This extra term in the Navier-Stokes equation behave as a breaking force when the particles are sliding down. It is shown that the particles change their profile from a V-shape to a W-shape due to the characteristics of the deadman. Moreover, the velocity magnitude is higher at the outer surface of the deadman for higher grid-slabs in this region than the near-wall cells. However, the situation changes as solid particles moving to even lower level of grid-slabs at the outer surface of the deadman in comparison to near-wall cells. It has also been shown that an increase in the magnitude of the effective pressure reduces the velocity magnitude of descending particles. © 2013 ISIJ.

  • 24.
    Sheng, Dong Yuan
    et al.
    MEFOS − Stiftelsen för Metallurgisk Forskning.
    Kim, C.-S.
    Seoul National University.
    Yoon, J.-K.
    Seoul National University.
    Hsiao, T.-C.
    Northeastern University.
    Water model study on convection pattern of molten steel flow in continuous casting tundish1998Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 38, nr 8, s. 843-851Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Natural convection will obviously influence the liquid steel flow in continuous casting (CC) tundish, which cannot be neglected in tundish metallurgical process. Through the theoretical analysis, the dimensionless number, Gr/Re 2, is adopted to determine the convection pattern in tundish system. Validity of this criteria in a reduced scale water model are also discussed in this paper. Non-isothermal water model experiment with the temperature variation of inlet stream, has been simulated to see the effect of temperature variation of ladle stream. The convection pattern of molten steel flow in continuous casting tundish is also studied numerically by using the commercialized computational fluid dynamic (CFD) software package, CFX4. From the results of theoretical analysis, physical and mathematical model simulation, it can be stated that the convection pattern of molten steel flow in tundish is controlled by the combined nature convection and forced convection.

  • 25.
    Siwecki, Tadeusz
    et al.
    RISE, Swerea, Swerea KIMAB AB.
    Eliasson, Johan
    RISE, Swerea, Swerea KIMAB AB.
    Lagneborg, Rune
    RISE, Swerea, Swerea KIMAB AB.
    Hutchinson, Bevis
    RISE, Swerea, Swerea KIMAB AB.
    Vanadium microalloyed bainitic hot strip steels2010Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 50, nr 5, s. 760-767Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The aim of the present study was to investigate the possibilities of reaching yield strengths beyond 600 MPa for low carbon bainitic hot strip steels by vanadium microalloying together with suitable base alloying. The processing conditions and levels of carbon and nitrogen chosen in this laboratory investigation correspond to those of a typical 8 mm hot strip steel containing 0.04mass% carbon and 0.010 mass% nitrogen from electric arc furnace practice processed in conventional or compact strip mills. It was found that a base alloying corresponding to 1.4mass% Mn, 1.0mass% Cr and 0.25mass% Mo is required to form a fully bainitic structure after coiling at 400°C. The decisive factors determining the strength of bainitic hot strip steels are firstly the bainite transformation temperature and secondly the extent to which recovery of the densely dislocated bainitic ferrite can be prevented. The results of this study demonstrate that vanadium microalloying effectively prevents the recovery of the bainitic ferrite and leads to retention of the strength of the virgin bainite after coiling. This is primarily due to retardation of recovery by fine vanadium carbonitrides precipitates on dislocations and only to a lesser extent to true precipitation strengthening. With 0.08 mass% V together with 0.010-0.020 mass% N the yield strength lies in the range of 750-790MPa compared to 680 MPa for a similar reference steel without vanadium. By raising the chromium content to 2 %, yield strengths in the range of 840-880 MPa have been reached. This is attributed to a lowering of the bainite transformation temperature resulting from the higher base alloying. © 2010 ISIJ.

  • 26.
    Song, Tengfei
    et al.
    University of Science and Technology Beijing, China.
    Zhang, Jianliang
    University of Science and Technology Beijing, China.
    Wang, Guangwei
    University of Science and Technology Beijing, China.
    Wang, Haiyang
    University of Science and Technology Beijing, China.
    Xu, Runsheng
    Wuhan University of Science and Technology, China.
    Pang, Qinghai
    University of Science and Technology Liaoning, China.
    Wang, Chuan
    RISE - Research Institutes of Sweden, Material och produktion, Swerea MEFOS AB. Åbo Akademi University, Finland.
    Effect of carbonization conditions on the property and structure of bamboo char for injection in blast furnace2019Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 59, nr 3, s. 442-449Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To evaluate the effect of carbonization conditions on the bamboo, the relationship between carbonization parameter and physicochemical characteristics was studied. The results indicated that the volatile matter drastically decreased with the increase of carbonization temperature, while the fixed carbon and fuel ratio (fixed carbon/volatile matter) increased. Excellent linearity between the fuel ratio and carbonization temperature was obtained. The energy yield decreased gradually when rising the carbonization temperature, whereas the change of heating value was not obvious. A new calculation model of higher heating value (HHV) was developed, and it could be used to predict HHV of the bamboo char more precisely at temperatures above 300°C. The positive impact of functional groups, specific surface area as well as catalysis of alkali metal may contribute to the combustion of bamboo char. The results showed that there is a feasible operating condition for the transformation of bamboo into char with the carbonization parameter at 400°C for 30 min.

  • 27.
    Viklund-White, Christina
    MEFOS − Stiftelsen för Metallurgisk Forskning.
    Use of LCA for the environmental evaluation of the recycling of galvanized steel2000Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 40, nr 3, s. 292-299Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Life Cycle Assessment has been used to compare the environmental performance of landfilling of the zinc used for galvanizing steel with recycling by a number processes. Hypothetical process routes were composed involving three different EAF dust treatment processes, Waelz kiln, DC-furnace, and EZINEX, as well as scrap dezincing. The study shows that recycling of zinc used for galvanizing steel clearly has environmental benefits in that it saves zinc resources. However, zinc recovery does not necessarily decrease the potential impact on global warming and acidification. The magnitude of these two impact categories is tightly correlated with the amount and type of primary energy consumed in a process. Due to the high electricity consumption in the dezincing process, this route has the highest impact on Global Warming Potential as well as Acidification Potential. The major part of the energy requirement for the production of zinc from primary and secondary sources is consumed in the reduction of ZnO to Zn. The consequence is that the theoretically possible saving in primary energy by recycling zinc-containing materials is relatively small. The impact categories land use and waste generation are not considered in this study, but most likely the evaluation of such impacts would further increase the potential environmental impact of the landfill alternative. The results also show that the location of an electricity-intensive process highly affects the potential environmental impact. Comparing process and material alternatives in LCA studies where branch average data is used is therefore considerably more complex than when LCA is used within a company.

  • 28.
    Watakabe, S.
    et al.
    JFE Steel Corporation.
    Miyagawa, K.
    Kobe Steel.
    Matsuzaki, S.
    Nippon Steel and Sumitomo Metal Corporation.
    Inada, T.
    Nippon Steel and Sumitomo Metal Corporation.
    Tomita, Y.
    Nisshin Steel Company.
    Saito, K.
    Nippon Steel and Sumitomo Metal Corporation.
    Osame, M.
    JFE Steel Corporation.
    Sikström, P.
    LKAB.
    Ökvist, Lena Sundqvist
    RISE, Swerea, Swerea MEFOS AB.
    Wikström, Jan-Olov
    RISE, Swerea, Swerea MEFOS AB.
    Operation trial of hydrogenous gas injection of COURSE50 project at an experimental blast furnace2013Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 53, nr 12, s. 2065-2071Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    COURSE50 (CO2 ultimate reduction in steelmaking process by innovative technology for Cool Earth 50) carried out COG and reformed COG (RCOG) injection operation trials at LKAB's experimental blast furnace in Luleå in cooperation with LKAB and Swerea MEFOS. Operation trials were successfully carried out. Input of C in both COG and RCOG injection periods decreased comparing the base period, because ofincrease in H2 reduction instead of C direct reduction that is a huge endothermic reaction. However poor penetration depth of injected gas from shaft tuyere made furnace efficiency worse. Hot top gas injection increased temperature of top gas and upper part of the furnace. Efficiency of hot top gas injection was not clear as sinter degradation did not occur in the base period. © 2013 ISIJ.

  • 29.
    Ye, Guozhu
    et al.
    MEFOS − Stiftelsen för Metallurgisk Forskning.
    Jönsson, Pär
    MEFOS − Stiftelsen för Metallurgisk Forskning.
    Lund, T.
    Ovako Steel AB.
    Thermodynamics and kinetics of the modification of Al2O3 inclusions1996Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 36, nr SUPPL., s. S105-S108Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The use of thermodynamic data in describing calcium modification of aluminium oxide inclusions has been summarised and reviewed. The majority of the published Al-S equilibrium diagrams, based on the following reaction: 3CaO+3S+2Al=3CaS+Al2O3, vary significantly due to different sources for thermodynamic data, especially for the activity of CaO and Al2O3. Using ThermoCalc, the activities of CaO and Al2O3 have been calculated and compared to the published data. Calculations in the present work pertaining to the molten range of the system are in good agreement with the most recently published experimental data of Fujisawa et al.7) Based on the assessed thermodynamic data and observed phenomena during calcium modification of inclusions in steel melts of moderate sulphur content, a model for alumina modification by calcium treatment has been developed. According to the model, the reactions progress by the following sequence until the activity of Al2O3 becomes so low that precipitation of CaS occurs: Al2O3⇒CA6⇒CA 2⇒CA⇒CAx(liquid). © 1996 ISIJ.

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