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  • 1.
    Brämming, Mats
    et al.
    SSAB EMEA.
    Parker, G.
    Tata Steel Europe - Long Products.
    Millman, S.
    Tata Research.
    Kapilashrami, A.
    Tata Research.
    Malmberg, Donald
    RISE, Swerea, Swerea MEFOS.
    Björkman, B.
    Luleå University of Technology.
    Comparison between vessel vibration and audiometry for slopping control in the top-blown BOS process2011In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 82, no 6, p. 683-692Article in journal (Refereed)
    Abstract [en]

    Excess slag foam growth is a frequent problem in the BOS process. In the worst case, foam is forced out of the vessel and this phenomenon, commonly called slopping, not only results in loss of valuable metal yield but also in equipment damage and lost production time. In order to minimize slopping, accurate estimation of the foam level inside the vessel is an important part of BOS process control. In the top blown BOS vessel, slopping control is achieved using both static and dynamic measures. The most common implemented technique for dynamic foam height estimation and slopping control is the audiometer system. An alternative method, vessel vibration monitoring, has been investigated as part of the work in a RFCS funded research project called IMPHOS. In order to judge the usefulness of this method, parallel vibration and audio measurements have been carried out on 130 tonne as well as on 300 tonne BOS vessels. The results show that during stable process conditions there is good agreement between the two methods with regard to foam height estimation and, as vessel vibration and audiometry are largely independent of each other, a combination of the two is likely to increase significantly the accuracy of slopping prediction. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  • 2.
    Doostmohammadi, H.
    et al.
    KTH.
    Jönsson, P.G.
    KTH.
    Komenda, Jacek
    RISE, Swerea, Swerea KIMAB.
    Hagman, S.
    Ovako Bar.
    Inclusion characteristics of bearing steel in a runner after ingot casting2010In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 81, no 2, p. 142-149Article in journal (Refereed)
    Abstract [en]

    In the uphill teaming method of ingot casting molten metal from the ladle goes into the runner system, which feeds one or several ingot moulds. This method is still important for production of bearing steel. In order to make clean steel, which has a controlled amount of inclusions, good understanding of inclusions characteristics is necessary. In this work non-metallic inclusions of steel left in the runner part of an ingot casting system were studied. Inclusion type, size, and morphology were the main focus of this study. A scanning electron microscope (SEM) was used to assess inclusion size and morphology. The chemical composition of inclusions was determined by SEM equipped with EDS. An automated program called 'INCAFeature' was used to collect statistics of inclusion characteristics. Based on the statistical analysis of inclusion composition, four types of inclusions including oxides, sulfides, carbonitrides and complex inclusions were defined. The inclusion characteristics in the runner were also compared to literature data of inclusions found in ladle and mould samples. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  • 3.
    Däcker, Carl-Åke
    et al.
    RISE, Swerea, Swerea KIMAB.
    Sohlgren, T.
    SSAB EMEA.
    The influence of mould powder properties on shell formation in continuous casting of steels2010In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 81, no 10, p. 899-907Article in journal (Refereed)
    Abstract [en]

    For peritectic steel grades the shell formation is uneven resulting in quality problems such as surface cracks. Production of these steels calls for good control and knowledge of the critical factors for shell formation. By optimisation of process parameters, it is possible to enable production of crack sensitive slabs for heavy plate. This also gives a unique possibility to study the interaction between process parameters and shell formation. The paper presents the results from two large investigations with this ambition covering the total of 27+30 heats of 220 tons of steel at SSAB EMEA-Oxelösund and concludes how surface cracks can be significantly decreased. © 2010 Wiley-VCH Verlag GmbH & Co.

  • 4.
    Granbom, Y.
    et al.
    SSAB Strip Product Division.
    Ryde, Lena
    RISE, Swerea, Swerea KIMAB.
    Jeppsson, J.
    Royal Institute of Technology.
    Simulation of the soaking and gas jet cooling in a continuous annealing line using dilatometry2010In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 81, no 2, p. 158-167Article in journal (Refereed)
    Abstract [en]

    The present study concerns the simulation of a continuous annealing line (CAL), using dilatometry. Simulations of CAL have been performed on four commercial steel grades with different chemical compositions in order to investigate how the alloying elements C, Mn, Si and B affect the microstructure and hardness of dual phase (DP) and martensitic steels. Three annealing cycles corresponding to those used in a CAL have been applied. When annealing intercritically, as is the case in DP-steel production, the materials do not reach equilibrium during soaking. Mn and C increase the austenite content and consequently the hardness of the materials. Higher levels of Si (0.4 wt %) are required to retard the formation of new ferrite during cooling in the gas jet section, prior to quenching. B increases hardenability effectively when annealing in the austenite region but is not as efficient during intercritical annealing, which implies that boron restrains ferrite nucleation rather than impeding ferrite growth. Results from DICTRA calculations show that it is possible to simulate the phase transformations during soaking, gasjet cooling and quenching. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  • 5.
    Hansén, Thorbjörn
    et al.
    MEFOS − Metallurgical Research Institute AB.
    Jönsson, P.
    KTH.
    Lundberg, S.-E.
    Örebro University.
    Torresvoll, K.
    Ovako Steel.
    The concept of the liquid sampling and hot rolling method for determination of macro inclusion characteristics in steel2006In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 77, no 3, p. 177-185Article in journal (Refereed)
    Abstract [en]

    A novel method for determination of semi-macro and macro size distributions of inclusions in steel from samples in ladle, tundish and mould has been developed. The samples are worked and surface treated before inspection. Mainly immersed ultrasonic scanning is performed to determine the semi-macro and macro inclusion content. The LSHR method has been tested in several different steel plants and for different steel grades. It is concluded that new information regarding large inclusions during steelmaking can be obtained using the method.

  • 6.
    Hansén, Thorbjörn
    et al.
    MEFOS − Metallurgical Research Institute AB.
    Runnsjö, G.
    Outokumpu Stainless.
    Sundqvist, O.
    Sandvik Materials Technology.
    Jönsson, P.
    KTH.
    The use of the LSHR sampler to determine total oxygen contents in the ladle and tundish for different steel grades2006In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 77, no 8, p. 550-557Article in journal (Refereed)
    Abstract [en]

    The LSHR sampler is a new development for providing a sample volume large enough to study semi-macro and macro inclusions in clean steel. During the development of the LSHR sampler it was found that the pin where the steel enters the sampler can be used for the determination of the total oxygen content. Therefore, samples were taken at several different steel plants both in the ladle and the tundish as well as for the following five different steel grades: bearing steel, stainless steel 304L and 316L, DWI steel and ULC steel. The general conclusion regarding the sampling is that it was successful for all conditions and steel grades studied. The sample pins were examined for total oxygen content using both the inert-gas-fusion method and the fractional-gas-analysis method. Thereafter, the standard deviations with respect to the total oxygen data were used as a measure of the samples reliability. The general conclusion regarding the total oxygen determinations is that they were accurate for the five steel grades studied and the conditions under which the sampling took place.

  • 7.
    Hellberg, Per Erik
    et al.
    MEFOS − Metallurgical Research Institute AB.
    Jonsson, T.L.I.
    KTH.
    Jönsson, P.G.
    KTH.
    A mathematical model of a blast furnace injection tuyere2005In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 76, no 11, p. 755-763Article in journal (Refereed)
    Abstract [en]

    One way to further utilise produced gases in an integrated metallurgical plant is to replace oil with gas as a reducing agent in a modern blast furnace. Accordingly, it is of great interest to study the injection of reducing gas into the blast furnace. Therefore, a three-dimensional mathematical model has been developed which simulates the injection of the gas by lances into the tuyere. The model includes the coupled solution of the flow field and the chemical reaction of the gases in the tuyere. Two different types of fuel gas, coke oven gas (COG) and basic oxygen furnace gas (BOF) have been modelled using one injection lance. The modelling technique is presented and discussed as well as the implied results. Furthermore, process parameters such as different gas compositions etc. are investigated using the developed model. Not surprisingly, the main results show that the COG is combusted more completely than BOF gas, which leads to higher flame temperature of the blast putting demand forward to lower the heat load of the tuyere. However, the modelling of the raceway is as far not included in the model, hence the influence of the outlet boundary condition at the tuyere is not reflected in the presented results.

  • 8.
    Hu, Xiangfeng
    et al.
    RISE - Research Institutes of Sweden, Swerea, Swerea MEFOS. Luleå University of Technology, Sweden.
    Sundqvist Ökvist, Lena
    RISE - Research Institutes of Sweden, Swerea, Swerea MEFOS. Luleå University of Technology, Sweden.
    Eriksson, Johan
    RISE - Research Institutes of Sweden, Swerea, Swerea MEFOS.
    Yang, Qixing
    Luleå University of Technology, Sweden.
    Björkman, Bo
    Luleå University of Technology, Sweden.
    Direct Alloying Steel with Chromium by Briquettes Made from Chromite Ore, Mill Scale, and Petroleum Coke2017In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 88, no 5, article id 1600247Article in journal (Refereed)
    Abstract [en]

    In this work, the effectiveness of using briquettes made from chromite ore, mill scale, and petroleum coke for direct chromium alloying is tested by induction furnace trials carried out in three different scales. The experimental results show that steel scrap can be alloyed with chromium by the chromite ore in the briquettes and the Cr yield from the chromite ore increases with the increase in mill scale addition to the briquettes: the more mill scale is added to the briquettes, the lower the mass ratio of Cr to (Cr + Fe) would be, leading to a higher Cr yield from the chromite ore. Specifically, the maximum Cr yield from the chromite ore is 99.9% when the mass ratio of Cr to (Cr + Fe) in the briquettes is 0.05, and being 93.0% when the ratio is 0.10. However, when the ratio of Cr to (Cr + Fe) in the briquettes reaches 0.20, the maximum Cr yield is only 67.1%. The reduction of chromite ore under the present experimental conditions is promoted by a solid-state reduction mechanism.

  • 9.
    Lagergren, J.
    et al.
    Jernkontoret.
    Wanhelm, T.
    Technical University of Denmark.
    Precz, W.
    Technical University of Denmark.
    Henningsen, P.
    Technical University of Denmark.
    Arentoft, M.
    Technical University of Denmark.
    Jonsson, Nils Göran
    MEFOS − Metallurgical Research Institute AB.
    A new transducer for local load measurements of friction and roll pressure in cold flat rolling2006In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 77, no 6, p. 430-438Article in journal (Refereed)
    Abstract [en]

    The only way to establish the true rolling pressure and the true friction condition in cold rolling is to conduct measurements in the roll bite. A new transducer design is therefore proposed, in order to overcome problems in previous measurements In the past 70 years. The new idea Is to increase the contact surface of the transducer, to be larger than the arc of contact. This Is in contrast to the smaller and smaller contact pin design that has been prevailing. The measurements were conducted during cold dry rolling of both copper strips and stainless steel strips In a pilot mill. The recordings were selected from a steady state with no disturbance from the material flow. The transducer was able to simultaneously measure both the normal pressure and the friction stress. An estimation of the coefficient of friction was accordingly performed. The new transducer works very well, it was seen to be robust and able to avoid signal disturbance. The pressure and friction stress distribution results was as expected by the authors and showed good reproducibility, together with a proven agreement between recorded and simulated signals.

  • 10.
    Lindell, David
    et al.
    RISE, Swerea, Swerea KIMAB.
    Ekman, T.
    Aga Ab.
    Pettersson, R.
    Jernkontoret.
    Fast and efficient annealing of stainless steel strip using oxyfuel burners2015In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 86, no 5, p. 557-566Article in journal (Refereed)
    Abstract [en]

    Pilot plant and annealing experiments have been conducted to study the effect of the higher water content in oxyfuel annealing on oxidation and pickling of cold rolled stainless steel. The experiments were conducted on the austenitic grade AISI 304 in a propane-fired furnace using air and pure oxygen as oxidizers. The experiments were conducted at 1050-1200 °C for typically less than 60 s, in order to simulate industrial annealing of thin strip. Supplementary laboratory annealing trials were made to study the evolution of the microstructure during fast heating rates and short hold times. Increasing the water content from 15 to 50 mol% did not alter the oxidation kinetics or the chemistry of the oxide. Since the oxidation is not altered significantly, the pickling performance of the material remains unchanged. The presence of spalled areas increased the pickling efficiency significantly but this was only seen for material annealed at higher temperature compared to industrial practice. Oxyfuel combustion allows higher heat input and therefore faster heating. The 304 grade recrystallizes readily even at moderate cold rolling reductions so the total annealing time can be reduced substantially if the heating rate can be increased. The present work suggests that this can be done without any downstream effects. Pilot plant annealing experiments have been conducted to study the effect of the higher water content, caused by altering the oxidizer in combustion furnaces, on oxidation and pickling of cold rolled stainless steel. Characterization of oxide, microstructure, mechanical properties, and pickling response suggests that the increasing the water content from 15 to 50 mol% does not result in any negative downstream effects. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  • 11.
    Lindell, David
    et al.
    RISE, Swerea, Swerea KIMAB.
    Pettersson, R.
    Outokumpu Stainless.
    Pickling of process-oxidised austenitic stainless steels in HNO 3-HF mixed acid2010In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 81, no 7, p. 542-551Article in journal (Refereed)
    Abstract [en]

    Oxide formation during production annealing and the subsequent pickling response in mixed acid have been studied. The aims were to characterise the oxides formed and to understand how the pickling mechanism and kinetics are affected by the nature of the oxide. Totally, eight different versions of the austenitic stainless steel grades AISI 301, 304L and 309L were studied, all annealed in production lines. Cold rolled oxides (formed during annealing) are thin (< 1 μm), dense and formed in a multilayered manner. Hot rolled oxides (formed during reheating, hot rolling and annealing) are thicker (>1 μm) and more heterogeneous in thickness and composition. The dissolution rate of the chromium depleted layer (CDL) under the oxide is the most important factor for the overall pickling rate. The permeability of acid through the oxide and the tendency of the oxide to spall are also important factors affecting the pickling kinetics. The dense oxide formed on cold rolled materials can to some extent hinder the acid to reach the CDL. The oxides on hot rolled materials are porous and do not provide such a barrier but they are thicker and thereby more difficult to remove. Shot-blasting prior to pickling of the hot rolled materials improves the pickling performance because it thins the oxide, improves the permeability and increases the tendency of the oxide to spall during the pickling step. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  • 12.
    Lindvall, Mikael
    et al.
    RISE, Swerea, Swerea MEFOS.
    Rutqvist, E.
    LKAB Technology and Business Development.
    Ye, Guozhu
    RISE, Swerea, Swerea MEFOS.
    Björkvall, Johan
    RISE, Swerea, Swerea MEFOS.
    Sichen, D.
    Royal Institute of Technology.
    Possibility of selective oxidation of vanadium from iron and phosphorus in Fe-V-P melt2010In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 81, no 2, p. 105-111Article in journal (Refereed)
    Abstract [en]

    Experiments on a vanadium recovery method from vanadium containing BOF-slag using both a Tamman furnace (3 kg scale) and an induction furnace (150 kg scale) were conducted. The vanadium was extracted into the slag phase by bubbling oxidation gas into a metal bath consisting mainly of V (1-10 mass%), Si (less than 1 mass%) and P (about 1 mass%). The first experiments revealed that the slag formed during oxidation reaction had considerably high phosphate capacity. High phosphorus content would rule out the possibility of using the slag as a raw material for the production of ferrovanadium of high quality. In order to reduce the P-content in the slag, addition of slag former to reduce phosphate capacity was necessary. A suitable slag system (having the initial composition 40 mass% Al2O3 - 25 mass% CaO - 35 mass% SiO2) and a suitable atmosphere, by using CO2, that enhanced the oxidation of vanadium, but limit the oxidation of iron and phosphorus was found. However, more efforts should be put forward, e.g. study of the phase diagram, the viscosity of the slag and even oxide activities to gain more insight into the slag formed by selective oxidation. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  • 13.
    Nyström, Ralph
    et al.
    MEFOS − Metallurgical Research Institute AB.
    Spitzer, K.-H.
    Technical University of Clausthal.
    Development of Soft Reduction at Inexa Profil for the Possibility of Increased Productivity with Maintained or Improved Product Quality2003In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 74, p. 700-707Article in journal (Refereed)
    Abstract [en]

    When Inexa planned to increase charge weights, it was important to increase productivity of the caster in order to meet the requirements from the primary furnaces. With the existing caster and for certain grades difficulties arise to meet quality standards at increased casting speed. To counteract this problem soft reduction technique was planned to be developed. A solidification model of the Inexa bloom caster was developed using the software package TEMPSIMU to aid in the design of a soft reduction unit. Additionally, a 3-dimensional solidification model of the crater end position and shape during transient casting conditions was developed using the software THERMAL TRACKING. Shell thickness measurements using the wedge method were conducted for calibration of these models. A soft reduction unit was built and installed in one strand of the Inexa bloom caster. Soft reduction trials were carried out on the caster. The result from the trials indicated that it is possible to improve or maintain the centre quality of the blooms at increased casting speed with the installed soft reduction unit.

  • 14.
    Randelius, Mats
    et al.
    RISE, Swerea, Swerea KIMAB.
    Krantz, Therese
    RISE, Swerea, Swerea KIMAB.
    Melander, Arne
    RISE, Swerea, Swerea KIMAB.
    Experimental testing and computer simulations of ductile fracture in tool steels2012In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 83, no 1, p. 91-99Article in journal (Refereed)
    Abstract [en]

    Ductility was determined in experimental four-point bending tests of smooth specimens of tool steel. The tool steels had different contents of carbides and carbide sizes and with a hardness of approximately 60HRc. Two of the materials tested were produced powder metallurgically, one was spray formed and one was conventionally uphill ingot cast. Carbide size distribution analysis was performed on planar polished sections of each material. Correlation between carbide microstructure and ductility performance was obtained. The fracture mechanisms were investigated with fractography. A 3D FE-model was used to simulate the four-point bending tests and thereby analyse the matrix flow curve. Also the strain at failure was analysed for each material when simulations were performed based on experimental data. SEM-images of the materials carbide microstructure were used to create 2D FE-models. The models simulated crack initiation and propagation by removing elements in the steel matrix as the plastic strain reached a critical level. With three variants, simulations of crack initiation and propagation at carbides were investigated. That was carbides with no cohesion to matrix, carbides fixed to the matrix and carbides with internal cracks. Comparison of strains at failure for the 2D and the 3D FE-models showed good correlation. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  • 15.
    Randelius, Mats
    et al.
    RISE, Swerea, Swerea KIMAB.
    Sandström, Rolf
    RISE, Swerea, Swerea KIMAB.
    Melander, Arne
    RISE, Swerea, Swerea KIMAB.
    Fatigue strength of conventionally cast tool steels and its dependence of carbide microstructure2012In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 83, no 1, p. 83-90Article in journal (Refereed)
    Abstract [en]

    The axial fatigue strength at two million cycles was experimentally determined for two conventionally cast tool steels and successfully compared with results from a fatigue limit model. Specimens were tested both in the rolling and transverse direction and showed large differences in fatigue properties due to the segregated carbide microstructure. Rolling direction specimens experienced higher fatigue strength than the transverse direction specimens. This is due to smaller carbides present in the load affected cross section of the rolling direction fatigue test bars compared to the cross section of the transverse direction fatigue test bars. Fractographic analysis of failed specimens showed that large carbides had caused fatigue failure, which was also predicted by the model. Measured size distributions of carbides and inclusions were used as input data in the model. The probability that at least one particle will be present in the material volume having a size larger than the threshold value for crack propagation was calculated. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  • 16.
    Safavi Nick, Reza
    et al.
    RISE, Swerea, Swerea MEFOS.
    Tilliander, A.
    KTH Royal Institute of Technology.
    Jonsson, L.T.I.
    KTH Royal Institute of Technology.
    Jönsson, P.G.
    KTH Royal Institute of Technology.
    A mathematical model of the solid flow behavior in a real dimension blast furnace: Effects of the solid volume fraction on the velocity profile2013In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 84, no 10, p. 999-1010Article in journal (Refereed)
    Abstract [en]

    A mathematical model based on the continuum mechanic concept has been developed to describe the profile of solid particles in a blast furnace with respect to the in-furnace conditions and characteristics, e.g., 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 equation has been modified to make it possible to describe the dual nature of the solid phase in the system by applying the concept of the solid surface stress to characterize the inter-granular surface interactions between particles. Since different phases co-exist in a blast furnace, the volume fraction plays an important role in a blast furnace. Therefore, the influence of three different packing densities (0.68, 0.71, and 0.74, respectively) on the profile of the flow in the upper part of a furnace down to the tuyeres level has been studied. It is shown that an increase in the volume fraction of the solid phase lead to a decrease in magnitude of the velocity. The decrease in the magnitude of the velocity due to an increase in the solid volume fraction will increase the resident time of the particles inside a blast furnace. In addition, it is shown that the solid phase velocity magnitude decreases from the throat to the belly of the furnace for the studied conditions. However, after belly the velocity magnitude increases. It is shown that the particle velocity increases in the upper part of the furnace up to the tuyeres level with a decrease in the packing density from 0.74 to 0.71 and 0.68 while all other parameters were keptconstant. The shrinkage in the size of the particles is not applied to the model. However it is plausible to say that an increase in the packing density of the bed decreases the velocity magnitude. This, in turn, increases the resident time of the particles. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  • 17.
    Solhed, Henrik
    et al.
    MEFOS − Metallurgical Research Institute AB.
    Jonsson, L.
    KTH.
    Jönsson, P.
    KTH.
    Modelling of the steel/slag interface in a continuous casting tundish2008In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 79, no 5, p. 348-357Article in journal (Refereed)
    Abstract [en]

    It is very important to understand the underlying physical phenomena at the steel/slag interface in a continuous casting tundish in order to control reoxidation and deoxidation phenomena that can occur. Aiming to investigate probable sources of exogenous inclusions originating from the covering slag, an existing mathematical model of the tundish was augmented to include key physical parameters needed for the prediction of the physical behaviour of steel/slag mixing phenomena. Results showed a recirculation flow in the inlet region to be responsible for both the entrainment of steel drops into the slag and slag fragments into the steel. The highest concentration of slag in the steel was found to be in the area behind the inlet where slag fragment sizes are smaller due to a high degree of turbulent energy dissipation. Likewise, higher concentrations of steel in the slag, consisting of smaller steel droplets, were only found in the inlet region and along the walls. The results indicate that only small slag fragments of approximately 10-50 microns from the covering slag reach the outlet.

  • 18.
    Thunman, M.
    et al.
    Royal Institute of Technology.
    Eckert, S.
    Forschungszentrum Dresden-Rossendorf (FZD).
    Hennig, O.
    Forschungszentrum Dresden-Rossendorf (FZD).
    Björkvall, Johan
    MEFOS − Metallurgical Research Institute AB.
    Sichen, D.
    Royal Institute of Technology.
    Study on the formation of open-eye and slag entrainment in gas stirred ladle2007In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 78, no 12, p. 849-856Article in journal (Refereed)
    Abstract [en]

    Laboratory experiments were carried out to study the phenomena related to open-eye formation in ladle treatment. Ga-In-Sn alloy with a melting temperature of 283 K was used to simulate the liquid steel, while MgCl2- Glycerol(87%) solution as well as HCl solution were used to simulate the ladle slag. No open-eye was formed at lower gas flow rates, but, occurred when gas flow reached a critical rate. This critical gas flow rate was found to depend significantly on the height of the top liquid. No noticeable amount of top liquid was observed in any of the samples taken from the metal bulk during gas stirring. To confirm this aspect, samples of slag-metal interface were taken around the open-eye in an industrial gas stirred steel ladle. No entrapped slag droplet was found in the solidified steel within the region between the interface and 2 cm from the interface. The accordance of the laboratory and industrial results suggests that the entrainment of slag into the steel bulk around the open-eye cannot be considered as the major contribution to inclusion formation.

  • 19.
    Wang, Chuan
    et al.
    RISE, Swerea, Swerea MEFOS.
    Brämming, Mats
    SSAB EMEA.
    Larsson, Mikael
    RISE, Swerea, Swerea MEFOS.
    Numerical model of scrap blending in BOF with simultaneous consideration of steel quality, production cost, and energy use2013In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 84, no 4, p. 387-394Article in journal (Refereed)
    Abstract [en]

    At its integrated steel plant in Luleå, SSAB EMEA produces high strength steel via two basic oxygen furnaces (BOFs), type LD/LBE. The BOFs are charged with a mix of hot metal, scrap, and slag formers. The scrap has several functions, for example, as coolant to balance excess heat, and it contributes to high steel production rate and decreased CO2 emission. The optimal scrap to hot metal ratio is influenced by several factors, for example, the excess heat generated in the BOF versus target value of tapping temperature, content of contamination elements versus contents allowed in the steel, possible use of alloys in scrap to decrease the need of alloy addition and the scrap price versus the production cost of hot metal. The first two factors also affect the maximum amount of scrap to be charged. Furthermore, the available scrap exists as several types with different composition, properties, size, and price. For most scrap types there are also uncertainties in composition, which has to be considered. An optimization model has been further developed in combination with some statistic analysis techniques. The present work is focusing on the possibility to use the model as a tool to optimize and control raw material/scrap blending into the BOFs. On the basis of the statistical analysis technique, the scrap sorting in the model will be described, as well as development and introduction of an extended BOF sub-model. This model includes a scrap sorting function and a response on deviations in steel quality. Real production data is used to identify steel quality parameters with consideration of different combination of elements, for example, S, Cr, Ni, and Cu. The possible solutions with simultaneous consideration of steel quality, energy consumption and production cost are presented. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  • 20.
    Wessman, Sten
    et al.
    RISE, Swerea, Swerea KIMAB.
    Pettersson, R.
    Jernkontoret - The Swedish Steel Producers' Association.
    Application of computational thermodynamics to predict growth of intermetallic phases in superduplex stainless steels2015In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344XArticle in journal (Refereed)
    Abstract [en]

    Computational thermodynamics were used to predict the growth of intermetallic phases in superduplex stainless steels, assuming that it is the ferrite which primarily decomposes during heat treatments below 1000°C. Sigma and chi phase were modeled to form at the edge of a 10μm ferrite unit and the time from 0.1s to the development of a 100nm layer of the phase in question was evaluated. This approach encompasses thermodynamics and kinetics of growth of the intermetallic phases but omits nucleation. Nevertheless the calculations accurately predict the classic C-shaped TTT curves, in which "nose" the growth is most rapid with a critical combination of precipitation, diffusion, and driving force. Verification of the relevance of the model was done by comparison with a publication with experimental studies of molybdenum and tungsten alloyed superduplex stainless steel weld metals, showing that partial substitution of Mo of by W does cause a more rapid growth of intermetallic phases. In addition the effect of the partial substitution of nickel by copper was examined and showed that copper decreases the amount of sigma phase and also reduces its growth rate. The results also suggest that the time for nucleation is of less importance in this context than previously suggested and thermodynamics and kinetics are sufficient to give an adequate explanation to the experimental results. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  • 21.
    Wessman, Sten
    et al.
    RISE, Swerea, Swerea KIMAB.
    Pettersson, R.
    Outokumpu Stainless AB.
    Hertzman, S.
    Outokumpu Stainless Research Foundation.
    On phase equilibria in duplex stainless steels2010In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 81, no 5, p. 337-346Article in journal (Refereed)
    Abstract [en]

    The equilibrium conditions of four duplex stainless steels; Fe-23Cr-4.5Ni-0.1N, Fe-22Cr-5.5Ni-3Mo-0.17N, Fe-25Cr-7Ni-4Mo-0.27N and Fe-25Cr-7Ni-4Mo-1W-1.5Cu-0.27N were studied in the temperature region from 700 to 1000 8C. Phase compositions were determined with SEM EDS and the phase fractions using image analysis on backscattered SEM images. The results showed that below 1000° the steels develop an inverse duplex structure with austenite and sigma phase, of which the former is the matrix phase. With decreasing temperature, the microstructure will be more and more complex and finely dispersed. The ferrite is, for the higher alloyed steels, only stable above 1000 ° and at lower temperatures disappears in favour of intermetallic phases. The major intermetallic phase is sigma phase with small amounts of chi phase, the latter primarily in high Mo and W grades. Nitrides, not a focus in this investigation, were present as rounded particles and acicular precipitates at lower temperatures. The results were compared to theoretical predictions using the TCFE5 and TCFE6 databases.

  • 22.
    Wessman, Sten
    et al.
    RISE, Swerea, Swerea KIMAB.
    Wilson, A.
    AB Sandvik Materials Technology.
    Hertzman, S.
    Outokumpu Stainless Research Foundation.
    Pettersson, R.
    Jernkontoret.
    An experimental and theoretical evaluation of microstructure coarsening in duplex stainless steels2013In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 84, no 11, p. 1126-1137Article in journal (Refereed)
    Abstract [en]

    The coarsening of duplex stainless steel microstructures at temperatures above 1000°C was investigated experimentally and theoretically. Hot-rolled duplex 2205 and superduplex 2507 samples were heat treated isothermally at 1100°C up to 700 h, and also between 1000 and 1250°C for 24 h. The ferrite content and the microstructure coarseness, quantified by the measured austenite spacing, AS, were evaluated. It was found that the observed coarsening could be described using Ostwald ripening theory expressed as AS n-AS0 n=kt, where AS0 is austenite spacing of the as-delivered material, k the rate constant, n the exponent, and t the heat treatment time. Using regression analysis, n and k were evaluated and the resulting predictions compared with literature theories and results. The results were also calculated according to the original Lifshitz, Slyozov, Wagner (LSW) theory with parameters taken from literature, as well as with the Dictra software for diffusion and growth in multicomponent systems. The calculations indicated that while the classical LSW theory failed to give a good description of the experimental results, the Dictra simulations proved very accurate, even though systems of equal ferrite and austenite content are considerably outside the intended range of applicability of the software. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  • 23.
    Wikström, Jan-Olov
    RISE, Swerea, Swerea MEFOS.
    Scanmet III - 3rd international conference on process development in iron and steelmaking2009In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 80, no 6, p. 377-Article in journal (Refereed)
1 - 23 of 23
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