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  • 51.
    Jönsson, Pär
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Aune, Ragnhild E.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Du, Sichen
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Teng, Lidong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Matsushita, Taishi
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Sundberg, Sven
    The Seetharaman Seminar June 14-15, 2010 in Stockholm, Sweden2012In: High Temperature Materials and Processes, ISSN 0334-6455, E-ISSN 2191-0324, Vol. 31, no 3, p. 193-193Article in journal (Other academic)
  • 52.
    Jönsson, Pär
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jonsson, Lage
    KTH, Superseded Departments, Metallurgy.
    Sichen, Du
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Viscosities of ld slags and their impact on ladle refining1997In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 37, no 5, p. 484-491Article in journal (Other academic)
  • 53.
    Jönsson, Pär
    et al.
    KTH, Superseded Departments, Applied Process Metallurgy.
    Jonsson, Lage
    KTH, Superseded Departments, Applied Process Metallurgy.
    Sichen, Du
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Viscosities of LF slag’s and their impact on ladle refining1997In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 37, no 11, p. 484-491Article in journal (Refereed)
  • 54. Kang, Y.
    et al.
    Thunman, Mikael
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Sichen, Du
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Morohoshi, Takashi
    Mizukami, Kazumi
    Morita, Kazuki
    Aluminum Deoxidation Equilibrium of Molten Iron-Aluminum Alloy with Wide Aluminum Composition Range at 1873 K2009In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 49, no 10, p. 1483-1489Article in journal (Refereed)
    Abstract [en]

    Al-0 equilibria in molten Fe-Al alloys were experimentally investigated. Molten steel with varying Al content (0.01-10 mass%) was equilibrated with a pure Al2O3(S) crucible at 1873 K in an Ar atmosphere with 3 vol% H-2, The oxygen content of steel with Al content higher than 1.0 mass% was found to be much lower than that found in previous works, while the oxygen content for Al content less than I mass% was found to be slightly higher, resulting in a smaller equilibrium constant. The interaction parameters as well as the equilibrium constant of the Al-O equilibria in molten steel at 1 873 K were reevaluated in the present study. The equilibrium for the Al deoxidation of molten steel was well represented up to 10.0 mass% Al using the reevaluated parameters.

  • 55.
    Kang, Young Jo
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Some aspects of non-metallic inclusions during vacuum degassing in ladle treatment: with emphasize on liquid CaO-Al2O3 inclusions2007Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The present thesis was to study non-metallic inclusions during vacuum degassing in ladle treatment. Emphasize was mostly given to liquid CaO-Al2O3 inclusions. A series of industrial experiments were carried out at Uddeholm Tooling AB, Hagfors, Sweden. To gain an insight into the industrial findings, laboratory investigations were also performed.

    Large number of steel samples were collected and examined. Liquid calcium aluminate inclusions with low SiO2 and high SiO2 were often found with spinel inclusions before vacuum degassing. Laboratory experiments showed that spinel would react with the dissolved Ca in the liquid steel forming calcium aluminate inclusions. This laboratory results agreed with the industrial observation that spinel phase was quite often found in the center of the calcium aluminate phase.

    After vacuum degassing, most of the inclusions were calcium aluminate liquid inclusions. When dissolved Al level was low, 2 types of liquid calcium aluminate inclusions with considerably different SiO2 contents were found to coexist even at the end of the process. In view of the lack of the thermodynamic data for SiO2 activities in the low silica region, thermodynamic measurements were conducted in the CaO-Al2O3-SiO2-MgO system. The experimental results could reasonably explain the coexistence of the two types of the liquid oxide inclusions.

    While the total number of inclusions decreased during vacuum degassing, the number of bigger inclusions (>11.3 μm) increased generally in used ladles. This finding was in accordance with the previous studies, wherein, ladle glaze was found to be responsible for the supply of bigger inclusions.

    The behaviors of several types of inclusions in liquid steel were examined using a laser scanning confocal microscope (LSCM). While alumina inclusions tended to impact on each other, agglomerate and grow very quickly, none of the other types of inclusions, such as spinel and calcium aluminate was observed to agglomerate. The results of LSCM study agreed well with the industrial observation. Examination on a huge number of inclusions did not show any indication of impact and physical growth of the inclusions, except the alumina inclusions.

    The removal of inclusions around open-eye in a gas-stirred ladle was experimentally studied by a cold model with oil and water. Most of the simulated inclusions were brought up to the oil phase by gas-water plume. Inclusion removal into oil layer took place when the inclusions passed through the sphere-bed of the oil layer around the open-eye. A calculation showed that the contribution of metal-gas plume in inclusion removal was much larger than that of buoyancy mechanism.

    The results of the industrial experiments revealed that the inclusions distribution strongly depended on stirring condition. When a ladle was stirred by both gas and induction, inclusion removal near slag layer was significant.

  • 56.
    Kang, YoungJo
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Li, Fan
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Morita, Kazuki
    Institute of Industrial Science, University of Tokyo.
    Sichen, Du
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Mechanism study on the formation of liquid calcium aluminate inclusion from MgO.Al(2)O(3) Spinel2006In: Steel Research International, ISSN 1611-3683, Vol. 77, no 11, p. 785-792Article in journal (Refereed)
    Abstract [en]

    A study on the formation mechanism of liquid calcium aluminate inclusions from MgO center dot Al2O3 spinel was carried out. It was found that spinel reacted with dissolved Ca in liquid steel forming liquid calcium aluminate phase. Stability calculations showed good agreement with the experimental result. According to the thermodynamic calculation, liquid calcium aluminate inclusions would form from spinel even at very low level of dissolved Ca content at 1873 K. At lower temperatures, the compound CaO center dot 2Al(2)O(3) was found to be the stable phase at the spinel-metal interface. Potential sources of dissolved Ca during ladle processes were also discussed.

  • 57.
    Kantarp, Robbin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Theoretical consideration about optimising casting parameters in DC Casting of aluminium alloys2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Optimised casting parameters in direct-chill casting are of great importance to manufacture crack sensitive aluminium alloys. The aim of this thesis is to develop a theoretical model to optimise casting parameters at Sapa Heat Transfer´s cast house in Finspång.

    The model is an energy balance describing the difference between in- and out-going metal inside the mold, enthalpy in cooling water and losses to the surrounding during steady-state casting. A theoretical study is done to identifying the parameters of influence and with optimising potential.

  • 58.
    Kazemi, Mania
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Reduction of Hematite Pellets with CO-H2 Mixtures2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 59.
    Kazemi, Mania
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Glaser, Bjoern
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Sichen, Du
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Study on Direct Reduction of Hematite Pellets Using a New TG Setup2014In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 85, no 4, p. 718-728Article in journal (Refereed)
    Abstract [en]

    A new thermogravimetric setup was developed to study direct reduction of iron oxide under well-controlled experimental conditions. Pure and industrial hematite samples were isothermally reduced by hydrogen and carbon monoxide gaseous mixtures. Influences of gas composition, gas flow rate, and temperature on reduction were investigated. Reduction rates obtained using the new setup were higher compared to conventional thermogravimetric method. This difference was due to the time required to replace the inert gas with the reactant gas in the conventional method, which led to lower reduction rate at the initial stage. Carbon deposited on the surface of the pellets at relatively high gas flow rates and at low temperatures. The presence of pure iron and high carbon potential in the gas phase were the cause for carbon deposition. Study of partially reduced samples illustrated that the outer layer of pellet with high iron content thickened as reduction proceeded inside the pellet. Closure of micro-pores and formation of dense iron phase in this layer decelerated diffusion of reactant and product gases, and led to decrease of reduction rate at later stages of reaction. At lower temperatures, this effect was coupled with carbon deposition. Therefore, the reduction was seriously hindered.

  • 60.
    Kojola, Niklas
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Hurtig, Jenny
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Nitrogen and Hydrogen Refining During Vacuum Treatment of Liquid Steel2011In: PR-258-024, 2011, no 6Conference paper (Refereed)
    Abstract [en]

    Nitrogen and hydrogen strongly affects mechanical properties of steel. This is why control of liquid steel nitrogen and hydrogen contents is of the utmost importance. In this paper, the nitrogen and hydrogen refining during vacuum treatment and the variation of nitrogen and hydrogen content in the tundish, have been investigated. The results clearly show that the nitrogen refining depends on the gas pressure inside the tank as well as steel sulfur content and vacuum treatment time, while the hydrogen refining seems to reach equilibrium within the varied process parameters. It is further shown that the nitrogen and hydrogen contents vary during casting. A model predicting this variation as function of time is also presented.

  • 61. Kuma, Jalaj
    et al.
    Tripathi, N
    Sichen, Du
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Importance of interfacial phenomena in the removal of inclusions by gas bubbles from steel – An experimental study using cold model2003In: Steel Grips - Journal of Steel and Related Materials, ISSN 1611-4442, E-ISSN 1866-8453, Vol. 1, p. 133-139Article in journal (Refereed)
  • 62.
    Li, Fan
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Development of Techniques to Produce Nickel Coated Composite Materials as well as Hollow Nickel Fibres and Kinetic Study of the Process Involved2007Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The present thesis was mainly to study the preparation of nickel composite materials by chemical plating process. Nickel coated boron nitride particles, nickel coated spherical silica particles and nickel viscose composite fibres were prepared. Both experiment and model development were carried out to study the kinetics of the processes. Preparation of hollow nickel fibres was also investigated.

    NiSO4-(NH4)2SO4-NH3·H2O-N2H4·H2O was found a suitable system for nickel plating. This system could be employed in preparing nickel coating layer on surface of boron nitride particles, spherical silica powder and viscose fibres. The main factors which could affect the plating process were investigated. The optimum conditions were suggested for different substrate materials based on the experimental results.

    It was found that Pd on the surface of substrate materials acted as an active center for nickel deposition at the initial stage of the process. Thereafter, Ni itself would act as an active center to catch Ni from the solution through the reaction: Ni2+ + 2H* ad ⇒ Ni + 2H+. The rate of the process was found to be controlled by the reaction at the interface under the present experimental conditions. A kinetic model was developed on the basis of the mechanism study. The model predictions were found to be in agreement with the experimental data for different substrate materials. Since the kinetic model does not have any parameters related to the shape and surface area of the substrate, it could be used as a general model to describe the processes controlled by interface reaction with growing interface area.

    Hollow nickel fibers were prepared by thermal decomposition method from nickel viscose composite. The experiments showed that viscose filling could be removed by heat treatment in air atmosphere. Experiments showed that hollow nickel fiber could be prepared by direct thermal decomposition in air flow at low temperature, e.g. 573 K. But slight surface oxide is inevitable. Decomposition of the viscose filling could also be carried at higher temperature. However, serious oxidation of nickel would also take place during the decomposition. To remove nickel oxide, reduction by hydrogen gas could be applied.

    Preliminary effort was made to extend the application of the present method to prepare copper viscose composite fibres. Promising result was obtained. More detailed study is required to confirm the applicability of the technique.

  • 63.
    Li, Fan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Du, Sichen
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Thermodynamic consideration and experimental study on preparation of hollow nickel fibres2008In: International Journal of Materials Research, ISSN 1862-5282, Vol. 99, no 9, p. 1023-1031Article in journal (Refereed)
    Abstract [en]

    In the present work, heat-treated hollow nickel fibres were prepared by thermal decomposition from nickel viscose composite. The thermodynamic properties of viscose fibre, namely standard enthalpy of formation, heat capacity, absolute entropy, and standard Gibbs free energy of formation were estimated by bond enthalpy. Thermodynamic analysis showed that viscose fibres could decompose at any reachable temperature, when the kinetic conditions were favourable. The results of thermogravimetric analysis experiments indicated that viscose filling could be removed by heat treatment in air. The thermogravimetric analysis results along with X-ray diffraction, scanning electron microscopy and X-ray energy dispersive spectrum analysis showed that hollow nickel fibre could be prepared by direct thermal decomposition in air flow at low temperatures, e.g. 573 K. Decomposition of the viscose filling could also be carried out at higher temperatures. However, serious oxidation of nickel would also take place during the decomposition. To remove nickel oxide, reduction by hydrogen gas could be applied.

  • 64.
    Lindstrom, David
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Du, Sichen
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Kinetic Study on Desulfurization of Hot Metal Using CaO and CaC22015In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 46, no 1, p. 83-92Article in journal (Refereed)
    Abstract [en]

    The kinetics and reaction mechanisms of hot metal desulfurization using CaO and CaC2 were studied in a well-controlled atmosphere with a lab scale high temperature furnace. The growths of CaS around CaO and CaC2 were measured and compared at 1773 K (1500 degrees C). The parabolic rate constant was evaluated to be 5 x 10(-7) (cm s(-1)) on CaO particles, and 2.4 x 10(-7) (cm s(-1)) on CaC2. The bigger parabolic constant of CaO resulted in more efficient desulfurization. Agglomerates and big CaO particles led to 2CaO center dot SiO2 formation which hindered further utilization of CaO for desulfurization. The 2CaO center dot SiO2 formation was favoured by a high oxygen potential. Since the desulfurization reaction of CaO not only produced CaS but also oxygen, the local oxygen concentration around big CaO particles was higher than around small particles.

  • 65.
    Lindström, David
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    A Study on Desulfurization of Hot Metal Using Different Agents2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis deals with desulfurization of hot metal using different agents. The aim of this study was to improve the understanding of commonly used desulfurization agents such as fluidized CaO, CaC2, commercial-CaO, Mg, and mixtures of commercial-CaO-Mg. The possibility to use ZnO for desulfurization of hot metal was also investigated. The desulfurization mechanisms and kinetics of these agents were studied. A broad comparison of the desulfurization abilities of the agents was performed under the same experimental conditions. The experimental studies were carried out in a high temperature resistance furnace at 1773 K with good quenching ability and precise control of the oxygen partial pressure.

    The influence of ZnO in blast furnace slag on the sulfur removal potential was studied. It was found that ZnO does not stay in blast furnace slag under relevant oxygen potentials and consequently has no influence on its sulfur removal capacity.

    The reaction mechanism of Mg was studied by adding pure Mg into hot metal. It was found that most Mg (about 90 %) escaped as gas in less than two seconds, only providing a little desulfurization. MgS is not formed by homogenous nucleation, but on MgO particles originating from the surface of the added Mg metal.

    The growth of CaS around CaC2, fluidized CaO and commercial-CaO were measured and compared. The parabolic rate constants were evaluated to be 2.4∙10-7 [cm s-1] for CaC2, and 5∙10-7 [cm s-1] for fluidized CaO particles. The bigger parabolic rate constant of fluidized CaO explains why fluidized CaO achieved a much better desulfurization of hot metal than CaC2 under the same experimental conditions. Commercial-CaO performed less satisfactory in comparison to fluidized CaO powder. This was due to both its less reactive surface and agglomeration of the particles.

    Agglomerates and large CaO particles lead to 2CaO.SiO2 formation which hindered further utilization of CaO for desulfurization. The 2CaO.SiO2 formation was favored by a high oxygen potential. Since the desulfurization reaction of CaO not only produced CaS but also oxygen, the local oxygen concentration around big CaO particles was higher than around small particles.

    When small CaO particles were added together with Mg they quickly transformed to CaS. The Mg-gas helped to distribute the CaO particles in the hot metal and improved the kinetic conditions.

    The desulfurization abilities of some commonly used agents, namely fluidized CaO, CaC2, commercial-CaO, Mg, mixtures of commercial-CaO-Mg, and ZnO were studied and compared under the same experimental conditions. While fluidized CaO showed the best performance, commercial-CaO mixed with 20 mass % Mg achieved the second best desulfurization. Mg-granules performed slightly better than CaC2 and commercial-CaO, but somewhat less satisfactory compared to fluidized CaO and commercial-CaO-Mg mixtures. ZnO does not influence the sulfur concentration of hot metal.

  • 66.
    Lindström, David
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Nortier, P.
    Sichen, Du
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Functions of Mg and Mg-CaO mixtures in hot metal desulfurization2014In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 85, no 1, p. 76-88Article in journal (Refereed)
    Abstract [en]

    The mechanisms of hot metal desulfurization using Mg and Mg-CaO mixtures were studied in a newly designed set-up. It was found that most of the added Mg quickly escaped in 2 s. MgS was not formed by homogeneous nucleation but by its formation on the MgO particles originated from oxide shell of the Mg particles. When tiny CaO particles were added together with Mg, the particles efficiently transformed to CaS. It was found that Mg-gas helped the distribution of the CaO particles in the hot metal and improved the kinetic condition. Most of the CaO particles smaller than 10 μm were completely transformed to CaS whereas CaO particles >10 μm still had CaO in the center after 20 s. The CaO particles as nuclei were also found to help Mg gas in forming MgS. The ratio of CaO and Mg added was found to have strong impact on the kinetic conditions of desulfurization. This ratio would need further study in any reactor of interest, as the kinetic conditions would differ considerably. The optimized ratio is expected to be a function of the size and geometry of the reactor, the position and the depth of the addition, the manner of addition and more. The hot metal desulfurization mechanisms using Mg and Mg-CaO mixtures were studied. Most added Mg quickly escaped in 2 s. MgS was not formed by homogeneous nucleation but by formation on oxide particles. When tiny CaO particles were added together with Mg, Mg-gas helped distribution of CaO particles in hot metal and improved kinetics. Most CaO particles sized <10 μm were completely transformed to CaS whereas CaO particles >10 μm still had CaO in the center after 20 s.

  • 67.
    Lindström, David
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Nortier, Patrice
    Glaser, Björn
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Sichen, Du
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Study on the Possibility of Using ZnO for Hot Metal Desulfurization2013In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 84, no 5, p. 419-425Article in journal (Refereed)
    Abstract [en]

    The possibility of using ZnO for desulfurization in hot metal was evaluated. A lab scale experimental setup was designed so that different desulfurizing agents could be added to hot metal for evaluation of their desulfurizing power. The setup had good control of both temperature and the gaseous atmosphere. It also provided stirring of the metal bath with an impeller as well as quenching facility to maintain the metal composition at high temperature. Desulfurization of hot metal using CaO powder showed evidently the applicability of the new setup. On the other hand, additions of ZnO into the hot metal under various experimental conditions showed no effect on desulfurization. The results were in contradiction to the suggestion found in literature. A thorough examination of the thermodynamic data employed by the previous work was carried out. The data used in the literature were found to be subjected to fundamental mistakes. The present experimental results convincingly rule out the possibility of using ZnO as a desulfurization agent.

  • 68.
    Lindström, David
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Sichen, Du
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Kinetic study on desulfurization of hot metal using CaO and CaC2Manuscript (preprint) (Other academic)
    Abstract [en]

    The kinetics and reaction mechanisms of hot metal desulfurization using CaO and CaC2 were studied in a well-controlled atmosphere with a lab scale high temperature furnace. The growths of CaS around CaO and CaC2 were measured and compared at 1773 K. The parabolic rate constant was evaluated to be 5∙10-7 [cm s-1] on CaO particles, and 2.4∙10-7 [cm s-1] on CaC2. The bigger parabolic constant of CaO resulted in more efficient desulfurization. Agglomerates and big CaO particles led to 2CaO.SiO2 formation which hindered further utilization of CaO for desulfurization. The 2CaO.SiO2 formation was favoured by a high oxygen potential. Since the desulfurization reaction of CaO not only produced CaS but also oxygen, the local oxygen concentration around big CaO particles was higher than around small particles.

  • 69.
    Lindström, David
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Sichen, Du
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Study on Desulfurization Abilities of Some Commonly Used Desulfurization Agents2015In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 86, no 1, p. 73-83Article in journal (Refereed)
    Abstract [en]

    The desulfurization abilities of some commonly used agents, namely fluidized CaO, CaC2, commercial-CaO, Mg, MgO, CaO center dot MgO, and mixtures of commercial-CaO-Mg were studied and compared under the same experimental conditions in a laboratory furnace at 1773 K. The desulfurization mechanisms of CaO center dot MgO, commercial-CaO, and mixtures of commercial-CaO and Mg were also studied. While fluidized CaO showed the best performance, commercial-CaO mixed with 20 mass% Mg achieved the second best desulfurization. Mg-granules performed slightly better than CaC2 and commercial-CaO, but somewhat less satisfactory compared to fluidized CaO and commercial-CaO-Mg mixtures. Since only the CaO portion in CaO center dot MgO functioned to take up sulfur, additional 70% mass had to be added to achieve the same desulfurization level. The poor ability of commercial-CaO in comparison to fluidized CaO powder was due to both its less reactive surface and agglomeration of the particles.

  • 70. Lindvall, M.
    et al.
    Rutqvist, E.
    Ye, G.
    Björkvall, J.
    Sichen, Du
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Possibility of Selective Oxidation of Vanadium from Iron and Phosphorus in Fe-V-P Melt2010In: Steel Research International, ISSN 1611-3683, 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.

  • 71.
    Lindvall, Mikael
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling. Swerea MEFOS.
    A Study on Vanadium Extraction from Fe-V-P Melts Derived from Primary and Secondary Sources2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Vanadium extraction methods were developed for iron-vanadium-phosphorus (Fe-V-P) melts derived from processing of V-bearing titanomagnetites and steel slags. Studies on phase relationships of V slags were carried out to provide important understanding of the extraction processes. Phase relationship in vanadiferous slag was investigated experimentally at 1573K, 1673K and 1773K, for the compositional range of 0-6mass% Al2O3, 1-5mass% CaO, 10-17mass% SiO2, with MnO and V2O3 fixed at 5.5mass% and 30mass%, balanced with FeO. The slags were found to be solid-liquid mixtures, of liquid, spinel and in some cases free silica. Alumina was identified as the preferred additive to prohibit precipitation of free silica. A method for V extraction to vanadiferous slag was developed based on Fe-V(2mass%)-P(0.1mass%) melts at 1677K using a semi-industrial scale BOF. Oxidation was carried out with an oxygen enriched air jet and iron ore pellets. The complete dissolution of pellets was achieved by deliberately creating good stirring conditions utilising high momentary decarburisation rates. The P distribution to the slag was low when good stirring conditions was obtained. Phase relationship in Al2O3-CaO(25-35mass%)-SiO2-VOx slag was investigated experimentally at an oxygen partial pressure of 9.37•10-11atm and 1873K. The maximum solubility of V-oxide in the slag was 9-10mass% V2O3. Two solid phases were found, a solid solution of Al2O3 in V2O3 (karelianite) and hibonite with fractionation of V into the crystal structure. V extraction experiments to Al2O3-CaO-SiO2 based slags were carried out in 150kg scale by blowing CO2 gas into the metal bath consisting mainly of 1-10mass% V and 1mass% P. At these conditions, oxidation of V was favoured over Fe. Up to 10-13mass% V2O3 could be dissolved in the slag before a viscous slag saturated in V-oxide was observed. The phosphate capacity in the slag was low and as a result this slag could at once be subjected to a final reduction step for production of ferrovanadium with 40-50mass% V.

  • 72. Lindvall, Mikael
    et al.
    Sichen, Du
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Determination of Vanadium Solubility in the Al2O3-CaO(30 Mass Pct)-SiO2 and Al2O3-CaO(35 Mass Pct)-SiO2 System2015In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 46, no 2, p. 733-740Article in journal (Refereed)
    Abstract [en]

    The solubility of vanadium oxide in the Al2O3-CaO(30 mass pct)-SiO2 system and Al2O3-CaO(35 mass pct)-SiO2 system was determined experimentally at 1873 K (1600 degrees C) and at a fixed oxygen potential of 9.37 x 10(-11) bar. EPMA microanalyses were employed to identify the phases and their compositions in the quenched samples. The solubility of vanadium oxide in the liquid phase was found to decrease with increasing CaO content in the liquid. The vanadium oxide solubility was especially low when both CaO and Al2O3 contents were high in the liquid phase. The maximum solubility of vanadium oxide was up to 7 mass pct (as V). Two solid phases were found, a solid solution of Al2O3 and vanadium oxide and an Al2O3-rich solid phase with 16.7 mass pct V2O3. The Al2O3 solubility in the solid solution was found to increase with increasing Al2O3 content in the liquid, the impact of the CaO content in the liquid on the solubility of Al2O3 in V2O3 was found to be small. The Al2O3-rich solid phase was identified as the mineral hibonite with fractionation of V into the crystal structure.

  • 73.
    Martinsson, Johan
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    A Study of the Behavior of Foaming Slag in Steelmaking2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The thesis presents a fundamental study on some aspects regarding foaming slag. In today’s society, the requirements on environmental impact and energy consumption are increasing. It is essential for the steel industry to better understand the fundamentals of their processes to be able to develop both the process but also process control to reach the demands. In this work, the basic BOF furnace is the main focus, even though foaming slag may also occur in some electric arc furnaces. The BOF is a chaotic process with the purpose to decarburize and dephosphorize hot metal from the blast furnace. The foaming slag plays a profound role in the kinetics of the reactions, maintains the temperature in the furnace and protects the lining material of the furnace.The first part of the thesis includes a study of the structure of different foams and some viscosity measurements. Both room temperature and high temperature experiments are conducted. It is shown that the apparent viscosity of a foam is not only depending on the dynamic viscosity of the liquid phase and the gas fraction of the foam, but also the surface tension of the liquid and the bubbles size of the foam. The foam appears to show a shear thinning non-Newtonian behavior with apparent viscosities up to 5 times as high as for the pure liquid. The reason is found in the structure of the foams.The behavior of particles falling through foams generated from different sugar solutions is studied in the second part of the thesis. The particle behavior differs a lot depending on the size and density of the particle, and the viscosity and surface tension of the liquid phase. Some particles get stuck in the foam, some heavy particles fall through the foam crushing the bubbles in its path, and some particles fall slowly in a zick-zack pattern towards the bottom. The residence time is also measured, and a semi-empirical model is developed to describe the apparent velocity of the particles falling in a zick-zack pattern.The decarburization is the source of the foam in the furnace, and is studied in the third part of the thesis. Pig iron is dropped into liquid slag and the reaction rate is studied by quenching of samples at different times. Small droplets are decarburized faster than big droplets, and the incubation time of the reaction is found to play a big role in the decarburization process for different slag compositions.ivThe last part of the thesis is a comparison of lime dissolution in liquid versus foaming BOF slags. The controlling dissolution mechanism in liquid slag is the removal of interfacial layers of calcium silicates. In the foam on the other hand, the contact area between liquid slag and lime seem to be the controlling mechanism. In total, the rate seem to be similar in some liquid and foaming slag compositions while in others, the lime is dissociated into small pieces in the foaming slag due to the chaotic environment in the experiment.

  • 74.
    Martinsson, Johan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Glaser, Bjoern
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Sichen, Du
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    The structure of foaming BOF-converter slag2017In: IRONMAKING & STEELMAKINGArticle in journal (Other academic)
  • 75.
    Martinsson, Johan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Sichen, Du
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Decarburization of pig iron in synthetic BOF converter slagManuscript (preprint) (Other academic)
  • 76.
    Martinsson, Johan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Sichen, Du
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Deng, Zhiyin
    School of Metallurgy, Northeastern University.
    A Semi-Empirical Model of Particle Velocity in FoamManuscript (preprint) (Other academic)
  • 77.
    Martinsson, Johan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Sichen, Du
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Glaser, Bjoern
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Lime dissolution in liquid versus foaming BOF slagManuscript (preprint) (Other academic)
  • 78.
    Médioni, Charlotte
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    The effect of stirring practice on the number of inclusions2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 79.
    Nabeel, Muhammad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy. KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Karasev, Andrey
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Glaser, Bjoern
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Characterization of dust generated during mechanical wear of partially reduced iron ore pelletsManuscript (preprint) (Other academic)
    Abstract [en]

    During reduction in a blast furnace (BF), the iron ore pellets undergo structural changes which facilitate dust generation due to the mechanical wear / disintegration of the pellets. The generated dust decreases the permeability and productivity of the BF process. Thus, this study investigates the mechanical wear of iron ore pellets reduced at 500 °C (P500) and 850 °C (P850) and compares the results to the wear of unreduced pellets (P25). Moreover, the dust generated during the wear experiments is also characterized. It was found that pellets reduced at 500 °C exhibit a ~ 16 to 35% higher wear rate than reference unreduced pellets. For the pellets reduced at 850 °C, the mechanical wear is inhibited by a formation of a metallic layer at the outer surface of the pellets. Further, the dust generated due to mechanical wear of reduced pellets contained 3 to 6 times higher amount of coarse particles (>20µm) as compared to the dust from unreduced pellets. The obtained results are explained on the basis of the structural changes which take place during the reduction of pellets. 

  • 80.
    Ragnarsson, Lars
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Formation of non-metallic inclusions and the possibility of their removal during ingot casting2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The present study was carried out to investigate the formation and evolution of non-metallic inclusions during ingot casting. Emphasize have been on understanding the types of inclusions formed and developed through the casting process and on the development of already existing inclusions carried over from the ladle during casting. Industrial experiments carried on at Uddeholm Tooling together with laboratory work and Computational Fluid Dynamics (CFD) simulations.

    Ingots of 5.8 tons have been sampled and the types of inclusions together with their distribution within the ingot have been characterized. Two new types of inclusions have been found. Type C1 is found originated from casting powder and in the size from a few μm to 30 μm. Type C2 is of macro inclusion type sizing up to 70 μm. The presence of C2 inclusions are few but very detrimental for the quality of the steel. Both types, C1 and C2 consist of alumina, indicating that reoxidation is the main reason for their existence.

    The protecting argon shroud has been studied by the use of a 1:1 scaled 2D model. Both flow pattern and oxygen measurement have been carried out. CFD has also been used as an auxiliary tool. It has been found that the oxygen pickup through argon gas shroud depends mostly on the distance between the ladle and the collar placed on top of runner. Further increase of gas flow rate above 2.5 m3.h-1 had very little effect on the oxygen distribution since both the flushing effect and the entraining effect with respect to oxygen are enhanced by further increase of inert gas flow rate. In the case of dual gas inlet, the flow in the shroud was found much less diffused compared with either vertical or horizontal injection system. The oxygen content in this arrangement was also greatly reduced.

    Studies of the runner after casting revealed a sparse non-metallic network structure around the periphery of the steel rod remained in the runner. The surface of the refractory had been severely attacked by the mechanical force from the streaming steel. The erosions of the centre stone and the end stone were on the other hand negligible. CFD calculations showed that the flow at those locations is almost stagnant. The surface of the refractory in contact with the steel was found to have an increased content of alumina. The source for the alumina could come from either exchange reaction of dissolved aluminium replaces the silica or reoxidation products origin from oxygen pick up during the transfer from the ladle to the vertical runner. Inclusions were also found entrapped in the steel refractory interface.

    It was also found that a formation of a liquid slag film as early as possible during casting would increase the possibility to remove inclusions and especially inclusions generated by the casting powder.

  • 81.
    Ragnarsson, Lars
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Ek, Mattias
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Eliasson, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Ceramics.
    Du, Sichen
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Flow pattern in ingot during mould filling and its impact on inclusion removal2010In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 37, no 5, p. 347-352Article in journal (Refereed)
    Abstract [en]

    A two-dimensional non-steady state computational fluid dynamic model was employed to gain a basic understanding of the flow in the ingot during casting. The surface velocity was found to be affected by the inlet angle and was found to vary with the casting level. The information of surface velocity was related to the probability of the inclusion removal. Water model experiments were also conducted to help the understanding. The model calculation revealed the same trends as the results of water model experiments. Both computational fluid dynamic data and the physical modelling showed that the inlet angle of 5 degrees currently used in the industry was a good alternative regarding inclusion removal. The present work suggests strongly that the melting shop should try to obtain a liquid or semiliquid film at as early stage as possible in ingot casting.

  • 82.
    Ragnarsson, Lars
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Sichen, Du
    Erosion of runners in ingot casting2009In: AISTech - Iron and Steel Technology Conference Proceedings, 2009, p. 1077-1087Conference paper (Refereed)
    Abstract [en]

    Substantial erosion of the runner, especially the horizontal runner was noticed during casting. CFD simulation of the flow showed that the velocities were almost zero close to the centre stone and end stone. The low velocities well explained the minor erosion of the two types of stones. The CFD calculation also indicated that the velocities in the horizontal were not evenly distributed. Velocities as high as 3 m/s could be found at the entrance of the horizontal runner and close to the entrance of the ingot. This result was in good agreement with the experimental observation that the erosion close to the entrance of the horizontal runner was much more profound. The runner surface was found to react with the dissolved aluminium forming a layer of higher alumina content. The zigzag surface of the refractory could entrap inclusions and provide good condition for agglomeration. The detachment of the agglomerated inclusions along with the pieces of refractory could be an important source of the formation of macro inclusions during casting. The higher alumina contents in the inclusions found in the steel rod in comparison with that found in the ladle suggested possible reoxidation of the steel during casting.

  • 83.
    Ragnarsson, Lars
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Sichen, Du
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Inclusions Generated during Ingot Casting of Tool Steel2010In: STEEL RESEARCH INTERNATIONAL, ISSN 1611-3683, Vol. 81, no 1, p. 40-47Article in journal (Refereed)
    Abstract [en]

    An industrial trial study was carried out at Uddeholm Tooling AB, Sweden, to investigate the mechanisms of the formation of inclusions, especially macro inclusions during ingot casting. Strong evidence of reoxidation was observed. Two types of inclusions generated during casting were detected in the ingot. Inclusions of Type C1 originated from mould powder with reoxidation product Al2O3 as a part of it. Inclusions of this type were usually small. The number of Type C1 inclusions increased from the centre of the ingot toward the side wall of the mould. Type C2 inclusions were macro size. They could be the results of reoxidation and erosion of runner.

  • 84.
    Ragnarsson, Lars
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Song, Wei
    Ma, Yonglin
    Du, Sichen
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Oxygen penetration in the protection shroud in steel casting2010In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 81, no 11, p. 965-973Article in journal (Refereed)
    Abstract [en]

    Physical modelling of argon shroud used in ingot casting was carried out using a 2D 1:1 scaled model in order to determine the oxygen distribution around the steel stream. The oxygen concentrations were measured by an oxygen sensor. Complementary PIV measurements were also carried out for a gas inlet configuration using dual (horizontal and vertical) gas inlet. The main findings were: (1) The oxygen concentrations were considerably high in the ordinary operation conditions. The oxygen contents were the highest in the case of vertical gas injection (higher than 11% in all cases). (2) A minimized distance between the ladle and the collar on the top of the vertical runner would reduce the oxygen entrainment by convection and diffusion, in the case of horizontal gas injection and a dual gas inlet configuration. (3) A modest flow rate of argon gas should be used. Further increase of the gas flow would not improve the protection. (4) A dual gas inlet configuration would be more effective than a single inlet, especially in the case of larger distances between the ladle and the runner.

  • 85.
    Ragnarsson, Lars
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Song, Wei
    Ma, Yonglin
    Du, Sichen
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Physical and mathematical modelling of argon shroud for protection of steel stream during casting2010In: International Journal of Cast Metals Research, ISSN 1364-0461, E-ISSN 1743-1336, Vol. 23, no 6, p. 368-374Article in journal (Refereed)
  • 86.
    Ramström, Eva
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Mass transfer and slag-metal reaction in ladle refining: a CFD approach2009Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

     

    In order to optimise the ladle treatment mass transfer modelling of aluminium addition and homogenisation time was carried out. It was stressed that incorporating slag-metal reactions into the mass transfer modelling strongly would enhance the reliability and amount of information to be analyzed from the CFD calculations.

     

    In the present work, a thermodynamic model taking all the involved slag metal reactions into consideration was incorporated into a 2-D fluid flow model of an argon stirred ladle. Both thermodynamic constraints and mass balance were considered. The activities of the oxide components in the slag phase were described using the thermodynamic model by Björkvall and the liquid metal using the dilute solution model. Desulphurization was simulated using the sulphide capacity model developed by KTH group. A 2-D fluid flow model considering the slag, steel and argon phases was adopted.

     

    The model predictions were compared with industrial data and the agreement was found quite satisfactory. The promising model calculation would encourage new CFD simulation of 3-D along this direction.

     

  • 87.
    Ren, Shan
    et al.
    Univ Sci & Technol Beijing, Peoples R China.
    Zhang, Jianliang
    Univ Sci & Technol Beijing, Peoples R China.
    Wu, Liushun
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Liu, Weijian
    Univ Sci & Technol Beijing, Peoples R China.
    Bai, Yanan
    Univ Sci & Technol Beijing, Peoples R China.
    Xing, Xiangdong
    Univ Sci & Technol Beijing, Peoples R China.
    Su, Buxin
    Univ Sci & Technol Beijing, Peoples R China.
    Kong, Dewen
    Univ Sci & Technol Beijing, Peoples R China.
    Influence of B2O3 on Viscosity of High Ti-bearing Blast Furnace Slag2012In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 52, no 6, p. 984-991Article in journal (Refereed)
    Abstract [en]

    The influence of B2O3 on the viscosity of high Ti-bearing BF slag is studied under Ar atmosphere from 1 773 K (1 500 degrees C) to about 1 593 K (1 320 degrees C). The results show that the addition of B2O3 can decrease the viscosity of high Ti-bearing BF Slag containing UPC, consequently improve its fluidity. With the existence of 1.5% UPC, when the content of B2O3 increased from 0 to 4.1%, the volume fraction of perovskite decreased from 7.7% to 1.6% at 1 610 K. Meanwhile, the liquidus temperatures decreased from 1 619 K to 1 613 K. At a lower temperature, B2O3 was easy to form a eutectic and decreased the viscosity of molten slag. At a higher temperature, some tetrahedron [BO4](5-) changed into triangle [BO3](3-) which would disintegrate the chains/molecules of molten matrix and decreased its viscosity.

  • 88.
    Seetharaman, Seshadri
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Mukai, K.
    Sichen, Du
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Viscosities of slags - an overview2005In: Steel Research International, ISSN 1611-3683, Vol. 76, no 4, p. 267-278Article in journal (Refereed)
    Abstract [en]

    Viscosities of slags constitute an important physical property needed for an understanding of the mass transfer phenomena in metallurgical processes. Viscosity is also the key that leads to a better understanding of the structure of slags. It is well-known that the viscosities of silicate slags decrease with the addition of basic oxides due to the breaking of the silicate network. The measurements of slag viscosities often pose experimental challenges, especially with respect to the choice of materials. This paper takes up the experimental problems and the various techniques adopted. Dynamic viscosity measurement, as a powerful tool towards an understanding of the kinetics of some high temperature reactions is brought out. A number of semi-empirical models have been developed to estimate the slag viscosities in the case of multicomponent slags. A critical survey of these models is presented in this paper. Earlier models by Riboud et al., Urbain et al. and Mills et al. have been developed further into a new generation of models. Some of the current important models are, (1) Model by lida et al., ( 2) CSIRO model, (3) Pyroresearch Model, (4) Model by Tanaka et al., (5) Model approach by Reddy et al., and (6) KTH-model. The predictions and capabilities of the various models are compared. Estimations of viscosities from thermodynamic data and prediction of liquidus temperatures from viscosities are presented. The concept of surface viscosities with reference to slags and viscosities of two-phase mixtures are also taken up in the presentation.

  • 89.
    Seetharaman, Seshadri
    et al.
    KTH, Superseded Departments, Metallurgy.
    Sichen, Du
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Jönsson, Pär
    KTH, Superseded Departments, Applied Process Metallurgy.
    Jonsson, Lage
    KTH, Superseded Departments, Applied Process Metallurgy.
    Modelling of Metallurgical Reactions Towards Process Simulations2000Conference paper (Refereed)
  • 90.
    Sichen, Du
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Modeling Related to Secondary Steel Making2012In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 83, no 9, p. 825-841Article, review/survey (Refereed)
    Abstract [en]

    A big number of publications were collected to provide an overall picture of the modeling in secondary steelmaking. The referred papers could illustrate the general and typical approaches in modeling the process and sub-processes of steelmaking. The flow, mass transfer, and heat transfer in the reactors were briefly discussed. While modeling of slagmetal interface was summarized, the strong need for further understanding of the interface was emphasized. Modeling approaches of inclusion generation, growth, and separation were also discussed. The requirement of in-depth knowledge of these phenomena was addressed. The present review intends not only to provide a literature survey, but also to remind the researchers the importance of keeping balance between the experimental and modeling studies.

  • 91.
    Song, Minho
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    A Study on the Correlation between Ladle Glaze and Non-Metallic Inclusions in the Ladle Treatment2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In the present thesis, the correlation between ladle glaze and non-metallic inclusions in the ladle treatment was studied. A number of industrial trials with full scale ladle and laboratory works were performed to investigate the inclusions in the ladle treatment.

    BaO was used as tracer in the ladle slag to investigate the effect of slag on inclusion composition and the formation of non-metallic inclusions by ladle glaze. BaO was detected in the inclusions of all followed heats. This observation showed strong evidence for the generation of non-metallic inclusions by the ladle glaze. The increase of the fractions of BaO containing inclusions and their average content of BaO in the first heat with tracer suggested that the effect of slag on the composition of inclusions was a very slow process.

    The detachment of ladle glaze and the chemical transformations of oxide solution in the MgO matrix were investigated. The experimental results evidently showed that the ladle glaze could be the source of inclusions continually during the ladle treatment. Samples of liquid oxide solution to simulate the liquid oxide inclusions carried over from EAF were equilibrated with molten steel under controlled atmosphere. The results along with thermodynamic calculation suggested that the SiO2 content of inclusions from EAF could be considerably reduced by dissolved aluminium in the steel. This would explain the vanishing of inclusions containing high SiO2 content after deoxidation.

    Due to the lack of experimental data, the viscosities of slags in the Al2O3-CaO-MgO-SiO2 system were measured using the rotating cylinder method in the temperature range of 1720 to 1910 K. Eight different slag compositions related to the secondary steel making operations were selected. Viscosities in this system and its sub-systems were expressed as a function of temperature and composition based on the viscosity model developed earlier at KTH.

    The activities of oxide components in the Al2O3-CaO-MgO-SiO2 systems at 1873 K were measured by equilibrating liquid slag and metal. Either silicon or copper was used as the metal phase and the oxygen partial pressure was controlled with different mixing rates of Ar and CO gas flow in equilibrium with graphite. Iso-activity lines were drawn from the measured activity values in the isothermal section of the slag systems.

    Nine series of industrial trials were carried out using the same ladle in each series to examine the effect of ladle slag on the number of non-metallic inclusions in the next heat. It was found that the number of inclusions increased with SiO2 content of the ladle slag in the previous heat. No clear trends were found for the effects of viscosity and MgO activity of the previous slag on the number of inclusions. Theoretical analysis based on the experimental results suggested that the formation of 2CaO∙SiO2 followed but the dusting of the compound made the refractory more porous, which was reasonable for the number of non-metallic inclusions.

  • 92.
    Song, Minho
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Nzotta, M.
    Sichen, Du
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Study of the Formation of Non-metallic Inclusions by Ladle Glaze and the Effect of Slag on Inclusion Composition using Tracer Experiments2009In: Steel Resarch International, ISSN 1611-3683, Vol. 80, no 10, p. 753-760Article in journal (Refereed)
    Abstract [en]

    In the present work, BaO was used as tracer in the ladle slag to investigate the effect of slag on inclusion composition and the formation of non-metallic inclusions by ladle glaze. Experiments were carried out at Uddeholm Tooling AB, Hagfors, Sweden. In the first heat of each series, about 20 mass% BaO was added to the ladle slag. In the next heat(s) using the same ladle, no BaO was added. BaO was detected in the inclusions. This observation showed strong evidence for the generation of non-metallic inclusions by the ladle glaze. Even in the second and third heats, the fractions of BaO containing inclusions were still very high in all stages of the ladle treatment, indicating that ladle glaze was one of the major sources of inclusions. The sizes of the BaO containing inclusions were relatively big. The average size was 20 mu m, while the biggest was around 100 mu m. The increase of the fractions of BaO containing inclusions and their average content of BaO with the treatment stage suggested that the effect of slag on the composition of inclusions was a very slow process, due to the low solubility of Ba in the steel.

  • 93.
    Song, Minho
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Nzotta, Mselly
    Sichen, Du
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Effect of ladle slag of the previous heat on the number of non-metallic inclusions in ladle treatment of tool steel2011In: Ironmaking and Steelmaking, ISSN 0301-9233, Vol. 38, no 8, p. 584-589Article in journal (Other academic)
    Abstract [en]

    Nine series of industrial trials were carried out using the same ladle in each series to examine the effect of ladle slag on the number of non-metallic inclusions in the next heat. Steel and slag samples were taken after ladle vacuum treatment for chemical composition analysis. Samples of the final steel product were examined to determine the number of non-metallic inclusions. It was found that the number of inclusions increased with SiO(2) content of the ladle slag in the previous heat. No clear trends were found for the effects of viscosity and MgO activity of the previous slag on the number of inclusions. Theoretical analysis based on the experimental results suggested that the formation of 2CaO.SiO(2) followed, but the dusting of the compound made the refractory more porous, which was reasonable for the number of non-metallic inclusions.

  • 94.
    Song, Minho
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Ragnarsson, Lars
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Nzotta, M.
    Sichen, Du
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Mechanism study on the formation and chemical changes of calcium aluminate inclusions containing SiO2 in ladle treatment of tool steel2010In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812Article in journal (Refereed)
  • 95.
    Song, Minho
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Shu, Qifeng
    Sichen, Du
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Viscosities of the Quaternary Al2O3-CaO-MgO-SiO2 Slags2011In: Steel Research International, ISSN 1611-3683, Vol. 82, no 3, p. 260-268Article in journal (Refereed)
    Abstract [en]

    Viscosities of some quaternary slags in the Al2O3-CaO-MgO-SiO2 system were measured using the rotating cylinder method. Eight different slag compositions were selected. These slag compositions ranging in the high basicity region were directly related to the secondary steel making operations. The measurements were carried out in the temperature range of 1720 to 1910 K. Viscosities in this system and its sub-systems were expressed as a function of temperature and composition based on the viscosity model developed earlier at KTH. The iso-viscosity contours in the Al2O3-CaO-MgO-SiO2 system relevant to ladle slags were calculated at 1823K and 1873K for 5 mass% MgO and 10 mass% MgO sections. The predicted results showed good agreement with experimental values and the literature data.

  • 96.
    Song, Minho
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    White, Jesse
    Sichen, Du
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Activity measurements in Al2O3-CaO-SiO2(-5 mass% MgO) slag systems at 1873 KIn: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916Article in journal (Other academic)
  • 97.
    Thunman, Mikael
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Eckert, S.
    Hennig, O.
    Bjorkvall, J.
    Sichen, Du
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Study on the formation of open-eye and slag entrainment in gas stirred ladle2007In: Steel Research International, ISSN 1611-3683, 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.

  • 98.
    Thunman, Mikael
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Sichen, Du
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Origins of non-metallic inclusions and their chemical development during ladle treatment2008In: STEEL RESEARCH INTERNATIONAL, ISSN 1611-3683, Vol. 79, no 2, p. 124-132Article in journal (Refereed)
    Abstract [en]

    In the present work, steel, slag and refractory samples were taken from the ladle at OVAKO Steel in Hofors, Sweden. The steel samples were analysed in LOM, SEM and OES PDA. The chemical compositions of the inclusions were determined by EDS. According to the morphologies and compositions, the inclusions were classified into 5 different types, namely, (1) type-1, alumina inclusions, (2) type-2, calcium aluminate, (3) type-3, spinel+calcium aluminate, (4) type-4, calcium aluminate surrounded by a CaS shell, and (5) spinel+calcium aluminate surrounded by a CaS shell. Ladle glaze was found to be a major supplier of the inclusions, while the inclusions brought over from EAF could be another important source. The results of OES PDA showed that removal of inclusions took place mostly during the vacuum degassing period.

  • 99.
    Thunman, Mikael
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Sichen, Du
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Gran, Jonas
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Slag‐refractory reaction during ladle refining and teeming2009In: Steel Grips - Journal of Steel and Related Materials, ISSN 1611-4442, E-ISSN 1866-8453, Vol. 7, no 2, p. 129-135Article in journal (Other academic)
    Abstract [en]

    Refractory lining samples with slag layer were taken from used ladles at two steel plants, Ovako Steel and Uddeholm Tooling. The morphologies of the slag layers and the phases present were examined. The appearances and phases of the glaze layers were found to be somewhat different in the ladles from the two steel plants. The precipitated phases found in the refractory were 3CaO-Al2O3, MgO-Al2O3 and CaO in the case of Ovako Steel, and 3CaO-Al2O3 and 2CaO-SiO2 in the case of Uddeholm Tooling. To help the understanding, model calculations using commercial software Thermocalc were carried out. Although the model predictions differed somewhat from the experimental observation, the predicted major phases were in line with the EDS analysis on the refractory samples. Cold model study using both water and Ga-In-Sn alloy to simulate liquid steel were also performed. The results would be able to explain the thick slag line of the ladle and the serious erosion even far below the slag line. Both the slag line and the glaze layer below the slag line would be a potential source of non-metallic inclusions.

  • 100.
    Tomé Torquemada, Silvia
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Studies of some thermodynamic aspects related to the production of silicon and ferrosilicon2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis presents a fundamental study on some thermodynamic aspects regarding the silicon and ferrosilicon production. The purity requirements for silicon and ferrosilicon alloys are stringent. In order to achieve a successful and efficient refining of the silicon and ferrosilicon produced by carbothermic reduction, it is of great importance to know the phase relations in the system and to have reliable thermodynamic, kinetic and other physical data for the elements involved.

    The first part of the thesis includes a study of different phase relationships of the SrO-SiO2 and SiO2-SrO-Al2O3 systems. Experiments were performed to determine the phase relationships at temperatures between 1300 °C and 1625 °C in the binary system and at 1450 °C, 1500 °C and 1600 °C in the ternary system. The present result would be valuable when determining the compositions of the refining slags. A fully liquid slag would ensure favorable kinetic conditions in the refining process.

    The activities of some metallic elements in the silicon melt were determined in the second part of the thesis. The activities of Sr, Al, Zr and Ca in silicon were experimentally determined at temperatures that varied between 1450 °C and 1600 °C. These activities would provide useful information regarding the process temperature and the design of refining slags.

    The third part of the thesis covers the study of the activities in a ferrosilicon alloy. The activity coefficients for Al and Ca in FeSi50 were experimentally determined by equilibrating SiO2-Al2O3-CaO slags with ferrosilicon at 1550 °C. The activities obtained would be very useful information for the optimization of the refining process.

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