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  • 3051.
    Wendel, Erik
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Andersson, Axel
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Parameters affecting dephosphorization of stainless steel2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    A literary study has been made to find parameters affecting dephosphorization of stainless steel. Ways to lower phosphorus content without major loss of chromium in order to decrease the production costs of Sandvik AB’s stainless steel. The study was conducted with respect to oxidizing dephosphorization and parameters affecting dephosphorization are carbon and chromium content, temperature and slag properties. It was revealed that higher carbon content and basicity is beneficial to the dephosphorization process. However, the choice of temperature, chromium content and flux were dependant on which way dephosphorization was approached. A method of refining chromium in slag using an electric arc furnace (EAF) was also discovered. This made it possible to extract 97% of all chromium in slag. The conclusions are that in order for Sandvik to successfully remove phosphorus, scrap metal with higher carbon content should be used, together with a basic CaO slag with constituents of e g Li2O3 and CaF2. A deslagging step can be added to the argon oxygen decarburizer (AOD) process in order to remove the phosphorus bound to the slag, before decarburization.

  • 3052.
    Wennberg, Thord
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Transporting highly concentrated slurries with centrifugal pumps: the thickened minerals tailings example2010Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    New technologies are continuously considered for the handling and deposition of tailings. With thickened tailings only a fraction of water used conventionally reaches the disposal area, thus limiting sizes of water holding dam facilities and areas to be rehabilitated. Heat may also be recovered with direct water circulation from the thickening. Technical-economical feasibility considerations are here coupled to the Svappavaara iron ore operations by the Luossavaara-Kiirunavaara AB (LKAB) Company in northern Sweden. Local conditions here favour placement with an elevated thickener location close to the disposal area.The thickened tailings studied here have typically average particle sizes of 20 to 100 µm with maximum sizes of up to about 500 µm. The corresponding slurries cover an intermediate area between homogeneously and heterogeneously flowing mixtures. Various design features are often refereed to in rheological terms, i.e. homogeneous flow. Here, these terms are considered with some caution due to the notable amount of particles larger than about 40 µm.The objective is to form a background for feasibility considerations based on laboratory and pilot-scale experiments in pipelines and flumes together with viscometric measurements and depositional slope observations. Pipeline diameters covered the full-scale range, up to 0.15 m.It was found that a solids concentration by volume of about 48 % characterizes the pipeline pumping, here estimated to be on the conservative side with respect to thickened product quality requirement. The overall pipeline loop results were evaluated in terms of a representative pipe wall stress of about 200 Pa. Approximate values of the Bingham yield stress and plastic viscosity were estimated to 185 Pa and 0.03 Pas, respectively. Depositional slopes have been estimated to about 4 % for slurry properties that gives a conceptually even inclination with no segregation of particles and virtually no drainage of water.With an elevated thickener location close to the disposal area a new high pressure pumping system for about 10 MPa is avoided while the thickener underflow slurry is delivered with a centrifugal pump a short distance during the first years of operation. In order to meet the most effective long-term solution for pipeline distribution and placement, continued use of centrifugal pumps in series installations is considered as the discharge point advances during the 20-year life.The performance of a centrifugal pump is affected when handling highly concentrated slurries which shows up as reductions of the clear water head and efficiency curves. It was found that maximum reductions in head and efficiency were about 10 and 15 %, respectively, when operating at the design flow rate, QBEP, in the best efficiency region. As opposed to Newtonian fluids, a diverging tendency from the water head curve for decreasing flow rates has sometimes been reported below about 0.5QBEP for slurries that show a highly non-Newtonian behaviour. Various mechanisms related to the diverging tendency are discussed. The suction side pressure requirement is normally fulfilled with a large margin for a thickener underflow pump. It was observed in an installation how a standard pump operating at 0.5QBEP under a thickener showed no unstable head tendencies for a tailings slurry with an yield stress of nearly 200 Pa. However, pumps in series installation should be arranged with sufficient margins for an increased suction side pressure requirement.Keywords: Tailings slurry, highly concentrated, non-Newtonian behaviour, centrifugal pump performance, tailings depositional conditions.

  • 3053. Wessman, S.
    et al.
    Selleby, Malin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.
    Evaluation of Austenite Reformation in Duplex Stainless Steel Weld Metal using Computational Thermodynamics2014In: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 58, no 2, p. 217-224Article in journal (Refereed)
    Abstract [en]

    This paper provides a theoretical study of austenite reformation during cooling of duplex stainless weld metal using computational thermodynamics and kinetics. Model alloys of the superduplex 2509 weld metal and 2205 base material were used for the study and austenite reformation was calculated at equilibrium conditions and at cooling rates from 0.01 to 2,000 K/s. The calculations also provided the possibility to study the distribution of the alloying elements at ferrite and austenite phase boundaries. The importance of nitrogen for austenite reformation at rapid cooling was studied by comparing with simulations for a low-nitrogen alloy. The results were also compared with experimental and model results from the literature providing good correlation and the unique possibility to study the distribution of alloying elements between the growing austenite and the shrinking ferrite.

  • 3054. Westerberg, O.
    et al.
    Gartz, M.
    Stark, E.
    Gyllenram, Rutger
    KTH.
    Improving steel quality and decreasing production cost and carbon footprint through raw material management2012In: 70th World Foundry Congress 2012, WFC 2012, 2012, p. 515-518Conference paper (Refereed)
    Abstract [en]

    A thorough raw material selection and blending is essential for achieving a high quality melt at a minimum cost. Residual material from previous production constitute a large part of the material input and a practice where residuals from one steel type is used for producing the same steel type often lead to big stocks of internal scrap. The value of internal scrap is high due to its known alloy content and can, if used optimally, reduce overall production costs Global Warming has put the emissions of CO2 as a main focus point in product ecology. The choice of alloy source and electricity (if possible) is vital for reducing the carbon footprint for stainless steel. This paper discusses possible ways to decrease the capital bound in stock for a stainless steel foundry. Ways to improve quality control of scrap are outlined in order to be able to buy cheaper scrap and reduce the fraction of alloying elements coming from primary alloys.

  • 3055.
    Westerholm, Mikael
    Luleå tekniska universitet.
    Rheology of the mortar phase of concrete with crushed aggregate2006Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    In Sweden, concrete has traditionally been manufactured with glaciofluvial deposits as fine aggregate. In 2004 the production of this aggregate was approximately 21 million tons. Due to environmental reasons and local shortage of this natural resource there exists a goal to reduce the production to 12 million tons in year 2010. In order to compensate for the reduced production an alternative material which can be used as replacement has to be found. Aggregate from crushed bedrock is an alternative which is locally available and found in sufficient amounts. However, the characteristics of this type of aggregate generally differ from the ones of glaciofluvial fine aggregate and are known to generate concrete with higher water demand and lower workability. In order to facilitate a changeover to crushed fine aggregate, it is important to achieve a better understanding of the influence of crushed fine aggregate characteristics on the workability of concrete. The properties of the mortar phase of concrete influence the workability of concrete. The study of the mortar phase of concrete with crushed fine aggregate can therefore be valuable in predicting the influence of the fine aggregate characteristics on concrete workability. The aim of this licentiate thesis was to clarify the influence of the characteristics of crushed fine aggregate (0-2 mm) on the rheological properties of mortars. This included studies of the effect of aggregate shape, quality and amount of fines, washed fine aggregate and superplasticizer addition. The experimental work was divided into three different parts, i.e., zeta potential study, micromortar and mortar rheology. In the zeta potential part, the interaction between different fines and a common type of superplasticizer was studied. The results indicate that the superplasticizer is preferentially adsorbed on biotite rich fines. In the micromortar part, the fines fraction of different fine aggregates was studied separately in order to evaluate the influence of their particle shape, specific surface area and mineral composition. The results from this part showed that the quality of the fines has a large influence on the rheological properties of micromortars. Furthermore, the yield stress and plastic viscosity were shown to increase with the specific surface area of the fines. The results also suggest that the shape of the fines mainly influences the plastic viscosity, i.e., the viscosity of the micromortars with elongated fines was higher than the corresponding micromortars with cubic shaped fines. In the mortar part, different fine aggregates were studied both with their original and with standardized grading curves. The evaluation was done both with and without addition of superplasticizer and at different paste volumes. The effect of washed fine aggregate was also evaluated. The results show that the shape of the fine aggregate particles mainly influences the plastic viscosity of the mortar. The fines content was shown to increase the yield stress and, thus, the water demand of the mortar. Furthermore, the results showed that washing and the use of superplasticizer are two potential ways to reduce the water demand of mortars with fine aggregates from crushed rock. Finally, the results from this work suggests that the higher yield stress and plastic viscosity often shown by mortars containing crushed fine aggregate can be related to two main characteristics of the aggregate. The high yield stress is believed to mainly originate from the high amounts of fines often seen in crushed fine aggregates, while the higher plastic viscosity can be related to the more elongated particle shape of the fine aggregate.

  • 3056.
    Westerholm, Mikael
    et al.
    Swedish Cement and Concrete Research Institute.
    Lagerblad, B.
    Swedish Cement and Concrete Research Institute.
    Silfwerbrand, J.
    Swedish Cement and Concrete Research Institute.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Influence of fine aggregate characteristics on the rheological properties of mortars2008In: Cement & Concrete Composites, ISSN 0958-9465, E-ISSN 1873-393X, Vol. 30, no 4, p. 274-282Article in journal (Refereed)
    Abstract [en]

    This paper presents results from a laboratory study on the influence of crushed fine aggregate on the rheological properties, i.e., yield stress and plastic viscosity, of the mortar phase of concrete. The effect of grading, particle shape, etc. of the fine aggregates has been evaluated with the use of a viscometer suited for coarse particle suspensions. The evaluation has been done at different dosages of superplasticizer and paste volumes by the use of an inert artificial "cement paste". The results show that the properties and amount of fine aggregate have a strong influence on the water demand and workability of the mortar, i.e., the rheology. The large amounts of fines often found in crushed fine aggregate primarily increases the yield stress of the mortar. The amount of fines also contributes to the plastic viscosity by increased interparticle friction. However, the results clearly show that the particle shape of the fine aggregate strongly contributes to the plastic viscosity. The influence of the properties of the fine aggregate is largely dependent on the paste volume of the mortar. Thus, by increasing the paste volume, negative effects of poorly graded and shaped aggregates can be eliminated or significantly reduced.

  • 3057.
    Westerholm, Mikael
    et al.
    Swedish Cement and Concrete Research Institute.
    Lagerblad, Björn
    Swedish Cement and Concrete Research Institute.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Rheological properties of micromortars containing fines from manufactured aggregates2007In: Materials and Structures, ISSN 1359-5997, E-ISSN 1871-6873, Vol. 40, no 6, p. 615-625Article in journal (Refereed)
    Abstract [en]

    This paper concerns the influence of fines from manufactured aggregates on the rheological properties of the micromortar phase of concrete. Fines from nine different aggregates were included in the experimental work. The zeta potential of five of them was measured at different additions of superplasticizer in order to study the interaction between the surface of the fines and the superplasticizer. The rheological properties of the micromortars were studied at different volume concentrations of fines and at different concentrations in the paste phase, i.e., w/c ratios. Furthermore, the micromortars were studied at different dosages of a superplasticizer. The results show that the fines have different surface properties, i.e., zeta potential, and indicate that the superplasticizer only is adsorbed on some of them. The results from the rheological characterisation of the micromortars indicate that the higher water demand of concrete with manufactured aggregates partly can be traced to the properties of the micromortar phase of the concrete.

  • 3058.
    Westerholm, Mikael
    et al.
    Swedish Cement and Concrete Research Institute.
    Lagerblad, Björn
    Swedish Cement and Concrete Research Institute.
    Forssberg, Eric
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Washing of aggregates: Influence on aggregate properties and mortar rheology2006In: Nordic Concrete Research, Oslo: The Nordic Concrete Federation , 2006, p. 35-46Chapter in book (Other academic)
  • 3059.
    Westin, Elin M.
    Outokumpu Stainless, Avesta Research Centre.
    HENRY GRANJON PRIZE COMPETITION 2009 Winner Category B: "Materials Behaviour and Weldability" PITTING CORROSION RESISTANCE OF GTA WELDED LEAN DUPLEX STAINLESS STEEL2010In: WELD WORLD, ISSN 0043-2288, Vol. 54, no 11-12, p. R308-R321Article in journal (Refereed)
    Abstract [en]

    The use of lean duplex stainless steel increases steadily worldwide and the fluctuations in nickel price in recent years have contributed to further growth. The weldability of these grades is different from that of the substituted austenitic grades and this paper focuses on the effect of weld metal microstructure and weld oxide on the pitting corrosion resistance. The influence of chromium nitride precipitates on the corrosion performance is illustrated and it is shown that if the weld metal has sufficient nitrogen content and hence adequate austenite formation, the weld oxide controls the location of pitting. Diffusion and oxidation are normally the discussed processes affecting the composition and distribution of the heat tint, but here a new approach to weld oxide formation is proposed. It is shown that manganese is evaporated from the weld metal and contributes to forming thicker weld oxide by subsequent deposition. Addition of nitrogen to the shielding gas further enhanced the manganese evaporation and also formed a significant fraction of oxynitrides in the weld oxide.

  • 3060.
    Westin, Elin M.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Microstructure and properties of welds in the lean duplex stainless steel LDX 21012010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Duplex stainless steels can be very attractive alternatives to austenitic grades due to their almost double strength at equal pitting corrosion resistance. When welding, the duplex alloys normally require addition of filler metal, while the commodity austenitic grades can often be welded autogenously. Over-alloyed consumables are used to counteract segregation of important alloying elements and to balance the two phases, ferrite and austenite, in the duplex weld metal. This work focuses on the weldability of the recently-developed lean duplex stainless steel LDX 2101® (EN 1.4162, UNS S32101). The pitting corrosion resistance of this grade is better than that of austenitic AISI 304 (EN 1.4307) and can reach the level of AISI 316L (EN 1.4404). The austenite formation is rapid in LDX 2101 compared to older duplex grades. Pitting resistance tests performed show that 1-2.5 mm thick laser and gas tungsten arc (GTA) welded LDX 2101 can have good corrosion properties even when welding autogenously. Additions of filler metal, nitrogen in the shielding gas, nitrogen-based backing gas and use of laser hybrid welding methods, however, increase the austenite formation. The pitting resistance may also be increased by suppressing formation of chromium nitrides in the weld metal and heat affected zone (HAZ). After thorough post-weld cleaning (pickling), pitting primarily occurred 1-3 mm from the fusion line, in the parent metal rather than in the HAZ. Neither the chromium nitride precipitates found in the HAZ, nor the element depletion along the fusion line that was revealed by electron probe microanalysis (EPMA) were found to locally decrease the pitting resistance. The preferential pitting location is suggested to be controlled by the residual weld oxide composition that varies over the surface. The composition and thickness of weld oxide formed on LDX 2101 and 2304 (EN 1.4362, UNS S32304) were determined using X-ray photoelectron spectroscopy (XPS). The heat tint on these lean duplex grades proved to contain significantly more manganese than what has been reported for standard austenitic stainless steels in the AISI 300 series. A new approach to heat tint formation is presented; whereby evaporation of material from the weld metal and subsequent deposition on the already-formed weld oxide are suggested to contribute to weld oxide formation. This is consistent with manganese loss from the weld metal, and nitrogen additions to the GTA shielding gas enhance the evaporation. The segregation of all elements apart from nitrogen is low in autogenously welded LDX 2101. This means that filler wire additions may not be required as for other duplex grades assuming that there is no large nitrogen loss that could cause excessive ferrite contents. As the nitrogen appears to be controlling the austenite formation, it becomes essential to avoid losing nitrogen during welding by choosing nitrogen-containing shielding and backing gas.

  • 3061.
    Westin, Elin M.
    et al.
    Outokumpu Stainless.
    Brolund, Bengt
    SSAB Tunnplat.
    Hertzman, Staffan
    Outokumpu Stainless Res Fdn.
    Weldability aspects of a newly developed duplex stainless steel LDX 21012008In: STEEL RES INT, ISSN 1611-3683, Vol. 79, no 6, p. 473-481Article in journal (Refereed)
    Abstract [en]

    Duplex grades have, due to balanced chemical compositions of both filler and base metals, a weldability that allows for successful welding using a majority of the technically relevant techniques of today. In order to fulfil the performance requirements several aspects must be considered. In the heat affected zone (HAZ) the austenite reformation must be reasonably high and in the weld metal the microstructure must be stable so that e.g. high productivity welding and multi-pass welding are possible, without precipitation of detrimental phases in previous passes. This paper addresses the effect of alloying elements and thermal cycles on phase balance in the high temperature HAZ (HTHAZ) of the newly developed lean duplex grade LDX 2101 (EN 1.4162, UNS S32101). Bead-on-plate welds and simulated weld structures have been produced and investigated using metallography, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results are analysed using the thermodynamic database Thermo-Calc and a model for phase transformation based on a paraequilibrium assumption for ferrite-austenite transformation. In the temperature region outside the paraequilibrium domain, growth controlled by diffusion of substitutional elements was considered. The analysis follows a model by Cahn regarding grain boundary nucleated growth and the Hillert-Engberg model on kinetics of spherical and planar growth.

  • 3062.
    Westin, Elin M.
    et al.
    Outokumpu Stainless, Avesta Research Centre.
    Hertzman, Staffan
    Outokumpu Stainless Research Foundation.
    Element distribution in lean duplex stainless steel weldsIn: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940Article in journal (Other academic)
  • 3063. Westraadt, J. E.
    et al.
    Olivier, E. J.
    Neethling, J. H.
    Hedström, Peter
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Odqvist, Joakim
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Xu, X.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Steuwer, A.
    A high-resolution analytical scanning transmission electron microscopy study of the early stages of spinodal decomposition in binary Fe-Cr2015In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 109, p. 216-221Article in journal (Refereed)
    Abstract [en]

    Spinodal decomposition (SD) is an important phenomenon in materials science and engineering. For example, it is considered to be responsible for the 475 degrees C embrittlement of stainless steels comprising the bcc (ferrite) or bct (martensite) phases. Structural characterization of the evolving minute nano-scale concentration fluctuations during SD in the Fe-Cr system is, however, a notable challenge, and has mainly been considered accessible via atom probe tomography (APT) and small-angle neutron scattering. The standard tool for nanostructure characterization, viz, transmission electron microscopy (TEM), has only been successfully applied to late stages of SD when embrit-dement is already severe. However, we here demonstrate that the structural evolution in the early stages of SD in binary Fe-Cr, and alloys based on the binary, are accessible via analytical scanning TEM. An Fe-36 wt% Cr alloy aged at 500 degrees C for 1, 10 and 100 h is investigated using an aberration-corrected microscope and it is found that highly coherent and interconnected Cr-rich regions develop. The wavelength of decomposition is rather insensitive to the sample thickness and it is quantified to 2, 3 and 6 nm after ageing for 1, 10 and 100 h, which is in reasonable agreement with prior APT analysis. The concentration amplitude is more sensitive to the sample thickness and acquisition parameters but the TEM analysis is in good agreement with APT analysis for the longest ageing time. These findings open up for combinatorial TEM studies where both local crystallography and chemistry is required.

  • 3064. White, Jesse F.
    et al.
    Allertz, Carl
    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.
    Boron partitioning between SiO2-CaO-MgO slags and liquid silicon at controlled nitrogen potential2013In: International Journal of Materials Research - Zeitschrift für Metallkunde, ISSN 1862-5282, E-ISSN 2195-8556, Vol. 104, no 7, p. 650-656Article in journal (Refereed)
    Abstract [en]

    During refining of silicon using slag treatment, boron dissolved in the silicon is extracted to a liquid oxide (slag) phase. In this investigation the partitioning of boron between SiO2-CaO-MgO slags and liquid silicon was examined at 1873 K over a range of slag compositions and CO-N-2 gas mixtures. It was found that the distribution of boron is strongly dependent on the nitrogen partial pressure as well as the slag composition. The greatest partition ratios were achieved at 0.6 atm CO/0.4 atm N-2 with low silica content in the slag. The concentration of MgO in the slag seems to have little or no impact on the boron partition ratio.

  • 3065. White, Jesse F.
    et al.
    Allertz, Carl
    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.
    The thermodynamics of boron extraction from liquid silicon using SiO2-CaO-MgO stag treatment2013In: International Journal of Materials Research - Zeitschrift für Metallkunde, ISSN 1862-5282, E-ISSN 2195-8556, Vol. 104, no 3, p. 229-234Article in journal (Refereed)
    Abstract [en]

    In the refining of solar-grade silicon using slag treatment, boron dissolved in the silicon is oxidized and rejected to a liquid oxide (slag) phase. In this study the partitioning of boron between liquid silicon and SiO2-CaO-MgO slags was examined at 1 873 K over a range of slag compositions and oxygen partial pressures. It was found that the distribution of boron is indeed dependent on both the slag composition and the oxygen partial pressure. The concentration of MgO seems to have little impact on the partition ratio.

  • 3066. White, Jesse F.
    et al.
    Du, Sichen
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Mass Transfer in Slag Refining of Silicon with Mechanical Stirring: Transient Kinetics of Ca and B Transfer2015In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 46, no 1, p. 135-144Article in journal (Refereed)
    Abstract [en]

    Mechanical stirring was demonstrated to be a potent means to increase the mass transfer rates of B and Ca in slag refining of silicon, and optimal stirring conditions were attained with only a modest kinetic energy input into the melt. Experiments were undertaken to measure mass transfer rates between liquid silicon and CaO-SiO2 slags at 1823 K (1550 degrees C) with varying stirring speed and slag composition. A remarkable feature of this system is the extreme fluctuation in interfacial area-these changes occur very rapidly and are difficult to capture. As little as 50 rpm stirring speed promotes, significant transient increases in interfacial area. At stirring speeds above 100 rpm, the rates of mass transfer do not increase significantly, so it is evident that above this threshold mass transfer in the bulk phases and interfacial area generation are already maximized. With a sufficiently high content of CaO in the slag, interfacial phenomena induced by the mass flux of calcium facilitate emulsification, and this is explained from a thermodynamic standpoint. It is likely that the calcium transfer enhances boron transfer by increasing the available interfacial area.

  • 3067.
    White, Jesse Franklin
    et al.
    Elkem AS, Technology, Kristiansand, Norway .
    Du, Sichen
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Mass Transfer in Slag Refining of Silicon with Mechanical Stirring: Transient Interfacial Phenomena2014In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 45, no 1, p. 96-105Article in journal (Refereed)
    Abstract [en]

    Experiments have been carried out to study the rates of mass transfer between liquid silicon and CaO-SiO2 slag with impeller stirring at 1823 K (1550 A degrees C). The occurrence of transient interfacial phenomena related to the mass transfer of calcium has been observed; the evidence suggests that the reduction of calcium oxide at the interface leads to a rapid, temporary drop in the apparent interfacial tension. At low apparent interfacial tension, mechanical agitation facilitates the dispersion of metal into the slag phase, which dramatically increases the interfacial area; here, it has been estimated to increase by at least one order of magnitude. As the reaction rate slows down, the apparent interfacial tension increases and the metal recoalesces. The incidental transfer of calcium very likely promotes the transfer of boron by increasing the interfacial area. Mechanical mixing appears to be an extremely effective means to increase the reaction rate of boron extraction and could feasibly be implemented in the industrial slag refining of silicon to improve reaction rates.

  • 3068. Widlund, Daniel
    et al.
    Sarma, Darbha Subraanranya
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Studies on decarburisation and desiliconisation of levitated Fe-C-Si alloy droplets2006In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 46, no 8, p. 1149-1157Article in journal (Refereed)
    Abstract [en]

    The rate of decarburization and desiliconisation has been studied in several Fe-C-Si alloys containing 4% C and 0.37-0.71% Si using electromagnetically levitated droplets at 1400 and 1660 degrees C in oxygen and helium atmospheres containing 10 and 20% oxygen. It has been found that the decarburization proceeds till a carbon content of about 0.5% is reached at a constant rate (the rates are 0.11 and 0.17%/s respectively for 10 and 20% oxygen) that is independent of temperature and silicon content. Beyond this carbon level, not only the decarburization rate has decreased but also the silicon content has started falling down. Optical microscopy studies showed typical white iron structures in the initial stages of decarburization (due to the small size of the droplet as well as rapid cooling) while low carbon acicular ferrite structure when % O-2 was 20 % and medium carbon structure when % 02 was 10 %. This corresponded to the higher carbon content (similar to 0.38%) of the latter. SEM studies did not reveal any oxide layer on the surface but EDS showed that the oxygen concentration was higher (0.02 to 0.24%) that extended to about 0.5 to 1 mu m depth suggesting that oxygen gradients do occur even in the initial stages of decarburization due to the high level of turbulence within the droplet due to the electromagnetic effects in levitation. Calculations based on Thermocalc gave logarithmic decrease for decarburisation while it was found to be linear experimentally. This could be due to operating parameters other than diffusion (like convection) taking place or nonequilibrium conditions (created due to turbulence) and shorter times used for levitation.

  • 3069.
    Wikedzi, Alphonce
    et al.
    Luleå University of Technology, Sweden.
    Awe, Samuel A.
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing. Luleå University of Technology, Sweden.
    Selective Extraction of Antimony and Arsenic from Decopperization Slime Using Experimental Design2017In: Journal of sustainable metallurgy, ISSN 2199-3823, Vol. 3, no 2, p. 362-374Article in journal (Refereed)
    Abstract [en]

    The aim of the present study is to selectively extract antimony and arsenic from decopperization slime through alkaline sulfide hydrometallurgy with a view to recycle the obtained solid residue within the copper smelter, and also regenerate the sulfide lixiviant during the process. Rechtschaffner experimental design was used to evaluate the joint influence of several experimental parameters such as leaching temperature, Na2S concentration, solid concentration, and reaction time on the extraction of antimony and arsenic from the material. The most active parameters influencing the extraction of the metals are solid concentration and reaction period. In addition, the results show that solid concentration interacted strongly with the leaching time and slightly with reaction temperature, which is an indication that solid concentration is the predominant influencing factor in removing antimony and arsenic from the material. It is also indicated from the results that about 95% Sb and 89% As were extracted when 50 g/L of the decopperization slime was dissolved in alkaline sulfide lixiviant containing 200 g/ L Na2S ? 20 g/L NaOH at 60 C for 24 h. Moreover, analysis of the leach residue reveals that copper sulfide and lead sulfide remain as the main constituents of the residue. The bismuth-containing mineral phase was not observed in the residue because of its low concentration, and also the Sb/As-bearing mineral phases were not detected due to the selectivity of the leaching reagent to the metals. Based on the experimental results from this investigation, a process flowsheet for the alkaline sulfide treatment of a decopperization slime was proposed with a view to eliminating its antimony and arsenic contents in a sustainable manner.

  • 3070.
    Wikedzi, Alphonce
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering. Department of Materials and Manufacturing, School of Engineering, Jönköping University, Jönköping, Sweden.
    Awe, Samuel Ayowole
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Selective Extraction of Antimony and Arsenic from Decopperization Slime Using Experimental Design2017In: Journal of Sustainable Metallurgy, ISSN 2199-3823, Vol. 3, no 2, p. 362-374Article in journal (Refereed)
    Abstract [en]

    The aim of the present study is to selectively extract antimony and arsenic from decopperization slime through alkaline sulfide hydrometallurgy with a view to recycle the obtained solid residue within the copper smelter, and also regenerate the sulfide lixiviant during the process. Rechtschaffner experimental design was used to evaluate the joint influence of several experimental parameters such as leaching temperature, Na2S concentration, solid concentration, and reaction time on the extraction of antimony and arsenic from the material. The most active parameters influencing the extraction of the metals are solid concentration and reaction period. In addition, the results show that solid concentration interacted strongly with the leaching time and slightly with reaction temperature, which is an indication that solid concentration is the predominant influencing factor in removing antimony and arsenic from the material. It is also indicated from the results that about 95% Sb and 89% As were extracted when 50 g/L of the decopperization slime was dissolved in alkaline sulfide lixiviant containing 200 g/L Na2S + 20 g/L NaOH at 60 °C for 24 h. Moreover, analysis of the leach residue reveals that copper sulfide and lead sulfide remain as the main constituents of the residue. The bismuth-containing mineral phase was not observed in the residue because of its low concentration, and also the Sb/As-bearing mineral phases were not detected due to the selectivity of the leaching reagent to the metals. Based on the experimental results from this investigation, a process flowsheet for the alkaline sulfide treatment of a decopperization slime was proposed with a view to eliminating its antimony and arsenic contents in a sustainable manner.

  • 3071.
    Wikedzi, Alphonce
    et al.
    University of Dar es Salaam, Tanzania.
    Sandström, Åke
    Luleå University of Technology, Sweden.
    Awe, Samuel A.
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing. Luleå University of Technology, Sweden.
    Recovery of antimony compounds from alkaline sulphide leachates2016In: International Journal of Mineral Processing, ISSN 0301-7516, E-ISSN 1879-3525, Vol. 152, p. 26-35Article in journal (Refereed)
    Abstract [en]

    In copper metallurgy, antimony impurities usually form alloys and compounds with the transition metals to make up the basic building blocks of a speiss phase. This speiss phase is generally rich in copper and precious metals, which are desirable to recycle and recover at the smelter. The presence of this impurity unfortunately creates a build-up of this metal in the copper circuit, leading to problems during copper refining processes. Therefore, a removal or reduction of the antimony impurity to an acceptable level is a necessary step before the speiss can be recycled at the smelter for the recovery of its valuable metals. A lead silicate slag that was obtained after smelting a copper speiss admixed with silica, soda and lead oxide, was leached in alkaline sulphide solution to selectively dissolve its antimony content. Furthermore, the pregnant sulphide leachate was purified by precipitation and crystallization techniques to recover antimony as sodium thioantimonate and sodium hydroxyl antimonate using synthetic Na2S-NaOH-Sb2S3 solutions. The leaching results indicate that the highest amount of antimony and arsenic extracted from the material after 24 h at 100 °C and reagent concentration of 30 g/L NaOH + 30 g/L S2− was 83% and 90%, respectively. In the precipitation process, the addition of hydrogen peroxide to the alkaline sulphide leachate prompts the precipitation of antimony as NaSb(OH)6. The result also implies that b100% of stoichiometric hydrogen peroxide is required to completely oxidize the total amounts of both Sb3+ and S2− in the solution and to quantitatively precipitate N90% of the antimony in solution. The influence of catalytic agents and temperature on the process was not clearly reflected in this investigation due to the exothermic reaction with hydrogen peroxide. Moreover, the addition of elemental sulphur to the sulphide leachate also in- fluences the precipitation of antimony as sodium thioantimonate.

  • 3072.
    Wikedzi, Alphonce
    et al.
    Department of Chemical and Mining Engineering, University of Dar es Salaam.
    Sandström, Åke
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Awe, Samuel Ayowole
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Minerals and Metallurgical Engineering.
    Recovery of antimony compounds from alkaline sulphide leachates2016In: International Journal of Mineral Processing, ISSN 0301-7516, E-ISSN 1879-3525, Vol. 152, p. 26-35Article in journal (Refereed)
    Abstract [en]

    In copper metallurgy, antimony impurity usually forms alloys and compounds with the transition metals to make up the basic building blocks of a speiss phase. This speiss phase is generally rich in copper and precious metals which are desirable to recycle and recover at the smelter. The presence of this impurity unfortunately creates a build-up of this metal in the copper circuit, leading to problems during copper refining processes. Therefore, a removal or reduction of the antimony impurity to an acceptable level is a necessary step before the speiss can be recycled at the smelter for the recovery of its valuable metals. A lead oxide slag, which was obtained after speiss had gone through a special pyrometallurgical process, was leached in alkaline sulphide solution to selectively dissolve its antimony content. Furthermore, the pregnant sulphide leachate was purified by precipitation and crystallization techniques to recover antimony as sodium thioantimonate and sodium hydroxyl antimonate using synthetic Na2S-NaOH-Sb2S3 solution. The leaching results indicate that the highest amount of antimony and arsenic extracted from the material after 24 h at 100oC and reagent concentration of 30 g/L NaOH + 30 g/L S2- was 83% and 90%, respectively. In the precipitation process, addition of hydrogen peroxide to the alkaline sulphide leachate prompts the precipitation of antimony as NaSb(OH)6. The result also implies that less than 100% of stoichiometric hydrogen peroxide is required to completely oxidize the total amounts of both Sb3+ and S2- in the solution to quantitatively precipitate more than 90% of the antimony in solution. The influence of catalytic agents and temperature on the process was not clearly reflected in this investigation due to the exothermic reaction with hydrogen peroxide. Moreover, addition of elemental sulphur to the sulphide leachate also influences the precipitation of antimony as sodium thioantimonate.

  • 3073.
    Wiklund, Daniel
    Halmstad University, School of Business and Engineering (SET), Mechanical Engineering and Industrial Design (MTEK).
    Tribology of stamping: the influence of designed steel sheet surface topography on friction2006Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Tribology is the science of friction, wear, and lubrication; the interaction of surfaces in relative motion. The tribological conditions in sheet metal forming influences the flow of material in forming operations, the strain distributions of sheet material, extent of wear, and thereby the quality of products. The purpose of the thesis is to increase the knowledge of why and how sheet surface topography influence the frictional response in stamping, to characterise the geometrical properties, and make results applicable for industry. The frictional response of different surface topographies have been measured in a Bending Under Tension test under mixed lubricated conditions. The studied materials have been stainless steel sheets and uncoated and coated carbon steel sheets. The results did show the influence of roughness, skewness, and anisotropy of surface topography. The findings could be explained by the theory of pad bearings. A new functional 3D parameter (Sq>0) was developed for pressing performance that is sensitive to the effects of roughness and skewness. The texture-aspect ratio parameter (Str) was found to be correlated to the anisotropical behaviour of the frictional response. The results are very tangible and mean increased control of stamping operations. An initial step was taken to introduce more advanced tribological models in FE simulation of sheet metal forming operations. The aim is to decrease the trial-and-error time in the design process of dies and tools. A friction model considering surface topography (Sq>0), sliding velocity, lubricant viscosity, and apparent pressure, was successfully implemented. Simulations of a part were evaluated with real stamping tryouts. The results did show the potential of improving the precision in forming simulations with more advanced tribological models. Finally, theory and characterisation methods of active micro-oil pockets in the contact zone of tool and sheet were investigated. The real contact area was shown to be the critical feature to determine. Therefore, two topographical methods and one microscope-imaging processing technique were studied, but no method was found to be viable. However, the experimental results did not confirm the importance of microoil pockets in mixed lubricated regime.

  • 3074.
    Wiklund, Simon
    et al.
    KTH, School of Industrial Engineering and Management (ITM).
    Armstrong, Christopther
    KTH, School of Industrial Engineering and Management (ITM).
    A Study of Waterjets: Characterization of waterjet in the water atomization process2018Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This study was regarding the waterjets in the water atomization process. This is because the understanding of the waterjets is not complete and with a greater understanding the production of metal powder could be improved.

    The waterjets were going to be categorized according to their wave function, size and distribution of the droplets and the three regimes that Höganäs had divided up the jets into was also analyzed. The three regimes depend on the jets characteristics and the regimes are the transparent, milky and the droplet jet.

    The purpose was to get a better understanding of the correlation between velocity, temperature, waves, size and distribution of the droplets in a 50 cm long waterjet.

    The method to enhance the understanding of this project was to first do theoretical solution with the help of fluid dynamics. Weber, Reynolds and Ohnesorge number were calculated and evaluated to get a better understanding of the waterjet. Secondly, experiments were conducted where a waterjet with different nozzles and temperatures was filmed with a highspeed camera and the videos were analyzed with the help of a software package called ImageJ.

    The results show the correlation between increasing temperature and decreasing droplet size and a less cohesive waterjet core. The conclusion from the study was that with the help of temperature one can help control the droplet size.

  • 3075.
    Wikman, Stefan
    et al.
    Fusion for Energy, Barcelona, Spain.
    Cui, Daqing
    Studsvik Nuclear AB, Sweden.
    Shen, James
    Stockholms universitet, Sweden.
    Bin, Qian
    Stockholms universitet, Sweden.
    Rännar, Lars-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    ON 3D ADDITIVE MANUFACTURING ITER COMPONENTS2013Conference paper (Refereed)
  • 3076.
    Wikman, Stefan
    et al.
    Fusion for Energy.
    Shen, Zhijian
    Stockholm University.
    Rännar, Lars-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Obitz, Charlotta
    Studsvik.
    Öijerholm, Johan
    Studsvik.
    Assessment of additive manufacturing of 316L(N)-IG for In-Vessel components and performance of CuCrZr at coolant water interfaces2015Conference paper (Refereed)
  • 3077. Wikström, Jan-Olov
    et al.
    Grip, Carl-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Larsson, Mikael
    Ångström, Sten
    Swerea MEFOS AB.
    Ways to reduce CO2-emissions at SSAB Luleå works2004In: Proceedings: 2nd International Conference on New Developments in Metallurgical Process Technology, Milano: Associazione Italiana di Metallurgia , 2004Conference paper (Other academic)
  • 3078.
    Wikström, Jenny
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    A Mathematical and Experimental Study of Inclusion Behaviour at a Steel-Slag Interface2007Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The aim of this thesis work is to increase the knowledge of inclusion behavior at the steel-slag interface by mathematical modeling and in-situ Confocal Scanning Laser Microscope experiments. Mathematical models based on the equation of motion predicting liquid and solid inclusion behavior was first investigated. Four main forces, the buoyancy force, the added mass force, the rebound force and the drag force, act on the inclusion as it crosses the interface. There are three types of behavior an inclusion at the steel-slag interface can adopt. These are a) pass, which means that the inclusion is separated to the slag, b) remain, where the inclusion stays at the interface without being fully transferred to the slag or c) oscillate, and the inclusion rises and descends at the interface until the motion is dampened out by the interfacial forces. The studies showed the importance of accurate experimental physical property data. Application of the models to industrial conditions illustrated that useful plots could be made showing the industry how to optimize their interfacial properties in the ladle and tundish to obtain maximum inclusion separation.

    In-situ Confocal Scanning Laser Microscope (CSLM) experiments were carried out in order to study agglomeration of liquid and semi liquid inclusions at the steel-gas and steel-slag interfaces and in the slag. Liquid-liquid inclusion agglomeration at steel-gas and steel-slag interfaces was seen to not occur without using force. However, when already transferred to the slag the inclusions agglomerated freely due to a higher free energy force. Comparison of experimental and theoretical agglomeration force showed good agreement between experiments and theory.

    The main conclusion of this work is that inclusion separation is a complex field of study and there exist no model that takes everything into account. Here the tendency for inclusion transfer and how to manipulate the physical properties for inclusion separation together with agglomeration experiments have been studied. For the future maybe coupling of models for computational fluid dynamics, agglomeration, inclusion separation, dissolution and slag entrainment in addition with experimental physical property data can provide a better overview and understanding.

  • 3079.
    Wikström, Jenny
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jonsson, Lage
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Application of a model for liquid inclusion separation at a steel-slag interface for laboratory and industrial situations2008In: Steel Research International, ISSN 1611-3683, Vol. 79, no 11, p. 826-834Article in journal (Refereed)
    Abstract [en]

    A mathematical model based on the equations of particle motion was used to predict inclusion behavior observed at steel-slag interface in an in-situ Confocal Scanning Laser Microscope. The results show that the model can be used to explain some phenomena observed in the experiments. In addition, a parameter study was done in order to illustrate how the model can be used to study the effect of physical properties on the inclusion behavior at the slag-steel interface for some typical industrial ladle metallurgy conditions. Furthermore, to study the effect of steel temperature, sulfur and oxygen content in the steel, slag and inclusion density as well as initial inclusion velocity on the inclusions behavior at the slag-steel interface. The results show that the temperature and initial velocity was of less importance and that the oxygen content in the steel had a larger influence on the inclusion behavior than the sulfur content in the steel.

  • 3080.
    Wikström, Jenny
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Shibata, H.
    IMRAM Institute, Tohoku University, Sendai.
    Tilliander, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    In situ studies of agglomeration between Al2O3-CaO inclusions at metal/gas, metal/slag interfaces and in slag2008In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 35, no 8, p. 589-599Article in journal (Refereed)
    Abstract [en]

    Studies of inclusion behaviour at the metal/slag interface is of great importance for the steel industry in order to achieve better control of both the size and amount of the inclusions, as well as improving the steel quality and the casting process. In this work agglomeration of liquid Al2O3-CaO particles at both steel/argon gas and steel/slag interfaces was studied with a confocal scanning laser microscope. In addition, agglomeration of liquid Al2O3-CaO-SiO2 inclusions present in the slag was investigated. The results showed that liquid inclusions more easily agglomerated to semiliquid inclusions than to liquid inclusions. Moreover, the agglomeration of liquid particles was found to be improved remarkably when the particles were present in the slag compared to when they were in the steel/slag interface.

  • 3081.
    Wikström, Jenny
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Nakajima, Keiji
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Shibata, H.
    Tilliander, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    In situ studies of the agglomeration phenomena for calcium-alumina inclusions at liquid steel-liquid slag interface and in the slag2008In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 495, no 1-2, p. 316-319Article in journal (Refereed)
    Abstract [en]

    Studies of inclusion behavior at the metal-slag interface are of great importance for the steel industry in order to obtain better control of the size and of inclusions as well as improving the steel quality and casting process. In this work the agglomeration of liquid Al2O3-CaO particles at the liquid steel-liquid slag interfaces are studied with a confocal scanning laser microscope. In addition, the agglomeration of liquid Al2O3-CaO inclusions already transferred to the slag is investigated. It is found that agglomeration of the liquid inclusions at the steel-slag interface could only take place when the inclusions were forced towards each other, while the agglomeration of liquid particles was seen to be noticeably enhanced when the particles were already in the slag.

  • 3082.
    Wikström, Patrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    A study of surface temperature and heat flux estimations in heating processes by solving an Inverse Heat Conduction Problem2006Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The topic of this thesis is estimation of the dynamic changes of the surface temperatureand heat flux during heating processes by using an inverse method. The local transient surface temperature and heat flux of a steel slab are calculated based on measurements in the interior of the slab.

    The motivations for using an inverse method may be manifold. Sometimes, especially in the field of thermal engineering, one wants to calculate the transient temperature or heat flux on the surface of a body. This body may be a slab, or billet in metallurgical applications. However, it may be the case that the surface for some reason is inaccessible to exterior measurements with the aid of some measurement device. Such a device could be a thermocouple if contact with the surface in question is possible or a pyrometer if an invasive method is preferred. Sometimes though, these kinds of devices may be an inappropriate choice. It could be the case that the installation of any such device may disturb the experiment in some way or that the environment is chemically destructive or just that the instruments might give incorrect results. In these situations one is directed to using an inverse method based on interior measurements in the body, and in which the desired temperature is calculated by a numerical procedure.

    The mathematical model used was applied to experimental data from a small scale laboratory furnace as well as from a full scale industrial reheating furnace and the results verified that the method can be successfully applied to high temperature thermal applications.

  • 3083.
    Wikström, Patrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Application of inverse method to heat conduction with chemical process on the boundary2007Doctoral thesis, comprehensive summary (Other scientific)
  • 3084.
    Wikström, Patrik
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
    Blasiak, Wlodzimierz
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
    Berntsson, Fredrik
    Department of Mathematics, Division of Numerical Analysis, Linköping University.
    Estimation of the transient surface temperature and heat flux of a steel slab using an inverse method2007In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 27, no 14-15, p. 2463-2472Article in journal (Refereed)
    Abstract [en]

    In the steel industry it is of great importance to be able to control the surface temperature and heating- or cooling rates during heat treatment processes. An experiment was performed in which a steel slab was heated up to 1250 degrees C in a fuel fired test furnace. The transient surface temperature and heat flux of a steel slab is calculated using a model for inverse heat conduction. That is, the time dependent local surface temperature and heat flux of a slab is calculated on the basis of temperature measurements in selected points of its interior by using a model of inverse heat conduction. Time- and temperature histories were measured at three points inside a steel slab. Measured temperature histories at the two lower locations of the slab were used as input to calculate the temperature at the position of the third location. A comparison of the experimentally measured and the calculated temperature histories was made to verify the model. The results showed very good agreement and suggest that this model can be applied to similar applications in the Steel industry or in other areas where the target of investigation for some reason is inaccessible to direct measurements.

  • 3085.
    Wikström, Patrik
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Blasiak, Wlodzimierz
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Berntsson, Fredrik
    Department of Mathematics, Linköping University.
    Estimation of the transient surface temperature, heat flux and effective heat transfer coefficient of a slab in an industrial reheating furnace by using an inverse method2007In: Steel Research International, ISSN 1611-3683, Vol. 78, no 1, p. 63-70Article in journal (Refereed)
    Abstract [en]

    In the steel industry it is of great importance to be able to control the surface temperature and heating or cooling rates during heat treatment processes. In this paper, a steel slab is heated up to 1300 degrees C in an industrial reheating furnace and the temperature data are recorded during the reheating process. The transient local surface temperature, heat flux and effective heat transfer coefficient of the steel slab ares calculated using a model for inverse heat conduction. The calculated surface temperatures are compared with the temperatures achieved by using a model of the heating process with the help of the software STEELTEMP (R) 2D. The results obtained show very good agreement and suggest that the inverse method can be applied to similar high temperature applications with very good accuracy.

  • 3086.
    Wikström, Patrik
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Blasiak, Wlodzimierz
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Du, Sichen
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    A study on oxide scale formation of low-carbon steel using thermo gravimetric technique2008In: Ironmaking and Steelmaking, ISSN 0301-9233, Vol. 35, no 8, p. 621-632Article in journal (Refereed)
    Abstract [en]

    The aim of this paper was to investigate the effect of oxygen content and temperature on the formation of oxide scales of four different steel grades. Thermo gravimetric experiments were carried out. Small samples of low carbon steels with different compositions were exposed to a gas containing a certain amount of oxygen and at temperatures in the range of 1373-1623 K. The mass gain of the steel sample was recorded. On the basis of the oxidation curves, the parabolic rate constants were reported. Post-experimental investigation of the samples was performed using scanning electron microscope and light optical microscope techniques. The results were compared with the scanning electron microscopy graphs of the steel samples taken from the real industrial reheating furnace.

  • 3087.
    Wilberfors, F.
    et al.
    ScaniaCV AB, Engine Development, Södertälje, Sweden.
    Svensson, Ingvar L.
    Jönköping University, School of Engineering, JTH, Materials and Manufacturing. Jönköping University, School of Engineering, JTH. Research area Materials and manufacturing – Casting.
    Elfsberg, J.
    Scania CV AB, Materials Technology, Södertälje, Sweden.
    Richnau, K.
    Scania CV AB, Materials Technology, Södertälje, Sweden.
    Ipek, N.
    Scania CV AB, Materials Technology, Södertälje, Sweden.
    Local chill as a mean of increasing strength in grey cast iron2016In: International Journal of Cast Metals Research, ISSN 1364-0461, E-ISSN 1743-1336, Vol. 29, no 1-2, p. 40-46Article in journal (Refereed)
    Abstract [en]

    The influence of a chill on the mechanical properties and microstructural features in grey cast iron has been studied. Some of the main findings were that the chill refined the microstructure and modified the graphite distribution from A to D/E. Eutectic cell size was reduced by 60–70%. The Brinell hardness increased while the Vickers hardness, measured in dendrite arms, was unaffected. Fatigue testing in four point bending showed that the fatigue limit was increased by 20–30% in the chilled samples. An increase in tensile strength, proof strength and Young’s modulus was also observed in the chilled samples. The increase in fatigue limit was approximately twice as high as the increase in tensile strength. A possible explanation could be that the eutectic cell size had a more pronounced effect on the fatigue limit than on the tensile strength.

  • 3088.
    Wilkstrom, Patrik
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Weihong, Yang
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Blasiak, Wlodzimierz
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    The influence of oxide scale on heat transfer during reheating of steel2008In: Steel Research International, ISSN 1611-3683, Vol. 79, no 10, p. 765-775Article in journal (Refereed)
    Abstract [en]

    The present work presents methodology and development of a mathematical model for prediction of the influence of oxide scale on heat transfer during reheating of steel in an industrial furnace. In this developed model, temperatures inside the steel billet were measured and with thermocouples at selected places and were collected by a water cooled computer that was traveling inside the slab. CFD is used to calculate the flow field inside of a furnace. The mass-transfer coefficient of the scale formation is obtained by solving the convection mass-diffusion equation across a boundary layer to the surface of a flat plate. A model for inverse heat conduction is employed to calculate the local surface temperature and heat flux on top of the growing oxide scale layer on a slab moving through a walking beam reheating furnace. By using the inverse method, the transient temperature and heat flux was firstly determined on the surface of the steel. During subsequent computations, the growth of the scale was calculated and the surface temperature of the oxide scale was extracted by using the Cauchy data from the previous calculations. The sensibility of the model on steel physical parameters is studied, and suitable parameters were obtained for heating a low carbon steel plate in the reheating furnace. Results show that the oxide scale layer should not be neglected in reheating models.

  • 3089.
    Wu, Guangxin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Shanghai Univ, State Key Lab Adv Special Steel, Shanghai 200072, Peoples R China.;Shanghai Univ, Shanghai Key Lab Adv Ferromet, Shanghai 200072, Peoples R China.;Shanghai Univ, Sch Mat Sci & Engn, Shanghai 200072, Peoples R China.
    Guan, Chuang
    South Polar New Mat Shanghai Co Ltd, Shanghai 201908, Peoples R China..
    Tan, Ning
    Baosteel Grp, Cent Res Inst, Shanghai 201900, Peoples R China..
    Zhang, Jieyu
    Shanghai Univ, State Key Lab Adv Special Steel, Shanghai 200072, Peoples R China.;Shanghai Univ, Shanghai Key Lab Adv Ferromet, Shanghai 200072, Peoples R China.;Shanghai Univ, Sch Mat Sci & Engn, Shanghai 200072, Peoples R China..
    Effect of Hot Rolled Substrate of Hydrogen Reduction on Interfacial Reaction Layer of Hot-dip Galvanizing2018In: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 259, p. 134-140Article in journal (Refereed)
    Abstract [en]

    The effect of morphology of substrate on intermetallic layer is studied in this work by combining the hydrogen reduction descaling of hot rolled steel and galvanizing process. The results show that the morphology of iron reduced at different temperatures can be divided into porous and dense iron surface. The interfacial reaction layer on steel strip with porous iron is composed of xi phase and delta phase, and the phase in coating is invariable with the increasing of soaking time. However, the interfacial reaction layer on steel strip with dense iron is considered to be Fe2Al5Znx intermetallic layer. As the time goes up, a columnar xi phase forms on the intermetallic layer of steel strip reduced at 700 degrees C and the Fe-Al intermetallic layer disappears gradually. In addition, the bursting phenomenon of intermetallic layer occurs after dipping for 10s on steel strip reduced at 800 degrees C, and the delta phase forms on the interface between the "outburst" Fe-Al phase and substrate. The possible mechanisms involved in the formation of Fe-Al and Fe-Zn alloys were also discussed.

  • 3090.
    Wu, Guangxin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. State Key Laboratory of Advanced Special Steel & Shanghai Key Laboratory of Advanced Ferrometallurgy & School of Materials Science and Engineering, Shanghai University, Shanghai 200072, China.
    Zhang, Jieyu
    State Key Laboratory of Advanced Special Steel & Shanghai Key Laboratory of Advanced Ferrometallurgy & School of Materials Science and Engineering, Shanghai University, Shanghai 200072, China.
    Effect of water pressure and soaking time on the selective oxidation of DP980 advanced high strength steel2018In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 453, p. 252-262Article in journal (Refereed)
    Abstract [en]

    Due to the limited heating power in non-oxidation furnace of continuous strip processing facilities of heating stage, selective oxidation with higher oxygen pressure is practically inevitable, which will greatly influence the quality of coating during immersion into the zinc bath. In this paper, the oxidation behaviors of DP980 advanced high strength steel are studied during annealing in a pure H2 atmosphere with controlled water pressure ranging from 0.033 to 0.094 bar (PH2O/PH2) and soaking time from 30 s to 2 h. The oxidation proceeds as a combination of external formation of Mn oxides and internal formation of Mn2SiO4, MnSiO3 and SiO2 from the subsurface of the steel into the matrix. As the water pressure increases from 0.033 to 0.094 bar, it can be seen that the amount of oxide particles and coverage on the surface of the steel seems to decrease initially and increase afterwards. The sequence of oxides determined by oxygen partial pressure was calculated and illustrated using thermodynamics with alloys activity. Oxide growth mechanism during annealing and the effect of water pressure on the amount of oxide particles were also discussed.

  • 3091.
    Wu, Laner
    et al.
    School of Material Science & Engineering, Beifang University of Nationality, Yinchuan, Ningxia.
    Han, Fenglan
    School of Material Science & Engineering, Beifang University of Nationality, Yinchuan, Ningxia.
    Yang, Qixing
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Guo, Shengwei
    School of Material Science & Engineering, Beifang University of Nationality, Yinchuan, Ningxia.
    Fluoride emissions from Pidgeon process for magnesium production2012Conference paper (Refereed)
    Abstract [en]

    Primary magnesium is nowadays produced in China via Pidgeon process. An important reaction in the process is silicothermic reduction of MgO from dolime near 1200ºC under pressure of 2-10 Pa to generate Mg vapor. Fluorite, ranging 2-3% (mass fraction), is usually mixed with the raw materials to catalyze the reaction. Under the process conditions, CaF2 in the fluorite may form some fluorides to vaporize, thus polluting air. The fluorides remaining in the solid process waste, the Mg slag, may be dissolved to cause water pollution.In the present study, experiments were performed by using retorts of pilot scale in a maffle furnace to simulate the Pidgeon process for primary Mg production. The test materials, briquettes of 5.6-10 kg made of dolime, ferrosilicon and fluorite, were charged in the retorts and heated under conditions similar to the industry operation. Fluoride minerals in the Mg slag from the simulation experiments were identified by XRD and SEM-EDS techniques. Quantities of some F-containing phases formed in the process under equilibrium condition were calculated by FactSage 6.2 thermodynamic package. Fluoride distributions were determined to establish an F-balance among the input and output materials. Besides, slag samples from a magnesium plant were also characterized, including leaching test according to EN 12457-2.Based on these results, fluoride impacts on the environment were evaluated and discussed. Suggestions were also presented to minimize the environmental impacts from primary Mg production using the Pidgeon process.

  • 3092.
    Wu, Laner
    et al.
    School of Material Science and Engineering, Beifang University of Nationalities, Wenchangbeilu, Yinchuan.
    Yang, Qixing
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Han, FengLan
    School of Material Science and Engineering, Beifang University of Nationalities, Wenchangbeilu, Yinchuan.
    Du, Chun
    School of Chemical Engineering, Beifang University of Nationalities, Yinchuan.
    Dusting control of magnesium slag produced by Pidgeon process2013In: Powders and grains 2013: proceedings of the 7th International Conference on Micromechanics of Granular Media : Sydney, Australia: 8-12 July 2013 / [ed] Aibing Yu, Melville, NY: American Institute of Physics (AIP), 2013, p. 1282-1285Conference paper (Refereed)
    Abstract [en]

    Magnesium production by Pidgeon process has been developed very fast in China since 1990's. The waste slag from magnesium production has attracted broad attention because the huge amounts of the slag. For each ton of magnesium produced, there will be 6-8 tons of the slag generated. A big part of the Mg slag exists as fine dust with particle size of D95 < 0.1mm, which may pollute air, soil and water surrounding the Mg industry. The fine particles are generated by phase transformations of dicalcium silicate C2S (2CaOṡSiO 2) during the slag cooling. There is a volume expansion of more than 10% with the transformation of β-C2S to γ-C2S phase, causing a disintegration or dusting of the Mg slag. In the present study, several chemical stabilizers were used to treat the dusting Mg slag at 1200°C, including borates, phosphates and rare earth oxides, in order to obtain volume stable slag aggregates for environmental protection and recycling of the Mg slag. The volume expanding rates of the samples were measured. XRD and SEM studies were carried out to confirm effects of the stabilizers. The results show that all of the stabilizers were effective for the stabilization of Mg slag. Some differences between the stabilizers were also described and discussed

  • 3093.
    Wu, Liushun
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Study of slag droplet formation in a gas-stirred ladle using cold models2011In: Steel Grips - Journal of Steel and Related Materials, ISSN 1611-4442, E-ISSN 1866-8453, Vol. 9, p. 51-55Article in journal (Refereed)
    Abstract [en]

    Two cold models were employed to simulate the formation of slag droplets in a gas-stirred ladle. How do gas flow rate and interfacial tension between bath liquid and top liquid effect droplet size? Further, a semi-empirical model was developed to describe the size of the droplets of the water model. What else can it be used for with reasonably good agreement?

  • 3094.
    Wu, Liushun
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Valentin, P.
    Sichen, Du
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Study of Open Eye Formation in an Argon Stirred Ladle2010In: STEEL RES INT, ISSN 1611-3683, Vol. 81, no 7, p. 508-515Article in journal (Refereed)
    Abstract [en]

    Two cold models were employed to simulate the formation of open-eyes in a gas stirred ladle. In the first model, water and silicon oils were employed to simulate liquid steel and slag respectively. In the second one, liquid Ga-In-Sn alloy was used to simulate liquid steel, while 12% hydrochloric acid simulated the top slag. The experimental results indicated that the gas flow rate, height of the lower liquid and height of the top liquid has a strong impact on the open-eye size. On the other hand, the viscosity of the top liquid and the interfacial tension between the two liquids had only little effect on the open-eye size. A semi-empirical model was developed to describe the size of open-eye as a function of the heights of the two adults and the gas flow rate. The two sets of parameters obtained for the the water and Ga-In-Sn models were very different Industrial trials were also conducted to examine the applicability of the models. The model developed based on the Ga-In-Sn model could well predict the formation of an open-eye during ladle treatment. The model could be adopted by the industry to estimate the real gas flow rate by measuring the size of the open-eye online. On the other hand, the mathematical model based on water model experiments was unsatisfactory when applied to the industrial ladle process.

  • 3095.
    Wu, L.-M.
    Luleå tekniska universitet.
    Characteristics of steelmaking flue dust1999In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 26, no 5, p. 372-377Article in journal (Refereed)
    Abstract [en]

    The physicochemical and surface properties of steelmaking flue dust have been investigated by scanning electron (SEM) and X-ray diffraction (XRD) measurements, chemical analysis, FT-IR studies, zeta potential measurement, Brunauer-Emmett-Teller (BET) surface area determination, and potentiometric titration techniques. The results show that the dust consists of very fine spherical particles, which contain mainly iron oxide, iron ferrite, calcium (magnesium) oxide, calcium (magnesium) carbonate, and other metal oxides. The dust possesses a high BET surface area (14·65 m2 g-1 ) and a reversible surface charge. The point of zero charge pHpzc of the surface is around pH 6. Solubility tests show that the dust releases very little heavy metals in solution in the pH range 4·5-11·8 and has a high capacity to neutralise strong acid in solution

  • 3096.
    Wu, L.N.
    et al.
    Beifang University of Nationality, Yinchuan, Ningxia.
    Han, F.L.
    Beifang University of Nationality, Yinchuan, Ningxia.
    Yang, Qixing
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Du, C.
    Beifang University of Nationality, Yinchuan, Ningxia.
    Xu, A.J.
    School of Metallurgical and Ecological Engineering, University of Science and Technology, Beijing.
    Li, J.L.
    School of Metallurgical and Ecological Engineering, University of Science and Technology, Beijing.
    Fluorine vaporization and leaching from Mg slag treated at different conditions2013In: Advanced Materials Research, ISSN 1022-6680, E-ISSN 1662-8985, Vol. 753-755, p. 88-94Article in journal (Refereed)
    Abstract [en]

    Both treatments and leaching tests of an Mg slag sample containing F of 2.15% from an Mg factory in northwest China were conducted in the present study, focusing on problems of F pollutions. By treating at 1000-1200°C in a muffle furnace, F leaching was decreased to a minimum level of 0.49-2.85 mg/l from the Mg slag with an original F leaching of 13.9 mg/l. The F leaching values increased to 4.83-95.5 mg/l, while treating the slag samples in a vacuum furnace. The treatments of Mg slag may thus be carried out in oxidizing atmosphere and under 1200°C to minimize fluorine pollutions and to improve environmental performances of the Pidgeon process.

  • 3097. Wunderlich, R. K.
    et al.
    Fecht, H. -J
    Egry, I.
    Etay, J.
    Battezzati, L.
    Ricci, E.
    Matsushita, Taishi
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Thermophysical Properties of a Fe-Cr-Mo Alloy in the Solid and Liquid Phase2012In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 83, no 1, p. 43-54Article in journal (Refereed)
    Abstract [en]

    Results of a thermophysical characterization of a Fe-Cr-Mo alloy in the solid and liquid phases are reported. Methods applied include calorimetry, dilatometry; the laser flash technique for thermal diffusivity measurement and ultrasound pulse echo for the measurement of the room temperature sound velocities and elastic constants. Density in the liquid phase and surface tension were measured by optical dilatometry and by the oscillating drop method on electromagnetic levitated specimen. In addition, surface tension and viscosity were measured by the oscillating drop method on board parabolic flights under reduced gravity conditions. The methods applied and results obtained are presented. This work represents a collaborative effort, including round robin measurements in different laboratories for a characterization of the basic thermophysical properties needed for process simulation.

  • 3098.
    Wänerholm, Martin
    et al.
    RISE - Research Institutes of Sweden, Swerea, Swerea SWECAST.
    Heintz, Ida
    Minskat metallspill: Effektivare resursutnyttjande hos gjuterier och plåtindustri2016Report (Other academic)
    Abstract [sv]

    Tanken med projektet Spill till guld har varit att utveckla en internettjänst där det finns möjlighet att försöka sälja sitt material till intresserade användare alternativt knyta kontakter som kan användas för att hitta nya idéer hur man tar hand om sina restprodukter och kanske förädlar dessa.

    I arbetspaket metall har olika metoder för att få avsättning för slagg och metallinnehållande stoft från gjuterier studerats. Dessutom har möjligheten att minska mängden plåtspill vid tillskärning utretts.

    Först studerades möjligheter att återta metallstoftet till den egna processen och vad det skulle innebära ekonomiskt och hur hanteringen skulle ske. De stoft som analyserades innehöll dock en del annat än bara metall, till exempel sandrester och det visade sig därför vara svårt att få ekonomi i att föra tillbaka till den egna smältugnen. Andra projekt som genomförts visar att stoft med högre metallhalt eller som innehåller lite mer värdefulla metaller kan vara mer lönsamt. Det är alltså viktigt att skaffa kunskap om de stoft man har. Om stoftet ska återföras måste man hantera stoftet på ett bra sätt så att det inte flyger i väg när det läggs i smältan. Ett bra sätt att få god hantering är genom brikettering.

    Nästa steg var att undersöka om gjuteriernas restprodukter kunde användas i en annan bransch. Det mest naturliga var då att titta på om järn- och stålindustrin kunde ha ett intresse. Även här kan konstateras att stoft innehållande sandrester inte är helt optimalt och att det är svårt att få ekonomi i detta. Att separera olika material ur ett stoft kan vara ett viktigt steg för att få bättre ekonomi i återvinningen.

    När det gäller slagg från gjuterier i allmänhet kan dessa ibland innehålla relativt höga halter av rent järn och kan då säljas som skrot direkt. Ett antal olika användningsområden för olika typer av slagg har studerats både inom järn- och stålindustrin men även på annat håll. Även här har det varit svårt att få ekonomi i återvinningen av slagg. Inom projektet har kontakt även tagits med värmeverk för att se om slagg från gjuterier skulle kunna förbättra förbränningen i deras sandbäddar. Detta ser lovande ut och vidare diskussioner förs.

    Gällande minskat spill i plåtbranschen har en fallstudie genomförts samt omvärldsbevakning vid två mässor. Fallstudien visade på potential att minska plåtspill vid tillskärning av plåtkomponenter med laserskärmaskin från formatplåt genom användning av nya smartare nestingprogram. Hur stora vinster som kan göras beror på flera faktorer som med vilken tidhorisont som produktionen planeras, geometrin på komponenterna samt hur modern utrustning som används.

  • 3099.
    Xia, Wei
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Initial evaluation of briquetting possibilities of CaO-containing paper production waste: For use in metallurgical processes2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Paper and pulp industry and steel industry are two major industries in Sweden, both of which are facing big challenges to treat their waste products properly. In this thesis work, initial evaluation of mechanical properties of briquettes made of waste products was performed. Three different CaO-containing waste products (Mesa, Kalk, Fly Ash) from Stora Enso and SCA were pressed with one kind of binding material (AOD slag) from Outokumpu. Drop tests were carried out to test the impact strength of the lab-made briquettes.

    Three different parameters were investigated of their influence on the impact strength of the briquettes: 1) Composition of briquettes 2) Heat treatment procedure 3) Exposure time to open air. A total of 97 briquettes were pressed. Drop test results show that for different material based briquettes, heat-treatment and exposure to open air had different influence on the final impact strength. In order to get best impact strength, MB briquettes (90% Mesa +10% AOD slag) heat treated at 850℃, KB briquettes (90% Kalk +10% AOD slag) heat treated at 850℃ and FC briquettes (80% Fly Ash + 20% AOD slag) exposed to open air for 20 days are recommended.

    Melting experiment was carried out to investigate the sulphur removal ability of the briquettes in metallurgical processes. Thermodynamic calculation of sulphide capacity was done.

  • 3100.
    Xiang, Shengmei
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    High-Temperature Corrosion-Fatigue of Cast Alloys for Exhaust Manifolds2018Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The introduction of gas-driven Otto engine and the corresponding usage of bio-fuels in heavy-duty engines will render the exhaust atmosphere more corrosive and bring a higher working temperature to exhaust manifolds. The current service material, a ferritic ductile cast iron called SiMo51, will soon meet its upper temperature limit set by the ferrite-austenite transformation at 860ºC. Three alternative materials, as well as SiMo51 serving as reference, are investigated in the present thesis emphasizing on high-temperature corrosion fatigue. 

    The first aim of this study is to obtain material data and give a quantitative ranking of the materials’ performance. Low-cycle fatigue (LCF) tests at 800ºC in a synthetic exhaust gas (5%O2-10%CO2-5%H2O-1ppmSO2-N2 bal.) are conducted to evaluate the materials’ performance in simulated real working scenarios, where high-temperature, corrosive atmosphere and fatigue conditions during testings are similar to the conditions experienced by the exhaust manifolds. To evaluate the individual effect from high-temperature fatigue and isolate the impact from corrosion, the materials are tested under the same settings but in an argon atmosphere. To evaluate the individual effect from high-temperature corrosion and isolate the impact from mechanical deformation, oxidation tests are carried out at 800ºC in the same synthetic exhaust gas. The second aim is to identify and understand different oxidation behavior and failure mechanisms in the materials, realized by considerable characterizations of the tested specimens.

    From the fatigue tests, it is found that the austenitic stainless steel HK30 has the highest fatigue resistance, followed by the austenitic cast iron Ni-resist D5S, and the ferritic ductile cast irons SiMo1000 and SiMo51, a ranking valid in both atmospheres. In the exhaust atmosphere, for instance, the improvement in fatigue strength at 15,000 cycles relative to SiMo51 are 260%, 194% and 26%, respectively. Different crack initiation and propagation mechanisms are found for the various combinations of materials and atmospheres. In the exhaust atmosphere, for instance, crack initiation is assisted by oxide intrusion in SiMo51 and crack propagation is affected by crack branching in HK30, mechanisms not observed in argon. By comparing the S-N fatigue curves in the two atmospheres, the influence of oxidation on fatigue life is evaluated. The fatigue life of the cast irons are surprisingly found to be higher in the exhaust atmosphere. Several explanations are suggested for this, considering their very different oxidation behaviors. 

    This study provides accurate test data that can be used to help industry avoid over-dimensioned design. The investigation of the failure mechanisms promotes better understanding of the correlation between microstructure and mechanical properties. Moreover, the combination of fatigue tests in argon, fatigue tests in exhaust and oxidation tests in exhaust, shows how corrosion and fatigue individually and synergistically affect the materials’ performance at high temperature.

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