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  • 1. Abbasalizadeh, A.
    et al.
    Teng, Lidong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Sietsma, J.
    Yang, Y.
    Rare Earth Extraction from NdFeB Magnets and Rare Earth Oxides Using Aluminum Chloride/Fluoride Molten Salts2015Ingår i: Rare Earths Industry: Technological, Economic, and Environmental Implications, Elsevier, 2015, s. 357-373Kapitel i bok, del av antologi (Övrigt vetenskapligt)
    Abstract [en]

    In the current research, the feasibility of the recovery of neodymium and dysprosium from spent NdFeB magnets (about 6wt% Dy) was investigated using molten salt processes. The salt bath consisted of a eutectic composition of an NaCl-KCl-LiCl mixture. To enable the efficient dissolution of metal in the molten salt phase, AlCl3 was used as a chlorinating agent. Iron-free electrodeposition was carried out successfully. Energy-dispersive spectroscopic analysis of the electrodeposit revealed that co-deposition of the dysprosium occurs along with neodymium at the cathode. The process shows that this method is well suited for recovering rare earth metals from magnetic scrap containing these metals.Furthermore, the setup design for recovery of neodymium and dysprosium from their oxides was investigated with regard to previous studies on the neodymium magnets. The stability of different fluoride and chloride salts was studied by means of thermodynamic calculation. Aluminum fluoride-based molten salt systems were studied in detail as the electrolyte for electrochemical extraction of rare earth oxides into rare earth metal elements with Al.

  • 2.
    Abbasalizadeh, Aida
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Teng, Lidong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Sridhar, Seetharaman
    Grinder, Olle
    Izumi, Yukari
    Barati, Mansoor
    Highlights of the Salt Extraction Process2013Ingår i: JOM: The Member Journal of TMS, ISSN 1047-4838, E-ISSN 1543-1851, Vol. 65, nr 11, s. 1552-1558Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This article presents the salient features of a new process for the recovery of metal values from secondary sources and waste materials such as slag and flue dusts. It is also feasible in extracting metals such as nickel and cobalt from ores that normally are difficult to enrich and process metallurgically. The salt extraction process is based on extraction of the metals from the raw materials by a molten salt bath consisting of NaCl, LiCl, and KCl corresponding to the eutectic composition with AlCl3 as the chlorinating agent. The process is operated in the temperature range 973 K (700 degrees C) to 1173 K (900 degrees C). The process was shown to be successful in extracting Cr and Fe from electric arc furnace (EAF) slag. Electrolytic copper could be produced from copper concentrate based on chalcopyrite in a single step. Conducting the process in oxygen-free atmosphere, sulfur could be captured in the elemental form. The method proved to be successful in extracting lead from spent cathode ray tubes. In order to prevent the loss of AlCl3 in the vapor form and also chlorine gas emission at the cathode during the electrolysis, liquid aluminum was used. The process was shown to be successful in extracting Nd and Dy from magnetic scrap. The method is a highly promising process route for the recovery of strategic metals. It also has the added advantage of being environmentally friendly.

  • 3.
    Abbasalizadeh, Aida
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Teng, Lidong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Seetharaman, S.
    Dysprosium extraction using molten salt process2014Ingår i: Rare metal technology 2014: proceedings of a symposium sponsored by The Minerals, Metals & Materials Society (TMS) held during TMS 2014, 143rd Annual Meeting & Exhibition, February 16-20, 2014, San Diego Convention Center, San Diego, California, USA, 2014, s. 207-208Konferensbidrag (Refereegranskat)
  • 4.
    Abbasalizadeh, Aida
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Teng, Lidong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Sridhar, S.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Neodymium extraction using salt extraction process2015Ingår i: Mineral Processing and Extractive Metallurgy: Transactions of the Institutions of Mining and Metallurgy: Section C, ISSN 0371-9553, E-ISSN 1743-2855, Vol. 124, nr 4, s. 191-198Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The present paper deals with the feasibility of the neodymium recovery from spent Nd-Fe-B magnets using molten salt electrodeposition method. The salt bath consisted of a mixture of LiCl- KCl-NaCl corresponding to the eutectic composition. The experimental set-up with its salient features is presented. AlCl3 was used as flux and graphite rods dipped in the salt bath served as electrodes. The voltage for the electrolysis was chosen on the basis of the decomposition potential of NdCl3. The reaction sequence can be described as Iron-free neodymium deposition could be carried out successfully. In view of the proximity of the electrode potentials, the co-deposition of the aluminium and neodymium was observed to occur at the cathode, as revealed by SEM/EDS and XRD analyses of the electrodeposit.

  • 5.
    Abdoshahi, Neda
    et al.
    Univ Leoben, Dept Mat Sci, Franz Josef Str 18, A-8700 Leoben, Austria..
    Dehghani, Mohammad
    Mat Ctr Leoben Forsch GmbH, Roseggerstr 12, A-8700 Leoben, Austria..
    Hatzenbichler, Lukas
    Univ Leoben, Dept Mat Sci, Franz Josef Str 18, A-8700 Leoben, Austria..
    Spoerk-Erdely, Petra
    Univ Leoben, Dept Mat Sci, Franz Josef Str 18, A-8700 Leoben, Austria..
    Ruban, Andrei V.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap. Mat Ctr Leoben Forsch GmbH, Roseggerstr 12, A-8700 Leoben, Austria.
    Musi, Michael
    Univ Leoben, Dept Mat Sci, Franz Josef Str 18, A-8700 Leoben, Austria..
    Mayer, Svea
    Univ Leoben, Dept Mat Sci, Franz Josef Str 18, A-8700 Leoben, Austria..
    Spitaler, Juergen
    Mat Ctr Leoben Forsch GmbH, Roseggerstr 12, A-8700 Leoben, Austria..
    Holec, David
    Univ Leoben, Dept Mat Sci, Franz Josef Str 18, A-8700 Leoben, Austria..
    Structural stability and mechanical properties of TiAl plus Mo alloys: A comprehensive ab initio study2021Ingår i: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 221, s. 117427-, artikel-id 117427Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Titanium aluminides are technologically important intermetallic alloys with also many curious properties interesting from a basic research point of view. When alloyed with Mo, several (meta)stable phases have been reported; their properties are, however, largely unknown due to the alloy processing (e.g. fast cooling) and/or non-existence as a single-phase material. Here we employ first principles calculations to study compositional trends in structural and mechanical properties. We could show that Mo increases the density of all studied phases, leads to their chemical destabilization with the exception of the ordered bcc /3o phase, increases their ductility, and enhances the elastic anisotropy. Discrepancies between two employed ab initio methods (special quasi-random structures vs. coherent potential approximation) in the case of the /3o and B19 phases are rationalized with significant local distortions which may eventually facilitate a spontaneous phase transformation. Predictions of ordering temperatures solely based on the configurational entropy do not yield values in the experimentally expected ranges.

  • 6.
    Abdoshahi, Neda
    et al.
    Univ Leoben, Dept Mat Sci, Franz Josef Str 18, A-8700 Leoben, Austria..
    Dehghani, Mohammad
    Mat Ctr Leoben Forsch GmbH, Roseggerstr 12, A-8700 Leoben, Austria..
    Ruban, Andrei V.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Strukturer. Mat Ctr Leoben Forsch GmbH, Roseggerstr 12, A-8700 Leoben, Austria..
    Friak, Martin
    Czech Acad Sci, Inst Phys Mat, Zizkova 22, CZ-61662 Brno, Czech Republic.;Brno Univ Technol, Fac Mech Engn, Inst Mat Sci & Engn, Tech 2896-2, CZ-61669 Brno, Czech Republic..
    Sob, Mojmir
    Czech Acad Sci, Inst Phys Mat, Zizkova 22, CZ-61662 Brno, Czech Republic.;Masaryk Univ, Fac Sci, Dept Chem, Kotlarska 2, CZ-61137 Brno, Czech Republic..
    Spitaler, Juergen
    Mat Ctr Leoben Forsch GmbH, Roseggerstr 12, A-8700 Leoben, Austria..
    Holec, David
    Univ Leoben, Dept Mat Sci, Franz Josef Str 18, A-8700 Leoben, Austria..
    On the energetics of the cubic-to-hexagonal transformations in TiAl plus Mo alloys2022Ingår i: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 240, artikel-id 118268Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Diffusionless transformations allow access to metastable phases and enrich the materials design portfolio. They are well suited for atomistic modeling; nonetheless, they are challenging when involving disordered systems or alloys with complex compositions. This work presents a comprehensive study of transforma-tion energetics between bcc and hcp ordered and disordered phases in the TiAl+Mo model alloy system. By employing two complementary techniques I. VASP-SQS, and II. EMTO-CPA, we can show that chemical disorder flattens the energy landscape but may introduce a small barrier. Unlike that, the energetics of ordered phases are barrier-less and hence would suggest a spontaneous transformation. Finally, we show that Mo stabilizes the bcc phases, leading to a barrier-less transformation hcp -+ bcc for both ordered and disordered states when Mo content exceeds ti 12 at.%.

  • 7.
    Abdul Abas, Riad
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Experimental Studies of Thermal Diffusivities concerning some Industrially Important Systems2006Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The main objective of this industrially important work was to gain an increasing understanding of the properties of some industrially important materials such as CMSX-4 nickel base super alloy, 90Ti.6Al.4V alloy, 25Cr:6Ni stainless steel, 0.7% carbon steel, AISI 304 stainless steel-alumina composites, mould powder used in continuous casting of steel as well as coke used in blast furnace with special reference to the thermal diffusivities. The measurements were carried out in a wide temperature range covering solid, liquid, glassy and crystalline states.

    For CMSX-4 alloy, the thermal conductivities were calculated from the experimental thermal diffusivities. Both the diffusivities and conductivities were found to increase with increasing temperature. Microscopic analysis showed the presence of intermetallic phases γ´ such as Ni3Al below 1253 K. In this region, the mean free path of the electrons and phonons is likely to be limited by scattering against lattice defects. Between 1253 K and solidus temperature, these phases dissolved in the alloy adding to the impurities in the matrix, which, in turn, caused a decrease in the thermal diffusivity. This effect was confirmed by annealing the samples at 1573 K. The thermal diffusivities of the annealed samples measured at 1277, 1403 and 1531 K were found to be lower than the thermal diffusivities of non-annealed samples and the values did not show any noticeable change with time. It could be related to the attainment of equilibrium with the completion of the dissolution of γ´ phase during the annealing process. Liquid CMSX-4 does not show any change of thermal diffusivity with temperature. It may be attributed to the decrease of the mean free path being shorter than characteristic distance between two neighbouring atoms.

    Same tendency could be observed in the case of 90Ti.6Al.4V alloy. Since the thermal diffusivity increases with increasing temperature below 1225 K and shows slight decrease or constancy at higher temperature. For 25Cr:6Ni stainless steel, the thermal diffusivity is nearly constant up to about 700 K. Beyond that, there is an increase with temperature both during heating as well as cooling cycle. On the other hand, the slope of the curve increases above 950 K, which can be due to the increase of bcc phase in the structure. 0.7% carbon steel shows a decrease in the thermal diffusivity at temperature below Curie point, where the structure contains bcc+ fcc phases. Above this point the thermal diffusivity increases, where the structure contains only fcc phase. The experimental thermal conductivity values of these alloys show good agreement with the calculated values using Mills model.

    Thermal diffusivity measurements as a function of temperature of sintered AISI 304 stainless steel-alumina composites having various composition, viz, 0.001, 0.01, 0.1, 1, 2, 3, 5, 7, 8 and 10 wt% Al2O3 were carried out in the present work. The thermal diffusivity as well as the thermal conductivity were found to increase with temperature for all composite specimens. The thermal diffusivity/conductivity decreases with increasing weight fraction of alumina in the composites. The experimental results are in good agreement with simple rule of mixture, Eucken equation and developed Ohm´s law model at weight fraction of alumina below 5 wt%. Beyond this, the thermal diffusivity/ conductivity exhibits a high discrepancy probably due to the agglomeration of alumina particles during cold pressing and sintering.

    On the other hand, thermal diffusivities of industrial mould flux having glassy and crystalline states decrease with increasing temperature at lower temperature and are constant at higher temperature except for one glassy sample. The thermal diffusivity is increased with increasing crystallisation degree of mould flux, which is expected from theoretical considerations.

    Analogously, the thermal diffusivity measurements of mould flux do not show any significant change with temperature in liquid state. It is likely to be due to the silicate network being largely broken down.

    In the case of coke, the sample taken from deeper level of the pilot blast furnace is found to have larger thermal diffusivity. This can be correlated to the average crystallite size along the structural c-axis, Lc, which is indicative of the higher degree of graphitisation. This was also confirmed by XRD measurements of the different coke samples. The degree of graphitisation was found to increase with increasing temperature. Further, XRD and heat capacity measurements of coke samples taken from different levels in the shaft of the pilot blast furnace show that the graphitisation of coke was instantaneous between 973 and 1473 K.

    Ladda ner fulltext (pdf)
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  • 8.
    Abdul Abas, Riad
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Hayashi, M.iyuki
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Thermal Diffusivity measurement of CMSX-4 alloy by Laser flash method2007Ingår i: International journal of thermophysics, ISSN 0195-928X, E-ISSN 1572-9567, Vol. 28, nr 1, s. 109-122Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the present work, thermal diffusivity measurements have been carried out on industrial samples of CMSX-4 nickel-base superalloy using the laser-flash method with emphasis on studying the effect of temperature and microstructure on the thermal diffusivity. The measurements were performed in the temperature range from 298 to 1623 K covering both solid as well as liquid ranges. Below 1253 K, the thermal-diffusivity values were found to increase with increasing temperature. Microstructural investigations of quenched samples revealed that below 1253 K, an ordered phase, usually referred to as the -phase was present together with the disordered fcc phase, often referred to as the γ phase. Between 1253 K and the solidus temperature, the phase was found to dissolve in the matrix alloy causing an increase in the disordering of the alloy, and thereby a small decrease in the thermal-diffusivity values. The thermal-diffusivity values of samples pre-annealed at 1573 K exhibited constancy in the temperature range from 1277 to 1513 K, which is attributed to the attainment of thermodynamic equilibrium. These equilibrium values were found to be lower than the results for samples not subjected to annealing. The thermal-diffusivity values of the alloy in the liquid state were found to be independent of temperature.

  • 9.
    Abdul Abas, Riad
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Hayashi, Miyuki
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Thermal Diffusivity Measurements of some Industrially Important Alloys by a Laser Flash Method2007Ingår i: International journal of materials reseach, ISSN 1862-5282, Vol. 98, nr 6, s. 535-540Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the present work, thermal diffusivity measurements of three industrially significant alloys, viz. 90Ti.6Al.4V, stainless steel with 25Cr and 6Ni as well as plain carbon steel with 0.7 % carbon have been carried out as a function of temperature. The aim of this work is to study the effect of temperature and microstructure on the thermal diffusivities of these alloys. For the 90Ti.6Al.4V alloy, thermal diffusivity increases with temperature below 1225 K. Above this temperature, the values started decreasing probably due to the dissolution of Ti3Al intermediate phase in the matrix, which would result in an increase in the disorder of the structure. For 25Cr: 6Ni stainless steel, the thermal diffusivity is nearly constant up to about 700 K. Above this, there is an increase in the thermal diffusivities with temperature during the heating cycle, which was reproducible during thermal cycling. On the other hand, the slope of the curve increases above 950 K.

    In the case of the 0.7 % carbon steel, the thermal diffusivity shows a decreasing trend with temperature below the Curie point for the alloy, where the alloy consists of bcc + fcc phases. Above this point, only the fcc phase is prevalent and the thermal diffusivity was found to increase with temperature. Heat transfer is carried out by lattice vibration (phonons) as well as electrons. The contribution of electrons varies depending upon the type of alloy. In this study, the highest electron contribution was found in 0.7 % carbon steel, while the lowest was in stainless steel. The thermal conductivity values of these alloys are in good agreement with the calculated values using the model proposed by Mills.

  • 10.
    Abelin, Mathias
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Blomkvist, Håkan
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Investigation of the scale factor between full scale ladle furnace process and water models2020Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Skänkmetallurgin är en viktigt process inom stålindustrin. Syftet med denna process är att optimera den kemiska sammansättningen i smältan och att homogenisera temperaturen i vätskan.

    Det är vanligt att modelera denna process med hjälp av vattenmodeller. För att träffsäkert skala dessa modeller krävs en mängd kriterier och skal-faktorer. Det mest centrala fenomenet, utifrån vilket allt annat kan härledas, är två-fas gasplymen som dominerar flödena i skänken. Plymen och dess beroende parametrar är svåra att definera. Vilka som bör användas och hur de används har inte standardiserats. Oro har väckts över om den vanligaste skalningsmetoden ens går att använda i skänkmetallurgi. Denna rapport redogör för studier rörande dessa variabler och deras påverkan på ämnet. Syftet med denna rapport är att belysa olika tillvägagångssätt till att förbättra dessa simulationer med hänsyn till debaterade parametrar.

    Slutsatsen för denna studie lyfter fram anledningarna till varför dessa variabler är av vikt för modellering för skänkmetallurgin. Även framtida arbete som bör utföras föratt ge djupare förståelse för de olika parametrarna belyses.

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    fulltext
  • 11.
    Abouzari, Sara
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Solid solution strengthening effect on creep strength of austenitic stainless steel2012Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Sanicro 25 is a newly developed austenitic stainless steel, designed for the next generation of Ultrasupercritical coal-fired boilers in electrical power plants. This material is applicable in reheater and superheater tubes, where the material temperature is up to 700

    °C. One of the main strengthening mechanisms in high temperature materials is solid solution strengthening. A combination of this mechanism and precipitation hardening, promotes creep strength of heat resistance materials. The aim of this work was to characterize the effects of solid solution strengthening on creep strength of Sanicro 25.Previous works has been done for effects of phosphorous in copper and also for influence of laves phase on the creep properties of CrMo alloys. The results of these two works are used and the model is adapted to austenitic stainless steel. First a Zero starting state was defined which was Alloy 316H and then the calculation was made for Sanicro 25. Thermodynamic calculations were made using DICTRA and Thermo-Calc. Elastic misfit parameter was determined using ab initio calculations. The results from the simulation in this work indicate that solutes with larger size misfit compare to the parent atoms have better solid solution strengthening effect. A decrease in the creep strength by increasing temperature has been observed which could be attributed to growth of laves phase.

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    Solid solution strengthening effect on creep strength of austenitic stainless steel
  • 12. Abu-Odeh, A.
    et al.
    Galvan, E.
    Kirk, T.
    Mao, Huahai
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Chen, Q.
    Mason, P.
    Malak, R.
    Arróyave, R.
    Efficient exploration of the High Entropy Alloy composition-phase space2018Ingår i: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 152, s. 41-57Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    High Entropy Alloys (HEAs), Multi-principal Component Alloys (MCA), or Compositionally Complex Alloys (CCAs) are alloys that contain multiple principal alloying elements. While many HEAs have been shown to have unique properties, their discovery has been largely done through costly and time-consuming trial-and-error approaches, with only an infinitesimally small fraction of the entire possible composition space having been explored. In this work, the exploration of the HEA composition space is framed as a Continuous Constraint Satisfaction Problem (CCSP) and solved using a novel Constraint Satisfaction Algorithm (CSA) for the rapid and robust exploration of alloy thermodynamic spaces. The algorithm is used to discover regions in the HEA Composition-Temperature space that satisfy desired phase constitution requirements. The algorithm is demonstrated against a new (TCHEA1) CALPHAD HEA thermodynamic database. The database is first validated by comparing phase stability predictions against experiments and then the CSA is deployed and tested against design tasks consisting of identifying not only single phase solid solution regions in ternary, quaternary and quinary composition spaces but also the identification of regions that are likely to yield precipitation-strengthened HEAs.

  • 13. Affatato, S.
    et al.
    Leardini, W.
    Jedenmalm, Anneli
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Zavalloni, M.
    Ruggeri, O.
    Tarterini, F.
    Viceconti, M.
    Microstructural effects on the wear resistance of CO-CR implant alloys2006Ingår i: Proceedings of the 8th Biennial Conference on Engineering Systems Design and Analysis, 2006, s. -951Konferensbidrag (Refereegranskat)
    Abstract [en]

    Modem metal-on-metal articulation have been proposed to reduce the incidence of osteolysis due to polyethylene particles debris, as a late complication. The tribology of large metal-on-metal articulations allows theoretical advantages with respect to other configurations, especially for the lubrication regime. This study was aimed to compare the wear performances of different diameters of clinically available acetabular metallic components manufactured in a cast cobalt-chrome alloy. To evaluate the influence of the material properties of wear and microstructure, metal-on-metal components were tested in a hip joint simulator for five million cycles with bovine calf serum as lubricant. In particular, three different configurations of metal-on-metal components (28-mm, 36-mm, 54-mm) were tested. After the test all specimens were examined with optical and electronic scanning microscope. A statistical difference were observed among the three groups tested in the run-in and steady-state wear rates, favoring the larger femoral heads. The results of this study indicate that the 54-mm diameter femoral heads prove a better wear behavior than the smaller configurations.

  • 14.
    Afshari, Davood
    et al.
    Univ Zanjan, Zanjan, Iran..
    Ghaffari, Ali
    Univ Zanjan, Zanjan, Iran..
    Barsoum, Zuheir
    KTH, Skolan för teknikvetenskap (SCI), Teknisk mekanik, Farkostteknik och Solidmekanik.
    Optimization in the Resistant Spot-Welding Process of AZ61 Magnesium Alloy2022Ingår i: Strojniski vestnik, ISSN 0039-2480, Vol. 68, nr 7-8, s. 485-492Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, an integrated artificial neural network (ANN) and multi-objective genetic algorithm (GA) are developed to optimize the resistance spot welding (RSW) of AZ61 magnesium alloy. Since the stability and strength of a welded joint are strongly dependent on the size of the nugget and the residual stresses created during the welding process, the main purpose of the optimization is to achieve the maximum size of the nugget and minimum tensile residual stress in the weld zone. It is identified that the electrical current, welding time, and electrode force are the main welding parameters affecting the weld quality. The experiments are carried out based on the full factorial design of experiments (DOE). In order to measure the residual stresses, an X-ray diffraction technique is used. Moreover, two separate ANNs are developed to predict the nugget size and the maximum tensile residual stress based on the welding parameters. The ANN is integrated with a multi-objective GA to find the optimum welding parameters. The findings show that the integrated optimization method presented in this study is effective and feasible for optimizing the RSW joints and process.

  • 15.
    Agca, Can
    et al.
    Univ Calif Davis, Peter A Rock Thermochem Lab, Davis, CA 95616 USA.;Oak Ridge Natl Lab, POB 2009, Oak Ridge, TN 37831 USA..
    Lindwall, Greta
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    McMurray, Jake W.
    Oak Ridge Natl Lab, POB 2009, Oak Ridge, TN 37831 USA..
    Neuefeind, Jorg C.
    Oak Ridge Natl Lab, POB 2009, Oak Ridge, TN 37831 USA..
    Liu, Zi-Kui
    Penn State Univ, Dept Mat Sci & Engn, University Pk, PA 16802 USA..
    Navrotsky, Alexandra
    Univ Calif Davis, Peter A Rock Thermochem Lab, Davis, CA 95616 USA.;Arizona State Univ, Ctr Mat Universe, Sch Mol Sci, Tempe, AZ 85287 USA..
    Experimental and computational studies of melting of the spinel phase in the Fe-Al-O ternary system2020Ingår i: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, Vol. 70, artikel-id 101798Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The melting behavior of spinel in the Fe-Al-O system at high temperatures (1500-1800 degrees C) was studied by a combination of experimental and computational investigations. Differential thermal analysis (DTA) at ultra-high temperatures coupled with cooling traces on CO2 laser-heated levitated samples provided melting temperatures and the heats of fusion of (Fe,Al)(3)O-4 spinel phases. The experimental results are in fair agreement with the predictions using a published CALPHAD description and areas for modeling improvement are identified. New insights into the melting of defect spinel are provided.

  • 16.
    Aghasibeig, Maniya
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Laser cladding of a featureless iron-based alloy2012Ingår i: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 209, s. 32-37Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Laser cladding experiments with powder injection technique were carried out to create coatings of Fe-8.1Cr6.4Mn-5.3Si-6.9Mo-3.6C alloy on AISI 1018 steel substrates using a diode laser. Analysis of the clad layers showed that an almost featureless structure was formed at different dilutions between 1% and 4%. The featureless phase with a high hardness of 1155 HV was characterized as a metastable solid solution of e phase. However, the featureless structure appeared to be very brittle with numerous cracks. After heat-treatment, it decomposed into a bainitic structure with a high hardness of 884 HV.

  • 17.
    Ahlin, Björn
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Gärdin, Marcus
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Automated Classification of Steel Samples: An investigation using Convolutional Neural Networks2017Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Automatiserad bildigenkänning har tidigare använts inom ståltillverkning för olika sorters analyser. Den här studiens syfte är att undersöka om bildigenkänningsprogram applicerat på Svepelektronmikroskopi (SEM) bilder kan klassificera två stålprover. Stålproven var av samma sort, med skillnaden att de behandlats med kalcium olika lång tid.

    För att möjliggöra den automatiserade bildigenkänningen byggdes ett Convolutional Neural Network (CNN). Nätverket byggdes med hjälp av öppen kod från Keras Documentation. Detta för att programmet enkelt skall kunna reproduceras. Nätverket tränades, validerades och testades, först för vanliga bilder och sedan för binariserade bilder. Binariserade bilder användes för att tvinga programmet att bara klassificera med avseende på inneslutningar och inte på grundmatrisen.

    Resultaten på klassificeringen för vanliga bilder gav en träffsäkerhet på 99.99%. För binariserade bilder blev träffsäkerheten för klassificeringen 67.9%. Resultaten visar att det är möjligt att använda CNNs för att klassificera stålprover. En intressant möjlighet som vidare studier på CNNs kan leda till är att automatisk klassificering av inneslutningar kan möjliggöras. 

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  • 18.
    Ahlin, Björn T. I.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Nitrogen Removal in a Vacuum Tank Degasser: An Investigation on the Nitrogen Removal Performance2019Självständigt arbete på avancerad nivå (masterexamen), 300 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Förändringar till följd av HYBRIT projektet kommer påverka SSAB Oxelösunds stålverk. Masugn och LD konverter skall ersättas med ljusbågsugns teknologi. Ett problem till följd av detta är kvävehalter i stålet. Enligt litteraturen är kvävehalterna betydligt högre i stål tappat från en ljusbågsugn. Med kvävehalter runt 60-70 ppm jämfört med stål tappat från en LD konverter som har kvävehalter kring 25 ppm. Därför krävdes en undersökning kring kvävereningpotentialen för SSAB Oxelösunds vakuum tank avgasare. Industriella experiment med minskad slaggmängd jämfört med standard praxis blev utförda. Detta utfördes med tanken att minskad slaggmängd skulle ge en större effektiv reaktionsarea. Intentionen var att utföra försök först med halverad slaggmängd följt av slaggfria försök. Dock, på grund av produktions praktiska problem vid verket blev försöken avbrutna. Som en följd av detta blev bara försök med halverad slaggmängd utförda och jämförda med processdata från standard praxis. Kvävereningsberäkningar på historisk processdata utfördes. En parameter som representerade genomsnittlig reaktionshastighet, vilken beror på den effektiva reaktionsarea blev erhållen, validerad och senare applicerad på ett hypotetiskt framtida scenario. Resultaten indikerar att minskad slaggmängd har en positiv inverkan på den effektiva reaktions arean och till följd av detta även en positiv inverkan på kväverening. Dock är för få försök utförda för att kunna fastställa detta. De slutsatser som dras är att vakuum anläggningen vid SSAB Oxelösund har möjligheten att, med förlängd vakuumbehandlingstid, rena de ökade kvävehalter till nivåer runt 20-30 ppm. Ytterligare slutsatser var att ytaktiva element, såsom syre och svavel, i stålet har en stor negativ påverkan för kväverening. Samt att den effektiva reaktionsarean är av stor betydelse för kväverening. Därför bör ansträngningar tas för att minska koncentrationen av ytaktiva element samt att försöka göra den effektiva reaktionsarean så stor som möjligt. Slutligen fastställdes det att ytterligare studier är nödvändiga för att öka kunskapen kring förebyggande tekniker och reningstekniker för kväveföroreningar i stål.

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  • 19.
    Ahmad, Yousef
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Oxidation of Graphite and Metallurgical Coke: A Numerical Study with an Experimental Approach2016Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    At the royal institute of technology (KTH) in the department of applied process metallurgy, a novel modelling approach has been developed which allows a dynamic coupling between the commercial thermodynamic software Thermo-Calc and the commercial computational fluid dynamic (CFD) software Ansys Fluent, only referred to as Fluent in the study. The dynamic coupling approach is used to provide numerical CFD-models with thermodynamic data for the thermo-physical properties and for the fluid-fluid chemical reactions occurring in metallurgical processes. The main assumption forthe dynamic coupling approach is the existence of local equilibrium in each computational cell. By assuming local equilibrium in each computational cell it is possible to use thermodynamic data from thermodynamic databases instead of kinetic data to numerically simulate chemical reactions. The dynamic coupling approach has been used by previous studies to numerically simulate chemical reactions in metallurgical processes with good results. In order to validate the dynamic coupling approach further, experimental data is required regarding surface reactions. In this study, a graphiteand metallurgical coke oxidation experimental setup was suggested in order to provide the needed experimental data. With the experimental data, the ability of the dynamic couplings approach to numerically predict the outcome of surface reactions can be tested.By reviewing the literature, the main experimental apparatus suggested for the oxidationexperiments was a thermo-gravimetric analyzer (TGA). The TGA can provide experimental data regarding the reaction rate, kinetic parameters and mass loss as a function of both temperature and time. An experimental setup and procedure were also suggested.In order to test the ability of Fluent to numerically predict the outcome of surface reactions, without any implementation of thermodynamic data from Thermo-Calc, a benchmarking has been conducted. Fluent is benchmarked against graphite oxidation experiments conducted by Kim and No from the Korean advanced institute of science and technology (KAIST). The experimental graphite oxidation rates were compared with the numerically calculated graphite oxidation rates obtained from Fluent. A good match between the experimental graphite oxidation rates and the numerically calculated graphite oxidation rates were obtained. A parameter study was also conducted in order to study the effect of mass diffusion, gas flow rate and the kinetic parameters on the numerically calculated graphite oxidation rate. The results of the parameter study were partially supported by previous graphite oxidation studies. Thus, Fluent proved to be a sufficient numerical tool for numerically predicting the outcome of surface reactions regarding graphite oxidation at zero burn-off degree.

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  • 20.
    Ahmed, Hesham M.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Investigations of the Kinetics of Reduction and Reduction/Carburization of NiO-WO3 Precursors.2010Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Kinetic studies of reduction of the mixtures of NiO and WO3 having different Ni/(Ni+W) molar ratios in flowing hydrogen gas were investigated by means of Thermo Gravimetric Analysis (TGA), Fluidized Bed (FB) technique as well as Thermal diffusivity measurements under isothermal conditions. In the case of TGA, the reaction progress was monitored by mass loss, while evolved gas analysis by a gas chromatograph was the indicator of the reaction progress in the case of FB. The results indicate that the reduction reaction proceeds through three consecutive steps, viz.

    NiO-WO3 Ni-WO3 Ni-WO2 Ni-W

    The present results show that the fluidized bed technique can be successfully utilized in bulk production of intermetallics containing W and a transition metal (or a composite material) wherein the process conditions would have a strong impact on the particle size of the end product.

    During the investigations, it was found that there was a delay in the reaction during the hydrogen reduction of NiO-WO3 mixed oxides in a fluidized bed reactor. In order to understand the same, a theoretical model was developed to estimate the apparent reaction rate constant for the reduction reaction from the intrinsic chemical reaction rate constant. Appropriate differential mass balance equations based on intrinsic chemical reaction rate constants and thermodynamic equilibria were developed. The proposed model was successfully applied in predicting the overall reaction kinetics of a fluidized bed reactor. This model is also suitable for scale-up calculations.

    SEM images showed that the particle size of the final product was dependent on the Ni/(Ni+W) molar ratio; smaller particles were formed at higher nickel contents. X-ray diffractions of the reduced precursors exhibited slight shift of Ni peaks from the standard one indicating the dissolution of W into Ni.

    A new method for studying kinetics of the hydrogen reduction of NiO-WO3 precursors was developed in which the reaction progress was monitored by following the change of thermal diffusivity of the precursors. Activation energies of reduction as well as sintering were calculated. This method is considered unique as it provides information regarding the physical changes like sintering, change of porosity and agglomeration along with the chemical changes occurring during the gas/solid reaction.

    As a continuation of the kinetic studies, Ni-W-C ternary carbides were synthesized by simultaneous reduction–carburization of Ni-W-O system using H2-CH4 gas mixtures by TGA. The results showed that the reduction of the oxide mixture was complete before the carburization took place. The nascent particles of the metals formed by reduction could react with the gas mixture with well-defined carbon potential to form a uniform product of Ni-W-C. The above-mentioned experiments were conducted in such a way to ensure that the reaction was controlled by the chemical reaction. The activation energies of the reduction as well as carburization processes at different stages were calculated accordingly.

    The present dissertation demonstrates the potential of the investigations of gas/solid reactions towards tailoring the process towards materials with optimized properties as for example introduction of interstitials. The present process design is extremely environment-friendly with reduced number of unit processes and the product being H2O.

  • 21.
    Ahmed, Hesham M.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    El-Geassy, Abdel-Hady A.
    Viswanathan, Nurni Neelakantan
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Kinetics and Mathematical Modeling of Hydrogen Reduction of NiO-WO(3) Precursors in Fluidized Bed Reactor2011Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 51, nr 9, s. 1383-1391Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the present work, Fluidized bed reduction of NiO-WO(3) precursors was investigated isothermally at temperatures 973-1 273 K. The reaction progress was monitored by analysis of H(2)O evolved during the reaction process using a gas chromatograph instrument. A theoretical model based on intrinsic chemical reaction rate constants and thermodynamic equilibria was developed to estimate the apparent reaction rate constant for the reduction reaction. In developing the model, the particles are considered to be in a completely mixed condition and gas flow is described as plug flow. The proposed model is also suitable for scale-up calculations. The interfacial chemical reaction model was found to fit the experimental results. The apparent activation energy values of the reduction process at different stages were calculated accordingly. The present investigation proved that the fluidized bed technique can be successfully utilized in bulk production of intermetallics containing W and a transition metal (or a composite material) wherein the process conditions would have a strong impact on the particle size of the end product.

  • 22.
    Ahmed, Hesham M.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Reduction-Carburization of NiO-WO3 Under Isothermal Conditions Using H2-CH4 Gas Mixture2010Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 41, nr 1, s. 173-181Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ni-W-C ternary carbides were synthesized by simultaneous reduction–carburization of NiO-WO3 oxide precursors using H2-CH4 gas mixtures in the temperature range of 973 to 1273 K. The kinetics of the gas–solid reaction were followed closely by monitoring the mass changes using the thermogravimetric method (TGA). As a thin bed of the precursors were used, each particle was in direct contact with the gas mixture. The results showed that the hydrogen reduction of the oxide mixture was complete before the carburization took place. The nascent particles of the metals formed by reduction could react with the gas mixture with well-defined carbon potential to form a uniform product of Ni-W-C. Consequently, the reaction rate could be conceived as being controlled by the chemical reaction. From the reaction rate, Arrhenius activation energies for reduction and carburization were evaluated. Characterization of the carbides produced was carried out using X-ray diffraction and a scanning electron microscope (SEM) combined with electron dispersion spectroscopy (SEM-EDS) analyses. The grain sizes also were determined. The process parameters, such as the temperature of the reduction–carburization reaction and the composition of the gas mixture, had a strong impact on the carbide composition as well as on the grain size. The results are discussed in light of the reduction kinetics of the oxides and the thermodynamic constraints.

  • 23. Ahmed, Hesham
    et al.
    Morales-Estrella, R.
    Viswanathan, Nurin
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Gas-Solid Reaction Route toward the Production of Intermetallics from Their Corresponding Oxide Mixtures2016Ingår i: Metals, ISSN 2075-4701, Vol. 6, nr 8, artikel-id 190Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Near-net shape forming of metallic components from metallic powders produced in situ from reduction of corresponding pure metal oxides has not been explored to a large extent. Such a process can be probably termed in short as the "Reduction-Sintering" process. This methodology can be especially effective in producing components containing refractory metals. Additionally, in situ production of metallic powder from complex oxides containing more than one metallic element may result in in situ alloying during reduction, possibly at lower temperatures. With this motivation, in situ reduction of complex oxides mixtures containing more than one metallic element has been investigated intensively over a period of years in the department of materials science, KTH, Sweden. This review highlights the most important features of that investigation. The investigation includes not only synthesis of intermetallics and refractory metals using the gas solid reaction route but also study the reaction kinetics and mechanism. Environmentally friendly gases like H-2, CH4 and N-2 were used for simultaneous reduction, carburization and nitridation, respectively. Different techniques have been utilized. A thermogravimetric analyzer was used to accurately control the process conditions and obtain reaction kinetics. The fluidized bed technique has been utilized to study the possibility of bulk production of intermetallics compared to milligrams in TGA. Carburization and nitridation of nascent formed intermetallics were successfully carried out. A novel method based on material thermal property was explored to track the reaction progress and estimate the reaction kinetics. This method implies the dynamic measure of thermal diffusivity using laser flash method. These efforts end up with a successful preparation of nanograined intermetallics like Fe-Mo and Ni-W. In addition, it ends up with simultaneous reduction and synthesis of Ni-WN and Ni-WC from their oxide mixtures in single step.

  • 24.
    Ahmed, N.
    et al.
    Khalifa Univ, Adv Digital & Addit Mfg Ctr, Abu Dhabi, U Arab Emirates..
    Barsoum, Imad
    KTH, Skolan för teknikvetenskap (SCI), Teknisk mekanik. Khalifa Univ, Adv Digital & Addit Mfg Ctr, Abu Dhabi, U Arab Emirates.;Khalifa Univ, Dept Mech Engn, Abu Dhabi, U Arab Emirates..
    Haidemenopoulos, G.
    Univ Thessaly, Dept Mech Engn, Volos, Greece..
    Abu Al-Rub, R. K.
    Khalifa Univ, Adv Digital & Addit Mfg Ctr, Abu Dhabi, U Arab Emirates.;Khalifa Univ, Dept Mech Engn, Abu Dhabi, U Arab Emirates..
    Process parameter selection and optimization of laser powder bed fusion for 316L stainless steel: A review2022Ingår i: JOURNAL OF MANUFACTURING PROCESSES, ISSN 1526-6125, Vol. 75, s. 415-434Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    Stainless steel 316L has been an extensively investigated metallic material for laser powder bed fusion (L-PBF) in the past few decades due to its high corrosion resistance. However, there are challenges related to producing LPBF parts with minimal defects, attaining mechanical properties comparable with traditional process and dependency on time consuming post process treatments. The selection of L-PBF process parameters is crucial to overcome these challenges. This paper reviews the research carried out on L-PBF process parameter optimization for fabrication of 316L steel components for maximizing part densifications and attaining desired microstructure morphologies in parts. A brief work on numerical simulation approach for process parameter optimization for high densifications is also included in this paper.

  • 25. Ai, S.
    et al.
    Long, M.
    Guo, W.
    Liu, P.
    Chen, D.
    Dong, Zhihua
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Zhang, Y.
    Duan, H.
    Ab Initio Study on Continuous Evolution of Mechanical Properties in Phase-Transition Region of Low-Carbon Steel2020Ingår i: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344XArtikel i tidskrift (Refereegranskat)
    Abstract [en]

    To control steel quality during continuous casting and subsequent heat treatment, an understanding of the evolution laws of mechanical properties during the austenite transition and the underlying mechanisms is of importance. Herein, the peak separation method is used to investigate the expansion behaviors in low-carbon steel. And the elastic properties of the matrix phase are calculated using the exact muffin-tin orbitals (EMTO) method. A continuous evolution model of high-temperature properties in the phase-transition region is established for ab initio data and experimental results. The evolution laws of the tetragonal shear elastic constant C′ and Young's modulus E agree well with that of the high-temperature strength. The critical temperature for ductility to brittleness is 850 °C. The matrix phase exhibits significantly brittleness character and increases slightly with decreasing temperature in single-phase paramagnetic (PM) γ-Fe region. The straightening zone temperature should be controlled above 950 °C to avoid cracks. In the austenite transition region, the drop rate of the magnetic moment reaches 18.90%. The findings suggest that the evolution law of mechanical properties of steels can be predicted from the elastic properties, especially during the austenite transition process, providing a basis for the prediction of material properties using ab initio methods. 

  • 26. Ai, S. -Y
    et al.
    Long, M. -J
    Zhang, M. -Y
    Chen, D. -F
    Liu, P.
    Dong, Zhihua
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Egenskaper.
    High-temperature strength of l245mb slab and elastic properties of iron matrix2019Ingår i: Kang T'ieh/Iron and Steel, ISSN 0449-749X, Vol. 54, nr 8, s. 194-201Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    It‘s important to understand the evolution of high-temperature properties of slabs from the microscopic structure and the macroscopic structure, which is of great significance to the performance and quality control of slabs. The variation of the high-temperature strength of the L245MB slab with the temperature was measured by the hot tensile test technique with the Gleeble system. For the Fe matrix phase, which was under different crystal structures and magnetic states, the EMTO first-principles method was used to calculate the bulk modulus B, the single-crystal elastic constants c’ and c44, the polymorphic Young's modulus E, and the evolution of the system magnetic moment μ with temperature. The results showed that the cooling rate had little effect on the high-temperature strength evolution of the slab. The high-temperature strength took a transition near Ae3 and TC temperature, with a "platform" presented, where the average evolution rate of tensile strength was 0.008 Mpa/℃ and the yield strength was 0.076 Mpa/℃. The thermoplasticity of the slab had a different degree of decline in the temperature range of TC~Ae3, and the reduction of the area was the smallest at about 800℃, which was 59.02%~62.79%. The temperature range of ductility trough increased with the cooling rate increasing, and the surface temperature of the straightening zone should be controlled above 850 ℃ to avoid the crack generation. The elastic properties of the Fe matrix phase changed with the change of the magnetic state and the crystal structure. The transformation of the magnetic state had a greater influence on c’, c44, E, and the transformation of the crystal structure had a greater influence on B. During the transformation of FM to PM, c’ and E decreased by 64.09% and 10.33%, c44 increased by 57.82%, and B decreased by 34.38% with the change of bcc to fcc structure. The relationship between the evolution of single crystal elastic constant c’, polycrystalline Young's modulus E and the high-temperature strength of the slab were analyzed. It provides an idea for analyzing the macroscopic performance of the slab from the microstructural parameters of the crystal structure, which is a basis for the research and application of the first principles method in the high-temperature mechanical properties of steel materials. 

  • 27.
    Ai, Songyuan
    et al.
    Chongqing Univ, Coll Mat Sci & Engn, State Key Lab Coal Mine Disaster Dynam & Control, Chongqing 400044, Peoples R China.;Chongqing Univ, Chongqing Key Lab Vanadium Titanium Met & New Mat, Chongqing 400044, Peoples R China..
    Long, Mujun
    Chongqing Univ, Coll Mat Sci & Engn, State Key Lab Coal Mine Disaster Dynam & Control, Chongqing 400044, Peoples R China.;Chongqing Univ, Chongqing Key Lab Vanadium Titanium Met & New Mat, Chongqing 400044, Peoples R China..
    Zhang, Siyuan
    Chongqing Univ, Coll Mat Sci & Engn, State Key Lab Coal Mine Disaster Dynam & Control, Chongqing 400044, Peoples R China.;Chongqing Univ, Chongqing Key Lab Vanadium Titanium Met & New Mat, Chongqing 400044, Peoples R China..
    Chen, Dengfu
    Chongqing Univ, Coll Mat Sci & Engn, State Key Lab Coal Mine Disaster Dynam & Control, Chongqing 400044, Peoples R China.;Chongqing Univ, Chongqing Key Lab Vanadium Titanium Met & New Mat, Chongqing 400044, Peoples R China..
    Dong, Zhihua
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Liu, Peng
    Chongqing Univ, Coll Mat Sci & Engn, State Key Lab Coal Mine Disaster Dynam & Control, Chongqing 400044, Peoples R China.;Chongqing Univ, Chongqing Key Lab Vanadium Titanium Met & New Mat, Chongqing 400044, Peoples R China..
    Zhang, Yanming
    Chongqing Univ, Coll Mat Sci & Engn, State Key Lab Coal Mine Disaster Dynam & Control, Chongqing 400044, Peoples R China.;Chongqing Univ, Chongqing Key Lab Vanadium Titanium Met & New Mat, Chongqing 400044, Peoples R China..
    Duan, Huamei
    Chongqing Univ, Coll Mat Sci & Engn, State Key Lab Coal Mine Disaster Dynam & Control, Chongqing 400044, Peoples R China.;Chongqing Univ, Chongqing Key Lab Vanadium Titanium Met & New Mat, Chongqing 400044, Peoples R China..
    Ab Initio Calculations on Elastic Properties of IF Steel Matrix Phase at High Temperature Based on Lattice Expansion Theory2020Ingår i: Metals, ISSN 2075-4701, Vol. 10, nr 2, artikel-id 283Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Elucidating the evolution law of the elastic properties of the matrix phase is of great significance for the control of steel properties and quality during continuous casting and subsequent heat treatment. In this paper, thermal expansion experiments and ab initio calculations are used to study the elastic properties of the interstitial free (IF) steel matrix phase in different magnetic states and crystal structures. The results show that the bulk modulus B and the tetragonal shear elastic constant C' for the entire temperature range decrease with increasing temperature, but C-44 is the opposite. While from paramagnetic (PM) to ferromagnetic (FM) state, C'(C-44) have changed similar to 188% (similar to 27%), B increases by similar to 55% during the crystal structure change (fcc -> bcc). With the FM to PM state, the Zener anisotropy parameter increases sharply, and Young's modulus decreases significantly in the [001] direction; the maximum difference is similar to 76 GPa. The evolution rate of average Young's modulus in single bcc-phase FM (fcc-phase PM) range reaches similar to 5.5(similar to 5.6) x 10(-2) GPa K-1. The research provides an effective method for ab initio calculation of the elastic properties of interstitial free and ultra-low carbon steels at high temperature, also furnishing a basis for the application of ab initio calculations to the high temperature performance of steel materials.

  • 28.
    Akbarnejad, Shahin
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Experimental and Mathematical Study of Incompressible Fluid Flow through Ceramic Foam Filters2016Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Ceramic Foam Filters (CFFs) are widely used to filter solid particles and inclusions from molten metal in metal production, particularly in the aluminum industry. In general, the molten metal is poured on the top of a ceramic foam filter until it reaches a certain height, also known as metal head or gravity head. This is done to build the required pressure to prime the filter media and to initiate filtration. To predict the required metal head, it is necessary to obtain the Darcy and non-Darcy permeability coefficients of the filter. The coefficients vary upon filter type. Here, it is common to classify CFFs based on grades or pore per inches (PPI). These CFFs range from10 to100 PPI and their properties vary in everything from cell and window size to strut size. The 80-100 PPI CFFs are generally not practical for use by industry, since the priming of the filters by a gravitational force requires an excessive metal head. However, recently a new method has been developed to prime such filters by using electromagnetic Lorentz forces. This allows the filters to be primed at a low metal head.

    To continue the research work, it was deemed necessary to measure the pressure gradients of single and stack of commercial alumina ceramic foam filters and to obtain the permeability characteristics. Therefore, efforts have been made to validate the previously obtained results, to improve the permeametry experimental setup, and to obtain Darcy and non-Darcy permeability coefficients of single 30, 50, and 80 PPI filters and stacks of filters. Furthermore, the experimentally obtained pressure gradients were analyzed and compered to the mathematically and analytically estimated pressure gradients.

    The studies showed that, in permeametry experiments, the sample sealing procedure plays an important role for an accurate estimation of the permeability constants. An inadequate sealing or an un-sealed sample results in an underestimation of the pressure drop, which causes a considerable error in the obtained Darcy and non-Darcy permeability coefficients. Meanwhile, the results from the single filter experiments showed that the permeability values of the similar PPI filters are not identical. However, the stacks of three identical filters gave substantially the same measured pressure drop values and roughly the same Darcy and non-Darcy coefficients as for the single filters.

    The permeability coefficients of the filters are believed to be best defined and calculated by using the Forchheimer equation. The well-known and widely used Ergun and Dietrich equations cannot correctly predict the pressure drop unless a correction factor is introduced. The accuracy of the mathematically estimated pressure drop, using COMSOL Multiphysics® 5.1, found to be dependent on the drag term used in the Brinkman-Forchheimer equation.  Unacceptable error, as high as 84 to 89 percent for the 30, 50 and 80 PPI single filters, compared to the experimentally obtained pressure gradient values were observed when the literature defined Brinkman-Forchheimer drag term was used. However, when the same second order drag term (containing the non-Darcy coefficient) as defined in the Forchheimer equation was used, the predicted pressure gradient profiles satisfactorily agreed with the experiment data with as little as 0.3 to 5.5 percent deviations for the 30, 50 and 80 PPI single filters.

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    Thesis
  • 29.
    Akbarnejad, Shahin
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Processer.
    Mathematical and Experimental Study on Filtration of Solid Inclusions from Molten Aluminium and Steel2023Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Aluminium och stål har varit den mest producerade metallen respektive legeringen under många år. Deras omfattande användning i olika industrier, deras grundläggande roll i vårt vardagliga liv och deras utmärkta återvinningsegenskaper utgör de stora drivkrafterna för utvecklingen av en produktion mot mer hållbara processer. En framgångsrik integrering och tillämpning av smält metallfiltrering från oönskade inneslutningar i produktionsprocesser kan resultera i minskningar av skrot och omarbetning samt skulle ge en renare smält metall som kan leda till en produktion av metalliska material med förbättrade mekaniska egenskaper. Filtrering av aluminiumsmältor med keramiska skumfilter utgör en etablerad process inom aluminiumindustrin. Keramiska filter används också i stålgjuterier för att avlägsna inneslutningar från smältan före gjutning i en form. Användningen av keramiska filter är dock antingen begränsad till specifika typer av legeringar eller gjutgods eller till specifika filter med stora porer och öppningar. Som ett resultat av detta har användningen av keramiska filter i stålindustrin begränsningar när det gäller att fånga upp inneslutningar, där specifikt små inneslutningar inte kan fångas upp.

     Detta forskningsarbete syftar till att bidra till det globala arbetet med att utveckla processerna för tillverkning av smält metall för att bli mer hållbara och för att höja kvaliteten på slutprodukten. För att vara specifik syftar det till att sprida mer ljus gällande filtreringsapplikationer och användningen av keramiska filter för att avlägsna fasta icke-metalliska inneslutningar från smält aluminium och stål. Således bestämdes permeabilitetsegenskaper för enkla 30, 50 och 80 porer per tum (PPI) aluminiumoxid keramiska skumfilter (CFF) kvaliteter såväl som staplar av tre 30, tre 50 och tre 80 PPI aluminiumoxid CFF-kvaliteter baserat på experimentella och numeriska studier. Detta ger den information som behövs för att uppskatta det tryck som krävs för att grunda och/eller trycka det smälta aluminiumet genom filtren. Trycket kan antingen byggas upp av gravitationskrafter eller andra krafter. Det har nyligen visat sig att det är möjligt att grunda sådana filter med elektromagnetiska krafter och filtrera fasta inneslutningar från smält aluminium. Slutligen undersöktes och studerades fysisk raffinering av smält stål från fasta aluminiumoxidinneslutningar genom användande av ett monolitiskt extruderat fyrkantscelligt aluminiumoxidkeramiskt filter med en utvecklad matematisk Computational Fluid Dynamics (CFD) modell samt partikelbanorna för inneslutningar i storleksintervallet 1 till 100 [um].

     De experimentellt erhållna permeabilitetsegenskaperna såväl som de erhållna tryckgradientprofilerna för de enskilda 30, 50 och 80 PPI CFF:erna jämfördes med tidigare forskningsresultat från litteraturen. Överlag så var överensstämmelse mellan nuvarande och tidigare resultat god. Det visade sig också att det var viktigt att vätskan inte tog genvägar under permeabilitetsexperiment för att inte erhålla avvikelser så höga som 60 %. Det visade sig också att liknande permeabilitetsegenskaper för de staplade filtren som för de enskilda filtren kunde uppnås. Ett ungefär tre gånger högre tryckgradient eller tryck måste dock appliceras när man använder en stapel med tre identiska PPI-filter jämfört när enstaka filter används. De numeriska simuleringarna validerade också de experimentella resultaten från permeabilitetsexperimenten.

     CFD-simuleringarna och partikelbanorna för de fasta aluminiumoxidinneslutningarna i smält stål genom det monolitiska aluminiumoxidfiltret visade att det var möjligt att fånga upp alla partiklar större än 50 [µm]. Det var dock inte möjligt att fånga upp alla partiklar mindre än 50 [µm] på grund av den användande simuleringsmetoden samt de nuvarande simuleringsbegränsningar i programvaran.

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    fulltext
  • 30.
    Akbarnejad, Shahin
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Jonsson, Lage Tord Ingemar
    Kennedy, Mark William
    Aune, Ragnhild Elizabeth
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Analysis on Experimental Investigation and Mathematical Modeling of Incompressible Flow Through Ceramic Foam Filters2016Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 47, nr 4, s. 2229-2243Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents experimental results of pressure drop measurements on 30, 50, and 80 pores per inch (PPI) commercial alumina ceramic foam filters (CFF) and compares the obtained pressure drop profiles to numerically modeled values. In addition, it is aimed at investigating the adequacy of the mathematical correlations used in the analytical and the computational fluid dynamics (CFD) simulations. It is shown that the widely used correlations for predicting pressure drop in porous media continuously under-predict the experimentally obtained pressure drop profiles. For analytical predictions, the negative deviations from the experimentally obtained pressure drop using the unmodified Ergun and Dietrich equations could be as high as 95 and 74 pct, respectively. For the CFD predictions, the deviation to experimental results is in the range of 84.3 to 88.5 pct depending on filter PPI. Better results can be achieved by applying the Forchheimer second-order drag term instead of the Brinkman-Forchheimer drag term. Thus, the final deviation of the CFD model estimates lie in the range of 0.3 to 5.5 pct compared to the measured values.

  • 31.
    Akbarnejad, Shahin
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Saffari Pour, Mohsen
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Jonsson, Lage Tord Ingemar
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Jönsson, Pӓr Göran
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Effect of Fluid Bypassing on the Experimentally Obtained Darcy and Non-Darcy Permeability Parameters of Ceramic Foam Filters2017Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 48, nr 1, s. 197-207Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ceramic foam filters (CFFs) are used to remove solid particles and inclusions from molten metal. In general, molten metal which is poured on the top of a CFF needs to reach a certain height to build the required pressure (metal head) to prime the filter. To estimate the required metal head, it is necessary to obtain permeability coefficients using permeametry experiments. It has been mentioned in the literature that to avoid fluid bypassing, during permeametry, samples need to be sealed. However, the effect of fluid bypassing on the experimentally obtained pressure gradients seems not to be explored. Therefore, in this research, the focus was on studying the effect of fluid bypassing on the experimentally obtained pressure gradients as well as the empirically obtained Darcy and non-Darcy permeability coefficients. Specifically, the aim of the research was to investigate the effect of fluid bypassing on the liquid permeability of 30, 50, and 80 pores per inch (PPI) commercial alumina CFFs. In addition, the experimental data were compared to the numerically modeled findings. Both studies showed that no sealing results in extremely poor estimates of the pressure gradients and Darcy and non-Darcy permeability coefficients for all studied filters. The average deviations between the pressure gradients of the sealed and unsealed 30, 50, and 80 PPI samples were calculated to be 57.2, 56.8, and 61.3 pct. The deviations between the Darcy coefficients of the sealed and unsealed 30, 50, and 80 PPI samples found to be 9, 20, and 31 pct. The deviations between the non-Darcy coefficients of the sealed and unsealed 30, 50, and 80 PPI samples were calculated to be 59, 58, and 63 pct.

  • 32.
    Akbarnejad, Shahin
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Sheng, Dong-yuan
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Processer.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Processer.
    A Computational Fluid Dynamics Study on Physical Refining of Steel Melts by Filtration2023Ingår i: Metals, ISSN 2075-4701, Vol. 13, nr 6, artikel-id 1022Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, a previous experimental investigation on physical refining of steel melts by filtration was numerically studied. To be specific, the filtration of non-metallic alumina inclusions, in the size range of 1-100 & mu;m, was stimulated from steel melt using a square-celled monolithic alumina filter. Computational fluid dynamics (CFD) studies, including simulations of both fluid flow and particle tracing using the one-way coupling method, were conducted. The CFD predicted results for particles in the size range of & LE;5 & mu;m were compared to the published experimental data. The modeled filtration setup could capture 100% of the particles larger than 50 & mu;m. The percentage of the filtered particles decreased from 98% to 0% in the particle size range from 50 & mu;m to 1 & mu;m.

  • 33.
    Akbarnejad, Shahin
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Processer.
    Sheng, Dongyuan
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Processer.
    Jönsson, Pär Göran
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Processer.
    A Computational Fluid Dynamics Study on Physical Refining of Steel Melts by FiltrationManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    In this paper, a previous experimental investigation on physical refining of steel melts by filtration was numerically studied. To be specific, filtration of non-metallic alumina inclusions, in the size range of 1 to 100 [μm], from steel melt by using a square-celled monolithic alumina filter was simulated. Computational fluid dynamics (CFD) studies, including simulations of both fluid flow and particle tracing using one-way coupling method, were conducted. The CFD predicted results for particles in the size range  5 [μm] were compared to the published experimental data. The modelled filtration setup could capture 100 % of the particles larger than 50 [μm]. The percentage of the filtered particles decreases from 98% to 0% in the particle size range of 50 [μm] to 1[μm].

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    fulltext
  • 34.
    Akbarnejad, Shahin
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Tilliander, Anders
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Processer.
    Sheng, Dongyuan
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Processer.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Processer.
    Effect of Batch Dissimilarity on Permeability of Stacked Ceramic Foam Filters and Incompressible Fluid Flow: Experimental and Numerical Investigation2022Ingår i: Metals, ISSN 2075-4701, Vol. 12, nr 6, s. 1001-, artikel-id 1001Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ceramic foam filters (CFFs) are used to remove inclusions and/or solid particles from molten metal. In general, the molten metal poured on the top of a CFF should reach a certain height to form the pressure (metal head) required to prime the filter. For estimating the required metal head and obtaining the permeability coefficients of the CFFs, permeability experiments are essential. Recently, electromagnetic priming and filtration of molten aluminum with low and high grades of CFF, i.e., 30, 50 and 80 pore per inch (PPI) CFFs, have been introduced. Since then, there has been interest in exploring the possibility of obtaining further inclusion entrapment and aluminum refinement by using electromagnetic force to prime and filter with stacked CFFs. The successful execution of such trials requires a profound understanding concerning the permeability parameters of the stacked filters. Such data were deemed not to exist prior to this study. As a result, this study presents experimental findings of permeability measurements for stacks of three 30, three 50 and three 80 PPI commercial alumina CFFs from different industrial batches and compares the findings to numerically modelled data as well as previous research works. Both experimental and numerical findings showed a good agreement with previous results. The deviation between the experimentally and numerically obtained data lies in the range of 0.4 to 6.3%.

  • 35. Alam, Minhaj M
    et al.
    Barsoum, Zuheir
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Lättkonstruktioner.
    Häggblad, Hans Åke
    Jonsén, Pär
    Kaplan, Alexander
    The Effects of Surface Topography and Lack of Fusion on The Fatigue Strength of Laser Hybrid Welds2009Ingår i: Congress proceedings: ICALEO, 28th International Congress on Applications of Lasers & Electro-Optics, 2009, s. 38-46Konferensbidrag (Refereegranskat)
    Abstract [en]

    The geometrical aspects of laser hybrid welds (before, during and after the process) differ from autonomous laser welding and from arc welding. When studying the fatigue behaviour of laser hybrid welded fillet joints we identified that the micro-topography (i.e. the surface ripples) can be more important than the macrogeometry of the weld surface or lack of fusion (LOF), which frequently was detected. The plastic replica method was applied to measure the toe radii at the weld edges while the micro-topography was identified by interferometric profilometry. From metallurgical analysis of the joint interface, the tendency to LOF can be explained. Stress analysis was carried out by Finite element analysis (FEA) for the complex joint geometry and a bending load situation, showing maximum stress on the weld toes, even when including LOF. It was shown that the position and value of the maximum stress depends on a non-trivial combination of the weld geometry, including possible LOF, and the surface micro-topography. Thus it can be explained that at compressive stress conditions LOF does not contribute significantly to the fatigue strength of laser hybrid welds while the surface topography does. Recommendations for defining and in turn avoiding critical geometrical aspects during the welding process are discussed.

  • 36.
    Albertsson, Galina
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Abatement of Chromium Emissions from Steelmaking Slags - Cr Stabilization by Phase Separation2013Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Chromium is an important alloying element in stainless steel but also environmentally harmful element. A number of mineralogical phases present in the slag matrix can contain chromium and lead to chromium leaching. Chromium in slag if not stabilized, could oxidize to the cancerogenic hexavalent state, and leach out if exposed to acidic and oxygen rich environment. Other environmental concerns are slag dusting and chromium escape to the atmosphere. Despite the fact that there is a certain risk of Cr-emission from slags at operating conditions, still very little is known regarding the emission of the oxides of chromium during the slag tapping. Spinel phase is known to be important for controlling the leaching properties of chromium from the slag. The objective of the present study was to get an understanding of the phase relationships and chromium partition in the chromium-containing industrial slags and synthetic slags with a view to control the chromium stabilization in spinel phase. The impact of slag basicity, heat treatment, oxygen partial pressure and Al2O3 addition, on the phase relationships and chromium partition has been determined. The experimental results were compared with the phase equilibrium calculations. It was found that the oxygen partial pressure in the gas phase had a strong impact on chromium partition. The experimental results show that the impact of the slag basicity on chromium partition at lower oxygen partial pressures was negligible in contrast to that in air. The amount of spinel phase was found to increase with increased Al2O3 content. Slow cooling of slag and soaking at low oxygen partial pressure would improve the spinel phase precipitation. This treatment will also lead to less Cr dissolved in the unstable matrix phases. Chromium oxide was found to be emitted when chromium containing slags were exposed to oxidizing atmosphere. The results indicate that chromium oxide evaporation increases with increase in temperature and oxygen partial pressure, but decreases with slag basicity and sample thickness.

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    Abatement of Chromium Emissions
  • 37.
    Albertsson, Galina
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Mikro-modellering.
    Effect of the presence of a dispersed phase (solid particles, gas bubbles) on the viscosity of slag2009Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The viscosities of a set of silicone oils containing different size ranges of charcoal or paraffin particles as well as the viscosities of silicone oil foams were measured at room temperature in order to determine the effect of dispersed phase on the viscosity of a liquid and its effect on foaming ability. The effective viscosity of the samples increased with volume fraction of the second phase. The foaming ability was improved by the presence of the particles. The improved foaming effect was for the most part not a result of the increased viscosity. No connection between the particle size and the effective viscosity could be determined. On the other hand particle morphology and the particle size distribution had effect on the effective viscosity. The viscosity data were compared with a number of existing equations for the estimation of effective viscosity. Einstein-Roscoe equation is suitable for two-phase mixtures containing globular particles with narrow particle size distribution and low interfacial tension. New mathematical models are required for effective viscosity prediction, where the suspending phase viscosity, effect of the interfacial tension, as well as the particle morphology should be taken in consideration.

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    fulltext
  • 38.
    Albertsson, Galina
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Teng, Lidong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Björkman, Bo
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Engström, Fredrik
    Effect of Low Oxygen Partial Pressure on the Chromium Partition in CaO-MgO-SiO2-Cr2O3-Al2O3 Synthetic Slag at Elevated Temperatures2013Ingår i: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 84, nr 7, s. 670-679Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The objective of the present work is to get an understanding of the impact of Al2O3 addition on the phase relationships in the CaO-MgO-Al2O3-SiO2-Cr2O3 slags at low oxygen partial pressures (P-O2 = 10(-4) Pa), with a view to control the precipitation of Cr-spinel in the slag. The equilibrium phases in CaO-MgO-Al2O3-SiO2-Cr2O3 slag system in the range on 1673-1873 K have been investigated. The compositions close to the industrial slag systems were chosen. The Cr2O3 content was fixed at 6 wt% and MgO at 8 wt%. Al2O3 contents in the slag were varied in the range of 3-12 wt%. The basicity (CaO/SiO2) of slag was set to 1.6. Gas/slag equilibrium technique was adopted. The samples were heated to 1873 K and soaked at this temperature for 24 h. The samples were then slow cooled to 1673 K and equilibrated for an additional 24 h. The oxygen partial pressure was kept at 10(-4) Pa. A gas mixture of CO/CO2 was used to control the oxygen partial pressure. After the equilibration, the samples were quenched in water. The chromium distribution and phase compositions in the quenched slags were studied using SEM-WDS and XRD techniques. The results were compared with the phase equilibrium calculations obtained from FACTSAGE software and the samples equilibrated in air. The size of spinel crystals increased drastically after slow cooling followed by annealing compared to samples being quenched after soaking at 1873 K. It was also found that low oxygen partial pressure had a strong impact on chromium partition. The amount of spinel phase increases with increased Al2O3 content.

  • 39.
    Aldén, Rickard
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Metallurgical investigation in weldability of Aluminium Silicon coated boron steel with different coating thickness.2015Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Hot-pressed aluminium and silicon coated boron steel is used in the car industry where high tensile strength is of great importance, such as in the safety cage of a car where deformation has to be kept to a minimum in case of a collision. After hot-pressing the AlSi-boron steel shows excellent properties with high tensile strength, minimal spring back and also shows good protection against corrosion. A thickness of the AlSi coating of 150 [g/m2] for AlSi coated boron steel is typically used by the car industry today. However the coating thickness would be desirable to be minimized to 80 [g/m2]. Welding of this boron steel with 80 [g/m2]have shown difficulties; and it’s not clear why this occurs.

    In this report the metallurgical properties of the different coating layers will be investigated, simulations with Thermocalc module Dictra will be used, SEM/EDS will be used to characterize phases in coating layers and correlate to weldability. Resistance spot welding tests will also be performed where the welding parameters of pre-pulse, pulse time, time in between pulses and current will be varied to achieve desirable weld plug diameter without expulsion. Hardness testing in form of micro Vickers will executed. The Materials used will be USIBOR® 1500, AS80 with four different annealing times and one sample of AS150.

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    fulltext
  • 40.
    Alevanau, Aliaksandr
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Study of pyrolysis and gasification of biomass from the self-organization perspective2015Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    This thesis focuses on the analysis of kinetics of i) low-temperature pyrolysis of gaseous hydrocarbons, ii) high-temperature steam gasification of char of wood pellets (>700oC), iii) high temperature pyrolysis of straw pellets in an atmosphere of argon and steam, and iv) high temperature pyrolysis of slices of transversally cut wooden sticks. The results of the kinetic measurements in the high-temperature cases are approximated using a least-square based optimization software, which was specially developed to analyse kinetics prone for deviation from the Arrhenius law.In the thesis a general analysis of the researched materials and kinetics of their pyrolysis and gasification is presented from the self-organization perspective. The energy transfer phenomena in both the pyrolysis and gasification processes of biomass are discussed with an emphasis on an analysis of basic phenomena involving the self-organized dynamics on fractal structures in the chosen biomass samples.

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    Alevanau_Thesis
  • 41.
    Alexis, Jonas
    et al.
    Swerea-Mefos.
    Jonsson, Lage
    KTH, Tidigare Institutioner (före 2005), Tillämpad processmetallurgi.
    Jönsson, Pär
    KTH, Tidigare Institutioner (före 2005), Tillämpad processmetallurgi.
    Heat and fluid-flow models for stirring conditionsin ladle furnaces and their practical implications in secondary refiningoperations1997Ingår i: Clean Steel 5, Vol 1,  2-4 June 1997, Balatonszeplak,Hungary, Balatonszeplak, 1997, s. 49-58Konferensbidrag (Refereegranskat)
  • 42.
    Alexis, Jonas
    et al.
    Swerea-Mefos.
    Jönsson, Pär
    KTH, Tidigare Institutioner (före 2005), Tillämpad processmetallurgi.
    Jonsson, Lage
    KTH, Tidigare Institutioner (före 2005), Tillämpad processmetallurgi.
    A model of an induction-stirred ladle accounting for slag and surface deformation1999Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 39, nr 8, s. 772-778Artikel i tidskrift (Refereegranskat)
  • 43.
    Alexis, Jonas
    et al.
    Swerea-Mefos.
    Jönsson, Pär
    KTH, Tidigare Institutioner (före 2005), Metallurgi.
    Jonsson, Lage
    Heating and electromagnetic stirring in a ladle furnace – a simulationmodel2000Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 40, nr 11, s. 1098-1104Artikel i tidskrift (Refereegranskat)
    Abstract [en]

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

  • 44.
    Alfredsson, Bo
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    Linares Arregui, Irene
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    Hazar, Selcuk
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    Numerical analysis of plasticity effects on fatigue growth of a short crack in a bainitic high strength bearing steel2016Ingår i: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 92, s. 36-51Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Plasticity effects on fatigue growth were simulated for a physically short crack. The material description comprised the Drucker-Prager yield surface, non-associated flow rule and non-linear combined hardening. The simulated development of the growth limiting parameter agreed with the experimental crack behaviour with early rapid propagation followed by a transition to slow R-controlled growth. The crack was open to the tip without any crack face closure throughout all load cycles. Instead compressive residual stresses developed at the unloaded tip which supplied an explanation to the slow rate of the propagated short crack in this bainitic high strength bearing steel. The material's strength differential effect was the key difference explaining why compressive residual stresses instead of crack face closure was responsible for the short crack effect in this material.

  • 45.
    Ali, Yusra
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    The Steel Sampling Process: A Study on Direct Analysis Sampler Design and Process2020Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Noggrann provtagning av smält stål har en nära direkt relation till kvalitetskontrollen av slutprodukten inom stålindustrin. Provtagare för nedsänkning utvecklas för att samla stålprover under de olika metallbearbetningsstationerna. För att tillhandahålla en snabbare metod för att erhålla provernas sammansättning, används direkt analys (DA) nedsänkningsprovtagare i stålindustrin. Provtagare av DA-typ kan leverera en verifiering av stålkompositionen på mycket kortare tid än för en vanlig provtagningsanordning. Det kräver ingen form av ytberedning innan den analyseras genom att utnyttja OES-analys (optisk emission spektroskopi). Eftersom stålfyllningsprocessen och stelningsförloppet påverkar provernas homogenitet och platthet utgår det här examensarbetet på att genomföra en studie av stålprovtagningsprocessen med olika metoder.

    Computational fluid dynamics (CFD) simulering med ANSYS FLUENT av stålfyllningssekvens med avseende på olika vinklar och olika slaggskydd har genomförts. Målet var att hitta en optimal inloppsvinkel där flödesmönstret för det smälta stålet som kommer in i provtagarens inlopp är mindre turbulent. En efterföljande CFD-simulering utfördes i MAGMASOFT där visa parametrar justerades för att undersöka deras effekt på proverna. Ytterligare mikroskopisk analys av tillhandahållna prover har genomförts. Slutligen har OES-analys utförts på två olika prover med samma stålkvalitet och från samma batch. Ett prov genomgick ytfräsning, medan det andra förblev ofärdändrat.

    ANSYS FLUENT-resultaten visade att i fallet med metallslaggskyddet, simuleringen visade en ofullständig fyllnad av provtagaren. Därför var det inte möjligt att specificera en optimal inloppsvinkel vid aktuell status. Den mikroskopiska analysen visade varken kolsegregering eller synlig dendritisk struktur i de erhållna proverna. Koncentrationsvärdena från OES-analysen gällande det bearbetade provet var nära varandra inom varje gnista. När det gäller icke-bearbetat provet visade OES-analysen olika koncentrationer bland olika gnistor. Detta är troligtvis relaterat till ytans platthet. MAGMASOFT-resultaten visade att ett byte av formmaterial från aluminium till koppar inte har någon påverkan på stålfyllningsprocessen, men en betydande förändring i stelningsgraden. Ökande inloppsdiameter minskar stålets hastighet tillsammans med hålighetens krympvolym och stålpåfyllningstiden minskar med ökande smälttryck och inloppsdiameter. Slutligen ger de framtida föreslagen en stor kunskap om att bestämma de exakta parametrarna som kan leda till specifika dimensioner för DA provtagare.

  • 46. Alirezaei, Mohammadamin
    et al.
    Doostmohammadi, Hamid
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Microstructure evolution in cast and equilibrium heat-treated CuZn30-(Si) alloys2016Ingår i: International Journal of Cast Metals Research, ISSN 1364-0461, E-ISSN 1743-1336, Vol. 29, nr 4, s. 222-227Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The main object of this work was to investigate the effect of Si addition and heat treatment on the microstructure of CuZn30 alloy. The alloys were prepared by casting and then the chemical composition, microstructure and phases were determined by optical and scanning electron microscope and XRD analysis. The resulting microstructures contained two phases, alpha and beta', with volume fraction depending on silicon content. Increments of Si content led to the formation of a Widmanstatten structure. It was also found that the silicon dissolved completely in alpha + beta phases and the lattice parameters of both alpha- and beta'-phases increased as the Si content increased. Hardness tests showed that hardness of both the as-cast and heat-treated samples increased as the Si content increased, and a significant increment of hardness in heat-treated alloy was due to the formation of a martensite phase.

  • 47.
    Allertz, Carl
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Mikro-modellering.
    Sulfur and nitrogen in ladle slag2016Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The present work deals with some aspects of slags related to secondary metallurgy in the steelmaking process. More specifically the focus is given to sulfur and nitrogen in ladle slags. Even though slags have been fairly well-researched in the past, the available data for these elements in typical ladle slag compositions is rather scarce. In some cases the available data is in discordance. There are also inconsistencies between the literature data and what is commonly observed in the industrial processes.

    Sulfide capacities were measured at steelmaking temperatures, 1823–1873 K, in ladle slags. The data was found to be in reasonable agreement with the industrial process norms. The sulfide capacity was found to increase with the basic oxides CaO and MgO; and decrease with the acidic components Al2O3 and SiO2. The sulfide capacity was also found to increase with temperature.

    The dependence of sulfide capacity on the oxygen partial pressure, for slags containing multivalent elements, was investigated experimentally at 1873 K with a slag containing vanadium oxide. A strong dependence of oxygen partial pressure was observed. The sulfide capacity increase by more than two orders of magnitude when the oxygen partial pressure was increased from 4.6×10-16 atm to 9.7×10-10 atm.

    The nitrogen solubility and the effect of carbon was investigated in typical ladle slags and the CaO–MgO–SiO2 system at 1873 K. Carbon increases the nitrogen solubility substantially. In the absence of carbon, the nitrogen solubility is extremely low. Low concentrations of cyanide was detected in the carbon saturated slag. This was much lower than the total nitrogen content and formation of cyanide cannot explain the large increase.

    The possibility of removing sulfur with oxidation from used ladle slag was investigated experimentally at 1373–1673 K. The sulfur removal of mostly solid slag was found to be a slow process, and would not suitable for industrial practice. At 1673 K the slag was mostly liquid and more than 85% of the sulfur was removed after 60 min of oxidation in pure oxygen atmosphere.

     

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    Thesis
  • 48.
    Allertz, Carl
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Mikro-modellering.
    Du, Sichen
    Possibility of Sulfur Removal from Ladle Slag by Oxidation in the Temperature Range 1373-1673 K2015Ingår i: Journal of Sustainable Metallurgy, ISSN 2199-3823, Vol. 1, nr 3, s. 229-239Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Experiments were conducted to investigate the possibility of removing sulfur from used ladle slag by oxidation. Slag samples (solid, two-phase mixture, and liquid with a small fraction of solid MgO particles) were subjected to an oxygen-rich atmosphere in the temperature range 1373–1673 K. The sulfur removal from the samples of solid and two-phase mixture was found to be a slow process due to the slow diffusion. The sulfur removal was found to have little dependence on temperature in the range 1373–1573 K. When the slag was mostly liquid (at 1673 K), the sulfur removal was significantly increased. More than 85 % of the sulfur could be removed after 60 min of oxidation in pure oxygen. An increase in oxygen partial pressure was found to increase the desulfurization slightly. Increasing the Al2O3 content in the slag decreased the degree of sulfur removal.

  • 49.
    Allertz, Carl
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Mikro-modellering.
    Du, Sichen
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Mikro-modellering.
    The Effect of Oxygen Potential on the Sulfide Capacity for Slags Containing Multivalent SpeciesManuskript (preprint) (Övrigt vetenskapligt)
  • 50.
    Allertz, Carl
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Mikro-modellering.
    Kojola, Niklas
    Hui, Wang
    Sichen, Du
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Mikro-modellering.
    A Study of Nitrogen Pickup from the Slag during Waiting Time of Ladle Treatment2014Ingår i: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 85, nr 4, s. 689-696Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An investigation of the nitrogen pickup of liquid steel from ladle slag after vacuum degassing was made. Nitride capacities, C-N, of a number of ladle slags were determined at controlled nitrogen and oxygen potentials at 1873K. The nitride capacities in the composition range studied were found to be very low. In accordance with the literature, the nitride capacity was found to increase with increasing SiO2 content. Industrial trials were performed. The nitrogen content of the steel was determined before and after vacuum degassing as well as after the waiting period. Three different trends of the variation of nitrogen content in the steel were observed. Both the laboratory study and the industrial trials revealed that the transfer of nitrogen from slag to steel was not the reason for nitrogen pickup in the steel subsequent to vacuum degassing.

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