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  • 201.
    Chen, Chao
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap. Taiyuan University of Technology, China; University of Science and Technology Beijing, China.
    Ni, Peiyuan
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Jonsson, L. T. I.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap. Swedish Defence Research Agency, Sweden.
    Tilliander, Anders
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Cheng, G.
    Jönsson, Pär G.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    A Model Study of Inclusions Deposition, Macroscopic Transport, and Dynamic Removal at Steel–Slag Interface for Different Tundish Designs2016Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 47, nr 3, s. 1916-1932Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents computational fluid dynamics (CFD) simulation results of inclusions macroscopic transport as well as dynamic removal in tundishes. A novel treatment was implemented using the deposition velocity calculated by a revised unified Eulerian deposition model to replace the widely used Stokes rising velocity in the boundary conditions for inclusions removal at the steel–slag interface in tundishes. In this study, the dynamic removal for different size groups of inclusions at different steel–slag interfaces (smooth or rough) with different absorption conditions at the interface (partially or fully absorbed) in two tundish designs was studied. The results showed that the dynamic removal ratios were higher for larger inclusions than for smaller inclusions. Besides, the dynamic removal ratio was higher for rough interfaces than for smooth interfaces. On the other hand, regarding the cases when inclusions are partially or fully absorbed at a smooth steel–slag interface, the removal ratio values are proportional to the absorption proportion of inclusions at the steel–slag interface. Furthermore, the removal of inclusions in two tundish designs, i.e., with and without a weir and a dam were compared. Specifically, the tundish with a weir and a dam exhibited a better performance with respect to the removal of bigger inclusions (radii of 5, 7, and 9 μm) than that of the case without weir and dam. That was found to be due to the strong paralleling flow near the middle part of the top surface. However, the tundish without weir and dam showed a higher removal ratio of smaller inclusions (radius of 1 μm). The reason could be the presence of a paralleling flow near the inlet zone, where the inclusions deposition velocities were much higher than in other parts.

  • 202.
    Chen, Chao
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi. State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing.
    Ni, Peiyuan
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jonsson, Lage
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi. FOI, Swedish Defence Research Agency, Division of CBRN Defence and Security.
    Tilliander, Anders
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Cheng, Guoguang
    State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Application of a Unified Eulerian Model to Study the Inclusions Deposition at a Steel-Slag Interface in a TundishManuskript (preprint) (Övrigt vetenskapligt)
  • 203. Chen, J.
    et al.
    Lindberg, F.
    Belova, Lyubov M.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Teknisk materialfysik.
    Forssgren, B.
    Gott, K.
    Lejon, J.
    Jasiulevicius, A.
    High resolution electron microscopy study on oxide films formed on nickel-base Alloys X-750, 182 and 82 in simulated high flow velocity BWR water conditions2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    This work contributes to characterization of the oxide films formed on nickel-base alloys (Alloy X-750, Alloy 82 and Alloy 182) under simulated BWR water environments at ∼10 or 18 m/s with or without iron injection. HR SEM/TEM and FIB techniques were applied. The oxide thicknesses on different alloys were substantially different, ranging from 50 nm to 8 μm. For Alloy X-750 and Alloy 182 exposed without iron injection, similar oxide phase compositions consisting of sub-micron Fe2O3 and NiFe 2O4 grains as well as NiO were formed but with substantially different microstructures. For the corroded Alloy X-750 there was an additional dense layer of possibly Ni1.5Cr0.5O 3 in between the NiFe2O4 and NiO layers. On Alloy 82 which contained a relatively low Fe-content only a thin but dense film of Cr1.3Fe0.7O3 was seen. With iron injection the oxide films formed on Alloy 82 were similar to that on the Alloy 182 without iron injection, suggesting that iron injection may play a similar role as if the alloy had an elevated iron content. The implication of the observations for material corrosion behavior in BWRs is elaborated.

  • 204. Chen, J.
    et al.
    Su, Z. -J
    Nakajima, Keiji
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    He, J. -C
    Criterion for dendrite fragmentation of steel under imposition of linear traveling EMS2011Ingår i: 2010 International Conference on Advances in Materials and Manufacturing Processes, ICAMMP 2010, 2011, s. 84-91Konferensbidrag (Refereegranskat)
    Abstract [en]

    In the fragmentation theory of T. Campanella et al, the local remelting of dendrite arms is induced by the solute-rich fluid flow. Based on this theory, the effects of linear EMS intensity and solute content on CET of steel are investigated. The conclusions are as follows: The criterion for dendrite fragmentation under linear EMS is derived based on dendrite fragmentation theory by T. Campanella et al. And the criterion is verified with steel experiments. It is valid for steel under the Linear EMS. Investigation is carried out on relation between critical volume fraction of solid and solute content at the time of dendrite fragmentation (CET occurrence). It is concluded that critical volume fraction of solid is small with low EMS intensity and it decreases with the increase of solute content (C, Mn). The reason is that it causes that flow in the mushy zone becomes small which leads to CET occurrence difficult.

  • 205. Chen, J.
    et al.
    Su, Z. -J
    Nakajima, Keiji
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    He, J. -C
    Critical conditions for dendrite fragmentation of low carbon steel in travelling electromagnetic field2010Ingår i: Dongbei Daxue Xuebao/Journal of Northeastern University, ISSN 1005-3026, Vol. 31, nr 12, s. 1717-1720+1732Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To investigate the effect of travelling electromagnetic field on dendrite fragmentation in solidification process, the 0.22 wt%~0.34 wt%C steel was tested for its solidifying behavior in travelling electromagnetic field. Observing the solidification structures of casting blanks under different magnetic flux density, the distributions of secondary dendrite arm spacing were investigated and the functional relationship between secondary dendrite arm spacing and cooling rate in solidification was discussed, as well as the effect of travelling electromagnetic field on the columnar-to-equiaxed transition (CET) position. The solidification rate and solid fraction when CET occurs were calculated. The critical conditions for dendrite fragmentation in travelling electromagnetic field is derived and verified by the testing results of low carbon steel. Thus, the relationship between the average velocity of the liquid-phase and the critical solid volume fraction when CET occurs was obtained.

  • 206.
    Chen, Kaixuan
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap. School of Material Science and Engineering, University of Science and Technology Beijing, Beijing, 100083, China.
    Pan, S.
    State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing, 100083, China.
    Chen, X.
    State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing, 100083, China.
    Wang, Z.
    School of Material Science and Engineering, University of Science and Technology Beijing, Beijing, 100083, China.
    Sandström, Rolf
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialteknologi.
    Optimisation of deformation properties in as-cast copper by microstructural engineering. Part II. Mechanical properties2020Ingår i: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 812, artikel-id 151910Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The microstructure evolution in the as-cast pure Cu and Cu-(1.0–3.0)Fe-0.5Co and Cu-1.5Fe-0.1Sn (wt. %) alloys was characterised in the previous work. Herein, the plastic deformation characteristics were examined by uniaxial tensile tests at room temperature. Along with the microstructure evolution, the yield strength increased with increasing Fe content and reached a peak value at 1.5 wt % Fe, but thereafter decreased with the further addition of Fe in the Cu–Fe–Co alloys. Nevertheless, the tensile strength and elongation synchronously improve with increasing Fe content. In particular, the Cu-1.5Fe-0.1Sn alloy achieved the optimal strength–ductility combination. In terms of the strengthening mechanism, the (Fe, Co)- or (Fe, Sn)-doped copper encouraged impediment, trapping, and storage of dislocations by the iron-rich nanoparticles and grain boundaries, which enhanced the strength and sustained the work hardening and elongation. The evolution of mechanical properties under an alloying effect was quantitatively described by the strengthening models. The results indicate that the optimum balance between strength and ductility was achieved by designing a microstructure containing fine grains, intragranular smaller spherical nanoparticles, and a minor solute element with higher misfit and higher growth restriction effect. The necessities for engineering a microstructure to achieve simultaneously strong and ductile bulk metals were discussed.

  • 207.
    Chen, Kaixuan
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap. University of Science and Technology Beijing, China.
    Pan, Shiwei
    Zhu, Yuzhi
    Cheng, Yongjian
    Chen, Xiaohua
    Wang, Zidong
    In situ observations of crack propagation in as-cast Cu-1.5Fe-0.5Co (wt%) alloy2017Ingår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 706, s. 211-216Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    As-cast Cu-1.5Fe-0.5Co (wt%) alloy displays both high tensile strength of 307 MPa and elongation of 33%. In situ transmission electron microscopy was used to investigate crack propagation in the alloy, to analyze the origin of the good properties. At different deformation stages in thin Cu foils, the interactions of a propagating crack with iron-rich nanoparticles and growth twins are investigated. Crack-bridging processes via near-tip twinned bridges were identified. The multiple deformation mechanisms act synergistically to contribute to high strength and high ductility in the alloy.

  • 208.
    Cheng, Yajuan
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Wang, Jing
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Jönsson, Pär Göran
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Zhao, Zhe
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Keramteknologi.
    Optimization of high-quality vertically aligned ZnO rod arrays by the response surface methodology2015Ingår i: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 626, s. 180-188Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Optimization of the deposition parameters was conducted by the response surface methodology to synthesize high-quality ZnO rod arrays with a high texture coefficient, a large aspect ratio and a narrow bandgap. In addition, mathematical models based on statistical analysis were also developed to predict the texture coefficient, aspect ratio and bandgap of the ZnO rod arrays. With the optimized parameters, all of the three involved responses obtained the desired optimum values. The results show that the texture coefficient can be elevated up to a value of 0.998, which represents an almost perfect value. Moreover, wide range of aspect ratios was obtained for various applications and the obtained maximum value of 21.3 is relatively high value by wet chemical method, especially when no capping agent and no refreshing growth solution in a nearly neutral solution is used.

  • 209.
    Christopher, Petersson
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnenergiteknik.
    Erosion-Corrosion experiments on Steels in liquid lead and Development of Slow Strain Rate testing rig2019Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
  • 210.
    Chychko, Andrei
    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.
    Foaming in Electric Arc Furnace: Part I: Laboratory Studies of Enthalpy changes of Carbonate Additions to Slag Melts2011Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 42, nr 1, s. 20-29Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the present work, a modified thermal analysis technique was used for studying the heat effect of slag foaming with carbonates addition. Experiments were conducted by sinking limestone and dolomite pieces of defined shapes (together with iron sinkers) in molten slag and monitoring the temperature changes accompanying the decomposition of carbonates. The heat effects of dolomite and limestone decompositions were determined at 1623 K (1350 A degrees C) and 1673 K (1400 A degrees C). It was found that the decomposition energy for dolomite and limestone for the studied slag composition is in the range of 56 to 79 pct of theoretical values, which is linked to the energy-saving effect of slag foaming. No influence of sample shape on decomposition energy was found for both limestone and dolomite.

  • 211.
    Chychko, Andrei
    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.
    Nzotta, M.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Fe2MoO4 as a precursor material for Mo alloying in steel: (Part II): Upscaling test2011Ingår i: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 82, nr 8, s. 886-897Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Mo yield when using three different alloying mixtures (MoO3 +C; MoO3 +C + FeOx; and MoO3+ C + CaO) was tested both in laboratory experiments (16 g and 0.5 kg scale) and industrial trials (3 ton scale). The alloying is based on in-situ formation of compounds of Mo in the mixtures from molybdenite concentrate with industrial grade Fe 2O3. Thermogravimetry (TGA) and X-ray diffraction (XRD) analyses were performed to identify the reduction steps and final products of the alloying mixtures. At least two steps of mass change were discovered during the reduction of all tested mixtures by carbon. The Mo yield for MoO3 + C mixture is 93% which was confirmed by both laboratory and industrial experiments. The Mo yield for MoO3 + C + CaO mixture is around 92% during 16 g scale laboratory and 3 ton scale industrial tests. The best results were obtained in the case of the mixture which contained FeOx, MoO3 and C, resulting in the Mo yield up to 98% at all the experiment scale levels. It was found that the combination of both lower evaporation and fast reduction by carbon of the mixture along with further dissolution in steel are necessary to provide high Mo yield during steel alloying. The calculated mass balance of 3 ton trial heats showed that only a small part of initial Mo amount (8-13 ppm) has gone into slag. Copyright

  • 212.
    Chychko, Andrei
    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.
    Nzotta, M.
    Seetharaman, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Synthesis and characterization of Fe2MoO4 as a precursor material for Mo alloying in steel2011Ingår i: Steel Research International, ISSN 1611-3683, Vol. 82, nr 3, s. 269-276Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Iron molybdate (Fe2MoO4) has been studied as a new potential precursor for Mo additions in high alloy steel processing. Fe2MoO4 was synthesized by high temperature reactions between MoO3, FeOx and carbon by holding the mixture first for 23 hours at 873K and then for 16 hours at 1373 K. The Fe2MoO4 syntheses were carried out with pure reagents as well as commercial grade materials supplied by steel industry. A thermodynamic analysis of the stabilities of the various phases in the Fe-Mo-O-C quaternary was carried out. The synthesis processes, leading to the Fe2MoO4 formation from the precursors and further reduction by carbon were studied with the aid of thermogravimetric analysis (TGA), high-temperature X-ray diffraction (HT-XRD) and evolved gas analysis by gas chromatography (GC). The maximum temperature in the case of all the experiments was 1373 K. It was found that the reactions between the precursor components start already above 873 K. The precursor mixture from commercial grade materials offers an economically advantageous process route with high Mo yield in steel.

  • 213.
    Chychko, Andrei
    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, Seshadri
    Foaming in Electric Arc Furnace: Part II: Foaming visualization and Comparison with Plant trials2012Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 43, nr 5, s. 1078-1085Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The kinetics of slag foaming by limestone particles was studied at 1773 K (1500 A degrees C) with the aid of an X-ray imaging system. Two models were implemented to describe the decrease in foam height with the time on the basis of the lowering of the average temperature and CaO shell formation during decomposition reaction. The energy impact of carbonate additions was studied on an industrial scale in a 100-ton electric arc furnace (EAF). It was found that, in the case of the addition of carbonates after the scrap is completely molten, the heat effects for limestone and dolomite (2255 and 2264 kJ/kg, respectively) were only 70 pct from theoretical values. Comparing these values with similar additions during the scrap melting stage shows that the energy requirements in the case of carbonate additions to steel bath are much smaller. It was found from the trial heats with dolomite addition to the steel bath that the partial substitution of lime by raw dolomite can be made without an increase in energy consumption.

  • 214.
    Chychko, Andrei
    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, Seshadri
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    MoO3 Evaporation Studies from Binary Systems towards Choice of Mo Precursors in EAF2010Ingår i: Steel Research International, ISSN 1611-3683, Vol. 81, nr 9, s. 784-791Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The evaporation rate of molybdenum oxide from mixtures with CaO or MgO was studied in the temperature range 300-1573 K. The investigations were carried out using high temperature X-ray diffraction and thermogravimetry. Further, additions of these precursors to molten steel in the laboratory scale and the Mo yield achieved were determined. The X-ray studies show that the calcium molybdate is formed from the oxide mixture in the temperature interval 773-873K, which precedes the beginning of evaporation of MoO3. Results of thermogravimetric studies with mixtures CaO and MgO with MoO3 as well as the compounds CaMoO4 and MgMoO4 confirm the above results. Addition of various molybdenum precursors, viz, the mixtures of carbon with pure MoO3, CaMoO4 and MgMoO4, as well as oxide mixtures (CaO + MoO3, MgO + MoO3) show that the highest yield was observed for CaMoO4 + C and MoO3 + C mixtures, while MgO + C + MoO3 mixture showed much lower yield.

  • 215.
    Claesson, Erik
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Development of a heat treatment method to form a duplex microstructure of lower bainite and martensite in AISI 4140 stee2014Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Research on bainite and martensite structures has indicated that lower bainite needles have a refining effect on the lath martensitic structure. Lower bainte needles partitions prior austenite grains and will consequently have a refining effect on the subsequent formed lath martensite. Smaller austenite grains will result in smaller lath martensitic packets and blocks and will result in enhanced mechanical properties.   In order to create a variation of lower bainte structure in a matrix of martensite, two different heat treating methods were tested. The work was focused towards the formation of lower bainite during isothermal heat treating in molten salt, above and below the MS-temperature. Both un-tempered and tempered samples were analyzed .Two different materials were tested, both were AISI 4140 but with a slightly difference in hardenability. The material provided by Ovako Steel is 326C and 326F the later had a higher hardenability. In order to better distinguish the two structures from each other when studied under a microscope, a variation of etching methods were tested.  It was possible to create a variation of lower bainite structures in a matrix of martensite.  326F shows less amount of lower bainite and provides a higher average surface hardness before tempering.

  • 216.
    Condo, Adolfo Firmino Timoteo
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Possibility of Hot Metal Re-Sulfurization During the Waiting Time in the Transfer LadleIngår i: Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
    Abstract [en]

    The investigation on the possibility of hot metal re-sulfurization during the waiting time in the transfer ladle before the BOF was carried out. According to the results, the slag was no longer a pure liquid, and different solid phases were found distributed within the slag along with small portion of liquid slag. Almost all the sulfur was found in the solid phase in the form of CaS, which is only a small fraction of slag. On the other hand, the hot metal was found to have a limited contact with the solid CaS and liquid slag which led to a very poor kinetics for re-sulfurization. Therefore, the amount of re-sulfurization in the transfer ladle was found to be very low.

  • 217.
    Condo, Adolfo Firmino Timoteo
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap. KTH.
    Study of Sulfide Capacity of Slag and Sulfur Removal from Hot Metal2018Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The present study aims at investigating the desulfurization process in hot metal and sulfide capacity of slags. The missing experimental data of sulfide capacities in Al2O3-CaOMgO-SiO2 system at 1713 K, 1743 K, 1773 K, 1823 K, 1873 K and in the Al2O3-CaO-SiO2 system at 1873 K were investigated under wellcontrolled oxygen potentials. These data along with the reliable and accurate data carefully selected from the literature were employed for KTH model optimization. The model was successfully optimized and produced good predictions of sulfide capacity between 1700 K and 1873 K for all liquid slags in the Al2O3-CaO-MgO-SiO2 system, especially for ladle slags and blast furnace slags, with an average relative deviation of approximately 15%. The partition of sulfur in the blast furnace at tapping was investigated. The results of re-melted slag and hot metal at temperatures of 1743 K and 1773 K showed that the two phases were not in equilibrium with respect to sulfur at tapping. Furthermore, about 30 min was required to reach equilibrium. The optimum equilibrium sulfur partition in the range of blast furnace slag was determined using sulfide capacity data calculated with the newly-optimized model. The results showed clearly that the best area which provides a good equilibrium sulfur partition is between 10 to 14 mass% MgO. The effect of aged CaC2 on the desulfurization of hot metal was investigated at 1673 K and 1773 K. The results show that the use of aged CaC2 does not have significant effect on the desulfurization process since all the samples used exhibited almost the same performance, despite being subject to different aging treatments. The possibility of re-sulfurization during the long waiting time in the transfer ladle before the BOF was investigated. From the results, II different solid phases were found present in the slag along with small portion of liquid slag. In addition, majority of sulfur in the slag is in the solid phase in the form of CaS, which is only a small fraction of the slag. The liquid slag and solid CaS was found to have a limited contact with the hot metal leading to very poor kinetics for re-sulfurization. Therefore, the amount re-sulfurization that is observed in the transfer ladle was found to be very low.

  • 218.
    Condo, Adolfo Firmino Timoteo
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap. Eduardo Mondlane University, Mozambique.
    Lindstrom, David
    Kojola, Niklas
    Sichen, Du
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Study on the Effect of Aging on the Ability of Calcium Carbide for Hot Metal Desulfurization2016Ingår i: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 87, nr 9, s. 1137-1143Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Industrial trials and laboratory study are carried out to investigate the effect of aging on the ability of CaC2 in hot metal desulfurization. The industrial trials indicate that the time of storage of calcium carbide within the limit of industrial practice has no appreciable effect on its ability of desulfurization. In the laboratory, samples of CaC2 are prepared by exposing them in air for different times to promote formation of a Ca(OH)(2) outer layer. The thickness of Ca(OH)(2) increases with exposing time. Thereafter, the aged CaC2 samples are employed for desulfurization at 1673 and 1773 K for 8 min. For all the samples after desulfurization, layers of graphite and CaO are found between the remaining CaC2 particles and the outer CaS layer. The desulfurization using CaC2 is found to proceed by the diffusion of calcium vapor through the product layers and then its reaction with dissolved sulfur in the hot metal at the surface. No appreciable difference in the thickness of the CaS layer is found with the samples exposed to air for different times. This finding explains well the industrial results.

  • 219.
    Condo, Adolfo Firmino Timoteo
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Lindström, David
    Sichen, Du
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Study on the Equilibrium of Slag and Hot Metal at Tapping with Respect to Sulfur2017Ingår i: Steel Research International, Vol. 88, nr 6, s. 1-9Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The blast furnace slag and hot metal were collected from the industrial trials. The collected slag and hot metal samples are re-melted in a graphite crucible and stirred to investigate the sulfur partition at different stirring times. The experimental oxygen potential is well controlled to simulate the blast furnace conditions. The results show evidently that sulfur is transferred from hot metal to slag, which led to an increase in the sulfur partition from its initial value (t=0 min) of 26 -33 at 1743 K, and from 23 to 37 at 1773 K after 30 min of slag-metal reaction. The results strongly indicate non-equilibrium between slag and hot metal at tapping. The sulfide capacities of the slag with typical composition of the slag at tapping are determined. On the basis of the sulfide capacity data, the theoretical sulfur partition is evaluated. The theoretically calculated partition further supports the finding obtained in the stirring experiments. This finding would suggest the possibility of improvement to increase the usage of blast furnace slag in desulfurization.  

  • 220.
    Condo, Adolfo Firmino Timoteo
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Qifeng, Shu
    Sichen, Du
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Sulfide Capacities in the Al2O3-CaO-MgO-SiO2 System2018Ingår i: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 89, nr 8, artikel-id 1800061Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the present study, the sulfide capacities of the slags in the ternary Al2O3-CaO-SiO2 system at 1873K, and in the quaternary system Al2O3-CaO-MgO-SiO2 at 1823 and 1873K are experimentally measured using copper-slag equilibrium at controlled oxygen partial pressure. The experimental data, which has been unavailable, are needed for the improvement of a sulfide capacity model. An assessment of the available data for sulfide capacities in the Al2O3-CaO-MgO-SiO2 system and its sub lower-order systems are made. Based on this assessment and the present experimental results, the model parameters of the existing sulfide capacity model are re-optimized. The sulfide capacity model can be successfully used in the prediction of the sulfide capacities of multicomponent slags with satisfactory accuracy.

  • 221.
    Correa Zapisotski, David
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Wallhed, Martin
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Characterizing flowability of metal powders2019Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Pulvermetallurgi är en växande industri med stor potential. Syftet samt problemet med detta arbete är att försöka beskriva och förstå vilka pulveregenskaper som är betydande för flödet och hur dessa egenskaper påverkar hur pulvret flödar.

    Flera olika experiment har utförts på åtta olika metallpulver, av varierande sorter material och pulverstorlek, har utförts för att undersöka samband och se vilka pulveregenskaper som är viktiga för ett metallpulver ska ha eftertraktade flödesegenskaper. Utförda experiment består av Hall flöde, tappdensitet, rasvinkel (angle of repose) samt en mer komplex Rheometer analys.

    Resultaten visar många samband mellan olika experiment och metallpulver med en del avvikelser som väntat på grund av flertalet felkällor. Resultaten för alla pulver och experiment uppvisas i stapelgrafer för enkel överblick och jämförelse.

    Metallpulvret som påvisade bäst flödesegenskaper (fritt flödande pulver) rankades som bästa pulver i varje experiment vilket indikerar att alla experiment är relevanta. Ett väl flödande metallpulver indikeras av låga värden på kohesion, rasvinkel, specifik energi osv.

  • 222.
    Dahlberg, Carl F. O.
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    Faleskog, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    An improved strain gradient plasticity formulation with energetic interfaces: theory and a fully implicit finite element formulation2013Ingår i: Computational Mechanics, ISSN 0178-7675, E-ISSN 1432-0924, Vol. 51, nr 5, s. 641-659Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A fully implicit backward-Euler implementation of a higher order strain gradient plasticity theory is presented. A tangent operator consistent with the numerical update procedure is given. The implemented theory is a dissipative bulk formulation with energetic contribution from internal interface to model the behavior of material interfaces at small length scales. The implementation is tested by solving some examples that specifically highlight the numerics and the effect of using the energetic interfaces as higher order boundary conditions. Specifically, it is demonstrated that the energetic interface formulation is able to mimic a wide range of plastic strain conditions at internal boundaries. It is also shown that delayed micro-hard conditions may arise under certain circumstances such that an interface at first offers little constraints on plastic flow, but with increasing plastic deformation will develop and become a barrier to dislocation motion.

  • 223.
    Dahlberg, Carl F. O.
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    Faleskog, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    Strain gradient plasticity analysis of the influence of grain size and distribution on the yield strength in polycrystals2014Ingår i: European journal of mechanics. A, Solids, ISSN 0997-7538, E-ISSN 1873-7285, Vol. 44, s. 1-16Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Plane strain models of polycrystalline microstructures are investigated using strain gradient plasticity (SGP) and a grain boundary (GB) deformation mechanism. The microstructures are constructed using a non-linear constrained Voronoi tessellation so that they conform to a log-normal distribution in grain size. The SGP framework is used to model the grain size dependent strengthening and the GB deformation results in a cut-off of this trend below a certain critical grain size. Plastic strain field localization is discussed in relation to the non-local effects introduced by SGP and a material length scale. A modification of the Hall-Petch relation that accounts for, not only the mean grain size, but also the statistical size variation in a population of grains is proposed.

  • 224.
    Dahlberg, Carl F. O.
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    Faleskog, Jonas
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    Niordson, Christian F.
    Legarth, Brian Nyvang
    A deformation mechanism map for polycrystals modeled using strain gradient plasticity and interfaces that slide and separate2013Ingår i: International journal of plasticity, ISSN 0749-6419, E-ISSN 1879-2154, Vol. 43, s. 177-195Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Small scale strain gradient plasticity is coupled with a model of grain boundaries that take into account the energetic state of a plastically strained boundary and the slip and separation between neighboring grains. A microstructure of hexagonal grains is investigated using a plane strain finite element model. The results show that three different microstructural deformation mechanisms can be identified. The standard plasticity case in which the material behaves as expected from coarse grained experiments, the nonlocal plasticity region where size of the microstructure compared to some intrinsic length scale enhances the yield stress and a third mechanism, active only in very fine grained microstructures, where the grains deform mainly in relative sliding and separation.

  • 225.
    Dahlberg, Carl F.O.
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.).
    Saito, Y.
    Öztop, M.S.
    Kysar, J. W.
    Geometrically necessary dislocation density measurements at a grain boundary due to wedge indentation into an aluminum bicrystal2017Ingår i: Journal of the mechanics and physics of solids, ISSN 0022-5096, E-ISSN 1873-4782, Vol. 105, s. 131-149Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An aluminum bicrystal with a symmetric tilt Σ43 (3 3 5)[1 1 0] coincident site lattice grain boundary was deformed plastically via wedge indentation under conditions that led to a plane strain deformation state. Plastic deformation is induced into both crystals and the initially straight grain boundary developed a significant curvature. The resulting lattice rotation field was measured via Electron Backscatter Diffraction (EBSD). The Nye dislocation density tensor and the associated Geometrically Necessary Dislocation (GND) densities introduced by the plastic deformation were calculated. The grain boundary served as an impediment to plastic deformation as quantified through a smaller lattice rotation magnitude and smaller GND density magnitudes in one of the crystals. There is evidence that the lattice rotations in one grain brought a slip system in that grain into alignment with a slip system in the other grain, upon which the impediment to dislocation transmission across the grain boundary was reduced. This allowed the two slip systems to rotate together in tandem at later stages of the deformation. Finite element crystal plasticity simulations using classical constitutive hardening relationship capture the general features observed in the experiments.

  • 226.
    Dahlberg, Carl
    et al.
    Columbia University.
    Saito, Yuki
    Columbia University.
    Öztop, Muin S.
    Columbia University.
    Kysar, Jeffrey W.
    Columbia University.
    Geometrically necessary dislocation density measurements associated with different angles of indentations2014Ingår i: International journal of plasticity, ISSN 0749-6419, E-ISSN 1879-2154, Vol. 54, s. 81-95Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Experiments and numerical simulations of various angles of wedge indenters into face-centered cubic single crystal were performed under plane strain conditions. In the experiments, the included angles of indenters are chosen to be 60 degrees, 90 degrees and 120 degrees and they are indented into nickel single crystal into the < 00 (1) over bar > direction with its tip parallel to < 1 1 0 > direction, so that there are three effective in-plane slip systems on (1 1 0) plane. Indenters are applied 200 mu m in depth. The midsection of the specimens is exposed with a wire Electrical Discharge Machining (EDM) and the in-plane lattice rotations of the region around the indented area are calculated from the crystallographic orientation maps obtained from electron backscatter diffraction (EBSD) measurement. No matter which angles of indenters are applied, the rotation fields are very similar. There is a strong lattice rotation discontinuity on the line below the indenter tip. The magnitude of the lattice rotation ranges from -20 degrees to 20 degrees. Lower bounds on the Geometrically Necessary Dislocation (GND) densities are also calculated and plotted. The numerical simulations of the same experimental setup are performed. The simulation results of lattice rotation and slip rates are plotted and compared with the experimental result. There is high correlation between the experimental result and the numerical result.

  • 227. Dahle, A. K.
    et al.
    Hillert, Mats
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Discussion of "nucleation mechanism of eutectic phases in aluminum-silicon hypoeutectic alloys"2005Ingår i: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 36, nr 6, s. 1612-1613Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A previous study tried to prove that each plate of Si in the ordinary Al-Si eutectic is nucleated individually by the action of a small iron-containing particle. The study justified the need for a more complete understanding of the Al-Si eutectic reaction in the absence of chemical modifiers in order to shed light on the complicated mechanisms operating in chemically modified Al-Si alloys. Reacting to this claim, the present authors state that the mechanisms of the ordinary eutectic reaction of Al-Si alloys have been well understood for several decades, thus a very strong evidence is required to justify a revision of that understanding. For their part, the authors of the first study justified their claim for a revision by considering results of thermal analyses, optical microscopy, scanning and transmission electron microscopy, and selected area electron diffraction (SAED) analyses and elemental X-ray mapping performed on samples of precisely controlled chemistry.

  • 228.
    Dahlin, Anders
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Influence of Ladle-slag Additions on BOF-Process Parameters2011Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The influence of ladle-slag additions on the BOF-process performance were investigated in plant trials. The aim of the study was to recycle ladle slag from secondary steelmaking to the LD-converter to save lime and improve the slag formation. More specifically, two plant trial campaigns covering in total 83 heats, whereof 47 with ladle-slag additions and 36 without ladle-slag additions, were performed.

     Slag and steel sampling of the process were performed at tapping as well as during blowing at 15, 35, and 65% of the total blowing time. During the first campaign, ladle slag was added through the chute and lime reductions were made manually to correct for the ladle-slag addition.

     In the second campaign, a development of the approach was made to suite a normal production practice. More specifically, the ladle slag was added through the weight-hopper system and implemented in the process-control system. In this way, the lime additions were reduced automatically by approximately 260 kg per heat. Moreover, the heat balance was compensated with a reduction in the iron-ore consumption. Additionally, the lance program was modified and the lance was lowered in the initial stages of the blow.

     On the positive side, it was found that no demerits in the metallurgical performance of the process occur when ladle slag is recycled to the BOF-process. Furthermore, only slight affections on the slag composition were found, mainly with respect to the Al2O3 and FeO-content. In addition, the ladle slag was shown to melt during the initial stages of the blow. This contributed to an increased slag weight both during the blow and at tapping. However, a negative effect on the blowing time was experienced during the trials. Although, this effect was more pronounced during the first campaign and could be reduced with a controlled heat balance during the second campaign.

     

     

  • 229.
    Dahlin, Anders
    et al.
    LKAB, Malmberget, Sweden.
    Eriksson, Johan
    Swerea MEFOS AB, Process Metallurgy Department, Luleå, Sweden.
    Tilliander, Anders
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jönsson, Pär G.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Influence of ladle slag additions on BOF process under production conditions2012Ingår i: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 39, nr 5, s. 318-326Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The influence of recycled ladle slag on the basic oxygen furnace (BOF) process under production conditions was investigated in plant trials. More specifically, 25 heats with ladle slag additions and 23 heats without ladle slag additions were studied. Both steel and slag samples were collected, from which the chemical compositions were determined. In addition, several process parameters were monitored. Overall, it was found that recirculation of ladle slag during normal production conditions works fine. On the positive side, it was seen that the steel quality concerning the phosphorus and sulphur contents of liquid steel has, in accordance with previous studies, not been affected by the ladle slag additions. Furthermore, no major differences in the slag composition occur when the recycling of ladle slag to BOF is performed. Finally, in comparison to previous studies, the increased tendency for slopping when adding ladle slag could be eliminated with a change in the lance schedule. However, on the negative side, it was seen that the addition of ladle slag leads to an increased blowing time due to lower iron ore additions. Moreover, the slag weight at tapping increased due to an increased weight of added slag formers.

  • 230.
    Dahlin, Anders
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jönsson, Pär G.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    A theoretical study of the effect of ladle-slag additions on the BOF processManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    A Case study has been performed using the commercial Multi‐Phase equilibrium (MPE) software. The aim was to study the effect on the energy balance of an industrial BOF converter when recycling of ladle slag is made to the process. A reference simulation was made with typical process parameters of an industrial converter without the addition of ladle slag. The energy penalty of recycling ladle slag to the process was found to be 1728 MJ. Moreover, five different options to obtain an energy balance in the converter were studied. The results showed that either the scrap weight could be decreased by 1.5t, or the iron‐ore addition could be reduced with 380 kg. These two solutions offered consistent metallurgical performance in the process, but had drawbacks due to a decreased yield and an increased blowing time respectively. It was also found that the chemical energy released from the process could be increased, by oxidizing FeO or adding FeSi. However, this had negative effects on the process time as well as the steel quality. The most beneficial way for the BOF process to compensate for the energy loss is to reduce the tapping temperature with 12°C. This will also have positive effects on the phosphorus removal in the process. The results also showed that 200 kg per heat of burnt lime could be saved thanks to the recirculation of ladle slag. However, concluding remarks on the environmental and economical effect of the different options to compensate for the energy penalty needs to be assessed by a Life Cycle Analysis in the future to which this study can act as a useful guide.

     

  • 231.
    Dahlin, Anders
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Tilliander, Anders
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Eriksson, Johan
    Swerea MEFOS AB, Process Metallurgy Department, Luleå, Sweden.
    Jönsson, Pär G.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Influence of ladle slag additions on BOF process performance2012Ingår i: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 39, nr 5, s. 378-385Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A plant trial has been performed, with recycling of ladle slag to the LD converter at SSAB EMEA, Lulea, Sweden. The effect of ladle slag addition on the slag and steel composition, together with the slag weight, was investigated with sampling both during the blow and at blow end. The addition of ladle slag resulted in an increase in slag weight between 1 and 2 t throughout the blow and an increase of 3 wt-% in the slag Al2O3 content. This indicated that the ladle slag melted during the initial stages of the blow and enhanced the early slag formation. Lime additions were reduced with 3.5 kg t(-1) liquid steel without drawbacks on the phosphorus or sulphur refining. Heats with added ladle slag had an increase in blowing time with similar to 4% and an increased tendency for slopping. However, this can be handled by different lance and addition programmes.

  • 232.
    Dahlqvist, v
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Increase the capacityof continuous annealing furnaces at Ovako2012Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The capacity of soft annealing of low alloyed tubes at Ovako’s continuous annealing furnaces have been evaluated by comparing how it is done today with information from published and internal articles on the subject. It was found that it is possible to reduce the cycle time by 30 % for one furnace, 55 % for one furnace and 72 % for two furnaces. Two separate fullscale tests were made to assess whether the faster soft annealing procedure was feasible. The tests were performed without any reconstruction of the furnace and were made by continuously vary the speed of the batch inside thefurnace. The temperature in the batch was measured and compared with results from computer simulations of the heating/cooling sequences. The computer simulations were performed in COMSOL. The soft annealing was evaluated according to the SEP-520 standard ,which means evaluating the microstructure and hardness. The results show that the faster heat treatment could yield lower grades than today but still meet it’s requirements. In order to achieve this increase  a reconstruction of the furnaces is needed and the reconstruction is  briefly treated in the report. Ideas to further increase the speed of the soft annealing procedure are also presented.

  • 233.
    Dahlström, Alexander
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialteknologi.
    Wear mechanisms in austenitic stainless steel drilling: A comprehensive wear study2015Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    This thesis is meant to serve as part of a competence platform for future product development projects at Sandvik Coromant AB, Solid Round Tools Department, Västberga, Sweden. The project objective is to gain generic knowledge of the wear mechanisms that restrict tool lifetime when drilling austenitic stainless steel. Thus, identifying if the weakest link of the tool is located within the coating, the coating adherence or in the strength of the substrate. A theoretical review of the work-piece and tool materials has been conducted as a background, along with definition of tool geometry and process parameters. Furthermore, the review includes chemical and process design effect on mechanical properties of the austenitic stainless steel, TiAlN coatings and cemented carbide substrates. Additionally, the basic principles of the wear mechanisms and wear types that are specific to drilling have been reviewed. During the experimental procedures both solid and exchangeable tip drills from cemented carbide with multilayered PVD TiAlN coatings were tested. Two series of tests were conducted, the first series aimed to identify wear type dependency on cutting speed, focusing on wear of the tool margin. The second test series was performed to map the wear progression depending on distance. Analyses including identification the main wear mechanism, quantification the amount of wear, identify wear location on the tool, crack investigation and WDS analysis of chemical wear. Adhesive coating wear was found on the tool margin at an early stage. The adhesive wear rapidly progressed into a stable intermediate stage. Leaving the substrate exposed and more susceptible to other wear types resulting in crack and oxide layer formation. 

  • 234.
    Dai, J. H.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik. Harbin Inst Technol Weihai, Sch Mat Sci & Engn, 2 West Wenhua Rd, Weihai 264209, Peoples R China..
    Li, Wei
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Song, Y.
    Harbin Inst Technol Weihai, Sch Mat Sci & Engn, 2 West Wenhua Rd, Weihai 264209, Peoples R China..
    Vitos, Levente
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik. Uppsala Univ, Dept Phys & Astron, Div Mat Theory, Box 516, SE-75120 Uppsala, Sweden.;Wigner Res Ctr Phys, Inst Solid State Phys & Opt, POB 49, H-1525 Budapest, Hungary..
    Theoretical investigation of the phase stability and elastic properties of TiZrHfNb-based high entropy alloys2019Ingår i: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 182, artikel-id UNSP 108033Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    First principles calculations are performed to study the effects of alloying elements (X = Al, Si, Sc, V, Cr, Mn, Cu, Zn, Y. Mo, Ta, W and Re) on the phase stability and elastic properties of TiZrHfNb refractory high entropy alloys. Both equimolar and non-equimolar alloys are considered. It is shown that the calculated lattice parameters, phase stability and elastic moduli of equimolar TiZrHfNbX are consistent with the available experimental and theoretical results. The substitutions of alloying elements at Ti, Zr, and Hf sites with various contents show similar effects on the phase stability and elastic properties of the TiZrHINb-based alloys. The substitutions on Nb site are found to generally decrease the stability of body centered cubic phase. Close connections between the charge densities at the Wigner-Seitz cell boundary and the bulk moduli of TiZrHfNb-based alloys are found. The present results provide a quantitative model for exploring the phase stability and elastic properties of TiZrHINb-based alloys from the electronic structure viewpoint. Elsevier Ltd.

  • 235.
    Danielsson, Olivia
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Jonsson, Sonja
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Mildenberger, Ida
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Corrosion in the coolant circuit of Pansarterrängbil 2032016Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The military vehicle, Pansarterrängbil 203 (PATGB 203) demonstrates a fault. There are some components in a coolant circuit that fail due to corrosion while others are unaffected. One of the affected components that will be investigated in this report is the water heater. The subject of this technical investigation has been an issue for FMV, Swedish Defence Materiel Administration since a decade. While seeking out the cause of the coolant circuit failing, this investigation aim to analyzing the underlying problems considering material, factors of corrosion and organization.

    In order to establish the origin of material and appearance of corrosion, experiments were performed. The experiments showed that the original material is an Al-Si alloy. The micrographs indicated varying stratification of the corrosion throughout the unit. The corrosive deposits consisted mainly of oxygen, silicon, aluminum and sodium.

    Consequently, the protecting passive oxide layer is compromised, which results in a direct connection between the coolant and the underlying material. This direct connection gives rise to the development of corrosion in the material. Clear underlying causes of the corrosion were not found but the most probable suggest on galvanic corrosion accelerated by a stray current. Properly grounding the components decreases the stray current in the system and is essential to avoid corrosion. If grounding the components is not sufficient, additional checks of the coolant with attention to the pH-value and the function of corrosion inhibitors may indicate corrosion at an earlier stage.

  • 236.
    Das, Yadunandan B.
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap. Open Univ, Mat Engn, Walton Hall, Milton Keynes MK7 6AA, Bucks, England.
    Forsey, Alexander N.
    Open Univ, Mat Engn, Walton Hall, Milton Keynes MK7 6AA, Bucks, England..
    Kelleher, Joe
    Rutherford Appleton Lab, ISIS Facil, Didcot, Oxon, England..
    Kabra, Saurabh
    Rutherford Appleton Lab, ISIS Facil, Didcot, Oxon, England..
    Fitzpatrick, Michael E.
    Coventry Univ, Fac Engn & Comp, Coventry, W Midlands, England..
    Simm, Thomas H.
    Swansea Univ, Coll Engn, Bay Campus, Swansea, W Glam, Wales..
    Gungor, Salih
    Open Univ, Mat Engn, Walton Hall, Milton Keynes MK7 6AA, Bucks, England..
    Moat, Richard J.
    Open Univ, Mat Engn, Walton Hall, Milton Keynes MK7 6AA, Bucks, England..
    The influence of temperature on deformation-induced martensitic transformation in 301 stainless steel2018Ingår i: Materials Science and Technology, ISSN 0267-0836, E-ISSN 1743-2847, Vol. 34, nr 17, s. 2114-2125Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Deformation-induced martensitic transformations are increasingly being used to create desirable mechanical properties in steels. Here, the kinetics of the deformation-induced martensitic transformation is investigated at 300, 263, 223, 173 and 100 K using in situ neutron diffraction during tensile loading. The results from these experiments show a distinct change in the transformation behaviour between 300 K and the tests conducted at 263 K and below, causing a difference in martensite structure. The difference in transformation kinetics is correlated to the suppression of slip at low temperatures, as evidenced using diffraction peak intensity analysis for different grain families and corroborated using transmission electron microscopy. A direct correlation between the deformation-induced martensite fraction and the work-hardening rate is shown.

  • 237. Davoodi, A.
    et al.
    Pan, Jinshan
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Leygraf, Christofer
    KTH, Skolan för kemivetenskap (CHE), Kemi, Yt- och korrosionsvetenskap.
    Parvizi, R.
    Norgren, S.
    An insight into the influence of morphological and compositional heterogeneity of an individual intermetallic particle on aluminium alloy corrosion initiation2013Ingår i: Materials and corrosion - Werkstoffe und Korrosion, ISSN 0947-5117, E-ISSN 1521-4176, Vol. 64, nr 3, s. 195-198Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, a multi-analytical in situ and ex situ approach was used to provide information needed to identify the role of an individual heterogeneous intermetallic particle (IMP) in localized corrosion initiation of aluminium alloys. The heterogeneity of the IMP was studied by combining atomic force microscopy (AFM), scanning electron microscopy and energy dispersive spectroscopy (SEMEDS) and scanning electrochemical microscopy (SECM). A complex AlMnFeSi IMP phase with different chemical composition in its inner and outer parts was characterized by SEMEDS analysis. AFM results uniquely revealed a brain-like feature of an IMP with 20nm height variations. Submicron sized galvanic cell induced by morphological and compositional heterogeneity resulted in a localized corrosion attack inside the individual IMP. Various collected current levels measured by SECM were associated to the morphological and compositional heterogeneity of IMPs.

  • 238.
    Davydenko, Arkadiy
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Some aspects of recycling of rest products and slag foaming in the EAF during stainless steel production2014Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    An efficient stainless steel making industry is defined by different factors such as an efficient utilisation of energy in the Electric Arc Furnace (EAF). This requires a good by slag foaming practice and an utilisation of waste products from own production facilities. In the following study, briquettes applied for a combined slag foaming and waste product recycling in the EAF were investigated in both laboratory and industrial scales. More specifically, briquettes were characterised and used for slag foaming in the EAF. The recipes of the briquettes were made based on a literature review and previous experience. Afterwards, the composition and density of briquettes were defined and compared to calculated data. Moreover, weight reduction experiments were made on a laboratory scale at temperatures up to 1500°C in an argon atmosphere in order to characterise the products (metal, slag and gas) produced by briquettes. The calculations were also compared to experimental data. Thereafter, briquettes with different densities and pet-coke addition were tested on an industrial scale to study slag foaming in the EAF process during a stainless steel production. The slag foaming tendencies were determined based on visual estimations of slag foaming, determinations of the slag density before and after additions of different briquettes, and by calculating a foaming index.  Moreover, the influence of the main parameters of the briquettes (composition, density) and the furnace slag (composition, basicity and etc.) on slag foaming was studied.  

    Investigation of briquettes made on laboratory and industrial scales provided the following main results: the density of briquettes can successfully be verified, briquettes have different mechanical properties depending on the materials used for production of briquettes, briquettes yield different amounts of metal and gas. Moreover, it was found that the heavy briquettes (containing FeCr) produce about half the amount of gas compared to the light briquettes (without FeCr). The main part of the gas was generated during the first 2-3 min. Also, the valuable metals can be recovered from briquettes; recipes of briquettes can be optimized based on the amount of metal droplets in briquettes and the total utilisation of carbon.  In addition, it was found that both heavy and light briquettes can be used for slag foaming. The highest slag foaming rate was obtained for slags with a basicity in the range of 1.31-1.49.

  • 239.
    Davydenko, Arkadiy
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Karasev, Andrey
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Glaser, Bjoern
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Direct Reduction of Fe, Ni and Cr from Oxides of Waste Products Used in Briquettes for Slag Foaming in EAF2019Ingår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, nr 20, artikel-id 3434Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Environmental aspects and the sustainable manufacturing of steels require producers to pay more and more attention to the efficient utilization of materials and waste products during steelmaking. This study is focused on the evaluation of possibilities for the recovery of metals (such as Fe, Ni and Cr) from waste products used for slag foaming in the Electric Arc Furnace (EAF) process. Two types of industrial briquettes were produced by mixing mill-scale from the hot rolling of stainless steels with anthracite and pet-coke, respectively. Thereafter, an assessment of the metal reduction processes in briquettes at high temperatures (1500 degrees C) was made by using laboratory thermo-gravimetric reduction experiments in an argon atmosphere. The amounts of metal, slag and gas obtained from the briquettes were estimated. In addition, the velocity and time for the removal of metal droplets from the liquid slag depending on the size of the metal droplets was estimated. It was found that up to 97% of metal droplets can be removed from the slag during the first 30 min. Moreover, results showed that most of the Cr, Ni and Fe (up to 93-100%) can be reduced from oxides of these metals in briquettes at 1500 degrees C. Moreover, the anthracite and pet-coke in the investigated briquettes have similar reduction capabilities. It was found that up to 330 kg of Fe, 28 kg of Ni and 66 kg of Cr per ton of added briquettes can be recovered from waste products by the industrial application of those briquettes for slag foaming in EAF.

  • 240.
    Davydenko, Arkadiy
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Karasev, Andrey
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Lindstrand, Gunnar
    Outokompu.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Investigation of Slag Foaming by Additions of Briquettes in the EAF during Stainless Steel Production2015Ingår i: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 86, nr 2, s. 146-153Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Nowadays, an effective application of energy required for stainless steel production in the electric arc furnace (EAF) by a slag foaming practice and recycling of waste products play two of the most significant roles for a sustainable steel production. In this study, briquettes were used to obtain a combined slag foaming and waste product reduction in the EAF process. Briquettes with different densities produced partly from waste products were tested in an industrial scale to study slag foaming in the EAF process during stainless steel production. The slag foaming tendency was determined based on visual estimations of slag foaming, evaluations of the slag density before and after addition of different briquettes, and by calculating a foaming index. The influence of the main parameters of briquettes (composition, density) and the furnace slag (composition, basicity, and, etc.) on slag foaming was studied. It was found that both heavy and light briquettes can be used for slag foaming. The heavy briquettes, with FeCr, produce about half the amount of gas compared to the light briquettes, without FeCr. The main part of the gas, >80%, was generated during the first 2-3min, Moreover, the highest slag foaming rate was obtained for slags with a basicity in the range of 1.31-1.49.

  • 241.
    Davydenko, Arkadiy
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Mostafaee, Saman
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi. Ovako Hofors.
    Karasev, Andrey
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Characterization of Briquettes Used for Slag Foaming in the EAF during Stainless Steel Production2014Ingår i: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 86, nr 2, s. 137-145Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The modern sustainable stainless steel making industry is characterized by different factors such as an efficient utilization of energy in the Electric Arc Furnace (EAF) by a slag foaming practice and an utilization of waste products from its own production facilities. In this study, the foaming briquettes applied for a combined slag foaming and waste product reduction in the EAF are characterized. The recipes of the briquettes were made based on a literature review and previous experience. Afterwards, the composition and density of briquettes were estimated and compared to calculated data. Moreover, weight reduction experiments were made on a laboratory scale at temperatures up to 1500-°C in an argon atmosphere in order to characterize the products (metal, slag, and gas). Based on these results, the calculations were compared with experimental data. The following main results were found: (i) the density of briquettes can be successfully verified, (ii) briquettes have different mechanical properties depending on the materials used for production of briquettes, and (iii) the briquettes yield in different amounts of metal and gas. Moreover, it was found that light briquettes (without FeCr) produced almost double the amount of gas in comparison with heavy briquettes (containing FeCr); valuable metals can be recovered from briquettes, and recipes of briquettes can be optimized based on the amount of metal droplets in briquettes and the total utilization of carbon. This study is focused on a characterization of briquettes, which are used for slag foaming and waste product reduction in the Electric Arc Furnace (EAF) during the stainless steel production. The experimental data is compared with calculations according to the obtained results.

  • 242.
    De Colle, Mattia
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Topological Data Analysis to improve the predictive model of an Electric Arc Furnace2016Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Data mining, and in particular topological data analysis (TDA), had proven to be successful inabstracting insights from big arrays of data. This thesis utilizes the TDA software AyasdiTM inorder to improve the accuracy of the energy model of an Electric Arc Furnace (EAF), pinpointingthe causes of a wrong calculation of the steel temperature. Almost 50% of the charges analyzedpresented an underestimation of temperature, while under 30% an overestimation.First a dataset was created by filtering the data obtained by the company. After an initialscreening, around 700 charges built the dataset, each one characterized by 104 parameters. Thedataset was subsequently used to create a topological network through the TDA software. Bycomparing the distribution of each parameter with the distribution of the wrong temperatureestimation, it was possible to identify which parameters provided a biased trend. In particular, itwas found that an overestimation of temperature was caused by an underestimation of themelting energy of materials not having through a melting test. It was also found a possible biasedtrend in some distribution of parameters like %O in steel and slag weight, which it is believedare all connected together. Despite not finding a global solution for the reasons behind theunderestimation of temperature, it is believed that a different settings more focused around thematerials used as scrap mix can highlight more on that subject. In conclusion TDA proved itselfefficient as a problem solving technique in the steel industry.

  • 243.
    De Colle, Mattia
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processvetenskap.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Karasev, Andrey
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Gauffin, Alicia
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Renman, Agnieszka
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Vatten- och miljöteknik.
    Renman, Gunno
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Hållbar utveckling, miljövetenskap och teknik, Vatten- och miljöteknik.
    The Use of High-Alloyed EAF Slag for the Neutralization of On-Site Produced Acidic Wastewater: The First Step Towards a Zero-Waste Stainless-Steel Production Process2019Ingår i: Applied Sciences, ISSN 2076-3417, Vol. 9, nr 19, artikel-id 3974Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Recycling of steelmaking slags has well-established applications, such as their use in cement, asphalt, or fertilizer industries. Although in some cases, such as the electric arc furnace (EAF) high-alloyed stainless-steel production, the slag’s high metal content prevents its use in such applications. This forces companies to accumulate it as waste. Using concepts such dematerialization, waste management, industrial symbiosis, and circular economy, the article drafts a conceptual framework on the best route to solving the landfilling issue, aiming at a zero-waste process re-design. An experimental part follows, with an investigation of the use of landfill slag as a substitute of limestone for the neutralization of acidic wastewater, produced by the rinsing of steel after the pickling process. Neutralization of acidic wastewater with both lime and slag samples was performed with two different methods. Two out of four slag samples tested proved their possible use, reaching desired pH values compared to lime neutralizations. Moreover, the clean waters resulting from the neutralizations with the use of both lime and slag were tested. In terms of hazardous element concentrations, neutralization with slag yielded similar results to lime. The results of these trials show that slag is a potential substitute of lime for the neutralization of acidic wastewater.

  • 244.
    Delandar, Arash Hosseinzadeh
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Gorbatov, O. I.
    Gornostyrev, Yu. N.
    Korzhavyi, Pavel A.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Ab-initio based search for late blooming phase compositions in iron alloysManuskript (preprint) (Övrigt vetenskapligt)
  • 245.
    Delandar, Arash Hosseinzadeh
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Sandström, Rolf
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Korzhavyi, Pavel A.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    The role of glide during creep of copper at low temperaturesManuskript (preprint) (Övrigt vetenskapligt)
  • 246.
    Delczeg, Lorand
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Ab-initio description of mono-vacancies in metals and alloys2011Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Trough the following pages a comprehensive study of open structures will be shown, including mono-vacancy calculations and open surfaces. These are electronic structure calculations using density functional theory within the exact muffin tin method.

    First we investigate the accuracy of five common density functional approximations for the theoretical description of the formation energy of mono-vacancies in three closepacked metals. Besides the local density approximation (LDA), we consider two generalized gradient approximation developed by Perdew and co-workers (PBE and PBEsol) and two gradient-level functionals obtained within the subsystem functional approach (AM05 and LAG). As test cases, we select aluminium, nickel and copper, all of them adopting the face centered cubic crystallographic structure.

    This investigation is followed by a performance comparison of the three common gradientlevel exchange-correlation functionals for metallic bulk, surface and vacancy systems. We find that approximations which by construction give similar results for the jellium surface, show large deviations for realistic systems. The particular charge density and density gradient dependence of the exchange-correlation energy densities is shown to be the reason behind the obtained differences. Our findings confirm that both the global (total energy) and the local (energy density) behavior of the exchange-correlation functional should be monitored for a consistent functional design.

    Last we show the vacancy formation energies of paramagnetic Fe-Cr-Ni alloys as a function of chemical composition. The theoretical predictions obtained for homogeneous chemistry and relaxed nearest-neighbors are in line with the experimental observation. In particular, Ni is found to decrease and Cr increase the vacancy formation energy of the ternary system.

  • 247.
    Deng, Tengfei
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Mikro-modellering.
    Study on the dissolution of lime and dolomite in converter slag2012Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    In the present study, the dissolution mechanism and rate of lime, limestone and dolomite in converter slag was studied. Lime dissolution in stagnant slag was studied first and dissolution of lime, limestone and dolomite under forced convection were carried out by new experimental setup.

    Dissolution of different CaO samples into stagnant converter slags was carried out in a closed tube furnace at 1873K. In the case of CaO-‘FeO’-SiO2 slag, the dissolution of CaO rod in the stagnant slag was retarded after the initial period (2 minutes). A dense layer of 2CaO∙SiO2 was found to be responsible for the total stop of the dissolution. It could be concluded that constant removal of the 2CaO∙SiO2 layer would be of essence to obtain high dissolution rate of lime. In this connection, it was found necessary to study the dissolution of lime in moving slag.

    In order to obtain reliable information of lime dissolution under forced convection, the commonly used rotating rod method was examined. Both CFD calculation and cold model experiments showed evidently that the mass transfer due to radial velocity introduced by forced convection was zero if the rod was centrally placed in a cylindrical container. A new experimental design was therefore developed. A cube was placed in the crucible and stirred by Mo rod along with slag. The whole system could be quenched in order to maintain the state of the system at high temperature. A linear relationship between normalized length and time was obtained for lime dissolution. Different lime samples showed big difference in dissolution rate. It was found that the main mechanism of CaO dissolution in slag was due to the removal of 2CaO∙SiO2 layer.

    Decomposition and dissolution of limestone and dolomite in slag at 1873 K were studied. The decomposition was carried out both in argon and in slag under argon atmosphere. The decomposition process was simulated using Comsol. The results showed evidently that the decomposition of limestone and dolomite was controlled mostly by heat transfer.

    It was also found that the decomposition of limestone product: CaO had very dense structure, no matter the sample was decomposed in slag or in argon. The slow decomposition and the dense CaO layer would greatly hinder the dissolution of lime in the slag. The present results clearly indicate that addition of limestone instead of lime would not be beneficial in converter process.

    Discontinuous 2CaO∙SiO2 layer along with MgO∙Fe2O3 particles was found on the surface of the dolomite sample. Some 2CaO∙SiO2 islands were found in the vicinity of the sample in the slag, which revealed therefore that the dissolution was dominated by the peeling-off of the layer of 2CaO∙SiO2-MgO∙Fe2O3 mixture. 2CaO∙SiO2, (Mg, Fe)Oss along with super cooled liquid phases were found inside dolomite sample close to the surface. 2CaO∙SiO2 phase was replaced gradually by 3CaO∙SiO2 towards the centre of the decomposed sample.

  • 248.
    Deng, Tengfei
    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.
    Dissolution mechanism of dolomite in converter slag at 1873K2014Ingår i: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 41, nr 1, s. 75-80Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The mechanism of dolomite dissolution in converter slag was studied and found to proceed by two steps: decomposition of dolomite into CaO and MgO and dissolution of the product into the slag. The first step was found to be controlled by heat transfer, which was confirmed by theoretical calculation. The decomposed dolomite had many pores, which allowed easy slag penetration. A discontinuous 2CaO.SiO2 layer along with MgO.Fe2O3 particles was found on the surface of the samples. Some 2CaO.SiO2 islands were found in the vicinity of the samples in the slag, revealing that the dissolution was dominated by peeling-off of the layer of 2CaO.SiO2- MgO.Fe2O3 mixture. 2CaO.SiO2, (Mg, Fe)Oss along with super cooled liquid phases were found inside dolomite samples close to the surface. 2CaO.SiO2 phase was replaced gradually by 3CaO.SiO2 towards the centre of the decomposed sample. While addition of small amounts of dolomite directly into the slag could be considered in steelmaking converter, too much would result in slow dissolution and waste of the raw materials.

  • 249.
    Deng, Tengfei
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Mikro-modellering.
    Glaser, Björn
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Mikro-modellering.
    Sichen, Du
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Mikro-modellering.
    Experimental Design for the Mechanism Study of Lime Dissolution in Liquid Slag2012Ingår i: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 83, nr 3, s. 259-268Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The applicability of rotating rod technique in the study of lime dissolution in slag was investigated. Both computational fluid dynamic (CFD) and cold model experiments showed that the mass transfer due to radial velocity introduced by forced convection was zero if the rod was long. The mass transfer by forced convection was also less important in comparison with natural convection and diffusion when the rod was half length of the height of the bath. This finding was in accordance with the criteria put forward by the original work that the method could only be applicable when a thin disk (instead of rod) with big diameter and big liquid bath were used. To study the lime dissolution by forced convection a new experimental technique was developed. A cube was placed in the slag that was eccentrically stirred. The whole system, viz. the sample along with the slag could be quenched. The new technique could study the effect of forced convection on the dissolution. The microscopic study on the quenched slag-lime samples could reveal the dissolution mechanism successfully.

  • 250.
    Deng, Tengfei
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Mikro-modellering.
    Nortier, Patrice
    Ek, Mattias
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Mikro-modellering.
    Du, Sichen
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Mikro-modellering.
    Limestone Dissolution in Converter Slag at 1873 K (1600 degrees C)2013Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 44, nr 1, s. 98-105Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Decomposition and dissolution of limestone in slag at 1873 K (1600 A degrees C) were studied. The limestone samples were in the shape of cubes (11 mm x 11 mm x 11 mm approximately). The decomposition was carried out both in argon and in slag under argon atmosphere. In order to gain an insight into the phenomenon of slow decomposition, the decomposition process of CaCO3 was simulated using Comsol. The results showed evidently that the decomposition of calcium carbonate was controlled mostly by heat transfer. It was also found that the decomposition product CaO had very dense structure, whether the sample was decomposed in slag or in argon. The slow decomposition and the dense CaO layer would greatly hinder the dissolution of lime in the slag. The present results clearly indicate that the addition of limestone instead of lime would not be beneficial in the converter process.

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