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  • 1.
    Alipour, Yousef
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Machining of CoCr28Mo62011Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The machining process of Cobait-Chromium medical ailoys become a veryessential topic for research due to widening range of application. They aregeneraily used because of their high wear resistance, low corrosioncharacteristics and high fatigue strength. This project describes an investigationof chip formation during the machining of Cobalt-Chromium-Molybdenum highcarbon alloy. A quick stop device has been employed to investigate mechanismof chip formation through analyzing of shear zone and shear plane. Thicknessmeasurement of segments, surface conditions after finishing, lowest valley andhighest peak with three different cutting tool inserts were studied as weil.Moreover cutting force measurement at different cutting speeds, feeds and radialnoses were performed. Microstructure and hardness of work material before andafter machining has been studied. Tool life of inserts was evaluated bymeasuring flank wear.

    The consequences obtained from the study illuminated:

    1. For the constant cutting speed and nose radius flank wear increased whenthe feed increased.
    2. For the constant feed and nose radius, increase in the cutting speedlowered flank and crater wear.
    3. Cutting force increased with the increase in feed.
    4. Increase in cutting speed to 40 m/min raised cutting force. However afterthat cutting force decreased.
    5. Insert CNMG 120408-MF1 TS2000 with cutting data v~=70 m/min, ap= 3mm and f=0.1 mm seemed fit the best in base of lower flank and craterwear, almost lower cutting force and smoother finish roughness.
  • 2.
    Al-Saadi, Munir
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Microstructures and mechanical properties: Forged vs rolled bar in Sanmac 22052016Ingår i: Stainless Steel World, ISSN 1383-7184, Vol. 28, nr July/August, s. 45-48Artikel i tidskrift (Refereegranskat)
  • 3.
    Al-Saadi, Munir
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Sandberg, Fredrik
    Karasev, Andrey
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Jonsson, Stefan
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Microstructure characterisation in alloy 8252018Konferensbidrag (Refereegranskat)
  • 4.
    Al-Saadi, Munir
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Karasev, Andrey
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Sandberg, Fredrik
    Comparative Study of Microstructures Evolution of Columnar and Equiaxed Grain Structurs in Alloy 825 after Hot Compression2018Ingår i: 3rd InternationalConference on Ingot Casting, Rolling and Forging, ICRF2018, in Stockholm, 16-19October, 2018, artikel-id 114Konferensbidrag (Refereegranskat)
  • 5.
    Al-Saadi, Munir
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi. R&D, AB Sandvik Materials Technology, SE-811 81Sandviken, Sweden..
    Sandberg, Fredrik
    R&D, AB Sandvik Materials Technology, SE-811 81Sandviken, Sweden..
    Hulme-Smith, Christopher
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Karasev, Andrey
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    A study of the static recrystallization behaviour of cast Alloy 825 after hot-compressions2019Ingår i: Journal of Physics: Conference Series, 2019, Vol. 1270Konferensbidrag (Refereegranskat)
    Abstract [en]

    The static recrystallization behaviour of a columnar and equiaxed Alloy 825 material was studied on a Gleeble-3800 thermo-simulator by single-hit compression experiments. Deformation temperatures of 1000-1200 °C, a strain of up to 0.8, a strain rate of 1s-1, and relaxation times of 30, 180, and 300 s were selected as the deformation conditions to investigate the effects of the deformation parameters on the SRX behaviour. Furthermore, the influences of the initial grain structures on the SRX behaviors were studied. The microstructural evolution was studied using optical microscopy and EBSD. The EBSD measurements showed a relaxation time of 95 % for fractional recrystallization grains, 𝑡95, in both structures, was less than 30 seconds at the deformation temperatures 1100 °C and 1200 °C. However, fewer than 95% of recrystallized grains recrystallized when the deformation temperature was lowered to 1000 °C. From the grain-boundary misorientation distribution in statically recrystallized samples, the fraction of high-angle grain boundaries decreased with an increasing deformation temperature from 1000 °C to 1200 °C for a given relaxation time. This was attributed to grain coarsening

  • 6. Antonsson, T.
    et al.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    The effect of cooling rate on the solidification of INCONEL 7182005Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 36, nr 1, s. 85-96Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The superalloy INCONEL 718 (IN718) is a commonly used material in aerospace and turbine components. The advantage of this type of material with sluggish precipitation-hardening kinetics is that IN718 is readily weldable. Both wrought and cast parts are used and welded together. While the alloy has been studied previously, new production processes such as laser treatment demand better knowledge of the solidification process in IN718. especially at high cooling rates. In this investigation. the solidification process was studied over a wide range of cooling rated by three different experimental techniques: differential thermal analysis (DTA), mirror furnace (MF), and levitation casting. The solidification sequence and the reaction temperatures were identified. The microstructure and the change in growth morphology were also studied. Segregation measurements were performed, and the distribution of Nb was analyzed in detail for the different types of samples. because of its strong impact on the solidification sequence and microstructure. New observations are that the latent heat decreases and the effective partition coefficient increases with increasing cooling rate. The diffusion rate also seems to be enhanced in the first part of primary solidified dendrites. It is suggested that the new observations can be explained by an increased number of lattice defects formed in the solid as the cooling rate increases.

  • 7.
    Arnberg, Lars
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Fredriksson, H.
    Ekerot, S.
    Tadesse, A.
    Solvent refining of silicon for solar cells –some practical aspects2020Ingår i: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 531, artikel-id 125332Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Solvent refinement has been suggested as an energy- and cost-efficient process to produce high purity silicon for photovoltaic solar cells. In this process, metallurgical grade silicon is dissolved in a liquid metal e.g. Al at high temperature. High purity silicon crystals can then be precipitated by decreasing the temperature and extracted from the melt. Residual aluminium is then removed by leaching, and after remelting and directional solidification, the purified silicon can be used as silicon for solar cells. Metallurgical grade silicon (99 wt%Si) with iron as the main impurity has been dissolved to 40 wt% in liquid aluminium at 1000 °C. Silicon crystals have been extracted slightly above the eutectic temperature. The crystals have then been leached in 10% hydrochloric acid at room temperature. Silicon crystal have been sorted into three size fraction which have been melted separately and thereafter analyzed by light optical- and electron microscopy with EDS analysis. After leaching, extracted material has been remelted together with silicon oxide in order to oxidize residual aluminium. The extracted material contains significant amounts of residual Al-Si eutectic. The aluminium has not been removed completely by the leaching and insoluble metal rich intermetallic compounds have been found in the smallest size fraction. The residual aluminium can be further reduced by oxidation by silicon oxide and sedimentation of the aluminium oxide.

  • 8.
    Arzpeyma, Niloofar
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Ersson, Mikael
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Mathematical Modeling of Postcombustion in an Electric Arc Furnace (EAF)2019Ingår i: METALS, ISSN 2075-4701, Vol. 9, nr 5, artikel-id 547Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Numerical modeling was used to study the capability of postcombustion in an electric arc furnace (EAF) equipped with virtual lance burners. The CO flow rate at the molten bath surface was estimated using the off-gas data obtained close to the outlet of an EAF. Then, the effect of the secondary oxygen flow rate on postcombustion was studied. The results show a CO flow rate of 0.6 kgs(-1) and 0.8 kgs(-1) for operation modes of burner and burner + lancing. Increase of the secondary oxygen flow rates of 60% and 70% result in 17% and 7% increase in the postcombustion ratio (PCR) for the burner and burner lancing modes, respectively.

  • 9.
    Bai, Haitong
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Ersson, Mikael
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Numerical study of an application of a divergent reverse TurboSwirl nozzle in the billet continuous casting process2019Ingår i: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 46, nr 2, s. 148-158Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The swirling flow has widely been investigated for liquid steel flowing in the continuous casting process. In this paper, a new design of the submerged entry nozzle (SEN) is applied by using a reverse TurboSwirl device with a divergent nozzle. This divergent reverse TurboSwirl nozzle (DRTSN) is shown to gain a more beneficial flow pattern compared to the straight nozzle. A stronger swirling flow can be obtained at the SEN outlet, which leads to a calmer flow field and an appropriately active meniscus flow that could improve the heat and mass transfer near the meniscus. The swirl number in the SEN is independent of the casting speed, while a lower casting speed yields a lower maximum wall shear stress. The DRTSN is connected to the tundish by an elbow and a horizontal runner. A longer horizontal runner supplies a more uniform velocity profile and a more symmetrical flow pattern.

  • 10.
    Bai, Haitong
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Ni, Peiyuan
    Northeastern Univ, Sch Met, Key Lab Ecol Met Multimet Intergrown Ores, Educ Minist, Shenyang 110819, Liaoning, Peoples R China.;Osaka Univ, Grad Sch Engn, Dept Mat & Mfg Sci, 2-1 Yamadaoka, Suita, Osaka 5650871, Japan..
    Ersson, Mikael
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Zhang, Tingan
    Northeastern Univ, Sch Met, Key Lab Ecol Met Multimet Intergrown Ores, Educ Minist, Shenyang 110819, Liaoning, Peoples R China..
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Effect of swirling flow tundish submerged entry nozzle outlet design on multiphase flow and heat transfer in mould2019Ingår i: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Effect of a swirling flow SEN (submerged entry nozzle) outlet design on the multiphase flow and heat transfer in a mould was investigated by using numerical simulation. It was found that different SEN outlet designs could form different flow patterns and temperature distributions on the upper of the mould. The enlarged outlet SEN design had an effect to decrease the horizontal velocity of liquid steel flowing out the SEN outlet, reducing the steel flow velocity towards the solidification front. Although a higher velocity was found near the slag/steel interface with the enlarged outlet SEN, but the turbulent kinetic energy was lower. The reason was that less circulation flows were formed in the region of the mould top. The weak horizontal flow towards the solidification front with the enlarged outlet SEN induced lower wall shear stresses, at the same time it also formed a lower temperature distribution near the solidified shell.

  • 11.
    Bölke, Kristofer
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Ersson, Mikael
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Andersson, Nils A. I.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Imris, Matej
    ScanArc Plasma Technol AB, SE-81321 Hofors, Sweden..
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Experimental Determinations of Mixing Times in the IronArc Pilot Plant Process2019Ingår i: METALS, ISSN 2075-4701, Vol. 9, nr 1, artikel-id 101Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    IronArc is a newly developed technology and an emerging future process for pig iron production. The long-term goal with this technology is to reduce the CO2 emissions and energy consumption compared to existing technologies. The production rate of this process is dependent on the stirring, which was investigated in the pilot plant process by measuring the mixing time in the slag bath. Moreover, slag investigations were done both based on light optical microscope studies as well as by Thermo-Calc calculations in order to determine the phases of the slag during operation. This was done because the viscosity (which is another important parameter) is dependent on the liquid and solid fractions of the slag. The overall results show that it was possible to determine the mixing time by means of the addition of a tracer (MnO2 powder) to the slag. The mixing time for the trials showed that the slag was homogenized after seconds. For two of the trials, homogenization had already been reached in the second sample after tracer addition, which means <= 8 s. The phase analysis from the slag indicated that the slag is in a liquid state during the operation of the process.

  • 12.
    Bölke, Kristofer
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Ersson, Mikael
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Imris, Matej
    ScanArc Plasma Technol AB, SE-81321 Hofors, Sweden..
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Importance of the Penetration Depth and Mixing in the IRONARC Process2018Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 58, nr 7, s. 1210-1217Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    One of the most important parameters for gas injection into liquid baths is the penetration depth of the gas into the bath. This is due to that it strongly influences the flow structure and hence the stirring and plume behavior in metallurgical processes. The IRONARC process is a new energy efficient process for reduction of iron oxide to produce pig iron. The future goal is to continuously scale up the process to an industrial scale from the current pilot scale. In this process, gas is injected horizontally through a submerged nozzle into a slag bath. Hence, the penetration depth is of great importance since it greatly affect several parameters in this process. Moreover, this information is essential when scaling up the reactor from a pilot scale to an industrial scale. In this work, the penetration depth of gas injection into water in a small scale side blown converter was studied numerically. Two different approaches with different multiphase models were tested, namely the Volume of Fluid (VOF) model and Eulerian multiphase model (EE). The penetration depth could be accurately determined for both numerical models, with a small expected deviation of 13.9% from the physical experiment results. Also, the simulation time was shorter for the Eulerian multiphase model. The penetration depth was then determined for the IRONARC pilot plant process. The results show that the plume is detached from the nozzle wall, which in turn results in a better energy usage of the gas along with a small refractory wear.

  • 13.
    Bölke, Kristofer
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Ersson, Mikael
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Ni, Peiyuan
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Swartling, Maria
    ScanArc Plasma Technol AB, SE-81321 Hofors, Sweden..
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Physical Modeling Study on the Mixing in the New IronArc Process2018Ingår i: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 89, nr 7, artikel-id 1700555Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    IronArc is a newly developed technology for pig iron production with the aim to reduce the CO2 emission and energy consumption, compared to a conventional blast furnace route. In order to understand the fluid flow and stirring in the IronArc reactor, water modeling experiments are performed. Specifically, a down scaled acrylic plastic model of the IronArc pilot plant reactor is used to investigate the mixing phenomena and gas penetration depth in the liquid bath. The mixing time is determined by measuring the conductivity in the bath, after a sodium chloride solution is added. Moreover, the penetration depth is determined by analyzing the pictures obtained during the experimental process by using both a video camera and a high speed camera. The results show that the bath movements are strong and that a circular movement of the surface is present. The mixing in the model for the flow rate of 282 NLmin(-1) is fast. Specifically, the average mixing times are 7.6 and 10.2s for a 95% and a 99% homogenization degree, respectively. This is 15% and 18% (per degree of homogenization) faster compared to the case when using 3 gas inlets and the same flow rate.

  • 14.
    Carlsson, Leo
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Using Multilayer Perceptrons asmeans to predict the end-pointtemperature in an Electric ArcFurnace2015Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
  • 15.
    Carlsson, Leo
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Samuelsson, Peter
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Predicting the Electrical Energy Consumption of Electric Arc Furnaces Using Statistical Modeling2019Ingår i: METALS, ISSN 2075-4701, Vol. 9, nr 9, artikel-id 959Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    Statistical modeling, also known as machine learning, has gained increased attention in part due to the Industry 4.0 development. However, a review of the statistical models within the scope of steel processes has not previously been conducted. This paper reviews available statistical models in the literature predicting the Electrical Energy (EE) consumption of the Electric Arc Furnace (EAF). The aim was to structure published data and to bring clarity to the subject in light of challenges and considerations that are imposed by statistical models. These include data complexity and data treatment, model validation and error reporting, choice of input variables, and model transparency with respect to process metallurgy. A majority of the models are never tested on future heats, which essentially renders the models useless in a practical industrial setting. In addition, nonlinear models outperform linear models but lack transparency with regards to which input variables are influencing the EE consumption prediction. Some input variables that heavily influence the EE consumption are rarely used in the models. The scrap composition and additive materials are two such examples. These observed shortcomings have to be correctly addressed in future research applying statistical modeling on steel processes. Lastly, the paper provides three key recommendations for future research applying statistical modeling on steel processes.

  • 16.
    Cendekia, Bintang Bergas
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi. KTH Royal Institute of technology.
    The Effect of Electromagnetic Stirring and Flow Control Devices on Eight-Strand Tundish Performance2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The strand similarity and inclusion removal capability are two critical parameters to measure the performance of multi-strand tundish in clean steel production. In this work, the effect of two flow regulators, i.e., Flow Control Devices (FCD) and Electromagnetic Stirring (EMS) on eight-strand tundish performance have been investigated by establishing a water model and conducting numerical simulations of water model. The water model was focused on revealing the effect of stirring while the simulation was employed to investigate the effect of two FCDs, namely baffle wall and turbo-stopper. The analysis of strand similarity and inclusion removal were conducted by analyzing flow characteristics derived from Combined Model of Residence Time Distribution (RTD) curve and observing the flow movement in the tundish model. In addition, the tundish capability to remove inclusions was also studied by injecting inclusion particles using Discrete Phase Model (DPM) in ANSYS Fluent. Experiment results cause the Combined Model needs to be modified. This modification was employed when analyzing tundish configuration involving stirring. By using the modified Combined Model, the stirring can significantly increase the well-mix volume to almost 100% as it annihilates dead zone. The stirring also increases the similarity between strands and makes the RTD curve more similar to ideal mixing curve.  However, the problem of short-circuiting flow need to be solved and care should be taken into consideration regarding the selection of stirring direction as well as bath surface condition when implementing EMS in reality. The simulation results show that the addition of baffle wall and turbo-stopper are beneficial to improve mixing as well as to avoid the short-circuiting flow. Furthermore, compared to individual FCD, the combination of baffle wall and turbo-stopper results in the best performance to remove inclusions by providing surface-directed flow and generating a higher plug flow.

  • 17.
    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.

  • 18.
    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.

  • 19. Dhindaw, B. K.
    et al.
    Kumar, L.
    Alkarkhi, N. C. Amer
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Microstructure development and solute redistribution in aluminium alloys under low and moderate shear rates during rheo processing2005Ingår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 413, s. 156-164Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Microstructural features and microsegregational behaviour of solute are studied in shear or stir-cast aluminium alloys under low and moderate shear rates. Alloys studied are Al-6.2% Cu, Al-7.3% Si and Al-13.2% Mg. In all the cases, microstructures of the primary pre-quench solid for stir-cast samples show rosette or ellipsoidal morphologies. Volume fractions of pre-quenched solid phase show significantly higher values for stir-cast alloys as compared to calculated. Microsegregation studies by microprobe analysis along the grains of the samples solidified under different treatment conditions show that stir casting changes the segregation pattern significantly. Except for Al-13.2% Mg alloys lower values than those calculated by Scheil's microsegregation equation are observed for other systems. A model for microstructure evolution during stir casting is presented. The microsegregation patterns have been discussed in terms of interaction between the diffusing solute and the vacancies migrating from solid into liquid.

  • 20.
    Du, Hongying
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Karasev, Andrey
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Sundqvist, Olle
    Sandv Mat Technol AB, S-81181 Sandviken, Sweden..
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Modification of Non-Metallic Inclusions in Stainless Steel by Addition of CaSi2019Ingår i: METALS, ISSN 2075-4701, Vol. 9, nr 1, artikel-id 74Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The focus of this study involved comparative investigations of non-metallic inclusions in 316L stainless steel bars without and with Ca treatments. The inclusions were extracted by using electrolytic extraction (EE). After that, the characteristics of the inclusions, such as morphology, size, number, and composition, were investigated by using a scanning electron microscope (SEM) in combination with an energy dispersive X-ray spectroscopy (EDS). The following four types of inclusions were observed in 316L steels: (1) Elongated MnS (Type I), (2) MnS with hard oxide cores (Type II), (3) Undeformed irregular oxides (Type III), and (4) Elongated oxides with a hard oxide core (Type IV). In the reference sample, only a small amount of the Type III oxides (Al2O3-MgO-MnO-TiOx) existed. However, in Ca-treated 316L steel, about 46% of the observed inclusions were oxide inclusions (Types III and IV) correlated to gehlenite and to a mixture of gehlenite and anorthite, which are favorable for the machinability of steel. Furthermore, untransformed oxide cores (Al2O3-MgO-MnO) were also found in the inclusions of Type IV. The mechanism leading to different morphologies of oxide inclusions is also discussed.

  • 21.
    El-Bealy, Mostafa O.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Air-Water Mist and Homogeneity Degree of Spray Cooling Zones for Improving Quality in Continuous Casting of Steel2011Ingår i: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 82, nr 10, s. 1187-1206Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A theoretical investigation used previous experimental works for validation of model predications and for studying the effect of different nozzle designs on the quality of continuously cast steel slabs has been undertaken. This is by optimizing the homogeneity degree of cooling pattern "HDCP'' between a pair of rolls. The idea behind this technique is to maximize the solid shell resistance against thermo-metallurgical and mechanical stresses and therefore minimizes the defects generated in different cooling zones. A 2-D mathematical model of thermal, solidification, solid shell resistance and cooling conditions has been developed. The model determines the temperature distributions, the different phases associated with the solidification and three phase peritectic reaction L + delta -> gamma of Fe-0.12%C steel alloy as well as isotherms. The effect of different cooling patterns for various spray cooling systems on the homogeneity degree and solid shell resistance are examined. In additional to traditional water and air-water (AWM) nozzles, a new design of air-water mist nozzle has been proposed to improve the homogeneity degree of spray cooling system. The results indicate generally that the increasing in the homogeneity degree of cooling conditions is proportional to the increasing in the solid shell resistance and therefore to the improving of slab quality. Model predications of different effects of different nozzle designs on the surface and inner quality levels are compared and discussed in the mold and secondary spray cooling zones.

  • 22.
    El-Bealy, Mostafa O.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Influence of direct chill casting process variables on surface quality of aluminum alloy sheet ingots2012Ingår i: Light Metals 2012, John Wiley & Sons, 2012, s. 1107-1112Konferensbidrag (Refereegranskat)
    Abstract [en]

    Surface defects formation and their effects on the surface quality of aluminum direct-chill cast sheet ingots have been investigated by metallographic examinations and mathematical modeling. The influence of process variables such as alloy composition, casting speed and lubricant on the surface defects especially extruded surface segregation layer has been determined. The metallographic study for collected samples of plant trials involved visual, micro-examinations and macrosegregation analysis. A 2-D mathematical model has been developed to characterize the thermal, solidification, interdendritic strain and macrosegregation distributions. Also, the model contained a new approach to evaluate qualitatively the macrosegregation formed during dendritic solidification. The model predications were compared to measurements from collected samples to verify the model, where a good agreement was obtained. The model predications illustrate that all the process variables tested have an observed effect on the surface quality by different levels. The mathematical analysis of strain fields as well as metallographic study has been used to explain and discuss the effects of different process variables on the surface quality.

  • 23.
    El-Bealy, Mostafa Omar
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Advanced solute conservation equations for dendritic solidification processes: Part I: Experiments and theory2013Ingår i: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 84, nr 6, s. 565-583Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The macrosegregation formed in dendritic equiaxed structure during early stages of solidification of Al-4.5%Cu alloy has been studied by experimental work and by metallurgical study of cast samples taken from the experimental work. An experimental work was conducted to study the coupled effect of natural convection streams, interdendritic strain and mushy permeability of Al-4.5%Cu aluminum alloy solidified in horizontal rectangular parallelepiped cavity at different superheats. The metallurgical study includes macro-microstructure evaluation, measurements of grain size of equiaxed crystals and macrosegregation analysis. This study shows that the level of surface segregation exhibiting as positive segregation varies with superheat whereas the rest of inner ingot areas show the light fluctuation in segregation values. In addition to experimental work, there is a mathematical study which contains a complete derivation of local solute redistribution equations based on Fleming's approach under different solute diffusion mechanisms in the dendritic solid. This derivation includes also the effects of interdendritic strain and mushy permeability on the local solute redistribution distribution. Owing to the length of the study, it is presented in two parts. The first part describes the experimental work and its results as well as a detail derivation of solute conservation equations. This part also involves comparison and discussion between existing and proposed solute conservation equations. The second part contains the mathematical analyses of a two dimensional mathematical model of fluid flow, heat flow, solidification, interdendritic strain and macrosegregation. Also, this part also contains the numerical simulations by using finite difference technique "FDT" to create convection patterns, heat transfer, interdendritic strain, and macrosegregation distributions. This part also includes comparisons between the available measurements and model predications as well as full discussion of different model simulations. The mechanism of interdendritic strain generation and macrosegregation formation during solidification of dendritic equiaxed structure under different diffusion mechanisms in dendritic solid has also been explained and discussed. Macrosegregation in dendritic equiaxed structure during the early stages of solidification of Al-4.5%Cu alloy has been studied experimentally. The metallurgical study includes macro-microstructure evaluation, measurements of grain size of equiaxed crystals, and macrosegregation analysis. In addition to the experimental work, there is a mathematical study which contains a complete derivation of local solute redistribution equations based on Fleming's approach under different solute diffusion mechanisms in the dendritic solid.

  • 24.
    El-Bealy, Mostafa Omar
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Advanced solute conservation equations for dendritic solidification processes part II: Numerical simulations and comparisons2013Ingår i: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 84, nr 6, s. 584-606Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The mathematical model of derived solute equations in part I for equiaxed dendritic solidification with melt convection streams and interdendritic thermo-metallurgical strain is applied numerically to predict macrosegregation distributions with different diffusing mechanisms in dendritic solid. Numerical and experimental results are present for solidification of a Al-4.5% Cu alloy inside horizontal rectangular cavity at different superheats. The numerical simulations were performed by using simpler method developed by Patanker. The experiments were conducted to measure the cooling curves via thermocouples and the metallurgical examinations to measure the grain size and macrosegregation distributions in Part I. Preliminary validity of the model is demonstrated by the qualitative and quantitative agreements between the measurements and predications of cooling curves and predicted macrosegregation distributions including mushy permeability and interdendritic strain. In addition, several important features of macrosegregation in equiaxed dendritic solidification are identified through this combined experimental and numerical study. Also, quantitative agreements between the numerical simulations and experiments reveal several areas for future research work. The differences and errors between predicted macrosegregation results under different diffusing mechanisms have been discussed. The mathematical model of derived solute equations in Part I for equiaxed dendritic solidification with melt convection streams and thermal is applied numerically to predict macrosegregation distributions with different diffusing mechanisms in dendritic solid. Numerical and experimental results are present for solidification of a Al-4.5% Cu alloy inside horizontal rectangular cavity at different superheats.

  • 25.
    El-Bealy, Mostafa Omar
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Insulated sprayed roll technique "ISRT" and solid shell resistance of inner quality of continuously cast steel slabs2011Ingår i: Mater. Sci. Technol. Conf. Exhib., MS T, 2011, s. 743-750Konferensbidrag (Refereegranskat)
    Abstract [en]

    In order to get a better inner quality of continuously cast steel slabs, insulated sprayed roll technique by using a ceramic material has been developed to increase the slab thermo-mechanical rigidity against the thermo-mechanical stresses. The idea behind this technique is to increase the slab solid shell resistance "Ic" by optimizing the homogeneity of cooling conditions between a pair of rolls. This is by minimizing a rapid fluctuation in the surface temperature between rolls especially at roll contact area. The mathematical model of thermal, solidification, solid shell resistance and cooling conditions has been developed. The model predications indicate that the increasing in the thickness of this layer "δC" or decreasing its thermal conductivity "κC" is proportional to decreasing the surface temperature peak at roll contact area. The predications also point out that the improving of the solid shell resistance depends on the optimum selection of δC and κC with cooling conditions between rolls. Also, the predications were used to explain and discussed the mechanism of characteristics of insulated layer with Ic and thermo-mechanical rigidity of steel slab. Copyright

  • 26.
    El-Bealy, Mostafa Omar
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    On the formation of interdendritic cracking phenomena in direct chill casting of aluminum alloy slabs2008Ingår i: TMS Light Met., 2008, s. 721-725Konferensbidrag (Refereegranskat)
    Abstract [en]

    The formation of interdendritic crack of continuously cast aluminum alloy slabs has been studied by macrosegegation analysis of cast samples and by performing a set of mathematical analyses of heat flow, solidification, interdendritic strain and interdendritic cracking criteria. The study has revealed that the interdendritic cracking phenomena depends mainly on the interdendritic coherernt region width and the accumulated interdendritic strain generated due to various cooling conditions during dendritic solidification process. Interdendritic crack is expected in the positive segregation areas where the tensile strain is present. The morphology of this crack depends mainly on the kind, degree and pattern of macrosegregation.

  • 27.
    El-Bealy, Mostafa Omar
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    On the Formation of Interdendritic Internal Cracks During Dendritic Solidification of Continuously Cast Steel Slabs2012Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 43, nr 6, s. 1488-1516Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study of solidification during the continuous casting of steel slabs, the effect of the different spray cooling conditions on the interdendritic internal cracks formed between the columnar dendrites has been examined by a metallographic study of the slab samples and by performing a set of mathematical analyses. The metallographic study involved plant trials to measure the slab surface temperature within different secondary spray cooling conditions. Also, macro/microexaminations of the collected samples from plant trials, measurements of dendrite arm spacing, and interdendritic distance between the columnar dendrites, as well as a segment length of interdendritic crack, have been performed. The experimental results show that the morphology of the interdendritic cracks described by the segment width and length fluctuate with the distance from the slab surface based on the secondary spray cooling conditions. A one-dimensional mathematical model of the heat transfer, solidification, structure evolution, interdendritic strain, and elementary interdendritic area (EIA) has been developed. This model takes into account also calculating the width of interdendritic crack. The model predictions are in a good agreement with the measurements. The results pointed out also that this criterion can be considered as the most important tool to measure the inner quality of the continuously cast steel slabs. Therefore, it helps also to define the required mechanism and reduction level of hot working deformation to close these interdendritic internal cracks. The formation mechanism of these cracks during the dendritic solidification of continuously cast steel slabs has been discussed and the available solutions have been proposed.

  • 28.
    El-Bealy, Mostafa Omar
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    On the Formation of Macrosegregation and Interdendritic Cracks During Dendritic Solidification of Continuous Casting of Steel2014Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 45, nr 3, s. 988-1017Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The aim of the current article is to elucidate the significant effects of macrosegregation distribution and its level on the different stages of interdendritic crack formation during dendritic solidification in continuously cast steel slabs. Couple formations of macrosegregation and interdendritic crack phenomena during dendritic solidification of peritectic carbon steels have been investigated by metallographic study of collected slab samples and by performing a set of mathematical analyses. The metallographic study involved plant trails to measure slab surface temperature of different secondary spray cooling conditions. Also, macro-microexaminations, measurements of dendrite arm spacing, macrosegregation analysis, and interdendritic distance between the dendrites of collected samples from plant trials have been performed. The experimental results show a fluctuation of carbon segregation with respect to distance from slab surface. These results also reveal that the interdendritic cracks vary with this fluctuation in various nano, macro, and microscales based on the cooling conditions. A mathematical model of heat transfer, solidification, structure evolution, interdendritic strain, macrosegregation, and elementary interdendritic area "EIA" has been developed. This model takes also into account the calculating of interdendritic distance between the dendrites "IDD" to evaluate the interdendritic crack width. The model predictions of different thermal and solidification phenomena show a good agreement with measurements. The results pointed out also that the coupled effect of interdendritic strain and macrosegregation phenomena and their distributions can be considered as the most important tools to evaluate the surface and internal interdendritic cracks in continuously cast steel slabs. The formation mechanisms of different types of interdendritic crack with interdendritic strain patterns and fluctuation of macrosegregation levels during various cooling zones have been explained, and the possible solutions to these problems have been discussed.

  • 29.
    El-Bealy, Mostafa Omar
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi. Department of Materials Processing and Technology, ASU, Egypt .
    On the mechanism of mechanical soft reduction and macrosegregation quality criteria of continuous casting of steel2014Ingår i: AISTech - Iron and Steel Technology Conference Proceedings, 2014, Vol. 3, s. 2959-2967Konferensbidrag (Refereegranskat)
    Abstract [en]

    In order to study the central quality of continuously cast tool steel slabs, the mathematical model has been developed to simulate the quality criteria. The model calculates different quality criteria such as average macrosegregation level criterion "ASL", its average fluctuation level "FSV and its average segregation quality number "SQN" of different segregated elements. These criteria were calculated based on the previous measurements in central areas of lower and upper slab sides. These measurements of carbon and sulfur concentrations were performed by chemical analysis technique. The effect of mechanical soft reduction technique "MSR" on the central quality of slab was also examined and studied. The model predications illustrated that this technique affects the centerline quality significantly by different ways based on the casting speed. These predications pointed out also that the macro-segregation quality criteria and their distributions can be considered as the most simple and important tools of steel industries men to explain preventive techniques and formation mechanisms of different defects in slab central area.

  • 30.
    El-Bealy, Mostafa Omar
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Spray cooling pattern and microthermomechanical rigidity criterion for improving inner quality in continuously cast steel slabs2013Ingår i: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 40, nr 3, s. 167-188Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A new concept has been developed to assess, and a new technique developed to improve, the microthermomechanical rigidity of the solidifying shell in the secondary cooling zones during continuous casting of steel. This is to maximise the coherent solid shell resistance 'I-c' against thermometallurgical and mechanical stresses at different levels from meniscus. The idea behind this concept is to optimise the degree of homogeneity of the cooling pattern between a pair of rolls. The effect of the degree of homogeneity of the cooling pattern between a pair of rolls 'HDCP', in different spray cooling zones on the different types of centreline segregates has been investigated. A number of plant trials with two different water cooling patterns between a pair of rolls have been performed. The metallographic investigation contains examinations and measurements of the level of centreline segregates of collected samples. A one dimensional (1D) transient finite difference mathematical model of thermal, solidification, solid shell resistance and cooling conditions has been developed to test the different effects of spray patterns on the microthermomechanical rigidity concept and therefore on the mechanism of centreline macrosegregation level. The results indicate that the increase in the degree of homogeneity of the cooling conditions is proportional to the increase in slab internal microquality. The results show that the degree of homogeneity of the cooling pattern affects centreline macrosegregation significantly. This depends significantly on the degree of homogeneity of cooling pattern between a pair of rolls, its location from the meniscus and, generally, on the increase microthermomechanical rigidity concept.

  • 31.
    Eliasson, Anders
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Keramteknologi.
    Ekbom, L.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Tungsten grain separation during initial stage of liquid phase sintering2008Ingår i: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 51, nr 4, s. 343-349Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The initial stage, the first few seconds of liquid phase sintering has been investigated in experiments using a tungsten heavy alloy with low tungsten content. The heavy alloy has been melted in a temperature gradient for short periods, similar to 9 s in an ellipsoid mirror furnace. During the liquid phase sintering at about 1470 degrees C, a penetration followed by a remarkably rapid separation and dispersion of the tungsten grains by the molten matrix occur. The suggested explanation for this grain separation and dispersion is based on the effect of composition gradients in the liquid matrix and a theory based on interagglomerate melt swelling due to a Kirkendall effect.

  • 32.
    Eliasson, Anders
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Interaction behaviour between alumina particles and solidification front and particle behaviour in iron based alloys at deoxidation by Kirkendall effect2007Ingår i: International Journal of Cast Metals Research, ISSN 1364-0461, E-ISSN 1743-1336, Vol. 20, nr 3, s. 127-130Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The present paper deals with interaction phenomena by particles in liquid metals. The interpretation is to make an initial analysis how the model by Kirkendall, for diffusion phenomena in solids, can be used for the analysis of particle behaviour in liquids. Whenever there is an unequal solutal field, insoluble particles may 'move' due to concentration gradients in the liquid and a difference of diffusion rates of the solute atoms. The analysis deals with the following melt/particles interactions: one is the interaction behaviour between the solidification front and the formed slag oxide particles of Al2O3 and the critical velocity for pushing/engulfment at the interface and the other is the movement and clustering of precipitated alumina inclusions around SiO2 or FeO inclusions formed in a steel melt before deoxidation. Despite the uncertainty of the used material constants and the assumed concentration profiles, the results of the present study are in accordance with some shown experimental particle movements.

  • 33.
    Emi, Toshihiko
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Improving steelmaking and steel properties2005Ingår i: Fundamentals of Metallurgy, Elsevier Inc. , 2005, s. 503-554Kapitel i bok, del av antologi (Övrigt vetenskapligt)
  • 34.
    Emi, Toshihiko
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    High-speed continuous casting of peritectic carbon steels2005Ingår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 413, s. 2-9Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Productivity of an integrated steel plant is improved by high-speed casting of hypo-peritectic steels that makes the productivity of caster meet basic oxygen furnace. In high-speed casting, however, strands of the steels tending to form cracks on the shell in the mold, require off-line conditioning that limits the plant productivity and premium yield. Hypo-peritectic transformation occurring on solidification in mold results in irregular shell-surface roughness that causes non-uniform heat transfer to the mold, causing local lifting of the shell from the mold, recalescence, and surface cracks. Influential factors are summarized on the development of the surface roughness, the non-uniform heat transfer and the decline of mechanical properties of the shell upon recalesce. Effective means are presented to reduce the non-uniformity and the cracks at high casting speeds by controlling the properties of mold flux film infiltrating into the solidifying shell/mold boundary.

  • 35.
    Ersson, Mikael
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Colocated pressure-velocity coupling in finite difference methods2019Ingår i: Progress in Computational Fluid Dynamics, An International Journal, ISSN 1468-4349, E-ISSN 1741-5233, Vol. 19, nr 5, s. 273-281Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A simple method to be used for colocated pressure-velocity coupling in incompressible flows is presented with a full derivation. A number of standard test cases are shown that demonstrate the ability of the method to produce accurate results. The method avoids spurious pressure oscillations while keeping the pressure Poisson equation stencil compact. This is obtained by discretising the continuity and pressure derivatives with first order differences with opposite directions, i.e., backward difference for continuity and forward difference for pressure (BCFP). The equations are also approximated using a forward difference for continuity and a backward difference for pressure (FCBP). In order to obtain a second order approximation the mean between BCFP and FCBP is used, i.e., a central difference. The paper gives a useful alternative to existing methods for pressure-velocity coupling in finite difference methods in which a staggered arrangement is not desirable.

  • 36. Formenti, A.
    et al.
    Eliasson, Anders
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Keramteknologi.
    Mitchell, A.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Solidification sequence and carbide precipitation in Ni-base superalloys IN718, IN625 AND IN9392005Ingår i: High Temperature Materials and Processes, ISSN 0334-6455, E-ISSN 2191-0324, Vol. 24, nr 4, s. 239-258Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Differential Thermal Analysis (DTA) and Directional Solidification and Quenching (DSQ) were used to evaluate the solidification and precipitation sequence for the Ni-base superalloys IN718, IN625 and IN939. They all showed a similar precipitation sequence, with an initial precipitation of gamma dendrites, followed by an intermediate non-invariant divorced eutectic reaction of type L -> gamma + MC, and a final eutectic precipitation of Laves phase for alloy IN718 and IN625 and of eta-phase for alloy IN939. The reaction temperatures and the amounts of carbides and of final precipitates were evaluated. Precipitated nitrides were found to act as nucleation sites for the precipitation of blocky carbides/carbonitrides, at low interdendritic supersaturation, while in interdendritic regions with high supersaturation, a 'script-like' carbide formation was found instead.

  • 37.
    Formenti, Angelo
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Eliasson, Anders
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Keramteknologi.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    On the dendritic growth and microsegregation in Ni-base superalloys IN718, IN625 and IN9392005Ingår i: High Temperature Materials and Processes, ISSN 0334-6455, E-ISSN 2191-0324, Vol. 24, nr 4, s. 221-238Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Directional Solidification and Quenching (DSQ) has been used to analyse the solidification, segregation and precipitation behaviour of the Ni-base alloys IN718, IN625 and IN939. The microsegregation in the primary solidified gamma-phase was analysed by Energy Dispersive Spectroscopy (EDS) and were mainly found to be Nb for alloy IN718 and Ti for alloy IN939. The microsegregation behaviour were analysed by numerical back diffusion models and it was found that the diffusion rate in the samples was higher than expected from the theory. A suggested explanation was that this was an effect of the formation of lattice defects during the solidification process. The coarsening process that occurs during the further cooling of the samples is proved to be by the mechanism of back diffusion i.e. the smaller secondary dendrite arms grow together with the thicker ones into a plate.

  • 38.
    Fredriksson, Hasse
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Fredriksson, E.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    A model of liquid metals and its relation to the solidification process2005Ingår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 413, s. 455-459Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    X-ray analysis shows that a liquid is build up of clusters of atoms with a certain number of nearest neighbours. The X-ray analysis shows that 8-11 nearest neighbours surround each atom. Each cluster has a crystal-like structure. Between the clusters there are some free atoms and free electrons. The enthalpy of fusion is according to Richard's rule around the gas constant times the temperature of melting and the heat capacity in the liquid state is normally constant and for some metals lower than that in the solid state. For metals with low melting points it will decrease further with increasing temperature. This behaviour of the metals can be explained by the use of statistical mechanics and by assuming that the clusters, observed by X-ray analysis are rotating around a centre of its mass. The cluster model is applied to explain the diffusion rate in liquid metals. The effect of the experimental set upon measurements of diffusion constants is discussed as well as its effect on crystal growth.

  • 39.
    Fredriksson, Hasse
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Haddad-Sabzevar, M.
    Hansson, K.
    Kron, J.
    Theory of hot crack formation2005Ingår i: Materials Science and Technology, ISSN 0267-0836, E-ISSN 1743-2847, Vol. 21, nr 5, s. 521-529Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The hot crack sensitivity in metals is suggested to be caused by the supersaturation of vacancies created during the solidification process. Equations have been derived to predict the nucleation and growth of cracks by the condensation of vacancies. The transition temperature from brittle to ductile fracture was found to be related to the decrease in the supersaturation of vacancies due to an annealing process. The hot crack sensitivity was observed to be related to the supersaturation of vacancies, the diffusion rate, and the structure coarseness. The effect of surface active elements such as phosphorous and sulphur in steel alloys is discussed.

  • 40.
    Fredriksson, Hasse
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Stjerndahl, J.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Tinoco, J.
    On the solidification of nodular cast iron and its relation to the expansion and contraction2005Ingår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 413, s. 363-372Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Directional solidification and quench-out thermal analysis experiments have been performed in Mg-treated cast iron alloys. The volume fraction of liquid, allstenite and graphite was evaluated. It was observed that the volume fraction of austenite is much larger than expected from the equilibrium phase diagram at the beginning of the solidification process. It was also been observed that the last melt solidifies far below the equilibrium eutectic temperature. The solidification process was analyzed by non-equilibrium thermodynamic models. The theoretical treatment was supported by the observation that the latent heat decreases during the solidification process. The formation of small pores was observed at the very end of the solidification. An explanation for the formation of the small pores is given in terms of a vacancies creep model. The formation of macropores was related to the large fraction of austenite formed during the first part of the solidification process.

  • 41.
    Gharehbaghi, Ali
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Precipitation Study in a High Temperature Austenitic Stainless Steel using Low Voltage Energy Dispersive X-ray Spectroscopy2012Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Precipitation of second phase particles is a key factor dominating the mechanical properties of high temperature alloys. In order to control and optimize the precipitation effect it is of great importance to study the role of alloying elements in the formation and stability of precipitates. As a favored family of corrosion and creep resistant austenitic stainless steels the 20Cr-25Ni alloy was modified by addition of copper, molybdenum, nitrogen, niobium and vanadium. A set of alloys with similar matrix but varying contents of niobium, vanadium and nitrogen were prepared. Sample preparation process included melting, hot forging, solution annealing and finally aging for 500 h at 700, 800 and 850 ºC.Light optical and scanning electron microscopy revealed micron-scale precipitates on grain and twin boundaries as well as sub-micron intragranular precipitates in all samples. Characterization of precipitates was carried out by means of energy dispersive X-ray spectroscopy (EDS). Among micron-scale precipitates M23C6 carbide was the dominant phase at 700 ºC aging temperature; whereas silicon-rich eta phase (M5SiC) was the main precipitate in samples aged at 800 and 850 ºC. A few sigma phase particles were found in one of the niobium containing samples aged at 700 and 800 ºC. Sub-micron intragranular precipitates were analyzed using low voltage EDS. The spatial resolution of EDS microanalysis at 5 kV accelerating voltage was estimated as almost 100 nm which was at least eight times better than that using the ordinary 20 kV voltage. Also, low voltage EDS revealed the presence of light elements (carbon, nitrogen and boron) in the composition of sub-micron particles thanks to the less matrix effect in absorption of low energy X-rays of light elements. In samples aged at 700 ºC niobium-rich and vanadium-rich carbonitrides were found as the dominant precipitates; whereas they contained much less carbon in samples aged at 800 ºC and mostly became carbon-free nitrides with well-defined cuboidal shapes at 850 ºC aging temperature. This showed that niobium/vanadium-rich nitride phases are stable precipitates at aging temperatures above 700 ºC.The drawbacks of low voltage EDS were indicated as high detection limit (no detection of low- content elements), poor accuracy of quantitative analysis and high sensitivity to surface contamination. Some possible ways to improve the accuracy of low voltage EDS, e.g. longer acquisition time were examined and some other suggestions are proposed for future works.

  • 42.
    Gharehbaghi, Ali
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Precipitation Study in a High Temperature Austenitic Stainless Steel using Low Voltage Energy Dispersive X-ray Spectroscopy2012Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Precipitation of second phase particles is a key factor dominating the mechanical properties of high temperature alloys. In order to control and optimize the precipitation effect it is of great importance to study the role of alloying elements in the formation and stability of precipitates. As a favored family of corrosion and creep resistant austenitic stainless steels the 20Cr-25Ni alloy was modified by addition of copper, molybdenum, nitrogen, niobium and vanadium. A set of alloys with similar matrix but varying contents of niobium, vanadium and nitrogen were prepared. Sample preparation process included melting, hot forging, solution annealing and finally aging for 500 h at 700, 800 and 850 ºC.

    Light optical and scanning electron microscopy revealed micron-scale precipitates on grain and twin boundaries as well as sub-micron intragranular precipitates in all samples. Characterization of precipitates was carried out by means of energy dispersive X-ray spectroscopy (EDS). Among micron-scale precipitates M23C6 carbide was the dominant phase at 700 ºC aging temperature; whereas silicon-rich eta phase (M5SiC) was the main precipitate in samples aged at 800 and 850 ºC. A few sigma phase particles were found in one of the niobium containing samples aged at 700 and 800 ºC. Sub-micron intragranular precipitates were analyzed using low voltage EDS. The spatial resolution of EDS microanalysis at 5 kV accelerating voltage was estimated as almost 100 nm which was at least eight times better than that using the ordinary 20 kV voltage. Also, low voltage EDS revealed the presence of light elements (carbon, nitrogen and boron) in the composition of sub-micron particles thanks to the less matrix effect in absorption of low energy X-rays of light elements. In samples aged at 700 ºC niobium-rich and vanadium-rich carbonitrides were found as the dominant precipitates; whereas they contained much less carbon in samples aged at 800 ºC and mostly became carbon-free nitrides with well-defined cuboidal shapes at 850 ºC aging temperature. This showed that niobium/vanadium-rich nitride phases are stable precipitates at aging temperatures above 700 ºC.

    The drawbacks of low voltage EDS were indicated as high detection limit (no detection of low- content elements), poor accuracy of quantitative analysis and high sensitivity to surface contamination. Some possible ways to improve the accuracy of low voltage EDS, e.g. longer acquisition time were examined and some other suggestions are proposed for future works.

  • 43. Gorkusha, D. V.
    et al.
    Grigorovich, K. V.
    Karasev, Andrey
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Komolova, O. A.
    Content modification of different types of nonmetallic inclusions during low-carbon if steel ladle treatment2019Ingår i: Izvestiya Ferrous Metallurgy, ISSN 0368-0797, Vol. 62, nr 5, s. 345-352Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Development of advanced materials for the automotive industry allows us to produce a lighter body without losing strength characteristics of the structure. It became possible by the creation and subsequent introduction into the production of such steel grades as IF (Interstitial Free)-steel with no interstitial solute atoms to strain the solid iron lattice and IF-BH (Bake Hardening)-steel with hardening during hot drying. The article provides a brief overview of the history of the emergence of IF steel and the current situation in the production of it in Russia. One of the quality criteria for steels of IF grades is purity of the metal by non-metallic inclusions (NMI), which negatively affect the plastic properties of the material, lead to the formation of surface defects of flat rolled products and reduce the manufacturability due to a decrease in the casting speed of steel, as they cause overgrowing of steel casting nozzles. The article presents investigation results of the content, composition, size and morphology of non-metallic inclusions (NMI) in the metal samples taken at all stages of ladle treatment and casting of IF steel grade production using quantitative metallographic analysis, electrochemical dissolution (ED) followed by X-ray microanalysis of isolated inclusions, Auger electron spectroscopy and fractional gas analysis (FGA). As a result of the analysis of inclusions in the studied samples using a scanning electron microscope, according to morphological features, five characteristic types of inclusions were identified, which reduce the performance properties and strength characteristics of the materials produced from them. Results of the analysis of nonmetallic inclusions in metal samples obtained by the ED method are in good agreement with the results of the determination of oxide nonmetallic inclusions by the FGA method. The method of fractional gas analysis shows the dynamics of changes in the content of various types of oxide nonmetallic inclusions during the secondary (ladle) treatment of steel. It is shown that application of the FGA me­ thod allows to make analysis of causes of the harmful NMI formation in the metal and to correct operations at ladle treatment.

  • 44.
    Hailom Yosef, Futsum
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    On the peritectic reaction of iron based binary alloys2005Rapport (Övrigt vetenskapligt)
  • 45.
    Hulme-Smith, Christopher
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi. Univ Cambridge, Dept Mat Sci & Met, 27 Charles Babbage Rd, Cambridge CB3 0FS, England..
    Ooi, S. W.
    Univ Cambridge, Dept Mat Sci & Met, 27 Charles Babbage Rd, Cambridge CB3 0FS, England..
    Bhadeshia, H. K. D. H.
    Univ Cambridge, Dept Mat Sci & Met, 27 Charles Babbage Rd, Cambridge CB3 0FS, England..
    Intermetallic-strengthened nanocrystalline bainitic steel2018Ingår i: Materials Science and Technology, ISSN 0267-0836, E-ISSN 1743-2847, Vol. 34, nr 16, s. 1976-1979Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A new thermally stable, nanocrystalline bainitic steel has been developed, rich in nickel and aluminium. During tempering, it is expected that a significant quantity of intermetallic precipitates will form. This was confirmed by X-ray diffractometry, scanning transmission electron microscopy, Fourier transform analysis of atomic column images, energy dispersive X-ray spectroscopy and selected area electron diffraction. These are the first intermetallics to be produced in a nanocrystalline bainitic steel.

  • 46.
    Hulme-Smith, Christopher
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi. University Of Cambridge.
    Pickering, Ed
    University of Cambridge.
    Steeling the Show2012Ingår i: The Naked Scientists: Science Articles and FeaturesArtikel, forskningsöversikt (Övrig (populärvetenskap, debatt, mm))
  • 47. Iwnicki, S. D.
    et al.
    Orlova, A.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Fartan, M.
    Design of the running gear for the SUSTRAIL freight vehicle2015Ingår i: Stephenson Conference Research for Railways 2015, Institution of Mechanical Engineers , 2015, s. 299-305Konferensbidrag (Refereegranskat)
    Abstract [en]

    The authors are working together in the 'SUSTRAIL' project to design an innovative, sustainable freight vehicle for use in new European markets. Market research has determined that the SUSTRAIL freight vehicle needs to run at up to 140km/h with an axle load of up to 25T. In order to reduce the impact of the increased freight traffic a requirement for a 50% reduction in lateral forces on the track has also been set. These very demanding requirements can not be met without a corresponding step change in suspension design. After a thorough review it was therefore decided that the conventional Y25 type suspension was not appropriate for the SUSTRAIL freight vehicle. The Y25 suspension is very common in European railway operations and this brings advantages for operation and maintenance however it does have a high level of longitudinal stiffness after the small amount of longitudinal clearance at the axle box has been exceeded and this can result in relatively poor curving and high lateral wheel-rail forces. As an alternative a modified version of the Y25 suspension with a double Lenoir link primary suspension has been investigated and shown to produce much lower longitudinal primary stiffness while still utilizing standard components and methods which are well established within the railway industry. Computer simulation tools have been used by the project team to optimize the precise geometric design and the component parameters. In order to improve stability of the vehicle and allow higher speed operation it was decided to assess the benefit of linkages providing longitudinal stiffness between the axleboxes using a radial arm. Various previous designs were considered and the final proposal involves a novel cross bracing arrangement. A prototype SUSTRAIL freight vehicle is now being constructed and will be tested in 2015. 

  • 48.
    Jaradeh, Majed
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Carlberg, Torbjörn
    Analysis of solidification in a Bridgman furnace as a simulation of DC casting of aluminium alloy slabs2007Ingår i: Materials Science and Technology, ISSN 0267-0836, Vol. 23, nr 4, s. 475-482Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The vertical Bridgman directional solidification equipment has been used in several investigations to simulate direct chill casting of wrought aluminium alloys. As a basis for such investigations and alloy developments, it is important to have an understanding of the performance of the furnace used during simulation of the casting conditions. In this investigation the thermal conditions in the furnace have been analysed in detail, both by measurements and by mathematical modelling. The growth characteristics of the furnace, such as gradient, growth rates and cooling rates have been compared to conditions in large ingots. The direct chill casting conditions, which the simulations have been compared to, are casting of slabs of 330 and 600 mm thickness of an aluminium AA3003 type alloy. The results show that the experiments are able to simulate the cooling conditions in the ingots except from the surface zone. Comparisons of the microstructures have been made and a good agreement has been obtained for structure parameters such as grain size and DAS.

  • 49.
    Jonnalagadda, Krishna Praveen
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Influence of Graphite type on copper diffusion in P/M copper steels2012Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    One main reason for the use of Fe-Cu-C system in PM industry is the presence of liquid phase (copper) at the start of sintering (1120oC). The diffusion of liquid copper into iron causes swelling in the structure. This in turn can cause high dimensional change and, if not controlled properly, may cause distortion. So it is of paramount importance to control the copper diffusion. Carbon, added as graphite, reduces the swelling of copper by changing the dihedral angle. The affect of graphite on copper diffusion depends on the graphite type, particle size of graphite and heating rate. The aim of this work was to find the influence of graphite type and particle size of graphite on copper diffusion. Water Atomized iron (ASC100.29) produced in Höganäs AB was taken as the base powder.  Two types of graphite were used each with two different particle sizes. Two different graphite quantities (0.2% & 0.8%) for each type was taken. Natural fine graphite (UF4), Natural coarse graphite (PG44), Synthetic fine graphite (F10) and  Synthetic coarse graphite (KS44) were the graphites used in this work. Powders were compacted at 600 Mpa and the sintering was done at 1120oC for 30 minutes in 90/10 N2/H2. Dilatometry and metallographic investigation of the samples sintered in the production furnace were used to understand the graphite influence.

     

    The investigation showed that at low graphite levels (0.2%), the affect of graphite type or graphite size was not significant on copper diffusion. At high graphite levels (0.8%),  synthetic graphites were more effective in reducing the swelling of copper. Influence of  particle size of synthetic graphites on Cu diffusion was not significant compared to the influence of particle size of natural graphite. There was also a considerable affect of heating rate on graphite dissolution and copper swelling.

     

     

  • 50.
    Karasev, Andrey
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Alekseeva, E.
    Lukianov, A.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Characterization of non-metallic inclusions in corrosion -resistance nickel - Based EP718 and 718 alloys by using electrolytic extraction method2019Ingår i: E3S Web of Conferences, EDP Sciences , 2019Konferensbidrag (Refereegranskat)
    Abstract [en]

    It is known that non-metallic inclusions (NMI) that are formed during steel production and heat treatment can significantly affect the properties of final steel products. Therefore, it is very important to be able to determine the content of harmful NMI in steels. Nickel-based alloys are widely used in the oil and gas recovery industry, due to a good combination of strength and corrosion properties. Earlier studies have shown that the corrosion properties in immersion test and electrochemical tests for Ni-based EP718 alloys are slightly lower than that for 718 alloys. The focus in this study was the influence of different NMI on the corrosion resistance of these alloys. The characteristics of inclusions (such as size, morphology, and chemical composition) were analysed by using the electrolytic extraction method followed by three-dimensional investigations using SEM in combination with EDS. It was found that some non-metallic inclusions in EP718 alloys significantly reduce its corrosion resistance. It was also shown that a primary dissolution of the metal matrix occurs around certain inclusions during electrolytic extraction. Based on obtained results, the corrosion active non-metallic inclusions can be determined in these Nickel-base alloys and some recommendations for optimization of their production technology can be formulated.

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