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  • 101. Hörnström, Sven Erik
    et al.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Material Science.
    van Ooij, Wim. J.
    Zhang, J.
    Characterisation of Thin Films of Organofunctional and Non-Functional Silanes on 55Al-43.4Zn-1.6Si Alloy Coated Steel1997In: ECASIA 97, Gothenburg, Sweden, 1997Conference paper (Refereed)
  • 102. Hörnström, Sven-Erik
    et al.
    Karlsson, Erik
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Bay, Niels
    Losch, Achim
    Forming of high strength steels using a hot-melt lubricant2008In: Best in Class Stamping, IDDRG, Olofström, Sweden, 2008Conference paper (Refereed)
  • 103. Ingemarsson, L.
    et al.
    Halvarsson, M.
    Engkvist, Josefin
    Dalarna University, School of Technology and Business Studies, Material Science.
    Jonsson, T.
    Hellstrom, K.
    Johansson, L. -G
    Svensson, J. -E
    Oxidation behavior of a Mo (Si, Al)(2)-based composite at 300-1000 degrees C2010In: Intermetallics (Barking), ISSN 0966-9795, E-ISSN 1879-0216, Vol. 18, no 4, p. 633-640Article in journal (Refereed)
    Abstract [en]

    The oxidation behavior of a Mo (Si,Al)(2)-based composite of Mo(Si,Al)(2), Al2O3 and Mo-5(Si,Al)(3) (Kanthal Super ER) in synthetic air was investigated. The samples were oxidized isothermally for up to 72 h at 300-1000 degrees C using a thermobalance. The microstructure was analyzed by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Auger Electron Spectroscopy (AES) depth profiling. Broad ion beam milling (BIB) was used to prepare cross-sections. Oxidation behavior depended strongly on the composition of the substrate which consisted of a Mo(Si,Al)(2) matrix and the minority phases Mo-5(Si,Al)(3) and Al2O3. At 300-500 degrees C the mass gains were small with parabolic kinetics, oxidation resulting in a mixture of oxides that reflects the substrate composition. At 600 and 700 degrees C the oxide scale is thin and protective and depleted in molybdenum, a mass loss occurring due to MoO3 vaporization. At 1000 degrees C a protective alpha-alumina scale forms. (C) 2009 Elsevier Ltd. All rights reserved.

  • 104.
    Jaisi, Rajesh
    Dalarna University, School of Technology and Business Studies, Material Science.
    Synthesis of Photosensitive Cross Linking Polymer2003Independent thesis Advanced level (degree of Master (Two Years))Student thesis
  • 105.
    JANSSON, CLAS
    Dalarna University, School of Technology and Business Studies, Material Science.
    Analys av sänksmidning av vevstake: Analysis of closed-die forging of connecting rod2007Independent thesis Basic level (degree of Bachelor)Student thesis
    Abstract [sv]

    På Auto Verdi i Smedjebacken tillverkas vevstakar genom sänksmidning för tävlingsbruk. Smidningsprocessen sker vid 1150°C och i två steg. Vevstaken genomgår sedan skäggning, blästring och härdning till 40 HRC(hårdhet av typ Rockwell C). Efterföljande operationer består av maskinbearbetning. Simuleringsresultaten visar hur materialet har påverkats efter smidningen. Mikrostrukturanalys görs med LOM i bl.a. tre valda snitt på sänksmidd vevstake och jämförs med resultaten från simuleringen i liknande områden. Simuleringen visar att stora deformationer förekommer. Den största uppmätta deformation avlägsnas vid maskinbearbetningen. Den lilla temperaturhöjning som förekommer i vissa områden bidrar inte till någon korntillväxt. FEM studien visar att en cylindriskt kuts vid smidning inte är optimalt, eftersom materialspillet motsvarar ca 35-40%. Detta skulle kunna minska med en annan geometri på utgångsämnet.

  • 106.
    Jansson, Joakim
    Dalarna University, School of Technology and Business Studies, Material Science.
    Möjligheter till förbättrad valsekonomi2005Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [sv]

    Den största enskilda verktygskostnaden för tillverkning av varmvalsade band är kostnaden för valsar. Valsarna slits under valsningsprocessen och måste med jämna mellanrum slipas för att tillfredställande produktegenskaper skall innehållas. Livslängden för en vals bestäms av dess belastning, geometri och materialegenskaper, när de inte uppfyller kravet på mått eller hållfasthet måste de skrotas och ersättas. Kostnaden för valsar liksom produktiviteten påverkas således av flera faktorer. Valsmaterial, tillverkningsteknik för valsar, valsslipmaskiner, mätmetoder liksom metoder att utnyttja valsarna utvecklas hela tiden. Syftet med examensarbetet är att identifiera kostnaderna associerade med valsar och ge förslag till hur dessa kan sänkas. Ett databasbaserat utvärderingsverktyg ska utvecklas för att effektivt utvärdera valskostnaden. Då två nya valstyper (2:a generationen semi IC till steckelverket och HSS till förparet) insätts i drift under perioden och deras prestanda ska utvärderas ur ett tekniskt och ett ekonomiskt perspektiv.

  • 107.
    JOHANSSON, HELENA
    Dalarna University, School of Technology and Business Studies, Material Science.
    Variation i valskrafter på grund av skenmärken som uppkommit i stegbalksugnen: Variation in roll forces caused by skid marks from the walking beam furnace2006Independent thesis Basic level (degree of Bachelor)Student thesis
    Abstract [sv]

    I varmvalsverket vid SSAB Tunnplåt i Borlänge förvärms stålämnen i stegbalksugnar innan de går vidare genom valsningsprocessen. Under uppvärmningen vilar ämnena på skenor i ugnen, vilka ger upphov till områden på ämnet med lägre temperatur. Dessa områden benämns skenmärken. Den lägre temperaturen medför att högre valskraft krävs för att deformera materialet och den kan även ge upphov till skillnader i mikrostrukturutvecklingen. Syftet med denna rapport var att göra en jämförelse av mikrostrukturutvecklingen i och utanför skenmärken under varmvalsning av tunnplåt. Utredningen bygger på processdata från varmvalsverket vid SSAB Tunnplåt. De uppmätta värdena har använts för beräkningar av medelflytspänning (MFS) och medeltemperatur längs valsade band. Medelflytspänningarna har beräknats i Matlab med hjälp av programmet Friction - Hill. Medeltemperaturerna beräknades med Steeltemp. Fem band ingick i utredningen, två valsades mot slutvalstemperatur 870°C och tre mot slutvalstemperatur 930°C, varav två med väntetid före sista stick i förparet. Resultaten av beräkningarna har använts för att ta fram MFS – kurvor. Utifrån dessa har jämförelser gjorts, för att se om det finns skillnader i mikrostrukturutvecklingen i och utanför skenmärken. Vid jämförelsen av MFS – kurvorna i och utanför skenmärke kunde inte några direkta skillnader ses. Däremot förekommer variationer längs de band som valsats med högre valshastighet. Dessa variationer längs banden förekommer inte på de band som valsats med lägre hastighet samt mot lägre slutvalstemperatur.

  • 108. Johansson, M
    et al.
    Samuelsson, J
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Material Science.
    Sundell, P.-E
    Fatty Acid Derivatives in Radiation Curable Coatings2004In: Proceedings of e|5: UV & EB Technology Conference, Charlotte, NC, USA, 2004Conference paper (Refereed)
  • 109. Johansson, M
    et al.
    Samuelsson, J
    Sundell, P.-E
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Material Science.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Radiation Induced Polymerization of Monomers From Renewable Resources2003In: Polymer Preprints, ISSN 0551-4657, Vol. 44, no 1, p. 19-20Article in journal (Refereed)
  • 110.
    JOHANSSON, NICLAS
    Dalarna University, School of Technology and Business Studies, Material Science.
    FEM-simulering av axelutböjning i rullformningsmaskin: FEM-simulation of shaft deflection in a Roll Forming Mill2006Independent thesis Basic level (degree of Bachelor)Student thesis
    Abstract [sv]

    Rullformning är en formningsmetod som ökar för varje år på grund av att man kan ha en väldigt hög produktionshastigheten och skapa i princip vilken geometri som helst. Rullformning är en plåtformningsprocess där man viker plåten successivt genom att låta plåten få passera ett antal formade valspar som successivt ändrar formen för varje formningssteg. Detta fördjupningsarbete syftar till att undersöka den axelutböjningen som sker när en plåt förs in mellan formningsverktygen som sitter på axeln i rullfomningsmaskinen. Och med hjälp av FEM-simulering beräkna axelutböjningen samt validera dessa resultat mot verkliga experiment och teoretisk balkböjningsberäkning . Undersökningen visar att utböjningsvärdena för FEM-simulering överensstämmer något bättre mot experimenten än de teoretiska beräkningsmetoderna. Den teoretiska beräkningsmetod, kallad Fall 2 i denna rapport, är den teoretiska metod som bäst stämmer överens med de verkliga experimenten. Den metoden har ett belastningsfall där kraften från formningen approximeras med en punktlast. För enkla belastningsfall som är av den typ som behandlas i rapporten, är de teoretiska beräkningsmetoderna att föredra då FEM-modellering är för tidskrävande.

  • 111.
    Johnsson, Conny
    Dalarna University, School of Technology and Business Studies, Material Science.
    Götparksoptimering2005Independent thesis Basic level (degree of Bachelor)Student thesis
    Abstract [sv]

    Syftet med detta examensarbete var att kontrollera det reella utbytet med teoretiskt beräknade utbytet i smedjan inför uppgradering av de gamla utbytestabellerna. Projektet begränsades till två sorters detaljer, verktygsstålplattor och stång som har ett frekvent flöde genom anläggningen. Resultatet av examensarbetet visar att uppgradering av utbyteslistorna inte är något problem då man redan idag på dom flesta detaljer har samma utbytesgrad som dom nya listorna.

  • 112.
    Jojodu, Prasad
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Patibandla, Madhava
    Dalarna University, School of Technology and Business Studies, Material Science.
    Designing of Driving Electronics for Testing Different LCD's2004Independent thesis Advanced level (degree of Master (Two Years))Student thesis
  • 113.
    Jonsson, Per
    Dalarna University, School of Technology and Business Studies, Material Science.
    Ytstrukturens utveckling under tillverkning av kallvalsat rostfritt stål;: Development of the surface topography during production of cold rolled stainless steel2006Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [sv]

    Den här studien är en del av ett större projekt som bedrivs inom Outokumpu Stainless där varmvalsat material levererat till kallvalsning från flera olika leverantörer undersöks. Målet med examensarbetet är att kartlägga hur det inkommande varmvalsade materialet påverkar ytstrukturen hos den färdiga kallvalsade produkten, och hur olika processparametrar påverkar ytstrukturen hos det färdiga materialet. För provtagning användes replikateknik och för att utvärdera replikaten användes ett konfokalmikroskop hos Avesta Research Centre (ARC). En undersökning gjordes om replika teknikens tillförlitlighet. Prover togs på tre olika ställen i produktionen, före och efter kallvalsning samt på den färdiga 2B produkten. Två-, och tre-, dimensionella ytparametrar togs fram för proverna. Resultatet av undersökningen visar att: • Variation i ytråhet beror till större delen av reduktion och tjocklek hos det färdiga bandet. • Genom att slipa slabsen kan en något bättre yta hos den färdiga produkten erhållas. • Betningen efter kallvalsning har en stor inverkan på yttopografin hos den färdiga produkten och ger en ökad ytråhet. • Den utnyttjade replikatekniken fungerar bra för utvärdering av yttopografin hos valsad plåt.

  • 114. Jönsson, S.K.M
    et al.
    Birgerson, Jonas
    Dalarna University, School of Technology and Business Studies, Material Science.
    Crispin, X
    Greczynski, G
    Osikowicz, W
    Denier van der Gon, A.W
    Salaneck, W.R
    Fahlman, M
    The effects of solvents on the morphology and sheet resistance in poly(3,4-ethylenedioxythiophene)-polystyrenesulfonic acid (PEDOT-PSS) films2003In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 139, no 1, p. 1-10Article in journal (Refereed)
  • 115. Karlsson, P. G.
    et al.
    Richter, J. H.
    Blomquist, J.
    Uvdal, P.
    Grehk, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Sandell, A.
    Metal organic chemical vapor deposition of ultrathin ZrO2 films on Si(1 0 0) and Si(1 1 1) studied by electron spectroscopy2007In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 601, no 4, p. 1008-1018Article in journal (Refereed)
    Abstract [en]

    The growth of ultrathin ZrO2 films on Si(100)-(2x1) and Si(111)-(7x7) has been studied with core level photoelectron spectroscopy and X-ray absorption spectroscopy. The films were deposited sequentially by chemical vapor deposition in ultra-high vacuum using zirconium tetra-tert-butoxide as precursor. Deposition of a > 50Å thick film leads in both cases to tetragonal ZrO2 (t-ZrO2), whereas significant differences are found for thinner films. On Si(111)-(7x7) the local structure of t-ZrO2 is not observed until a film thickness of 51Å is reached. On Si(100)-(2x1) the local geometric structure of t-ZrO2 is formed already at a film thickness of 11Å. The higher tendency for the formation of t-ZrO2 on Si(100) is discussed in terms of Zr–O valence electron matching to the number of dangling bonds per surface Si atom. The Zr–O hybridization within the ZrO2 unit depends furthermore on the chemical composition of the surrounding. The precursor t-butoxy ligands undergo efficient C–O scission on Si(100), leaving carbonaceous fragments embedded in the interfacial layer. In contrast, after small deposits on Si(111) stable t-butoxy groups are found. These are consumed upon further deposition. Stable methyl and, possibly, also hydroxyl groups are found on both surfaces within a wide film thickness range.

  • 116.
    Kasimagwa, Ismail
    Dalarna University, School of Technology and Business Studies, Material Science.
    A study of slag corrosion of oxides and oxide-carbon refractories during steel refining2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The use of ceramic material as refractories in the manufacturing industry is a common practice worldwide. During usage, for example in the production of steel, these materials do experience severe working conditions including high temperatures, low pressures and corrosive environments. This results in lowered service lives and high consumptions of these materials. This, in turn, affects the productivity of the whole steel plant and thereby the cost. In order to investigate how the service life can be improved, studies have been carried out for refractories used in the inner lining of the steel ladles. More specifically, from the slag zone, where the corrosion is most severe. By combining thermodynamic simulations, plant trails and post-mortem studies of the refractories after service, vital information about the behaviour of the slagline refractories during steel refining and the causes of the accelerated wear in this ladle area has been achieved. The results from these studies show that the wear of the slagline refractories of the ladle is initiated at the preheating station, through reduction-oxidation reactions. The degree of the decarburization process is mostly dependent on the preheating fuel or the environment. For refractories without antioxidants, refractory decarburization is slower when coal gas is used in ladle preheating than when a mixture of oil and air is used. In addition, ladle preheating of the refractories without antioxidants leads to direct wear of the slagline refractories. This is due to the total loss of the matrix strength, which results in a sand-like product. Thermal chemical changes that take place in the slagline refractories are due to the MgO-C reaction as well as the formation of liquid phases from impurity oxides. In addition, the decrease in the system pressure during steel refining makes the MgO-C reaction take place at the steel refining temperatures. This reduces the refractory’s resistance to corrosion. This is a serious problem for both the magnesia-carbon and dolomite-carbon refractories. The studies of the reactions between the slagline refractories and the different slag compositions showed that slags rich in iron oxide lead mostly to the oxidation of carbon/graphite in the carbon-containing refractories. This leads to an increased porosity and wettability and therefore an enhanced penetration of slag into the refractory structure. If the slag contains high contents of alumina and or silica (such as the steel refining slag), reactions between the slag components and the dolomite-carbon refractory are promoted. This leads to the formation of low-temperature melting phases such as calcium-aluminates and silicates. The state of these reaction products during steel refining leads to an accelerated wear of the dolomite-carbon refractory. The main products of the reactions between the magnesia-carbon refractory and the steel refining slag are MgAl2O4 spinels, and calcium-aluminates, and silicates. Due to the good refractory properties of MgAl2O4 spinels, the slag corrosion resistance of the magnesiacarbon refractory is promoted.

  • 117.
    Kasimagwa, Ismail
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Brabie, Voicu
    Dalarna University, School of Technology and Business Studies, Material Science.
    Jönsson, Pär G.
    Studies on decarburization of MgO-c refractories during ladle preheating2010In: Steel GRIPS Journal, ISSN 1611-4442, no 8, p. 357-363Article in journal (Refereed)
  • 118.
    Keränen, Elias
    Dalarna University, School of Technology and Business Studies, Material Science.
    Experimental and modelling ofmachining behavior of stainlesssteel in interrupted cutting withcoated cemented carbide2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Understanding the chip formation process and the loads that the tools are subjected to in intermittent cutting operations of stainless steel are of importance in order to increase the span of the tool life. Examples of improvements that would follow an increased tool life are reduced use of materials, decreased energy consumption, increased productivities and increased quality of the finished product.A study has been carried out to increase the understanding of chip formation process and what conditions the cutting tool is exposed to in metal cutting in the stainless steel 316L under intermittent conditions. Wear and wear rates of the cutting tools used in these conditions are determined by mechanical and thermal fatigue caused by the stress and temperature cycles. A number of different substrates with varying carbide grain size and cobalt content were included to find the beneficial properties of the cemented carbide. The study includes both practical cutting tests and simulations done in AdvantEdge with varying feed and cutting speed.A preliminary version of a power law based temperature dependent model including damage evolution has been proposed. The model was able to predict chip segmentation but failed to capture the non-linear relation between segmentation parameters and cutting speed.Simulations showed that the tool exit generates tensile stresses in the rake face of the tool which may result in fracture of the cutting edge. These stresses are caused by the footing phenomena that alter the chip formation momentarily during the tool exit.Tests also showed that it is difficult to predict tool life in milling operations of the stainless steel 316L. Chipping proved to be a dominant wear mechanism of the cemented carbide. Tough substrates with a coarse grain size and high cobalt content proved to be beneficial in terms of wear rates and tool life.

  • 119.
    Kivelö, Tommi
    Dalarna University, School of Technology and Business Studies, Material Science.
    Optimering av hålltidstabeller vid Normaliseringsugnen2005Independent thesis Basic level (degree of Bachelor)Student thesis
    Abstract [sv]

    Analyserna av hålltiderna i Normaliseringsugnen visar att i de flesta fall kan hålltiderna förkortas, beroende på om man väljer att godkänna värmebehandlingen vid en temperatur 15C° eller 5C° under börvärdet. Om 5C° väljas kan det krävas att vissa ugnstider förlängs. Det finns ingen anledning att hålla övertid på plåtarna i ugnen, vilket kan leda till korntillväxt och ett sprött material. Undersökningen visar att övertiden ökar med plåttjockleken. Temperaturavvikelsediagrammet för värmebehandlingen visar att inom tjockleksintervallet 30mm - 50mm är temperaturdifferensen vid hålltidens slut störst gentemot börvärdet. Man bör dock komma ihåg att pyrometern endast mäter yttemperaturen. Kärntemperaturen är förmodligen något lägre och då krävs en viss övertid för att säkerställa en homogen temperatur genom hela plåten. Vid ett lyckat experiment med att plana en plåt, efter att ha värmt upp den till 650°C, gjordes en simulering i dataprogrammet Steeltemp 2D. Simuleringen visar svalningskurvor för en given analyskod från 600°C för olika plåttjocklekar. Temperaturen på experimentplåten vid inträdet i planmaskinen var 350°C. Resultatet som redovisas i Steeltempdiagrammet visar att det inte finns risk att plåttemperaturen sjunker under 350°C.

  • 120.
    Kleist, Anders
    Dalarna University, School of Technology and Business Studies, Material Science.
    Theory of super power saving circuits and configurations for mixed signal CPU for smartcard application2003Independent thesis Advanced level (degree of Master (Two Years))Student thesis
  • 121.
    Kohrs, Johnny
    Dalarna University, School of Technology and Business Studies, Material Science.
    Pulverlacks vidhäftning på zinkmanganfosfaterad yta2011Independent thesis Basic level (degree of Bachelor)Student thesis
  • 122.
    Kommireddy, Narasinga
    Dalarna University, School of Technology and Business Studies, Material Science.
    ITO Matching for Optimizing the Optical Properties of Off-State LC-cell2004Independent thesis Advanced level (degree of Master (Two Years))Student thesis
  • 123. Kozlovsky, M.
    et al.
    Lymarenko, R.
    Wang, Lu
    Dalarna University, School of Technology and Business Studies, Material Science.
    Haase, W.
    Chiral photochromic liquid crystalline polymers for holographic applications2004In: Proc. of SPIE, 2004Conference paper (Refereed)
  • 124. Kozlovsky, M.
    et al.
    Skarp, Kent
    Dalarna University, School of Technology and Business Studies, Material Science.
    Kinetically controlled phase transitions in LC polymers2005In: Journal of Polymer Science Part B: Polymer Physics, ISSN 0887-6266, E-ISSN 1099-0488Article in journal (Refereed)
  • 125.
    Kvarnström, Maria
    Dalarna University, School of Technology and Business Studies, Material Science.
    Undersökning av inneslutningsstatusen i en stålsort före och efter gjutning2006Independent thesis Basic level (degree of Bachelor)Student thesis
    Abstract [sv]

    Ett 10 poängs examensarbete om bildandet av inneslutningar under gjutning och stelning har utförts på Uddeholm Tooling AB. Syftet har varit att titta på vilka inneslutningar som bildas under gjutning och stelning samt att undersöka om ett gjutpulver med lägre svavelhalt påverkar segringen nära ytan. Försöket har gjorts på ORVAR 2M som är det största stålet tonnagemässigt på Uddeholm Tooling AB. Prover har tagits från ugnen innan gjutning, under gjutningen och på stelnat material. Stora mängder aluminiumoxid löstes in under gjutförloppet p.g.a att gjutningen inte var skyddad av argongas, vilket den i normala fall är. I försöket med lågsvavelhaltigt gjutpulver kunde man se att det inte gav någon svavelhöjande effekt på ytan.

  • 126.
    Larsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Optimala reduktionsgränser för kalldragna rör: Optimal reduction limits for cold-drawn tubes2006Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [sv]

    Dragbänken installerades på avdelning kallbearbetade rör på Ovako i Hofors 1990. Sedan dess har kvalitetskraven på de dragna rören ökat. Samtidigt har produktivitetskraven ökat, det vill säga att tillverka rör till rätt kostnad. I produktionsplaneringsprogrammet finns gränser och regler för hur de dragna rören ska tillverkas för att rätt kvalitet och kostnad ska uppnås. Eftersom både de dragna rören och de varmvalsade ingångsrören har ändrats med åren så stämmer inte alltid gränserna och reglerna idag. Med anledning av detta undersöks reduktionsgränserna i det här examensarbetet. Resultaten visar att en kraftigare areareduktion kan användas vilket borde kunna öka produktiviteten i dragbänken. Detta examensarbete behandlar även deformationsförloppet av kalldragningsprocessen. En bild av deformationszonen fås fram i form av konturer med en koordinatmätare. Med hjälp av dessa konturer kan väggtjocklekens variation i deformationszonen fås fram. Med denna kunskap genereras en modell där väggtjocklekens toppvärde kan predikteras. Beräkningarna med modellen ger en avvikelse mot det uppmätta toppvärdet på väggtjockleken på som störst 1,9 %. Osäkerheten ökar med ett ökande spel.

  • 127.
    Lindgren, Lars-Erik
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Carlsson, Per
    Dalarna University, School of Technology and Business Studies, Material Science.
    Simulation of hydroforming of steel tube made of metastable stainless steel2010In: International journal of plasticity, ISSN 0749-6419, E-ISSN 1879-2154, Vol. 26, no 11, p. 1576-1590Article in journal (Refereed)
    Abstract [en]

    The Olson-Cohen model for strain-induced deformation, further developed by Stringfellow and others, has been calibrated together with a flow stress model for the plastic deformation of metastable stainless steel. Special validation tests for checking one of the limitations of the model have also been carried out. The model has been implemented into a commercial finite element code using a staggered approach for integrating the stress-strain relations with the microstructure model. Results from a thermo-mechanical coupled simulation of hydroforming of a tube have been compared with corresponding experiments. The agreement between experimental results of radial expansion and martensite fraction and the corresponding computed results is good. 

  • 128.
    Lindgren, Michael
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Wikström, Lars
    Roll forming of partially heated cold rolled stainless steel2009In: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 209, no 7, p. 3117-3124Article in journal (Refereed)
    Abstract [en]

    Today you will find roll formed details in many different products, for example buildings, household appliances and vehicles. The industry, in order to save weight, tends to use more and more high strength steel. The disadvantage with these materials is that they can be difficult to form due to reduced ductility. A way to increase the ductility in the forming areas is by partially heat the steel. It is shown that partial heating substantially increases the ductility of high strength steel and make it possible to roll form large bend angles. When roll forming, the material will work hardening almost to the as-received condition in the outer and inner radius of the roll formed profile. Furthermore, the heating power decides the bend angle obtained. Finally, the mechanical properties after heating and roll forming are discussed.

  • 129. Lissel, Linda
    et al.
    Engberg, Göran
    Dalarna University, School of Technology and Business Studies, Material Science.
    Prediction of the microstructural evolution during hot strip rolling of Nb microalloyed steels2007In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 558-559, no 2, p. 1127-1132Article in journal (Refereed)
    Abstract [en]

    A physically based model is used to describe the microstructural evolution of Nb microalloyed steels during hot rolling. The model is based on a physical description of dislocation density evolution, where the generation and recovery of dislocations determines the flow stress and also the driving force for recrystallization. In the model, abnormally growing subgrains are assumed to be the nuclei of recrystallized grains and recrystallization starts when the subgrains reach a critical size and configuration. The model is used to predict the flow stress during rolling in SSAB Tunnplåt’s hot strip mill. The predicted flow stress in each stand was compared to the stresses calculated by a friction-hill roll-force model. Good fit is obtained between the predicted values by the microstructure model and the measured mill data, with an agreement generally within the interval ±15%.

  • 130. Lissel, Linda
    et al.
    Engberg, Göran
    Dalarna University, School of Technology and Business Studies, Material Science.
    Borggren, Ulrika
    Modeling precipitation and its effect on recrystallization during hot strip rolling of niobium steels2008In: 3rd Int. Conf. on Thermomechanical Processing of Steels, Padua, Italy, 2008Conference paper (Other academic)
    Abstract [en]

    Using a physically based model, the microstructural evolution of Nb microalloyed steels during rolling in SSAB Tunnplåt’s hot strip mill was modeled. The model describes the evolution of dislocation density, the creation and diffusion of vacancies, dynamic and static recovery through climb and glide, subgrain formation and growth, dynamic and static recrystallization and grain growth. Also, the model describes the dissolution and precipitation of particles. The impeding effect on grain growth and recrystallization due to solute drag and particles is accounted for. During hot strip rolling of Nb steels, Nb in solid solution retards recrystallization due to solute drag and at lower temperatures strain-induced precipitation of Nb(C,N) may occur which effectively retard recrystallization. The flow stress behavior during hot rolling was calculated where the mean flow stress values were calculated using both the model and measured mill data. The model showed that solute drag has an essential effect on recrystallization during hot rolling of Nb steels.

  • 131.
    Mahinay, Cheryll
    Dalarna University, School of Technology and Business Studies, Material Science.
    Investigation of Liquid Crystal Alignment on Room-Temperature Polyimide Alignment Films2004Independent thesis Advanced level (degree of Master (Two Years))Student thesis
  • 132. Malmberg, P.
    et al.
    Bexell, Ulf
    Dalarna University, School of Technology and Business Studies, Material Science.
    Eriksson, C.
    Nygren, H.
    Richter, K.
    Analysis of bone minerals by time-of-flight secondary ion mass spectrometry: a comparative study using monoatomic and cluster ions sources2007In: Rapid Communications in Mass Spectrometry, ISSN 0951-4198, E-ISSN 1097-0231, Vol. 21, no 5, p. 745-749Article in journal (Refereed)
    Abstract [en]

    Time-of-flight secondary ion mass spectrometry (TOF-SIMS) is an important tool for the analysis of bone minerals at implant surfaces. Most studies have been performed with monoatomic primary ion sources such as Ga+ with poor secondary molecular ion production efficiency and only elemental distributions and minor fragments of bone minerals have been reported. By using cluster ion sources, such as Au and Bi, identification of larger hydroxyapatite species at m/z 485, 541, 597 and 653, identified as Ca5P3O12, Ca6P3O13, Ca7P3O14 and Ca8P3O15, respectively, became possible. The ions appear to be fragments of the hydroxyapatite unit cell Ca10(PO4)6(OH)2. Each ion in the series is separated by 55.9 m/z units, corresponding to CaO, and this separation might reflect the columnar nature of the unit cell. Copyright © 2007 John Wiley & Sons, Ltd.

  • 133.
    Malmesjö, Christer
    Dalarna University, School of Technology and Business Studies, Material Science.
    Analys av förvridning vid hålning av rör: Analysis of metal torsion in rotary piercing2005Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [sv]

    Hålningsprocessen är det inledande bearbetningssteget vid varmvalsning av sömlösa rör. Det är en tvärvalsningsprocess i vilken ett cylindriskt ämne valsas mellan två dubbelkoniska val¬sar över en plugg. Valsarna är snedställda med en viss mat¬ningsvinkel, vilken ger upphov till en axiell drivkraft genom ver¬ket. Hela denna pro¬cess är roterande. Detta i kombination med bl.a. de koniska valsarna leder till en förvrid¬ning av röret, dvs. en tänkt rak linje på det ingå¬ende äm¬net övergår till en spiral efter genomförd valsning. Med föreliggande uppgift är målet att studera förvridningen genom teoretisk och experimen¬tell analys. Syftet med detta är dels att få fördjupad kunskap inom området och dels att ut¬veckla en modell för pre¬diktering av förvridningen. Det experimentella arbetet är utfört på ett stål av typ Ovako 280 (SS2142). Denna mjuka stål¬sort valdes i syfte att undvika värmebehandling innan provberedning. För att visuali¬sera för¬vridningen fräs¬tes ett rakt spår längs det ingående äm¬net och hål borrades mot symmetrilinjen. De praktiska undersökningarna utfördes direkt i den löpande produktionen. Genomförda beräkningar uppvisar en längsgående förvridningsvinkel som stämmer väl över¬ens med uppmätt värde. Detta är dock under antagandet att den tangentiella hastighetskoeffi¬cienten varierar linjärt utmed deformationszonen. För en mer utvecklad modell krävs en nog¬grannare analys av kontakten mellan vals/ämne eller en grundligt genomförd uppmätning av ämnets vinkelhastighet.

  • 134. Marciniak, S
    et al.
    Crispin, X
    Uvdal, K
    Trzcinski, M
    Birgerson, Jonas
    Dalarna University, School of Technology and Business Studies, Material Science.
    Louwet, F
    Salaneck, W.R.
    Light induced damages in Poly(3,4-ethylenedioxythiophene) and its deratives: a photoelectron spectroscopy study2004In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 141, no 1-2, p. 67-73Article in journal (Refereed)
  • 135.
    Memarpour, Arashk
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Brabie, Voicu
    Dalarna University, School of Technology and Business Studies, Material Science.
    Jönsson, Pär
    Studies of effect of glass/silicon powder coatings on clogging behaviour of submerged entry nozzles when using REM alloyed stainless steels2011In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 38, no 3, p. 229-239Article in journal (Refereed)
    Abstract [en]

    The internal surfaces of modern submerged entry nozzles (SENs) were coated with a glass/silicon powder layer to prevent SEN graphite oxidation during preheating. The effects of the interaction between the coating layer and the SEN base refractory materials on clogging were studied. The results indicated that penetration of the formed alkaline rich glaze into the alumina/graphite base refractory occurs during preheating. More specifically, the glaze reacts with graphite to form carbon monoxide gas. Thereafter, dissociation of CO at the SEN/molten metal interface takes place. This leads to reoxidation of dissolved rare earth metals, which form ‘in situ’ rare earth metal oxides at the interface between the SEN and the molten steel. In addition, the interaction of the penetrated glaze with alumina in the SEN base refractory materials leads to the formation of a high viscous alumina rich glaze during the SEN preheating process. This, in turn, creates a very uneven surface at the SEN internal surface. The ‘in situ’ formation of the rare earth metal oxides together with the uneven internal surface of the SEN may facilitate the accumulation of the primary inclusions on the refractory walls.

  • 136.
    Memarpour, Arashk
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Brabie, Voicu
    Jönsson, Pär
    Studies of Yttria Stabilized Zirconia (YSZ) plasma-PVD coated Al2O3-C refractory base materials of a commercial SEN with respect todecarburization and clogging2011In: Steel Grips - Journal of Steel and Related Materials, ISSN 1866-8453Article in journal (Refereed)
    Abstract [en]

    Carbon oxidation is a main industrial problem for alumina-graphite refractory base materials used in commercial Submerged Entry Nozzles (SEN) during preheating. Thus, the effects of the plasma spray-PVD coating of the Yttria Stabilized Zirconia (YSZ) powder on the carbon oxidation were investigated. Laboratory preheating trials were performed at non-isothermal heating conditions in a controlled atmosphere. Also, the applied temperature profile for the laboratory trials were defined based on industrial preheating trials. The controlled atmospheres consisted of CO2, O2 and Ar. The (CO2/O2) ratios were kept the same as for a propane combustion flue gas at an Air-Fuel-Ratio (AFR) value equal to 1.5 for heating in an air-fuel mixture and in air. The thicknesses of the decarburized layers were measured and examined using light optic microscopy, FEG-SEM and EDS. The YSZ plasma-PVD coated alumina-graphite refractory base materials, presented the effective resistance to carbon oxidation at different coating thicknesses from 160-480 μm in both combustion flue gas and air atmospheres. For the YSZ plasma coating that contained a thinner coating layer such as 160 μm, the uneven surface of the substrate may be reflected more than it could be reflected for a thicker coating. However, for the YSZ plasma coating with a coating thickness of 290 μm, the uneven surface of the substrate may be reflected much less than it could be reflected for thinner coatings. A 250μm and a 290μm YSZ coating may prevent the decarburization of an alumina-graphite refractory base materials during preheating in air at a maximum heating temperature of 1020°C. Moreover, in an oxidizing atmosphere with an AFR value equal to 1.5 at a maximum temperature of 1020°C and a holding time of 7200 seconds. A 250-290 μm YSZ coating is suggested to be an appropriate coating, as it provides both an even surface and prevention of the decarburization even during heating in air. In addition, the interactions between the YSZ coated alumina-graphite refractory base materials in contact with a cerium alloyed molten stainless steel were surveyed. The YSZ coating provided a total prevention of the alumina reduction by cerium. Therefore, the prevention of the first clogging product formed on the surface of the SEN refractory base materials. Therefore, the YSZ plasma-PVD coating can be recommended for coating of the hot surface of thecommercial SENs.

  • 137.
    Memarpour, Arashk
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Brabie, Voicu
    Jönsson, Pär G.
    Decarburization and clogging behaviour of yttria stabilized zirconia coatings applied to SEN´s Al2O3-C refractories by plasma PVD2012In: Steel Grips - Journal of Steel and Related Materials, ISSN 1611-4442, E-ISSN 1866-8453, Vol. 10, p. 353-363Article in journal (Refereed)
    Abstract [en]

    Carbon oxidation is a main industrial problem for alumina-graphite refractory base materials used in commercial Submerged Entry Nozzles (SEN) during preheating. Thus, the effects of the plasma spray-PVD coating of the Yttria Stabilized Zirconia (YSZ) powder on the carbon oxidation were investigated. Laboratory preheating trials were performed at non-isothermal heating conditions in a controlled atmosphere. Also, the applied temperature profile for the laboratory trials were defined based on industrial preheating trials. The controlled atmospheres consisted of CO2, O2 and Ar. The (CO2/O2) ratios were kept the same as for a propane combustion flue gas at an Air-Fuel-Ratio (AFR) value equal to 1.5 for heating in an air-fuel mixture and in air. The thicknesses of the decarburized layers were measured and examined using light optic microscopy, FEG-SEM and EDS. The YSZ plasma-PVD coated alumina-graphite refractory base materials, presented the effective resistance to carbon oxidation at different coating thicknesses from 160-480 µm in both combustion flue gas and air atmospheres. For the YSZ plasma coating that contained a thinner coating layer such as 160 µm, the uneven surface of the substrate may be reflected more than it could be reflected for a thicker coating. However, for the YSZ plasma coating with a coating thickness of 290 µm, the uneven surface of the substrate may be reflected much less than it could be reflected for thinner coatings. A 250µm and a 290µm YSZ coating may prevent the decarburization of an alumina-graphite refractory base materials during preheating in air at a maximum heating temperature of 1020°C. Moreover, in an oxidizing atmosphere with an AFR value equal to 1.5 at a maximum temperature of 1020°C and a holding time of 7200 seconds. A 250-290 µm YSZ coating is suggested to be an appropriate coating, as it provides both an even surface and prevention of the decarburization even during heating in air. In addition, the interactions between the YSZ coated alumina-graphite refractory base materials in contact with a cerium alloyed molten stainless steel were surveyed. The YSZ coating provided a total prevention of the alumina reduction by cerium. Therefore, the prevention of the first clogging product formed on the surface of the SEN refractory base materials. Therefore, the YSZ plasma-PVD coating can be recommended for coating of the hot surface of the commercial SENs.

  • 138.
    Memarpour, Arashk
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Brabie, Voicu
    Dalarna University, School of Technology and Business Studies, Material Science.
    Jönsson, Pär G.
    Post-mortem study of the internal coated SENs (Submerged Entry Nozzle) respecting clogging phenomena2011Conference paper (Refereed)
    Abstract [en]

    A large number of accretion samples formed inside alumina/graphite clogged Submerged Entry Nozzles (SEN) were examined using FEG-SEM-EDS and Feature analysis. The SENs were used for continuous casting of stainless steel grades alloyed by Rare Earth Metals (REM). The internal surfaces of the SENs were coated by a glass/silicon powder layer to prevent the SEN decarburization during the preheating process. The results indicated a harmful effect of the SENs decarburization on the accretion thickness. In addition, the post-mortem results clearly revealed the formation of a multi-layer accretion. Also, the study indicated the penetration of the protecting glaze into the Alumina/graphite refractory materials. The interaction of the penetrated glaze with alumina in the SEN refractory materials leads to formation of high viscous alumina-rich glaze during the SEN preheating process. This interaction may lead to formation of an uneven surface inside the SEN. These areas consist of alumina particles, silica particles and the penetrated glaze in between. The results showed that these areas react with dissolved REM in molten steel to form REM aluminates, REM silicates and REM alumina-silicates. Furthermore, the penetration of the glaze may lead to reactions between alkalines in the glaze and the graphite. This leads to a supply of oxygen at the interface between the SEN and the molten steel. This, in turn, may lead to reoxidation of the REM alloying elements in molten steel under the formation of “in situ” REM oxides. The formation of the large “in-situ” REM oxides and the reaction of the REM alloying elements with the SEN´s uneven inside surface, may create a large REM-rich surface in contact with the primary inclusions in molten steel. This may facilitate the attraction and agglomeration of the primary REM oxides inclusions on the SEN internal surface and thereafter the clogging.

  • 139.
    Memarpour, Arashk
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Brabie, Voicu
    Dalarna University, School of Technology and Business Studies, Material Science.
    Jönsson, Pär G.
    Studies on the decarburization of the commercial Submerged Entry Nozzles (SEN)2011In: Steel Grips, ISSN 1866-8453, no 9, p. 121-127Article in journal (Refereed)
    Abstract [en]

    Decarburization behaviours of Al2O3-C, ZrO2-C and MgO-C refractory materials constituting a commercial Submerged Entry Nozzle (SEN), have been investigated in different gas atmospheres consisting of CO2, O2 and Ar. The (CO2/ O2) ratio values were kept the same as it is in propane combustion flue gas at Air-Fuel-Ratio (AFR) values equal to 1.5 and 1 for both Air-Fuel and Oxygen-Fuel combustion systems. Laboratory experiments were carried out non-isothermally in the temperature range 873 K to 1473 K at 15 (K•min-1) followed by isothermal heating at 1473 K for 60 min. The decarburization ratio (a) values of the three refractory types were determined by measuring the real time weight losses of the samples. The results showed that the decarburization ratio (a) values of the MgO-C refractory became 3.1 times higher for Oxygen-Fuel combustion compared to Air-Fuel combustion at an AFR equal to 1.5 in the temperature range 873 K to 1473 K. The decarburization ratio (a) values for Al2O3-C samples were the same as for the isothermal heating at 1473 K and non-isothermal heating in the temperature range 1473 K to 1773 K with a 15 (K•min-1) heating rate. It substantiates the SEN preheating advantage at higher temperatures for shorter holding times instead of heating at lower temperatures for longer holding times. Diffusion models were proposed for estimating the decarburization rate of Al2O3-C refractory in the SEN. The activation energy for Al2O3-C samples heated at an AFR equal to 1.5, for Air-Fuel and Oxygen-Fuel combustions were found to be 81.8 (KJ•mol-1) and 88.8 (KJ•mol-1), respectively during non-isothermal heating in the temperature range 873 K to 1473 K.

  • 140.
    Memarpour, Arashk
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Brabie, Voicu
    Dalarna University, School of Technology and Business Studies, Material Science.
    Jönsson, Pär G.
    The effect of zirconium disilicide (ZrSi2) additions on the carbon oxidation behavior of alumina/graphite refractory materials2010In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 50, no 11, p. 1612-1621Article in journal (Refereed)
    Abstract [en]

    Carbon oxidation is a main industrial problem for Alumina/Graphite Submerged Entry Nozzles (SEN) during pre-heating. Thus, the effect of ZrSi2 antioxidants and the coexistence of antioxidant additive and (4B2O3 •BaO) glass powder on carbon oxidation were investigated at simulated non-isothermal heating conditions in a controlled atmosphere. Also, the effect of ZrSi2 antioxidants on carbon oxidation was investigated at isothermal temperatures at 1473 K and 1773 K. The specimens’ weight loss and temperature were plotted versus time and compared to each others. The thickness of the oxide areas were measured and examined using XRD, FEG-SEM and EDS. The coexistence of 8 wt% ZrSi2 and 15 wt% (4B2O3 •BaO) glass powder of the total alumina/Graphite base refractory materials, presented the most effective resistance to carbon oxidation. The 121% volume expansion due to the Zircon formation during heating and filling up the open pores by (4B2O3 •BaO) glaze during green body sintering led to an excellent carbon oxidation resistance.

  • 141.
    Mirjana, Filipovic
    Dalarna University, School of Technology and Business Studies, Material Science.
    Evolution of artificial defects during shape rolling2007Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Very often defects are present in rolled products. For wire rods, defects are very deleterious since the wire rods are generally used directly in various applications. For this reason, the market nowadays requires wire rods to be completely defect-free. Any wire with defects must be rejected as scrap which is very costly for the production mill. Thus, it is very important to study the formation and evolution of defects during wire rod rolling in order to better understand and minimize the problem, at the same time improving quality of the wire rods and reducing production costs. The present work is focused on the evolution of artificial defects during rolling. Longitudinal surface defects are studied during shape rolling of an AISI M2 high speed steel and a longitudinal central inner defect is studied in an AISI 304L austenitic stainless steel during ultra-high-speed wire rod rolling. Experimental studies are carried out by rolling short rods prepared with arteficial defects. The evolution of the defects is characterised and compared to numerical analyses. The comparison shows that surface defects generally reduce quicker in the experiments than predicted by the simulations whereas a good agreement is generally obtained for the central defect.

  • 142.
    Moser, Dominik
    Dalarna University, School of Technology and Business Studies, Material Science.
    Automated Development of Thin Film Polarizer for LC Displays2003Independent thesis Advanced level (degree of Master (Two Years))Student thesis
  • 143.
    MÅNSSON, RONJA
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    TALUS, ANNIKA
    Dalarna University, School of Technology and Business Studies, Material Science.
    Utformning av laborationer i plåtformning: Development of laboratory exercises in sheet metal forming2007Independent thesis Basic level (degree of Bachelor)Student thesis
    Abstract [sv]

    Hösten 2008 är det planerat att en ny masterutbildning inom materialvetenskap med inriktning formnings- och ytteknik ska starta på Högskolan Dalarna. Utbildningen kommer att innehålla en kurs om konventionella formningsmetoder och plasticitetsteori. För att illustrera olika fenomen inom formning ska laborationer vara ett moment i kursen. Syftet med detta projekt var att utveckla ett par laborationer som behandlar och ger förståelse för olika fenomen inom konventionell plåtformning. Dragpressning, sträckpressning och olika typer av bockning är vanliga formningsmetoder som ofta förekommer i industrin. Formning av ett material leder till både en elastisk och en plastisk deformation och ett vanligt fenomen som uppkommer vid all typ av formning är återfjädring, detta på grund av att den elastiska deformationen hos materialet återgår efter formning. En annan viktig parameter vid plåtformning är formbarheten hos materialet, vilken bland annat påverkas av materialets deformationshårdnande som uppstår hos de flesta metaller och legeringar vid plastisk deformation. Detta kan beskrivas med hjälp av en kallhärdningsexponent som utvärderas genom användning av spännings- töjningskurvor. Projektet resulterade i två genomförbara laborationer. En av laborationerna behandlar fenomenet återfjädring och illustrerar detta vid rullformning, vilket dock inte är en konventionell metod men som ändå kan jämföras med bockning. Denna laboration går att genomföra på Högskolan Dalarna. Laboration nummer två syftar till att öka förståelsen för hur deformationshårdnandet hos ett material påverkar formbarheten. Denna laboration utförs på sträckpressning och är utvecklad i samarbete med Outokumpu Stainless AB, Avesta Research Centre.

  • 144.
    Naveen, Anumula
    Dalarna University, School of Technology and Business Studies, Material Science.
    Measurement of Optical Properties for a 3D Monitor2004Independent thesis Advanced level (degree of Master (Two Years))Student thesis
  • 145.
    Nilsson, Johan
    Dalarna University, School of Technology and Business Studies, Material Science.
    Dragprovsegenskaper av svetsad och värmebehandlad JBK-752006Independent thesis Basic level (degree of Bachelor)Student thesis
    Abstract [sv]

    Syftet med detta examensarbete var att ta fram dragprovsegenskaper för EB-svetsad och värmebehandlad JBK-75. JBK-75 är en järnbaserad superlegering, snarlik A-286 men med förbättrade svetsegenskaper. Fyra olika värmebehandlingar valdes: • 900°C / 2h, 725°C / 16h • 980°C / 1h, 725°C / 16h • 900°C / 2h • 900°C / 24h, 725°C / 16h Det blev överraskande nog ingen större skillnad i egenskaper hos dom svetsade provstavarna, förutom den som inte genomgått åldringsprocessen. För referensprovstavarna (utan svets) gav denna värmebehandling: 900°C / 2h, 725°C / 16h, dom bästa egenskaperna.

  • 146.
    Nilsson, Maria
    Dalarna University, School of Technology and Business Studies, Material Science.
    Tribological Evaluation of CVD- and PVD-Coatings for Wire Drawing Applications2008Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    Ovako Steel is one of the world’s largest manufacturers of ball bearing steel. In the manufacturing route of ball bearing steel, wire drawing is one of the important steps for the production of wire products. Wire drawing dies used in the production at Ovako in Hällefors are today made of cemented carbide. The aim of this study was to investigate the friction and wear characteristics of a number of CVD- and PVD-coatings, deposited on the Ovako steel grade Ovatec 677, in sliding contact with the steel grade Ovako 803 using pin-on-disc testing. Based on the results obtained from this pin-on-disc investigation, three coatings were chosen to be deposited on drawing dies made of Ovatec 677. An introductory study of cemented carbide dies indicated that the coating should have low friction in the lubricated contact, and preferably also under local dry contact conditions, with steel to reduce the frictional heat since thermal softening of the steel substrate must be avoided. It also showed that the coating should have a smooth surface topography in order to reduce the material pick-up tendency and adhesive wear of the coating material. The coating should also show a high wear resistance/cracking resistance, i.e. a combination of high hardness and toughness. With these requirements in mind, two different coatings, a PVD CrC/C-coating, a CVD TiC-coating and a dual-layer TiC/CrC/C-coating, were found to be the most suitable for deposition on wire drawing dies.

  • 147.
    Nilsson, Maria
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    On the possibility to replace cemented carbide with CVD and PVD coated steel in wire drawing dies – A tribological investigation2009In: Wear of Materials, Las Vegas, 2009Conference paper (Other academic)
    Abstract [en]

    Cemented carbide is today the most frequently used drawing die material in steel wire drawing applications. This is mainly due to the possibility to obtain a broad combination of hardness and toughness thus meeting the requirements concerning strength, crack resistance and wear resistance set by the wire drawing process. However, the increasing cost of cemented carbide in combination with the possibility to increase the wear resistance of steel through the deposition of wear resistant CVD and PVD coatings have increased the interest for steel wire drawing dies during the last years. In the present study, the possibility to replace cemented carbide wire drawing dies with CVD and PVD coated steel drawing dies have been investigated by i) tribological testing, i.e. pin-on-disc and scratch testing, in combination with post-test observations of the tribo surfaces using scanning electron microscopy, energy dispersive X-ray spectroscopy and 3D surface profilometry and ii) steel wire drawing under full scale industrial conditions. In the tests a sodium stearate based soap was used as a lubricant. Of the CVD and PVD coatings evaluated in the tribological tests, a CVD TiC and a PVD CrC/C coating displayed the most promising results, i.e. a combination of high wear resistance and low friction in contact with the steel wire material and consequently these coatings were selected for the steel wire drawing tests. Post-test examination of the worn drawing dies showed that the CrC/C coating displayed a high wear rate while the TiC coating showed a low wear rate but also signs of local cracking and chipping. However, the overall best performance was displayed by a TiC – CrC/C dual layer coating which displayed a limited cracking and chipping tendency although the top CrC/C coating showed a high wear rate. Based on the results obtained, CVD and PVD coatings aimed to provide improved tribological performance of steel wire drawing dies should display a smooth surface topography, a high wear resistance, a high fracture toughness (i.e. a high cracking and chipping resistance) and intrinsic low friction properties in contact with the wire material. Also, the steel substrate used must display a sufficient load carrying capacity and resistance to thermal softening.

  • 148.
    Nilsson, Maria
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Tribological Testing of Some Potential PVD and CVD Coatings for Steel Wire Drawing Dies2010In: Nordtrib 2010, Storforsen, 2010Conference paper (Refereed)
    Abstract [en]

    Cemented carbide is today the most frequently used drawing die material in steel wire drawing applications. This is mainly due to the possibility to obtain a broad combination of hardness and toughness thus meeting the requirements concerning strength, crack resistance and wear resistance set by the wire drawing process. However, the increasing cost of cemented carbide in combination with the possibility to increase the wear resistance of steel through the deposition of wear resistant CVD and PVD coatings have enhanced the interest to replace cemented carbide drawing dies with CVD and PVD coated steel wire drawing dies. In the present study, the possibility to replace cemented carbide wire drawing dies with CVD and PVD coated steel drawing dies have been investigated by tribological characterisation, i.e. pin-on-disc and scratch testing, in combination with post-test observations of the tribo surfaces using scanning electron microscopy, energy dispersive X-ray spectroscopy and 3D surface profilometry. Based on the results obtained, CVD and PVD coatings aimed to provide improved tribological performance of steel wire drawing dies should display a smooth surface topography, a high wear resistance, a high fracture toughness (i.e. a high cracking and chipping resistance) and intrinsic low friction properties in contact with the wire material. Also, the steel substrate used must display a sufficient load carrying capacity and resistance to thermal softening. Of the CVD and PVD coatings evaluated in the tribological tests, a CVD TiC and a PVD CrC/C coating displayed the most promising results.

  • 149.
    Nilsson, Maria
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Tribological testing of some potential PVD and CVD coatings for steel wire drawing dies2011In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 273, no 1, p. 55-59Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to investigate the possibility to replace cemented carbide wire drawing dies with CVD or PVD coated steel dies. Material pick-up tendency, friction and wear characteristics of four different commercial coatings – CVD TiC and PVD (Ti,Al)N, CrN and CrC/C – in sliding contact with ASTM 52100 bearing steel were evaluated using pin-on-disc testing. The load bearing capacity of the coating/substrate composites was evaluated using scratch testing. The results show that the friction characteristics and material pick-up tendency of the coatings to a large extent is controlled by the surface topography of the as-deposited coatings which should be improved by a polishing post-treatment in order to obtain a smooth surface. Based on the results obtained in this study, three different coatings – CrC/C, TiC and dual-layer TiC/CrC/C – are recommended to be evaluated in wire drawing field tests. CrC/C and TiC are recommended due to their intrinsic low friction properties and material pick-up tendency in sliding contact with steel. The dual-layer is recommended in order to combine the good properties of the two coatings CrC/C (low shear strength) and TiC (high hardness).

  • 150.
    Olsson, Lars
    Dalarna University, School of Technology and Business Studies, Material Science.
    Karaktärisering av planhetsställdon i mångvalsarsverk2005Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [sv]

    Projektbeskrivning: Bakgrund: Vid valsning av tunna band med hög hållfasthet används reversibla mångvalsarsverk. Kundkraven är höga vad gäller bandens planhet. Planheten kan styras genom de planhetsställdon som valsverket är utrustat med. Syfte: Förvärva kunskap om hur de olika ställdonen inverkar på planheten. Varje enskilt ställdons inverkan på planheten kan undersökas genom att genomföra en föreskriven förändring av ställdonets läge och därefter utvärdera planhetsförändringen som uppkom. Försöken utförs i ett 20-valsarsverk vid Sandvik Materials Technology i Sandviken. Mål: Förbättra den automatiska planhetsregleringen.

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