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  • 201.
    Tahir, Mohammed
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Mattsson, Robert
    Modeling and analysis of the work-roll grinding depth and the roll wear of the work-roll in Steckel hot rolling mill2013Conference paper (Other academic)
    Abstract [en]

    Thermal expansion, elastic deformation and roll wear are some of the main factors influencing work-roll geometry in the hot rolling process and thereby rolling gap appearance and finally the flatness and profile of the hot rolled material. The purpose of this industrial project was to compile the parameters that influence strip crown of Steckel hot rolling mill, where the influence of these parameters has significant impact to optimize the roll adjustment to achieve a greater availability and higher yield. Focusing on roll wear influence, the evaluation of the grinding depth of work rolls toward roll wear was conducted. In addition to that, the roll wear prediction model in the strip width was developed and roll wear resistance of work-rolls used in a Steckel hot rolling mill has been evaluated. The rolled material used in this project was martensitic stainless chromium steel.

    Hardness measuring with Leeb-method shows that softening occurs in the contact area between strip and work roll, which is still present after a re-grinding process. The grinding depth was varied to investigate the influence on the measured softening. It was clear that an increased grinding depth reduced the softening and the work roll attained a hardness condition close to the one of an unused roll. Wear is a function of the hardness of the roll and thus the wear of the work roll due to different grinding depths was analyzed during actual rolling. The results showed that the wear coefficient remained the same even though the softening was reduced by increasing the grinding depth.

    A model to calculate the wear as a function of the position on the work roll width has been developed in this project. This was done to be able to model the local wear variations during a campaign. This was achieved by simulating the varying force along the contact between strip and work roll and between work roll and back-up roll. The software program used in the evaluation is CROWN426.

     By using Design of Experiments and the software MODDE, a polynomial fit was assigned to the rolling force between the work rolls and the strip (F1) and the force between work rolls and backup rolls (F2) by MLR and PLS, respectively, for faster calculation and the ability to use the model as an on-line tool. Finally, the polynomials, F1 and F2, were used to calculate the wear as a function of the force and number of rotations of the work-roll in contact with the strip. The results show that the model can predict the total varying wear with less than 7 % maximum average error for the rolled steel grade, martensitic stainless chromium steel.

  • 202.
    Tahir, Mohammed
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Sjögren, Björn
    Swerea MEFOS AB.
    LOWWEAR hot rolling WP12012Report (Other academic)
    Abstract [en]

    LOWWEAR hot WP 1 consists of three main parts. The first part includes design of in-line wear and temperature profile gauge for strip and plate mills.

    The second part is the study of roll wear prediction model for hot strip and plate mills.

    The third part includes the evaluation of roll materials (Vancron 40, Sverker 3 (RT60) and Vanadis 23 (ASP23)) with regard to roll wear, surface quality and galling. Roll materials were evaluated experimentally in laboratory and in pilot rolling mill.

     

    The purpose of the first part was to develop a gauge that could be inserted in the mill to measure wear and temperature profiles of both work rolls. This gauge should, be easier and faster to use, than existing gauges and be able to show the shape of the top and bottom roll separately.

    The gauge was designed as an adjustable measuring device so that it could measure the work rolls independent of the distance between them, within a range of 50 – 110 mm. The reason for this design feature is that different mills have different possibilities of opening the work rolls and it can also vary from time to time, depending on back-up and work roll diameters at the moment. The goal was set to 45 mm and the initial design had 45 mm but due to different changes in the design it had to be increased to 50 mm. These design changes delayed the making of the gauge and all original design features were not implemented during the project time. This delay was also the reason why this part was stopped by the project committee before it was finished.

     

    The purpose of the second part is to develop a roll wear prediction model to improve the process control systems of rolling mills by developing accurate roll wear prediction models that takes more influential parameters into consideration, among others. This was done on the basis of measured roll-wear. By means of this model roll wear of three roll grades, HSS, HiCr and IC were evaluated.

     

    A modified prediction model was presented where the influence of work roll and strip grades were evaluated. The contribution of roll wear from contact area (work roll /strip) and between work roll and back-up rolls was investigated. Different finishing mill stands with different work roll arrangements, differences of roll wear of the upper and lower rolls, the influence of lubrication with mixed and similar strip grades were also studied. By adjusting the model to different rolling conditions, hot strip mill, plate mills and steckel mills, possibilities of testing the modified prediction model in operation, offline and online, were investigated. Using some industrial adjustments, the modified model was used for research and master thesis projects for industrial applications. This was done for hot strip mills, plate mills and steckel mills.

     

    The third part was a study of roll materials, using four different industrial lubricants, laboratory strip reduction tests and pilot experiments were conducted and analyzed. Currently used roll type ASP23 was used as reference roll in the evaluation. The severe tribological conditions of “strip reduction test” (scratch test) gave some evaluation measures about surface roughness and galling. Scratches due to galling identified easily and the sliding length determined. Vancron 40 shows promising through its “surface coating” which is integrated into the finished tooling material. It also shows high resistance to galling, toward adhesive wear under severe conditions for low and high reductions.

     

    The pilot experiment was conducted in a 4-high rolling mill at Swerea MEFOS. Final thickness, work roll temperature after rolling and surface roughness of the strip and work rolls was measured and evaluated. The tests were conducted with different industrial lubricants. To achieve the proposed final thickness, five passes were rolled with a constant reduction of 25 %. The character of upper and lower work roll during rolling was also examined. Lubrication was applied in controlled form to the upper and lower work rolls and into the roll gap. The pilot experiment confirms that Vancron 40 is a promising material for work rolls, through its good performance in surface roughness and combination of galling resistance and adhesive wear resistance.

  • 203.
    Tunell, Helena
    Dalarna University, School of Technology and Business Studies, Material Science.
    Synthesis and characterization of photosensitive polymers for liquid crystal alignment2006Licentiate thesis, monograph (Other academic)
  • 204.
    Tunell, Helena
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Osterman, Jesper
    Selo, Muhammed
    Photoinduced reorientation and LC alignment of novel azobenzene-containing monomers2006In: American Chemical Society Polymer Division Meeting, San Francisco, 2006Conference paper (Refereed)
  • 205.
    Vainikainen, Kalevi
    Dalarna University, School of Technology and Business Studies, Material Science.
    Undersökning av sprickors uppträdande och beteende vid valsning av rostfri tråd;: Investigation of Surface Cracks Behaviour in Wire Rod Rolling of Stainless Steel2006Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [sv]

    Marknaden ställer allt högre krav på rostfri valstråd samtidigt som många stålsorter är komplicerade att tillverka. Defekter av olika slag får inte förekomma på kallstukningstråd, fjädertråd och på tråd för andra krävande applikationer. Sprickor som är svåra att upptäcka kan hamna hos kunden, vilket leder till reklamationer. Därmed undersöktes sprickors beteende under valsning genom hela valsverket. Ämnen i olika stålsorter preparerades med längsgående sprickor, värmdes i förvärmningsugnen och valsades till tråd i dimensionen Ø 5,6 mm. Prover togs ut vid befintliga saxar och på färdig tråd. En undersökning gjordes även på en repa som introducerades i början av den kontinuerliga mellansträckan, prover togs ut på samma sätt som för sprickor. Efter provberedning mättes sprickorna med hjälp av ljusmikroskop och analyserades i SEM. Sedan redovisades sprickdjupet genom hela valsverket som ett relativt sprickdjup. Resultaten visade att i de första sticken påverkade formen på sprickan och repan sprickdjupet markant, placeringen i spåret hade också en betydelse. Det kunde konstateras att en ökad sprickbredd med innesluten oxid påverkade sprickdjupet negativt. Sprickdjupet påverkades även av stålets analys. Slutligen kunde konstateras att två av stålsorterna var känsligare för sprickor och att de preparerade sprickorna och den introducerade repan inte kunde elimineras för någon av stålsorterna.

  • 206.
    Valyuhk, Iryna
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Slobodyanyuk, A
    Lumarenko, R
    Skarp, Kent
    Dalarna University, School of Technology and Business Studies, Material Science.
    Optical Proporties of Monochromatic Double-Layer Cholesteric Liquid Crystal Displays2003In: Proceedings of XII International Symposium Advanced Display Technologies, Moscow, Russia, 2003, p. 258-261Conference paper (Refereed)
  • 207.
    Valyuhk, Iryna
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Slobodyanyuk, A.
    Lymarenko, R.
    Skarp, Kent
    Dalarna University, School of Technology and Business Studies, Material Science.
    Optical properties of monochromatic double-layer cholesteric liquid crystal displays2003In: Advanced display technologies, Moscow, Russia, 2003Conference paper (Refereed)
  • 208.
    Valyuhk, Iryna
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Slobodyanyuk, A
    Skarp, Kent
    Dalarna University, School of Technology and Business Studies, Material Science.
    Optical Characteristics of Double-layer Cholesteric Liquid Crystal Displays2003In: Proceedings of International Display Research Conference (IDRC), Phoenix, USA, 2003, p. 203-206Conference paper (Refereed)
  • 209.
    Valyukh, Iryna
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Slobodyanyuk, A
    Valyukh, S
    Osterman, Jesper
    Dalarna University, School of Technology and Business Studies, Material Science.
    Skarp, Kent
    Dalarna University, School of Technology and Business Studies, Material Science.
    Using the Jones matrix for simulation of light propagation in anisotropic media2003In: Journal of optical technology (Print), ISSN 1070-9762, E-ISSN 1091-0786, Vol. 70, no 7, p. 470-473Article in journal (Refereed)
  • 210.
    Valyukh, Iryna
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Slobodyanyuk, A.
    Valyukh, S.
    Sorokin, V.
    Osterman, Jesper
    Dalarna University, School of Technology and Business Studies, Material Science.
    Skarp, Kent
    Dalarna University, School of Technology and Business Studies, Material Science.
    On accuracy of the Jones matrix method for simulation of light propagation in twisted nematic liquid crystals2002In: Proc. of the 11th Int. Symp. Advanced Display Technologies, UkraineArticle in journal (Refereed)
  • 211.
    Valyukh, Iryna
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Slobodyanyuk, A.
    Valyukh, S.
    Sorokin, V.
    Osterman, Jesper
    Dalarna University, School of Technology and Business Studies, Material Science.
    Skarp, Kent
    Dalarna University, School of Technology and Business Studies, Material Science.
    Simulation of light scattered by reflective polarizer with a rough metallic surface2002In: Eurodisplay 2002, Nice, France, 2002Conference paper (Refereed)
  • 212.
    Valyukh, Iryna
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Valyukh, S.
    Skarp, Kent
    Dalarna University, School of Technology and Business Studies, Material Science.
    Theoretical study of the optical properties of low voltage stacked cholesteric liquid-crystal displays2004In: Asia display, 2004Conference paper (Refereed)
  • 213.
    Valyukh, Sergiy
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Osterman, Jesper
    Dalarna University, School of Technology and Business Studies, Material Science.
    Adås, C.
    Skarp, Kent
    Dalarna University, School of Technology and Business Studies, Material Science.
    Cell gap measurements of flexible reflective TN- and STN-LC cells2004In: SID international symposium, 2004Conference paper (Refereed)
  • 214.
    Valyukh, Sergiy
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Osterman, Jesper
    Dalarna University, School of Technology and Business Studies, Material Science.
    Skarp, Kent
    Dalarna University, School of Technology and Business Studies, Material Science.
    Simple Spectroscopic Method to Measure Cell Gap and Twist Angle of TN-LCD2003In: International display research conference, 2003Conference paper (Refereed)
  • 215.
    Valyukh, Sergiy
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Osterman, Jesper
    Dalarna University, School of Technology and Business Studies, Material Science.
    Skarp, Kent
    Dalarna University, School of Technology and Business Studies, Material Science.
    Chigrinov, V.
    Optical performance of bistable reflective and transflective ferroelectric LCDs2005In: SID international symposium, Boston, 2005Conference paper (Refereed)
  • 216.
    Valyukh, Sergiy
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Osterman, Jesper
    Dalarna University, School of Technology and Business Studies, Material Science.
    Valyuhk, Iryna
    Dalarna University, School of Technology and Business Studies, Material Science.
    Skarp, Kent
    Dalarna University, School of Technology and Business Studies, Material Science.
    Characterization of flexible reflective liquid crystal cells2005In: Journal of the Society for Information Display, ISSN 1071-0922, E-ISSN 1938-3657, Vol. 13, no 6, p. 501-506Article in journal (Refereed)
    Abstract [en]

    We consider peculiarities in testing flexible reflective liquid-crystal (LC) cells. Several new methods for measuring optical retardation of filled reflective LC cells on plastic substrates are proposed. Cases when the plastic is anisotropic and the LC cell consists of either one or two internal polarizers are studied. The majority of proposed methods can be applied for transmissive LC cells as well as for measuring twist angle.

  • 217.
    Valyukh, Sergiy
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Rybalochka, A.
    Sorokin, V.
    Tytarenko, P.
    Skarp, Kent
    Dalarna University, School of Technology and Business Studies, Material Science.
    A method for measuring reflective twist nematic liquid crystal cell properties2003In: Advanced display technologies, Moscow, Russia, 2003Conference paper (Refereed)
  • 218.
    Valyukh, Sergiy
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Rybalochka, A
    Sorokin, V
    Tytarnenko, T
    Skarp, Kent
    Dalarna University, School of Technology and Business Studies, Material Science.
    A method for measuring reflective twist nematic liquid crystal cell proporties2003In: Proceedings of XII International Symposium Advanced Display Technologies, Moscow, Russia, 2003, p. 254-257Conference paper (Refereed)
  • 219.
    Valyukh, Sergiy
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Slobodyanyuk, A.
    Sorokin, V.
    Skarp, Kent
    Dalarna University, School of Technology and Business Studies, Material Science.
    Computer simulation of scattering properties of cholesteric liquid crystal displays2001In: European conference on liquid crystals, Halle, Germany, 2001Conference paper (Other academic)
  • 220.
    Valyukh, Sergiy
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Valyuhk, Iryna
    Dalarna University, School of Technology and Business Studies, Material Science.
    Skarp, Kent
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Spectrophotometric determination of reflective liquid crystal cell parameters2006In: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 99, no 5Article in journal (Refereed)
    Abstract [en]

    We introduce a method for the determination of the optical retardation, its wavelength dispersion, the cell twist angle, and the orientation of the input director in a reflective liquid crystal (LC) cell. These parameters are found from the extremes of a characteristic function defined as a sum of two spectral reflectivities of the LC cell placed between a pair of linear polarizers. The reflectivities are measured for two cell orientations, one of which is arbitrary and the other one is turned through 45°. Both theoretical analysis and experimental procedures are presented. Excellent agreement between the experiment and our theory has been found. The proposed method can be applied to the measurement of reflective LC cells with small and large cell gaps, as well as cells with small and large twist angles.

  • 221.
    Valyukh, Sergiy
    et al.
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Valyukh, Iryna
    Dalarna University, School of Technology and Business Studies, Materials Technology.
    Adås, C.
    Chigrinov, V.
    Skarp, Kent
    Dalarna University, School of Technology and Business Studies, Material Science.
    Reflective liquid crystal cell parameters2004In: Asia display, 2004Conference paper (Refereed)
  • 222.
    Venkat, Thangella
    Dalarna University, School of Technology and Business Studies, Material Science.
    Synthesis of Photosensitive Polymers2004Independent thesis Advanced level (degree of Master (Two Years))Student thesis
  • 223.
    Vishwas, Gongidi
    Dalarna University, School of Technology and Business Studies, Material Science.
    Viewing Angle Properties of Reflective LCDs2004Independent thesis Advanced level (degree of Master (Two Years))Student thesis
  • 224. Wadman, Boel
    et al.
    Eriksson, Jenny
    Dalarna University, School of Technology and Business Studies, Material Science.
    Olsson, Mikael
    Dalarna University, School of Technology and Business Studies, Material Science.
    Schedin, Erik
    Madsen, Erik
    Bay, Niels
    Influence of surface texture on the galling characteristics of lean duplex and austenitic stainless steels2010In: Duplex World 2010 Conference & Exhibition, Beaune, France, 2010Conference paper (Other academic)
    Abstract [en]

    Two simulative test methods were used to study galling in sheet forming of two types of stainless steel sheet: austenitic (EN 1.4301) and lean duplex LDX 2101 (EN 1.4162) in different surface conditions. The pin-on-disc test was used to analyse the galling resistance of different combinations of sheet materials and lubricants. The strip reduction test, a severe sheet forming tribology test was used to simulate the conditions during ironing. This investigation shows that the risk of galling is highly dependent on the surface texture of the duplex steel. Trials were also performed in an industrial tool used for high volume production of pump components, to compare forming of LDX 2101 and austenitic stainless steel with equal thickness. The forming forces, the geometry and the strains in the sheet material were compared for the same component. It was found that LDX steels can be formed to high strain levels in tools normally applied for forming of austenitic steels, but tool adaptations are needed to comply with the higher strength and springback of the material.

  • 225.
    Waltersson, Erik
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Eriksson, Göran
    Dalarna University, School of Technology and Business Studies, Material Science.
    Undersökning av steady state och utvärdering av valskraft och friktion vid kallvalsning av aluminium2011Independent thesis Basic level (degree of Bachelor)Student thesis
    Abstract [sv]

    The purpose with this thesis was to examine the cold rolling mill located at Högskolan Dalarna and to stabilize the rolling process, to achieve steady state. Experiments with cold rolling of an aluminium strip have given results for rolling force, friction, reduction, strip tension and strain hardening. Results show that steady state has been found for the experiments with roll force and strain hardening, and not been found for the experiments with friction and reduction. Results show that increased strip tension gives lower roll forces. The roll force equation of Stone shows comparable results with reality for dry contact with reductions up to 30 %, but starts being incomparable with higher reductions. The roll force equation of Stone shows a bit higher roll forces than reality gave, but was comparable within reductions from 13 to 50 %. Experiments have shown that the aluminium strip has gone through strain hardening. Experiments show how the set roll gap did not yield the desired thickness reduction, there for the elastic spring constant for the rolling mill was examined and determined to be 417 N / mm for the specific alloy band. The influence of tension strip for roll force was examined and Results confirm the theory about how the roll force is decreased by increasing tension strip. The work rolls started to slip against the alumina strip as high tension strip; 70 N/mm2, gave low roll force; < 15kN.

  • 226.
    Wang, Lu
    et al.
    Dalarna University, School of Technology and Business Studies, Material Science.
    Birgerson, J.
    Osterman, Jesper
    Dalarna University, School of Technology and Business Studies, Material Science.
    Skarp, Kent
    Dalarna University, School of Technology and Business Studies, Material Science.
    Voit, W.
    Inkjet printing of linearly photopolymerizable polymer as alignment in LCD2005In: SID international symposium, Boston, 2005Conference paper (Refereed)
  • 227. Wang, X.T.
    et al.
    Yu, Z.L.
    Siwecki, Tadeusz
    Engberg, Göran
    Dalarna University, School of Technology and Business Studies, Material Science.
    Sun, Z.Q
    Physical Modeling on Recrystallization of Austenite in Steels in Thermo-mechanical Processing2007In: Materials Science Forum, ISSN 1662-9752, Vol. 561-565, p. 1953-1956Article in journal (Other academic)
    Abstract [en]

    A physical model for austenite recrystallization of steel concerning TMCP is developed. Dislocation density plays a key role as recrystallization driving force. The dislocation density change is a result of competition between dislocation generation and dynamic recovery. Recrystallization is described as a nucleation-growth process. An abnormal subgrain growth mechanism is introduced for nucleation. A few subgrains fulfilling abnormal growth conditions will stand out and become nuclei of recrystallization. The recrystallized grain grows to the deformed materials driven by the stored energy. Oswald ripening occurs for grains surrounded by recrystallized grains. The models were verified by laboratory simulation results for selected austenite stainless steels. It showed good agreement between predicted and experimental results.

  • 228.
    Westin, Tommy
    Dalarna University, School of Technology and Business Studies, Material Science.
    Induktiv provning av ferritiskt rostfritt stå2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The report examines the factors which may be a contributing cause to the problems that are present when ferritic stainless steel are eddy current tested in a warm condition. The work is carried out at Fagersta Stainless AB in Fagersta which manufactures stainless steel wire. In the rolling mill there is an eddy current equipment for detection of surface defects on the wire. The ferritic stainless steels cause a noise when testing and this noise complicates the detection of defects.Because of this, a study was made of how the noise related to factors such as steel grade, temperature, size and velocity. By observing the signal and with the possibilities to change the equipment settings the capability to let a signal filter reduce the noise level were evaluated. Theories about the material's physical properties have also been included, mainly the magnetic properties, electrical conductivity and the material's tendency to oxidize.Results from the tests show that a number of factors do not affect the inductive test significantly and to use a filter to reduce the noise level does not seem to be a viable option. The level of noise does not relate to the presence of superficial particles in form of oxides.The ferritic stainless steels showed some difference in noise level. Which noise level there was did match well with the steels probability for a precipitation of a second phase, and precipitation of austenite may in this case contribute to noise when using an eddy current instrument.The noise is probably due to some physical material property that varies within the thread.

  • 229.
    Wuopio, Christina
    Dalarna University, School of Technology and Business Studies, Material Science.
    Kylning av valsar vid spårvalsning2005Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [sv]

    Inom Ruukki Fundia Special Bar finns tre liknande förpar, ett i Smedjebacken och två i Boxholm varav ett i finverket och det andra i mediumverket. Valsarna levereras av Åkers Sweden AB och är av samma kvalité, (gjutna H-SG-P-Mo-48 värmebehandlat-segjärn-perlitisk struktur-molybdenlegerat och med hårdhet 48 Shore) det som skiljer är radien. I mediumverket utsätts valsarna för ett hårt slitage både genom sprickbildning och ojämn yta medan de två andra förparen inte slits lika hårt. Idag används en vals i cirka sex månader, under den tiden sker en omsvarvning. På grund den rikliga sprickbildningen kan bara en omsvarvning ske på grund av att de djupa sprickorna gör att 12-16mm på diametern svarvas bort vid varje tillfälle. En andra omsvarvning gör att valsens radie blir för liten. Företaget vill minimera sprickbildningen för att kunna svarva om valsarna ytterligare en gång och på det sättet förbättra valsekonomin. Syftet med detta examensarbete är att undersöka möjligheter till varför denna sprickbildning och ytojämnhet uppstår. Sprickbildning är en följd av bland annat termiska ojämnheter på valsytan som orsakas växlande uppvärmning från hetan och kylning från kylmedlet. En annan orsak till sprickbildning kan vara överbelastning av valsarna. Temperaturer på valsar, ämne och vatten kommer att undersökas för att få en förståelse för vart problemet kan ligga. Det har gjorts beräkningar på valskrafter och moment för undersökningar i fråga om överbelastning. Programmet Steeltemp har används för att studera temperatur- förändringar i valsen under valsning. Även jämförelser mellan förparen i Smedjebacken och finverket i Boxholm har studerats.

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