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Development of a heat treatment method to form a duplex microstructure of lower bainite and martensite in AISI 4140 steeClaesson, Erik January 2014 (has links)
Research on bainite and martensite structures has indicated that lower bainite needles have a refining effect on the lath martensitic structure. Lower bainte needles partitions prior austenite grains and will consequently have a refining effect on the subsequent formed lath martensite. Smaller austenite grains will result in smaller lath martensitic packets and blocks and will result in enhanced mechanical properties. In order to create a variation of lower bainte structure in a matrix of martensite, two different heat treating methods were tested. The work was focused towards the formation of lower bainite during isothermal heat treating in molten salt, above and below the MS-temperature. Both un-tempered and tempered samples were analyzed .Two different materials were tested, both were AISI 4140 but with a slightly difference in hardenability. The material provided by Ovako Steel is 326C and 326F the later had a higher hardenability. In order to better distinguish the two structures from each other when studied under a microscope, a variation of etching methods were tested. It was possible to create a variation of lower bainite structures in a matrix of martensite. 326F shows less amount of lower bainite and provides a higher average surface hardness before tempering.
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Increase the capacityof continuous annealing furnaces at OvakoDahlqvist, v January 2012 (has links)
The capacity of soft annealing of low alloyed tubes at Ovako’s continuous annealing furnaces have been evaluated by comparing how it is done today with information from published and internal articles on the subject. It was found that it is possible to reduce the cycle time by 30 % for one furnace, 55 % for one furnace and 72 % for two furnaces. Two separate fullscale tests were made to assess whether the faster soft annealing procedure was feasible. The tests were performed without any reconstruction of the furnace and were made by continuously vary the speed of the batch inside thefurnace. The temperature in the batch was measured and compared with results from computer simulations of the heating/cooling sequences. The computer simulations were performed in COMSOL. The soft annealing was evaluated according to the SEP-520 standard ,which means evaluating the microstructure and hardness. The results show that the faster heat treatment could yield lower grades than today but still meet it’s requirements. In order to achieve this increase a reconstruction of the furnaces is needed and the reconstruction is briefly treated in the report. Ideas to further increase the speed of the soft annealing procedure are also presented.
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Precipitation Study in a High Temperature Austenitic Stainless Steel using Low Voltage Energy Dispersive X-ray SpectroscopyGharehbaghi, Ali January 2012 (has links)
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.
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3D study of non-metallic inclusions by EEmethod and use of statistics for the estimationof largest size inclusions in tool steel.Safa, Meer January 2010 (has links)
The control of non-metallic inclusions is very important for the improvement of performance during the application of tool steel. This present study was performed to see the effect of changing of some process parameters during the vacuum degassing of the melt and how these changing parameters affects the characteristics of inclusions in tool steel. The main parameters that were changed during the vacuum degassing were the change of induction stirring, argon flow rate from both the plug 1 and 2 and different ladle ages for different heat. Electrolytic extraction method was used to observe the morphology and characteristics of inclusions as a 3 dimensional view in tool steel. Four lollipop samples from four different heats were used for the experiment and all the samples were after vacuum (AV) degassing. In this study four different types of inclusions were found and they are classified as type 1, 2, 3 and 4. Of them type 1 inclusion was the major one with mostly spherical shaped. This study shows that among the three parameters, induction stirring has the biggest effect for the total number of inclusions per volume in the sample than the other two parameters Heat 4A showed the lowest number of inclusions per volume comparing with the other heats. The main reason behind this can be said that the induction stirring was the lowest comparing with the other heats with moderate argon flow and ladle age of 12. Extreme value analysis was used in this study to predict the probability of getting largest size inclusions in a certain volume of the metal. For the prediction of the largest inclusion size, both the electrolytic extraction (3D) and cross-sectional (2D) method was used. Later in this study comparison was done to determine the accuracy of both the methods and it is concluded that for the type 1 inclusions electrolytic extraction method shows almost similar trend with cross-sectional method and electrolytic extraction method shows better accuracy for the prediction of largest size inclusions than the cross-sectional method. Electrolytic Extraction method is also applicable for the prediction of largest size inclusions for multiple types of inclusions.
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A study of flow fields during filling of a samplerZhang, Zhi January 2009 (has links)
More and more attention has been paid to decreasing the number and size of non-metallic inclusions existing in the final products recently in steel industries. Therefore, more efforts have been made to monitor the inclusions' size distributions during the metallurgy process, especially at the secondary steelmaking period. A liquid sampling procedure is one of the commonly applied methods that monitoring the inclusion size distribution in ladles, for example, during the secondary steelmaking. Here, a crucial point is that the steel sampler should be filled and solidified without changing the inclusion characteristics that exist at steel making temperatures. In order to preserve the original size and distributions in the extracted samples, it is important to avoid their collisions and coagulations inside samplers during filling. Therefore, one of the first steps to investigate is the flow pattern inside samplers during filling in order to obtain a more in-depth knowledge of the sampling process to make sure that the influence is minimized. The main objective of this work is to fundamentally study the above mentioned sampler filling process. A production sampler employed in the industries has been scaled-up according to the similarity of Froude Number in the experimental study. A Particle Image Velocimetry (PIV) was used to capture the flow field and calculate the velocity vectors during the entire experiment. Also, a mathematical model has been developed to have an in-depth investigate of the flow pattern in side the sampler during its filling. Two different turbulence models were applied in the numerical study, the realizable k-ε model and Wilcox k-ω model. The predictions were compared to experimental results obtained by the PIV measurements. Furthermore, it was illustrated that there is a fairly good agreement between the measurements obtained by PIV and calculations predicted by the Wilcox k-ω model. Thus, it is concluded that the Wilcox k-ω model can be used in the future to predict the filling of steel samplers.
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Modeling the Microstructure Evolution During and After Hot Working in Martensitic SteelSafara Nosar, Nima January 2021 (has links)
In this study, the goal is to predict the microstructure evolution during and after the hot working of a martensitic stainless steel with 13% chromium using a physically-based model in the form of a MATLAB toolbox. This model is based on dislocation density theory and consists of coupled sets of evolution equations for dislocation, vacancies, recovery, recrystallization, and grain growth. The focus in this work is on the flow stress calculation and the effect of second phase particles on the strengthening mechanisms in the material at elevated temperatures. Recovery and recrystallization are also studied for this alloy during deformation and following stress relaxation. The experimental part of this work was performed with a Gleeble thermo-mechanical simulator over the temperature range of 850 to 1200°C. Samples were investigated later by a light optical microscope (LOM) and a scanning electron microscope (SEM) equipped with energy dispersive X-ray spectroscope (EDS). Hardness test and phase isolation were also performed on the samples and the results are compared with the modeling results. The model can satisfactorily predict the grain growth, recovery, recrystallization, and flow stress for this alloy. Further investigation on the second phase particles showed that the measured mean size of carbides has a good agreement with what is obtained from the model and the hardness values. On the other hand, the modeled volume fraction of the carbides followed a slightly different trend comparing to hardness values, and phase isolation results at temperatures higher than 1000°C. Additionally, the Ms temperature and fraction of the martensite phase are calculated for quenched samples where the results are following the measured hardness values. Finally, the Zener-Hollomon parameter (Z) and its relation to the flow stress and the activation energy for deformation are defined. The dynamic recrystallization (DRX) kinetic is modeled and the fraction DRX was calculated at various temperatures and strain rates for this alloy. / I denna studie är målet att förutsäga mikrostrukturutvecklingen under och efter varmbearbetning i ett martensitiskt rostfritt stål med 13 % krom med hjälp av en fysisk baserad modell i form av en MATLAB verktygslåda. Denna modell är baserad på en teori för dislokationstäthet och bestårav kopplade uppsättningar av evolutionsekvationer för dislokation, vakanser, återhämtning, rekristallisation och kornstillväxt. Fokus i detta arbete är beräkning av flytespänningen och effekten av sekundärfaspartiklar på härdningsmekanismerna i materialet vid höga temperaturer. Återhämtning och rekristallisation studeras också för denna legering under deformation och efter spänningsrelaxation. Den experimentella delen av detta arbete utfördes med en Gleeble termomekanisk simulator inom temperaturområdet 850 till 1200°C. Proverna undersöktes senare med ett ljust optiskt mikroskop (LOM) och svepelektronmikroskop(SEM) utrustad med energidispersiv spektroskopi (EDS). Hårdhetstest och fasisolering utfördes också på proverna och resultaten jämförs med modelleringsresultaten. Modellen på ett tillfredsställande sätt kan förutsäga korntillväxt, återhämtning, rekristallisation och flytspänningen för denna legering. Vidare undersökning av partiklarna i sekundärfasen visade att den uppmätta medelstorleken för karbider har bra överensstämmelse med vad som erhålls från modellen och hårdhetsvärdena. Den modellerade volymfraktionen av karbiderna följde en något annorlunda trend vid temperaturerna högre än 1000°C jämfört med hårdhetsvärden och fasisoleringsresultat. Dessutom beräknas Ms temperaturen och fraktionen av martensitfasen för släckta prover där resultaten följer de uppmätta hårdhetsvärdena. Slutligen definieras Zener-Hollomon-parametern (Z) och dess förhållande till flytspänningen och aktiveringsenergin för deformation. Den kinetiska dynamiska rekristallisation (DRX) modelleras och fraktionen DRX beräknades vidolika temperaturer och töjningshastigheter för denna legering.
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Process Parameters for Creation of Porous Stainless Steel SurfacesHultstein, Eric January 2011 (has links)
Detta examensarbete ämnar att undersöka värmebehandlingsmetoder för att skapaporösa austenitiska rostfria stål samt utvärdera ifall dessa ytor medför förbättringargentemot referensmaterialen. De porösa ytorna skapades genom en två-stegs metod.Prover oxiderades initialt i en fuktig eller torr argon atmosfär för att sedan reducerasi ren vätgas. De material som använts i denna studie är austenitiska rostrifa stål ienhlighet med standardena 1.4301 (304), 1.4404 (316L), 1.4435 (316L) och F-138 (316LVM).Oxidationsprocessen genomfördes under temperaturer över 630 ◦ C under 150 - 1200 s.Efteråt reducerades proverna i ren vätgas under 150 - 2400 s.För att karakterisera processen undersöktes proverna med svepelektronmikroskopsamt elektron-dispersiv röntgenspektrometer. Vissa prover har även analyserats medhjälp av ljusoptiskt mikroskop, bildanalys samt värmeledningsförmåga. Resultaten visarklart att alla undersökta material kan uppvisa porösa strukturer, dock kan inte allaprocessparametrar möjliggöra uppkomsten av dessa. Generellt sett beror porositeten påden underliggande strukturen skapade under oxidationen. Det har ännu inte varit möjligtatt karaterisera några kristallstrukturer, kemisk analys tyder dock på närvaro av kromoxid,(Cr,Fe) spineller samt järnoxider. Resultaten konstaterar att en kort oxidationstid normaltbildar kromoxid medan längre oxidation medför uppkomsten av järnoxider. En ökadreduktionstid leder till större och färre porer jämfört med kortare reduktionstider. Kemiskaanalyser visar enhälligt att porösa strukturer innahåller till största del järn. En trolig orsaktill detta beteende kan kopplas till det fenomen där krom förångas under oxidation i fuktigaatmosfärer. Följaktikligen blir även ytan känslig för korrosion då majoriteten av krom harförsvunnit.Utvärdering av egenskaperna hos dessa ytor visar en tydlig förbättring i värmeledning vianaturlig konvektion. Värmeväxlingen mellan två uider uppvisar dock inte någon störreskillnad förutom under låga ödeshastigheter då en porös yta tenderar att transporterabort mer värme / This work aim to investigate a novel process by means of process parameters for creationof porous austenitic stainless steels surfaces as well as investigate if they permit anyimprovements compared to reference materials. Porous surfaces were created by a two-step method; samples were initially oxidised in a wet argon atmosphere and subsequentlyreduced in a pure hydrogen. The materials used in this investigation are all stainless steelswith specications according to steel grades 1.4301 (304), 1.4404 (316L), 1.4435 (316L)and F-138 (316LVM). The oxidation process is performed above 630 ◦ C for 150 - 1200 s in aow of wet argon or dry air and reduction is performed with a ow hydrogen for 150 - 2400 s.In order to understand the heat treatment processes, samples were characterised by usinga scanning electron microscope together with an electron dispersive x-ray spectrometer.However, light optical microscopy, image analysis and heat transfer measurement werealso used. Results show that all materials can obtain porous structures even though itis evident some process parameters cannot support successful creation of porosity. Ingeneral, the porosity depends on the structure created upon oxidation. It has not beenpossible to identify any crystal structures but compositional analysis as well as previousliterature suggest presence of chromia, (Cr,Fe) spinels and iron oxides. It is concluded thatshort time oxidation frequently creates chromia layers and prolonged oxidation inducesiron oxides due to breakaway oxidation. An increased reduction time results in larger andfewer pores. Compositional analyses show that all porous morphologies are created withina very iron rich layer. It is suggested that wet oxidation promote chromium evaporation,which consequently reduces the amount of chromium in the surface and enables iron oxideto rapidly form. Furthermore, results show that the porous layer is very susceptible tocorrosion as almost no chromium is present after the heat treatment. Evaluation of the properties of porous surfaces reveals a signicant improvement in heattransfer due to natural convection. Heat exchange between uids is though not enhancedgreatly by porous surfaces, a small improvement can be seen for low ow rates but for largerows no improvement is found.
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Konceptutveckling av en caterpillar med inriktning på kvalitet : En utvecklingsprocessKarlsson, Hampus, Karlsson, Anton January 2017 (has links)
When transporting a sea cable, what is commonly called a caterpillar is used, but the most common said is a cable tensioner. These machines can be found in a flurry of different variants, where there are a multitude of competitors, which applies demands to having an extremely distinctive machine. Therefore from a market analysis it have been identified that a lack of quality regarding the machines are a factor. A poor quality shortage that usually occurs in hard weather conditions, but this is something that should not happen as it may lead to machine breakdown. Semcon AB in Karlskrona constructs and then collaborates with Ronneby Svets & Smide, who manufacture cable carousels, armrests and other equipment for the cable industry but not the cable tensioner that are ordered separately by external companies. This is the background to why the project is created because Semcon sees a need to eliminate this bottleneck and also expand their product portfolio for customer recovery. The aim it therefore, together with Semcon, develop a new concept for a completely new cable tensioner with given preferences, rough drawing and selection of qualitative features for the machine in order to be competitive with its future overall solution for the cable industry. To find a solution to the described problem, a product development process has been followed to establish structure. The process include a planning, concept development, design and detailed development phase. From the first phase, a wide understanding of how the complex machine works and where its deficiencies may be. Even hidden customer needs in form of interviews with cable manufacturers in Karlskrona and with industries that handle sea cable were conducted to get a broader spectrum. The needs are transformed into specifications to generate concepts based on the rankings of the measurably formulated specifications. Followed up by an evaluation where the best concepts were taken to the design phase and detailed development. All design calculations have been made, either by hand or with computer-based programs. The work has resulted in an innovative concept of a whole cable tensioner with all key components, rough drawing, together with a new thinking solution regarding the contact face between the cable and the machine, developed through experiments and theory studies. As this project is very broad, the overall project has been divided into two master thesis works and all electronics are handles by an electrical/automation company. Therefore, for a broader understanding and information about functionality, reference is made to the second project “Konceptutveckling kring funktionerna hos en kabeldragare” authored by Anton Hansson. It is extremely important to mention that the outcome of this project is intended to be a concept for a new innovative cable tensioner. This means that with future work on the concept, which includes continued depth of calculation and further contact with suppliers, can provide an opportunity to manufacture the generated concept. Another development area Semcon must proceed with is to review the safety routines of the machine. The authors of this report believe that a highly competitive solution has been presented, and that work contributes to a strong foundation for the development of transporting sea cable technology in the future with the help of this innovative concept.
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Coupled flux nucleation model applied to the metallic glass AMZ4 / Kopplad flödesmodell applicerad på det metalliska glaset AMZ4Tidefelt, Mattias January 2021 (has links)
Additive manufacturing (AM), also known as 3D-printing, has made it possible to produce components made of bulk metallic glass (BMG) which have remarkable properties compared to parts made of conventional alloys. A metallic glass is a metastable noncrystalline alloy that form if a melt is quenched with a sufficient cooling rate. Research on systems with low critical cooling rates have made the maximum dimensions of these alloys to grow to what is called BMG's. The high local cooling rate obtained during AM makes it in principle possible to bypass the dimension restrictions that otherwise have been present when creating these alloys but the procedure is complex. It is believed that oxygen impurities in the powder feedstock material used during AM of Zr-based alloys makes it favourable for nucleation of stable crystalline phases at lower activation energies which hinders fully glass features to develop. The purpose of this thesis is to investigate how the limiting solute concentration in the bulk of the AM produced alloy AMZ4 (Zr59.3Cu28.8Al10.4Nb1.5(at\%)) impact the nucleation. Using a numerical model based on classical nucleation theory (CNT) that couples the interfacial and long range fluxes makes it possible to study how impurities impact the nucleation event. However, missing oxygen dependent data makes this a study on how limiting solute impact the nucleation in AMZ4. The numerical model is validated against earlier work and the results obtained from the simulations on AMZ4 shows a strong connection between the nucleation event and the limiting solute concentration. Further investigations on phase separation energies and the production of concentration dependent time-temperature-transformation (TTT) diagrams are needed to fully describe the connection to oxygen concentration. Nevertheless, the implemented model captures important features that the classical model cannot describe which needs to be taken into account when describing the nucleation in AMZ4. / Friformsframställning (eng. additive manufacturing (AM)), också känt som 3D-printing, har gjort det möjligt att producera komponenter gjorda av bulkmetallglas (eng. bulk metallic glass (BMG)) vilka har anmärkningsvärda egenskaper jämfört med delar gjord av konventionella legeringar. Ett metalliskt glas är en metastabil icke kristallin legering som skapas om en smälta släcks med en tillräcklig kylhastighet. Forsking på system med låga kritiska kylhastigheter har gjort att de maximala dimensionerna av dessa legeringar har ökat till vad som kallas BMG's. Den höga lokala kylhastigheten som erhålls under AM gör att dimensionsrestriktionerna principiellt kan kringgås vilka annars är närvarande vid skapandet dessa legeringar men proceduren är komplex. Det är trott att orenheter av syre i pulver-råvarumaterialet som används vid AM av Zr-baserade legeringar gör det fördelaktigt för kärnbildning av stabila kristallina faser vid lägre aktiveringsenergier vilket hindrar fulla glas egenskaper från att utvecklas. Syftet med denna uppsats är att undersöka hur den begränsande lösningen påverkar kärnbildningsförloppet i den AM producerade legeringen AMZ4 (Zr59.3Cu28.8Al10.4Nb1.5(at\%)). En numerisk modell baserad på klassisk kärnbildningsteori (eng. classical nucleation theory (CNT)) som kopplar gränsskikt- och långdistans-flödet gör det möjligt att studera hur orenheter påverkar kärnbildningsförloppet. Syreberoende data gör dock detta till en studie om hur den begränsande lösningen påverkar kärnbildningen i AMZ4. Den numeriska modellen valideras mot tidigare arbeten och resultaten från simuleringarna av AMZ4 visar ett starkt samband mellan kärnbildningsförloppet och den begränsade lösningskoncentrationen. Vidare studier rörande fas-separeringsenergier och framställningen av koncentrationsberoende tid-temperature-transformation (eng. time-temperature-transformation (TTT)) diagram behövs för att till fullo beskriva kopplingen till syrekoncentrationen. Den implementerade modellen fångar dock viktiga egenskaper som den klassiska modellen inte kan beskriva vilka måste tas hänsyn till när kärnbildning i AMZ4 ska beskrivas.
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Online Metallurgical Mass Balance and Reconciliation / On-line metallurgisk massbalansering och haltjusteringAndersson, Emil January 2021 (has links)
In mineral processing, one of the most important and versatile separation methods is flotation. Flotation utilizes the different surface properties of the valuable minerals in the ore to separate them from the less valuable gangue material in the ore. Crushed and ground ore is mixed with water and fed into flotation tanks. In the flotation tanks, the particles of valuable mineral are made hydrophobic. That way, they can be floated by attaching to air bubbles and gather on top of the flotation tank as froth. This froth, containing higher concentrations of valuable mineral, is recovered and then processed further. The flotation circuit is controlled and maintained using measurements on the mass flows and grades of different materials. Due to economical, practical, and technological limitations, these measurements are performed at a chosen number of points in the circuit and at discrete points in time. Poor measurement data can have devastating consequences if the operators are left with limited information and errors in the circuit remain undetected. The accuracy of the acquired measurements is improved by performing mass balance and reconciliation. Traditionally, mass balance uses the sum of the total mass flows and the average grades over long times to avoid including the internal mass of the circuit in the calculations. It is desirable to perform mass balance directly to allow for faster intervention if any failures occur in the circuit during the on-line process. This report describes an on-line dynamic approach towards mass balancing and reconciliation of the mass flows and grades in a flotation circuit. Here, physical models of the flotation circuit are used to construct mass balance constraints using interpolation and test functions and the mass balance problem is posed as an optimization problem. The optimization problem is to adjust the assay such that the residual, the difference between the measured and the adjusted assay, is minimized while maintaining mass balance. An implementation in MATLAB and tests on synthetic data show that the dynamic formulation of mass balance does adjust 'erroneous' measurements such that mass balance is fulfilled. Given this result, there are still important aspects of the implementation that have to be addressed. The model uses the unknown and cell specific parameters flotation rate and recovery. Thus, these must be found or properly modeled. This report proposes a possible model for flotation rate as well as a strategy to find the recovery. The requirements of accuracy and speed of the implementation are also discussed. Possible next steps of this project is to further confirm a time effective implementation using synthetic data. Consequently, the implementation can be adapted for natural data in order to verify correctness of models. / I malmanrikning, är flotation en av de viktigaste och mest mångsidiga metoderna. Flotation utnyttjar de fysikaliska ytegenskaperna som partiklar av värdemineral har för att separera dessa från det mindre värdefulla gråberget i malmen. Krossad och mald malm blandas med vatten och matas in i flotationstankar. I flotationstankarna görs partiklarna av värdemineral hydrofobiska. På så vis kan de fästa sig vid luftbubblor och flyta till ytan och bilda ett skum. Detta skum samlas sedan ihop och behandlas vidare eftersom det innehåller en högre koncentration av värdemineral. Flotationskretsen styrs och underhålls med hjälp av mätningar av massflödena och halterna av de olika ämnena som finns i kretsen. På grund av ekonomiska, praktiska, och teknologiska hinder kan dessa mätningar bara göras på ett utvalt antal punkter i kretsen samt bara vid diskreta tillfällen. Felaktigt data kan ha förödande konsekvenser om operatörerna lämnas med begränsad information och processen fortlöper med oupptäckta fel. Mätsäkerheten kan förbättras med hjälp av massbalansering och haltjustering. Traditionellt görs massbalansering genom att summera den totala massan som löpt genom kretsen samt medelvärden av halterna över lång tid för att undvika att räkna in den interna massan i systemet. Det är önskvärt att utföra massbalansering direkt för att möjliggöra snabbare ingrepp ifall fel uppstår i kretsen under den fortlöpande processen. Denna rapport beskriver en dynamisk lösning för massbalansering och justering av massflöden och halter i en flotationskrets. Här används fysikaliska modeller av kretsen för att konstruera bivillkor för massbalans med hjälp utav interpolation och testfunktioner och massbalanseringsproblemet ställs upp som ett optimeringsproblem. Optimeringen sker genom att justera mätserien så att residualen, skillnaden mellan det uppmätta värdet och det justerade värdet, minimeras under uppfyllande av mass balans. En implementation i MATLAB och tester på syntetisk data visar att den dynamiska formuleringen av massbalans justerar de felaktiga mätvärdena så att massbalans uppfylls. Med det resultatet i åtanke, finns det fortfarande viktiga aspekter av implementationen som bör tas hänsyn till. Modellen använder de okända och cellspecifika parametrarna flotationshastighet och utbytet och dessa måste kunna bestämmas för att denna modell ska kunna användas. Ett förslag på modellering av flotationshastigheten föreslås i rapporten. Dessutom ges förslag på strategier att hitta utbytet. Kraven på noggrannhet och snabbhet diskuteras också. Möjliga nästa steg för projektet är att vidareutveckla en tidseffektiv implementation genom att använda syntetiska data. Därefter kan en implementation för naturligt data verifiera modellerna.
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