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Hellström, Kristina. "Density variations during solidification of lamellar graphite iron." Licentiate thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH, Material och tillverkning, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-37869.
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Hernando, Juan Carlos. "Morphological characterization of primary austenite in cast iron." Licentiate thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH, Material och tillverkning, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-35585.
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Automotive industry products portfolio includes a wide variety of complex‐shaped cast iron products, such as truck engine components, that need to withstand a constant trend of higher demands, especially urged by stricter environmental regulations on emissions. Combined with this continued demand on properties improvement, cast iron industry faces a process problem related to the lack of understanding of solidification and mechanisms behind defect formation. Casting products are highly affected by the product design and the manufacturing method itself, which governs the final microstructure and hence the final mechanical properties. Wall thickness of the moulding material strongly influences the solidification time, varying the microstructural coarseness, resulting in a component with different properties depending on the local shape of the casting. The main objective of this work is the characterization of the primary austenite microstructure and its coarsening process, which has been poorly documented in cast iron literature, to allow the prediction and control of these microstructural features present in the casting. The microstructural evolution of the primary austenite in hypoeutectic lamellar graphite iron (LGI) is studied under isothermal coarsening conditions. The dendritic microstructure suffered major morphological changes that included dendrite fragmentation, globularization, and coalescence. Empirical relations based on morphological parameters are introduced to predict the microstructural evolution of primary austenite. A novel technique for colour‐etching and semi‐automatic image analysis for the characterization of quenched dendritic microstructures in cast iron is presented. A new experimental technique for production of graphitic iron with varying nodularity is presented as a solution to control the production of compacted (CGI) and spheroidal graphite iron (SGI) under laboratory conditions. The nodularity evolution is controlled as a function of the holding time and the residual Mg, allowing the study of the primary solidification and primary microstructures of hypoeutectic CGI and SGI in future investigations.
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Freitas, De Abreu Marcio. "Experimental Study of Metallic Surfaces Exposed to Cavitation." Thesis, KTH, Materialvetenskap, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-231937.
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Cylinder liners in heavy-duty truck engines are subjected to intense vibrations and may sustain damage from the cavitation of bubbles in the coolant liquid, with some risks of leakage and engine breakdown. An ultrasonic oscillating probe was used to simulate the pitting rates and behavior of samples extracted from cylinder liners, which are made of grey cast iron, with differences in surface roughness, glycol and inhibitor content in coolant, coolant temperature and graphite flake class; bainitic microstructures were also tested. Measurements consisted of mass losses under set intervals during experiments lasting 2.5 or 4 hours. Affected surfaces were later evaluated with scanning electron microscopy and confocal microscopy. Results indicate higher cavitation damage with: lower concentrations of glycol and absence of corrosion/cavitation inhibitors in the coolant liquid, lower liquid temperatures between 76⁰C and 90⁰C, and presence of B-type graphite class in the microstructure. Results regarding surface roughness were inconclusive. A sequence of surface damage mechanisms has been proposed, with corresponding microscope observations, to explain the mass loss trends and the associated microstructural changes over time.
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Ram, Gokul, and Vishnu Harikrishnan. "INFLUENCE OF CARBON CONTENT AND COOLING CONDITIONS ON THE THERMAL CONDUCTIVITY AND TENSILE STRENGTH OF HIGH SILICON LAMELLAR GRAPHITE IRON." Thesis, Tekniska Högskolan, JTH, Material och tillverkning, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-51152.
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Much study has been carried out to determine the properties of Lamellar Graphite Iron (LGI) or grey iron and their relations to factors such as the cooling rate, the dendrite morphology, the pouring temperature, and so on. However, there hasn’t been much comprehensive study on the properties of LGI outside the generally used and accepted composition, with 1 to 3% Silicon. The scope of this study is to measure and evaluate the thermal conductivity and tensile strength of LGI, for a higher concentration of Si and different carbon contents. The concentration of Si aimed for was 4% but the concentration obtained after spectroscopy was between 4.1% to 4.15%. There are two hypereutectic, one near-eutectic and three hypoeutectic samples considered and these six chemical compositions were cast under different cooling conditions . The cooling time has been varied by providing different molds of 30mm, 55mm, and 80mm diameter cylinders respectively, for all the six sample compositions. The microstructure analysis carried out studies the segregation of Si, the graphite morphology, primary austenite morphology. These factors are then compared to the thermal and tensile behavior measured in this study. It can be observed that the thermal conductivity studied in the present work has a direct correlation for a higher Si content and tends to be greater than the thermal conductivity values observed from other studies with lower content Of Si. However, the conductivity shows an inverse relation with the cooling rate and is maximum for the samples with the lowest cooling rate. The tensile strength, on the other hand, seems to have a lower value than that observed in previous studies for LGI with 1 to 3% Si, but shows a direct correlation with the cooling rate. The mean area fraction of dendrites obtained and the mean interdendritic hydraulic diameter is also measured and their influence on the properties are also studied. The addition of more Si has greatly favored the thermal behavior positively but has also reduced the tensile strength.
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Sundaram, Dinesh. "The Effect of Solidification time and Cooling rate on the Ultimate tensile Strength of Grey Cast Iron." Thesis, KTH, Materialteknologi, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-238856.
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Tensile strength modelling is usually done to predict the mechanical properties of lamellargraphite iron considering microstructural features. This work attempts to create a simplifiedmodel incorporating cooling rate and solidification time without considering themicrostructural features. This model will save time and cost in industry with the presence of acommercially available software such as Magmasoft which simulates solidification time andcooling rate. A plate model was designed for this purpose as the test geometry to createvariation in solidification time and cooling rate. By altering fraction solid, thermalconductivity, specific heat capacity in Magmasoft, a good fit was created between simulatedcooling curve and experimental cooling curves. The experimental UTS data of samples fromthree moulds were investigated and a regression model was created using statistics toolMinitab. The effect of solidification time and alloying on the graphite length Lmax was studiedfor twelve samples from each mould. Quantification of the effect of cooling rate and alloyingon the pearlitic properties of grey iron like matrix microhardness, pearlite inter-lamellarspacing was also investigated in this work.The developed model has sixty three percent correlation and explains UTS well in terms ofsolidification time and cooling rate. Microhardness measurements show that there is an almostlinear relationship between the cooling rate and microhardness of the matrix structure.Microhardness data also provides an overview of the pearlite fineness/interlamellar spacing.Analysis of the outliers showed that the presence of free ferrite on a fully pearlitic structurereduces the UTS significantly. Comparison of the regression model obtained from this workwith previous work showed that, there is a reduction in the predicted strength with this model.The effort to identify the reason for this reduction was not successful and needs furtherinvestigation. Pearlite inter-lamellar spacing measurement was not accurate. The relationshipbetween pearlite interlamellar spacing and matrix microhardness needs to be investigated inthe future using a better technique for pearlite spacing measurement. This will be useful tounderstand the effect of cooling rate on pearlite spacing and consequently on the UTS of greycast iron.<br>Draghållfasthetsmodellering görs vanligtvis för att förutsäga de mekaniska egenskaperna av lamellärt grafitjärn. Detta arbete har försökt att skapa en förenklad modell som innehåller kylhastighet och stelningstid utan att överväga mikrostrukturella egenskaper. Modellen kommer att spara tid och kostnad i industrin tillsammans med kommersiellt tillgänglig mjukvara som Magmasoft som simulerar stelningstiden och kylningshastighet. En plattformig modell utformades för detta ändamål som testgeometrin för att skapa variation i stelningstid och kylningshastighet. Genom att ändra fraktion fast fas, termisk konduktivitet och specifik värmekapacitet i Magmasoft skapades en bra anpassning mellan simulerade och experimentella kylkurvor. Experimentella draghållfasthetsdata (UTS) för prover från tre gjutningar undersöktes och en regressionsmodell skapades med hjälp av statistikverktyg Minitab. Effekten av stelningstid och legeringshalt på grafitlängden Lmax studerades för tolv prover från varje form. Effekten av kylhastighet och legering på de perlitiska egenskaperna hos grått järn som matrismikrohårdhet och perlitlamellavstånd undersöktes också i detta arbete. Den utvecklade modellen har sextiotre procent korrelation och förklarar UTS väl med avseende på stelningstid och kylningshastighet. Mikrohårdhetsmätningar visar att det finns ett nästan linjärt förhållande mellan kylhastigheten och mikrohårdheten hos matrisstrukturen. Mikrohårdhetsdata ger också en översikt över perlitens finhet/interlamellära avstånd. Analys av outliers visade att närvaron av fri ferrit på en fullständigt perlitisk struktur minskar UTS betydligt. Jämförelse av regressionsmodellen erhållen från detta arbete med tidigare arbete visade det att det finns en minskning av den förutsagda styrkan med denna modell. Ansträngningen att identifiera orsaken till denna minskning var inte framgångsrik och behöver ytterligare undersökas. Perlit mellan lamellär avståndsmätning var inte korrekt. Förhållandet mellan perlitens interlamellära avstånd och matrismikrohet måste undersökas i framtiden med hjälp av en bättre teknik för perlit-avståndsmätning. Detta kommer att vara användbart att förstå effekten av kylhastighet på perlitavståndet och följaktligen på UTS av grå gjutjärn
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Augustins, Louis. "Dimensionnement à la fatigue thermomécanique de disques de frein automobiles en fonte à graphite lamellaire." Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066246/document.
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Cette thèse vise à développer une démarche de dimensionnement à la fatigue thermomécanique de disques de freins automobiles en fonte à graphite lamellaire. La première étape est la proposition d'une loi de comportement cyclique permettant de représenter les phénomènes non-linéaires ainsi que la forte dissymétrie de comportement entre traction et compression observés sur la fonte GL. Le modèle s'appuie sur l'introduction d'un tenseur d'endommagement d'ordre 2 induit par le chargement. A partir de l'analyse des mécanismes d'endommagement, on propose ensuite un critère de fatigue fondé sur la densité d'énergie dissipée par cycle, permettant de prédire l'amorçage de fissures dans les zones critiques. On s'intéresse enfin à l'étude de la formation d'un réseau de faïençage observé sur les pistes des disques de frein<br>This thesis aims at developing an approach for thermomechanical fatigue design of automotive brake discs made of flake graphite (grey) cast-iron. The first step of this work consists of modeling the nonlinear cyclic behavior and tension/compression strong dissymmetry of grey cast iron. The proposed model is based on the introduction of a second-order induced damage tensor. From the analysis of the damage mechanisms, a fatigue criterion based on the dissipated energy per cycle, allowing crack initiation in the critical areas to be defined, is proposed. Finally, the formation of crack networks on braking discs is studied
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Westphal, Mark Emil. "Fracture toughness of coral graphite cast iron." Thesis, Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/16892.
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Castillo-Bozzo, Ricardo N. "A fracture mechanics study of flake graphite cast iron." Thesis, Imperial College London, 1985. http://hdl.handle.net/10044/1/37651.
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Franklin, Steven E. "A study of graphite morphology control in cast iron." Thesis, Loughborough University, 1986. https://dspace.lboro.ac.uk/2134/32998.
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The objectives of the research project were to gain a deeper understanding of the factors influencing the graphite morphology in cast iron; particularly the role of different solute elements in relation to the industrial manufacture of compacted graphite iron. A number of melt treatment processes were assessed for their abilities to produce low nodularity compacted graphite microstructures over a range of casting section thicknesses. In this respect, the magnesium-titanium method was found to be superior to treatment using cerium Mischmetall and calcium additives; and very promising results were obtained with methods using zirconium as a major constituent of the treatment alloy. Scanning electron microscopy, secondary ion mass spectrometry and X-ray microanalysis were used to study the structural characteristics of different cast iron microstructures and the elemental distributions of important solutes between the phases. This information was used to clarify the role of the main solute elements in graphite morphology control and to assess current graphite growth theories.
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Tigane, Rafik. "Caractérisation des phénomènes de stiction d’un couple disque/garniture de friction." Thesis, Sorbonne université, 2021. https://tel.archives-ouvertes.fr/tel-03789653.
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Le phénomène de stiction se traduit à l’interface disque-patin de frein par l’adhésion du patin au disque lors d’un serrage suffisamment long du frein de parking. Les mécanismes à l’origine de ce phénomène sont, à ce jour, largement inexpliqués. Cependant, à partir d’observations effectuées sur des surfaces de couples disque-patin ayant subi une stiction, l’hypothèse selon laquelle les produits de corrosion du disque, en s’incrustant dans les pores du matériau de friction, seraient à l’origine de ce phénomène, a été privilégiée. Les travaux de cette thèse ont porté sur la compréhension du phénomène de stiction en s’articulant sur trois volets qui sont : (a) la caractérisation du comportement électrochimique de divers couples disque-patin à l’aide de mesures de suivi du potentiel de corrosion, de spectroscopie d’impédance électrochimique et de voltampérométrie, (b) l’étude mécanistique des phénomènes de corrosion à l’interface disque-patin et (c) l’étude de l’effet de la pression sur les phénomènes de corrosion du couple disque-patin. L’étude sans force de serrage nous a permis, d’une part, de mettre en évidence une réactivité exacerbée du disque en présence du patin et d’autre part d’établir un critère de sélection de couple disque-patin. Le suivi du déplacement du patin lors des mesures électrochimique sous presse a permis de mettre en évidence que les produits de corrosion, en s’accumulant à l’interface disque-patin, exerçaient une force sur le patin, confirmant l’hypothèse émise au cours de cette thèse pour expliquer le phénomène de stiction<br>The phenomenon of stiction occurs at the pad-brake disc interface by the adhesion of the pad to the disc when the parking brake is applied long enough. The mechanisms behind this phenomenon are, to date, largely unexplained. However, from observations made on surfaces of disc-pad pairs having undergone a stiction, the hypothesis according to which the corrosion products of the disc, by becoming encrusted in the pores of the friction material, would be at the origin of this phenomenon, was privileged. The work of this thesis focused on understanding the phenomenon of stiction by focusing on three components which are: (a) the characterization of the electrochemical behavior of various disc-pad couples using measurements to monitor the corrosion potential, electrochemical impedance spectroscopy and voltammetry, (b) the mechanistic study of corrosion phenomena at the disc-pad interface and (c) the study of the pressure effect on corrosion phenomena of the disc-pad couple. The study without a clamping force allowed us, to demonstrate an exacerbated reactivity of the disc in the presence of the pad and to establish a selection criterion for the disc-pad torque. Monitoring the movement of the pad during electrochemical measurements with a clamping force revealed that corrosion products, accumulating at the disc-pad interface, exerted a force on the pad, confirming the hypothesis put forward during this thesis to explain the phenomenon of stiction
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Bobyliov, Konstantin. "Casting voids influence on spheroid graphite cast iron high-cycle fatigue strength." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2008. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2008~D_20081128_120950-42235.
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The influence of casting voids on spheroid cast iron cracking threshold is investigated. The experimental results and their analytical and numerical analysis basing on linear fracture mechanics is presented.<br>Nagrinėjamas liejimo tuštumų poveikis stipriojo ketaus pleišėjimo slenksčiui. Pateikiami eksperimentiniai rezultatai ir jų analitinė bei skaitinė analizė, remiantis tiesine irimo mechanika.<br>Исследуется влияние литейных пустот на порог трещиностойкости чугуна с шаровидным графитом. Представлены результаты экспериментального исследования и их аналитический и численный анализ, опираясь на линейную механику разрушения.
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Velichko, Alexandra. "Quantitative 3D characterization of graphite morphologiesin cast iron using FIB microstructure tomography." Aachen Shaker, 2008. http://d-nb.info/992480035/04.
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Ghasemi, Rohollah. "Tribological and Mechanical Behaviour of Lamellar and Compacted Graphite Irons in Engine Applications." Licentiate thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH. Forskningsmiljö Material och tillverkning – Gjutning, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-25724.
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There has been much discussion about the beneficial uses of lamellar graphite iron in piston rings–cylinder liner systems, where a good combinations of both thermal and tribological properties are essential. The excellent tribological performance of lamellar iron under such sliding conditions is principally associated with lubrication behaviour of the graphite particles which are distributed as lamellas throughout the matrix. During sliding, graphite particles are extruded and smeared onto the counterfaces, act as solid lubricating agents and form a thin graphite film between the sliding surfaces. Although this process especially, during the running-in period significantly changes the sliding wear response of the components, the exact mechanism behind of this phenomenon has rarely been discussed in previous studies. It is tribologically beneficial to keep the graphite open, particularly in applications where the scuffing issues do matter. In this thesis, the main causes involved in closing the graphite lamellas are discussed, with a focus on matrix plastic deformation that occurs during sliding. In first step, the relationship between graphite lamellae orientation and plastic deformation was investigated. To do so, two piston rings, belonging to the same two-stroke marine engine operated for different periods of time, were selected and compared to the unworn sample. The worn piston rings displayed a substantial decrease in both frequency and area fraction of the graphite lamellas. Most of the lamellas were closed as a result of plastic deformation of matrix. This happening was caused mainly by the interaction between abrasive particles and metallic matrix. Additionally, it was found that graphite lamellas parallel or near-parallel to the sliding direction exhibited maximum closing tendency under sliding condition. In next step, to have a better understanding of the graphite film formation mechanism and matrix deformation role in closing the graphite lamellas, microindentation and microscratch testing were performed on typical lamellar iron. The qualitative results showed a similar mechanism involving in graphite contribution to lubricate the sliding surfaces. Moreover, microindentations made nearby the graphite lamellas demonstrated that the deformation of the matrix causes the formation of cracks in the centre of the graphite lamellas, compressing and then extruding the graphite from its natural position, irrespective of the lamellas′ size. Furthermore, it was found that subsurface graphite orientation had a large influence on the extrusion behaviour, in that, for graphite lamellas oriented towards the indenter, the effect was observed more pronounced. Furthermore, an improved fully ferritic solution strengthened compacted graphite iron was produced for future wear studies. The effects of different Si levels and section thicknesses on tensile properties and hardness were investigated as well. The influence of Si content and section thickness on mechanical properties was revealed by improving the materials strength and slightly enhancing the hardness through increasing Si content. Besides, Si addition up to 4.5 wt% significantly affected the strength and elongation to failure of cast samples.<br>Helios<br>FFI
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Ye, Jianchang. "Roles of graphite in the reduction of azo-aromatic compounds with elemental iron." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 137 p, 2006. http://proquest.umi.com/pqdweb?did=1172118261&sid=5&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Svidró, Péter. "Study of solidification and volume change in lamellar cast iron with respect to defect formation mechanisms." Licentiate thesis, KTH, Tillämpad processmetallurgi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-136985.
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Lamellar cast iron is a very important technical alloy and the most used material in the casting production, and especially in the automotive industry which is the major consumer. Beside the many great properties, it is inclined to form casting defects of which some can be prevented, and some may be repaired subsequently. Shrinkage porosity is a randomly returning problem, which is difficult to understand and to avoid. This defect is a volumetric deficiency which appear as cavities inside the casting in connection to the casting surface. Another frequent defect is the metal expansion penetration. This defect is a material surplus squeezed to the casting surface containing sand inclusion from the mold material. Shrinkage porosity is usually mentioned together with metal expansion penetration as the formation mechanism of both defects have common roots. It is also generally agreed, that these type of defects are related to the volumetric changes occurring during solidification. Additionally, the formation of these defects are in connection with the coherency of the primary austenite dendrites. The purpose of this work was to develop knowledge on factors affecting a volume-change related casting defect formation in order to minimize the presence of these defects in engine component production. This was done by extending the existing solidification investigation methods with novel solutions. Introduction of expansion force measurement in the determination of dendrite coherency combined with multi axial volume change measurement refine the interpretation of the solidification. Comparison of registered axial and radial linear deformation in cylindrical samples indicated an anisotropic volume change. Different methods for dendrite coherency determination have been compared. It was shown that the coherency develops over an interval. Dependent on the added inoculant the coherency is reached at different levels of fractions of a solidified primary phase. It is also shown, that inoculation has an effect on the nucleation and growth of the primary phase. Quantitative image analysis has been performed on the primary phase in special designed samples designed to provoke shrinkage porosity and metal expansion penetration. It was found, that the inter-dendritic space varies within a casting. This was explained by the coarsening of the primary dendrites which originates from differences in the local time of solidification.<br><p>QC 20131210</p>
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Yeliyur, Siddegowda Darshan. "Gray-cast iron classification based on graphite flakes using image morphology and neural networks." Thesis, California State University, Long Beach, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10017846.
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<p> Gray-cast iron is an iron carbon alloy which is regularly used in manufacturing processes. Carbon is distributed in the iron material in the form of graphite. The distribution of the graphite flakes in the alloy contributes greatly towards the chemical and physical properties of the metal alloy. Thus it is important to identify and classify the Gray-cast iron based on the morphological parameters of the graphite flakes. Gray-Cast iron is classified into five types in ISO-945 represented with the letters A through E. These five classes possess different structures or distributions of the graphite flakes. The current project presents an automated classification method using image processing and machine learning algorithms. The method presented here obtains the required parameters from the microstructure through image morphological operations. The image information is subsequently fed through a supervised machine learning algorithm which is trained using parameters such as area of the flakes, perimeter, minimum inter-particle distance and chord length from over twenty samples. The algorithm calculates the percentage of the type of the flakes present in the given image. The simulation is done in MATLAB and was tested for six images in each class. Class C and D were classified with 100 percent accuracy, Class A and B were classified with accuracy of 82 percent and Class E was identified with accuracy of 68 percent.</p>
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Boutorabi, S. M. A. "The austempering kinetics, microstructure and mechanical properties of spheroidal graphite unalloyed aluminium cast iron." Thesis, University of Birmingham, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.520795.
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The effect of austempering processing variables on the transformation kinetics, microstructure and mechanical properties of the Fe-C-AI family of spheroidal graphite cast irons, in which the silicon is below 0.2wt% has been investigated. These alloys are described as SO Al cast irons. In the preliminary experiments the spheroidisation and inoculation treatments for SO Al were developed and the microstructure and tensile properties in the as cast and normalised SO Al cast iron at 2.2 and 3.2% of Al examined. The results show that the sequence of spheroidisation of SO Al iron differs significantly from those observed in SG Si iron. Whilst the treatment to introduce some Mg into the melt is required in both irons to alter the growth habit of graphite from flake to spheroidal, the behaviour of the irons towards the subsequent inoculation with various inoculating alloys is quite different. A wide range of mechanical properties of SG Al irons can be obtained, similar to SG Si irons, in the as cast or heat treated conditions. The effects of austenitizing temperatures of 850, 900 and 950°C, austempering temperatures of 300 to 450°C and austempering times of 5 to 300 minutes on impact and tensile properties have been investigated. X-ray diffraction has been used to determine the volume fraction, lattice parameter and carbon content of retained austenite and bainitic ferrite produced under different austempering conditions. Optical and scanning electron microscopy were used to analyse the microstructure. It has been shown that the basic mechanisms for the isothermal transformation of austenite to bainite are essentially similar to those of austempered SO silicon cast irons for both lower and upper bainite. This can be attributed to the strong graphitising effect of aluminium which delays the formation of transformation carbides. However, the higher carbon contents of retained austenite in SG Al iron show the stronger carbide inhibiting characteristics of aluminium compared with those of silicon. The first stage starts with the nucleation of bainitic ferrite from the grain boundaries and adjacent to the graphite nodules. The second stage in upper bainite fonnation is the growth of ferrite, during which carbon diffusion occurs ahead of the ferrite-austenite interface thus enriching the surrounding austenite. This is followed in the third stage by carbide precipitation in the high carbon retained austenite. In lower bainite fonnation the nucleating ferrite is supersaturated with carbon, and carbide precipitation occurs inside ferrite plates. The results show that the rate of fIrst stage transfonnation is higher in SO Al than in the corresponding SO Si iron, and the high carbon retained austenite has a longer life time with a high carbon content. Increasing the austempering temperature was shown to increase structural coarseness and retained austenite content, leading to reduced strength and hardness and improved impact properties and ductility. Retained austenite produced in austempered SO Al iron showed more stability at a high austempering temperature of 450°C, compared to SO Si iron. This was attributed to the graphitising potential of aluminium which suppresses the formation of carbide at that temperature. Austenitizing temperature was found to control the carbon content of both the matrix and of the retained austenite. Increasing the austenitizing temperature was shown to increase the matrix carbon content and to slow the bainitic reaction. Microstructures obtained at higher austenitizing temperature revealed two types of retained austenite: one with a film morphology and the other in a blocky form surrounded by ferrite growing in different directions. The length of bainitic ferrite appears to increase with austenitizing temperature. Austenitizing temperature had a greater effect on hardness in the lower bainitic region and on impact values in the upper bainitic region. The results obtained show that the controlling austempering variables for an SO Al iron of a given starting composition and microstructure are closely similar to those of SO Si iron. The transformation mechanisms are also similar, but the transformation kinetics differ and, to a small extent, microstructural differences give rise to differences in properties between the two types of irons.
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Velichko, Alexandra [Verfasser]. "Quantitative 3D Characterization of Graphite Morphologies in Cast Iron using FIB Microstructure Tomography / Alexandra Velichko." Aachen : Shaker, 2009. http://d-nb.info/1161310541/34.
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König, Mathias. "Microstructure Formation During Solidification and Solid State Transformation in Compacted Graphite Iron." Doctoral thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH. Forskningsmiljö Material och tillverkning – Gjutning, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-15694.
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Compacted graphite iron (CGI) is rapidly becoming an attractive alternative material for engine components in the automotive industry, replacing lamellar graphite iron (LGI) in applications where high mechanical strength is desired. However, the gain in mechanical strength comes with a cost; thermal conductivity, process control and machining are three areas that are more challenging for CGI. This generates a need for research regarding various aspects concerning CGI. In this thesis the microstructure formation during solidification and solid state transformation will be the focus of interest. The phase transformations relevant for microstructure formation of importance to properties in CGI were studied. Experiments were performed in an industrial foundry giving this research direct relevance to regular production of CGI castings. Solidification of the grey (graphite/austenite) eutectic will be discussed, focusing on some relevant aspects influencing the graphite morphology of CGI. The formation of graphite nodules has been investigated by studying colour-etched microstructures. In a material containing mainly CGI cells it was found that nodules form either early during solidification as a consequence of high undercooling or late in the solidification sequence due to a combination of high undercooling and segregation of nodularising elements. Solidification of the white (cementite/austenite) eutectic was studied using chill wedges and the influence of some alloying elements on the amount of carbides was examined. To further enhance the understanding of carbide formation in CGI a commercial casting simulation software was used to correlate real castings to simulations. It was found that the alloying elements investigated influence the carbide formation in a similar way as in other graphitic cast irons and that high nodularity CGI is more prone to chill formation than low nodularity CGI. The solid state transformation was studied and a deterministic model was developed. The model divides a eutectic cell into layers, in order to take into account segregation of alloying elements, which was observed to be influential for the ferrite growth. Moreover, the effect of alloying elements on mechanical properties (tensile properties and hardness) was evaluated. Properties were correlated to microstructural features originating from both solidification and solid state transformations. The trends found generally confirmed previous results regarding properties in graphitic cast irons.
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Sjögren, Torsten. "Influences of the Graphite Phase on Elastic and Plastic Deformation Behaviour of Cast Irons." Doctoral thesis, Linköpings universitet, Konstruktionsmaterial, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-8776.
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The amount and morphology of the graphite phase largely controls the resulting properties of cast iron. For instance, in flake graphite cast irons the mechanical properties are low while the thermal conductivity is high. This is in contrast with spheroidal graphite cast irons where the mechanical properties are high and the thermal conductivity is low. These differences are due to the different graphite morphologies and must be accounted for in the design work and material selection of cast iron components. In this work the influence of the graphite phase on the elastic and plastic deformation behaviour of cast irons has been studied. The material grades studied originate from castings for marine diesel engine piston rings with different chemical analyses. Two groups of pearlitic cast iron materials were studied; one with differences in graphite morphology and one with grey irons that differed in graphite content. For these different material grades the mechanical properties were correlated to microstructural parameters. In addition to standard uniaxial tensile tests, acoustic emission measurements were used for the study of deformation. When studying the modulus of elasticity of the cast iron it was found that the modulus of elasticity of the inherent graphite phase depends on the roundness of the graphite particles and is due to the strong anisotropy of the graphite phase. A linear correlation between nodularity and the modulus of elasticity of the graphite phase was derived. This correlation made it possible to account for the anisotropy of the graphite phase in the model used. By applying the linear function when modelling the effective modulus of elasticity, a high accuracy between experimental and theoretical values was achieved. Another factor affecting the elastic response when subjecting a cast iron component to tensile load was found to be the plastic deformation that actually occurs at very low strains for all of the studied cast iron grades. It was observed that the plastic deformation in the low strain elastic region, quantified by using acoustic emission measurements, increased linearly with decreasing modulus of elasticity. These measurements showed that the amount of plastic deformation in the elastic region was largely controlled by the graphite morphology. It was concluded that as the roundness of the graphite particles increases, the plastic deformation activity in the elastic region decreases. The plastic deformation activity continued linearly into the pronounced plastic region of the tensile tests. A decrease in roundness or increase in graphite fraction resulted in an increase of the amount of plastic deformation and the strain hardening exponent. A dependence between strength coefficient and graphite fraction was observed. Models for the flow curves for pearlitic cast irons were developed and shown to accurately reproduce the observed experimental curves. The surveys performed and conclusions from this thesis will be helpful in the design of new cast iron materials.
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Elmabrouk, Omar Mustafa. "An Investigation Of Compacted Graphite Cast Iron Production By Means Of Thermal Analysis Technique And Other Process Control Windows." Phd thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/3/12608096/index.pdf.
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ABSTRACT
AN INVESTIGATION OF COMPACTED GRAPHITE IRON PRODUCTION BY MEANS OF THERMAL ANALYSIS TECHNIQUE AND OTHER PROCESS CONTROL WINDOWS
El-mabrouk, Omar
PhD, Metallurgical and Material Engineering Department
Supervisor: Prof. Dr. Ali Kalkanli
January 2007, 123 pages
Compacted graphite irons have been proved valuable in many applications such as exhaust manifolds, hydraulic valves, and diesel engine blocks, the process of producing compacted graphite irons is not a straight forward process because of its narrow processing windows and its high sensitivity to the section thickness, treatment reaction time, pouring temperatures and charge composition.
In this thesis, compacted graphite was produced with minimum variations through all section thickness and the effect of Mg/S ratio, section thickness, and treatment agents on the graphite morphology, electrical resistivity property and fracture strength at high temperatures was investigated.
The range of Mg/S ratio and the section thickness was from 2/3 to 7/1 and 5 mm to 40 mm respectively. FeSiMg and FeSiMg cermish metal were used as a treatment agent.
Optical metallographic method was implemented to investigate the graphite
morphology change. For being a distinguishable characteristic for compacted graphite iron over ductile iron, thermal conductivity changes at high temperatures ranging from room temperature to 500 0C was examined by a suitable electrical setup in the manner of electrical conductivity changes by measuring the electrical resistance.
On the other hand, due to the higher values of mechanical properties of compacted graphite iron over those of gray iron, tensile strength was also examined by means of tensile test.
The relation between the compacted graphite shape and the alloy properties such as fracture strength and thermal conductivity was investigated. The most important controlling parameters to produce compacted graphite are Mg/S ratio and oxygen activity. The relation between these parameters with both fracture strength and thermal conductivity was established by means of multiple regression analysis technique.
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Cox, G. J. "The effect of composition and heat-treatment on the mechanical properties and micro structure of spheroidal-graphite cast iron." Thesis, Aston University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.484343.
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Ghasemi, Rohollah. "The influence of microstructure on mechanical and tribological properties of lamellar and compacted irons in engine applications." Doctoral thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH, Material och tillverkning, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-32052.
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Lamellar graphite iron (LGI) is commonly used in diesel engine applications such as piston rings–cylinder liner where an excellent combination of physical and tribological properties is essential to avoid scuffing and bore polishing issues. The excellent tribological behaviour of LGI alloys is related to the graphite lamellas, which act as solid lubricant agents by feeding onto the tribosurfaces under sliding conditions. However, increasingly tighter emissions and fuel economy legislations and the higher demands on enhanced power and durability have encouraged both engine designers and manufacturers to introduce pearlitic compacted graphite irons (CGI) as an alternative material replacing LGI, although the poor machinability of pearlitic CGI alloys compared to the LGI remains a challenge. The focus of this study is placed on investigating how the microstructure of LGI and CGI alloys affects their mechanical and tribological properties. This was initially undertaken by investigating representative, worn lamellar cast iron piston rings taken from a two-stroke large-bore heavy-duty diesel engine. As known that it is tribologically essential to keep the graphite open under sliding conditions, in particular under starved lubrication regimes or unlubricated conditions to avoid scuffing issues; however, this study revealed the closure of a majority of graphite lamellas; profoundly for those lamellas that were parallel to sliding direction; due to the severe matrix deformation caused by abrasion. Both microindentation and microscratch testing, which were used to crudely simulate the abrasion under starved lubricated condition in combustion chamber, suggested a novel mechanism of activating the graphite lamellas to serve as lubricating agents in which the matrix deformation adjacent to the graphite initially resulted in fracturing and then extrusion of the graphite lamellas. Additionally, in order to investigate the relation between matrix constituents, mechanical properties and machinability of cast iron materials, solution-strengthened CGI alloys were produced with different levels of silicon and section thicknesses. The results showed significant improvements in mechanical properties and machinability while deteriorating the ductility. Moreover, multiple regression analysis, based on chemical composition and microstructural characteristics was used to model the local mechanical properties of high Si ferritic CGI alloys, followed by implementing the derived models into a casting process simulation which enables the local mechanical properties of castings with complex geometries. Very good agreement was observed between the measured and predicted microstructure and mechanical properties.
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Dong, Ming-Jing. "Effet de l'endommagement sur la ténacité de la fonte à graphite sphéroïdal." Châtenay-Malabry, Ecole centrale de Paris, 1995. http://www.theses.fr/1995ECAP0392.
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Cette étude porte sur l'influence de l'endommagement sur la loi de comportement et sur la ténacité de la fonte a graphite sphéroïdal. La microstructure des fontes GGG 40, GS 52 5%, GS 52 25%, a été caractérisée par analyse à la microsonde, observation au MEB, et analyse d'images. L’endommagement est décrit d'une part à l'échelle macroscopique par les paramètres D, le coefficient de dilatance et l'évolution du coefficient de poisson plastique, et d'autre part a l'échelle microscopique par observation au MEB des différents stades de la décohésion de l'interface graphite/matrice. Nous trouvons que la décohésion apparait des les premiers stades de la déformation plastique macroscopique. D augmente de 30% quand la déformation plastique varie de 0 à 2%, puis l'endommagement se stabilise jusqu'a la rupture finale. Les différents types de graphite donnent les mécanismes d’endommagement différent. La fonte ne peut donc pas être considérée comme un matériau dense. La contrainte critique à l'interface pour la décohésion est de 82 MPA. La modélisation numérique de la loi de comportement montre que en tenant compte des effets du palier de plasticité, de l'empilement des nodules, des contraintes résiduelles, les nodules de graphite peuvent être remplacés par des cavités en accord avec les observations des mécanismes d'endommagement. La taille de la zone endommagée en tête de fissure a été déterminée par observation sur une éprouvette CT 25 de fonte GGG 40 et par des calculs analytique et numérique rendant compte de l'effet de la contrainte hydrostatique. Les résultats expérimentaux et ceux des modèles montrent bien que l'endommagement joue un rôle important dans le cas des éprouvettes CT 25. L’endommagement en tête de fissure modifie la valeur conventionnelle de kC, et entraine une augmentation de la ténacité par comparaison avec celle de la matrice massive. En présence de cavités nous montrons que, l'état de contrainte ne joue pas le même rôle sur la taille de la zone plastique que dans les matériaux denses.
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Souza, José Vitor Cândido de. "Desenvolvimento de pastilhas cerâmicas à bases de Si3N4 para aplicações tribológicas /." Guaratinguetá : [s.n.], 2005. http://hdl.handle.net/11449/105366.
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Resumo: Nesse trabalho foram desenvolvidas três composições à base de Si3N4 com quantidades e tipos de aditivos diferentes, com objetivos de desenvolver cerâmicas densas de altas resistências, para posteriores testes como ferramentas de corte na usinagem de torneamento do ferro fundido cinzento, ferro fundido vermicular e a liga Ti-6Al-4V. As composições utilizaram aditivos Y2O3/Al2O3 (10%) e AlN/Y2O3 (15 e 20%), e foram sinterizadas pelo processo de sinterização normal. Em seguida foram caracterizadas quanto as propriedades físicas e mecânicas, apresentando bons resultados. Posteriormente a composição de melhores propriedades (SNYA20), foi transformada em inserto para usinagem de corte de acordo com a norma ISO 1832. Os testes de torneamento foram realizados no ferro fundido cinzento com variações de parâmentros, onde para Vc=300m/min, f=0,32mm/rot e ap=1,00mm, alcançou um comprimento de corte de 6533m, superior aos encontrados em literatura, com diminuição dos desgastes, para maiores Vc e ap. O torneamento da liga Ti-6Al-4V em alta velocidade (Vc=180m/min, f=0,10mm/rot e ap=0,50mm), alcançou comprimento de corte de Lc=466m, para um desgaste VBmax=2,20mm. No torneamento do ferro fundido vermicular, com variações de parâmetros, alcançou resultados superiores aos encontrados na literatura com ferramentas cerâmicas comercial, utilizando Vc=200mm/min, f=0,20mm/rot e ap= 0,50mm, obteve-se comprimento de corte Lc=1658m. Os resultados de usinagem obtidos nesse trabalho estão relacionados com as propriedades e fases obtidas. Entretanto alem dos resultados obtidos essas ferramentas apresentam custo em torno de 50% das comerciais e redução de 17- 20% de custo no processo, devido ao uso de fluido refrigerante e proteção ao meio ambiente.<br>Abstract: In this work three compositions to base Si3N4 with amounts and types of different additives had been developed, with objective to develop dense ceramics of high strength to possible test as cutting tools in turning of gray cast iron, compacted graphite iron and titanium alloy (Ti-6Al-4V). The compositions had used additives Y2O3/Al2O3 (10%) and AlN/Y2O3 (15 and 20%), and were sinterized by process normal sintering. After sintering the physical and mechanical properties had been characterized, showing interesting results. Posterior the composition the best properties (SNYA20), was transformed into cutting tools to machining in the stand norm ISO 1832. The turning tests had been carried in gray cast iron with different parameters, where to Vc=300m/min, f=0,32mm/rev and ap=1,00mm, obtained a cut length of 6533m, achieving value superior at found in literature, with important reduction to larger cutting speed and cut depth. The turning of the Ti-6Al-4V alloy in high cutting speed (Vc=180m/min, f=0,10mm/rev and ap=0,50mm), obtained cutting length of Lc=466m, to VBmax=2,20mm. In turning compacted graphite iron, with different parameters, obtained value superior at found in literature, when utilize cutting tools ceramics of commercial materials, using for this Vc=200mm/min, f=0,20mm/rev and ap = 0,50mm. These condition obtained cut length of Lc=1658m. The results achieved in this work have been associated with the important physical and mechanical proprieties and phase of cutting tools. However the results obtained with these cutting tools present lower cost (50%) when compared with commercial cutting tools of similar material e reduction of cost in around 17-20%, because the do not use coolant, beside of protection at environment.<br>Orientador: Sérgio João Crnkovic<br>Coorientador: Olivério Moreira de Macedo Silva<br>Doutor
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Kiattisaksri, Chatcharit. "Time-Resolved and In-Situ Study on Evolution of Spheroidal Graphite Nodules and Volume Change During Solidification in Ductile Cast Iron." Kyoto University, 2019. http://hdl.handle.net/2433/244548.
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Bourdie, Jacques. "Sphéroïdisation du graphite - Cas de la fonte centrifugée." Thesis, Toulouse, INPT, 2017. http://www.theses.fr/2017INPT0117/document.
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Les fontes de fer sont des matériaux largement utilisés dans de nombreux domaines allant de l’industrie automobile au secteur de l’énergie en passant par la fabrication des tuyaux d’adduction d’eau. Du fait de la teneur en carbone élevée de ces alliages, du graphite et/ou des carbures de fer précipitent pendant la solidification. Les propriétés finales des pièces dépendent alors de la nature de la matrice, de la présence ou non de carbures et surtout de la forme du graphite. Celui-ci peut cristalliser sous la forme de lamelles, de sphères ou de particules de formes intermédiaires. Les éléments présents à l’état de traces dans le bain de fonte liquide influencent de manière considérable la croissance du graphite et conditionnent sa forme finale. Leur moyen d’action ainsi que le mécanisme de croissance du graphite sphéroïdal sont encore un sujet de débat et cette thèse a pour objectif de contribuer à la compréhension des phénomènes mis en jeu. Les échantillons utilisés ont été élaborés selon le procédé de coulée par centrifugation, son influence sur les mécanismes étudiés est d’ailleurs au cœur de ce projet. Les différents essais et analyses réalisés prouvent que la structure des nodules observés dans les échantillons centrifugés est la même que dans le cas des pièces moulées en sable. De plus, les éléments traces montrent une action similaire lors de la solidification et pendant la croissance en phase solide durant le traitement thermique destiné à éliminer les carbures. Ces résultats suggèrent que le mécanisme de croissance du graphite sphéroïdal est le même lors de la croissance à partir du liquide ou en phase solide par décomposition des carbures. Une proposition est d’ailleurs faite pour expliquer le développement des nodules par une germination continue du graphite sur les plans de base conjuguée à une croissance selon les directions prismatiques. Un modèle mathématique associé à ce mécanisme est présenté et son application au procédé de centrifugation donne des résultats en accord avec les observations expérimentales<br>Cast irons are widely used in the foundry industries for applications mainly in the automotive, energy and pipes industries. Because of the high carbon content, graphite and/or iron carbides appear during solidification. The properties of the casting depend on the nature of the matrix, the presence or not of carbides and the shape of the graphite. It can crystallise under the form of lamellae, spheroids or particles with an intermediate shape. Trace elements present in the melt strongly influence graphite growth and shape. Their action and the growth mechanism of the spheroidal graphite are still under debate and the aim of this project is to contribute to the understanding of these phenomena. The samples have been cooled by the centrifugal casting process whose influence on the studied mechanisms is the focus of this project. The different analyses that have been carried out show that the structure of the nodules is the same in centrifugated and sand mold castings. Moreover, the trace elements exhibit a similar action during solidification and solid state growth during heat-treatment for carbide dissolution. These results suggest that the growth mechanism of spheroidal graphite is the same during growth from the liquid and by solid state decomposition of carbides. A schematic is proposed to explain the growth of the nodules by a continuous nucleation on the basal surface of the graphite coupled to a growth along the prismatic directions. A mathematical model associated to this mechanism is presented and its application to the centrifugal casting process gives results in good agreement with experimental observations
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Molina, Griggs Alejandro José. "Laser Metal Powder Deposition of Austenitic Stainless Steel on Spheroidal Graphite Cast Iron : A corrosion resistant coating for the Food & Beverage Industry." Thesis, Högskolan Väst, Avdelningen för svetsteknologi (SV), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-13016.
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Spheroidal graphite cast iron is a material widely used in the industry for the manufacturing of all kind of covers and protective casings thanks to its good combination of mechanical properties, processability and cost. When cast iron components are put into service in corrosive environments the most common approach to protect the components is painting them. The protective painting has been found to flake off with time when aggressive washing procedures, such as the ones used in the Food & Beverage industry, are applied several times. In this project, the coating of cast iron with a corrosion resistant AISI 316L stainless steel by Laser Metal Powder Deposition has been studied as an alternative protection against corrosion. Several samples with different combinations of substrate preparation, number of layers and surface conditions were produced and analysed by optical microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, wash down tests and salt spray chamber corrosion tests. Main results show that the diffusion of carbon from the carbon-rich cast iron to the stainless steel coating, which would have a negative effect on the corrosion resistant properties, was significantly low as a result of the low penetration and dilution achieved during the laser metal powder deposition process. The deposited stainless steel coatings successfully protected the substrate during the corrosion tests and the integrity of the coatings is not expected to fail during the washing producers applied in the industry.
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Filipek, Szymon. "Predikce mechanických vlastností odlitků z litiny s lupínkovým grafitem pomocí numerické simulace." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-400494.
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The aim of this thesis was to assess the degree of conformity between the mechanical properties evaluated by numerical simulation in software MAGMA5 and the measured values of hardness and ultimate tensile strength of lamellar graphite iron castings. The theoretical part of this thesis deals with the classification of cast iron, structural components of lamellar graphite iron, and the factors defining the resulting mechanical properties of the material. The practical part presents an attempt to find empirical dependencies between input parameters and results evaluated by simulation software. At the end, an analysis of the correlation between reality and simulation software is performed.
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Armstrong, Christopher. "Inoculant measurement with thermal analysis." Thesis, KTH, Materialvetenskap, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-279066.
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Over time the level of inoculant will decrease due to fading and this needs to be compensated bymore additions of inoculant. When casting CGI400 at Scania a one-step method is used, and the inoculant additions are based on the last ladle from the previous oven. Longer stops in production will result in the previous oven not being representable and more inoculant should be added. A method to establish the inoculation level of the base iron in the oven would make it easier to control the process. This study was about inoculation measurements with the help of thermo- analysis of the melt in the oven to get a better understanding how it fluctuates between ovens and changes over time. The study is also about how to implement this tool into production in a foundry. With the help of thermo- analytic measurements, the inoculation level of the melt was established, and the method was also used to see how the level of inoculant changed over. To establish the inoculation additions needed, the saturation point of inoculant was investigated. The results from the study shows that the starting level of inoculant is too low in the melt it also shows that the inoculation level fluctuates over time. The conclusions that can be drawn from this study is that thermos analysis can be used in production to establish the inoculation level, but moremeasurements needs to be conducted to determine its accuracy.<br>Över tid så minskar ympnivån i en smälta på grund av fading och detta måste kompenseras med mertillsatser av ymp. Vid gjutning av CGI400 på Scania används en en-stegs metod där man baserar ymptillsatsen i skänken på vad ympnivån var i sista skänken från den tidigare ugnen. Vid längre produktionsstopp kommer inte ympnivån från ugnen innan vara representativ utan mer ymp måste tillsättas. En metod för att bestämma ympnivån av basjärnet i ugnen skulle göra det lättare att styra processen. Denna studie handlar om ympmätning med hjälp av termisk analys i bas smälta för att få en bättre förståelse för hur den fluktuerar mellan ugnar och ändras över tid. Studien handlar också om hur man ska kunna applicera denna mätmetod i produktionen på ett gjuteri. Med hjälp av termo analytiska mätningar skulle grundnivån av ymp i smältan bestämmas och även för att se hur nivån ändrades över tiden. För att bestämma tillsatsen av ymp som borde tillföras undersöktes mättnadspunkten av ymp och hur den kunde tillsättas i skänk. Resultaten från studien visar att grundnivån av ymp är för låg och resultaten visar också att nivån av ymp fluktuerar både upp och ner ökar tid vilket inte var vad man hade förväntat sig och även det finns flera faktorer som kan påverka nivån. Slutsatsen som kan dras är att termisk analys kan användas i produktion för att bestämma ympnivån, men mer mätningar behövs för att bestämmadess noggrannhet.
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Souza, José Vitor Cândido de [UNESP]. "Desenvolvimento de pastilhas cerâmicas à bases de Si3N4 para aplicações tribológicas." Universidade Estadual Paulista (UNESP), 2005. http://hdl.handle.net/11449/105366.
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souza_jvc_dr_guara.pdf: 3439864 bytes, checksum: 8f665815b08c108458b7f10749c5f6bb (MD5)<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)<br>Universidade Estadual Paulista (UNESP)<br>Nesse trabalho foram desenvolvidas três composições à base de Si3N4 com quantidades e tipos de aditivos diferentes, com objetivos de desenvolver cerâmicas densas de altas resistências, para posteriores testes como ferramentas de corte na usinagem de torneamento do ferro fundido cinzento, ferro fundido vermicular e a liga Ti-6Al-4V. As composições utilizaram aditivos Y2O3/Al2O3 (10%) e AlN/Y2O3 (15 e 20%), e foram sinterizadas pelo processo de sinterização normal. Em seguida foram caracterizadas quanto as propriedades físicas e mecânicas, apresentando bons resultados. Posteriormente a composição de melhores propriedades (SNYA20), foi transformada em inserto para usinagem de corte de acordo com a norma ISO 1832. Os testes de torneamento foram realizados no ferro fundido cinzento com variações de parâmentros, onde para Vc=300m/min, f=0,32mm/rot e ap=1,00mm, alcançou um comprimento de corte de 6533m, superior aos encontrados em literatura, com diminuição dos desgastes, para maiores Vc e ap. O torneamento da liga Ti-6Al-4V em alta velocidade (Vc=180m/min, f=0,10mm/rot e ap=0,50mm), alcançou comprimento de corte de Lc=466m, para um desgaste VBmax=2,20mm. No torneamento do ferro fundido vermicular, com variações de parâmetros, alcançou resultados superiores aos encontrados na literatura com ferramentas cerâmicas comercial, utilizando Vc=200mm/min, f=0,20mm/rot e ap= 0,50mm, obteve-se comprimento de corte Lc=1658m. Os resultados de usinagem obtidos nesse trabalho estão relacionados com as propriedades e fases obtidas. Entretanto alem dos resultados obtidos essas ferramentas apresentam custo em torno de 50% das comerciais e redução de 17- 20% de custo no processo, devido ao uso de fluido refrigerante e proteção ao meio ambiente.<br>In this work three compositions to base Si3N4 with amounts and types of different additives had been developed, with objective to develop dense ceramics of high strength to possible test as cutting tools in turning of gray cast iron, compacted graphite iron and titanium alloy (Ti-6Al-4V). The compositions had used additives Y2O3/Al2O3 (10%) and AlN/Y2O3 (15 and 20%), and were sinterized by process normal sintering. After sintering the physical and mechanical properties had been characterized, showing interesting results. Posterior the composition the best properties (SNYA20), was transformed into cutting tools to machining in the stand norm ISO 1832. The turning tests had been carried in gray cast iron with different parameters, where to Vc=300m/min, f=0,32mm/rev and ap=1,00mm, obtained a cut length of 6533m, achieving value superior at found in literature, with important reduction to larger cutting speed and cut depth. The turning of the Ti-6Al-4V alloy in high cutting speed (Vc=180m/min, f=0,10mm/rev and ap=0,50mm), obtained cutting length of Lc=466m, to VBmax=2,20mm. In turning compacted graphite iron, with different parameters, obtained value superior at found in literature, when utilize cutting tools ceramics of commercial materials, using for this Vc=200mm/min, f=0,20mm/rev and ap = 0,50mm. These condition obtained cut length of Lc=1658m. The results achieved in this work have been associated with the important physical and mechanical proprieties and phase of cutting tools. However the results obtained with these cutting tools present lower cost (50%) when compared with commercial cutting tools of similar material e reduction of cost in around 17-20%, because the do not use coolant, beside of protection at environment.
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Wang, Shuyan. "Formation des microstructures dans la fonte à graphite spheroïdal aux premiers instants de la solidification." Thesis, Université de Lorraine, 2012. http://www.theses.fr/2012LORR0338/document.
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Les conditions thermiques et le traitement du métal liquide pour la coulée centrifuge des tuyaux de canalisation permettent d'obtenir une solidification sous forme de graphite sphéroïdal sur l'ensemble de l'épaisseur. Il est parfois observé en peau des zones solidifiant selon le mode blanc qui peuvent induire des différences de réponses métallurgiques problématiques. La caractérisation de tuyaux de différents diamètres montre qu'une compétition entre la croissance de l'eutectique métastable et la germination et croissance de l'eutectique stable existe dès le tout début de la solidification. Pour préciser les conditions thermiques de cette compétition un dispositif de chute de goute sur substrat a été utilisé pour lequel la solidification rapide et dirigée se déroule avec mesure de l?évolution de la température aux premiers moments de la solidification (t<200 ms). La caractérisation des microstructures à l'état brut de coulée et après traitement thermique a montré que ce dispositif permettait de reproduire les conditions thermiques de la peau des tuyaux et de figer la structure précurseur de celle obtenue par coulée centrifuge. Un modèle physique décrivant les premiers instants de la solidification sous très fort gradient thermique d'une fonte inoculée et traitée au Mg est présenté, prenant en compte la cinétique de germination et croissance des nodules de graphite en compétition avec la solidification de l'eutectique métastable. La comparaison entre les résultats du modèle et les caractérisations microstructurales permet de préciser les scénarios de formation des microstructures en découplant l'influence du gradient thermique et de la vitesse de solidification<br>The thermal conditions and the treatment of the liquid metal for centrifugal casting of pipes lead to the solidification of the melt in the form of spheroidal graphite (SG) iron throughout the thickness. However it is sometimes observed zones that are solidified within the white mode (eutectic austenite / cementite) mainly in the skin of the product. These areas lead to differences which could be problematic. Further characterization of the microstructure of pipes shows that competition between the nucleation and growth of stable and metastable eutectic growth exists from the beginning of solidification. To clarify the thermal conditions of this competition an experimental device has been used. Liquid metal droplet fall on a cold substrate. Rapid directionnal solidification occurs and the temperature evolution of the lower surface of the droplet is recorded during the very first moment of solidification (< 200 ms). Characterization of droplet microstructures obtained in as-cast state and after heat treatment showed that the device is able to froze the solidified microstructure in an earlier stage of formation than in the as cast pipe. A physical model describing the first instants of the solidification under very high thermal gradient of a cast iron which is inoculated and treated with Mg is presented, taking into account the kinetics of nucleation and growth of graphite nodules in competition with the solidification of the metastable eutectic. The comparison between the calcluated results and microstructural characterizations allows to specify microstructures devlopment scenarios by decoupling the influence of the thermal gradient and solidification rate
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Ogata, Paulo Henrique. "Compósitos ferro-grafita para componentes de motores com propriedades tribológicas melhoradas." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/3/3133/tde-16112015-155422/.
Full textAbstract:
A constante busca por motores com maior eficiência energética, requer a introdução de novos materiais ou inovações nas rotas de fabricação dos materiais existentes. O presente trabalho busca, a partir de rotas de tratamento térmico, soluções para minimizar o desgaste originado no contato entre corpos metálicos em componentes submetidos a altas pressões de contato em regime lubrificado. A modificação microestrutural a partir de tratamentos térmicos originou matriz martensítica relativamente dura com uma dispersão refinada de nódulos esféricos de grafita, que atuariam como lubrificantes sólidos. O estudo baseou-se em dois ferros fundidos (cinzento e branco) submetidos a tratamentos de austenitização seguidos de tempera em óleo e revenimento em diferentes tempos. Ensaios de dilatometria foram efetuados nos dois materiais para estudar a cinética de grafitização secundaria sob diferentes condições de tratamento térmico. As propriedades mecânicas foram avaliadas por medidas de dureza Vickers das amostras tratadas termicamente. Amostras de ferro fundido cinzento e de branco modificado por tratamentos térmicos foram ensaiadas em teste de desgaste por deslizamento, com intuito de avaliar a influência de modificações na superfície no coeficiente de atrito.<br>The constant search for engines with higher energy efficiency requires the development of new materials or manufacturing innovations on the routes of existing materials. In the present work, heat treatment routs were investigated to minimize wear originated at the contact between metallic bodies into components subjected to high contact pressures in lubricated regime. Microstructural modification from heat treatments yielded relatively hard martensitic matrix with a fine dispersion of spherical graphite nodules, which act as solid lubricants. The study was based on two cast iron (gray and white) undergoing treatments of soaking (austenitizing) followed by quenching in oil and tempering at different times. Dilatometry tests were performed on both materials to study the kinetics of secondary graphitization under different heat treatment conditions. Mechanical properties were evaluated from Vickers hardness of the thermally treated samples. Samples of gray cast iron and white modified by heat treatments were tested in sliding wear test, in order to assess the influence of changes in the surface friction coefficient.
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Berglund, Anders. "Characterization of factors interacting in CGI machining : machinability - material microstructure - material physical properties." Licentiate thesis, KTH, Production Engineering, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-9258.
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<p>The Swedish truck industry is forced to find new material solutions to achieve lighter engines with increased strength. Customers and new environmental regulations demand both higher specific power and more environmentally friendly trucks, and this places a rising pressure on the manufactures. This demand could be met by increasing the peak pressure in the cylinders. Consequently, a more efficient combustion is obtained and the exhaust lowered. This however exposes the engine to higher loads and material physical properties must therefore be enhanced.</p><p>Today, alloyed gray iron is the predominantly used engine material. This material cannot meet the requirements of tomorrow’s engines. Compacted Graphite Iron has good potential to be the replacement; it opens new design opportunities with its superior strength, which can lead to smaller, more efficient engines and additional power. The question is: how will manufacturing be affected?</p><p>The main goal of this thesis is to identify and investigate the main factors’ effect and their individual contributions on CGI machining. When the relationship between the fundamental features; machinability, material microstructure, and material physical properties, are revealed, then the CGI material can be optimized, both regarding the manufacturing process and design requirements. The basic understanding is developed mainly through experimental analysis. No attempt has been made to optimize the material to be used as engine material in this thesis.</p><p>The thesis demonstrates the importance of having good casting process control. It also illustrates the microstructural properties’ effects on CGI machinability, and what new aspects of machining must be taken into account, compared to gray iron.</p><br>OPTIMA CGI
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Khan, Fareed Ashraf. "Some aspects of convection as well as graphite and carbide formations during casting." Licentiate thesis, KTH, Metallernas gjutning, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-228388.
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It is an established fact that segregation during casting affects the physical properties of carbon-based ferro alloys; this motivates the study of the segregation behaviour of carbon and carbide-forming solute elements. In this context, this thesis investigates two different situations: the effects of cooling rate and turbulence on the precipitation behaviour of the graphite nodules in nodular cast iron; the nature of carbide precipitation in a bearing steel grade and the effects of subsequent soaking on these carbides. The structures of boiling water reactor inserts cast by the uphill and downhill casting of nodular cast iron were examined. The samples were taken from representative locations in the top, middle and bottom cross sections of the castings. It was observed that in uphill-cast inserts the nodules were larger but fewer in number the bottom section, whereas in downhill-cast inserts the nodules in the bottom section were smaller, but greater in number. Variation in volume fraction of the graphite nodules across the inserts was also observed. The probable cause of this variation was the difference in cooling rate in different sections of the insert. Between the steel tubes located at the central part of the casting, the fraction of graphite was lower, which could be the result of carburization of the steel tubes. To study the effects of melt stirring during the solidification of nodular cast iron, several experiments were conducted at variable cooling rates and for different stirring times. Examination of the microstructure was conducted using Light Optical Microscope (LOM) and Scanning Electron Microscope (SEM). It was observed that during stirring the melt oxidized and oxide nuclei were formed. The number of nucleation sites for the precipitation of graphite nodules increased, which raised the nodule count and the fraction of the graphite precipitated. The matrix transformed from pearlite to ferrite, which could be due to the fact that more carbon had diffused out of the matrix. The segregation behaviour in hypereutectoid bearing steel produced by ingot casting was also studied. The effects of soaking on micro and macro segregation was investigated in samples taken from as cast and soaked ingots; emphasis was laid on the bulk matrix and A-segregation channels. Samples were also taken from ingots which were soaked and then hot worked. The micro and macro examination of the microstructure was conducted using LOM and SEM. Quantitative and qualitative composition analysis was performed using Energy-dispersive X-ray spectroscopy (EDX) and an electron micro probe analyzer (EMPA). It was observed that M3C, M2C and M6C had precipitated. The carbide morphology in the bulk matrix was different to that in the A-segregation channels. All the primary carbides in the bulk matrix were found to have dissolved after 4 hours of soaking at 1200oC.<br>Det är ett faktum att segringar som uppstår under gjutning påverkar materialegenskaperna hos kolbaserade järnlegeringar; detta utgör motivationen till studien av segringsuppträdandet hos kol och karbidbildande ämnen. Denna avhandling behandlar två olika aspekter inom ramen för detta ämne: påverkan av kylningshastighet och turbulens på kärnbildningen av grafitnoduler i nodulärt gjutjärn samt karbidbildning i kullagerstål och dess påverkan på den efterföljande värmebehandlingen av dessa karbider. Strukturen hos rör till vattenkokare som tillverkats av nodulärt gjutjärn som gjutits med fyllning från botten eller från toppen undersöktes. Prover togs från representativa tvärsnittspositioner från toppen, mitten och botten av de gjutna ämnena. Resultaten visade att användandet av bottenfyllda kokiller gav upphov till större men färre karbider i nedre delen av ämnet, medans användandet av toppfyllda kokiller gav upphov till mindre men fler karbider i nedre delen av ämnet. Variationer av volymfraktionen av grafitnoduler längs tvärsnitten observerades också. Den mest sannolika orsaken till denna variation var skillnaden i kylhastighet i de olika områdena av tvärsnitten. Hos rör tillverkade av det centrala delen av ämnet så var fraktionen grafit lägre, vilket kan bero på en uppkolning av rören. Ett flertal experiment utfördes med varierande kylningshastigheter och olika omrörningstider för att studera inverkan av omrörning av smältan på stelningen av nodulärt gjutjärn. Studier av mikrostrukturen genomfördes med ljusoptisk mikroskopi och svepelektronmikroskopi. Resultaten visade att smältan oxiderades under omrörningen, vilket resulterade i bildandet av oxider. Detta ledde till en ökning av kärnbildningsområden för grafitnoduler, vilket ledde till en ökning av antalet noduler samt fraktionen av grafit som fälldes ut. Strukturen omvandlades från perlit till ferrit, vilket troligen orsakades av att kol hade diffunderat ut från strukturen. Segringsbeteendet hos hypereutektoida kullagerstål tillverkade genom götgjutning undersöktes också. Effekten av värmebehandling på mikro- och makrosegringar undersöktes i prover tagna från gjutna och värmebehandlade ämnen. Fokus var på att studera strukturen i ämnena samt A-segringar. Dessutom togs prover från ämnen som först värmebehandlats och därefter varmbearbetats. Både mikro- och makroundersökningar av mikrostrukturen utfördes med ljusoptisk mikroskopi och svepelektronmikroskopi. Dessutom så genomfördes kvantitativa sammansättningsbestämningar med energidispersiv röntgenspektroskopi och elektronmikroprobsanalys. Resultaten visade att M3C, M2C och M6C karbider hade fällts ut. Karbidmorfologin i huvuddelen av strukturen skiljde sig från den som återfanns i A-segringar. Samtliga primära karbider i huvuddelen av strukturen hade lösts upp efter 4 timmars värmebehandling vid 1200oC.<br><p>QC 20180523</p>
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Sun, Chi-Hung, and 孫啟宏. "A Study on Metal Mold Centrifugal Casting of Compacted Graphite Cast Iron and Compacted Graphite Cast Iron Based Composites with TiC." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/16789614195744638932.
Full textAbstract:
碩士<br>義守大學<br>材料科學與工程學系<br>89<br>Abstract
The effect of process parameters, which include the amounts of spheroidizer (0.19~0.94wt%), the amount of inoculator (0.4~1.0wt%), the times gravity (70~110G), the pouring temperature (1350~1420℃),and the CE value (4.08~4.52%), on the microstructures and mechanical properties of centrifugally cast compacted graphite iron were studied. This data base were applied to develop compacted graphite iron based composite with concentration gradient distribution of TiC particles on the inner surface layer. Some process parameters will be investigated. They are titanium content (0~0.54wt%), the times gravity (70~110G), the pouring temperature (1349~1394℃), and the amount of inoculator (1.0~1.4wt%). The effect of process parameters on the amounts of TiC , microstructures and mechanical properties were investigated.
The results showed that the good compacted graphite shape can be obtained in the residual Mg content between 0.013~0.023wt%. When the residual Mg content at 0.018wt%, we can obtain the best vermicular graphite shape. The amount of carbide increases with increaseing times gravity. The tendency of carbide formation decreases with inccresing CE value. On the other hand, the amounts of ferrite , ductility, and tonghness have opposite tendency with CE values.
The results also revealed that the distribution of TiC particles in the radial direction is in the order of interior region > outside region . For the mechanical properties, the tensile strength increases with increasing the times gravity, but the tendency of ductility is contrary. The tensile strength decreases with increasing the amount of inoculator.
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Tai, Huang Kuo, and 黃國泰. "The Study of Compacted Graphite Cast Iron Process Stability." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/44331479904180955780.
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碩士<br>國立臺灣師範大學<br>工業教育研究所<br>90<br>ABSTRACT
This paper is mainly focusing on the study of the amount of the three kinds of spheroidizing, KC alloys、CG alloys、Rare earths that is needed to produce the compacted graphite cast iron, and on the study of the stability in the process of producing optical microscope observation and mechanical property under as identical condition as possible. Besides, this paper will do the comparison between the stability of the two base structures under two different speed of annealing.
The results shows that the amount needed to produce the compacted graphite cast iron is 0.8% with CG alloy-spheroidizing, 0.3% with KC alloy-spheroidizing, 0.8% with Rare earths; and what’s more, the above three kinds of spheroidizing have to add 0.2% dose of inoculation. According to the gauging, the coefficient of variance of the compacted rate of graphite is 44.98, and the standard deviation of it is 6.71, which is the smallest. In addition, the average figure of the eight-time experiment is 88.13% so to add KC alloys can make the process of producing the compacted graphite cast iron most stable.
From the results of the experiment, CG alloys can produce better mechanical quality of the compacted graphite cast iron, and have more stable process of producing it. When the compacted graphite cast iron is under the process of the annealing, neither the temperature quenching down to 260°C in the stove before quenching in the air nor quenching the temperature directly in the air will have influence on getting the complete ferrite structure.
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Javaid, Amjad. "Morphological features of spheroidal graphite in ductile cast iron." 1989. http://catalog.hathitrust.org/api/volumes/oclc/20078809.html.
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Thesis (M.S.)--University of Wisconsin--Madison, 1989.<br>Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 108-113).
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Hu, Chen-Yu, and 胡鎮宇. "Production of Graphite from Catalytic Liquid Cast Iron Bath." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/f987bp.
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碩士<br>國立清華大學<br>材料科學工程學系<br>106<br>Via the use of iron-carbon phase diagram and the theory of graphitization of carbon in cast irons, this study investigates an
innovative method for continuously, effectively and efficiently, as well as environment-friendly producing graphite in a catalytic cast iron bath. It is concluded that the transformation from amorphous carbon to graphite via the method is available, and the degree of graphitization (DOG) described in this study reaches a high value of more than 93% like that of Acheson’s. Furthermore, the DOG is process-controlled and is independent of carbon source in the hypereutectic catalytic cast iron melt.
The observance of graphite flotation in liquid catalytic cast iron bath manifests the production of graphite is achievable by the fluidized bed method.
The first part of this study describes the inductive melting (IM) of alloys of iron, carbon, and silicon at 1600oC for full melting; holding at temperatures higher than the eutectic temperature of 1500oC for 4 h for graphitization of carbon; and then lower the temperature to 25oC for test specimens. The IM specimens, being XRD and OM-checked firstly, are further pickled to obtain graphite that is also XRD-, OM- and ICP-analyzed to compare with graphite obtained from nodular cast iron and gray cast iron.
The second part is about the vacuum arc re-melting (VAR) experiment of the specimens that are obtained in the first part. The effects of the number of VAR process and the addition of synthetic graphite on the DOG are checked with OM. The graphite samples of VAR specimens after pickled are checked with graphite production yield analysis, XRD for the comparison of the DOG, and ICP for the composition analysis.
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Salim, Mohammad. "Tribological Behavior of Heat Treated Spheroidal Graphite Cast Iron." Thesis, 2015. http://ethesis.nitrkl.ac.in/7196/1/Tribological_Salim_2015.pdf.
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The main aim of this project is to investigate the microstructures of different matrix samples and correlate to the wear system response by varying matrix microstructure. SG iron is used for the production of different automobile parts such as camshaft and gears. SG iron is most important member among different members of cast iron family due to its high strength, toughness together with ductility. The main reason of this high ductility is presence of nodular structure of graphite that is present in it unlike present in grey cast iron as the flakes. In grey cast iron, stress concentration is high at the corners of these flakes but has been removed in the case of spheroidal graphite cast iron with the nodular shape. As a result of this its ductility increases along with toughness. In order to obtain the optimum wear resistance of SG cast iron, the current investigation involves annealing, normalizing, quench & tempering and austempering heat treatments leading to transformation of as-cast matrix to ferritic, pearlitic, tempered martensitic and coarse upper bainitic matrices respectively. Specimens having different alloying elements were austenitized to 1000°C for soaking time 90 min, followed by furnace cooling, air cooling, oil and salt bath quenching followed by air cooling for respective heat treatments. Vickers hardness test was conducted over the samples under 20Kg followed by wear test was carried over DUCOM TR-208 M1 ball on plate type wear monitor under 10N, 30N and 50N loads respectively in dry sliding condition for the sliding distance of 7.54m with the speed 0.063m/s. The hardness was maximum for quenched & tempered specimen in case of SG-02 samples due to presence of tempered martensitic matrix phase while, in case of SG-01, normalized specimen has maximum hardness due to presence of pearlitic matrix phase. The lowest hardness was observed to be for annealed sample with ferritic matrix phase. On the other hand hardness of ferritic, pearlitic and bainitic matrices was observe to be in between these range, also marginal difference was observed in as-cast and tempered martensitic matrices. The cause of this difference is that in as-cast specimen of iv SG-01 has bull’s eye ferritic/pearlitic matrix which may cause its hardness increases, whereas in case of as-cast sample of SG-02 fully ferritic phase is obtained as a result of which hardness decreases. For quench & tempered as well as austempered specimens of SG-01 has lower hardness value in comparison of that of in SG-02 because of more percentage of C, Mn, Ni, Cr, Mo and Si in SG-02 specimens that has tendency of strengthening solid solution of ferrite in ductile cast iron. It was observe that when sample of as-cast specimen subjected to load in between 10N- 20N it lost its weight continuously, while with increase in load to 30N subsequently weight gain was observe. This weight gain is due to the formation of oxide layer. There was no weight loss or gain observe for normalized specimen however in case of austempered specimen weight gain was observe for 20N and 30N due to formation of oxide which can be investigated by means of EDAX analysis. Finally it has been concluded that for the samples having ferritic, pearlitic, bainitic matrices phase, adhesive wear is main wear mechanism along with shallow pits are produced due to delamination and deposited over the sites where graphite nodules have already formed before.
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簡絲男. "A Study on the Resonant Vibration Characteristic of As-Cast Spheroidal Graphite Cast Iron." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/54420264935403337707.
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碩士<br>國立成功大學<br>材料科學及工程學系<br>87<br>Spheroidal graphite (SG) cast iron has been used in many automobile components. During application, resonant vibration may occur and cause failure. A lot of these automobile components are used in as-cast condition, so systematic exploration of the resonant vibration characteristics of as-cast SG cast iron is necessary. In addition, the resonant vibration test can also be applied to separate the sprue and workpiece in investment casting. The as-cast SG cast iron of 3.6wt%C-2.9wt%Si was used in this study. By varying the cooling rate after solidification, different matrix structures (pearlite components) were available, which aimed to study the effect of matrix structures on resonant vibration characteristics.
During resonant vibration, the variation of deflection amplitude vs. vibration cycles could be divided into three stage. Firstly, the deflection amplitude maintain about constant for a certain period of vibration cycles (stage I). Then, the deflection amplitude decreases significantly with increasing vibration cycles. In the third stage, the deflection amplitude maintains about constant again, but significantly lower than the deflection amplitude of stage I. The above mentioned feature of three-stages behavior is related to the result of crack initiation and propagation. Mostly, microcracks initiate from the interface between graphite nodules and matrix, and fewer microcracks initiated from the inclusions in eutectic cell wall. Microcracks propagated to link each other and finally become major cracks with increasing vibration cycles. The process of crack initiation and linking were proceeding during the stage I period. After the formation of major cracks, the major cracks propagate through the thickness direction, then the effectic elastic modulus of specimen was reduced. Due to the drop of elastic modulus, the deflection amplitude decreased significantly as shown the feature of "stage II". In stage 3, the lower of deflection amplitude and cracking rate makes another plateau region.
The experimental results showed that the increment of pearlite contents would slightly increase the resonant frequency of specimen. The damping capacity decreases with increasing pearlite content and so does deflection amplitude. After initiation, the cracks propagated in. The cracks propagated in the pearlite matrix along two paths. Sometimes it goes along the cementite platelets and sometimes through cementite platelets. Mostly, cracks propagated transgranularly in ferrite matrix, but fewer intergranular fracture near the bull''s-eye region is also observed by SEM.
As the crack extends, the deflection and brunching occur on the grain boundaries of ferrite, the interface between ferrite and pearlite and the cementite platelets with different orientation. Thus, the driving force for crack propagation is reduced. Although the pearlite content can cause the deflection amplitude under resonant, to increase the crack propagates in the pearlite with higher degree of deflection and branching and the pearlite can retard crack extension. Therefore, the resonant vibration life can be improved with increasing the pearlite content.
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Wu, Kuo-Lung, and 吳國龍. "Study on Erosion Wear of Spheroidal Graphite Cast Iron Pipes." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/ktpbnu.
Full textAbstract:
碩士<br>國立臺北科技大學<br>材料及資源工程系所<br>94<br>Spheroidal graphite cast iron has been widely used in many structure fields of industry due to its superior mechanical properties. This research takes three kinds of commercial spheroidal graphite cast iron pipes, centrifugal casting pipe, centrifugal casting pipe with annealing treatment and sand casting fitting, which were to undergo solid erosion test using angular Al2O3 particles. The purpose of this research is to study the effect of erosion on spheroidal graphite cast iron pipes and fitting which possess various microstructures and mechanical properties due to the different manufacturing processes and heat treatment. The experimental results showed that the microstructure of centrifugal casting pipe consists of larger amount of cementite because of the fast cooling rate and higher degree of overcooling, resisting in the improvement of hardness and erosion resistance. Centrifugal casting pipe with annealing treatment, turning its microstructure into full of ferrite by carbon atom diffusing to nodular graphite and ferrite, is least resistant to erosion with the highest erosion rate and the maximum erosion depth. The microstructure of sand casting fitting is mixed with pearlite and ferrite, with the mechanical property just laying between the other two pipes, which makes the erosion rate and erosion depth follow the same trend. The max. erosion rate occurred at incident angle 30°∼45°according to different solid erosion particle amounts, and the deepest erosion depth occurred consistently at incident angle 60°, for the three comparison specimens. The test also reveals that the failure mechanism of spheroidal graphite cast iron pipes and fitting tend to be ductile-brittle fracture.
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Mittal, Ranjan, and Sunit Nanda. "Property enhancement of spheroidal graphite cast iron by heat treatment." Thesis, 2010. http://ethesis.nitrkl.ac.in/1627/1/B.Tech_Thesis_Final.pdf.
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Ductile iron or popularly known as Spherodized graphite iron (SG iron) is a special variety of cast iron having carbon content more than 3% and has graphite present in compact, spherical shapes. These compact spheroids hamper the continuity of the matrix much less than graphite flakes which results in higher strength and toughness with a structure that resembles gray cast iron, thus imparting superior mechanical properties i.e. much higher than all other cast irons and which can be compared to steels. This unique property enables ductile irons to be used for
numerous industrial applications.
Alloying element addition greatly affects the mechanical properties of SG iron with Si, Mn, Cu and Ni being more predominant. While copper helps increasing the tensile strength and hardness causing no embrittlement in the matrix, Ni helps enhancing the U.T.S without affecting the
impact test values. Thus addition of Cu and Ni plays an important role in determining the end properties of SG iron after heat treatment.
The high ratio of performance to cost which they offer to the designer and end user makes them to be used extensively for industrial applications. However, to extend the consistency and range of properties of SG iron castings beyond its properties in as-cast condition, Heat treatment is a necessary operation. Tempering and Austempering are the two most widely used heat treatment operations in SG iron. For example a ferritic iron having 70-80% ferrite has a yield strength of 350Mpa while a similar material which is given a step quenching treatment shows a yield strength of 550-1250Mpa. Recently developed Austemperd Ductile iron (ADI) has good abrasion resistance combined with excellent ductility and toughness.
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Majhi, Pabitra Kumar, and Santosh Kumar. "Effect of tempering temperature & time on impact properties and microstucture of spheroidal graphite iron." Thesis, 2014. http://ethesis.nitrkl.ac.in/6255/1/110MM0358-2.pdf.
Full textAbstract:
Spherodized graphite iron (SG iron)or popularly known as Ductile iron is a special variety of cast iron having carbon content more than 3% and has graphite present in spherical shapes. mechanical properties which are much higher than other cast irons and which can be comparable to steels. Thus enables SG irons to be used for numerous industrial applications. Alloying element addition greatly affects the mechanical properties of SG iron with Mn, Cu, Si and Ni being more predominant. While copper helps increasing the hardness causing no embrittlement in the matrix, Ni helps enhancing the ultimate tensile strength without affecting the impact energy values. Therefore addition of Cu and Ni plays key role in determining the end properties of SG iron after heat treatment. The high ratio of performance to cost which it offers to the designer and end user makes it to be used extensively for industrial uses. However, to enhance the consistency & range of properties of SG iron beyond its properties while in as-cast condition, Heat treatment is a required operation. Tempering & Austempering are two most widely used heat treatment operations in Ductile iron. For example a ferritic iron containing 70-80% ferrite has a yield strength of 350Mpa while a similar material which is given a step quenching treatment shows a yield strength of 550-1250Mpa. Recently developed Austempered Ductile iron (ADI) has good abrasion resistance combined with excellent ductility and toughness.
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Lin, Guan-Yu, and 林冠宇. "A study on nitrocarburing of graphite cast iron with different pretreatment." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/8syv42.
Full textAbstract:
碩士<br>國立中興大學<br>材料科學與工程學系所<br>107<br>The purpose for the study was to assess the effects of different Nitriding Pretreatments on the nodular cast iron FCD550, including use the shot peening treatment or phosphate treatment. First of all, testing personnel choose the suitable nitrocarburing temperatures and using different sizes of the steel ball to shot peening (0.15mm, 0.25mm, and 0.8mm steel balls ) the surface of nodular cast iron FCD550 before the cast iron put into Nitriding Pretreatments. Then separately using zinc phosphate for 15 minutes, manganese phosphate for 15 minutes, manganese phosphate for 30 minutes of nodular cast iron FCD550 before the cast iron put into Nitriding Pretreatments.
For shot peening to create six different surface pretreatment conditions, and choose the 530℃ nitrocarburing. Then Vickers Type Tester, X-ray diffraction measuring instrument (XRD), Microscope, surface roughness, shape measuring instrument (Surfcom) and the Stress Measurement System were used for characterization to help figure out the mechanisms
For the graphite cast iron (FCD550), the nitriding process was tested by selecting three different temperature parameters. It was found that the maximum surface hardness and the lowest porosity were obtained under nitriding temperature of 530 °C. In the pretreatment, it was found that sample has different effects on the porous layer after shot peening, and the 0.8 mm steel ball can slightly improve the nitriding efficiency. And in it was found that different phosphate treatment before nitriding have different resulted. The results showed that the phosphate treated sample improves nitriding efficiency and makes the porous layer thinner
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Tsai, Dran-Ren, and 蔡端任. "The Influence of Chromium on The Austempered Flake Graphite Cast Iron." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/p8rpj5.
Full textAbstract:
碩士<br>國立臺北科技大學<br>材料科學與工程研究所<br>97<br>The study was carried out to change austempering temperature (300℃~400℃), and the content of chromium (0.3~1.5wt%). The flake graphite cast iron were austenitized at 900℃ for 2 hours, and then quenched to the austempering temperature and holded the temperature for 2 hours. The study was to examine the influence of the austempering temperature and the percent of chromium on the mechanical properties and the microstructure of the austempered flake graphite cast iron.
The result of the study showed that the matrix were composed of ferrite and block and a few of string-type of austenite. When the austempering temperature were low temperature, the structure of ferrite were to grow and coarse, and the retained austenite content and the value of retained austenite content multiplied by the carbon content of austenite rises with rising austmpering temperature. The Heat treatment in the same conditions, when the chromium content was lower, the retained austenite volume fraction was decrease; when the chromium content was higher, there was formation of carbide precipitation in the matrix, caused to increased austenitic volume fraction, the ratio of chromium content of carbide and the matrix, it will decrease as the temperature increases.
When the tempering temperature increased, the mechanical properties of the casting iron, the hardness and tensile strength will be drop, and the ultimate tensile strength occurs in the 1.5wt% Cr, and austempering temperature at 300 ℃ to 1448 MPa.
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Behera, Ranjan Kumar. "Development Of Spheroidal Graphite Cast Iron For Nuclear Fuel Transport Cask." Thesis, 2016. http://ethesis.nitrkl.ac.in/8634/1/2016__Phd__511MM606_RANJAN_KUMAR_BEHERA.pdf.
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In the present work SG iron specimens with carbon equivalent (%CE) ranging from 4.12 - 4.36, has been subjected to annealing, normalizing, quench & tempering, austempering and DMS treatment to obtain different matrix microstructure and microconstituent. Optical microscopy is observed for microstructure, phase volume fraction, nodularity, and nodule count for each of the as-cast and heat treat specimens. XRD analysis is done to validate the phases present in each specimen as well as to determine the amount of carbon dissolution in respective phases. Mechanical properties such as tensile strength, % elongation, Vicker’s hardness, and impact strength are measured by conducting necessary test following ASTM standards. Failure mechanisms involved in static and dynamic loading are investigated observing the fracture surfaces after tensile and impact test respectively, under Scanning Electron Microscope. The corrosion behavior of as-cast and heat treated specimens, (in sea water) is also studied. Specimens are immersed completely in sea water at room temperature and pressure, and the weight difference is recorded at regular intervals, for twelve weeks. The mechanical properties showed a quite good relationship with microconstituents for respective as-cast and heat treated specimens. The as-cast specimens show graphite spheroids within ferritic matrix resulted in increased ductility and impact strength (with increasing ferrite volume fraction) caused by increasing Si content. Annealing treatment led to the presence of completely ferritic matrix for every alloy consequently increasing ductility and impact toughness as compared to as-cast matrices. On the other hand specimens which underwent quenching & tempering treatment show the highest strength and hardness due to the tempered martensitic matrix, among all other heat treatment processes. Strength and ductility values of normalized austempered and DMS-treated specimens are intermediate to those of lowest strength value for annealed specimen and higher elongation value and that of highest strength and lowest elongation value for the quenched & tempered specimens. It is observed that the elongation increases with increased nodularity can be attributed to increases amount of Mg and Ce, whereas nodule count increases the hardness of respective as-cast and heat treated specimens. The increase of hardness may be due to increase of Ni and Cr content which provides strength to ferrite via solid solution strengthening (for ferritic specimens). Normalizing treatment produced a ferritic/pearlitic matrix and showed increased UTS and hardness with increased pearlite content. Austempered heat treatment resulted in coarse upper bainitic matrix leading to suitable combination of strength and ductility, whereas matrix consists of martensite and ferrite are obtained by DMS treatment. The failure mode for the soft ferritic matrix is observed to be ductile in nature caused by microvoid coalescence, and that of other matrices are mostly brittle signified by the presence of low energy stress paths (River marking) and cleavage facets. Mechanical properties of SG iron alloys studied in current research, found to be well above the recommended properties for fabrication of nuclear fuel cask, (in as-cast as well as heat treated conditions) and hence can successfully be used for the desired purpose.
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Lin, Shin-Chin, and 林士晴. "A Study on the Resonant Vibration Characteristics of Spheroidal Graphite Cast Iron." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/77878078487847818259.
Full textAbstract:
碩士<br>國立成功大學<br>材料科學(工程)學系<br>85<br>AbstractSpheroidal graphite (S.G.) cast iron has been used in
many automobile components. However, during application,
resonant vibration fatigue may occur and cause failure. To make
sure the safety and reliability when practicing, systematic
exploration of the resonant vibration fatigue characteristics is
necessary. The S.G. cast iron of 3.6wt%C-2.8wt%Si were explored
in this study. By varying the solidification rate and heat
treatment procedures, six distinctive test materials which have
two different nodule counts and three matrix structures
including ferritic, pearlitic and as-cast were available. The
experimental results show that the vibration deflection of the
six test materials were all larger in resonant frequency than in
other situations. The resonant deflection maintained about
constant in the initial stable period then decreases with
increasing vibration cycles in the final unstable period.
Surface microcracks initiated from the vicinity of graphite
nodules in the stable period, then they propagated and linked to
form a major crack. In the unstable period, the effective
elastic modulus was changed due to the formation and propagation
of the major crack giving rise to the descending deflection as
observed. In view of the matrix effect, the deflection of
pearlitic specimen was larger then ferritic specimen because of
the lower damping capacity. Although the change of
solidification rate did not have apparent influence on the
resonant deflection, the specimens of faster solidification rate
were more resistant to resonant vibration. And the resonant
life of the as-cast specimens was longer then the ferritic ones.
Because of the largest vibration deflection, the pearlitic
specimens showed the shortest resonant life. All the test
materials have the similar resonant vibration failure
characteristics which can be defined into four steps. In step
I, surface plastic flow and microcracks initiate at the
interface of graphite nodules and matrix; in step II, surface
microcracks propagate by linking with each other; in step III, a
major crack forms at the part which suffers the largest bending
force; finally in step IV, the major crack propagates along the
through-thickness direction. The resonant cracks propagate
transgranularly in ferritic specimen; they propagate randomly
through the lameller structure structure of the pearlitic
specimen. After step IV, SEM observation shows brittle fracture
on the fracture surface of all the six test materials.
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li-de, jiang, and 姜禮德. "Study on Microstructure of Compacted Graphite Cast Iron with In-Mold Treatment." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/48735441388214274787.
Full textAbstract:
碩士<br>國立臺灣師範大學<br>工業教育研究所<br>89<br>This study mainly focuses on the effect on the microstructure of the compacted graphite iron according to designs of the runner systems, and the different kinds, shapes and quantities of the treatment alloy. The results of the research is below:
1.We can get better rates of the compacted graphite by using the runner systems of the mixed reaction chamber, especially in M-C(fig.3-11) and M-H(fig.3-16).
2.It is not good to put the filter upon the outlet horizontally; otherwise it would be obstructed. It is not good to deal with the molten iron directly from the bottom of the reaction chamber; otherwise the treatment alloy would float on the surface of the molten iron and not be dissolved easily.
3.To adopt the treatment alloy with taper-pipe shape and the SSA is bigger than 50, the rate of the compacted graphite is the highest.
4.When the diameter of a grain of treatment alloy is less than 5mm, it is suitable for the common reaction chamber. Because the gaps between grains are too small, the molten iron can’t flow easily and mix with them. Besides, the diameter, which is more than 5mm, is suitable for the mixed reaction chamber.
5.When choosing the KC-5 treatment alloy and the quantity is 0.8%, we can get the highest rate of the compacted graphite.
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LIN, JIN-HONG, and 林錦宏. "A various analysis in low temperature strength of spheroidal graphite cast iron." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/17963455411829285192.
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