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1
Taivalkoski, Olivia. "Evaluation of material properties after laser welding on ductile cast iron." Thesis, KTH, Materialvetenskap, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-254653.
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Scania wants to lower the weight of their trucks, including the goal to reduce the carbon dioxide emissions, and one way to do that is to use laser welding instead of fastenings.This bachelor thesis work is about laser welding of ductile cast iron, or spheroidal graphite cast iron or nodular cast iron, to QT-steels and case hardening steel and evaluation of the mechanical properties of the weld. Also laser welding of cast steel to the same two materials are being evaluated in this work. Tests are done to evaluate the effect on the material from laser welding. The tests are tensile tests and Vickers hardness test; both across and along the weld and in some areas of interest. EDS (Energy Dispersive X-Ray Spectroscopy) is used to analyze the composition in the weld and light optical microscope is used to look at the fusion zone (FZ) and the heat affected zone (HAZ). The results shows that the hardness is high in the heat affected zone due to the formation of martensite and that the materials mix more towards the root of the weld. The materials also mix more if the weld depth is deeper. The width of the heat affected zone seems to be longer if the heat input is higher. It is also clear that welding of cast steel is less complicated than the welding of ductile cast iron. That is because ductile cast iron gets a hard and brittle heat affected zone (HAZ) while the cast steel does not. The cast steel can also be welded without filler wire without getting to hard or to brittle. If laser welding is to be used in the future the component should be constructed in such a way that the fusion zone is not carrying the main load. Tests on fatigue strength should also first be done on a finished component as it cannot be tested on the samples in this work. This work was conducted at Scania AB and the royal institute of technology, KTH, in Sweden.Scania vill sänka vikten på sina lastbilar, bland annat för att minska utsläppen av koldioxid, och ett sätt att göra det är att lasersvetsa istället för att använda bultar. Detta kandidatexamensarbete handlar om lasersvetsning av segjärn, eller nodulärt gjutjärn som det också kallas, till seghärdningsstål och sätthärdningsstål samt utvärdering av svetsens mekaniska egenskaper. Även lasersvetsning av gjutstål till samma stålsorter som ovan utvärderas i detta arbete.Tester görs för att utvärdera effekten på materialet från lasersvetsningen. Testerna är dragprov och Vickers hårdhetstestning; både tvärs över och längs med svetsen samt även i vissa områden av särskilt intresse. EDS (Energy Dispersive X-Ray Spectroscopy) används för att analysera sammansättningen i svetsen och ljusoptiskt mikroskop används för att se svetsgodset och den värmepåverkade zonen. Resultaten visar att hårdheten går upp i den värmepåverkade zonen på grund av martensit bildning och att materialen blandar sig mer närmare svetsroten. Materialen blandar sig också mer om svetsdjupet är djupare. Den värmepåverkade zonens bredd verkar vara större om sträckenergin är hög. Det står också klart att svetsning av gjutstål är mindre komplicerat än svetsning av segjärn eftersom segjärnet får en hög hårdhet i den värmepåverkade zonen medan det inte alls blir så för gjutstålet. Gjutstålet kunde också svetsas utan tillsatsmaterial utan att få ett för hårt eller sprött svetsgods. Om man vill använda lasersvetsning i framtiden ska komponenter konstrueras så att svetsen inte bär huvudvikten eftersom resultatet visar att svetsgodset får lägre brottgräns. Utmattningstester borde också göras på en färdig komponent eftersom det inte kan testas på proven från det här arbetet. Detta arbete utfördes på Scania AB och Kungliga Tekniska Högskolan, KTH, i Sverige.
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Procházka, Jan. "Vliv opravného zavařování za tepla na změnu struktury a tvrdost odlitků z litiny s lupínkovým grafitem." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-400486.
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The master‘s thesis deals with the influence of the thermal cycle of welding with preheat on castings made of grey cast iron to change the hardness. The thesis deals with the classification of graphitic cast irons, their structure, properties and influences they have on the formation and transformation of the structure. Emphasis is placed on chemical composition and structure stability at elevated temperatures. The practical part deals with the investigation of the effects of casting repair on the decrease of hardness measured in the foundry Heunisch Brno.
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Erturk, Murat Tolga. "Microstructural And Mechanical Characterization Of Metal Active Gas Welded Joint Between Cast Iron And Low Carbon Steel." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12612992/index.pdf.
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This study focuses on joining pearlitic ductile cast iron with low carbon steel by welding and investigation of this joint in microstructural and mechanical viewpoints. For this purpose E355 steel and GJS600-3 cast iron were joined using metal active gas (MAG) welding process by G3Si1 filler wire. The joining process is shaped mainly by the problems related to the low weldability of cast. Preheating was applied to prevent formation of cooling cracks and effects of post weld heat treatments (PWHT) were surveyed. Micro examination and micro hardness tests were applied to characterize the general microstructure. Grain size measurements were done for E355. Hardness profiles, tension and impact toughness properties were designated via mechanical tests. Fatigue behavior was surveyed and general fracture characteristics were determined via scanning electron microscopy (SEM) examinations.
According to study it was concluded that successful weld joint could be formed between the materials by suitable preheating. Formation of ledeburitic white cast iron and martensite in heat affected zone of cast piece was witnessed. It was possible to lower high hardness values of these phases gradually by increasing post weld heat treatment temperatures. The weld joint behaved superior to the base metals under tension and fatigue tests. In tension tests failure occurred at E355 base metal whereas fatigue loading resulted failure at GJS600-3. A great impact toughness variation was determined between two pieces. It is seen that heat treatments had minor effect on mechanical test results except hardness. The study was concluded that a useful fusion weld joint between these materials can be built.
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Rüthrich, Karsten. "Beitrag zur Entwicklung des Elektronenstrahl-Mehrspot/Mehrprozess-Schweißens von Gusseisen/Gusseisen- und Gusseisen/Stahl-Verbindungen ohne Schweißzusatzstoffe." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2014. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-149349.
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Ziel der Arbeit war die Entwicklung des Elektronenstrahl-Mehrspot/Mehrprozess-Schweißens für Gusseisen/Gusseisen- und Gusseisen/Stahl-Verbindungen ohne Schweißzusatzstoffe. Im Vergleich zum Einbad-Schweißen entsteht beim Mehrbad-Schweißen eine porenarme Schweißnaht, gleichzeitig senkt sich die Schweißnahthärte geringfügig ab. Dabei kann die Kaltrissbildung in der Schweißnaht für arteigene Gusseisen-Verbindungen nicht unterdrückt werden. Für Mischverbindungen ist der Strahlversatz der bestimmende Schweißparameter beim Mehrbad-Schweißen. Über diesen kann sowohl die chemische Zusammensetzung der Schweißnaht eingestellt als auch ohne Vorwärmen eine kaltrissfreie Schweißnaht für Gusseisen/Stahl-Verbindungen erzeugt werden. Für die prozessintegrierte Wärmebehandlung der Fügezone wurde ein neues EB-Thermofeld entwickelt. Durch den Thermofeldeinsatz konnte die Aufhärtung in der Schmelz- und Wärmeeinflusszone signifikant reduziert werden und die mechanischen Eigenschaften der Schweißverbindungen wurden deutlich verbessert.
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Argo, Donald. "Microstructural transitions in directionally solidified graphitic cast irons." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=65926.
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Chen, Zhen-da. "Laser surface melting and alloying of cast irons." Thesis, Imperial College London, 1987. http://hdl.handle.net/10044/1/38260.
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Silva, Diego Rodrigo da. "Estudo comparativo entre arames na soldagem de mancais de ferro fundido em compressores herméticos para refrigeração." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/18/18158/tde-14122017-100027/.
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Nos dias atuais, com o mercado altamente seletivo, com vários fabricantes e fornecedores de diversos tipos de produtos e serviços, a qualidade se tornou uma necessidade premente, na qual uma empresa que forneça bens e/ou serviços com baixa qualidade corre sérios riscos de ser descartada pelos mercados consumidores. Assim, a importância da qualidade é que se converteu em um requisito básico para uma empresa competir e se manter no mercado. As empresas veem a qualidade como uma ferramenta para a redução de custos e para a melhoria de sua imagem junto ao mercado consumidor. Neste contexto, de melhora da imagem junto ao mercado consumidor e de redução de custos, o presente trabalho foi realizado em uma importante e tradicional multinacional de grande porte que produz compressores herméticos para refrigeração, com o intuito de estudar a soldagem do mancal de ferro fundido à carcaça de aço de baixo carbono em compressores rotativos (rolete excêntrico), utilizados em aparelhos de ar condicionado. A solda realizada de maneira falha pode permitir a perda do entreferro do motor, resultando em um ruído característico, chamado stall. Este trabalho avaliou diferentes tipos de arames, buscando garantir um processo com qualidade e baixo custo. Testes foram realizados utilizando como peças teste carcaças e mancais dos compressores. Verificou-se que o arame sólido ANSI/AWS A5.18 ER70S-6, atualmente utilizado, não é o mais indicado para a respectiva soldagem, em virtude da microestrutura e da resistência da soldagem obtida. A solução técnica apropriada é a utilização do arame ERNiFeMn-CI que elimina a fragilização das zonas parcialmente fundidas e diluídas próximos ao metal de solda, enquanto o arame metal cored E70C-6M representa um compromisso entre as propriedades da junta soldada e custo do processo.Nowadays, with the highly selective market, with several manufacturers and suppliers of various types of products and services, quality has become a pressing need, in which a company that provides services with a low quality at serious risk of being discarded by the consumer markets. Thus, the importance of quality is that it has become a basic requirement for a company to compete and stay in the market. Companies see the Quality as a tool to reduce costs and to improve its image with the consumer market. In this context, the improvement of the image with the consumer market and costs reduction, this study was conducted in a major traditional large multinational that produces hermetic compressors to refrigeration, in order to study the welding of cast iron bearings with low carbon steel houses in rotary compressors (eccentric roller) used in air conditioners. The welding performed in a failure may allow loss of the air gap of the motor, resulting in a characteristic noise, called stall. This study evaluated different types of alloys, aiming to ensure process quality and low cost. Trials were done using low carbon steel houses and cast iron bearings of the compressors. After innumerous tests, it was found that the ANSI/AWS A5.18 ER70S-6 solid wire, currently used, is not the most suitable for their welding, in view of microstructure and resistance of the weld obtained. The appropriate technical solution is to use the wire ERNiFeMn-CI eliminating the weakening of partially melted and diluted zones near the weld metal, while metal cored wire E70C-6M represents a compromise between the properties of welded joint and the cost of the process.
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Talks, Miles Garston. "Erosion and corrosion of cast irons under cavitating conditions." Thesis, Coventry University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303009.
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BAPTISTA, ALIXANDRE COELHO. "CORRELATION BETWEEN MICROSTRUCTURE AND FATIGUE LIFE IN NODULAR CAST IRONS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2004. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=6576@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROEsta pesquisa teve como objetivo avaliar a vida-fadiga de dois ferros fundidos nodulares modificados metalurgicamente, sendo uma classe predominantemente ferrítica e outra.perlítica. Inicialmente, amostra dos dois ferros fundidos nodulares ferrítico e perlítico foram fundidas adotando-se moldação em areia na geometria padrão Y-block. Em seqüência, corpos de prova para ensaios mecânicos e de fadiga foram usinados das amostras ferríticas e perlíticas. Após os ensaios de tração e dureza, realizaram-se análises metalográficas qualitativas e quantitativas em ambos os materiais, com o intuito de se determinar suas características metalúrgicas, tais como contagem, distribuição e classe dos nódulos de grafita, bem como quantidade da matriz ferrítica e perlítica. Dando continuidade a etapa experimental, as curvas tensão versus número de ciclos para a falha do ferro fundido nodular ferrítico e do ferro fundido nodular perlítico foram levantadas por meio de ensaios de flexão rotativa. A vida útil em fadiga dos dois materiais foi relacionada com as suas características metalúrgicas. Quanto a resistência à fadiga, as amostras do ferro fundido nodular perlítico tiveram um melhor comportamento sob carregamento cíclico do que as amostras do ferro fundido nodular ferrítico. Tal comportamento superior foi atribuído a maior microdureza da matriz e a presença da estrutura olho-de-boi. Finalmente, as curvas experimentais tensão versus número de ciclos para a falha dos ferros fundidos nodulares ferrítico e perlítico foram modeladas pela equação de Coffin-Manson, que se mostrou eficiente no tratamento de dados experimentais da vida em fadiga de ambos os materiais.
The objective of the present work was to evaluate the fatigue life of two nodular cast irons with metallurgical modifications and resulting in ferritic and perlitic different classes of material. Initially, samples of both materials were cast in sand moulds adopting the standard Y-block geometry. In the sequence, tensile and fatigue specimens were machined from the ferritic and perlitic samples. After the tensile and hardness tests, the microstructure of the both materials were analyzed by qualitative and quantitative metallography, aiming to characterize their metallurgical aspects as content, distribution and class of graphite nodules, as well as the contents of the ferritic and perlitic matrix. Following the metallurgical characterization, rolating bend fatigue tests were performed in order to estabilish the stress-life curves of the ferritic and perlitic nodular cast irons. Regarding the fatigue resistance, the specimens machined from the perlitic nodular sample showed a longer fatigue life than that related to the ferritic nodular specimens. The longer fatigue life of the perlitic nodular specimens was associated with a higher microhardness of the perlitic matrix and the preserve of the bull`s-eye structure. Finally, the experimental stress-life curves of the ferritic and perlitic nodular cast irons were modeled adopting the Coffin-Manson law, which was considered efficient in fitting experimental fatigue life data of both materials.
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Gieseke, Brian G. "Observations on the fracture of hypoeutectic, high chromium white cast irons." Thesis, Georgia Institute of Technology, 1986. http://hdl.handle.net/1853/19967.
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Walker, Andrew Meredith. "Laser surface alloying of metallic substrates with carbon and silicon." Thesis, Imperial College London, 1986. http://hdl.handle.net/10044/1/38178.
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Stevenson, Anthony Nicholas James. "Wear and microstructure of weld-hardfacing deposits of high chromium white cast irons." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243064.
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Kamps, Timothy James Anthony. "Development of detection techniques for investigating scuffing mechanisms of automotive diesel cast irons." Thesis, University of Southampton, 2017. https://eprints.soton.ac.uk/420756/.
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Increasingly stringent environmental legislation has led automotive manufacturers to focus engine development on achieving greater fuel efficiency by friction reduction. Engine friction losses between 4 and 15 % are typical for diesel engines, with approximately 50 % occurring at the piston assembly. Viscous losses associated with shearing lubricant films may be reduced by using oil with a lower viscosity, however this also results in the contact surfaces being separated by thinner lubricant films, which makes them more susceptible to scuffing. Improving the scuffing resistance of engine materials requires a detailed understanding of the contact conditions that lead to scuffing. However this is a complicated process that is often characterised by a rapid progression and therefore it is difficult to detect accurately and repeatedly the onset of scuffing failure. This thesis explores the possibility of using deviations in the instantaneous friction force measured using a laboratory tribometer to assess whether the onset and progression of scuffing can be repeatedly determined for cast iron diesel cylinder liner materials. Two techniques were developed that assessed the deviation in spatially resolved friction signal as a function of stroke length as well asthe level of disorder in the instantaneous root mean squared friction force. This enabled transitions in scuffing behaviour to be assessed for a Grade 250 flake graphite and a designation 400‐15 nodular cast iron cylinder liner materials under lubricated reciprocating sliding at increasing contact pressure. The detection techniques allowed tests to be interrupted during scuffing transitions for the analysis of surfaces using a combination of profilometry, scanning electron microscopy, energy dispersive X‐ray spectroscopy and focused ion beam microscopy. The results showed that once sufficient energy was available for the sliding contact to degrade the lubricant, progression to mild scuffing occurred. This was characterised for Grade 250 cast iron by surface platelet formation and subsurface crack networks associated with the de‐cohesion of the flake graphite phase from the pearlitic matrix. Progression to severe scuffing was characterised by adhesive transfer and back transfer of these platelets resulting in catastrophic wear of the cast iron surface. Compared to flake graphite cast iron, nodular cast iron transitioned to mild scuffing at lower contact pressures, but exhibited an intermediate scuffing stage that prolonged the transition to severe scuffing. This was due to the formation of a comprehensive oxide film associated with the ferritic matrix, but also because the adhesive removal of material was associated with angular dross inclusions from the nodularisation process. The techniques were applied to a conformal ring liner geometry that exhibited velocity dependant friction behaviour and therefore the detection techniques were adapted to include contact potential and disorderly friction data to detect scuffing transitions. The failure mechanisms were confirmed to be similar to that observed for both line contact and fired engine scuffing tests and showed that these techniques could be used to repeatedly detect scuffing transitions within 18 % maximum absolute deviation. Recommendations for testing of future engine materials for scuffing resistance are discussed as well as potential areas of further research.
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Tadesse, Abel. "On the Volume Changes during the Solidification of Cast Irons and Peritectic Steels." Doctoral thesis, KTH, Metallernas gjutning, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-202558.
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This thesis work deals with the volume changes during the solidification of cast irons and peritectic steels. The volume changes in casting metals are related to the expansion and/or contraction of the molten metal during solidification. Often, different types of shrinkage, namely macro- and micro-shrinkage, affect the casting quality. In addition to that, exposure of the metal casting to higher contraction or expansion during the solidification might also be related to internal strain development in samples, which eventually leads to surface crack propagation in some types of steel alloys during continuous casting. In consequence, a deep understanding of the mechanisms and control of the solidification will improve casting quality and production. All of the experiments during the entire work were carried out on laboratory scale samples. Displacement changes during solidification were measured with the help of a Linear Variable Displacement Transformer (LVDT). All of the LVDT experiments were performed on samples inside a sand mould. Simultaneously, the cooling curves of the respective samples during solidification were recorded with a thermocouple. By combining the displacement and cooling curves, the volume changes was evaluated and later used to explain the influence of inoculants, carbon and cooling rates on volume shrinkages of the casting. Hypoeutectic grey cast iron (GCI) and nodular cast iron (NCI) with hypo-, hyper- and eutectic carbon compositions were considered in the experiments from cast iron group. High nickel alloy steel (Sandvik Sanbar 64) was also used from peritectic steel type. These materials were melted inside an induction furnace and treated with different types of inoculants before and during pouring in order to modify the composition. Samples that were taken from the LVDT experiments were investigated using a number of different methods in order to support the observations from the displacement measurements: Differential Thermal Analysis (DTA), to evaluate the different phase present; Dilatometry, to see the effect of cooling rates on contraction for the various types of alloys; metallographic studies with optical microscopy; Backscattered electrons (BSE) analysis on SEM S-3700N, to investigate the different types of oxide and sulphide nuclei; and bulk density measurements by applying Archimedes' principle. Furthermore, the experimental volume expansion during solidification was compared with the theoretically calculated values for GCI and NCI. It was found that the casting shows hardly any shrinkage during early solidification in GCI, but in the eutectic region the casting expands until the end of solidification. The measured and the calculated volume changes are close to one another, but the former shows more expansion. The addition of MBZCAS (Si, Ca, Zr, Ba, Mn and Al) promotes more flake graphite, and ASSC (Si, Ca, Sr and Al) does not increase the number of eutectic cells by much. In addition to that, it lowers the primary austenite fraction, promotes more eutectic growth and decreases undercooled graphite and secondary dendritic arm spacing (SDAS). As a result, the volume expansion changes in the eutectic region. The expansion during the eutectic growth increase with an increase in the inoculant weight percentage. At the same time, the eutectic cells become smaller and increase in number. The effect of the inoculant and the superheat temperature shows a variation in the degree of expansion/contraction and the cooling rates for the experiments. Effective inoculation tends to homogenize the eutectic structure, reducing the undercooled and interdendritic graphite throughout the structure. In NCI experiments, it was found that the samples showed no expansion in the transversal direction due to higher micro-shrinkages in the centre, whereas in the longitudinal direction the samples shows expansion until solidification was complete. The theoretical and measured volume changes agreed with each other. The austenite fraction and number of micro-shrinkage pores decreased with increase in carbon content. The nodule count and distribution changes with carbon content. The thermal contraction of NCI is not influenced by the variation in carbon content at lower cooling rates. The structural analysis and solidification simulation results for NCI show that the nodule size and count distribution along the cross-sections at various locations are different due to the variation in cooling rates and carbon concentration. Finer nodule graphite appears in the thinner sections and close to the mold walls. A coarser structure is distributed mostly in the last solidified location. The simulation result indicates that finer nodules are associated with higher cooling rate and a lower degree of microsegregation, whereas the coarser nodules are related to lower cooling rate and a higher degree of microsegregation. As a result, this structural variation influences the micro-shrinkage in different parts. The displacement change measurements show that the peritectic steel expands and/or contracts during the solidification. The primary austenite precipitation during the solidification in the metastable region is accompanied by gradual expansion on the casting sides. Primary δ-ferrite precipitation under stable phase diagram is complemented by a severe contraction during solidification. The microstructural analysis reveals that the only difference between the samples is grain refinement with Ti addition. Moreover, the severe contraction in solidification region might be the source for the crack formation due to strain development, and further theoretical analysis is required in the future to verify this observation.QC 20170228
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Kothari, Mitul Arvind. "Welding of cast A359/SiC/10p metal matrix composites." Texas A&M University, 2005. http://hdl.handle.net/1969.1/2699.
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Welding of metal matrix composites (MMCs) is an alternative to their
mechanical joining, since they are difficult to machine. Published literature in fusion
welding of similar composites shows metallurgical problems. This study investigates the
weldability of A359/SiC/10p aluminum SiC MMC. Statistical experiments were
performed to identify the significant variables and their effects on the hardness, tensile
and bending strengths, ductility, and microstructure of the weld. Finite Element
Analysis (FEA) was used to predict the preheat temperature field across the weld and the
weld pool temperature.
Welding current, welding speed, and the preheat temperature (300-350??C)
affected the weld quality significantly. It was seen that the fracture of the welded
specimens was either in the base MMC or in the weld indicating a stronger interface
between the weld and the base MMC. Oxides formation was controlled along the weld
joint. Low heat inputs provided higher weld strengths and better weld integrity. It was
found that the weld strengths were approximately 85% of the parent material strength.
The weld region had higher extent of uniform mixing of base and filler metal when
welded at low currents and high welding speeds. These adequate thermal conditions
helped the SiC particles to stay in the central weld region. The interface reaction
between the matrix and SiC particles was hindered due to controlled heat inputs and
formation of harmful Al4C3 flakes was suppressed. The hardness values were found to
be slightly higher in the base metal rich region. There was no significant loss in the
hardness of the heat affected zone. The ductility of the weld was considerably increased
to 6.0-7.0% due to the addition of Al-Si filler metal.
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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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Sjögren, Torsten. "Influences of the graphite phase on elastic and plastic deformation behaviour of cast irons /." Jönköping : Linköping : Department of Mechanical Engineering, School of Engineering, Jönköping University ; Department of Management and Engineering, Linköping University, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-8776.
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Freeney, Timothy Alan. "Friction stir processing of cast magnesium alloys." Diss., Rolla, Mo. : University of Missouri-Rolla, 2007. http://scholarsmine.mst.edu/thesis/pdf/Freeney_09007dcc804a9022_3_09007dcc8055e79b.pdf.
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Thesis (M.S.)--University of Missouri--Rolla, 2007.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed June 17, 2008) Includes bibliographical references.
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Jacuinde, Arnoldo Bedolla. "The effect of silicon and mischmetal on the structure of high-chromium cast irons for wear resistance applications." Thesis, University of Sheffield, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391044.
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Ekström, Madeleine. "Oxidation and corrosion fatigue aspects of cast exhaust manifolds." Doctoral thesis, KTH, Mekanisk metallografi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-166274.
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Emission regulations for heavy-duty diesel engines are becoming increasingly restrictive to limit the environmental impacts of exhaust gases and particles. Increasing the specific power output of diesel engines would improve fuel efficiency and greatly reduce emissions, but these changes could lead to increased exhaust gas temperature, increasing demands on the exhaust manifold material. This is currently the ferritic ductile cast iron alloy SiMo51, containing about 4 wt% Si and ~1 wt% Mo, which operates close to its fatigue and oxidation resistance limits at peak temperature (750C). To ensure high durability at higher temperatures, three different approaches to improving the life of exhaust manifolds were developed in this thesis. The first approach was to modify SiMo51 by adding different combinations of Cr and Ni to improve its high-temperature strength and oxidation resistance, or by applying a thermal barrier coating (TBC) to reduce the material temperature and thereby improve fatigue life. In the second approach, new materials for engine components, e.g. austenitic ductile iron and cast stainless steel, were investigated for their high-temperature fatigue and oxidation properties. In order to identify the most suitable alloys for this application, in the third the environmental effects of the corrosive diesel exhaust gas on the fatigue life of SiMo51 were investigated. The high-temperature oxidation resistance of SiMo51 at 700 and 800C in air was found to be improved by adding Cr, whereas Ni showed adverse effects. The effects of solid-solution hardening from Ni and precipitation hardening from Cr were low at 700C, with improvements only at lower temperatures. Applying a TBC system, providing thermal protection from a ceramic topcoat and oxidation protection from a metallic bond coat, resulted in only small reductions in material temperature, but according to finite element calculations still effectively improved the fatigue life of a turbo manifold. Possible alternative materials to SiMo51 identified were austenitic cast ductile iron Ni-resistant D5S and austenitic cast stainless steel HK30, which provided high durability of exhaust manifolds up to 800 and 900C, respectively. Corrosion fatigue testing of SiMo51 at 700C in diesel exhaust gas demonstrated that the corrosive gas reduced fatigue life by 30-50% compared with air and by 60-75% compared with an inert environment. The reduced fatigue life was associated with a mechanism whereby the crack tip oxidized, followed by crack growth. Thus another potential benefit of TBC systems is that the bond coat may reduce oxidation interactions and further improve fatigue life. These results can be used for selecting materials for exhaust applications. They also reveal many new research questions for future studies. Combining the different approaches of alloy modification, new material testing and improving the performance using coatings widened the scope of how component life in exhaust manifolds can be improved. Moreover, the findings on environmental interactions on SiMo51 fatigue provide a completely new understanding of these processes in ductile irons, important knowledge when designing components exposed to corrosive environments. The novel facility developed for high-temperature corrosion fatigue testing can be useful to other researchers working in this field.QC 20150507
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Woodward, Neil J. "Pool oscillations and cast variations : penetration control for orbital tig welding of austenitic stainless steel tubing." Thesis, Cranfield University, 1997. http://dspace.lib.cranfield.ac.uk/handle/1826/4512.
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Pool oscillations in tungsten inert gas welding pools have been used in a closed-loop control system for orbital welding of ultra high purity tubing, determining a target level of penetration by altering the welding current in real-time. The technique is ideally suited to this application since it is does not contravene the cleanliness requirements for the inner bore and can be implemented outside the small orbital heads that are commonly used. The results presented in this thesis show how clear pool oscillation signals in extremely small molten pools can be monitored by optimising the welding conditions and signal processing of the arc voltage signal. As an indicator of the likely variation in cast behaviour present particularly in austenitic stainless steels, a 'time-to-penetrate' characterisation was made of the materials, using the time of the transition from the Mode 1 to the Mode 3 oscillation behaviour as the measured variable. By applying the test across a range of welding currents, significant insight was obtained into the cast and associated penetration behaviour. Late transitions indicated casts that exhibited significantly different responses to the more usually applied welding procedures, especially at the lower levels of welding current (highlighting their potentially more problematic penetration behaviour). It was shown that the established theoretical models were difficult to apply with certainty to moving weld pools, and consequently a fuzzy logic model was used in the control strategy. The closed-loop system comprised a user-interface PC, a control rack and commercial welding power source - control signals were applied every 2 to 3 Hz. Mode 3 pool oscillations were found to offer a more than satisfactory sensitivity to the inner bead width created for the various casts of 1.65 mm wall thickness materials studied.
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Theron, Maritha. "Quenching and tempering effects on Rheo-cast F357 aluminium alloy during Nd: YAG laser welding." Master's thesis, University of Cape Town, 2010. http://hdl.handle.net/11427/26148.
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Al-Si-Mg casting alloys are being used in automotive applications, aerospace applications and other applications requiring heat-treatable permanent mould castings that combine good weldability with high strength and toughness (ASM). These casting alloys are also known for their excellent castability, corrosion resistance and, in particular, .a range of mechanical properties in the heattreated condition. A357 aluminum alloy has been extensively used for semi-solid processing for more than three decades, and a large amount of components like fuel rails, engine mounts, engine brackets and suspension parts have been produced. This alloy is also included in the Statement for Work between the Council for Scientific and Industrial Research (CSIR) and Boeing Co, USA. F357, a hypo-eutectic aluminium alloy, Al-7%Si-0.6%Mg without beryllium, was processed with CSIR-Rheo technology to the Semi-Solid Metal (SSM) state and cast in plates with a 50 Ton High Pressure Die Casting machine. The castings were either left in the as-cast (F) condition or subjected to T4, T4+ or T6 heat treatments prior to laser welding. Welding of aluminium alloys poses many problems like porosity, loss of alloying elements, poor bead geometry and softening of the heat affected zone. Laser welding is however widely used in industrial production owing to the advantages such as low heat input, high welding speed and high production rate. Due to these unique advantages, the potential of autogenous Nd: Y AG laser welding as manufacturing process for this cast aluminium alloy was evaluated. A welding operating window was established and the optimum parameters were found to be a laser power of 3.8 kW at the workpiece and a welding speed of 4 m/min with a twin spot laser light configuration. These laser welding parameters were applied for the welding of the heat treated plates and resulted in very low weld joint porosity and almost no loss of alloying elements. The mechanical properties of age-hardenable Al-Si-Mg alloys are dependent on the rate at which the alloy is cooled after the solution heat treatment Because of the high cooling rate during laser welding, the possibility of producing weld seams through deep penetration laser welding, with mechanical properties matching those of the T6 temper condition, but without a post-weld solid solution heat treatment, was investigated. The quench rate after laser welding was measured and compared well with that measured after solution treatment. The resulting mechanical properties of F357 aluminium welded in the T4 condition and only artificially aged after welding (T4+ condition), compares very well with the T6 base material properties. The strengthening mechanisms obtained during laser welding and the different heat treatments were studied by means of transmission electron microscopy (TEM) and are consistent with the expected precipitation hardening processes in Al-Si-Mg alloys. The quench sensitivity of SSM F357 aluminium alloy is thus sufficiently low to obtain such an increase in strength values during laser welding, that no postweld solution heat treatment is necessary to achieve mechanical properties to the T6 performance specification.
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Christensen, Adam Baxter. "The Feasibility of Augmenting a Fixed-Gap Bobbin Friction Stir Welding Tool with Cutters to Join Enclosed Castings." BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/6846.
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Bobbin Friction Stir Welding (BFSW) is a new application of Friction Stir Welding (FSW) that can be used to join materials together with little to no axial forces. This eliminates the need of a backplate or anvil needed to apply counter pressure against the tool. The applications of BFSW are growing every day. This new technology is helping the automotive industry and many other industries join materials more effectively and efficiently. This technology can be used to join materials with high strength to weight ratios to make cars lighter to increase fuel efficiency. This will also greatly reduce the cost of current joining technologies.The purpose of this research is to prove the feasibility of augmenting a BFSW tool with cutters to join enclosed castings while simultaneously removing ribs and variations in thickness by (1) penetrating a BFSW tool into the material away from an edge; (2) removing any inconsistencies in the material thickness while maintaining a weld; and (3) removing a BFSW tool from the casting away from an edge leaving a clean exit hole without destroying either the casting or the tool.
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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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Rosemark, Brian P. "Friction stir processing parameters and property distributions in cast nickel aluminum bronze." Thesis, Monterey, Calif. : Naval Postgraduate School, 2006. http://bosun.nps.edu/uhtbin/hyperion.exe/06Dec%5FRosemark.pdf.
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Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, December 2006.Thesis Advisor(s): Terry R. McNelley, Srinivasan Swaminathan. "December 2006." Includes bibliographical references (p. 49-50). Also available in print.
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Jday, Rawen. "Caractérisation microstructurale du graphite sphéroïdal formé lors de la solidification et à l'état solide." Thesis, Toulouse, INPT, 2017. http://www.theses.fr/2017INPT0077/document.
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Les fontes à graphite sphéroïdal sont aujourd’hui très largement utilisées en raison de leurs bonnes propriétés mécaniques. La forme sphéroïdale du graphite est obtenue le plus souvent par l’ajout de magnésium ou de cérium lors de l’élaboration des fontes. Le graphite sphéroïdal peut être obtenu par graphitisation à l'état solide des fontes totalement ou partiellement solidifiées dans le système métastable. L’objectif de ce travail est d’étudier l’effet du traitement de graphitisation à l’état solide sur la croissance du graphite nodulaire d’une fonte à paroi mince qui présente une structure truitée à l'état brut de coulée. Cette fonte a été étudiée par microscopie optique, microscopies électronique à balayage et en transmission, spectroscopie Raman et spectroscopie de perte d'énergie des électrons. Des traitements thermiques assurant une graphitisation totale et partielle pour décomposer la cémentite formée à la solidification en graphite et en austénite ont été réalisés. Les nodules deviennent plus nombreux et leur taille augmente en fonction du temps de graphitisation. La microstructure après traitement thermique est composée de nodules de graphite et de ferrite. La spectroscopie Raman a été utilisée pour caractériser les nodules de graphite d’échantillons ayant été entièrement graphitisés à différentes températures dans le domaine austénitique. L’analyse par spectroscopie Raman ne montre aucune différence significative entre les spectres Raman enregistrés sur le graphite formé lors de la solidification et à l’état solide. Les caractérisations microstructurales par microscopie électronique en transmission montrent que le graphite à l’état brut de coulée présente une structure caractérisée par une zone interne où le graphite est désorienté. Une déformation mécanique due à la contraction lors de la solidification métastable induit la formation de cette zone. Cette zone disparaît par recristallisation après traitement de graphitisation totale pour former à la fin des secteurs coniques rayonnant à partir du germe et se développant vers la périphérie. Les résultats de ces travaux ont permis une meilleure compréhension de la structure de graphite nodulaire à l’état solide et montre aussi que le mécanisme de croissance du graphite nodulaire est le même lors de la solidification et de la transformation à l'état solideSpheroidal graphite iron castings are today widely used because of their good mechanical properties. The spheroidal shape of graphite is most often obtained by the addition of magnesium or cerium during the casting process. Spheroidal graphite can be formed at the solid-state by graphitization of cast irons which solidified partly or totally in the metastable system. The purpose of this work is to study the effect of solid-state graphitization treatment on the growth of nodular graphite of a thin wall casting which has a mottled structure at the as-cast state. This cast iron was studied using optical microscopy, scanning and transmission electron microscopy, Raman spectroscopy and electron energy loss spectroscopy. Heat treatments ensuring a total and partial graphitization to decompose the cementite formed at the solidification in graphite and austenite were realized. The nodules become more numerous and their size increases according to the time of graphitization. The microstructure after heat treatment is composed of graphite nodules and ferrite. Raman spectroscopy has been used to characterize graphite nodules in as-cast state and in samples having been fully graphitized at various temperatures in the austenite field. The results show no significant difference between Raman spectra recorded on these various samples, suggesting graphite grows with the same mechanism during either solidification or hightemperature (so-called first stage) graphitization. Transmission electron microscopy characterizations show that nodules in the as-cast material presents a multi-fold structure characterized by an inner zone where graphite is misoriented and an outer zone where it is well crystallized. In heat-treated samples, graphite nodules consist of well crystallized sectors radiating from the nucleus. These observations suggest that the misoriented zone appears because of mechanical deformation when the liquid contracts during its solidification. During heat-treatment, this zone disappears by recrystallization. The results of the present work lead to a better understanding of the nodular graphite structure in the solid state and also show that nodular graphite growth mechanism is the same during solidification and solid-state transformation
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Chenelle, Brendan F. "Friction Stir Welding in Wrought and Cast Aluminum Alloys: Microstructure, Residual Stress, Fatigue Crack Growth Mechanisms, and Novel Applications." Digital WPI, 2011. https://digitalcommons.wpi.edu/etd-theses/1215.
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Friction Stir Welding (FSW) is a new solid-state welding process that shows great promise for use in the aerospace and transportation industries. One of the primary benefits of this process is that mechanical properties of the base material are not as severely degraded as they are with conventional fusion welding. However, fatigue crack initiation and growth properties of the resulting weld nugget are not fully understood at this time. The primary goal of this project is to characterize the fatigue crack growth properties of friction stir welds in 6061-T6 aluminum as relates to the microstructural evolution of the weld. This was accomplished by producing friction stir welds and testing fatigue crack growth response in different crack orientations with respect to the weld. In addition, residual stress measurements were conducted for all cases, using both the crack compliance and contour methods. The results from the methods were compared in order to evaluate the accuracy of each method. Being an immature technology, the potential for discovery of new applications for the FSW process exist. With this in mind, novel applications of the FSW process, including the addition of particles during welding were explored. The first step was the investigation of property changes that occur when secondary cast phases are refined using the FSW process. The FSW process successfully refined all secondary phases in A380 and A356, producing an increase in hardness. Next, methods for the creation of particle metal matrix composites using FSW will be investigated. Nano-scale alumina particles were successfully added to the matrix and homogenously distributed. Using multiple weld passes through the composite was found to increase the uniformity of particle distribution. However, the alumina particle composite failed to provide any statistically significant hardness increase over the base material. The FSW process was also evaluated for weldability of traditionally difficult alloy systems. FSW was found to show very good weldability for dissimilar cast and wrought alloys, as well as for high-pressure die castings. Lastly, the feasibility of friction stir welding/processing in repairing crack defects in complex structural members in combination with cold-spray technology was determined. Friction Stir processing was used on a cold spray 6061-T6 block, resulting in significant increases in hardness over the base material, as well as a reduction in porosity. In addition, FSP was shown to eliminate crack-type defects in cold spray materials, a finding that has important applications in part repair. The deliverables of this work include an understanding of the fatigue crack growth response of FSW/FSP 6061-T6, as well as a feasibility study exploring novel uses for the FSW/FSP process. In addition, the deliverables include CNC code, fixtures, procedures, and analytical code for the creation and analysis of FSW/FSP joints. This will be important for the continuation of FSW/FSP work at WPI.
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Bergstedt, Edwin. "A Study in How Welding Parameters Affect the Porosity in Laser Welded High Pressure Die Cast AM50 Magnesium Alloy." Thesis, KTH, Materialvetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-291119.
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There are a need for reducing the weight of vehicles, one solution is to implement cast lightweight materials such as the high pressure die cast AM50 magnesium alloy. The weldability of this cast alloy is poor and to implement the use of the alloy commercially a welding process is needed that limits the porosity of the weld. The aim of this thesis is to study the effect of the welding parameters on the porosity in the weld, for three laser welding methods. The welding methods examined are single spot and twin spot laser using either a beam splitter or separate optics. The microstructure of the base material are also examined in order to evaluate relations between the components of the microstructure and the porosity in the weld. It was concluded that the hydrogen in the base material was the main reason for the observed porosity in the weld and that the material contains high pressure gas. The welding parameters did not influence the porosity for the single beam laser process, however, for the dual beam processes the welding parameters could affect the amount of pores. It was found that a double weld reduced the amount of pores and that the size and distribution of the secondary phase particles would benefit from the treatment. The cleaning of the samples prior to welding increased the porosity, however, non-cleaned samples contained more oxide inclusions. The results indicate that a twin beam process could reduce the porosity in the weld of the AM50 alloy.Det finns ett behov av att reducera vikten på fordon, en lösning är att implementera gjutna lätta material såsom formsprutad AM50-magnesiumlegering. Svetsbarheten hos denna gjutna legering är dålig och för att kommersiellt kunna använda legeringen krävs en svetsprocess som begränsar svetsens porositet. Syftet med detta examensarbete är att studera svetsparametrarnas effekt på svetsens porositet för tre lasersvetsmetoder. De svetsmetoder som undersöks är enkelpunkts och dubbelpunktslaser där antingen en stråldelare eller separat optik använts. Basmaterialets mikrostruktur undersöks också för att utvärdera sambandet mellan mikrostrukturen och porositeten i svetsen. Man drog slutsatsen att väte i basmaterialet var huvudorsaken till den observerade porositeten i svetsen och att materialet innehåller gas under högt tryck. De undersökta svetsparametrarna påverkade inte porositeten för processen med en laserstråle, men för dubbelstråleprocesserna kan svetsparametrarna påverka mängden porer. Det visade sig att en svets utförd med två strålar minskade mängden porer och att storleken och fördelningen av sekundärfaspartiklarna gynnas av behandlingen. Prover som rengjordes före svetsning hade ökad porositet, men icke-rengjorda prover innehöll mer oxidinneslutningar. Resultaten indikerar att en dubbelstråleprocess kan minska porositeten då AM50-legeringen lasersvetsas.
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Azevedo, dos Anjos Vitor Emanuel [Verfasser], and Rüdiger [Akademischer Betreuer] Deike. "Use of Thermal Analysis to Control the Solidification Morphology of Nodular Cast Irons and Reduce Feeding Needs / Vitor Emanuel Azevedo dos Anjos. Betreuer: Rüdiger Deike." Duisburg, 2015. http://d-nb.info/1076006353/34.
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Mariani, Fábio Edson. "Tratamentos térmicos e termoquímicos de boroaustêmpera em ferros fundidos nodulares e caracterização dos produtos resultantes." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/18/18158/tde-05092014-082721/.
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Amostras de ferros fundidos nodulares ligados com Cu, Cu-Ni ou Cu-Ni-Mo foram austemperadas, boretadas e boroaustemperadas e caracterizadas quanto à dureza e o comportamento ao desgaste microadesivo, tendo sido também estudada a cinética de formação da camada. O método de boretação utilizado foi via líquida em banho de bórax fundido, com tempos de permanência de 2 e 4 horas nas temperaturas de 850, 900 e 950ºC. Procedeu-se o tratamento direto de austêmpera, a partir dessa temperatura, em banhos de sal fundidos nas temperaturas de 240, 300 e 360ºC com tempos de permanência de 4 horas (boroaustêmpera). Realizou-se também, para fins de comparação, tratamento convencional de austêmpera. Microscopias óptica e eletrônica de varredura, EDS por raios-X, testes de dureza Brinell (substrato) e Vickers (revestimento) foram realizados, bem como ensaios de desgaste microadesivo do tipo esfera presa. A boretação resultou na formação de camadas de elevadas durezas, na faixa de 1300 a 1700 HV, e elevadas resistências ao desgaste. As resistências ao desgaste das amostras boretadas ou boroaustemperadas foram aumentadas em até 40x em relação às amostras brutas de fundição ou apenas austemperadas, indicando a grande eficácia do tratamento neste tipo de propriedade.Samples of ductile cast iron alloyed with Cu, Cu-Ni or Cu-Ni-Mo were austempered, borided and boroaustempered and afterwards characterized for hardness and micro-adhesive wear behavior. The kinetics of layer formation were also studied. The boriding method used was liquid molten borax bath, in periods of 2 and 4 hours at temperatures of 850, 900 and 950°C. The direct austempering treatment was performed from the borax bath temperature using molten salt baths at temperatures of 240, 300 and 360°C for 4 hours (boroaustempered). For comparative purposes, the conventional austempering treatment was also conducted. Optical microscopy, scanning electron microscopy, EDX, Brinell hardness measurements (substrate) and Vickers (coating) were performed, as were the tests for micro-adhesive wear. The boriding treatment resulted in the formation of layers with high hardness, in the range of 1300 to 1700 HV and high wear resistance. The wear resistance of borided or boroaustempered samples were increased by 40 times when compared to cast irons or austempered samples, indicating the high efficiency of this type of treatment in increasing the wear resistance of this material.
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Stachovec, Ivo. "Vliv cementových forem na strukturu odlitků z litiny LKG." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2009. http://www.nusl.cz/ntk/nusl-228809.
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The object of the diploma thesis was to solve and to describe the influence of cement sands moulds on the structure of castings with cast iron LKG. The work was intent on watching the tendency of cement sands to the metal penetration of castings, rising of the compounds on the metal mould interface and liquid metal and accompanies elements on the shape of the graphite in the surface of casting. The study of this processes has a big theoretical and a practical meaning, for prevent and prediction of rising of the defects that are attached with unsuitable choice of sand.
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Przybylowicz, Eric Thomas. "Weldability Evaluation of High-Cr Ni-Base Filler Metals using the Cast Pin Tear Test." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1429792705.
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Theuwissen, Koenraad. "Etude de l'influence des impuretés et des éléments à l'état de traces sur les mécanismes de croissance du graphite dans les fontes." Thesis, Toulouse, INPT, 2013. http://www.theses.fr/2013INPT0074/document.
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Les fontes de fer sont des alliages eutectiques de fonderie dont la structure consiste en des précipités de graphite dans une matrice riche en fer. Les propriétés mécaniques de ces alliages peuvent être grandement modifiées en agissant sur la matrice et sur la forme des précipités de graphite. Industriellement, les formes de graphite les plus courantes sont lamellaire et sphéroïdal, et l'on passe de l'une à l'autre par un traitement de sphéroïdisation (ajout de 0,02-0,05% massique de cérium ou de magnésium). D'autres morphologies peuvent apparaître en fonction des conditions de refroidissement et de la composition chimique de la fonte liquide. De fait, de très nombreux éléments d'alliage ou à l'état de traces peuvent diminuer l'efficacité du traitement de sphéroïdisation et modifier la forme du graphite. L'objectif de cette étude a été double, d'une part caractériser la structure fine de différentes formes de graphite, d'autre part réaliser des expériences de laboratoire destinées à étudier l'effet de quelques éléments, O, Ce et Sb, sur la croissance du graphite primaire. Dans cette étude, différents types de graphite (sphéroïdal, lamellaire et morcelé) issus de fontes commerciales ont été étudiés par microscopie optique, microscopies électroniques à balayage et en transmission, et spectrométrie de masse des ions secondaires. Leur caractérisation a permis de mettre en évidence certaines similitudes à l'échelle nanométrique malgré les différences de morphologies à l'échelle micrométrique. Des expériences consistant à fondre du fer pur dans des creusets de graphite, avec ou sans ajout délibéré d’antimoine ou de cérium, ont été réalisées. Les échantillons ont été élaborés par chauffage soit sous air soit sous vide primaire, puis refroidis lentement et maintenus au dessus de la température eutectique afin de faire croître de gros précipités de graphite primaire, et enfin rapidement pour figer en une structure fine le liquide résiduel. Les différentes formes de graphite obtenues lors de ces expériences ont fait l'objet des mêmes analyses métallographiques que les fontes industrielles. L’antimoine a favorisé la formation de lamelles de graphite incurvées. Les courbures de ces lamelles ont lieu par des changements dans leur direction de croissance. Le cérium a produit du graphite sous forme de plaquettes courtes et épaisses dans les échantillons élaborés sous air et du graphite sphéroïdal ou explosé dans les échantillons élaborés sous vide. Ainsi, l’un des rôles de cet élément est de désoxyder la fonte, ce qui a été confirmé par l’observation de différents oxydes de cérium dans les échantillons. L’observation de morphologies de graphite particulières dans ces échantillons suggère que le rôle du cérium ne se limite pas à la désoxydation de la fonte et des mécanismes d’action de ces éléments ont été discutés. Les caractérisations microstructurales, et en particulier la microscopie électronique en transmission, montrent que le graphite peut s’adapter à différentes conditions de croissance et adopter diverses morphologies dans les fontes. Les résultats de ces travaux ont permis une meilleure compréhension de l’effet des éléments d’addition sur la croissance du graphite et un modèle de croissance permettant de décrire les observations a été proposéCast irons are eutectic foundry alloys with a structure consisting of graphite precipitates within an iron-rich matrix. The mechanical properties of these alloys can be modified by changing the nature of the matrix and the shape of the graphite precipitates. The most usual graphite shapes are lamellar and spheroidal, this modification being achieved through a spheroidisation treatment (adding 0.02-0.05 wt% of cerium or magnesium). Other morphologies can occur depending on the chemical composition of the melt and its cooling conditions. Numerous alloying elements present as traces can reduce the effectiveness of the spheroidisation treatment and modify the shape of graphite. The objectives of this study were to characterize the structure of different graphite types at a fine scale and to carry out laboratory experiments to study the effect of certain elements (oxygen, cerium and antimony) on primary graphite growth. In the present work, various types of graphite found in commercial cast irons were studied using optical microscopy, secondary ion mass spectrometry, scanning and transmission electron microscopy. Characterization of spheroidal, lamellar and chunky graphite was performed in order to reveal their structural features. Even though these precipitates seem very different at lower magnification the results of this investigation emphasize on similarities found between them. Experiments consisting in melting pure iron in graphite crucibles, with or without antimony or cerium additions were carried out. The samples were heated in air or primary vacuum, then slowly cooled and held above the eutectic temperature so as to produce large primary graphite crystals, and finally quenched to produce a fine structure from the remaining liquid. The different graphite morphologies obtained in these experiments underwent the same metallographic analyses as the commercial irons. Antimony favoured the development of curved graphite flakes by promoting frequent changes in the flakes’ growth direction. Cerium produced thick graphite platelets in the samples prepared in air and exploded graphite in the samples prepared in vacuum. One of the main roles of this element is thus to deoxidize the melt, which was confirmed by the presence of several cerium oxides in the samples. Peculiar graphite morphologies were observed in these samples, suggesting that the role of cerium is not limited to deoxidizing the iron and the mechanisms by which this element affects graphite growth were discussed. The microstructural characterizations and mainly transmission electron microscopy show that graphite can adapt to different growth conditions and adopt diverse morpholgies in cast irons. The results of the present work lead to a better understanding of the effect of elements on graphite growth and a model was proposed to describe the experimental observations
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Abramova, Elizaveta. "Výroba a vlastnosti litin typu SiMo." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2016. http://www.nusl.cz/ntk/nusl-254424.
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While using iron castings behind temperature of 500 oC namely at cyclic heat straining, degradation of structure and breaching iron castings. For this purpose introduce cast iron with content of Si and Mo. Focusing on improvement of SiMo51 for increased high-temmperature corrosion-and fatigue life in exhaust-gas temperatures up to 800 oC. Thesis set up survey types alloys, properties, and way of casting production.
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Evans, William Charles. "Advancements in Joining Armor Grade Steels." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1556816907125644.
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Penagos, Jose Jimmy. "Efeito do refinamento da microestrutura e da adição de nióbio na resistência ao desgaste abrasivo de ferros fundidos de alto cromo." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/3/3151/tde-25082016-082141/.
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Os Ferros Fundidos de Alto Cromo (FFAC), por apresentarem excelentes propriedades tribológicas, têm sido amplamente utilizados em aplicações específicas envolvendo elevadas perdas de material por abrasão, especialmente no setor da mineração. Entretanto, a demanda por materiais com maior resistência ao desgaste aumenta continuamente, sendo necessárias novas pesquisas nesta área. Portanto, o presente trabalho objetiva avaliar a utilização do nióbio para aumentar, ainda mais, a resistência à abrasão dos FFAC\'s. Por outro lado, quando o FFAC é utilizado na fabricação de peças com geometrias irregulares (por exemplo, rotores de bombas), o componente pode apresentar diferentes níveis de refinamento da microestrutura, entre as regiões finas e espessas, devido às variações na taxa de resfriamento. No presente trabalho foi avaliado, o efeito do grau de refinamento da microestrutura, e a interação do refinamento com a adição de nióbio, na resistência ao desgaste abrasivo dos FFAC\'s. Para tanto, foram desenvolvidos quatro estudos principais: no primeiro estudo foram fabricados blocos de FFAC variando o grau de refinamento da microestrutura e foi mostrado que: grandes incrementos no grau de refinamento resultam em maiores perdas de massa por abrasão. Nas microestruturas menos refinadas, os carbonetos de cromo M7C3, de maior tamanho, são menos susceptíveis ao micro trincamento e podem, ocasionalmente, atuar como barreiras ante os eventos abrasivos. Em uma segunda série de experimentos, foi avaliada a interação do efeito do grau de refinamento da microestrutura com a adição de nióbio em teores baixos (1 %); mostrando que, para microestruturas com alto grau de refinamento, adições de nióbio reduzem as perdas de massa por abrasão em até 50 %. Em uma terceira série de experimentos foi avaliada a interação dos efeitos da adição de nióbio e de molibdênio. Quando comparado com a liga isenta de molibdênio, adições simultâneas de nióbio e molibdênio resultaram em microestruturas mais refinadas, com maior microdureza da matriz, e com carbonetos de nióbio (NbC) de maior dureza. Para condições de desgaste abrasivo por baixos esforços, onde o desgaste foi mais acentuado na matriz, adições simultâneas de nióbio e molibdênio resultaram em aumentos da resistência á abrasão dos FFAC estudados. Na última etapa do trabalho foi adicionado 3 % de nióbio em um liga de FFAC com composição química inicial hipereutética (25%Cr/3%C), a qual apresentaria carbonetos primários de cromo M7C3 de grande tamanho que induziriam comportamento frágil do material quando exposto ao desgaste. Porém, a adição de nióbio resultou em um FFAC com microestrutura mais refinada (eutética), contendo NbC\'s compactos e por conseguinte, mais resistente ao desgaste abrasivo.High Chromium Cast Irons (HCCI\'s), because of their excellent tribological properties, have been widely used for specific applications involving high wear rates by abrasion, especially in the mining sector. However, the demand for materials with higher wear resistance is continuously growing and thus further research is needed in this area. For that reason, the current work purposes to assess the use of niobium to further increase the wear resistance of HCCI\'s. On the other hand, when HCCI is used for manufacturing components with irregular geometries (e.g. pump impellers), the components thin and thick regions can contain different levels of structure refinement due to variation in their cooling rates. In this work, the effect of structure refinement and the interaction between structure refinement and niobium addition on the abrasion resistance of HCCI\'s were evaluated. For that purpose, four systematic main studies were developed: in the first study, blocks of HCCI were manufactured varying the structure refinement and it was shown that large increases in the degree of structure refinement result in higher wear mass losses by abrasion. In less refined microstructures, the larger M7C3 chromium carbides are less susceptible to microcracking and can occasionally act as a barrier to abrasive particles. In the second series of experiments, the interaction between structure refinement and niobium addition in low concentrations (1 %) was evaluated; showing that for more refined microstructures, niobium additions reduce the mass losses by abrasion up to 50 %. In the third series of experiments, the interaction between niobium and molybdenum additions was evaluated. Compared to molybdenum-free alloy, simultaneous additions of niobium and molybdenum resulted in a more refined microstructure, higher hardness of the matrix and harder niobium carbides (NbC). For Low Stress Sliding Abrasion (LSSA) wear configuration, where wear was more pronounced in the matrix, simultaneous addition of niobium and molybdenum resulted in increase of abrasion resistance in the studied HCCI. In the last stage of this work, 3 % of niobium were added in an HCCI alloy with hypereutectic initial chemical composition (25%Cr/3%C), which presents primary large sized chromium carbides that induce a brittle behavior of the HCCI when subjected to wear. However, the niobium addition resulted in a more refined microstructure (eutectic) HCCI containing compact-shaped NbC carbides, and consequently in more resistance to abrasive wear.
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Pilchak, Adam L. "The effect of friction stir processing on the microstructure, mechanical properties and fracture behavior of investment cast Ti-6Al-4V." Columbus, Ohio : Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view.cgi?acc%5Fnum=osu1243874522.
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Martin, Alexander Charles. "Initial Weldability of High Entropy Alloys for High Temperature Applications." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1555496040477991.
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Lenzo, Jansen C. Lenzo. "Evaluation of the Effect of Tungsten and Boron Additions on the Microstructure and Solidification Cracking Susceptibility of Fe-Mn-C Filler Metals." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1470829433.
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CHEN, SHI-ZHONG, and 陳世忠. "Thermal shock resistance of cast irons." Thesis, 1989. http://ndltd.ncl.edu.tw/handle/63910672027819362611.
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Fang, Long-Yinn. "Effect of niobium in cast irons." 1990. http://catalog.hathitrust.org/api/volumes/oclc/23037549.html.
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Thesis (M.S.)--University of Wisconsin--Madison, 1990.Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 78-80).
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Suarez, Oscar Marcelo. "Thermal analysis and microstructure control of cast irons." 2000. http://www.library.wisc.edu/databases/connect/dissertations.html.
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Xu, Zheng-Xun, and 許正勳. "High strength high toughness compacted graphite cast irons." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/39388930598946325770.
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Rüthrich, Karsten. "Beitrag zur Entwicklung des Elektronenstrahl-Mehrspot/Mehrprozess-Schweißens von Gusseisen/Gusseisen- und Gusseisen/Stahl-Verbindungen ohne Schweißzusatzstoffe." Doctoral thesis, 2013. https://tubaf.qucosa.de/id/qucosa%3A22929.
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Ziel der Arbeit war die Entwicklung des Elektronenstrahl-Mehrspot/Mehrprozess-Schweißens für Gusseisen/Gusseisen- und Gusseisen/Stahl-Verbindungen ohne Schweißzusatzstoffe. Im Vergleich zum Einbad-Schweißen entsteht beim Mehrbad-Schweißen eine porenarme Schweißnaht, gleichzeitig senkt sich die Schweißnahthärte geringfügig ab. Dabei kann die Kaltrissbildung in der Schweißnaht für arteigene Gusseisen-Verbindungen nicht unterdrückt werden. Für Mischverbindungen ist der Strahlversatz der bestimmende Schweißparameter beim Mehrbad-Schweißen. Über diesen kann sowohl die chemische Zusammensetzung der Schweißnaht eingestellt als auch ohne Vorwärmen eine kaltrissfreie Schweißnaht für Gusseisen/Stahl-Verbindungen erzeugt werden. Für die prozessintegrierte Wärmebehandlung der Fügezone wurde ein neues EB-Thermofeld entwickelt. Durch den Thermofeldeinsatz konnte die Aufhärtung in der Schmelz- und Wärmeeinflusszone signifikant reduziert werden und die mechanischen Eigenschaften der Schweißverbindungen wurden deutlich verbessert.
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Kuo, Yu-Hao, and 郭育豪. "Mechanical Property Control of Heavy Section Ductile Cast Irons." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/nvq6mq.
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碩士國立臺灣大學
機械工程學研究所
105
The primary purposes of this research are two folds: (1) To investigate the effect of Ni on the mechanical properties (tensile strength, yield strength, elongation, hardness, and low-temperature impact value) and microstructures (nodularity, nodule counts and percent pearlite) of heavy-section ductile iron. Based on the experimental results, multiple regression analyses were performed to correlate the mechanical properties with chemical composition and microstructure. (2) To establish the optimal conditions for the production of ductile cast iron inserts for the storage of the spent nuclear fuels through alloy design and manufacturing process control. Furthermore, in this study, the microstructure that occurred in the castings were analyzed and schemes were proposed to eliminate those abnormities, aiming to conform with the specification of EN-GJS-400-15U (T.S.>370MPa, Y.S.>240MPa and El.>7%) for the ductile cast iron inserts. The results of the first part indicate that the addition of Ni to the ductile cast irons can enhance the mechanical properties, i.e., as tensile strength, yield strength, microhardnesses of both ferrite and pearlite phases. However, the effect is affected by other factors, such as the Si and Mn contents, the pearlite (or ferrite) percentage, and the nodule count. The multiple regression analyses were performed to correlate the impact value at various temperatures with the selected metallurgical parameters (percent Ni, percent pearlite, and nodule counts). The results show that the impact value increase with increasing Ni content, and decreasing the percent pearlite and nodule counts. Regarding the trial tests of the reduced-length small scale ductile cast iron inserts, the results of the first attempt fail to conform with the specification due to the presence of chunky graphite in the microstructure, which causes a significant drop in tensile properties. The presence of chunky graphite can be attributed to the excessive amount of Cerium (Ce), especially in heavy section castings. To counteract the adverse effect of Ce, an appropriate amount of antimony (Sb) was added in the second trial. The results of the second trial of the reduced-length small scale ductile cast iron insert can meet the requirement of the specification. Finally, the reduced-length ductile cast iron insert was poured based upon the optimal casting conditions obtained from the first two trials for the reduced-length small scale ductile cast iron inserts. Again, the results fulfill the specification. In addition, the quality indices of all the specimens obtained from the three ductile cast iron inserts, together with the standard grades ductile cast iron, were calculated and compared. The comparisons in quality index can serve as basis for the evaluation of casting performance.
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Metzloff, Kyle E. "The elastic behavior of ductile and compacted graphite cast irons." 2001. http://www.library.wisc.edu/databases/connect/dissertations.html.
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Arvedson, Mark P. "The effects of tinned steel scrap in gray cast irons." 1995. http://catalog.hathitrust.org/api/volumes/oclc/34067461.html.
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Thesis (M.S.)--University of Wisconsin--Madison, 1995.Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 24-25).
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Javaid, Amjad. "Structure and property control of heavy section ductile cast irons." 1994. http://catalog.hathitrust.org/api/volumes/oclc/32033639.html.
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Thesis (Ph. D.)--University of Wisconsin--Madison, 1994.Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 168-172).
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Liu, Shengli. "Recarburisers and graphitic inoculants for ray and uctile cast irons." 1992. http://catalog.hathitrust.org/api/volumes/oclc/29968026.html.
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Thesis (Ph. D.)--University of Wisconsin--Madison, 1992.Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 222-226).
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Liu, Zong-Pei, and 劉宗霈. "Thermal Dimensional Stability of Low Thermal Expansion Ductile Cast Irons." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/01144556435646396570.
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碩士國立臺灣大學
機械工程學研究所
102
The objectives of this study are threefold: (1) To investigate the effect of homogenization heat treatment on both the degree of Ni segregation and the content of dissolved carbon in the matrix of the low thermal expansion ductile cast irons, and then to analyze the influence of compositional factor on α value; (2) To study the effects of alloy composition and homogenization heat treatment on the dimensional and shape changes of the test specimens by means of constrained thermal cyclic fatigue tests (30~200℃); (3) The temperature distribution and the thermal stress field in the test specimens after the constrained thermal cyclic fatigue tests were analyzed first by both calculation and simulation (ANSYS), and then the dimensional and shape changes of the alloys studied (Alloy D-5, Regular ductile iron and 304 stainless steel) were calculated and compared with the measured data. In addition, the correlations among α value, thermal stress and dimensional change were evaluated. The experimental results indicate that the degree of Ni segregation can be reduced by increasing the homogenization heat treatment temperature and/or time, rendering a decrease in α value. On the other hand, the dissolved C content in the matrix showed little affected by homogenization heat treatment, regardless of the fact that increasing both heat treatment temperature and time will increase the dissolved C content. Among the various heat treatment procedures employed, heat treatment T4(1150℃/4hr/FC/750℃/4hr) not only can effectively eliminate the Ni segregation, but also can reduce the C concentration in the matrix, resulting in a very low α value of around (2-3)×10-6/℃. Furthermore, regression equations were derived to correlate the degree of Ni segregation and dissolved C content with α value, as expressed below: Heat A (35%Ni): Heat B (30%Ni + 5%Co): Heats A &; B: It is clear from the above equations that in order to achieve a low α value, both the degree of Ni segregation and the dissolved C content should decrease. Constrained thermal cyclic fatigue tests (30~200℃) were performed to compare the dimensional and shape changes among the low thermal expansion ductile cast irons with different homogenization heat treatment procedures, and also among three different alloys studied herein, namely, Alloy D-5, Regular ductile iron and 304 stainless steel. The extent of distortion or shape change of the test specimens (&;#8710;PV) was used as a criterion to evaluate the dimensional stability of the alloys investigated. The effect of homogenization heat treatment on &;#8710;PV can be expressed by the following order: Heat A (35%Ni): T0(338.51μm)>T1(301.82μm)>T2(237.95μm)>T3(190.70μm)>T4(61.24μm) Heat B (30%Ni + 5%Co): T0(286.24μm)>T1(252.64μm)>T2(189.44μm)>T3(125.46μm)>T4(48.23μm) It is clear from the above results that Alloy A with heat treatment T4 (1150℃/4hr/FC/750℃/4hr) exhibits the lowest shape change (48.23μm), implying that an alloy with a lower α value can achieve a better dimensional stability. Finally, numerical simulation by finite element method (FEM) was employed to obtain the temperature distribution and thermal stress field for different alloys (D-5, regular SG and SUS304) after thermal cyclic fatigue tests. The results show that the values of temperature gradient follow the following order: SG>SUS304>D-5, while the order of the thermal stress is: SUS304>SG>D-5. Furthermore, regression analysis was performed to obtain the correlation between thermal stress and &;#8710;PV, with the results shown as follows: . It is obvious that the lower the thermal stress, the lower the &;#8710;PV value. In conclusion, low thermal expansion ductile iron with T4 heat treatment (1150℃/4hr/ FC/750℃/4hr/WQ) exhibits the best dimensional stability due to its lowest α value (1.72x10-6/℃).