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1
Boeri, Roberto Enrique. "The solidification of ductile cast iron." Thesis, University of British Columbia, 1989. http://hdl.handle.net/2429/30598.
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The microsegregation of Mn, Cu, Cr, Mo, Ni and Si has been measured in cast ductile iron and in ductile iron which has been quenched when partially solidified. Effective segregation coefficients have been determined for each of the elements, and used to calculate the segregation on the basis of the Scheil equation. The calculated values agree reasonably well with the values of the solute concentration as a function of the solid fraction measured in quenched samples.
The microstructure of the solid phases during the solidification of ductile iron has been observed. Solidification of eutectic ductile iron begins with the independent nucleation of austenite and graphite in the melt. Later the graphite nodules are enveloped by austenite, and further solidification takes place by the thickening of the austenite layers enveloping the graphite. Isolated pockets of interdendritic melt are the last material to solidify.
On the basis of the measured segregation of the different alloying elements, the mechanisms by which the segregation affects the microstructure are considered, and an explanation for the effect of segregation on the hardenability of ductile iron is proposed.
A mathematical model of the solidification of eutectic ductile iron is formulated which includes heat flow, nucleation and growth of graphite nodules, and the segregation of Si. The model uses equilibrium temperatures given by the ternary Fe-C-Si equilibrium diagram. Using the mathematical model, cooling curves, nodule
count and nodular size distribution are determined as a function of position in the casting sample. The results are compared to measured temperatures, nodule count and nodule size in rod castings of 12.5, 20 and 43mm radius. There is good agreement between the calculated and measured values for the 43mm radius rod, and not quite good agreement for the rods of smaller radii. The changes in solidification predicted by the model when some solidification parameters are varied are consistent with experimental observations with the same variation in the parameters.Applied Science, Faculty of
Materials Engineering, Department of
Graduate
2
Lukhi, Mehul. "Micromechanical Simulation of Fatigue in Nodular Cast Iron." Technische Universität Bergakademie Freiberg, 2020. https://tubaf.qucosa.de/id/qucosa%3A72791.
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In the present thesis, fatigue behavior of nodular cast iron (NCI) is investigated using micromechanical simulations. An elastic-plastic porous material experiences an increase in a void volume fraction with each cycle of loading. This is called void ratchetting. The hypothesis of this thesis is to explain the fatigue failure of NCI using void ratchetting mechanism. The strain-life, stress-life, notch support effect, and fatigue crack growth are studied using the micromechanical simulations. In all these studies, matrix material is defined as an elastic-plastic with isotropic/kinematic hardening. No damage law is used to define material degradation. The axisymmetric cell model is developed to study strain-life and stress-life approaches for fatigue. The cell model is subjected to cyclic loading and cycle by cycle simulations are carried out until failure. The failure of the cell model is defined based on the drop in the macroscopic response of the cell model. The notch support effect is investigated using a 2D plane strain model within stress-life concept. From the simulation results, strain-life and stress-life curves are extracted, and they are in qualitative and quantitative agreement with experimental data collected from literature. The fatigue crack growth is studied using a micromechanical cell model under small scale yielding conditions. The graphite particles are considered as voids, and they are resolved discretely in fracture process zone. The region outside of the fracture process zone is considered as a homogenized medium. When positive alternating loads are applied, ligaments in the fracture process zone show ratchetting behavior, which is responsible for an effective fatigue crack growth. This mechanism is relevant for the fatigue crack growth in NCI. The 2D plane strain boundary layer model is able to predict the effect of load ratio on threshold for the fatigue crack growth and the fatigue crack growth rate. The fatigue crack growth rate curves obtained from the simulations are compared with experimental data. It is essential to note that the void ratchetting (plastic collapse of the intervoid ligaments) is a crucial mechanism in NCI and more focus should be given to this mechanism as it is simple to implement and gives satisfying simulation results.
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MELLO, CARLOS ALBERTO TORRES DE. "FATIGUE LIFE OF A FERRITIC NODULAR CAST IRON OF DIFFERENT MICROSTRUCTURES." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2003. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=3721@1.
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Esta pesquisa teve como objetivos promover variações
microestruturais em um ferro fundido nodular ferrítico tipo
ASTM A536 60-40-18, pelo do uso de resfriadores durante a
solidificação do material e pela adoção de tratamentos
térmicos pós-fundição, bem como avaliar a influência de
tais variações microestruturais sobre as propriedades
mecânicas e vida em fadiga do material.
Inicialmente, amostras do material foram fundidas em areia
com e sem o uso de resfriadores. Após a fundição, algumas
amostras de ambas as condições de resfriamento sofreram
normalização, enquanto outras foram recozidas, perfazendo
seis diferentes condições microestruturais: sem resfriador
bruta de fundição (SRB); sem resfriador normalizada (SRN);
sem resfriador recozida (SRR); com resfriador bruta de
fundição (CRB); com resfriador normalizada (CRN) e com
resfriador recozida (CRR).
Em seqüência, corpos de prova de todas as condições
mencionadas acima foram ensaiados em tração e,
posteriormente, sofreram análises metalográficas
qualitativas e quantitativas. Dando continuação a etapa
experimental, levantaramse as curvas tensão versus número
de ciclos para a falha das condições microestruturais SRB,
SRR, CRB e CRR, por meio de ensaios de fadiga em flexão
rotativa. A vida em fadiga do material também foi
relacionada com às características metalúrgicas de cada
condição.The objectives of the present work were to promote microstructural variations in an ASTM A 536 60-40-18 ferritic nodular cast iron, making use of cast coolers during and adopting heat treatments after casting, as well as to evaluate the influence of the microstructural variations on the mechanical properties and fatigue life of the material. Initially, samples of the material were cast in sand moulds with and without internal coolers. After casting, a number of samples in both cooling conditions were subjected to normalizing and annealing heat treatments and, therefore, six different microstructural conditions were obtained: as- cast without cooler (SRB), normalized without cooler (SRN), annealed without cooler (SRR), as-cast with cooler (CRB), normalized with cooler (CRN) and annealed with cooler (CRR). Tensile test were carried out on specimens representing the above mentioned conditions and their microstructures were analysed by qualitative and quantitative metallography. In the sequence of the experimental procedure, rotating bend fadigue test were performed in order to establish the stress-life curves for the SRB, SRR, CRB and CRR microstructural conditions. The fadigue life of the material was also related to the metallurgical characteristics of each condition. The metallographic analysis has indicated that the use of coolers increases the number of graphite nodules, reduces the graphite nodule size and otimizes the spherical morphology. However, these microstructural modifications seam to have no significant influence on the mechanical properties of the material. As to the effect of normalizing annealing, boht treatments not imply in significant changes in the mechanical properties of the as-cast conditions. Regarding the fadigue resistance of the material in the as-cast conditions, the CRB sample showed a longer fatigue life than the SRB samples and this performance under cyclic loading was attributed to the fact that the CRB condition is characterized by a higher number of graphite nodules of class VI. A comparison between the as-cast and annealed conditions indicated that the microstructural conditions SRR and CRR presented a lower fatigue resistance than the conditions SRB and CRB, respectively. This behaviour was associated with the microstructural features of the as-cast conditions, namely the smaller graphite nodule size, the higher microhardness of the matrix and the presence of the bull`s-eye structure. Finally, the experimental stress-life curves were modelled by means of Coffin-Manson law, which was considered efficient in the fadigue life data of ferritic nodular cast iron.
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Björkblad, Anders. "Fatigue Assessment of Cast Components : Influence of Cast Defects." Doctoral thesis, KTH, Lättkonstruktioner, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-9133.
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This thesis is on the fatigue assessment of cast components with special attention to defects. The primary material in view is nodular cast iron, but also cast steel is considered. However, the fatigue behaviour is in principle valid for general use on other cast metals.The first two papers is about general cast material behaviour in fatigue loading. The materials considered are a high strength alloyed cast steel and a medium strength nodular cast iron. It is concluded that cast defects is the main fatigue initiation cause and it is only in exception that the fatigue life is not ruled by fracture mechanics. The third paper is a fracture mechanics evaluation of a nodular iron cast sleeve. The analysis of the component is based on crack initiation from cast defects and low-cycle fatigue. Fracture mechanics material parameters for Paris law, c and m, are extracted for the materials considered. In paper D design quality rules for nodular cast iron based on the Swedish standard SS 11 40 60 is presented. The quality rules regard cast defects in fatigue assessments and facilitate defect-based component design. In paper E, a finite element tool that is capable to predict and calculate 3D crack propagation for embedded cracks and defects is presented. The tool is an add-on for ANSYS finite element program. In paper F, closure equations for nodular cast iron are proposed in parallel to refined fracture mechanics material data. The paper includes crack propagation at different load ratios and in different microstructures.Summarized, the thesis composes a further development of the fatigue assessment of cast components. The central role of defects in fatigue is clarified and tools are provided for fracture mechanics evaluations of defects as well as for defect based design. The quality rules are also fit for application in manufacturing and for acceptance tests, hence covering the span from design to complete product.QC 20100712
Gjutdesign
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Andrade, Ricardo Batista de. "Parametros termicos e estruturais em ferros fundidos cinzento e nodular solidificados em moldes de areia e unidirecionalmente." [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265196.
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Orientador: Rezende Gomes dos SantosTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
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Resumo: No presente trabalho a solidificação unidirecional em regime transiente de um ferro fundido cinzento com composição hipoeutética e de um ferro fundido nodular de composição eutética são aplicadas para analisar a influência dos parâmetros do processo no número de veios ou nódulos de grafita. Para efeito de comparação foram fundidas algumas amostras em moldes de areia convencionais. Os resultados experimentais das variações de temperatura durante a solidificação foram utilizados para estimar as variações dos parâmetros de solidificação. As curvas de variação do número de veios e nódulos por unidade de área com a velocidade de solidificação e a taxa de resfriamento indicaram que os números de veios e nódulos decrescem e suas dimensões aumentam com a queda desses parâmetros. Os resultados mostraram também que para posições longe da interface metal/molde na solidificação unidirecional os números de veios ou nódulos se aproximam dos obtidos em moldes de areia, portanto obteve-se a influência dos parâmetros de solidificação na microestrutura para praticamente todos os processamentos utilizados na prática de fundição destas ligas. Algumas medidas de variação de dureza com a distância da interface metal/molde foram realizadas, indicando que para o ferro fundido cinzento a dureza diminui e para o ferro fundido nodular aumenta com a diminuição da velocidade de solidificação.
Abstract: In the present work unsteady state unidirectional solidification of a hypoeutectic gray cast iron and of a eutectic ductile cast iron is applied to analyze the influence of the process parameters an the flake and nodule count. For comparison purpose some samples were cast in sand molds. The experimental results of temperature variation in the casting were used to estimate the variations of solidification parameters. From the results curves relating flake and nodule count and solidification rate and flake and nodule count and cooling rate were obtained indicating that the number nodule decreases and their dimensions increase as these parameters decreases. From the results obtained relations were established between these parameters. The results showed that nodule count observed for unidirectional solidification far from metal/mold interface approaches to the observed in sand mold, permitting to' analyze the influence solidification parameters an the microstructure formation far almost all foundry processes of these alloys. Some measurements of hardness variations from metal/mold interface were carried out indicating that far gray cast iron hardness decreases and for ductile iron increases as solidification rate decreases.
Doutorado
Materiais e Processos de Fabricação
Doutor em Engenharia Mecânica
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Maluf, Omar. ""Influência do roleteamento no comportamento em fadiga de um ferro fundido nodular perlítico"." Universidade de São Paulo, 2002. http://www.teses.usp.br/teses/disponiveis/88/88131/tde-17032004-163144/.
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O processo de roleteamento é um tratamento superficial, comumente utilizado em peças fabricadas em aços e ferros fundidos nodulares, em regiões onde há concentradores de tensões, com o intuito de melhorar as propriedades de resistência à fadiga. Este processo endurece e introduz tensões residuais compressivas na camada superficial do material, através de deformação controlada, provocando uma redução das tensões de tração que atuam na superfície da peça submetida a carregamentos cíclicos. Este trabalho teve como principal objetivo o estudo do efeito do roleteamento superficial sobre o comportamento em fadiga de um ferro fundido nodular de matriz perlítica, utilizado na fabricação de virabrequins pela indústria automobilística. Foram realizados ensaios de fadiga por flexão rotativa em corpos de prova lisos e com entalhe. Os corpos de prova com entalhe foram divididos em dois grupos, com e sem roleteamento superficial. Foi utilizado entalhe com geometria semicircular com raio de 1,20mm e profundidade de 0,70mm. Para o processo de roleteamento foi utilizado um rolete com diâmetro de 15,00mm e com raio de curvatura de 1,30mm e aplicada uma força de compressão de 2390N. A introdução de tensões residuais compressivas pelo trabalho a frio, dificultou a nucleação e a propagação de trincas na camada superficial dos entalhes roleteados. Isto ficou evidenciado pelo aumento do valor do limite de fadiga para 483MPa obtido para o material entalhado e roleteado, enquanto que para o material nas condições de sem entalhe e somente entalhado estes valores foram de 300MPa e 168Mpa, respectivamente.Surface rolling is a mechanical treatment commonly used in parts fabricated with steel and ductile cast iron, specifically in stress concentration regions, to improve fatigue properties. This process hardens and introduces compressive residual stresses to the surface of the material through the application of controlled strains, thus provoking a reduction of resulting tensile stress at its surface under cyclic loading. This work deals with the effect of surface rolling on high cycle fatigue behavior of a pearlitic ductile cast iron used in crankshaft by automotive industries. Rotating bending fatigue tests were performed in both smooth and notched specimens. The notched specimens were divided into two groups: with and without surface rolling treatment. The specimens notch geometry was semicircular with radius of 1.20mm and depth of 0.70mm. The rolling treatment was carried out using a roller with diameter of 15,00mm, curvature radius of 1.30mm and a compression force of 2390N. The introduction of compressive residual stresses under cold work made difficult the nucleation and propagation of the crack on the rolled surface of the notch. It was confirmed by the increase of the endurance limit of the surface rolled specimens to 483MPa in comparison with the smooth and notched specimens, respectively, 300MPa and 168 MPa.
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Wollmann, Daniela. "Avaliação da resistência à fadiga de contato de ferro fundido nodular nitretado por plasma." Universidade Tecnológica Federal do Paraná, 2012. http://repositorio.utfpr.edu.br/jspui/handle/1/565.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), Fundação AraucáriaEste trabalho apresenta um estudo sobre a resistência à fadiga de contato de um ferro fundido nodular nitretado por plasma. Os experimentos foram realizados em um equipamento do tipo esfera sobre plano. Os corpos de prova foram usinados a partir de uma barra de ferro fundido nodular perlítico e em seguida temperados e revenidos. Após a preparação superficial por meio de retificação, lixamento e polimento, as amostras foram divididas em três grupos: 1) temperadas e revenidas; 2) temperadas, revenidos e nitretadas por plasma por 8 horas a 400 °C; e 3) mesmos parâmetros do grupo 2, porém submetidas a um tratamento adicional de Difusão em forno por 16 horas a 400 °C, visando aumentar a profundidade de camada endurecida e dissolver possíveis traços da formação de camada de compostos. Foram feitas medidas de dureza superficial, perfis de dureza, análises das fases e de tensões residuais por meio de difração de raios-X, rugosidade e microscopia eletrônica de varredura, para a caracterização das amostras em diferentes estágios do trabalho. Os ensaios de fadiga de contato foram realizados com lubrificação e a uma pressão de contato máxima de 3,6 GPa. Análises de Weibull mostraram uma vida em fadiga aproximadamente cinco vezes menor para os corpos de prova nitretados por plasma, com ou sem difusão, apesar destes apresentarem tensão residual compressiva significativamente superior aos temperados e revenidos. A menor vida em fadiga dos corpos de prova nitretados foi atribuída a menor dureza de substrato e a ocorrência de um mecanismo de falha distinto dos mecanismos clássicos de fadiga de contato de rolamento, demonstrado nas análises das superfícies ensaiadas.
This work presents a study on the contact fatigue resistance of a plasma nitrided ductile cast iron. The experiments were carried out using a ball-on-washer machine. Specimens were machined from a perlitic ductile cast iron bar, and then quenched and tempered. After surface grinding and polishing, the specimens were divided into three groups a) the first group was tested after the described process, which means as quenched and tempered; b) the second group was plasma nitridedat 400 °C for 8 hours; c) the third one was plasma nitrided as previously described and submitted to a diffusion process at 400 °C for 16 hours in order to extend the hardened zone and to dissolve any trace of compound layer within the microstructure. Surface hardness, hardness profiles, phase analyses and residual stress measurements by X-ray diffraction, surface roughness and optical and scanning electron microscopy were applied to characterize the surfaces during different stages of this work. Rolling contact fatigue tests were conducted at a maximum contact pressure of 3.6 GPa under flood lubrication. Weibull analysis showed that fatigue lives of plasma nitrided specimens were approximately five times shorter than those just quenched and tempered, even though the residual stress measurements showed significantly higher compressive stresses for the nitride conditions. The lower fatigue life for the plasma nitrided specimens was attributed to the lower matrix hardness and to a failure mechanism distinct from the classical rolling contact fatigue mechanisms, showed by surface analisis.
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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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Lukhi, Mehul [Verfasser], Meinhard [Akademischer Betreuer] Kuna, Meinhard [Gutachter] Kuna, and Sebastian [Gutachter] Münstermann. "Micromechanical Simulation of Fatigue in Nodular Cast Iron / Mehul Lukhi ; Gutachter: Meinhard Kuna, Sebastian Münstermann ; Betreuer: Meinhard Kuna." Freiberg : Technische Universität Bergakademie Freiberg, 2020. http://d-nb.info/1226110894/34.
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Rosário, John Ferney Alvarez. "Avaliação da integridade da superfície no torneamento de um ferro fundido nodular com carboneto." Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/3/3132/tde-05092006-131535/.
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Neste trabalho, estudou-se a integridade superficial durante o torneamento de um ferro fundido nodular com carbonetos, considerando a heterogeneidade microestrutural (fração volumétrica, tamanho e morfologia de grafita e dos carbonetos) e os efeitos dos parâmetros de corte (avanço, velocidade de corte e profundidade de corte), baseados num planejamento fatorial fracionário 24-1. Este texto apresenta, numa primeira parte, uma revisão baseada em referências bibliográficas clássicas da engenharia de superfícies, na tentativa de definir os conceitos que compõem a integridade da superfície. Posteriormente, descrevem-se os resultados de ensaios preliminares, realizados com a finalidade avaliar os níveis do processo e os efeitos desses parâmetros na integridade da superfície. Finalmente, realizaram-se os ensaios de usinagem em corpos-de-prova de ferro fundido nodular com carboneto, nos diâmetros de 80 mm e 140mm. Durante os ensaios de torneamento empregaram-se duas velocidades de corte (60 m/min e 180 m/min), dois avanços (0,1 mm/rev e 0,3 mm/rev) e duas profundidades de corte (0,2 mm e 0,3 mm). Após os ensaios de usinagem, foram realizadas: a avaliação das propriedades do material usinado (dureza e microestrutura), a análise de topografia da superfície usinada mediante avaliação da rugosidade, e a avaliação da influência dos parâmetros de usinagem na rugosidade. Encontrou-se uma dependência estatisticamente significativa da variação nas propriedades mecânicas dos corpos-de-prova em função da microestrutura, e mostraram-se os efeitos dessas variações em termos da integridade da superfície usinada.In this work, the surface integrity of a ductile cast iron with carbides was studied during turning operations, considering the microstructural heterogeneity (volume fraction, size and morphology of the graphite and carbides) and the effect of the machining parameters (feed, cutting speed and depth of cut), based on a fractional factorial design 24-1. This work presents, initially, a literature review based on classic works on surface engineering, as an attempt to define the main concepts of surface integrity. Later, the results of preliminary test are described, which were conducted in order to define the process levels and the effects of these levels on the surface integrity. Finally, turning tests were conducted on specimens of ductile iron with carbides, at diameters of 80 and 140 mm. Two cutting speeds (60 m/min and 180 m/min), two feeds (0,1 mm/rev and 0,3 mm/rev) and two depths of cut (0,2 mm and 0,3 mm) were selected during the tests. Machined specimens were analyzed in terms of the properties of the machined material (hardness and microstructure) and of the roughness of the machined surface. The effect of the machining parameters on the roughness was also studied. A statistically significant dependence was observed for the properties of the machined specimens as a function of the microstructure and the effect of these properties on the surface integrity is presented.
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Santos, Elder Gregol dos. "Avaliação da carburação de um ferro fundido nodular em fornos de indução de média frequência." Universidade do Estado de Santa Catarina, 2014. http://tede.udesc.br/handle/handle/1669.
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Previous issue date: 2014-11-07Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
The carburiser materials have been widely used in the foundry industry, motivated by increasing use of scrap steel and consequent reduction in the use of pig iron. Several factors, besides of recovery of carbon in the metal bath, can be associated with the use of carburisers, including the effect on the levels of silicon, sulfur, nitrogen and degree of nucleation of metal. This paper evaluates the effects of the use of carburisers materials, of the types natural graphite, synthetic graphite, graphite permanent mold residue (used in molds of continuous casting) and synthetic graphite with low sulphur amount. The method of addition was chosen on the surface of the liquid bath, at a medium frequency induction furnace, 2500 kg capacity, tests at three different temperatures. Was observed that there was no incorporation of nitrogen of carburisers to liquid metal, and the sulfur content was altered only when used synthetic carburiser. The increase in temperature caused an increase in the value of carburation efficiency, regardless of the type of carburisers. In general, it was observed an increase 21-32% when the temperature is changed from 1480 to 1545 ° C. Only the special synthetic carburisers showed lower sensitivity to temperature increase, showing an increase of only 5% efficiency. It was found that the ash content of the carburiser is a variable that affects significantly the dissolution process of the carburiser. The results showed that the carburisers with lower ash content, have higher carburation efficiency. This paper proposed the concept of rate of gain of associated carbon, which was effective for predicting the behavior of % C of liquid metal after the addition of the carburiser. It was found that the rate of gain associated initial carbon is favored with increasing temperature and the sulfur content of liquid metal, and impaired with an increase in the percentage of ash in carburiser. As for the value of the combined rate of dissolution, this showed an increase when the temperature of addition is growing. It was noted that the value of maximum rate of efficiency has relation with the value of the combined rate of dissolution, allowing to conclude that the higher the value of the combined dissolution rate, the faster the process reaches its maximum efficiency. The results observed for the residue of graphite mold, in the carburation efficiency, efficiency rate and combined rate of dissolution, showed that this material has the potential to be used as carburante in foudry. Comparing the initial and final conditions of the experiments, it was found that bath treated with synthetic carburiser with low% S, showed a reduction in the degree eutetic supercooling at temperatures of 1485 and 1545 ° C and the chill residue contributed to the reduction of degree eutetic supercooling at temperatures of 1485, 1515 and 1545 ° C. When analyzing the behavior of the degree eutetic supercooling with time after the addition of carburiser, was possible to identify three different behaviors.
Os materiais carburantes têm sido amplamente utilizados na indústria de fundição, em função da crescente utilização de sucata de aço e a consequente redução do uso de ferro gusa. Vários fatores, além da recuperação de carbono no banho metálico, podem ser associados ao uso dos carburantes, entre eles o efeito nos teores de sílicio, enxofre, nitrogênio e no grau de nucleação do metal. Este trabalho apresenta a avaliação dos efeitos do uso de materiais carburantes, dos tipos grafite natural, grafite sintético, resíduo de coquilha de grafite (utilizado em matrizes de fundição contínua) e grafite sintético com baixo teor de enxofre. O método de adição escolhido foi sobre a superfície do banho líquido, em um forno à indução de média frequência, de 2500 Kg de capacidade, realizando testes em três temperaturas distintas. Observou-se que não houve incorporação de nitrogênio do carburante pelo metal líquido, e o teor de enxofre sofreu alteração somente quando usado o carburante sintético. O aumento da temperatura provocou um aumento no valor da eficiência de carburação, independente do tipo de carburante. De maneira geral, observou-se um aumento de 21 32% na eficiência, quando a temperatura é alterada de 1480 a 1545°C. Apenas o carburante sintético especial apresentou menor sensibilidade ao aumento da temperatura, mostrando um aumento de apenas 5% de eficiência. Verificou-se que o teor de cinzas do carburante é uma variável que afeta significativamente o processo de dissolução do carburante. Os resultados evidenciaram que os carburantes com menor teor de cinzas, apresentam maiores valores de eficiência de carburação. Este trabalho propôs o conceito da taxa de ganho de carbono associada, a qual se mostrou efetiva para a previsão do comportamento do % C do banho, após a adição do carburante. Verificou-se que a taxa de ganho de carbono associada inicial, é favorecida com o aumento da temperatura e do teor de enxofre do metal, sendo prejudicada com aumento do percentual de cinzas do carburante. Quanto ao valor da taxa de dissolução combinada, esta mostrou um aumento quando a temperatura de adição é crescente. Notou-se que o valor da taxa de eficiência máxima possui relação com o valor da taxa de dissolução combinada, permitindo concluir que quanto maior o valor da taxa de dissolução combinada, mais rapidamente o processo atinge a sua eficiência máxima. Os resultados observados para o resíduo de coquilha de grafite, na eficiência de carburação, taxa de eficiência e na taxa de dissolução combinada, evidenciaram que este material tem potencial para ser utilizado como carburante. Comparando as condições iniciais e finais dos experimentos, verificou-se que banhos tratados com carburante sintético com baixo %S, apresentaram uma redução no super-resfriamento do eutético, nas temperaturas de 1485 e 1545°C, e o resíduo de coquilha contribuiu para a redução do super-resfriamento do eutético nas temperaturas de 1485, 1515 e 1545°C. Quando analisado o comportamento do grau de super-resfriamento com o tempo, após a adição dos carburantes, foi possível identificar três comportamentos distintos.
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Jacumasso, Tiago. "INFLUÊNCIA DOS PARÂMETROS DE AUSTÊMPERA EM FERRO FUNDIDO NODULAR: MICROESTRUTURA, PROPRIEDADES MECÂNICAS E ASPECTOS DA GEOMETRIA FRACTAL NA FRATURA." Universidade Estadual de Ponta Grossa, 2018. http://tede2.uepg.br/jspui/handle/prefix/2684.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
A mecânica da fratura foi desenvolvida, utilizando-se uma descrição geométrica euclidiana que pressupõem uma trinca lisa sem irregularidades. Por esta razão, a modelagem matemática de uma trinca rugosa, usando a geometria fractal, tem sido a preocupação de vários autores nas últimas décadas. O intuito destes pesquisadores é descrever o fenômeno da fratura de forma mais autentica e precisa. Uma das formas de se avaliar as propriedades mecânicas de um material fraturado é usando o conceito de integral-J. Este conceito aplicado ao fenômeno da fratura define uma curva de resistência ao crescimento de trinca chamado de curva J-R. Sendo assim, vários modelos fractais de curva J-R têm sido propostos. Um dos modelos que vem ganhando destaque na literatura científica foi proposto por ALVES (2010, 2011). Por esta razão investigou-se, neste trabalho, a aplicação desse modelo no estudo da fratura do ferro fundido nodular e ferro fundido nodular austemperado (ADI). O objetivo foi avaliar os efeitos dos tratamentos térmicos de austêmpera na microestrutura e nas propriedades mecânicas de uma liga de ferro fundido nodular. Para tanto foi empregado duas rotas de tratamentos térmicos: austêmpera convencional, consistindo de austenitização a 900ºC por 60min, seguida de austêmpera até 250ºC e à 300ºC, com permanência por 60min e 120min para cada temperatura, totalizando quatro condições, com resfriamento ao ar. As amostras tratadas termicamente foram caracterizadas com auxílio de microscopia óptica, microscopia eletrônica de varredura (FEG) e difração de raios X (DRX), com objetivo de determinar suas fases e microconstituintes. O efeito das condições de tratamento nas propriedades mecânicas foi verificado por ensaios de dureza Vickers e de impacto instrumentado Charpy. Por meio de ensaios de impacto instrumentado e solicitação mecânica de tração e com o auxílio de microscopia eletrônica por emissão de campo (FEG) foi possível estudar o crescimento de trincas rugosas na fratura do ferro fundido nodular austemperado, comparando os resultados entre as quatro condições de tratamento térmico de austêmpera. Deste modo, foi possível fornecer dados experimentais para comprovar a validade da equação da curva J-R na presença de uma trinca rugosa proposta por ALVES (2010, 2011) com base na geometria fractal e na mecânica da fratura. Os resultados obtidos permitiram comparar e discutir o efeito das rotas de tratamento térmico, no sentido de desenvolver as propriedades mecânicas do ferro fundido nodular para aplicações diversas. As curvas D J ajustadas pelo modelo fractal mostraram-se em boa concordância com aquelas obtidas pelo método descrito na ASTM E1820-17a (2017). O ADI tratado a 300ºC por 60 minutos foi o material que apresentou as melhores condições de resistência mecânica a tração e ao impacto, superando o material bruto de fundição na tenacidade a fratura, calculada pelos parâmetros fractais da curva. Este ferro fundido nodular austemperado é comparado ao da classe de alta resistência de ADI.
The mechanics of the fracture were developed using a geometric Euclidean description that assumes a smooth crack without irregularities. For this reason, the mathematical modeling of a rough crack, using fractal geometry, has been the concern of several authors in the last decades. The aim of these researchers is to describe the fracture phenomenon more authentically and accurately. One of the ways to evaluate the mechanical properties of a fractured material is by using the concept of integral-J. This concept applied to the fracture phenomenon defines a crack growth resistance curve called the J-R curve. Thus, several fractal J-R curve models have been proposed. One of the models that have gained prominence in the scientific literature was proposed by ALVES (2010, 2011). For this reason we investigated the application of this model in the study of nodular cast iron and austempered nodular cast iron (ADI). The objective was to evaluate the effects of thermal treatments of austempering in the microstructure and mechanical properties of a ductile cast iron alloy. Two routes of thermal treatments were used: conventional austenitic, consisting of austenitization at 900ºC for 60min, followed by tempering up to 250ºC and at 300ºC, with permanence for 60min and 120min for each temperature, totaling four conditions, with air cooling. The thermally treated samples were characterized by optical microscopy, scanning electron microscopy (FEG) and X - ray diffraction (XRD), in order to determine their phases and microconstituents. The effect of the treatment conditions on the mechanical properties was verified by tests of Vickers hardness and instrumented impact Charpy. By means of instrumented impact and mechanical tensile stress tests and with the aid of field emission electron microscopy (FEG), it was possible to study the growth of rough cracks in austempered nodular cast iron fracture, comparing the results between the four conditions of heat treatment. Thus, it was possible to provide experimental data to prove the validity of the J-R curve equation in the presence of a rough crack proposed by ALVES (2010, 2011) based on fractal geometry and fracture mechanics. The results obtained allowed to compare and discuss the effect of heat treatment routes in order to develop the mechanical properties of nodular cast iron for different applications. The D J curves fitting by the fractal model show in agreement with the curves obtained by the method described in the ASTM E1820-17a (2017). The ADI treated at 300ºC for 60 minutes was the material that presented the best conditions of tensile and impact mechanical strength, surpassing the crude casting material in the fracture toughness, calculated by the fractal parameters of the curve. This austempered nodular cast iron is compared to that of the ADI high strength class.
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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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Cristofolini, Renato. "Estudo da potencialidade da aplicação do ferro fundido nodular ASTM A536 60-40-18 como materia prima para processos de tixoconformação." [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/263560.
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Orientador: Maria Helena RobertTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
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Resumo: Este trabalho analisa a tixohabilidade, a viabilidade de produção de pastas tixotrópicas e as transformações de fase que ocorrem na tixofundição do ferro fundido nodular ASTM A536 60-40-18. A análise da tixohabilidade é feita através de análises térmicas utilizando técnicas de Análise Térmica Diferencial (ATD) e Calorimetria Exploratória Diferencial (CED) em diferentes condições operacionais (tipo de ciclo e taxas de aquecimento/resfriamento), e através de simulação termodinâmica utilizando software THERMOCALC®. São discutidas a influência das condições dos ensaios nas temperaturas de transformações e intervalos de solidificação, e os resultados comparados com os obtidos por simulação. São discutidas as transformações de fases que ocorrem e as respectivas temperaturas, sendo proposto diagrama de fases para a liga específica em estudo. São determinadas a sensibilidade da variação da fração líquida com a temperatura (dFL/dT) e sugeridas janelas de tixoconformação, para todas as condições analisadas. Os resultados obtidos indicam uma faixa de operação para a tixoconformação da ordem de 20oC, onde uma transformação eutética se faz presente e a variação da fração líquida com a temperatura pode ser controlada adequadamente. A janela de tixoconformação depende da taxa de transferência de calor empregada: quanto maior a taxa, maior o intervalo de transformação eutética e maior a janela de tixoconformação. Quanto à análise da viabilidade de produção de pastas tixotrópicas, foram produzidas pastas por fusão parcial controlada a distintas temperaturas dentro da faixa de operação para tixoconformação determinada previamente. As microestruturas resultantes foram analisadas por microscopia ótica (MO) e eletrônica de varredura (MEV), difratometria de raios-x e microanálise utilizando energia dispersiva (EDS). Os resultados mostram a viabilidade de produção de pastas com características tixotrópicas, nas condições analisadas, apesar da estreita faixa de temperaturas da janela de tixoconformação do material estudado. Mostram ainda que a temperatura de tratamento influencia a quantidade e dimensões dos nódulos de grafita presentes na matriz da pasta, sendo que temperaturas de tixofundição superiores à faixa de transformação eutética podem levar à rápida dissolução desses nódulos e como consequência, o aumento da dureza da liga e redução de sua ductilidade. O produto tixofundido apresenta, à temperatura ambiente, estrutura constituída essencialmente de martensita, resultado do resfriamento rápido da austenita, grafita nodular de pequenas dimensões e de fases complexas em contornos de grãos martensíticos.
Abstract: This work analyses the thixoability, the viability of actual production of thixotropic semi-solid of ferritic nodular cast iron ASTM A536 60-40-18, as well as the phase transformations taking place in the process. Thixoability evaluation is made through thermal analysis by Differential Thermal Analysis (DTA) and Differential Scanning Calorimetry (DSC) tests in different conditions (cycle type and heating/cooling rate), and also through thermodynamic simulations using THERMOCALC® software. Related to these analysis it is evaluated the influence of tests conditions on transformations temperatures and ranges; results are compared to those obtained by simulation. Phase transformations are discussed and a specific phase diagram for the alloy investigated is proposed. Liquid fraction sensitivities with temperature (dFL/dT) are determined, and thixoforming windows are suggested. Results indicate that a thixoforming window in the order of 20°C are available; in this range a eutectic transformation takes place and the liquid fraction can be controlled. Beyond the eutectic temperature liquid fraction increases significantly with temperature variation and processing control can not be assured. Thixoforming windows depend on heat transfer rates: higher the rate, higher the eutectic range and the thixoforming window. To analyse the viability of actually producing thixotropic slurries by partial melting, samples were heated to temperatures within the thixoforming windows previously suggested. Resulting microstructures were analysed by optical and electronic microscopy, X-R diffraction and EDS microanalysis. Results show the feasibility of producing thixotropic semi-solid of the studied nodular iron, in spite of its narrow thixoforming field; treatment temperature influences the size and amount of graphite nodules in the matrix. Higher temperatures can lead to fast dissolution of graphite, jeopardizing the ductility of the material. Thixocast product presents, at room temperature, small nodules of graphite in a martensitic matrix and a complex phase in grain boundaries.
Doutorado
Materiais e Processos de Fabricação
Doutor em Engenharia Mecânica
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Tinoco, José. "On the Spray Forming of Metals, the Formation of Porosity and the Heat Evolution during Solidification." Doctoral thesis, KTH, Casting of Metals, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3636.
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This thesis deals with the heat evolution duringsolidification and its relation to the formation of porosity.It intends to improve the current understanding of theformation of porosity in cast materials with special interestin nodular cast iron and the spray forming process. Twodifferent systems, a Fe-based alloy, Cast iron, and a Ni-basedalloy, Inconel 625, are examined. The effect on the heatevolution of the morphology and the processing parameters inspray forming are treated.
An evaluation of the microstructural features, segregationbehavior and physical properties such as latent heat of fusionis performed byusing thermal analysis under cooling ratesranging from 0.1 to 104 K/s. In order to achieve this amodified differential thermal analysis (DTA) equipment, amirror furnace and levitation casting are used. Results arepresented in terms of the fraction of solidified, the coolingrate and the microstructure observed. The measured latent heatof fusion is not constant throughout the solidificationprocess. Variations in morphology and cooling rate affect therelease of the latent heat.
A thermodynamic model is used to describe the experimentalobservations and to explain the formation of pores in nodularcast iron by taking into consideration the formation of latticedefects during the liquid/solid transformation. In this casethe formation of porosity is regarded as a consequence ofchanges in the volume fraction ratio graphite/ during thesolidification process.
A numerical model of the spray forming process is developedby means of CFD modelling and compared with experimentalmeasurements performed in an industrial facility. Stagnationpressure measurements provided information about the gas flowvelocity and an analysis of the overspray powder providedinformation about the particle thermal history. Evaluation ofthe deposit was also performed. It is observed that the processconditions in spray forming promote non-equilibriumsolidification even though solidification at the deposit occursat a lower rate. In this case the porosity formed near theinterface substrate/deposit depends largely on the substratetemperature. The presence of certain reactive elements, such astitanium, affects the porosity levels in the rest of thedeposit.
Keywords:Thermal Analysis, Nodular Cast Iron, Inconel625, CFD, Flow Assesment, Multiphase Flow, Spray Deposition,Microporosity, Superalloys
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Magnusson, Lena. "On the Nucleation and Inoculation of Metals." Doctoral thesis, Stockholm : Royal Institute of Technology, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3893.
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Martinez, Thomas. "Etude de l'endommagement lors du démasselotage à chaud de bielles en fonte GS ADI moulées forgées." Thesis, Reims, 2016. http://www.theses.fr/2016REIMS002/document.
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Les travaux de cette thèse ont été initiés par la volonté industrielle de lever le verrou technologique du démasselotage à chaud de bielles en fonte GS. Ces bielles sont obtenues par un procédé de fabrication hybride innovant mêlant forgeage et fonderie en moule métallique. Ce procédé exige que le démasselotage soit effectué dans la « chaude de coulée » lorsque la fonte GS est en phase austénitique. La découpe de la fonte dans ces conditions de température fait apparaître des défauts majeurs sur les surfaces découpées préjudiciables à la suite du process. Pour pouvoir répondre à cette problématique, une étude est menée sur la caractérisation du comportement et de l’endommagement de la fonte GS dans les conditions de température du process. Une attention particulière est portée sur l’influence de la microstructure nodulaire sur les mécanismes de la rupture. Afin de se doter d’outils de simulation pour mettre au point le processus de démasselotage à chaud, les paramètres du modèle de comportement et d’endommagement de Gurson-Tvergaard-Needleman appliqués à la fonte GS sont identifiés par méthode inverse. Enfin, un plan d’expérience est déployé sur un démonstrateur de découpe instrumenté afin d’obtenir la configuration optimale des paramètres process pour une découpe sans défaut. Cette dernière étude met en avant la présence d’une transition d’un mode de rupture ductile à fragile lors de l’apparition des défauts de démasselotageThis work was initiated by the technological problematic of hot trimming of nodular cast iron connecting rods. These connecting rods are obtained by an innovative hybrid process that combines forging and metal mold casting. This process requires the trimming to be conducted at high temperatures in the is the austenitic phase of the cast iron. Hot trimming of cast iron brings up major defects on the cut surfaces which are detrimental to the continuing process. To address this problem, a study is conducted on the characterization of the mechanical behavior of nodular cast iron in the process temperature conditions. A particular attention is paid to the influence of the nodular microstructure on the failure mechanisms. To develop simulation tools for nodular cast iron hot trimming, the parameters of Gurson-Tvergaard-Needleman model are identified by inverse method for our material. Finally, a design of experiment is deployed using an instrumented demonstrator to obtain the optimum parameters configuration for a maximized cut surface quality. This latest study highlights the presence of a transition from ductile to brittle mode of failure leading to the hot trimming defects
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Mozetic, Halston José. "Design de produto : seleção de materiais e processos com aplicação de campo magnético em núcleos de alto-falantes." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2008. http://hdl.handle.net/10183/15735.
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Este trabalho tem por objetivo apresentar os resultados obtidos com o uso da técnica de campo magnético induzido durante o tratamento térmico do Ferro Fundido Nodular em desenvolvimento de núcleos de alto-falantes. Para este estudo foi escolhido como material o Ferro Fundido Nodular devido ao baixo custo de obtenção das peças e também por ser um material de fácil aquisição no mercado. Foram confeccionadas 90 amostras deste Ferro Fundido Nodular com percentuais diferenciados de Ferro, Silício e Carbono, sendo que as amostras quando foram submetidas ao tratamento térmico de recozimento também sofreram a indução magnética. Os parâmetros utilizados no tratamento térmico situaram-se na faixa de temperatura de aquecimento de 900ºC até 920ºC e uma indução magnética "B" entre 16000 e 20000 Gauss. O grande desafio deste trabalho estava no fato de que variações de composição das ligas de ferro fundido nodular, aliadas as inclusões de outros materiais não magnetizáveis, modificavam, para pior, o desempenho dos núcleos dos alto-falantes. Para obter-se, então, uma estrutura em que o fluxo magnético pudesse permear, buscou-se primeiramente selecionar a liga de ferro fundido eliminando ao máximo os materiais não magnetizáveis, e só então, estudar um processo de tratamento térmico com indução magnética que tornasse o material adequado ao uso nos núcleos de alto-falantes Para melhorar as propriedades magnéticas de forma contundente, buscou-se através do recozimento com campo induzido um alinhamento dos domínios, ou seja, uma ordenação dos "spins" dentro dos grãos do material que juntamente com a elevação de temperatura tenderam a ter um mesmo sentido, facilitando de maneira significativa a passagem do fluxo magnético, propriedade importante para o desempenho dos núcleos de alto-falantes. Foram realizados recozimentos com campo induzido observando-se o desempenho da permeabilidade magnética inicial das peças e posteriormente medidas com equipamento de saturação de campo. Esses resultados foram correlacionados com os dados obtidos pelo uso do aço SAE 1020, nas mesmas condições de uso e teste de laboratório. Foram realizados estudos metalográficos, além de análises de composição química das amostras e a relação destes fatores com as propriedades magnéticas. Também foram estudados os dados de usinabilidade das amostras do ferro fundido nodular tratadas termicamente com indução magnética e subseqüentemente comparados com o Aço SAE 1020. Do ponto de vista científico, uma das contribuições deste trabalho, está na influência da indução de campo magnético durante o tratamento térmico das amostras, pois é possível verificar um ganho significativo nas propriedades magnéticas apresentadas pelos núcleos dos alto-falantes durante os testes de desempenho. A outra está no fato de que ganhos correlacionados ao design do produto possibilitam utilizar o ferro fundido como uma alternativa economicamente viável e perfeitamente ajustável à alta performance dos alto-falantes. Como resultado deste estudo foi demonstrado à possibilidade do uso do recozimento com indução magnética, como forma de aumentar a permeabilidade de um material com alto teor de carbono, no caso específico, o ferro fundido nodular. Este trabalho permite afirmar que é possível desenvolver núcleos magnéticos de alto-falantes em ferro fundido nodular com alto desempenho e também sugerir que outras aplicações onde seja necessário aumento do desempenho magnético esta técnica possa ser aplicada.This work aims to present the results obtained with the use of induced magnetic field during the heat treatment of Nodular Cast Iron for speaker cores. For this study development, the chosen material is the nodular cast iron due to the low trading costs and ease of purchase on the market. Ninety samples of nodular cast iron were constructed, with different iron, silicon and carbon contents. Samples, when subjected to annealing, were also subjected to magnetic induction. The final temperature on the heat treatment was in the range of 900ºC to 920ºC, and the magnetic induction was in the range of 16000 to 20000 Gauss. The challenge of this work was in the fact that compositional changes in the nodular cast iron, allied to inclusions of non-magnetizable materials, modify for worse the performance of speaker cores. To obtain a structure that the magnetic field could permeate, the cast iron alloys were selected to eliminate, at most, the presence of non-magnetizable materials, and only then consider a heat treatment process with magnetic induction to make the material suitable for use in speaker cores. To improve the magnetic properties, an alignment of dipoles of the material, through induced magnetic field during annealing was intended. Annealing with induced magnetic field was carried out, observing the performance of the initial magnetic permeability of the samples, and subsequently measured with field saturation equipment The results were correlated with the obtained data from the use of the SAE 1020 steel, with the same conditions of use and laboratory tests. Metallographic and chemical composition analyses were carried out on the samples, and the correlation of these data with the magnetic properties was estmated. Also machinability of the thermal treated with magnetic induction nodular cast iron samples were analyzed and compared with the SAE 1020 steel. From the scientific point of view, one of the contributions of this work is the influence of induced magnetic field during the heat treatment of the samples, since it was possible to verify a significant gain in the magnetic properties of the speaker cores during the performance tests. Another contribution is the fact that gains correlated with the design of the product enable the use of cast iron as an economically viable and fully adjustable material to the high performance of subwoofers. As a result of this work, the possibility of using annealing with magnetic induction was presented as a way to increase the permeability of a material with high carbon content, in this particular case, the nodular cast iron. This research allows asserting that it is possible to develop speaker magnetic cores of nodular cast iron with high performance and also suggest that this technique can be applied to other applications where it is necessary to increase their magnetic performance.
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Fager, Fredrick, and Serg Chanouian. "Nuclear Waste Canister : Evaluating the mechanical properties of cassette steel after casting." Thesis, KTH, Materialvetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-209803.
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Företaget Svensk Kärnbränslehantering AB (SKB) håller på att utveckla en slutförvaringskapsel som kommer innehålla avfall från den svenska kärnkraften. Det är dock fortfarande en process under utveckling och därför undersöks olika typer av metoder och kapselmaterial för att kunna tillverka en hållbar och säker kapsel. Kapseln består av ett hölje av kopparrör med svetsad botten och lock och en insats med stållock. Insatsen är en cylindrisk konstruktion av segjärn och innehåller en svetsad stålkassett för att skapa utrymmen till det använda kärnbränslet. Insatsen innehåller bland annat stålrör som under tillverkning får utstå en gjutprocess med segjärn och erhåller efter det icke homogena egenskaper. Målet med undersökningen är hur stor påverkan gjutningen har på stålets kemiska sammansättning samt mikrostrukturer. Det som orsakar de inhomogena egenskaperna är främst värmebehandlingen som driver diffusionen av kol från gjutjärnet till stålet, som då ger ett hårdare men sprödare material. Med hjälp av experiment och simuleringar upptäcks hur mycket kol som diffunderar in i stålet samt ändringar i den kemiska sammansättningen i de påverkade zonerna. Identifiering av fasomvandlingar, diffusion och ändringar i mikrostrukturer är stora faktorer som i sin tur ändrar de mekaniska egenskaperna i stålet.The Swedish Nuclear Fuel and Waste Management Company (SKB) have developed a final storage canister that will contain waste from the Swedish nuclear power plants. However, it is still in a development phase and therefore different types of methods and canister materials are investigated to produce the most durable and safe canister. The canister is made of a copper tube with a welded bottom and lid with an insert. The insert is a cylindrical construction of nodular cast iron that contains a welded steel cassette, to make space for the spent fuel, and a steel lid. The steel tubes showed inhomogeneous properties after being exposed to a casting around them. The aim of this investigation is to clarify the impact of casting on the chemical composition of the steel as well as the microstructure. The cause to the inhomogeneous properties were the diffusion of carbon from the cast iron to the steel, which then produced a harder and more brittle material. Experiments and simulations were used to see the carbon diffusion into the steel as well as what happens with the chemical composition in the affected zones. Identification of phase changes, diffusion and microstructures contributed to changes of mechanical properties in the steel.
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Magalhães, Elton Franco de. "Caracterização e proposição de métodos estimativos das propriedades monotônicas e cíclicas dos ferros fundidos nodulares." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/88/88131/tde-03052012-165941/.
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Para o correto dimensionamento da maioria dos componentes estruturais é necessário informações sobre a resposta do material quando submetido à fadiga de alto e baixo ciclo, bem como conhecer as propriedades monotônicas (não-cíclicas) e cíclicas dos materiais. Na literatura são encontradas amplas divulgações de dados sobre diversos materiais de engenharia (Ex. SAE J1099 Technical Report on Fatigue Properties). Porém, quando se trata de ferro fundido nodular estas informações são limitadas, sendo assim, visa-se neste trabalho caracterizar as propriedades monotônicas e cíclicas destes materiais em complemento aos trabalhos já publicados na literatura e propor métodos para a estimativa destas propriedades a partir da dureza. Faz-se necessário a proposição de métodos estimativos das propriedades mecânicas destes materiais baseados na dureza devido às suas grandes variações que são inerentes ao processo de fundição. Em um mesmo componente podem existir diferentes classes de ferro fundido, que apesar de possuir a mesma composição química, podem apresentar variações nas propriedades mecânicas devido à formação de diferentes estruturas metalúrgicas que são sensíveis às taxas de resfriamento do material que variam de acordo com as características geométricas da peça que está sendo fundida, principalmente a variação da espessura. Neste estudo a determinação das relações entre as propriedades monotônicas e cíclicas dos ferros fundidos nodulares foram obtidas a partir do tratamento dos dados publicados na literatura levando-se em consideração o índice de qualidade. Foi proposto um modelo contínuo com relação à dureza para a estimativa das propriedades monotônicas, do coeficiente de resistência cíclico e do expoente de encruamento cíclico e para a estimativa das propriedades cíclicas que experimentalmente demonstraram não ter correlação com a dureza foi proposto uma forma discreta, que consistiu na recomendação de valores típicos definidas por faixas de dureza.For the correct design of the most part of structural components is necessary to have information about the material response under both high cycle and low cycle fatigue, as well as the knowledge of monotonic and cyclic materials properties. In literature a major publication of several engineering material data can be found (e.g, SAE J1099 - Technical Report on Fatigue Properties), but regarding to ductile iron this information is quite limited. Therefore, this work aims to characterize the monotonic and cyclic properties of this material in complementing to the available data in the literature and also make a proposition of methods to estimate this properties from hardness. The mechanical properties estimation model from hardness is relevant to take into account the inherent variations of casting process, which for the same chemical composition can be found different grades in a same part. This fact occurs due to the formation of different metallurgical structures that is influenced by cooling ratio which changes accordingly to geometrical characteristic of the part, especially the thickness variation. In this study the determination of the relation between monotonic and cyclic properties from hardness has been determined from literature data processing taking into account the Quality Index. For monotonic properties, the cyclic strength coefficient and the cyclic strain hardening exponent estimation has been proposed a continuous method based on hardness and for the cyclic properties that experimentally showed to remain independent of hardness has been recommended one set of properties for specific hardness ranges.
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Musilová, Iveta. "PROGRESIVNÍ VÝROBNÍ POSTUPY A MODELOVÁNÍ STRUKTUR A VLASTNOSTÍ LITIN S KULIČKOVÝM GRAFITEM." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2010. http://www.nusl.cz/ntk/nusl-233882.
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The thesis is concerned with relationships between progressive technological processes of spheroidal graphite cast iron’s production and their structural properties. The aim of the work is to explain causal relationship between parameters of the proposed manufacturing technology of the iron type given (involving selected variants of modification and inoculation of melt and the parameters of melt crystallization, solidification and cooling down in a mould), their structure and even chemical heterogeneity of elements in this structure. For close specification of presented relationships three-dimensional model of spheroidal graphite growth was used, which was developed at the Brno University of Technology, Faculty of Mechanical Engineering. Its usability in praxis has been verified on the basisis of the application of this model on experimentally acquired data. The U GRAFIT 20 model of the authors Stránský and Million counting segregation in the frame of eutectic cell has not still been used for prediction of segregation in real condition in greater extent. On the basis of the above mentioned model microsegregation within “on average” of the cell has been discovered during experimental melts. Microsegregation has been described by segregation and heterogeneity indexes. Calculated values of segregation and heterogeneity indexes have been compared with experimentally verified values. On the basis of comparison of calculated and measured values the possibility of further usage of the mentioned model in praxis has been explored.
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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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Kavan, Petr. "Řešení technologie součásti "víko" v podmínkách středně velké strojírenské firmy." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2011. http://www.nusl.cz/ntk/nusl-229896.
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The diploma thesis is concerned with evaluation of actual production technology of part “hydraulics cover” and with design of new, progressive variation machining of this part. Solution is focused at first on rationalization of cutting tools and choice of suitable cutting tools. An effort is to achieve shorter production time and decrease costs on production of component. With this problem is related alteration of technological documentation and technical economic evaluation for determination return rate of investments into progressive cutting tools.
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COLOSIO, MARCO A. "Efeito da nitretação na tenacidade de ferros fundidos nodulares bainíticos e martensíticos." reponame:Repositório Institucional do IPEN, 1998. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11586.
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Dissertação (Mestrado)
IPEN/D
Universidade Mackenzie. Departamento de Engenharia de Materiais, São Paulo
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Lachambre, Joël. "Développement d'une méthode de caractérisation 3D des fissures de fatigue à l'aide de la corrélation d'images numériques obtenues par tomographie X." Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0050/document.
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Ce mémoire présente une méthode mise au point pour caractériser et analyser des fissures de fatigue présentant un fort caractère tridimensionnel dans des matériaux métalliques opaques. L'analyse consiste à déterminer avec précision la position du front de la fissure étudiée et à mesurer des valeurs de facteurs d'intensité des contraintes le long du front par projection sur les séries de Williams du champ de déplacement issu de la corrélation numérique d'images 3D obtenues par tomographie aux rayons X. La corrélation d'images 3D numériques est utilisée afin de mesurer le champ de déplacement en volume lors de la mise sous chargement d'une éprouvette fissurée fatiguée. La corrélation d'images nécessitant un mouchetis, le matériau retenu pour les expériences est la fonte à graphite sphéroïdal car il présente un mouchetis 3D naturel (les nodules de graphites) parfaitement imagé par tomographie aux rayons X. Le cyclage est appliqué à l'aide d'une machine de fatigue in situ permettant d'alterner des phases de propagation de la fissure avec des acquisitions tomographiques sous différentes charges. L'introduction d'un défaut artificiel (une entaille obtenue par usinage laser) permet de maîtriser l'amorçage et la propagation de la fissure in situ. La méthode de corrélation d'images 3D numériques employée dans ces travaux étant basée sur des éléments finis, nous avons cherché à tirer profit de différents outils développés dans le cadre de cette méthode. Les surfaces libres sont spécifiées afin de bien conditionner le maillage et un enrichissement dans l'esprit des X-FEM permet de renseigner la fissure dont la position est repérée grâce à la trace laissée dans le résidu de corrélation entre l'image avant cyclage et la dernière image acquise. Une régularisation mécanique est également introduite dans le calcul sous forme d'un filtre de longueur d'onde choisie. Le champ de déplacement mesuré avec précision est ensuite projeté sur les séries de Williams augmentées des termes correctifs de Leblond et Torlai qui prennent en compte la courbure du front de la fissure. L'annulation du terme super-singulier d'ordre -1 des séries de Williams est utilisée pour détecter la position du front de la fissure. Une procédure itérative a été mise en place afin de concilier l'enrichissement et la courbure du front avec la projection sur les séries de Williams. Une fois la position du front 3D de la fissure déterminée et les valeurs des facteurs d'intensité des contraintes associées calculées, les résultats obtenus sont confrontés à la littératureThis manuscript describes a methodology used to compute Stress Intensity Factor values along the curved front of a fatigue crack inside a nodular cast iron. An artificial defect is introduced at the surface of a small sample. The initiation and growth of a fatigue crack from this defect during constant amplitude cycling is monitored in situ by laboratory x-ray tomography. The method for processing the 3D images in order to compute SIF values is described in detail. The results obtained show variations of the stress intensity factor values along the crack front
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Nishikawa, Arthur Seiji. "Têmpera e partição de ferros fundidos nodulares: microestrutura e cinética." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/3/3133/tde-05022019-092855/.
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Este trabalho está inserido em um projeto que procura estudar a viabilidade técnica da aplicação de um relativamente novo conceito de tratamento térmico, chamado de Têmpera e Partição (T&P), como alternativa para o processamento de ferros fundidos nodulares com alta resistência mecânica. O processo T&P tem por objetivo a obtenção de microestruturas multifásicas constituídas de martensita e austenita retida, estabilizada em carbono. A martensita confere elevada resistência mecânica, enquanto a austenita confere ductilidade. No processo T&P, após a austenitização total ou parcial da liga, o material é temperado até uma temperatura de têmpera TT entre as temperaturas Ms e Mf para produzir uma mistura controlada de martensita e austenita. Em seguida, na etapa de partição, o material é mantido isotermicamente em uma temperatura igual ou mais elevada (denominada temperatura de partição TP) para permitir a partição de carbono da martensita para a austenita. O carbono em solução sólida diminui a temperatura Ms da austenita, estabilizando-a à temperatura ambiente. O presente trabalho procurou estudar aspectos de transformações de fases -- com ênfase na evolução microestrutural e cinética das reações -- do tratamento térmico de Têmpera e Partição (T&P) aplicado a uma liga de ferro fundido nodular (Fe-3,47%C-2,47%Si-0,2%Mn). Tratamentos térmicos consistiram de austenitização a 880 oC por 30 min, seguido de têmpera a 140, 170 e 200 oC e partição a 300, 375 e 450 oC por até 2 h. A caracterização microestrutural foi feita por microscopia óptica (MO), eletrônica de varredura (MEV), difração de elétrons retroespalhados (EBSD) e análise de microssonda eletrônica (EPMA). A análise cinética foi feita por meio de ensaios de dilatometria de alta resolução e difração de raios X in situ usando radiação síncrotron. Resultados mostram que a ocorrência de reações competitivas -- reação bainítica e precipitação de carbonetos na martensita -- é inevitável durante a aplicação do tratamento T&P à presente liga de ferro fundido nodular. A cinética da reação bainítica é acelerada pela presença da martensita formada na etapa de têmpera. A reação bainítica acontece, a baixas temperaturas, desacompanhada da precipitação de carbonetos e contribui para o enriquecimento em carbono, e consequente estabilização, da austenita. Devido à precipitação de carbonetos na martensita, a formação de ferrita bainítica é o principal mecanismo de enriquecimento em carbono da austenita. A microssegregação proveniente da etapa de solidificação permanece no material tratado termicamente e afeta a distribuição da martensita formada na etapa de têmpera e a cinética da reação bainítica. Em regiões correspondentes a contornos de célula eutética são observadas menores quantidades de martensita e a reação bainítica é mais lenta. A microestrutura final produzida pelo tratamento T&P aplicado ao ferro fundido consiste de martensita revenida com carbonetos, ferrita banítica e austenita enriquecida estabilizada pelo carbono. Adicionalmente, foi desenvolvido um modelo computacional que calcula a redistribuição local de carbono durante a etapa de partição do tratamento T&P, assumindo os efeitos da precipitação de do crescimento de placas de ferrita bainítica a partir da austenita. O modelo mostrou que a cinética de partição de carbono da martensita para a austenita é mais lenta quando os carbonetos precipitados são mais estáveis e que, quando a energia livre dos carbonetos é suficientemente baixa, o fluxo de carbono acontece da austenita para a martensita. A aplicação do modelo não se limita às condições estudadas neste trabalho e pode ser aplicada para o planejamento de tratamentos T&P para aços.The present work belongs to a bigger project whose main goal is to study the technical feasibility of the application of a relatively new heat treating concept, called Quenching and Partitioning (Q&P), as an alternative to the processing of high strength ductile cast irons. The aim of the Q&P process is to obtain multiphase microstructures consisting of martensite and carbon enriched retained austenite. Martensite confers high strength, whereas austenite confers ductility. In the Q&P process, after total or partial austenitization of the alloy, the material is quenched in a quenching temperature TQ between the Ms and Mf temperatures to produce a controlled mixture of martensite and austenite. Next, at the partitioning step, the material is isothermally held at a either equal or higher temperature (so called partitioning temperature TP) in order to promote the carbon diffusion (partitioning) from martensite to austenite. The present work focus on the study of phase transformations aspects -- with emphasis on the microstructural evolution and kinetics of the reactions -- of the Q&P process applied to a ductile cast iron alloy (Fe-3,47%C-2,47%Si-0,2%Mn). Heat treatments consisted of austenitization at 880 oC for 30 min, followed by quenching at 140, 170, and 200 oC and partitioning at 300, 375 e 450 oC up to 2 h. The microstructural characterization was carried out by optical microscopy (OM), scanning electron microscopy (SEM), backscattered diffraction (EBSD), and electron probe microanalysis (EPMA). The kinetic analysis was studied by high resolution dilatometry tests and in situ X-ray diffraction using a synchrotron light source. Results showed that competitive reactions -- bainite reaction and carbides precipitation in martensite -- is unavoidable during the Q&P process. The bainite reaction kinetics is accelerated by the presence of martensite formed in the quenching step. The bainite reaction occurs at low temperatures without carbides precipitation and contributes to the carbon enrichment of austenite and its stabilization. Due to carbides precipitation in martensite, growth of bainitic ferrite is the main mechanism of carbon enrichment of austenite. Microsegregation inherited from the casting process is present in the heat treated material and affects the martensite distribution and the kinetics of the bainite reaction. In regions corresponding to eutectic cell boundaries less martensite is observed and the kinetics of bainite reaction is slower. The final microestructure produced by the Q&P process applied to the ductile cast iron consists of tempered martensite with carbides, bainitic ferrite, and carbon enriched austenite. Additionally, a computational model was developed to calculate the local kinetics of carbon redistribution during the partitioning step, considering the effects of carbides precipitation and bainite reaction. The model showed that the kinetics of carbon partitioning from martensite to austenite is slower when the tempering carbides are more stable and that, when the carbides free energy is sufficiently low, the carbon diffuses from austenite to martensite. The model is not limited to the studied conditions and can be applied to the development of Q&P heat treatments to steels.
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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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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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Melado, André Caetano. "Ferros fundidos nodulares de alta resistência obtidos por tratamento térmico de têmpera e partição: microestrutura e comportamento mecânico." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/3/3133/tde-16072018-134449/.
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A aplicação do novo conceito de tratamento térmico, chamado de têmpera e partição (Q&P), desenvolvido para a obtenção de aços da terceira geração da classe AHSS (Advanced high strengh steel ou aços avançados de alta resistência), mostra-se uma alternativa para o processamento de ferros fundidos nodulares com alta resistência mecânica. No processo Q&P, o carbono presente na martensita supersaturada, formada na etapa de têmpera, é utilizado para estabilizar a austenita não transformada durante a etapa de partição, mantendo-a estável na temperatura ambiente. Essa rota de tratamento térmico consiste em realizar uma têmpera no material (após uma etapa prévia de austenitização) numa faixa de temperatura entre o Ms e Mf (temperatura de início e fim da transformação martensítica, respectivamente), seguido de um reaquecimento e manutenção a uma temperatura acima do Ms (etapa isotérmica de partição) com o objetivo de que o carbono migre da martensita supersaturada para a austenita remanescente promovendo sua estabilização. Essa partição do carbono só é possível caso a precipitação da cementita seja suprimida, e isso é conseguido com a presença de elementos de liga, como o Si e/ou Al. Neste trabalho foi feito um estudo sobre as características microestruturais e mecânicas de um ferro fundido nodular (3,47%C; 2,47%Si; 0,2%Mn) submetido ao tratamento térmico de têmpera e partição, o qual foi denominado neste trabalho como, Q&PDI (Quenched and Partitioned Ductile Iron ou Ferro Fundido Nodular Temperado e Particionado). Para isso foi realizada uma austenitização plena nas amostras, a 880°C, por duas horas, seguida de uma têmpera em óleo pré-aquecido nas temperaturas de 140 e 170°C. A etapa de partição foi feita nas temperaturas de 300, 375 e 450°C, com intervalos de tempo variando de 5 a 120 minutos. A caracterização microestrutural foi realizada através de microscopia ótica, microscopia eletrônica de varredura e EBSD. A técnica de difração de raios-X foi empregada para quantificar a fração volumétrica e o teor de carbono na austenita retida. Ensaios de dilatometria, difração de raios-X \"in situ\" e nanoindentação foram empregados para auxiliar na análise das transformações de fases que ocorreram na etapa de partição, como a transformação bainítica e a precipitação de carbonetos de transição nas placas de martensita. A caracterização mecânica foi feita através de ensaios de tração, impacto, dureza, nanoindentação, tenacidade à fratura e resistência à fadiga. Ensaios de compressão auxiliaram na análise da transformação martensítica induzida por deformação. Os resultados obtidos mostraram que é possível obter ferros fundidos nodulares com alta resistência mecânica (limite de resistência >1450 MPa), com consideráveis ductilidade (de até 9%) e energia absorvida sob impacto (de até 81 J), bem como tenacidades à fratura de 55 MPa.m1/2 e limites de fadiga de 550 MPa. Este comportamento é proporcionado por uma microestrutura singular, constituída por uma dispersão homogênea de placas de martensita numa matriz de ausferrita bastante refinada, com consideráveis frações volumétricas de austenita retida (max. 23%).Quenching and partitioning (Q & P), a new heat treatment concept developed to obtain third generation AHSS (Advanced High Strength Steel), is an alternative for processing of nodular cast irons in order to obtain high mechanical strength. In the Q & P process, the carbon present in the supersaturated martensite formed in the quenching step diffuses towards the untransformed austenite during the partition step, keeping it stable at room temperature. This heat treatment route consists of quenching the material (after a previous step of austenitization) in a temperature range between Ms and Mf (beginning and end temperature of the martensitic transformation, respectively), followed by reheating and maintenance at a temperature above the Ms (isothermal stage of partition) allowing the carbon to migrate from the supersaturated martensite to the remaining austenite, promoting its stabilization. This partition of carbon is only possible if precipitation of cementite is suppressed; this is achieved adding alloying elements such as Si and/or Al. In this work a study was made on the microstructural and mechanical characteristics of a ductile iron (3.47%C; 2.47%Si; 0.2%Mn), submitted to a Q&P heat treatment, in this work named Q & PDI (Quenched and Partitioned Ductile Iron). A full sample austenitization was carried out at 880 ° C for two hours, followed by a pre-heated oil quanching at temperatures of 140 and 170 ° C. The partitioning step was at temperatures of 300, 375 and 450Â ° C, with time intervals ranging from 5 to 120 minutes. Microstructural characterization was performed through optical microscopy, scanning electron microscopy and EBSD. The X-ray diffraction technique was used to quantify the volumetric fraction and the carbon content in the retained austenite. Dilatometry, X-ray diffraction \"in situ\" and nanoindentation were also used to aid in the analysis of the phase transformations that occurred in the partitioning stage, such as the bainitic transformation and the precipitation of transition carbides in the martensite plates. Mechanical characterization was performed through tensile, impact, hardness, nanoindentation, fracture toughness and fatigue strength tests. Compression tests aided in the analysis of the deformation induced martensitic transformation. The results showed that it is possible to obtain nodular cast irons with high mechanical strength (resistance limit> 1450 MPa), with considerable ductility (up to 9%) and energy absorbed under impact (up to 81 J), as well as fracture toughness of 55 MPa.m -1 / 2 and fatigue limits of 550 Mpa. This behavior is provided by a unique microstructure, consisting of a homogeneous dispersion of martensite plates in a very refined ausferrite matrix, with considerable volumetric fractions of retained austenite (max. 23%).
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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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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.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.
QC 20180523
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吳慶郎. "Simulation of solidification in eutectic nodular cast iron system." Thesis, 1988. http://ndltd.ncl.edu.tw/handle/59909604391109681403.
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Pires, António Jorge Ferreira. "Use of Thermal Analysis for Evaluation Of Inoculation Efficiency In Nodular Cast Iron." Dissertação, 2020. https://hdl.handle.net/10216/129259.
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Pires, António Jorge Ferreira. "Use of Thermal Analysis for Evaluation Of Inoculation Efficiency In Nodular Cast Iron." Master's thesis, 2020. https://hdl.handle.net/10216/129259.
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Lin, Cheng, and 林晟. "The Study on Rare Earth Element (Ce) Decay in Thin Casting Nodular Cast Iron." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/y3y96u.
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碩士國立臺北科技大學
材料科學與工程研究所
97
The main propose of this thesis is to investigate the influence of metallographic on cast iron which have trace element. It could offer producer a feasible way and recognize the trace element to use it. The variable in the experiment include trace element type, quantity, reaction time and spheroidizing methods. And quantity of inoculation, size of inoculation and inoculate methods. In the experiment to make Nodular Cast Iron is use rare earth element (Ce) which pure rate above 99% to be nodularizer add into molten iron (FCD-450). Then inoculate with FeSi. Experiment temperature are within 1400 to 1500℃ in every furnace lot, and test pour out at different time. We use sand box to be cast mold which thin wall type in every factory, in order to know Thin Wall Nodular Cast Iron spheroidizing rate influence by nodularizer decay. We know produce procedure of Nodular Cast Iron, melting → spheroidizing → inoculation → casting → sampling. Spheroidizing and inoculation reaction are perform in ladel. Due to this experiment principal issue is nodularizer decay time in molten iron, molten iron pour out at different time, so we need to adjust procedure to match experiment demand. Experiment result shows that use cerium 3% to replace magnesium to be nodularizer, and add inoculate FeSi 1.5%. When spheroidizing 15~20 min., we can obtain Thin Casting Nodular Cast Iron nodularity 90%. when spheroidizing at a long time later, nodularity below 50%, to replace vermicular and flat piece graphite. In addition, this article is directed to manufacturing process about use cerium to replace magnesium to manufacture Thin Casting Nodular Cast Iron.
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Cheng, Tsai Tzung, and 蔡宗成. "The Effect of Alloy Elements and Microstructure on the Magnetic Properties of Ferritic Nodular Cast Iron." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/41259113160369211285.
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碩士國立臺灣科技大學
機械工程研究所
83
The study was aimed to discuss that the effect of nodularity, matrix structure and alloy elements on the magnetic properties of ferritic nodular cast iron in as-cast and heat treated con- dition, and to promote the feasibly of ferritic nodular cast iron been applied as industry magnetic materials. The nodular cast iron bar which was cut into ring sample with outside dia- meter 30mm,inside diameter 18mm,and thickness 5.4mm.After wind- ing ,set up was used hysteresis loop measurement. The nodularity microstructure was analyzed with image analysis system to get the experiment data for analysis and discussion. The results of this experiment indicated that if the ferritic nodular cast iron with higher nodularity,it would have better soft magnetic properties. The addition of silicon element can promote the soft magnetic properties of ferritic nodular cast iron.Increasing the silicon content would lower the coercive force and hysteresis losses.But the addition of manganese elem- ent has adverse effect. Increasing the manganese content would cause segregation and lower the soft magnetic properties. Heat treatment with annealing would decrease the lattice defects and make the soft magnetic properties better,but in a longer anneal- ing time,graphite growing would affect the total magnetic prope- rties.The grain size would not show any specific influence on the magnetic properties of ferritic nodular cast iron.
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Tung, Che-Hsiung, and 童哲雄. "The microstructure and mechanical property of hot-rolling nodula r cast iron." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/03196175916010864876.
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Yang, Rong Zhong, and 楊榮忠. "The influence of graphite nodules and size on austenitization of ductile cast iron." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/09428823973116950194.
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