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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
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James, Jocelyn S. "The microstructural modelling of austempered ductile iron camshafts." Thesis, Loughborough University, 1999. https://dspace.lboro.ac.uk/2134/14359.
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Austempered ductile iron (AD!) is a material which is receiving increasing interest from the manufacturers of automotive components such as camshafts due to its superior mechanical properties, and in particular excellent wear resistance, compared with other grades of cast iron. ADI is produced from a spheroidal graphite casting using a two-stage heattreatment process. During the first stage of the heat-treatment the matrix is transformed to austenite, and then in the second austempering stage, some of the austenite is transformed to bainitic ferrite. The final microstructure is therefore complex, consisting of graphite, bainitic ferrite, austenite, carbides and possibly martensite. The major focus of this work has been to develop a novel method of predicting the effect of composition and heat-treatment parameters on the major constituents of the microstructure. This has resulted in a single model which can predict a 'microstructural map' of ADI and will assist the foundry industry in reducing lead times for component manufacture. The high temperature equilibrium between graphite and austenite was investigated using Gibbs free energy minimisation in conjunction with critically assessed thermodynamic data. Having established the carbon concentration in austenite at the start of the austempering process, the volume fraction of bainitic ferrite was established from prediction of the limiting carbon content for the diffusionless transformation. The kinetics of the bainite transformation were determined by making modifications to a model which was originally developed for low alloy steels. The predictions were compared with experimental data obtained, both during the course of this research and available in the literature, using dilatometric and X-ray diffraction techniques. The kinetics of the austenitisation were investigated through consideration of a diffusion couple between graphite and austenite. The degree of segregation and formation of primary carbides, in the original ductile iron casting, was calculated using a Scheil approach to solidification. The effect of this segregation was subsequently accounted for by making microstructural predictions on a number of individual 'shells' of material between two graphite nodules. Finally, complete microstructure predictions were compared with reported mechanical properties for a range of compositions and heat treatments of austempered ductile irons.
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Putman, Duncan Colin. "Modelling of microstructural evolution in austempered ductile iron." Thesis, Loughborough University, 2004. https://dspace.lboro.ac.uk/2134/36092.
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Austempered ductile iron (ADI) has a microstructure consisting mainly of high carbon austenite, bainitic ferrite and graphite nodules, produced by a two stage austenitisation and austempering heat treatment. The resulting microstructure gives these materials a combination of high strength and toughness, making them attractive for a wide range of applications. To increase surface hardness, ductile iron alloys can also be cast into chilled moulds to induce carbide formation in the required areas of components. These chilled ductile iron alloys can also be subjected to austenitisation and austempering heat treatments, therefore further improving the mechanical properties of the components core, whilst retaining the hard carbides present in the surface layers. This work encompasses three main areas: two are concerned with the production of generic microstructure models, which work in conjunction with thermodynamic modelling software MTDATA; and one relates to high temperature X-ray diffraction experiments.
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Andersson, Sofia. "Study of Dross in Ductile Cast Iron Main Shafts." Thesis, Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-37148.
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The study of dross in ductile cast iron main shafts was performed at Global Castings Guldsmedshyttan AB and presented in this master thesis. The purpose of the study was to obtain answers to why dross defects were present in some of the foundry's casted main shafts, with the main problem located at the flange of the shaft. The chemical composition of the dross formations and which steps in the casting process that increased the dross formation were of interest. The study only included dross in main shafts manufactured at Global Castings Guldsmedshyttan AB. Dross particles form when elements such as Mg, Ca, Si and Mn react with O. These elements, which are highly reactive to O, are used in ductile cast irons to achieve the spheroidal graphite nodules that regulate the cast materials ductile properties. If a higher amount of dross particles has formed, the particles will start to cluster, resulting in a growing dross formation. Dross formations works as surface crack initiation points and reduces the castings fatigue strength and ductility. During the study it was seen that the cause of dross formations is a combination of many parameters increasing the melts exposure to O resulting in dross defects. The dross formations could be connected to worn out ladles, low melt temperatures, incorrect additions of Mg treatment, lack of an extra slag removal station and finally turbulence as the melt were poured into the mould. At Global Castings Guldsmedshyttan AB a greater part of the main shafts containing dross defects were a result of worn out ladles and low melt temperatures. The types of dross found in the main shaft material were mainly Mg, Ca, Si and Al which had reacted with O. S bonded with Mg and Ca was also detected in the dross formations. It was shown that the dross particles could be derived from charge material, Mg treatment and inoculation. To avoid dross defects the first step would be to set up an extra slag station, shorten the interval of maintenance of the ladles and to better adjust the melt temperature to the condition of the specific ladle. To minimize dross due to excess Mg a better controlled process would be recommended with an increased number of monitored manufacturing parameters.Studien av dross i axlar tillverkade av segjärn gjordes hos Global Castings Guldsmedshyttan AB och presenteras i denna examensrapport. Syftet med studien var att hitta anledningar till varför drossdefekter bildas i flänsen på vissa av gjuteriets tillverkade axlar. Drossens kemiska komposition likväl de steg i tillverkningsprocessen som inverkade på drossbildning var av intresse. Studien inkluderade endast drossdefekter i axlar tillverkade av Global Castings Guldsmedshyttan AB. Drosspartiklas bildas när till exempel Mg, Ca, Si och Mg reagerar med O. Dessa ämnen, vilka är väldigt reaktiva med syre, används vid framställning av segjärn för att de sfäriska grafitnodulerna som starkt reglerar materialets duktila egenskaper ska bildas. Ett större antal drosspartiklar i en smälta leder till kluster av dross vilka växer i takt med att nya partiklar bildas. Dross fungerar som sprickinitieringspunkter i gjutgodsytor och reducerar godsets utmattningshållfasthet och duktilitet. Under studien kunde det ses att dross bildas på grund av en kombination av parametrar som ökar smältans exponering av syre vilket resulterar i drossdefekter. Drossdefekter kunde kopplas till slitna skänkar, låga smälttemperaturer, felaktig mängd magnesiumbehandling, brist på en extra slaggstation och slutligen turbulens när smätan hälls i formen. Hos Global Castings Guldsmedshyttan AB är en stor del av axlarna med drossdefekter ett resultat av framför allt slitna skänkar och låga smälttemperaturer. Vid analys sågs det att ett antal olika typer av drosspartiklar kan bildas i det duktila gjutjärn som används till axlarna; främst Mg, Ca, Si och Al som reagerat med O. Mg och Ca som bundit med S kunde också hittas i vissa av de studerade drossformationerna. Det kunde visas att den kemiska kompositionen i drosspartiklarna var härrörande från grundmaterialet, magnesiumbehandlingen och ympmedlet. Ett första steg Global Castings Guldsmedshyttan AB skulle kunna ta för att undvika drossdefekter är att ha en extra slaggstation, införa tätare underhåll av skänkarna och bättre anpassa smälttemperaturen till skicket på den specifika skänken. För att minimera dross som bildats på grund av ett överskott av Mg skulle en mer kontrollerad process rekommenderas med ett ökat antal bevakade tillverkningsparametrar.
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Cheng, Chu-Lin. "Permeation of organic compounds through ductile iron pipe gaskets." [Ames, Iowa : Iowa State University], 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3369820.
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Zambrano, Habib. "Fatigue Assessment of Notches and Cracks in Ductile Cast Iron." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for produktutvikling og materialer, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-14632.
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The steadily increasing use of ductile cast iron and the necessity for building larger cast components present new challenges to the designers. In despite of large cast components are designed adhered to standards, unexpected failure sometime occurs. One reason is the inevitable manufacturing defects containing within the cast components that behave like cracks under cyclic loading. In addition the probability of a large defect to be situated at a critical region of the component increases with the size. Another reason is the effect of geometric discontinuities such as holes, threads and fillets, which are part unavoidable of the designs. These discontinuities that are usually called notches disturb the stress field and cause high local stress concentration. Thus dealing with these severe stress risers (defects and notches) is not an easy task. Therefore most designers resort to use very high and unnecessary safety factors.
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Kasvayee, Keivan Amiri. "Microstructure and deformation behaviour of ductile iron under tensile loading." Licentiate thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH. Forskningsmiljö Material och tillverkning – Gjutning, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-28335.
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The current thesis focuses on the deformation behaviour and strain distribution in the microstructure of ductile iron during tensile loading. Utilizing Digital Image Correlation (DIC) and in-situ tensile test under optical microscope, a method was developed to measure high resolution strain in microstructural constitutes. In this method, a pit etching procedure was applied to generate a random speckle pattern for DIC measurement. The method was validated by benchmarking the measured properties with the material’s standard properties. Using DIC, strain maps in the microstructure of the ductile iron were measured, which showed a high level of heterogeneity even during elastic deformation. The early micro-cracks were initiated around graphite particles, where the highest amount of local strain was detected. Local strain at the onset of the micro-cracks were measured. It was observed that the micro-cracks were initiated above a threshold strain level, but with a large variation in the overall strain. A continuum Finite Element (FE) model containing a physical length scale was developed to predict strain on the microstructure of ductile iron. The materials parameters for this model were calculated by optimization, utilizing Ramberg-Osgood equation. For benchmarking, the predicted strain maps were compared to the strain maps measured by DIC, both qualitatively and quantitatively. The DIC and simulation strain maps conformed to a large extent resulting in the validation of the model in micro-scale level. Furthermore, the results obtained from the in-situ tensile test were compared to a FE-model which compromised cohesive elements to enable cracking. The stress-strain curve prediction of the FE simulation showed a good agreement with the stress-strain curve that was measured from the experiment. The cohesive model was able to accurately capture the main trends of microscale deformation such as localized elastic and plastic deformation and micro-crack initiation and propagation.
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Fordyce, E. P. "The unlubricated sliding wear behaviour of austempered ductile irons." Master's thesis, University of Cape Town, 1989. http://hdl.handle.net/11427/21955.
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Bibliography: pages 85-89.A study has been made of the unlubricated sliding wear behaviour of austempered ductile irons under conditions of sliding velocity and load. The load was varied between 0.9 and 2.8 MPa, whilst the sliding velocity range was between 0.5 and 2.0 ms⁻¹. Two commercial grades of spheroidal graphite irons, SG42 and SG60 were austempered between 250⁰C and 400⁰C. A distinction in the wear behaviour was found with metallic type wear dominating at the lower sliding velocities and an oxidative type wear being evident at the higher sliding velocities. It was however found that an increase in the load resulted in an earlier onset of the oxidative type wear regime, for a specific sliding velocity. On austempering these spheroidal graphite irons the mechanical properties as well as the sliding wear resistance increased dramatically. Furthermore, the austempered irons' outperformed a series of steels of much higher hardness by factors between 2 and 28 times under the same conditions. At the lower velocity of testing the outstanding wear resistance is attributed to the austempered iron's unique microstructure of acicular ferrite and retained austenite and a partial transformation of austenite to martensite. However, at the higher sliding velocity the exceptional wear resistance is derived from a development of an tribologically protective oxide film together with the formation of a hardened white layer. The development of the work hardened layer is linked to the high carbon in the matrix of these irons. The work hardened layer leads to a similar wear rate prevailing for all irons austempered from a specific parent iron. The synergism of variation in load, sliding velocity and wear counterface together with the effect of initial microstructure has been explain in terms of simple wear models.
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Zahiri, Saden H. (Saden Heshmatollah) 1966. "Prediction of the processing window and austemperability for austempered ductile iron." Monash University, School of Physics and Materials Engineering, 2002. http://arrow.monash.edu.au/hdl/1959.1/8408.
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Hoffman, John Mark. "Zinc coatings for the external protection of ductile iron water mains." Thesis, University of Manchester, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.279981.
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Stokes, Ben. "Fatigue analysis of austempered ductile iron suitable for automotive camshaft applications." Thesis, University of Southampton, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288156.
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Jonzon, Andreas. "Characterization of High-silicon alloy ductile iron in very thick sections." Thesis, Luleå tekniska universitet, Mineralteknik och metallurgi, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-79194.
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Valmet AB has ha foundry located I Karlstad, Sweden. The foundry has specialized in large components in ductile and gray iron. This report is a part of an evaluation of a new alloy that Valmet has produced. The alloy is called S550 where 550 is the expected tensile strength in a cast on sample. S550 is a ferritic ductile alloy with 4,15-4,25% silicone. In this experiment the alloy is casted in very large sections to better match the intended final product. The purpose of the report is to promote a better understanding of how silicon works in large castings. Ultimate tensile strength, yield strength and elongation will be measured. The microstructure will be mapped and described. This as a step to ensure that the material is ready to use to produce castings in large dimensions. In the experiment, the microstructure is examined from 3 charges. Mechanical properties are collected from the 3 charges by widened specimens from 3 details of 2785 kg/piece and 4 drilled samples from 4 details about 600 kg/piece. The samples are processed to test bars according to standard SS-EN1563: 2012. Thereafter the rods are dragged in a tensile testing machine to collect data. The microstructure is mapped through light optic microscopy. The samples where machined according to SS-EN1563:2012. Tensile testing machine was used to record the mechanical values. Microstructure was mapped using a light-optic microscope. The material achieved a tensile strength of 544 MPa on average which is below the expected value. The yield strength was 436 MPa in average. The material shows low dispersion, mainly in fracture limit and yield limit. The elongation in average 12.8% varied in the different geometries but with lower variations within the same geometry. The alloy got better mechanical values on Detail B that had a shorter cooling time. In Detail A, micro porosity and slag were found which adversely affected their mechanical properties. The ground mass is considered as ferritic. The graphite nodes had a size of 82μm and a nodule density of 75 nodules / mm2. Most nodules had graphite form VI, small amount of graphite V and III have been found. No degenerated graphite forms as chunky or exploded graphite has been found.
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Sa, Andre Ricardo de Souza e. "Influência do alumínio nas propriedades mecânicas do ADI (Austempered Ductile Iron)." Universidade Federal de Minas Gerais, 2004. http://hdl.handle.net/1843/BUOS-8DQE8A.
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The ADI (Austempered Ductile Iron), a cast iron obtained after the proper heat treatment of regular sheroidal graphite iron, has been intensely studied in the last years. Silicon is the standard element added for graphitization of the alloy. In this study it was replaced by aluminium, an element know as presenting a similar chemical behavior in the alloy. Themelting procedure was the same as the used in the production of the standard ADI-Si. The aluminium content, replacing part of the silicon, were 0,75; 2,26 and 2,99% Al. The austempering temperatures were 270, 320, 370°C. The testing specimens were obtained according ASTM A 897 and regular tensile and hardness tests were used to determine the mechanical properties of the alloy with non-reacted austenite and carbide precipitation. The mechanical properties degenerated, accordingly, establishing the need of the use of a special melting procedure when dealing with this Al-bearing alloy.O ADI (Austempered Ductile Iron), produzido pelo tratamento de austêmpera de um ferro fundido nodular, vem sendo desenvolvido e estudado nos últimos anos tendo o silício como elemento grafitizante e portanto, como o segundo principal elemento de liga, definidor da liga. Este trabalho, no entanto, contemplou estudar as propriedades mecânicas do ADI (L.R., L.E., dureza e alongamento) utilizando o alumínio em substituição ao silício como elemento grafitizante. Foram realizados experimentos com adições de 0,75; 2,26 e 2,99% Al. A fusão foi realizada segundo os procedimentos usuais para obtenção do ADI-Si. Os tratamentos térmicos foram feitos em três temperaturas: 270, 320, 370°C. Os corpos de prova foram obtidos segundo norma ASTM A 897. Verificou-se que o alumínio causou a deterioração progressiva da grafita, o aumento da quantidade de austenita não reagida e a precipitação de carbonetos. Consequentemente, as propriedades mecânicas, de resistência e ductilidade, se deterioraram, indicando a necessidade de cuidados especiais na fusão do material.
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Taivalkoski, Olivia. "Evaluation of material properties after laser welding on ductile cast iron." Thesis, KTH, Materialvetenskap, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-254653.
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Scania wants to lower the weight of their trucks, including the goal to reduce the carbon dioxide emissions, and one way to do that is to use laser welding instead of fastenings.This bachelor thesis work is about laser welding of ductile cast iron, or spheroidal graphite cast iron or nodular cast iron, to QT-steels and case hardening steel and evaluation of the mechanical properties of the weld. Also laser welding of cast steel to the same two materials are being evaluated in this work. Tests are done to evaluate the effect on the material from laser welding. The tests are tensile tests and Vickers hardness test; both across and along the weld and in some areas of interest. EDS (Energy Dispersive X-Ray Spectroscopy) is used to analyze the composition in the weld and light optical microscope is used to look at the fusion zone (FZ) and the heat affected zone (HAZ). The results shows that the hardness is high in the heat affected zone due to the formation of martensite and that the materials mix more towards the root of the weld. The materials also mix more if the weld depth is deeper. The width of the heat affected zone seems to be longer if the heat input is higher. It is also clear that welding of cast steel is less complicated than the welding of ductile cast iron. That is because ductile cast iron gets a hard and brittle heat affected zone (HAZ) while the cast steel does not. The cast steel can also be welded without filler wire without getting to hard or to brittle. If laser welding is to be used in the future the component should be constructed in such a way that the fusion zone is not carrying the main load. Tests on fatigue strength should also first be done on a finished component as it cannot be tested on the samples in this work. This work was conducted at Scania AB and the royal institute of technology, KTH, in Sweden.Scania vill sänka vikten på sina lastbilar, bland annat för att minska utsläppen av koldioxid, och ett sätt att göra det är att lasersvetsa istället för att använda bultar. Detta kandidatexamensarbete handlar om lasersvetsning av segjärn, eller nodulärt gjutjärn som det också kallas, till seghärdningsstål och sätthärdningsstål samt utvärdering av svetsens mekaniska egenskaper. Även lasersvetsning av gjutstål till samma stålsorter som ovan utvärderas i detta arbete.Tester görs för att utvärdera effekten på materialet från lasersvetsningen. Testerna är dragprov och Vickers hårdhetstestning; både tvärs över och längs med svetsen samt även i vissa områden av särskilt intresse. EDS (Energy Dispersive X-Ray Spectroscopy) används för att analysera sammansättningen i svetsen och ljusoptiskt mikroskop används för att se svetsgodset och den värmepåverkade zonen. Resultaten visar att hårdheten går upp i den värmepåverkade zonen på grund av martensit bildning och att materialen blandar sig mer närmare svetsroten. Materialen blandar sig också mer om svetsdjupet är djupare. Den värmepåverkade zonens bredd verkar vara större om sträckenergin är hög. Det står också klart att svetsning av gjutstål är mindre komplicerat än svetsning av segjärn eftersom segjärnet får en hög hårdhet i den värmepåverkade zonen medan det inte alls blir så för gjutstålet. Gjutstålet kunde också svetsas utan tillsatsmaterial utan att få ett för hårt eller sprött svetsgods. Om man vill använda lasersvetsning i framtiden ska komponenter konstrueras så att svetsen inte bär huvudvikten eftersom resultatet visar att svetsgodset får lägre brottgräns. Utmattningstester borde också göras på en färdig komponent eftersom det inte kan testas på proven från det här arbetet. Detta arbete utfördes på Scania AB och Kungliga Tekniska Högskolan, KTH, i Sverige.
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Ozcan, Alper. "The Effect Of Sn Content And Isothermal Transformation Temperature On The Mechanical Properties Of Austempered Ductile Cast Iron." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/1055359/index.pdf.
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In this study the effects of Sn content and isothermal transformation temperature on the ultimate tensile strength (UTS), elongation and hardness of austempered ductile cast iron (ADI) was investigated. To determine the possible effect of Sn on these properties the Sn content of standard GGG30, GGG40 and GGG50 materials were taken as reference, whose chemical compositions vary from 0,016 to 0,050% in terms of Sn. However the Sn content was increased to a maximum of 0,26% for investigating the effect of Sn on mechanical properties. The test specimens were obtained from standard 1-in Y-blocks and austenitized at 925oC for 1 hour and austempered at 350oC,375oC, 400oC and 420oC for 60 minutes in a salt bath.
Microstructural examination of the specimens were also done. To determine the amount of retained austenite of the specimens X-Ray analyses were used. As a result of the study The UTS increases up to 0,1% Sn and then levels off. A similar behavior is observed in the variation of hardness. Percent elongation decreases and falls to a minimum around 0,1% Sn, from this point on, a slight increase is observed. Strength and hardness increase while percent elongation decreases with decreasing temperatures.
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Santos, Daniel dos [Verfasser]. "Development of an alloyed high yield ductile iron -HYDI- / Daniel dos Santos." Aachen : Shaker, 2010. http://d-nb.info/1080766847/34.
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Kasvayee, Keivan Amiri. "On the deformation behavior and cracking of ductile iron; effect of microstructure." Doctoral thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH, Material och tillverkning, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-36852.
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This thesis focuses on the effect of microstructural variation on the mechanical properties and deformation behavior of ductile iron. To research and determine these effects, two grades of ductile iron, (i) GJS-500-7 and (ii) high silicon GJS-500-14, were cast in a geometry containing several plates with different section thicknesses in order to produce microstructural variation. Microstructural investigations as well as tensile and hardness tests were performed on the casting plates. The results revealed higher ferrite fraction, graphite particle count, and yield strength in the high silicon GJS-500-14 grade compared to the GJS-500-7 grade. To study the relationship between the microstructural variation and tensile behavior on macroscale, tensile stress-strain response was characterized using the Ludwigson equation. The obtained tensile properties were modeled, based on the microstructural characteristics, using multiple linear regression and analysis of variance (ANOVA). The models showed that silicon content, graphite particle count, ferrite fraction, and fraction of porosity are the major contributing factors that influence tensile behavior. The models were entered into a casting process simulation software, and the simulated microstructure and tensile properties were validated using the experimental data. This enabled the opportunity to predict tensile properties of cast components with similar microstructural characteristics. To investigate deformation behavior on micro-scale, a method was developed to quantitatively measure strain in the microstructure, utilizing the digital image correlation (DIC) technique together with in-situ tensile testing. In this method, a pit-etching procedure was developed to generate a random speckle pattern, enabling DIC strain measurement to be conducted in the matrix and the area between the graphite particles. The method was validated by benchmarking the measured yield strength with the material’s standard yield strength. The microstructural deformation behavior under tensile loading was characterized. During elastic deformation, strain mapping revealed a heterogeneous strain distribution in the microstructure, as well as shear bands that formed between graphite particles. The crack was initiated at the stress ranges in which a kink occurred in the tensile curve, indicating the dissipation of energy during both plastic deformation and crack initiation. A large amount of strain localization was measured at the onset of the micro-cracks on the strain maps. The micro-cracks were initiated at local strain levels higher than 2%, suggesting a threshold level of strain required for micro-crack initiation. A continuum Finite Element (FE) model containing a physical length scale was developed to predict strain on the microstructure of ductile iron. The material parameters for this model were calculated by optimization, utilizing the Ramberg-Osgood equation. The predicted strain maps were compared to the strain maps measured by DIC, both qualitatively and quantitatively. To a large extent, the strain maps were in agreement, resulting in the validation of the model on micro-scale. In order to perform a micro-scale characterization of dynamic deformation behavior, local strain distribution on the microstructure was studied by performing in-situ cyclic tests using a scanning electron microscope (SEM). A novel method, based on the focused ion beam (FIB) milling, was developed to generate a speckle pattern on the microstructure of the ferritic ductile iron (GJS-500-14 grade) to enable quantitative DIC strain measurement to be performed. The results showed that the maximum strain concentration occurred in the vicinity of the micro-cracks, particularly ahead of the micro-crack tip.Denna avhandling fokuserar på effekten av variationer i mikrostrukturen på mekaniska egenskaper och deformationsbeteende hos segjärn. För att undersöka dessa effekter, två olika sorter av segjärn, (i) GJS-500-7 och (ii) högkisellegerad GJS-500-14, gjutits till plattor av olika tjocklekar för att generera mikrostrukturvariationen. Mikrostrukturundersökning, samt drag- och hårdhetsprov gjordes på de gjutna plattorna. Resultaten visade att en högre ferritfraktion, grafitpartikelantal och sträckgräns i den högkisellegerade GJS-500-14-sorten jämfört med GJS-500-7. För att studera förhållandet mellan mikrostrukturell variation och spännings-töjningsbeteendet på makroskala, modellerades detta med hjälp av Ludwigson-ekvationen. De erhållna spännings-töjningsegenskaperna modellerades baserat på mikrostrukturell karaktäristika genom multipel linjärregression och variansanalys (ANOVA). Modellerna visade att kiselhalt, grafitpartikelantal, ferritfraktion och porfraktion var de viktigaste bidragande faktorerna. Modellerna implementerades i ett simuleringsprogram för gjutningsprocessen. Resultatet från simuleringen validerades med hjälp av experimentella data som inte ingick i underlaget för regressionsanalysen. Detta möjliggjorde att prediktera spännings-töjningsbeteendet och dess variation hos gjutna segjärns komponenter med liknande sammansättning och gjutna tjocklekar som användes i denna studie. För att kunna undersöka deformationsbeteendet på mikroskala utvecklades en metod för kvantitativ mätning av töjning i mikrostrukturen, genom DIC-tekniken (digital image correlation) tillsammans med in-situ dragprovning. I denna metod utvecklades en grop-etsningsprocess för att generera ett slumpvis prickmönster, vilket möjliggjorde DIC-töjningsmätning i matrisen och i området mellan grafitpartiklarna med tillräcklig upplösning. Metoden validerades genom benchmarking av den uppmätta sträckgränsen mot materialets makroskopiska sträckgräns mätt med konventionell dragprovning. Det mikrostrukturella deformationsbeteendet under dragbelastning karakteriserades. Under elastisk deformation avslöjade töjningsmönstret en heterogen töjningsfördelning i mikrostrukturen, och bildandet av skjuvband mellan grafitpartiklar. Sprickbildning initierades vid låg spänning och redan vid de spänningsnivåer som ligger vis ”knät” på dragprovningskurvan, vilket indikerar energidissipering genom både begynnande plastisk deformation och sprickbildning. Den lokala töjningen vis sprickinitiering skedde då den lokala töjningen översteg 2%, vilket indikerar att detta skulle kunna vara en tröskelnivå för den töjning som erfordras för initiering av mikro-sprickor. En kontinuum Finita Element (FE) modell utvecklades för att prediktera töjningen hos ett segjärn och dess fördelning i segjärns mikrostruktur. Materialparametrarna för denna modell optimerades genom att anpassa parametrarna i Ramberg-Osgood ekvationen. De predikterade töjningsfördelningarna jämfördes med de experimentell uppmätta töjningsmönstren uppmätta med DIC, både kvalitativt och kvantitativt. Töjningsmönstren överensstämde i stor utsträckning, vilket resulterade i att modellerna kunde anses vara validerade på mikronivå. För att kunna mäta töjningsmönster under dynamiska förlopp på mikronivå utvecklades en metod för att skapa prickmönster och att utföra in-situ CT provning i ett svepeletronmikroskop (SEM). Prickmönstret skapades genom avverkning med en fokuserad jonstråle (FIB), och provades på det ferritiska segjärnet (GJS-500-14 grad). Resultaten visade att maximal töjningskoncentration fanns i närheten av mikrosprickorna, framförallt framför sprickspetsen.
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Almaari, Firas, and Essam Aljbban. "Strain Rate Effect on Fracture Mechanical Properties of Ferritic-Pearlitic Ductile Iron." Thesis, Linnéuniversitetet, Institutionen för byggteknik (BY), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-78858.
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This study investigates the effect of strain rate on fracture properties of Ferritic-Pearlitic Ductile Iron. A series of dynamic three point bending tests, with various load application rates, are conducted on Charpy V-notch specimens, in room temperature and approximately -18 °C. The tests are performed in a custom-made fixture and during the tests, force and displacement data are recorded. A XFEM (Extended Finite Element Method) model of the test setup has been established and material data from the tests are used as input to the model. The test results show a strong dependency of the strain rate regarding the force needed for crack initiation. Moreover, it can be concluded that low temperature makes the material very brittle, even at low load application rates.
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Ekström, Madeleine. "Development of a ferritic ductile cast iron for improved life in exhaust applications." Licentiate thesis, KTH, Mekanisk metallografi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-122006.
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Due to coming emission legislations, the temperature is expected to increase in heavy-duty diesel engines, specifically in the hot-end of the exhaust system affecting components, such as exhaust- and turbo manifolds. Since the current material in the turbo manifold, a ductile cast iron named SiMo51, is operating close to its limits there is a need for material development in order to maintain a high durability of these components. When designing for increased life, many material properties need to be considered, for example, creep-, corrosion- and fatigue resistance. Among these, the present work focuses on the latter two up to 800°C improving the current material by additions of Cr, for corrosion resistance, and Ni, for mechanical properties. The results show improved high-temperature corrosion resistance in air from 0.5 and 1wt% Cr additions resulting in improved barrier layer at the oxide/metal interface. However, during oxidation in exhaust-gases, which is a much more demanding environment compared to air, such improvement could not be observed. Addition of 1wt% Ni was found to increase the fatigue life up to 250°C, resulting from solution strengthening of the ferritic matrix. However, Ni was also found to increase the oxidation rates, as no continuous SiO2-barrier layers were formed in the presence of Ni. Since none of the tested alloys showed improved material properties in exhaust gases at high temperature, it is suggested that the way of improving performance of exhaust manifolds is to move towards austenitic ductile cast irons or cast stainless steels. One alloy showing good high-temperature oxidation properties in exhaust atmospheres is an austenitic cast stainless steel named HK30. This alloy formed adherent oxide scales during oxidation at 900°C in gas mixtures of 5%O2-10%H2O-85%N2 and 5%CO2-10%H2O-85%N2 and in air. In the two latter atmospheres, compact scales of (Cr, Mn)-spinel and Cr2O3 were formed whereas in the atmosphere containing 5%O2 and 10%H2O, the scales were more porous due to increased Fe-oxide formation. Despite the formation of a protective, i.e. compact and adherent, oxide scale on HK30, exposure to exhaust-gas condensate showed a detrimental effect in form of oxide spallation and metal release. Thus, proving the importance of taking exhaust-gas condensation, which may occur during cold-start or upon cooling of the engine, into account when selecting a new material for exhaust manifolds.QC 20130508
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Goldberg, Moshe. "Machinability research into the mechanics and surface integrity characteristics of austempered ductile iron." Thesis, Southampton Solent University, 2002. http://ssudl.solent.ac.uk/621/.
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Meyer, Nicholas. "Effects of Mean Stress and Stress Concentration on Fatigue Behavior of Ductile Iron." University of Toledo / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1418332368.
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Alp, Yunus Abbas Hassan H. "Combined flexural and cable-like behavior of ductile steel beams." Auburn, Ala, 2009. http://hdl.handle.net/10415/1902.
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Montenegro, Davi Melo. "An analysis of the machinability of ASTM grades 2 and 3 austempered ductile iron." Instituto Tecnológico de Aeronáutica, 2011. http://www.bd.bibl.ita.br/tde_busca/arquivo.php?codArquivo=1943.
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Austempered Ductile Iron (ADI) is a ferrous material that was first fabricated in the second half of last century, therefore a relatively new material compared to steel, which has been used for different applications by mankind for some millennia now. ADI';s mechanical properties, such as its strength-to-weight ratio, which has proven to outperform that of forged steel by up to 10%, are very suitable for structural applications, such as connecting rods, crankshafts, and heavy farm machinery among others. The main goal of this work is to perform an analysis of the machinability of two ASTM grades of ADI, namely 2 and 3. The samples used in this work were cast and austempered according to ASTM standards for the production of grade 2 (G2) and grade 3 (G3) ADI. Characterization was accomplished through tensile and hardness tests, metallography and X-ray diffraction. Machinability was evaluated by analyzing tool life, cutting forces, surface finish and chip characteristics in turning operations. A quick-stop test was also performed. Tool life when machining G2 was 33% lower than G3, although the latter is a harder material. Abrasion and adhesion were the wear mechanisms observed through SEM images, whereas in other cast irons mainly abrasion is observed. Cutting forces measurements showed that the value of Kc1,1 decreased 19%, from 1448 to 1175N/mm2, for G2 as the depth of cut increased from 2 to 5mm at a cutting speed of 80m/min and 18%, from 1501 to 1236N/mm2, for G3. Surface roughness measurements proved that a smoother surface is obtained for both alloys at f = 0.10mm/rev when using an insert with nose radius 1.6mm instead of smaller radii. Both alloys presented similar surface quality. All chips observed were segmented.
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Boonmee, Sarum. "Ductile and Compacted Graphite Iron Casting Skin - Evaluation, Effect on Fatigue Strength and Elimination." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1364310320.
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Malatin, Richard. "Využití termické analýzy litin pro predikci kvality odlitků numerickou simulaci." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2018. http://www.nusl.cz/ntk/nusl-387734.
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This work deals with problem of analyzing cooling curves of ductile iron and discovering possibility to predict shrinkage tendency of melt from thermal analysis results. This work was executed in foundry production conditions where obtained data from thermal analysis data linked to experimental castings where amount of shrinkage was estimated. Data were analyzed and looked for correlations between acquired thermal data and shrinkage defects.
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"Ductile white cast iron." 2008. http://library.cuhk.edu.hk/record=b5896770.
Full textAbstract:
Ho, Ching Man = 可柔韌的白鑄鐵 / 何靜雯.Thesis submitted in: November 2007.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2008.
Includes bibliographical references (leaves ).
Text in English; abstracts in English and Chinese.
Ho, Ching Man = Ke rou ren de bai zhu tie / He Jingwen.
Chapter Chapter 1: --- Introduction --- p.1
Chapter 1.1 --- Introduction of Composites --- p.1
Chapter 1.1.1 --- Dispersion-Strengthened composites --- p.2
Chapter 1.1.2 --- True Particulate Composites --- p.2
Chapter 1.1.3 --- Fiber-Reinforced Composites --- p.2
Chapter 1.1.4 --- Laminar Composites --- p.3
Chapter 1.2 --- Mechanical Properties of Metal Matrix Composites --- p.4
Chapter 1.2.1 --- Stress-Strain Test --- p.4
Chapter 1.2.2 --- "Stiffness, Strength and Ductility" --- p.4
Chapter 1.2.3 --- Hardness --- p.5
Chapter 1.3 --- Fabrication of Metal Matrix Composites --- p.5
Chapter 1.3.1 --- Liquid ´ؤ´ؤ State Processing --- p.6
Chapter 1.3.1.1 --- Infiltration Processes --- p.6
Chapter 1.3.1.2 --- Dispersion Processes --- p.7
Chapter 1.3.1.3 --- Spray Processes --- p.7
Chapter 1.3.1.4 --- In - Situ Processes --- p.8
Chapter 1.3.2 --- Solid - State Processing --- p.8
Chapter 1.3.2.1 --- Diffusion Bonding --- p.8
Chapter 1.3.2.2 --- Deformation Processing --- p.9
Chapter 1.3.2.3 --- Deposition Techniques --- p.9
Chapter 1.4 --- Fabrication of Metal Matrix Composites by Spinodal Decomposition --- p.10
Chapter 1.4.1 --- Phase Transformation --- p.10
Chapter 1.4.2 --- Nucleation and Growth --- p.12
Chapter 1.4.2.1 --- Kinetics of Nucleation and Growth --- p.12
Chapter 1.4.2.2 --- Phase Separation by Nucleation and Growth --- p.14
Chapter 1.4.3 --- Spinodal Decomposition --- p.14
Chapter 1.4.3.1 --- Phase Separation by Spinodal Decomposition --- p.14
Chapter 1.4.3.2 --- The Diffusion Equation for Spinodal Decomposition --- p.15
Chapter 1.4.4 --- Methods to obtain large undercooling --- p.17
Chapter 1.5 --- Aim of This Project --- p.18
Chapter Chapter 2: --- Experimental --- p.26
Chapter 2.1 --- Preparation of fused silica tube --- p.26
Chapter 2.2 --- Preparation of Sample --- p.26
Chapter 2.2.1 --- Weighing and Alloying --- p.26
Chapter 2.2.2 --- Fluxing --- p.27
Chapter 2.3 --- Slow Cooling --- p.28
Chapter 2.4 --- Microstructure Analysis --- p.28
Chapter 2.4.1 --- Optical Microscope (OM) Analysis --- p.28
Chapter 2.4.2 --- Sample Preparation for Scanning Electron Microscope (SEM) Analysis --- p.29
Chapter 2.4.3 --- Sample Preparation for Transmission Electron Microscope (TEM) Analysis --- p.29
Chapter 2.4.3.1 --- Specimen Requirement --- p.29
Chapter 2.4.3.2 --- "Cutting, Grinding and Polishing" --- p.30
Chapter 2.4.3.3 --- Ion Milling --- p.31
Chapter 2.5 --- Microstructure Characterization by TEM --- p.31
Chapter 2.5.1 --- Indexing Diffraction Pattern --- p.31
Chapter 2.5.2 --- Energy Dispersive X-Rav (EDX) Analysis --- p.32
Chapter 2.6 --- Mechanical Properties --- p.33
Chapter 2.6.1 --- Hardness Testing --- p.33
Chapter 2.6.2 --- Compression Testing --- p.33
Chapter 2.7 --- Characterizations of Non-spinodal Samples --- p.34
Chapter Chapter 3: --- Study of the Relationship between Microstructures and Undercooling of Fe81C14Si5 --- p.41
Chapter 3.1 --- Abstract --- p.41
Chapter 3.2 --- Introduction --- p.42
Chapter 3.3 --- Experiment --- p.42
Chapter 3.4 --- Results --- p.44
Chapter 3.5 --- Discussion --- p.46
Chapter 3.6 --- Conclusion --- p.46
Chapter Chapter 4: --- Ductile white cast iron --- p.56
Chapter 4.1 --- Abstract --- p.56
Chapter 4.2 --- Introduction --- p.57
Chapter 4.3 --- Experimental --- p.58
Chapter 4.4 --- Results --- p.60
Chapter 4.5 --- Discussions --- p.66
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Nandagopal, Palaniswamy Naidu. "Graphite pretreatment of ductile iron." 1986. http://catalog.hathitrust.org/api/volumes/oclc/14923412.html.
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Thesis (M.S.)--University of Wisconsin--Madison, 1986.Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 62-65).
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Chen, Bi-Ting, and 陳碧亭. "Microstructure of Intercritical Austempered Ductile Iron." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/4tsmrw.
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碩士國立臺北科技大學
材料科學與工程研究所
99
The current study investigates the influences of intercritical austenitizing temperatures on microstructures and mechanical properties of austempered ductile irons. A series of intercritical austenitizing temperatures ranging from 775 to 900°C are used and austempering is performed at 400°C on a conventional FCD700 ductile iron. Experimental results show that mechanical properties, including strength, ductility, and the toughness, all increase with intercritical austenitizing temperatures till an optimum austenitizing temperature of 830°C. At this optimum processing condition, strength of 974 MPa, impact energy of 166 J, and 16.4% ductility is achieved. These properties are much higher than non-treated ductile iron with 790 MPa strength, 42 J impact energy, and 8.2% ductility. The 830°C austenitized and 400°C austempered microstructure consists of 8% proeutectoid ferrite and 27% retained austenite. The uniform distribution of refined ausferrite grains is responsible for the increase of overall strength. Furthermore, nano-size martensitic transformation induced by plastic strain can be observed via TEM inside the blocky type retained austenite. The increased carbon content, adequate size and distribution of retained austenite combine to increase toughness through martensitic transformation giving rise to transformation induced plasticity (TRIP) effect.
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Chang, M. C., and 張明哲. "Cutting Properties of Austempered Ductile Iron." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/13488315145063896767.
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Lin, Zong-Ching, and 林宗慶. "Casting Simulation of Ductile Iron Exhaust Manifold." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/9jtc9f.
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碩士國立臺北科技大學
材料科學與工程研究所
99
In recent years, high quality automobile parts are demanded in the highly developed and sophisticated car industry. Especially for safety concerns, these parts not only require light weight and high strength but also have to be defect free. Exhaust manifold is one of high quality demanding parts which is made of ductile iron. The ductile irons are known to bear detrimental oxide defect formed by oxidation of Mg and Ce containing nodulizing agents when contacting with air. It is important to understand the formation of oxide defect in casting of complex castings such as exhaust manifold. . In this study, the casting process of a ductile iron exhaust manifold is computationally simulated. Influence of flow pattern is discussed in to understand the formation of possible defects. Simulation results show that the distribution of oxides in the mold cavity is not only affected by temperature of liquid metal but also affected by the flow pattern. The flow pattern in one location of the mold cavity sometimes is affected by flow streams from multiple directions. An inappropriate flow pattern design can result in the entrapment of oxide films which cause the degradation of casting quality. In contrast, a suitable flow pattern results in steady flow filling of the runner system sequentially and during the casting process. A high quality part without oxide defects could be produced. Therefore, flow pattern design during casting should be taken into consideration for improvement in complex casting quality.
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Chou, Jaw-Min, and 周兆民. "Austenitic Transformation in Ferritic Ductile Cast Iron." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/54515720878251638679.
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ZHONG, JI-YUAN, and 鍾吉垣. "Surface Remelt of Ductile Iron Using GTAW." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/93508843958155987232.
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碩士中州科技大學
機械與自動化工程系
104
Surface remelt of welding the as-cast ductile iron by using of the semi-automatic gas tungsten arc-welding (GTAW) machine in different energy input. Phase transformation and mechanical properties changing for weldment of ductile iron were observed and analyzes mutually in fusion zone and heat affected zone in matrix. Comput model of the ductile iron welding bead of thermal cycles, isotherms, and peak temperature locus for the influence of the welding parameters will upon the welding heat input. This governing equation is base on the "Rosenthal's analytical solution for three–dimensional heat flow during welding" to model the bead thermal distribution. Moreover, comparing the experimental data and the value of computer modeling welding bead results physically, to inquire heat input the welding bead conductivity and temperature distribution of the problem.
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TSAI, FENG-CHING, and 蔡豐慶. "Study on Aluminization of Austempered Ductile Iron." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/14586714244297276209.
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碩士國立高雄應用科技大學
模具工程系
105
In this paper, the austempered ductile iron(ADI) was used as a substrate and aluminized at 900 ℃ to aluminized layer on the ADI for increasing hardness, corrosion resistance, and antioxidant at high temperature. Since the aluminized treatment make the ADI restore to tradiction dutile iron, the austempered treatment was applied. It was not only possessed the property of ADI but also improved the oxidation at high temperature.
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Gao, Ming-Shiung, and 高銘祥. "The Repeat Heat Treatment of Austempered Ductile Iron." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/77461628721543139363.
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Feng, Hui-Ping, and 馮慧平. "Study on Fracture Toughness of Austempered Ductile Iron." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/29598386444377039351.
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博士大同工學院
材料工程研究所
87
In this study, applied ductile iron castings in different section size and with/ without Bi alloying addition, we evaluate the effects of mass variation and graphite refinement (with Bi alloying addition) in castings on the fracture toughness of ADI. And applied the compact tensile (CT) specimens of fracture toughness via single-step or two-step austempering heat treatment and testing at the different environmental temperatures (150℃, 25℃, or -150℃), this research is also to investigate the variation of the fracture toughness of ADI. We made three types of ductile iron casting materials, named as material A, B, and C in this experiment. The casting forms of material A (without Bi alloying addition) and material B are the same Y-block of 30, 60, and 115mm section size, which were added alloying elements Cu, Ni, and Mo to enhance their harden-ability to avoid the pearlite formation during austempering heat treatment process. The form of ductile iron material C casting, in T-block with two ends of 35mm and 65mm in thickness, is designed to meet the practical machine parts generally containing different section sizes. The results show the effect of graphite nodule refinement by Bi alloying addition on the plane stain fracture toughness (KIC) is significant, the highest toughness value of 56.0 MPa√m obtained in this study, and only at the very high nodules count of 400 nodules/ mm2 compounded with high ferrite content in the as-cast matrix. Otherwise, the as-cast ferritic-pearlitic ductile iron of thickness from 30 mm to 115 mm possess KIC fracture toughness only within 40~ 46 MPa√m. For KIC fracture toughness and retained austenite of the austempered materials A and B within 30 mm to 115 mm thick casting size, it appeared that because of the homogenization effect from high temperature austenitization (900℃), the specimens after 1~3 hours subsequent austempering did not seem to change the properties too greatly. Conventional single-step austempering of material A, B, and C ductile iron, can obtain a marked increase in the plane strain fracture toughness KIC from 42.7/46.7/38.2 MPa√m of the as-cast material A, B, and C to 64.3/71.3/57.4 MPa√m of the austempered, an improvement over 40%. Two-step austempering of the ductile iron material C yielded the good KIC 77.8 MPa√m , which is close to the KIC 77.3 MPa√m of the ductile iron subjected by a single-step austempered at higher temperature 360℃ and better than the KIC 57.4 MPa√m at lower temperature 300℃. At room temperature the fracture toughness of the mixed ausferrite of two-step austempering is close to that of the upper ausferrite of austempering temperature 360℃, however mixed ausferrite has a higher strength and hardness than those of the upper ausferrite. Therefore, we can conclude that ADI of two-step austempering is a suitable material for machine parts with good strength and fracture toughness. At medium (150℃) and low (-150℃) temperature in this experiment, the microstructures of ADI seem no significant change. However, the KIC of ADI markedly decrease at temperature of -150℃, which might be related to the martensite transformation of the retained austenite in the matrix under lower environmental temperature. Another observation, the fractography of ADI at low temperature generally shows large cleavage facets, which are typical brittle fracture.
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Li, Kuo-kuang, and 李國光. "The Study on Machinability of Austempering Ductile Iron." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/2dehgg.
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碩士國立臺灣科技大學
機械工程系
94
This thesis has been aimed to study the machinability of three types ductile irons including austempered ductile irons treated with two-stage austenitizing, conventional austempered and as-cast ductile irons. In order to analyze the relationship between the machinability with the structure and properties of the irons, the characteristic of microstructures was analyzed and also the testing of mechanical properties of hardness and toughness was conducted. The results of this research show that: (1) The microstructure of austempered ductile irons treated with a second stage low-temperature austeniting within the upper and lower critical temperatures existed a certain among of pro-eutectoid ferrite grains which precipitated along graphite nodular and or grain boundaries; (2) The austempered ductile irons alloying with Ni and Mo and treated with two-stage austenitizing had a microstructure with larger among of pro-eutectoid ferrite grains, and with mechanical properties softer and tougher; (3) In general, the machinability of austempered ductile irons treated with two-stage austenitizing was better than that of which treated with conventional one-stage process.
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陳正中. "The study of austempered ductile iron fatigue characteritic." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/55029565223490715411.
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Oliveira, Carlos Manuel Gomes. "Effect of lanthanum addition in ductile cast iron." Master's thesis, 2013. https://repositorio-aberto.up.pt/handle/10216/89138.
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Gomez, Jorge Ivan. "A study of the forgeability of ductile iron." 1986. http://catalog.hathitrust.org/api/volumes/oclc/15509985.html.
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Thesis (M.S.)--University of Wisconsin--Madison, 1986.Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 80-81).
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Misorski, Christopher John. "Solidification developments in heavy section ductile cast iron." 1988. http://catalog.hathitrust.org/api/volumes/oclc/19034680.html.
Full textAbstract:
Thesis (M.S.)--University of Wisconsin--Madison, 1988.Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 140-148).
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Oliveira, Carlos Manuel Gomes. "Effect of lanthanum addition in ductile cast iron." Dissertação, 2013. https://repositorio-aberto.up.pt/handle/10216/89138.
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SUN, ZHENG-YU, and 孫政郁. "Research and Development of Improved Austempered Ductile Iron." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/um4322.
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呂理得. "A Solidification Simulation of Ductile Iron with Personal Computer." Thesis, 1991. http://ndltd.ncl.edu.tw/handle/98492862205036839385.
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碩士國立臺灣科技大學
工程技術研究所
79
A computer program based on energy conservation and appropriate nucleation and growth models was developed to simulate the solidification of ductile iron. The forward time central spacing algorithm was used. Further, the simulation results are analyzed by comparing with the experimental results. The simplified eutectic cell growth model coupled with proportional nucleation and heterogeneous nucleation respectively are used as the solidification models in this study. In light of these solidification models. the simulation can be achieved by personal computer. In the traditional solidification simulation, the obvious deviations between experimental and calculation. results are basically caused by negleting the importance of the interfacial thermal resistance. In addition to the traditional simulation technique, interfacial thermal resistance obtained as a funtion of temperature is employed in the simulation to improved the calculation results. From the simulations in this study, the nucleation coefficient in the proportional model and the nucleation particle number in the heterogeneous model are recommened to choose as 1000 and 1016 respecticely. Moreover, it is found that the heterogeneous model is the better one.
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Javaid, Amjad. "Morphological features of spheroidal graphite in ductile cast iron." 1989. http://catalog.hathitrust.org/api/volumes/oclc/20078809.html.
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Thesis (M.S.)--University of Wisconsin--Madison, 1989.Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 108-113).
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Nikolai, Michael F. "Effects of tinned steel scrap in ductile cast iron." 1994. http://catalog.hathitrust.org/api/volumes/oclc/32845522.html.
Full textAbstract:
Thesis (M.S.)--University of Wisconsin--Madison, 1994.Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves vi-vii).
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Lee, Cheng Yen, and 李承諺. "The Influence of Rare earths(Lanthanum) in Ductile Iron." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/q332w5.
Full textAbstract:
碩士國立臺北科技大學
材料科學與工程研究所
97
In production of whole batch of cast iron castings, in order to save cost and consume rejects, a commercial foundry will use foundry returns. However, the amount of foundry returns used should be controlled at about 50%, and the remainder is fresh raw materials such as cast iron and scrap steel with the returns not exceeding 70% at most. Two reasons are responsible for this: on one hand, the composition and quality of re-melt products is worse than those of castings made from fresh raw materials, and internal alloying elements that have been added as required can not removed readily, the remained alloying elements may not be at the desired content, and further, there may be interference among alloying elements. On the other hand, the formed castings have been subjected to inoculation, while there may be magnesium residues in graphitization or nodularization. Returning and smelting to perform nodularization and inoculation is a process not different from re-activation of inoculation and nodularization once more. Furthermore, effects of nodularization and inoculation in re-melt castings might degrade slightly. This experiment employs ingot with constant composition, and uses 100% returns having same composition as the smelting raw material, while a rare earth element, lanthanum (La) is added in the liquid iron to replace the conventional magnesium nodulant in the furnace nodularization to accelerate rare earth decay rate and facilitate observation. Inoculation is carried out in a constant temperature ladle. After completing the reaction, a set of wedge form test pieces is poured every 5 minutes till liquid iron is exhausted. The decay process of the liquid surface and microscopic texture are observed and recorded. This study investigates further effects of direct pouring of additives and bell housing extruding, as well as process parameters such as varying particle sizes of nodulant and inoculant, addition amount, addition manner, addition types, time of constant temperature, pouring environment, pouring temperature and the like to achieve optimization. The experimental results indicate that, when 100% returns is used together with 2% content of rare earth element and 0.5% FeSi inoculant, the optimum cycle will be reached 10 minutes since nodularization begins. Nodular graphite cast iron with nodularization rate higher than 75% can be obtained. Matrix structure distribution is consisted of 50% pearlite, and 50% ferrite, with average graphite number per unit area higher than 300 spheroids. Decay phase occurs within 30 minutes, where nodularization effect degrades significantly to 40%, and this is an interval of compacted graphite cast iron. Complete decay occurs after 30 minutes. Reverse chill may occur at a constant probability.
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Simonite, Kenneth G. "An investigation of possible superplastic conditions in ductile cast iron." 1992. http://hdl.handle.net/1993/18686.
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Ren, Hwang Jiunn, and 黃俊仁. "A Study on the Processing Windows of Austempered Ductile Iron." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/73585223020616247585.
Full textAbstract:
碩士國立臺灣科技大學
機械工程研究所
84
Mechanical properties, including ultimate tensile strength, 0.2% offset stress, elongation, impact energy and hardness, were used to study the suitability on processing window of austempered ductile iron alloyed with 0.77%Cu and 0.5%Ni at high austempering temperature. The ranges of processing windows were derived from the electrical resistivity variations during austempering of the ductile iron. If austempered within the range of processing windows, results of higher strength and hardness but lower ductility and impact toughness will be obtained at either higher austenitizing temperature or lower austempering temperature. Optimum mechanical properties are obtained when heat treating periods are within the processing window. Both mechanical properties and microstructures show that the processing windows defined from the electrical resistivity are feasible. This thesis also discusses the improvement of segregation by homogenizing heat treatment; and the influence of the size and amount of specimen, related to the quench bath, on the hardness during austempering; also the assocaited fractography of mechanical testing.
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Chen, Chan Tung, and 陳建同. "The Study on the Transformation Kinetics of Austempered Ductile Iron." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/39813908367660353579.
Full textAbstract:
博士國立臺灣科技大學
機械工程系
87
The resistivity of alloyed ductile iron during austempering was measured to investigate the influence of austenitising temperature﹐austempering temperature and content of alloys on the kinetics of phase transformation. The specimens were heat-treated in a vacuum furnace by passing through direct current monitored and controlled with a personal computer to follow the heating and cooling scheme. Austenitising temperature from 850 to 950oC was used to bring the matrix of ductile iron into austenite phase. After a holding period at austenitising temperature, the specimens were quenched, with a liquid nitrogen spray, to desired austempering temperature to conduct the isothermal transformation. During the isothermal transformation process, the resistivity varied with time and showed three sequences of transformation: stage1﹔the processing window﹔and stage 2; clearly. The changes of resistivity around the process window were related to the volume fraction of retained austenite which was measured by X-ray diffraction technique. A model is then proposed to predict the volume fraction of retained austenite from the change of resistivity for austempering. During the progress of isothermal transformation, the resistivity of austempered ductile iron vs. time was recorded and then analyzed to determine the processing window. X-ray diffraction, heat tinting technique, and microstructural examination were conducted to examine the suitability of this processing window in terms of microstructural changes. The data of mechanical properties of the ductile iron from the same casting batch and same austempering were extracted from a concurrent work to discuss the suitability of this processing window. Both the evaluation of microstructures and mechanical properties confirmed the suitability of this processing window. A slow rate transformation during the time interval of processing window was observed, which was associated with the continuous decomposition of blocky austenite and resulted in a slight variation of the mechanical properties. A further kinetics analysis demonstrates that the reaction of all three stages mainly obey the Johnson-Mehl equation with an average value of exponent n equal to 1.20, 1.09, and 1.57, except for the final portion of stage 1 reaction for alloyed ductile iron at lower austempering temperature. The empirical activation energy of three-stage reactions calculated from the rate constant k are 19, 127, and 240 kJ/mole respectively. Increasing the austenitising temperature results in reducing the austempering reaction rate and the amount of retained austenite and in suppressing the onset of stage1 reaction. Decreasing the austempering temperature has the same influence on austempering reaction as increasing austenitising temperature. Alloyed ductile irons are shown to shift the heat treatment processing window to a longer time. The segregation of alloy elements produces the reducing of the stage 1 reaction rate but slightly accelerated the stage 2 reaction and then causes the shrinkage of the processing window.
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Cheng, S. J., and 鄭石釧. "The Effect of Low Temperature Austenitizing on Austempered Ductile Iron." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/01413017580081159436.
Full textAbstract:
碩士國立臺灣科技大學
機械工程系
92
Abstract This research is aimed to investigate the effect of low temperature austenitizing on austempered ductile irons. Use a self designed vacuum heat treating system to measure electrical resistivity during the heat treating. The austenitizing have two stages: the first stage kept in 900℃and the second stage adopt a lower temperature and then followed by an austempering. The temperature profile, microstructures and hardness from the austempered ductile irons were used to antithesis the temperature zones of phase transformation. The experimental results show that : (1) in all tests, only the ductile iron FCD 700 with austenitizing at 747℃, specimen C3, have its hardness at center portion meet the MADI standard; (2) through the temperature profiles of FCD 450、550 and 700 specimens, the critical transformation temperature range of pro-eutectoid ferrite are 784~730、750~697 and 753~689℃ respectively; (3)assisted with the micro- structures, the zone with a great quantity of pro-eutectoid ferrite would associated with a rapidly drops along the hardness profile; (4) through the micro structural observation of FE-SEM, the growth of ausferrite be hindered by the existed pro-eutectoid ferrite and resulted to a shape like short wicker. In the ferrite region of the matrix, there exists a two-layer structure. The reason is explained as that the carbon content of the pro-eutectoid ferrite are less then that of austempered ferrite.