Dissertations / Theses on the topic 'Steel alloys Heat treatment'
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1
Anderson, Danny. "Effect of the joint addition of aluminum and molybdenum on the precipitation and recrystallization in HSLA steels." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66207.
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Bradley, Christopher Michael. "Microstructural characterization and heat treatment of A-286 turbine buckets." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2009. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
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Wang, Xiaolan. "The effects of rust on the gas carburization of AISI 8620 steel." Worcester, Mass. : Worcester Polytechnic Institute, 2008. http://www.wpi.edu/Pubs/ETD/Available/etd-073108-094449/.
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Cerully, Laura B. "The fabrication of thin-walled steel alloys through the gas carburization of reduced metal oxide extrusions." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/34809.
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Investigations of the production of thin-walled steel alloys through the reduction and subsequent gas carburization of structures made from metal oxide powders were performed. Batch compositions, as well as the heat treatment parameters necessary for the formation of structures were determined through the use of thermogravimetric analysis, dilatometric measurements, and microstructural investigation. Parameters for the high temperature carburization of thin-walled 4140 structures were determined. The research has shown that the amount of carbon in the walls of the structures can be controlled and uniform carbon contents across the cross-sections can be achieved in less than 30 minutes. Heat treatments for carburized samples were performed and subsequent microhardness testing resulted in values similar to conventionally produced 4140 steel. Studies on the decarburization behavior of similar alloys under various conditions were also performed in order to aid in the prediction of the microstructural behavior of samples during carburization and subsequent heat treatment. Low temperature gas carburization of structures with 316 steel composition has also been performed. Hardness variations present through the cross-section of the part after carburization suggest some transfer of carbon, though contents are not as high as anticipated. Suggestions for future work in this area are presented. The results of these investigations yield a novel method for the production of steel parts from metal oxide powders. The speed and low cost of the process, coupled with the proven ability of the process to yield parts with similar microstructural and mechanical characteristics as conventionally made alloys, allows for the techniques presented in this study to be used for the development of alloys which could not be previously done economically.
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Dalai, Biswajit. "Microstructure and Properties of Solid-State Additively Processed Alloy 600 Claddings on 304L Stainless Steel." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1542724808933024.
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Quan, Liang. "Using FDM and FEM to simulate the decarburization in AISI 1074 during heat processing and its impact." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/44769.
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The metallurgical processes and the products developed from these processes have been the cornerstone on which our civilizations have developed and flourished. Many of the new materials that have been developed over centuries were often the result of serendipitous occurrences. Because of the importance of new materials to the improvement of society, it is necessary to accelerate the way in which new alloys and processes are designed, developed and implemented.
Over the last two decades the computational side of materials science has thrived as a result of bigger and faster computers. However, the application of new computational methods to the development of new materials and structures is still in the early stages primarily because of the complexity of most metallurgical processes. One such process is the decarburization of steel. Because of the importance of the microstructure on the mechanical properties, changes in the near surface properties are affected by the loss of carbon in the alloy. The topics investigated in this thesis include a variety of alloys and microstructures that are considered to be important in the development of a unique structure necessary for a more efficient method of recovering natural gas and oil from underground reserves as well as structures for energy absorbing systems. Since both the material application and the structure are new, this research represents an ideal opportunity to combine processing, properties, microstructure and computations to accelerate the development of these new structures.
Compared to other commercially available proppants which tend to fail in demanding environments, the thin-walled hollow metal proppants are regarded more promising due to the low density and high mechanical strength. The energy-absorbing composite material manufactured by embedding said spheres in the Mg/Al matrix material is optimized by improving sphere and matrix properties at each step in the process. Ultimately the mechanical strength, fracture toughness, and energy absorption are expected to achieve a factor of 2-5 higher than previously reported.
Modeling makes it economically practical to assess the targeted materials' overall properties, behaviors and the mechanical responses in conjunction with stress environment, material properties, material dimensions among other variables, before a structure is built. Additionally, more advanced modeling can enable the quantitative descriptions of more complex metallurgical phenomena such as the effects of impurity elements and deformation under complex loading conditions.
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Dai, Tao Dai. "Effect of Postweld Heat Treatment on the Properties of Steel Clad with Alloy 625 for Petrochemical Applications." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1523572474171801.
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Maropoulos, S. "The effect of heat treatment on structure-property relationships in a low alloy Ni-Cr-Mo-V steel." Thesis, University of Manchester, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370954.
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Doležal, Petr. "Vlastnosti nízkolegovaných ocelí za snížených teplot." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2014. http://www.nusl.cz/ntk/nusl-231635.
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The goal of the thesis was research in the field of structure and properties of low alloyed steels used in low temperature environment. Work was focused on heat treatment and chemical composition of the steel and their impact to hardness and impact energy values. Chemical composition and heat treatment of steel was proposed on the basis of achieved results.
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From, Malin, Johanna Ejerhed, Artin Fattah, Markus Lindén, and Alex Karlstens. "Heat Resistant Steel Alloys : Atlas Copco." Thesis, Uppsala universitet, Institutionen för teknikvetenskaper, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-256662.
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Atlas Copco is interested in investigating the friction in the top-hammer drilling tool threads thatcauses the steel to heat up, leading to a phase transformation and a softer steel in the threads. Theaim of this project is to find a steel alloy or surface finishing that will retain its hardness atelevated temperatures better than the presently used threads material. The solution is intended tobe used as a replacement material for the threads. The potential material is meant to combat thepremature breakdowns of the threads and thus minimizing the economical losses. To achieve ourproject goal, literature studies and an experimental parts were employed.Hardening methods are discussed thoroughly in the thesis, such as carbides/nitrides,precipitation, solid solution, grain size, and martensitic transformation. Alloying elements andtheir effects on steels properties were also discussed. C, Cr, Co, Mn, Mo, Ni, W, and V werefound to increase the steel's hardness at elevated temperature, high temperature strength andabrasion wear resistance.Nitration can be applied to most of the steels that Atlas Copco uses today, and will give a harder,and more wear resistant surface at elevated temperatures. A problem with nitration is that thenitrided layer is generally thinner than the martensitic hardening used today.Three tool steels samples (ASP 2030, ASP 2053 and ASP 2060) were acquired from Erasteel.These were used in the experimental part and compared to reference steels that Atlas Copcocurrently are using (R1-R6). The experiments were conducted in 400 and 600°C and the sampleswere tempered for 1, 10 and 100 hours before the hardness were measured with a Vickershardness test. The conclusion from the experiments was that ASP 2060 and ASP 2053 fromErasteel are the steels that have a much higher hardness at elevated temperature than the othersteels tested in the experiment. The results indicate that the tool steels will probably notexperience the same premature breakdown as the threads used today. R1 and ASP 2053 have thegreatest heat resistance.The suggested tool steels are all quite expensive, and to minimize the material needed only thethreads and not the rod can be in the new alloy. Lowering the cost could also be achieved byhardfacing where a layer of the new expensive alloy is welded onto a cheaper steel.
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Cochet, Julien. "Conception optimisée et comportement en service de manilles forgées." Thesis, Lorient, 2016. http://www.theses.fr/2016LORIS241.
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Les manilles utilisées pour l'assemblage et l'amarrage des plates-formes pétrolières nécessitent des propriétés mécaniques de plus en plus élevées. Mais les défauts de fabrication de ces manilles, responsables de leur rupture prématurée, engendrent des coûts d'intervention très élevés. Afin de comprendre et d'anticiper ces défauts de fabrication, trois outils numériques ont été développés permettant de simuler (i) le procédé de fabrication, (ii) le traitement thermique et (iii) le chargement mécanique de la manille. Le procédé de fabrication des manilles est constitué d'une succession de différentes étapes de forgeage à chaud et a été caractérisé avec des mesures de température, géométrie et efforts durant toutes les étapes. Un modèle numérique thermo- mécanique du procédé de fabrication a été développé en 3D et permet de prédire tous les paramètres de forge. Une étude numérique d'influence de certains paramètres du procédé a permis de comprendre les différentes causes de mise au rebut. Des mesures de température, des observations métallographiques au microscope et au MEB ainsi que des essais mécaniques ont été effectués sur des lopins après différents cycles de traitement thermique. Un modèle numérique de traitement thermique a été développé en 1D et permet de simuler les changements de phases pendant la normalisation et la trempe, et ainsi d'obtenir la dureté résultante en tout point du lopin. Finalement, une cartographie des propriétés mécaniques d'une manille a été obtenue et les modes de déformation de la manille en condition de chargement ont été évalués par le biais d'un essai de tension sur banc. Le modèle numérique de la manille sous tension a été développé en 3D et permet d'évaluer la charge maximale en service, la charge à rupture ainsi que la zone critique de la manille étudiéeShackles used for the assembly or the mooring of petroleum platforms require constantly higher mechanical properties. But the manufacturing defects often lead to premature failure which can cost 1M€/day. Thus, in order to understand and anticipate those manufacturing defects, three numerical tools have been developed to simulate (i) the manufacturing process, (ii) the heat treatment and (iii) the mechanical behavior of the shackle. A shackle is manufactured via a sequence of hot forming stages and the manufacturing process has been characterized during all the stages, with measures of temperature, geometry and loads. The numerical thermo-mechanical model has been developed in 3D and gives a very good prediction of each forging parameters. A numerical study of influence of some process parameters has led to a better understanding of scrapping. Temperature measurements, metallographic observations as well as mechanical testing have been carried out on cylindrical rods after various heat treatment cycles. The numerical heat treatment model has been developed in 1D and predicts phase transformations during normalizing and quenching, as well as the hardness at each point of the rod. Finally, the distribution of the mechanical properties over a shackle has been characterized and the deformation modes of the shackle were evaluated via a load test on a dedicated bench. The numerical model of the shackle under tension has been developed in 3D and allows to evaluate the working load limit, the break load as well as the critical zone of the shackle
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Forte, Julio Faria da Silva. "Modelagem e otimização de experimentos para o tratamento térmico de recozimento: um estudo com o algoritmo simulated annealing." Universidade do Estado do Rio de Janeiro, 2012. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=4380.
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Esta dissertação apresenta um estudo da modelagem de experimentos aplicados a um processo industrial de tratamento térmico. A motivação deste trabalho surgiu diante das dificuldades associadas aos processos de recozimento industrial de aços do tipo baixa liga, na tentativa de encontrar temperaturas nas quais as durezas superficiais dos aços atingissem valores suficientemente baixos, adequados para etapas posteriores de fabricação, em especial a usinagem. Inicialmente forem realizados diversos experimentos com diferentes aços, onde a dureza superficial é obtida em função da temperatura de recozimento e dos teores de carbono e silício das amostras utilizadas. Em seguida propôs-se um modelo quadrático para modelar a dureza superficial como função dessas três variáveis. A estimação de parâmetros do modelo proposto foi realizada com o emprego do algoritmo Simulated Annealing, uma meta-heurística para otimização global que procura imitar o processo de recozimento de um material sólido. Finalmente, usando-se o modelo proposto, foi resolvido o chamado problema inverso, o qual consiste na estimação da temperatura de recozimento em função dos teores de carbono e silício
e da dureza desejada.This dissertation presents a study for experiments modeling applied for a heat treatment industrial process. The driving force to this work have raised from usual difficulties while low-alloy steels annealing industrial processes get on, trying to find out temperatures which the superficial hardness measurements reaches low values enough and suitable for the following stages, in special focus, the machining. At the first time, some experiments have been done with several steel grades, where superficial hardness is achieved as a function by annealing temperature, percent carbon content and percent silicon content of the samples. There was purposed a quadratic model for modeling the hardness as a function of that three parameters. The parameter estimation of the purposed model was done by the simulated annealing algorithm, a metaheuristic for global optimization which can be as the same as annealing of a solid material. Starting at the purposed model, the inverse problem was solved, where the estimated annealing temperature was achieved by the carbon and silicon percent contents and the suitable hardness.
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Tavitas-Medrano, Francisco Javier. "Artificial aging treatments of 319-type aluminium alloys." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=103299.
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Aluminum-silicon-copper cast alloys of the 319-type have attained a commercially important status because of their widespread use. Artificial aging treatments are routinely applied to these alloys in order to obtain precipitation hardening and improve their mechanical properties. Standard treatments may not always yield the optimum achievable properties, thus Mg and Sr are commonly added to improve the response of the alloy to aging and to modify the eutectic Si morphology from acicular to fibrous, respectively. The present study was carried out to investigate aging behavior of four 319-type alloys in regard to such mechanical properties as their ultimate tensile strength, yield strength, microhardness, percent elongation and impact toughness. Non-conventional aging cycles were applied so as to evaluate the degree of the improvement in strength obtainable. These treatments, labeled in this study as T6- and T7-type multi-temperature and interrupted aging treatments, involve several heating stages at different temperatures, as opposed to the single stage at constant temperature specifications of the standard T6 or T7 heat treatment regimes. Scanning electron microscopy was used to examine the fracture surfaces of selected tensile-tested samples to compare the fracture behavior. Transmission electron microscopy was used to reveal and identify the tiny precipitates which appear in the microstructure as a result of the precipitation-hardening process due to artificial aging. It was found that the main strengthening phase is theta-Al2Cu in the form of needles; other phases were observed as minor constituents in this alloy, including the binary beta-Mg2Si, the ternary S-CuAlMg 2 and the quaternary Q-Al5Cu2Mg7Si 7. The results show that while Mg and Sr additions improve the properties of the alloy, the standard T6 treatment may not be the best available option to produce optimum properties. In fact, when the peak-aged (T6) condition is desired, the optimum treatment consists of a continuous artificial treatment at 170°C for 8 h; when the overaged (T7) condition is desired, a T7-type multi-temperature treatment consisting of underaging at 170°C for 1 h, then at 190°C for 1 h, and finally overaging at 240°C for 2 h is the best option.
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Walker, Jacob D. "Heat Transfer Analysis of Localized Heat-Treatment for Grade 91 Steel." DigitalCommons@USU, 2017. https://digitalcommons.usu.edu/etd/6045.
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Many of the projects utilizing Grade 91 steel are large in scale, therefore it is necessary to assemble on site. The assembly of the major pieces often requires welding in the assembly; welding drastically changes the superior mechanical properties of Grade 91 steel that it was specifically developed for. Therefore, because of the adverse effects of welding on the mechanical properties of Grade 91, it is necessary to do a localized post weld heat treatment.
In this study a localized post weld heat treatment is used to gather experimental data. The data is then used to derive unknown heat transfer coefficients that are necessary for theoretically modeling heat treatments. With the derived coefficients that have been found one can theoretically model heat treatment scenarios specific to the situations and provide results that are reliable and provide insight as to what parameters will provide the best results.
This research is very beneficial to the joining of metals industry because it provides a way to ensure the method used to heat treat the welded section is being properly done, and the required heat treatment is achieved. It is applicable to many different geometries so that it can be modified to specific situations.
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Bhatti, A. R. "Effect of heat treatment on metallic glasses." Thesis, University of Oxford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.236306.
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Sjölander, Emma. "Heat treatment of Al-Si-Cu-Mg casting alloys." Doctoral thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH. Forskningsmiljö Material och tillverkning – Gjutning, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-15695.
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Environmental savings can be made by increasing the use of aluminium alloys in the automotive industry as the vehicles can be made lighter. Increasing the knowledge about the heat treatment process is one task in the direction towards this goal. The aim of this work is to investigate and model the heat treatment process for Al-Si casting alloys. Three alloys containing Mg and/or Cu were cast using the gradient solidification technique to achieve three different coarsenesses of the microstructure and a low amount of defects. Solution treatment was studied by measuring the concentration of Mg, Cu and Si in the α-Al matrix using wavelength dispersive spectroscopy (WDS) after various times at a solution treatment temperature. A diffusion based model was developed which estimates the time needed to obtain a high and homogenous concentration of alloying elements for different alloys, temperatures and coarsenesses of the microstructure. It was shown that the yield strength after artificial ageing is weakly dependent on the coarseness of the microstructure when the solution treatment time is adjusted to achieve complete dissolution and homogenisation. The shape and position of ageing curves (yield strength versus ageing time) was investigated empirically in this work and by studying the literature in order to differentiate the mechanisms involved. A diffusion based model for prediction of the yield strength after different ageing times was developed for Al-Si-Mg alloys. The model was validated using data available in the literature. For Al-Si-Cu-Mg alloys further studies regarding the mechanisms involved need to be performed. Changes in the microstructure during a heat treatment process influence the plastic deformation behaviour. The Hollomon equation describes the plastic deformation of alloys containing shearable precipitates well, while the Ludwigson equation is needed when a supersaturated solid solution is present. When non-coherent precipitates are present, none of the equations describe the plastic deformation well. The evolution of the storage rate and recovery rate of dislocations was studied and coupled to the evolution of the microstructure using the Kocks-Mecking strain hardening theory.
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Hilty, Eric. "Influence of Welding and Heat Treatment on Aluminum Alloys." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1396877051.
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King, Benjamin. "Welding and post weld heat treatment of 2.25%Cr-1%Mo steel." Access electronically, 2005. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20060404.095844/index.html.
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Martin, D. C. (David Charles). "Selected heat conduction problems in thermomechanical treatment of steel." Doctoral thesis, Oulun yliopisto, 2011. http://urn.fi/urn:isbn:9789514295195.
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Abstract This thesis considers two related problems where heat conduction is accompanied by phase transformation during the cooling of carbon steels – phenomena which are fundamental to modern thermomechanical treatment processes. In the first problem, a non-linear heat equation formulation is described which includes linkage between irreversible diffusive and diffusionless phase transformation processes and thermophysical properties. A family of numerical schemes using finite difference methods with diagonally implicit Runge-Kutta method integrators for solving this formulation is present. Sample calculations using these schemes are presented for a mild steel cooled under range of industrially relevant heat transfer conditions. These calculations illustrate the need for careful scheme design and solver selection when coupled heat conduction and microstructure evolution equations become non-linear and stiff. The second section of the thesis extends this heat conduction formulation into the realm of inverse analysis. The problem of temperature reconstruction and boundary condition estimation using temperature measurements obtained thermocouples embedded into laboratory samples undergoing phase transformation is considered. A solution method based on iterative regularization is described for solving the resulting ill-posed problem. An analysis of extremely high rate cooling experiments made on a pilot-plant descaling unit using the inverse method is presented. This analysis highlights some of the practical issues associated with embedded thermocouple temperature measurements made in this fashionTiivistelmä Väitöstyössä tutkitaan kahta ongelmaa liittyen hiiliteräksen termomekaanisen käsittelyn numeeriseen mallintamiseen. Työssä tarkastellaan teräksessä tapahtuvaa lämmönsiirtoa ja faasimuutoksia jäähdytyksen aikana, eli ensisijaisen tärkeitä ilmiöitä kehittynyttä teräksen valmistusta ja prosessointia ajatellen. Ensimmäisenä ongelmana tutkitaan epälineaarisen energiayhtälön muodostaminen huomioiden teräksen termofysikaaliset materiaaliominaisuudet, diffuusion kontrolloimat ja diffuusiosta riippumattomat irreversiibelit faasimuutokset. Lisäksi huomioidaan näiden väliset kytkennät. Yhtälöt ratkaistaan numeerisesti ja käytetyt menetelmät esitellään differenssimenetelmien ja diagonaalisesti implisiittisten Runge-Kutta-menetelmien osalta. Väitöstyössä näiden käyttöä havainnollistetaan simuloimalla niukkahiilisen teräksen käyttäytymistä teollisia olosuhteita vastaavan jäähdytyksen aikana. Laskentatulokset osoittavat ratkaisumenetelmän suunnittelun ja valinnan tärkeyden erityisesti silloin, kun lämmönjohtuminen, mikrorakenteen kehittyminen ja termofysikaaliset materiaaliominaisuudet muuttavat ratkaistavan ongelman epälineaariseksi ja jäykäksi. Toisena ongelmana tutkitaan edellä esitetyn lämmönsiirtomallin käyttöä osanainversioanalyysiä. Laboratoriokokeiden, termopareilla suoritettujen lämpötilamittausten, työssä kehitetyn lämmönsiirtomallin ja suoritetun inversioanalyysin avulla rekonstruoidaan teräskappaleiden lämpötila- ja faasimuutoskäyttäytymistä sekä estimoidaan mallin reunaehtoja. Näin luotu inversio-ongelma on kuitenkin matemaattisesti tarkasteltuna ns. huonosti asetettu ongelma, ja sen ratkaisemiseksi käytetään iteratiiviseen säännöllistämiseen perustuvaa menetelmää. Väitöstyön inversioanalyysiä havainnollistetaan pilot-mittakaavan kokeiden avulla, joissa hilsepesuria käyttäen koekappaleen jäähtymisnopeus saadaan erittäin korkeaksi. Tulokset nostavat esille inversio-analyysiin liittyviä ongelmia ja rajoitteita nopeaan jäähtymiseen sekä lämpötilamittauksiin liittyen
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Al, Malki Uthman Mosfer. "The novel quenching and partitioning heat treatment of steel." Thesis, University of Leeds, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.595670.
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The recently proposed and novel steel heat treatment process known as quenching and partitioning (Q&P) is studied, in particular, the partitioning stage. Characterization of the partially quenched microstructure prior to the partitioning stage is enabled by using a base composition containing a higher Mn concentration than for conventional Q&P steels, such that quenching to room temperature produces only partial decomposition of austenite to martensite. Increasing the carbon concentration of this base composition also enabled a study of the effect of steel carbon content, although at the higher carbon contents refrigeration was required to achieve marten site because of the reduced Ms temperatures. Increased carbon also allowed the effect of martensite morphology to be examined. Intercritical annealing of a conventional TRIP steel composition provided an alternative route towards increasing the carbon concentration of austenite prior to partitioning. Light optical microscopy, scanning electron microscopy, X-ray and neutron diffraction were used to characterise the evolution of microstructure. In particular, in-situ examination of the Q&P heat-treatment process, enabled by introducing a furnace into the neutron beam-line, gave real -time observations and analyses of partitioning. Lattice parameter measurements enabled calculation of the carbon content of retained austenite, providing evidence of carbon partitioning from martensite to untransformed austenite during the partitioning stage. Thus, the partitioning process was shown to be effective in thermal and mechanical stabilization of retained austenite. In addition, evidence was found for substantial carbon enrichment of the austenite phase, which might be expected to provide opportunity for new Q&P steel grades with enhanced properties
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Bigg, Timothy David. "Quenching and partitioning : a new steel heat treatment concept." Thesis, University of Leeds, 2011. http://etheses.whiterose.ac.uk/3145/.
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Steel continues to be one of the primary materials in use today, however, even after 200 years of published research, innovative methods are being discovered and exploited to produce steel with enhanced properties. One such recent discovery has been termed Quenching and Partitioning (Q&P). The Q&P heat treatment process is reported to produce a multiphase microstructure consisting of retained austenite stabilised to room temperature, and a harder martensitic phase. This combination is prospected to form a new generation of high strength, formable sheet steel well suited to the demands of the automotive industry. Previous research has reported on the application of Q&P to commercial grades of steel, however, the temperatures required have hampered study of the process. In this investigation a model alloy has enabled separation of Q&P into its individual stages for closer inspection. Standard metallographic techniques were used to examine the microstructure of the material, followed by X-ray diffraction measurements to determine the stability of the austenite phase fraction before and after partitioning, confirming the effectiveness of the partitioning process in stabilising retained austenite. Estimations of carbon concentration via lattice parameter measurements have provided evidence of austenite carbon enrichment, but also suggest that some carbon remains unaccounted for, possibly as an equilibrium distribution between epsilon carbides and strained interstitial sites. In-situ partititioning in a neutron diffractometer has been utilised to obtain real-time measurements of the partitioning process. These measurements suggest that redistribution of carbon within martensite occurs before partitioning to austenite becomes kinetically significant. The trapping of carbon within energetically favourable locations is postulated to be a major factor in retarding carbon migration from martensite to austenite when compared to mathematical models of the partitioning process. Neutron diffraction measurements of carbon interstitial occupancy in austenite have also provided further evidence of austenite carbon enrichment during the partitioning process.
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Sulaiman, Samsiah. "Structure of properties of the heat affected zone of P91 creep resistant steel." Access electronically, 2007. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20080916.150054/index.html.
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Paray, Florence. "Heat treatment and mechanical properties of aluminum-silicon modified alloys." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=41146.
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The commercial applications of cast Al-Si alloys depend to an important extent on controlling the morphology of the eutectic silicon through thermal modification in the solid state and/or chemical modification of the melt before the production of the casting. The effects of modification and/or heat treatment on the microstructure and the mechanical properties of 356 alloy have been investigated on both permanent mold and sand cast samples. Strontium (0.02%) and sodium (0.01%) were used to produce well modified microstructures. The importance of the amount of modifier used was also examined in producing castings with 0.002% Sr and 0.08% Sr. Production parameters such as solution heat treatment time and artificial aging time were examined.Microstructural assessment was done by quantitative metallography using image analysis coupled to SEM while mechanical testing comprised tensile testing, hardness and microhardness measurements as well as impact tests.
The greatest improvement in mechanical properties obtained with modification was observed for the lower rates of solidification, i.e sand casting. The effect of modification on the heat treatment response of 356 alloy was investigated. The differences between unmodified and modified microstructures were more important in sand cast samples than in permanent mold cast samples. After one hour of solution heat treatment at 540$ sp circ$C, both permanent mold unmodified and modified microstructures became similar in terms of silicon particle size and sphericity. The processes which led to this were different. Silicon platelets in the unmodified structures segmented while silicon particles in the modified alloy coarsened. The final result was however the same. In sand cast alloy, the initial microstructural differences persisted after up to 12 hours of solution treatment. The coarser the initial as-cast microstructure, the greater the improvements associated with modification and heat treatment.
It was also found that porosity caused by modification can negate many of the microstructural benefits by decreasing tensile strength and percent elongation. It was demonstrated that modification also has an influence on the aluminum matrix. The hardness of modified alloy was found to be less after the T6 temper than in unmodified alloy. This was reflected in a lower yield strength of modified 356 alloy.
Quantitative microstructure-mechanical property relationships were established for the permanent mold samples. The best silicon-structure characteristics to predict the tensile properties were found to be the particle count per unit area and the particle area.
It was also determined that hardness can be a simple and inexpensive means whereby ultimate tensile strength and yield strength of 356 alloy in the T4 condition or T6 condition can be estimated.
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Wu, Chang Kai. "Predicting the Response of Aluminum Casting Alloys to Heat Treatment." Digital WPI, 2012. https://digitalcommons.wpi.edu/etd-dissertations/117.
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The objective of this research was to develop and verify a mathematical model and the necessary material database that allow predicting the physical and material property changes that occur in aluminum casting alloys in response to precipitation-hardening heat treatment. The model accounts for all three steps of the typical precipitation hardening heat treatment; i.e., the solutionizing, quenching, and aging steps; and it allows predicting the local hardness and tensile strength, and the local residual stresses, distortion and dimensional changes that develop in the cast component during each step of the heat treatment process. The model uses commercially available finite element software and an extensive database that was developed specifically for the aluminum alloy under consideration - namely A356.2 casting alloy. The database includes the mechanical, physical, and thermal properties of the alloy all as functions of temperature. The model predictions were compared to measurements made on commercial cast components that were heat treated according to standard heat treatment protocols and the model predictions were found to be in good agreement with the measurements.
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Jeong, Tae Ki 1968. "Subcritical heat treatment of cold rolled multi-phase trip steel." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=82605.
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The high strength of TRIP (TRansformation Induced Plasticity) steel enables high fuel efficiency by reducing the weight of a car without any loss of safety. In addition, the good formability shown by TRIP steel extends the application of this type of steel to complicated component shapes. TRIP steels can be used in the cold rolled and 'TRIP annealed' condition. After cold rolling, TRIP steels are subjected to a complicated anneal/heat-treatment encompassing intercritical annealing followed by bainitic transformation. Because the 'TRIP annealing' is designed to produce the complex microstructures, comprised of ferrite, bainite, retained austenite, which achieve the best combination of strength and formability; the processing of these steels requires careful selection and delicate control of temperatures and holding times. In this context, this research work has been carried out to design an alternative process for TRIP steel, using a relatively simple subcritical heat-treating process. Basically, the concept is to cold roll the TRIP steel to produce strain induced martensite, as well as work hardened ferrite and bainite, and then to 'conventionally' anneal the steel to produce tempered martensite and bainite, as well as recrystallized ferrite. For this purpose, 'subcritical heat treatment' of multiphase cold rolled TRIP steel at 200, 300, 400, 500, 550, 600, 650ºC for a hour were done then the microstructure, mechanical properties were investigated with x-ray diffraction, OM and SEM, tensile testing and hardness measuring. The mechanical properties after the subcritical heat treatment at 600ºC and over are approaching those of traditional TRIP processed steel hence this process can be a promising alternative and worth further study.
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Tenner, Jonathan. "Optimisation of the heat treatment of steel using neural networks." Thesis, University of Sheffield, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.719165.
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Carsbring, Amanda. "Heat Treatment and Secondary Phase Formation in FeCrNi Medium Entropy Alloys." Thesis, KTH, Materialvetenskap, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-291251.
Full textAbstract:
The topics of high entropy alloys (HEA) and medium entropy alloys (MEA) have been heavily researched in recent years. A HEA usually consists of five or more base elements, and a MEA would have three or four base elements. These types of alloys are multi-principal element alloys (MPEA) that have been thought to have interesting properties due to their high configurational entropy, which was thought to be the reason for stabilized simple solid solution phase in the HEA. The high entropy effect contributing to stable single phase in these alloys has been discussed and has not been found to be a predicament to which MPEA that will present as single phase at lowered temperatures. Still, some of the HEA and MEA investigated have interesting properties such as high ductility and good thermal properties, as is the case for the commonly researched CoCrFeMnNi HEA and the CoCrNi MEA which are both solid solution FCC phase at lower temperatures. This master thesis aims to investigate one of the less commonly researched MEA: equimolar FeCrNi. This alloy has been studied previously, and it was found there might be a possibility of precipitation hardening the alloy. To further study this alloy system, three FeCrNi alloys in the close-to equimolar range were produced and underwent a series of aging heat treatments to study the amount of precipitated secondary phase with composition changes and different aging temperatures. The objective is to evaluate and interpret the data found in the different CALPHAD databases used in Thermo-Calc and FactSage software and make comparisons to the experimental results. This to discuss the possibilities of hardening this alloy through aging treatment. The alloys selected and produced are 33Fe33Cr33Ni, 40Fe30Cr30Ni and 45Fe30Cr25Ni, all in mol%. Through experimental investigation using x-ray diffraction (XRD) analysis, it is found that Cr-rich BCC phase is formed in all alloys after most of the aging treatments performed. The volume fraction of BCC was quantified through the reference intensity ratio (RIR) method. From quantification, the largest volume fraction BCC is found in the equimolar 33Fe33Cr33Ni alloy, and the lowest fraction BCC is shown in the 40Fe30Cr30Ni alloy. The increased volume fraction of BCC coincides with an elevated hardness in all three alloys. It is also found that out of the three equilibrium phase calculations used in this project, the ThermoCalc steel database TCHEA4 seems to give results that are in closest agreement with the experimental results. For future studies in this subject, the recommendation is to further study the mechanical properties of the FeCrNi MEA and assess possibilities for application.Högentropilegeringar och mediumentropilegeringar har studerats närmre de senaste åren på grund av deras intressanta mekaniska egenskaper. En högentropilegering består vanligtvis av fem eller flera baselement, och en mediumentropilegering har tre eller fyra baselement. Detta skiljer dem från konventionella legeringar som i regel har ett, maximalt två, baselement. Dessa typer av multi-baslegeringar har ansetts ha intressanta egenskaper på grund av deras höga konfigurationsentropi, vilken tros vara orsaken till stabilisering av fast lösningsfas i legeringarna. Högentropieffekten som bidrar till stabil enfas i dessa legeringar har diskuterats och har emellertid inte visat sig vara tillförlitligt för att förutsäga vilka multi-baslegeringar som blir fast lösningsfas vid ett lägre temperaturintervall. Ändå har några av de undersökta legeringarna intressanta egenskaper som hög duktilitet och goda termiska egenskaper, vilket är fallet för högentropilegeringen CoCrFeMnNi och mediumentropilegeringen CoCrNi som båda är enkel FCC-fas vid lägre temperaturer. Detta examensarbete syftar till att undersöka en av de mindre omnämnda mediumentropilegeringarna: ekvimolär FeCrNi. Denna legering har studerats tidigare, och det visade sig att det kan finnas en möjlighet att utskiljningshärda legeringen. För att ytterligare studera detta legeringssystem producerades tre FeCrNi-legeringar i ett sammansättningsintervall nära ekvimolär sammansättning, som sedan genomgick en serie åldringsbehandlingar för att studera mängden utskild sekundär fas beroende på sammansättning och åldringstemperatur. Målet är att utvärdera och tolka data som finns i de olika CALPHAD-databaserna som används i beräkningsverktygen Thermo-Calc och FactSage, och därefter göra jämförelser med experimentresultaten. Detta för att diskutera möjligheterna att härda dessa legeringar med partikelutskiljning. De legeringar som valts och tillverkats är 33Fe33Cr33Ni, 40Fe30Cr30Ni och 45Fe30Cr25Ni, alla angivna i molprocent. Genom experimentella undersökningar med röntgendiffraktionsanalys hittades att BCC-fas med höga halter Cr bildats i alla legeringar efter majoriteten av åldringsbehandlingarna som utförts. Volymfraktionen av BCC kvantifierades genom beräkningar från referensintensitetsförhållande (RIR). Från kvantifiering fås den största volymfraktionen BCC i den ekvimolära 33Fe33Cr33Ni-legeringen, och den lägsta fraktionen BCC i 40Fe30Cr30Ni-legeringen. Högre volymfraktion BCC sammanfaller med en förhöjd hårdhet i alla tre legeringarna. Det visar sig också att utav de tre jämviktsfasberäkningarna som används i detta projekt så är det ThermoCalc-ståldatabasen TCFE10 som gett resultat som överensstämmer med experimentresultaten. För framtida undersökningar inom detta område rekommenderas att studera de mekaniska egenskaperna hos FeCrNi och bedöma möjligheterna för tillämpning av materialet.
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Kish, Joseph J. "Active-passive corrosion of Fe-Cr-Ni alloys in hot concentrated sulphuric acid solutions /." *McMaster only, 1999.
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Ohlsson, Jonas. "Effects of different heat treatments on hardness of Grade 91 steel." Thesis, Karlstads universitet, Avdelningen för maskin- och materialteknik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-32805.
Full textAbstract:
CCI Valve Technology AB is a company located in Säffle, Sweden, that manufactures and installs bypass valves. Due to requirements outside normal standards on the valve's hardness values, some measurements have had difficulties meeting such requirements. During this thesis work, tests were carried out to determine how to overcome the difficulties. The experiments focused on five different areas that may affect the components hardness, welding method, soaking temperature during post weld heat treatment, measuring procedure, component thickness and number of heat treatment cycles. The Grade 91 steel specimens that were examined consisted of five solid cylinders and three various pipes that were welded together by using shielded metal arc welding (SMAW) or gas tungsten arc welding (GTAW). Each pipe was sawed apart into three equal parts. All specimens were hardness tested and eight of the specimens' microstructure was studied with an optical microscope. The hardness measurement instruments used, LECO V-100-C2 and GE-MIC 10, are Vickers hardness testers, one stationary and the other one portable. The measuring results contain a vast number of different hardness measurement data. From the analyzed data, the conclusions were drawn that the most suitable soaking temperature during post weld heat treatment were 750° C, that the SMAW method creates a more stable hardness profile than the GTAW method, and that one heat treatment cycle is more beneficial than two or more.
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Iyer, Kaushik A. "Quantitative characterization of thermophysical properties in computational heat transfer." Full text open access at:, 1993. http://content.ohsu.edu/u?/etd,273.
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Hodgson, David K. "The Post Weld Heat Treatment Response in the Heat Affected Zone of 2.25Cr-1Mo Steel." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1367416587.
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Warke, Virendra S. "Predicting the response of powder metallurgy steel components to heat treatment." Worcester, Mass. : Worcester Polytechnic Institute, 2008. http://www.wpi.edu/Pubs/ETD/Available/etd-072808-100705/.
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Shi, Shu. "Repair weldability of heat-resistant stainless steel casings-HP45NB, HP50NB and 20-32NB alloys." The Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=osu1140490923.
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Cupido, Llewellyn Heinrich. "Experimental and numerical investigation of heat treatment of al-si-cu alloy." Thesis, Cape Peninsula University of Technology, 2014. http://hdl.handle.net/20.500.11838/1291.
Full textAbstract:
Dissertation submitted in fulfilment of the requirements for the degree
Master of Technology: Mechanical Engineering
in the Faculty of Engineering
at the Cape Peninsula University of TechnologyAluminium alloys has seen recent increase usage in the automotive industry. This is due to the global obligation towards carbon emission reduction and fuel efficiency in the transport sector. The good strength-to-weight ratio offered by Al-Si-Cu alloys showed promising results towards the compliance of these environmentally friendly criteria. The enhanced mechanical properties is obtained when the alloy is subjected to the T6 heat treatment process, which cause microstructural changes due to the evolution of intermetallic phases. The process involves solution heat treatment, for dissolving soluble Cu- and Mg-containing phases, the homogenization of alloying elements, and the spheroidisation of eutectic Silicon. It is followed by quenching, for maximum precipitation hardening particle retention in solution, and a further artificial ageing process with the aim to acquire a uniform distribution of small precipitates, for strength improvement. The heat treatment schedule applied in this study was conducted as follows: Solution heat treatment at a temperature of 525°C for 6h Quenching in water of temperature 50°C; Artificial ageing for 8h at a temperature of 175°C, and then after left inside furnace to cool down to room temperature. This is higher than the 520°C, but shorter than the 8-12h, observed in literature. Also, quenching is done at a lower temperature rather than 60°C, and artificial ageing at a higher temperature, rather than the 155°C. This was done to be able to draw a comparison between the MAGMASOFT® simulation, which has this non-adjustable schedule, and the experimental results. The simulated and experimental results were comparable and similar outcomes, but with some discrepancies. Such as the porosity was far more visible and intense in the experimental, than what was predicted by the software. The as-cast and heat treated microstructure revealed the expected evolution of intermetallic particles, such as dissolving of the Al2Cu and the spheroidisation of the eutectic Si phases. Another phase that was identified was the insoluble AlFeSi and other possible Fe-containing phases, which due to the higher solution heat treatment temperature, showed partial fragmentation and dissolution. The study provided practical data about the effect of heat treatment on microstructural evolution and how it affects the properties of the Al-Si-Cu alloy. It also brought to the attention and understanding of how critical pouring temperature is, as it affect the initial nucleation, and cooling rate, and therefore the micro and macro properties.
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Li, Cheng. "Effect of heat treatment on the microstructure of a 2CrMoNiWV rotor steel." Thesis, Sheffield Hallam University, 1996. http://shura.shu.ac.uk/3133/.
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A wide range of experiments have been carried out on a 2CrMoNiWV low alloy steel to investigate the effect of various heat treatment conditions on microstructural change, alloy carbide transformation mechanism and mechanical properties. Two complete continuous cooling transformation (CCT) diagrams were constructed for this steel on the basis of experimental dilatometry thermal analysis, metallographic examination and current phase transformation theory. The significance of these two diagrams is in that they can be directly utilised in industrial practice as a reference during heat treatment for this material. Meanwhile it was confirmed that this 2CrMoNiWV steel can be transformed to a fully bainitic microstructure over a wide range of cooling rates and this feature proved this steel suitable for large diameter steam turbine rotor application. An innovative carbide extraction technique for the XRD identification of carbide phase has been developed. The detailed description of this new technique and its advantages are discussed in this thesis. The extensive work using TEM/EDX has set up essential "finger prints" for the quick examination of large amounts of individual carbide existing at various heat treated conditions. Simultaneous measurements and determinations were made on particle composition, morphological change, the type, amount and distribution of these carbide phases. Thus the sequence of carbide transformation for this 2CrMoNiWV steel during tempering has been established. The characteristic microstructures of various heat treated specimens were carefully examined and discussed. Theoretical thermodynamic equilibria predictions were calculated using MTDATA. A very good agreement was found between experimental results and theoretical predictions on those critical transformation temperatures and a good correlation of carbide evolution sequences was obtained. Based on experimental results and theoretical predictions, the role of tungsten in promoting creep resistance to the material is elucidated. The usefulness of equilibrium thermodynamic calculations using MTDATA in predicting the microstructural changes and carbide evolution has been demonstrated in this work, particularly the separate effect of composition on the stable carbide dispersion where a thermodynamic approach offers great benefits. A possibly optimised heat treatment route is suggested for the large diameter rotor forgings which involves austenitising at 980°C for 10 hours following by oil quenching and then tempering at 675°C for 20 hours following by air cooling. Some general conclusions are drawn from this study, especially with regard to the effect of heat treatment on the microstructure of this 2CrMoNiWV steel and suggestions for further work are made.
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Yan, Pei. "High frequency induction welding & post-welding heat treatment of steel pipes." Thesis, University of Cambridge, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609702.
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Xie, Yun. "Development of Al-Mg-Si aluminium alloys for automobile applications." Thesis, University of Nottingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366371.
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Vu, Si Man. "Effect of heat treatment, oxidation and passivation on corrosion behavior of titanium alloy in simulated body fluid." Thesis, University of Macau, 2010. http://umaclib3.umac.mo/record=b2493961.
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Hinton, Kimberly D. "Extended heat treatment effects on the fracture toughness of cast aluminum alloy A357." Thesis, Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/17361.
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Sterjovski, Zoran. "Investigation of postweld heat treatment of quenched and tempered pressure vessel steels." Access electronically, 2003. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20031127.160623/index.html.
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Shepardson, Kevin W. "Diffusion and Phase Change During Heat Treatment of Ni-B Coatings on Steel." Digital WPI, 2008. https://digitalcommons.wpi.edu/etd-theses/416.
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Nickel-boron coatings are used to improve friction and wear properties (and, in some cases, corrosion resistance). The nickel-boron coating investigated here is 5-6 wt% boron, and is deposited by electroless plating on a 1018 steel substrate. It is amorphous as-plated, and heat treatment is used to crystallize the coating to improve its hardness. To better understand and predict the effects of heat treatment, samples that had been isothermally annealed at various temperatures from 500ºC to 800ºC for either 2h or 5h were examined by several methods to determine the diffusion effects taking place during annealing. Samples were examined by XRD, both at the coating surface and at multiple depths within the coating. Optical microscopy and SEM were used to view the structure of the coating in cross-section. Cross sections were etched and examined by optical microscopy and SEM, as well as EDS, which was used to develop a Ni-Fe composition profile at the coating-substrate interface. Microhardness measurements were taken and used to develop microhardness profiles. Additional samples were annealed to investigate boron oxidation at the coating surface. Based on the data, there is a reduced amount of Ni3B near the outer surface of the heat-treated coatings, with the thickness of the resultant γ-Ni layer increasing with annealing time and temperature, from 2.4 to just over 13 µm. This low-boron region indicates that boron is diffusing out through the surface of the coating and oxidizing, which the literature indicates should result in the formation of B2O3. Because B2O3 is water-soluble, it is likely that it dissolved during the water quench that concluded most anneals. Diffraction and EDS data also indicate interdiffusion of the nickel in the coating and the iron in the steel substrate. This leads to the formation of a soft interdiffusion layer between the Ni3B coating bulk and steel substrate that appears to be a mix of ferrite and Ni3Fe.
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Tan, Vincent Tandean. "Heat treatment optimization in the manufacture of Wilson Rockwell steel hardness test blocks." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/55236.
Full textAbstract:
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 84-85).
The heat-treatment process in the manufacture of Wilson Rockwell steel hardness test blocks often produces parts which are inconsistent in the mean hardness and hardness uniformity. In this thesis, the sources of variation in the mean hardness and hardness uniformity of the test blocks are identified by means of metallurgical study and Design of Experiments methodology. The uniformity of temperature distribution within the heating chamber and the effect of temperature and material composition on the final microstructure of the steel are analyzed. The hardness measurements and preparation of metallographic specimens follow the standards defined by the American Society for Testing and Materials (ASTM). Several control factors including soak temperature, soak time and location within the heating furnace are included in the Design of Experiment. The effects and interactions of control factors are studied using analysis of variance (ANOVA) techniques. Response Surface Methodology (RSM) was used to minimize the hardness variation on the interaction of the control factors. The heat-treatment experiment indicated that non-uniform temperature distribution within the heating chamber resulted in test blocks of different mean hardness in a batch run. The experiment also demonstrated that hardening temperatures below the homogeneous austenite formation temperature resulted in a large hardness variation. Several control factors and interaction between the factors that are significant on the mean hardness and hardness variation are identified. And finally, recommendations of control factor settings that minimize the hardness variation are presented in this thesis.
by Vincent Tandean Tan.
M.Eng.
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Okhrimenko, V. O., Оксана Петрівна Гапонова, Оксана Петровна Гапонова, and Oksana Petrivna Haponova. "Effect of heat treatment on structure and properties of austenite-martensite stainless steel." Thesis, Sumy State University, 2016. http://essuir.sumdu.edu.ua/handle/123456789/46865.
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Demands to new technics and mechanisms in various conditions increasing every year. Parts and equipment of enterprises are often subjected to cavitation erosion-wear; so problems of wear resistance and durability of machine parts is one of the main tasks of modern science. This type of wearingis characteristic for details of pumps, pipelines and other equipment under intensive motion of single- and multiphase liquids. Therefore, they use high-strength stainless steels based on: Fe-Cr-Ni-Mo and Fe-Cr-Ni-Co-Mo systems, which are a combine of mechanical properties and highprocessability.
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Aussaguel, Pierre. "A simplified finite element simulation for hard turning 52100 steel." Thesis, Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/19609.
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Burrow, Andrew Charles. "A model of the argon oxygen decarburization process for refining stainless steel and alloys." Thesis, 2015. http://hdl.handle.net/10539/16476.
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Mukuku, Kelvin. "Thermodynamic and parametric modeling in the refining of high carbon ferrochromium alloys using manually operated AODs." Thesis, 2017. https://hdl.handle.net/10539/24239.
Full textAbstract:
M.Sc. (50/50) Research project submitted to
School of Chemical and Metallurgical Engineering, Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, South Africa
July 2017This study and the work done involves investigating the effects of different parameters on the decarburization process of high carbon ferrochromium melts to produce medium carbon ferrochrome, and takes into account the manipulation of the different parameters and thermodynamic models based on actual plant data. Process plant data was collected from a typical plant producing medium carbon ferrochrome alloys using AODs. The molten alloy was tapped from the EAF and charged into the AOD for decarburization using oxygen and nitrogen gas mixtures. The gases were blown into the converter through the bottom tuyeres. Metal and slag samples and temperature measurements were taken throughout the duration of each heat. The decarburization process was split into two main intervals namely first stage blow (where carbon content in the metal bath is between 2-8 wt. % C) and second stage blow (carbon mass% below 2 wt. %). The first and second blow stages were differentiated by the gas flow rates whereby the first stage was signified by gas flow ratio of 2:1 (O2:N2), whilst the stage blow had 1:1 ratio of oxygen and nitrogen respectively. The effect of Cr mass% on carbon activity and how it relates to rate of decarburization was investigated, and the results indicated that an increase in Cr 66.54 – 70.5 wt. % reduced carbon activity in the metal bath from 0.336 – 0.511 for the first blowing stage. For the second blowing stage, the increase in Cr mass % of 67.22 – 71.65 wt. % resulted in an increase in C activity from 0.336 – 0.57. The trend showed that an increase in chromium composition resulted in a decrease in carbon activity and the same increase in Cr mass% resulted in reduced carbon solubility. Based on the plant data, it was observed that the rate of decarburization was time dependent, that is, the longer the decarburization time interval, the better the carbon removal from the metal bath. An interesting observation was that the change in carbon mass percent from the initial composition to the final (Δ%C) decreased from 10.18 – 8.37 wt. % with the increase in Cr/C ratio from 8.37 – 10.18. This effect was attributed to the chromium affinity for carbon and the fact that an increase in chromium content in the bath was seen to reduce activity of carbon. It was also observed that the effect of the Cr/C ratio was more significant in the first stage of the blowing process compared to the second blowing stage. A mass and energy balance model was constructed for the process under study to predict composition of the metal bath at any time interval under specified plant conditions and parameters. The model was used to predict the outcome of the process by manipulating certain parameters to achieve a set target. By keeping the gas flow rates, blowing times, gas ratios and initial metal bath temperature unchanged, the effect of initial temperature on decarburization in the converter was investigated. The results showed that the carbon end point with these parameters fixed decreased with increasing initial temperature, and this was supported by literature. The partial pressure of oxygen was observed to increase with decrease in C mass % between the first and second blow stages. For the second stage blow the partial pressure changed from 5.52*10-12 – 2.1*10-10 and carbon mass % increased from 0.754 – 2.99 wt. %. A carbon mass % of 7.87 had an oxygen partial pressure of 4.51*10-13 whilst a lower carbon content of 1.53 wt. % had an oxygen partial pressure of 8.06*10-11. The CO partial pressure however increased with increase in carbon composition in the metal bath. When the oxygen flow rate increased, a corresponding increase in the carbon removed (Δ%C) was observed. For the first stage of the blowing process, an increase in oxygen flow rate from 388.67 – 666.5Nm3 resulted in an increase in carbon removed from 5.06 – 7.28 wt. %. The second blowing stage had lower oxygen flow rates because of the carbon levels remaining in the metal bath were around +/- 2 wt. %. In this stage oxygen flow rates increased from 125 – 286.67 Nm3 and carbon removed (Δ%C) from 0.16 – 2.093 wt. %. The slag showed that an increase in basicity resulted in an increase in Cr2O3 in the slag. As the basicity increased from 0.478 – 1.281, this resulted in an increase in Cr2O3 increase from 0.26 – 0.68. Nitrogen solubility in the metal bath was investigated and it was observed that it increased with increasing Cr mass %. The increase in nitrogen solubility with increasing Cr mass % was independent of the nitrogen partial pressures.
MT2018
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Cho, Liang-Yih, and 卓良憶. "Effect of Austempering Heat Treatment on Erosion Wear of Ductile Iron and 4340 Alloy Steel." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/96914492119948318741.
Full textAbstract:
碩士大同大學
材料工程研究所
89
This research applied austempering heat treatment to obtain various microstructures in the matrix of ductile iron and AISI 4340 steel and studied their erosion wear behavior. The effects of different impact angle and microstructure on erosion wear rate and morphology were investigated. Mechanical property evaluation together with SEM analysis were also carried out to correlate the wear behavior observed.The results showed that after austempering hardness increased substantially. Impact toughness of ductile iron increased but AISI 4340 steel decreased. After erosion tests, it was determined that the wear rate of both materials were similar. However, at low angle (15 ) and high angle (90 ) impact angle, heat treated 4340 steel seemed to possessed better wear resistance than ductile iron. SEM observation revealed that cavities formed at where the spheroidal graphites located. Due to poor impact wear resistance of the graphite, they fell off from the matrix in early stage of the shot blasting leaving a hole behind that acclerated the peeling off effect of the ductile iron. Higher hardness enhanced eorsion wear resistance from the ability of sustaining deformation and peeling off effects.
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RAMLI and 洛建偉. "Effects of Heat treatment on the Microstructure and Mechanical Properties of SACM 645 Alloy Steel." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/zwhyba.
Full textAbstract:
碩士南臺科技大學
機械工程系
105
The purpose of this research is to observe and study the influence of hardening and tempering processes on microstructures and mechanical properties of SACM 645 steel by using several characterization techniques which include optical microscopy, hardness testing, tensile testing, fatigue testing, X-ray diffraction and scanning electron microscopy. In the present study, effects of the nitriding treatments on the material properties of the steel were also investigated. The heat treatment condition conducted in this research consists of hardening at 925 ˚C and then tempering at 540˚C, 560˚C, 580˚C as well as nitriding treatment at 530˚C. The experimental results related to the influences on microstructure and mechanical properties of SACM 645 steel induced the following conclusions. When the SACM 645 steel was first hardened at 925˚C treated and then tempered at 580˚C, the elongation of the SACM 645 steel will increase further from 6% to 20% and the number of cycles of failure will increase from 12509 cycles to 63314 cycles with the stress of fatigue limit 693.4 MPa or 120 Kg weights, this result indicating that after tempering at 580˚C the fatigue behavior of the SACM 645 steel rose five times in exceeding the without tempering specimen in this study. These results seem to be related to the formation of tiny and homogeneous structures on the tempering at 580˚C specimens. After nitriding treatments at 530˚C for 40 hours, the fatigue limit of SACM 645 steel greatly increased to 1351587 cycles. Moreover after nitriding treatments the microhardness of SACM 645 also significantly rose to ± 1100 HV0.1. Keywords: Tempering, Nitriding, Microstructure, elongation, Fatigue.
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Yu, Chun-hsin, and 尤俊鑫. "The Effect of Heat Treatment on Mechanical Properties of Low Alloy Ni-Cr-Mo Forging Steel." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/27632048877024699246.
Full textAbstract:
碩士國立高雄應用科技大學
機械與精密工程研究所
101
This study was conducted using quenching and tempering temperature heat treatment conditions change, to explore the relationship between the mechanical properties of low-alloy nickel-chromium-molybdenum forged steel with the help of microstructure. Experimental results show that low-nickel-chromium-molybdenum alloy for- ged steel hardened and then subjected to different tempering temperature te- mpering organization, will lead to massive as the tempering temperature ferrite (Blocky ferrite) grains become larger, while the acicular ferrite (Acicular ferri- te) then becomes relatively small. after hardening - heat treatment after the ten- sile strength, yield strength and hardness values are tempering temperature inc- reases with decreasing; impact toughness will follow the tempering temperat- ure increases. Quenching - heat treatment after tensile and impact fracture surface of the dimple ductile failure mode, as the tempering temperature will become more apparent. the low-temperature tempering conditions of its ductile fracture surface in addition to outside, there will be splitting failure mode char- acterized by brittle fracture occurs locally.
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LIN, YUEH-FENG, and 林岳鋒. "The Heat Treatment condition effect on the Mechanical Properties and Micro Structure of alloy SNCM Steel." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/4669k8.
Full textAbstract:
碩士國立高雄科技大學
機械工程系
107
Today's applications for metal materials are expanding. The requirements for wear resistance, fatigue resistance, high strength, and corrosion resistance of materials are becoming increasingly stringent. After various processing conditions, common components such as engine linkages, engine shafts, gears or chains play the most effective role. It can add elements of different compositions to improve the ductility, toughness, and rigidity of the material to extend the development of missiles, bullets, and fighter parts of the defense technology industry. Because of the different usage, different loading, and different environmental needs, materials with various characteristics of heat treatment, such as temperature quenching, tempering, cooling, are required to meet various conditions of use.Thus, the effect of heat treatment on metals is a very important research field. This research mainly studies the influence of heat treatment on the mechanical properties of SNCM materials, and the changes of grain-boundary, grain size, precipitate, etc. of the specimens after metallographic observation test to further understand the properties of the material. The experimental results show that the material with heat treatment has more than twice the stress-strain than the material without heat treatment. It can be seen through (OM) that the material that has been heat treated has a distinct ferritic carbon-iron phase, while the material that has not been heat-treated has more carbon precipitates at the grain boundary.