1,462 research outputs found

    Application of Machine Learning in the Control of Metal Melting Production Process

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    Abstract This paper presents the application of machine learning in the control of the metal melting process. Metal melting is a dynamic production process characterized by nonlinear relations between process parameters. In this particular case, the subject of research is the production of white cast iron. Two supervised machine learning algorithms have been applied: the neural network and the support vector regression. The goal of their application is the prediction of the amount of alloying additives in order to obtain the desired chemical composition of white cast iron. The neural network model provided better results than the support vector regression model in the training and testing phases, which qualifies it to be used in the control of the white cast iron production

    Age strengthening of gray cast iron: alloying effects and kinetics study

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    Age strengthening of gray cast iron has become a critical issue with metal casters trying to optimize their process for the closest conformance to properties. This necessitated more robust and precise methods to predict age strengthening. Most foundries use age strengthening behavior to cast at hight carbon equivalents to facilitate smaller gating systems. Also, it is well known in the casting industry that the tool life improves with aging. Hence these foundries require a model to predict aging behavior and accelerate the mechanism from days to hours. This research focuses on the methods of composition adjustments to control aging properties, creating a model to predict the aging behavior at different temperatures and understanding the mechanism of aging --Abstract, page iii

    Investment shell cracking

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    Shell cracking is the single greatest problem affecting investment casters. A clearer understanding of the factors affecting the melt profile of the wax can be gained using computational fluid dynamics (CFD) to model the interaction among 1) the thermal conductivity of the wax, 2) the thermal conductivity of the shell, and 3) the temperature of the autoclave during the autoclave de-waxing cycle. The most favorable melt profile results from a high autoclave temperature (438⁰K to 458⁰K) and saturated thermal conductivity of the shell (1.36 to 1.40 Wm⁻¹k⁻¹) in conjunction with a low wax thermal conductivity (0.33 Wm⁻¹k⁻¹). These parameters reduce the likelihood of shell cracking as a result of wax bulk expansion --Abstract, page iv

    Relationship between Solidification, Microstructures and Mechanical Properties of Magnesium Cast Alloys

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    This thesis analyses the solidification, the microstructure and the mechanical properties of several magnesium alloys. The objective is to establish correlations between them in order to predict the local mechanical properties of magnesium cast components. On one hand, the solidification times have been related to the grain sizes and on the other, the grain sizes to the tensile yield strength, as for example, using the Hall-Petch equation. These relationships are integrated into numerical models for the prediction of the local mechanical properties in castings. Moreover, the effect of the alloying elements in the mechanical properties and in the generation of the texture in HPDC magnesium alloys after uniaxial deformation has been analysed. This work is aimed at the aeronautic sector, specifically to substitute aluminium alloys in applications for the interior of commercial aircrafts. Four casting technologies and four alloys have been selected. The casting technologies are sand, investment, gravity die and high-pressure die-casting. Two of the selected alloys are commercial, the AZ91 and AM50 alloys. The commercial alloys are reference alloys for two new alloys. Three alloys, including the two commercial alloys, are based in the Mg-Al system. The fourth alloy is a higher strength magnesium alloy based in the Mg-Zn-Zr-Nd-Gd-Y system and designated as MRI207S. This investigation is divided into three sections. The first task is the production of magnesium castings and the acquisition of cooling curves. A variety of alloys have been cast obtaining several microstructures and consequently, different mechanical properties. The second section relates to the microstructural characterisation in as-cast and heat treated conditions. The applied heat treatment is the solution heat treatment and artificial aging (T6). In this section the precipitates of each alloy are identified, as well as the grain sizes in different areas and the fracture mechanisms. Precipitates increasing the strength are present in the new alloys. Moreover, texture generation in uniaxial deformation is analysed in order to investigate the effect of the alloying elements on the deformation mechanisms. The basal plane (0001) is oriented parallel to the loading direction. The obtained intensity is smaller than that obtained in wrought alloys. It has been concluded that the alloying elements have not affected the generation of the texture. The third section involves the mechanical characterisation. Tensile tests have been carried out in order to obtain the ultimate tensile strength, the tensile yield strength and the elongation of the material. The properties of the MRI207S alloy are close to the ones of the A357 aluminium alloy. Vickers microhardness tests have also been performed to see the influence of the kind of precipitates in mechanical properties. The morphology of the precipitates in the AZ91E alloy varies in the same zone, and, therefore, varying the local mechanical properties. Correlating the results obtained in these three sections, relationships between solidification time, grain size and tensile yield strength have been established for the new MRI207S gravity-cast alloy (cast by sand, investment and gravity die-casting).Hemen aurkezten den tesi honek hainbat aleazioren solidotzea, mikroegitura eta ezaugarri mekanikoak aztertzen ditu. Helburua euren arteko erlazioak ezarri eta galdatutako piezen ezaugarri mekanikoak igartzea da. Batetik solidotze denborak ale tamainarekin erlazionatu dira, eta bestetik ale tamainak trakzioko elastikotasun mugarekin, Hall-Petch ekuazioaren bidez adibidez. Lorturiko ekuazioak zenbakizko modeloetan sar daitezke galdaketako piezen lekuko ezaugarri mekaniko iragartzeko. Aleazio elementuek ezaugarri mekanikoetan duten eragina ere aztertu da. Bestalde, injekziozko magnesio aleazioen testura sorkuntza deformazio uniaxialean ere aztertu da. Lan hau sektore aeronautikoan kokatzen da, hegazkin komertzialen barne aplikazioetan aluminio aleazioak ordezteko asmoarekin. Lau galdaketa teknologia eta lau aleazio aukeratu dira. Lau teknologiak hondarrezko moldekatzea, argizari galduzkoa, maskorrezkoa eta injekzioa dira. Aukeraturiko aleazioen artean, bi komertzialak dira, AZ91 eta AM50 hain zuzen ere. Aleazio komertzialak erreferentzia moduan erabili dira beste bi aleazio berrirentzat. Hiru aleazio, tartean bi komertzialak, Mg-Al aleazio sisteman oinarriturik daude. Laugarren aleazioa erresistentzia handiagoko magnesio aleazio bat da, Mg-Zn-Zr-Nd-Gd-Y sisteman oinarritua eta MRI207S deiturikoa. Hiru etapa nagusi bereizi dira. Lehenengoa magnesio piezen galdaketa eta hozketa kurben neurketan oinarriturik dago. Etapa honetan hainbat aleazio galdatu dira mikroegitura desberdinak eta ondorioz, ezaugarri mekaniko desberdinak lortzearren. Bigarren etapa karakterizazio mikroegituralaz arduratzen da. Aleazio bakoitzean agerturiko prezipitatuak, ale tamainak eremu desberdinetan eta haustura mekanismoak aztertu dira. Aleazio berrietan, materialaren erresistentzia hobetzen duten prezipitatuak aurkitu dira. Bestalde, testuraren garapena aztertu da deformazio uniaxialean. Helburua aleazio elementuek deformazio mekanismoetan duten eragina aztertzea izan da. (0001) planoa karga norabideari paralelo orientatzen da eta lorturiko intentsitatea forja aleazioetan emandakoa baino txikiagoa da. Aleazio elementuek testura sorreran eraginik izan ez dutela ere erakutsi da. Hirugarren fasea karakterizazio mekanikoari buruzkoa da. Trakzio saiakuntzak egin dira aleazio desberdinen haustura erresistentzia, elastikotasun muga eta luzapena ezagutzeko asmoz. MRI207S aleazioak A357 aluminio aleazioaren pareko ezaugarri mekanikoak ditu. Honenbestez, aluminio aleazioak ordezkatzeko posibilitate handiak ditu aleazio honek. Mikrogogortasun neurketak ere egin dira AZ91 aleazioan prezipitatu motek ezaugarri mekanikoetan duen eragina jakiteko asmoz. Prezipitatuen morfologia aldakorra da eremu jakin batean, eta ondorioz, lekuko ezaugarri mekanikoak ez dira konstanteak. Hiru etapa hauetan lorturiko emaitzak batuz, solidotze denboraren, ale tamainaren eta elastikotasun mugaren arteko erlazioak garatu dira MRI207 aleazio berriarentzat hondarrezko moldekatzeaz, argizari galdukoaz edo maskorrezkoaz galdatzen den kasuetarako.La presente tesis analiza la solidificación, la microestructura y las propiedades mecánicas de varias aleaciones de magnesio con el fin de establecer correlaciones entre ellas y predecir las propiedades mecánicas locales en piezas fundidas. Se han relacionado los tiempos de solidificación con los tamaños de grano por un lado y por el otro los tamaños de grano con el límite elástico a tracción, como por ejemplo mediante la ecuación de Hall-Petch. Estas relaciones se integran en modelos numéricos para la predicción de propiedades mecánicas locales en piezas de fundición. Así mismo, se ha analizado el efecto de los aleantes en las propiedades mecánicas y en la generación de la textura de las aleaciones de magnesio inyectadas tras deformación uniaxial. El trabajo realizado se enmarca dentro del sector aeronáutico, concretamente con el fin de sustituir aleaciones de aluminio para aplicaciones del interior de aviones comerciales. Se han seleccionado cuatro tecnologías de fundición y cuatro aleaciones. Las cuatro tecnologías son el moldeo en arena, la cera perdida, el moldeo en coquilla por gravedad y la inyección. Entre las aleaciones seleccionadas, dos son comerciales, siendo estas la AZ91 y la AM50. Las aleaciones comerciales se han utilizado como referencia para las dos nuevas aleaciones. Tres aleaciones, incluyendo las dos comerciales, se basan en el sistema Mg-Al. La cuarta aleación es una aleación de magnesio de mayor resistencia basada en el sistema Mg-Zn-Zr-Nd-Gd-Y y denominada MRI207S. Se han distinguido tres fases principales. La primera fase consta de la producción de fundiciones de magnesio y la adquisición de curvas de enfriamiento. Se ha fundido una diversidad de aleaciones con varias microestructuras y por consiguiente, con diferentes propiedades mecánicas. La segunda fase trata de la caracterización microestructural antes y después del tratamiento térmico. El tratamiento térmico empleado ha sido el de solubilizado, temple y envejecimiento artificial (T6). En esta fase se han identificado los precipitados presentes en cada aleación, los tamaños de grano en diferentes zonas y los mecanismos de fractura. En las nuevas aleaciones se han detectado varios precipitados que mejoran la resistencia. Así mismo, se ha analizado la evolución de la textura durante la deformación uniaxial para analizar el efecto de los elementos de aleación en los mecanismos de deformación. En la deformación, el plano basal (0001) se orienta paralela a la dirección de carga, siendo la intensidad obtenida menor que la obtenida en las aleaciones forjadas. Así mismo, se ha detectado que los aleantes no han afectado a la evolución de la textura. La tercera fase es sobre la caracterización mecánica. Se han realizado ensayos de tracción para el establecimiento del límite a rotura, el límite elástico y el alargamiento. La aleación MRI207S muestra propiedades mecánicas cercanas a las de la aleación de aluminio A357 fundidas. También se han efectuado ensayos de microdureza para establecer la influencia que tiene el tipo de precipitado en las propiedades mecánicas. La morfología de los precipitados en el caso de la aleación AZ91E varía en una misma zona, variando así sus propiedades mecánicas locales. Relacionando los resultados obtenidos en estas tres fases, se han establecido correlaciones entre el tiempo de solidificación, el tamaño de grano y el límite elástico para la nueva aleación MRI207S fundida por gravedad (moldeo en arena, a la cera perdida y en coquilla por gravedad)

    Advanced Lost Foam Casting Technology - Phase V

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    Precision Casting via Advanced Simulation and Manufacturing

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    A two-year program was conducted to develop and commercially implement selected casting manufacturing technologies to enable significant reductions in the costs of castings, increase the complexity and dimensional accuracy of castings, and reduce the development times for delivery of high quality castings. The industry-led R&D project was cost shared with NASA's Aerospace Industry Technology Program (AITP). The Rocketdyne Division of Boeing North American, Inc. served as the team lead with participation from Lockheed Martin, Ford Motor Company, Howmet Corporation, PCC Airfoils, General Electric, UES, Inc., University of Alabama, Auburn University, Robinson, Inc., Aracor, and NASA-LeRC. The technical effort was organized into four distinct tasks. The accomplishments reported herein. Task 1.0 developed advanced simulation technology for core molding. Ford headed up this task. On this program, a specialized core machine was designed and built. Task 2.0 focused on intelligent process control for precision core molding. Howmet led this effort. The primary focus of these experimental efforts was to characterize the process parameters that have a strong impact on dimensional control issues of injection molded cores during their fabrication. Task 3.0 developed and applied rapid prototyping to produce near net shape castings. Rocketdyne was responsible for this task. CAD files were generated using reverse engineering, rapid prototype patterns were fabricated using SLS and SLA, and castings produced and evaluated. Task 4.0 was aimed at developing technology transfer. Rocketdyne coordinated this task. Casting related technology, explored and evaluated in the first three tasks of this program, was implemented into manufacturing processes

    Computers in Foundries

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    Computers have now entered into the foundryengineering. Foundry mechanization and modernizationare of considerable importance today when the foundryhas evolved from an ancient art into a modern scienceand it is fully controlled and monitored by computers.Modernization is the only key to improve casting qualityand productivity. From industrial point of view, theyhave been in use in the administrative areas of finance,accounting, personnel records, wage, salaries, andinventory control for a long period. Many foundry machinesystems are computerized. Due to the entry of computersin foundries, fatigue and strain on the workers and staffshave been considerably reduced during working andwork culture has improved tremendously. Improved workculture can lead to a sense of participation, involvement,and creativity. This review paper discusses on the role,prospects, and application of computers in foundries.Besides, an introduction on the computer aided foundrymodel design and computer aided foundry die design arepresented precisely in this paper. It also discusses on thenumerical simulation of casting solidification performed infoundries and a brief information about the computerizedand automated foundry line have been provided in thistechnical paper. The applications of expert systems infoundries and various types of foundry software packagescommonly used in the metal casting industries areexplained in detail in this review paper
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