RINFI, Repositorio Institucional Facultad de Ingeniería. UNMDP
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Austenite Dendrite Morphology in Lamellar Cast Iron
No full textPrimary austenite has been underestimated in general when the theories of nucleation, solidification, microstructure formation and mechanical properties was established for cast iron and particularly for lamellar cast iron. After extensive use of colour etching during the last two decades it has been found that primary austenite dendrites can be characterized using general morphology parameters like those used for other technical cast alloys with dendritic structure. The present work aims to investigate the primary austenite morphology of as-cast samples of a hypoeutectic lamellar cast iron produced with different cooling rates. Morphological parameters as the area fraction primary austenite, the secondary dendrite arm spacing, the dendrite envelope surface, the coarseness of the primary dendrite expressed as the relation between the volume of the dendrite and its envelope surface and the coarseness of the interdendritic space also known as the hydraulic diameter are measured. Furthermore the role of the size of investigation area is revealed be sequential investigation. A strong relation between all measured morphological parameters and the solidification time have been established excepting the volume fraction of primary austenite which is constant for all cooling conditions
Cast Iron Alloys for Exhaust Applications
No full textDownsizing of engines – gasoline as well as Diesel - helps to reduce CO2-emissions. Smaller engines at the same or even raised power levels result in higher exhaust gas temperatures. In personal cars, these are raised to above 850°C in Diesel engines and up to 1,050 °C for turbocharged gasoline engines. Ferritic Si- and Mo-alloyed ductile iron grades are standardised in Europe in EN-16’124. However, these materials are not sufficient for highly turbo charged engines. Based on SiMo ductile iron, new ferritic materials have been developed to raise ferrite/austenite transition temperature, high temperature strength and scaling resistance. The paper describes the development of new ferritic high temperature ductile iron grades, their properties, serial applications and newest achievements in realizing even higher working temperatures
Damage Evolution in Compacted Graphite Iron during Thermo-Mechanical Fatigue Testing
No full textThermo-mechanical fatigue (TMF) properties of a compacted graphite iron (CGI) in an out-of-phase (OP) configuration are investigated for different maximum temperatures and mechanical strain ranges. Furthermore, the stress-strain hysteresis loops are analysed and in particular the unloading modulus, i.e. the elastic modulus measured during specimen unloading, is obtained from each cycle. This material parameter has earlier been explicitly related to the amount of microcracking in cast irons. The results show that the unloading modulus linearly declines with the numbers of cycles in all tests performed. In addition, the rate of change of the unloading modulus is closely related to the number of cycles to failure. Accordingly, it is concluded that microcracks are independently propagated by fatigue until a point of rapid crack-linking resulting in the ultimate failure. This is supported by microstructural analyses consisting of optical microscope images taken at different stages throughout the life of a specimen
Modelling of Density Changes of Nodular Cast Iron During Solidification by Cellular Automaton
Get PDFResults of predictions of nodular cast iron density changes during solidification are presented. These changes were calculated by using a mathematical model which bases on a Cellular Automaton - Finite Differences (CA-FD) method. The CA-FD model takes into account, among others, the independent nucleation of graphite and austenite as a function of undercooling, the migration rate of the grains’ borders, non-uniform distribution of temperature and concentration in the calculation domain, diffusion of the carbon in the liquid and the austenite. All simulation were performed at various: nucleation intensity and the eutectic saturation. It has been shown and proofed by other authors that the shrinkage phenomena take place at three stages: pre-eutectic shrinkage, eutectic expansion, and final shrinkage
Effects of Microstructure and Strength on Tool Wear in Rough Milling of Austempered Ductile Iron
Get PDFThe machinability of various grades of austempered ductile iron (ADI) has been investigated for rough milling operations. ADI 900, ADI 1050 and ADI 1200 grades were commercially produced, commercially heat treated, and machined under controlled conditions using coated carbide inserts with coolant in the laboratory. The milling performance of the various grades was compared to that of AISI/SAE 4340 with similar hardness. In this study, machinability characteristics relative to wear rate (ISO 8688-2) and machining forces were measured and related to initial microstructure and properties. These preliminary results have been used to establish initial rough milling machining guidelines for machining ADI with coated carbide milling inserts
Sistema de medición de contaminación sonora
No full textEn este informe se presenta el diseño y construcción de un prototipo de medición de contaminación sonora. Este proyecto surgió motivado por la necesidad de un monitoreo de parámetros ambientales realizado en conjunto por integrantes del Laboratorio de Comunicaciones de la Facultad de Ingeniería – UNMdP, del INTEMA y el Observatorio de la Ciudad de FASTA. El objetivo de este proyecto fue desarrollar y construir un equipo que pueda medir y almacenar de forma continua y automática parámetros relacionados con la contaminación sonora en un determinado intervalo de tiempo, para poder realizar posteriormente un análisis de los datos obtenidos. Además, se propuso que dicho prototipo pudiera calcular el espectro de potencia del sonido con una resolución mayor a los equipos comerciales que existen en el mercado.
Como objetivo secundario, se estableció el prototipo pueda ser utilizado para medir otros parámetros de contaminación ambiental al poder conectarle diferentes sensores para la medición de diferentes variables. Por último, el equipo también dispone de distintas alternativas de conectividad para monitorear los datos.
La importancia de poder conocer las fuentes de contaminación sonora con suficiente detalle radica en que, de esta manera, se pueden tomar medidas preventivas para preservar la buena salud auditiva y hasta psicológica de las personas en distintos ámbitos de sus vidas. También permite identificar si una lesión auditiva existente puede haber sido provocada por una fuente sonora a la que un individuo está expuesto cotidianamente, por ejemplo en un ambiente laboral.
Para llevar a cabo este objetivo se diseñó y construyó un equipo capaz de medir la energía total, el espectro de potencia y el valor eficaz del ruido ambiente, para luego ser almacenados a intervalos de tiempo programados en una memoria SD para su posterior análisis en una PC. Además se colocó una pantalla LCD para mostrar la energía medida instantáneamente. El objetivo de este equipo es que pueda ser instalado en el lugar de medición y que el relevamiento de los datos sea programado y de forma automática. Puede ser utilizado para monitorear contaminación sonora ambiental, en industrias y hasta en puestos de trabajo para conocer los niveles sonoros a los que está expuesto el trabajador. También puede ser utilizado para determinar si una lesión auditiva fue provocada por la exposición a un ruido puntual o es debida a otra fuente, al conocer en detalle las características (composición espectral) del mismo.
Como se mencionó el prototipo posee un módulo central capaz de realizar el cálculo de la energía total, el espectro de potencia y el valor RMS del ruido en tiempo real, a través de un DSP de bajo costo. Este módulo posee además la capacidad de manejar una memoria SD para almacenar los datos. Un segundo módulo comandado por un microcontrolador es utilizado para manejar un reloj de tiempo real (RTC), el cual se es utilizado para almacenar los datos con fecha y hora, y la pantalla del equipo en donde se muestran mediciones simples. Estos módulos se comunican a través de sus interfaces UART.
Pensando en una expansión del equipo, ante necesidades concretas, se optó por prepararlo para poder incorporarle distintos tipo de sensores; como pueden ser distintos tipos de gases, temperatura, presión, rayos UV y otros. También tiene la posibilidad de agregarle distintos tipos de conectividad como puede ser Bluetooth (para poder descargar los datos desde un dispositivo móvil), wifi (para poder acceder al equipo en forma remota), GSM (para acceder de modo remoto a lugares en donde no hay señal internet, pero si telefonía móvil), y hasta un conector serie en el equipo para poder conectarlo a una PC. Las posibles expansiones del equipo son contempladas en un conversor de protocolos, el cual se implementa en un tercer microcontrolador, el cual también está insertado en este prototipo.
Una vez construido el prototipo se realizaron pruebas, las cuales arrojaron resultados positivos en cuanto a la medición y almacenamiento del ruido; como así también la visualización de algunos parámetros en la pantalla de dicho equipo.
Es importante destacar que esta es una primera versión del equipo y que al poseer la capacidad de expandirse en cuanto a sus prestaciones, son numerosas las mejoras que este prototipo puede aceptar.
Por último, debido a una serie de aspectos novedosos en la implementación del equipo y a que se acreditó su utilidad industrial, fue posible que el desarrollo esté en vías de patentamiento a través de la Oficina de Vinculación Tecnológica del CONICET.Fil: Etcheverry, Juan Alberto. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; Argentin
Effect of Cu, Mn and Sn on Pearlite Growth Kinetics in as-Cast Ductile Irons
No full textIn a previously published work, pearlite growth in cast irons was investigated and it was claimed that growth kinetics of pearlite in nodular cast iron does not depend on alloying elements and that only the start temperature for the transformation is modified. Since then, the authors have investigated the effect of copper at low level of manganese and the combined effect of copper and tin at intermediate manganese contents. In the first case, thermal records confirmed that copper decreases the formation temperature for both ferrite and pearlite. In the second work, an optimised content for tin, manganese and copper was found so as to improve mechanical properties while keeping fully pearlitic structures. The thermal records obtained during this latter study are here used to estimate the pearlite growth kinetics and the effect of copper and tin on it. Tin has been shown to reduce pearlite undercooling (increase of start transformation temperature) and thus to favour the formation of this constituent
Trace elements and the control limits in ductile iron
No full textSince the invention and start of production of ductile iron in the 1940’s people working in the area have tried to find a way to easily control the final properties of the cast product. For this several different equations calculating the effect of trace elements have been developed. There are equations trying to predict nodularity, pearlite percentage (and thus ferrite), segregation, balancing harmful trace element content and so on. This paper reviews some of these equations and discusses their appropriate fields of use. Equations for predicting the appearance of degenerate and chunky graphite and how to balance the harmful trace elements are also discussed
Numerical Simulation of Dimensional Change During Austempering Heat Treatment in Ductile Cast Iron
No full textChanges in the form and dimensions of ductile iron parts occur during the austempering process, and this poses a challenge whenever tight tolerances need to be satisfied. Thus, it is important to be able to predict the deformation which occur under heat treatment to evaluate the minimum and maximum stock material required to perform the final machining. Moreover, parts could be machined before heat treatment under better mach inability condition. This paper presents a thermo-mechanical-metallurgical formulation to predict the dimensional changes and final microstructure of a ductile cast iron part as a consequence of the austempering heat process. A coupled thermal, mechanical and metallurgical problem is solved using a finite element method, to
take into account different coupled and complex phenomena present in this process. As an illustration, the heat treatment of a specimen is considered and results are validated by comparison with experimental data
Influence of the Furfurylmoulding Sand on the Flake Graphite Formation in the Surface Layer of Ductile Iron Castings
No full textThe results of investigations of the influence of molding sand with furan resin, prepared both with fresh sand and reclaimed matrix, on the formation of microstructure and flake graphite formation in the surface layer of ductile iron castings, are presented in this paper. A series of experimental melts of ductile iron in molds made of molding sand, characterised by different levels of surface-active elements (sulphur, oxygen) were performed. The effect of the wall thickness, and the initial temperature of the metal in the mould cavity on the formation of the flake (and compacted) graphite formation in the surface layer of the casting, is shown in the paper. Investigations carried out by Energy Dispersive Spectroscopy (EDS) and Wavelength Dispersive Spectroscopy (WDS), showed concentration gradient profiles of surface-active elements in the surface layer of castings which are responsible for their quality. Finally it has been shown that there exist a significant effect of the quality of the sand on the formation of the flake graphite layer and the surface characteristic of ductile iron castings