This paper discusses technical problems related with casting of titanium alloys in centrifugal vacuum furnaces. The potentials of an analysis of the centrifugal casting process carried out in the Flow3D software CFD (Computational Fluid Dynamics) were presented. Simulations were carried out on a model set, which enables casting of two connecting rods for an I.C. engine. Changes in the mould filling process were examined for the three selected spinning velocities of the casting arm. The ranges of the metal flow velocity in mould were calculated as well as metal pressure in mould after reaching a predetermined spinning velocity. The results and the adopted mould geometry enabled determination of the magnitude of stress occurring in mould at the time of filling it with liquid titanium alloy. The paper presents a methodology for testing of the ceramic material strength using a four-point loading arrangement. The strength of the ceramic material was determined on samples heated at different temperatures. The obtained results enabled a thesis to be formulated that for pouring of moulds in a centrifugal vacuum furnace, the layered foundry ceramic moulds can be safely used, and the use of moulds that will provide the directional solidification of metal should be possible as well.Keywords: Centrifugal casting, innovative casting materials, titanium alloys, liquid ceramic slurries, ceramic mould W artykule przedstawiono problemy techniczne związane z odlewaniem stopów tytanu w próżniowych piecach odśrod-kowych. Zaprezentowano możliwości analizy procesu zalewania wirującej formy przeprowadzonej w programie Flow3D CFD (Computational Fluid Dynamics). Obliczenia symulacyjne prowadzono dla zestawu modelowego umożliwiającego odlanie dwóch korbowodów silnika spalinowego. Analizowano zmiany sposobu wypełniania formy dla trzech wybranych prędkości wirowania ramienia odlewniczego. Obliczono zakresy prędkości przepływu metalu w formie oraz ciśnienia metalu występują-cego w formie po osiągnięciu założonej prędkości obrotowej. Uzyskane wyniki oraz przyjęta geometria formy pozwoliły na wyznaczenie wielkości naprężeń występujących w formie w momencie wypełnienia jej ciekłym stopem tytanu. Przedstawiono metodykę badania wytrzymałości materiału ceramicznego wykorzystującego czteropunktowy układ obciążający. Wyznaczono wytrzymałość materiału ceramicznego dla próbek wygrzewanych w różnych temperaturach. Otrzymane wyniki pozwalają na przedstawienie tezy, że w podczas zalewania form w próżniowym piecu odśrodkowym będzie można bezpiecznie wykorzystywać warstwowe ceramiczne formy odlewnicze, oraz będzie możliwe zastosowanie form zapewniających założone kierunkowe krzepnięcie metalu.
In the evaporative pattern casting process, the surface of a polystyrene pattern (Styrofoam) is coated with a ceramic layer. This ceramic layer, which coats the evaporative pattern, should have specific physiochemical properties including: resistance to thermal, chemical, and erosive activity of molten metal and proper permeability for gases which are produced by the evaporative polystyrene pattern. The article presents the research results of properties of experimentally selected ceramic layers applied on a polystyrene pattern in the evaporative pattern casting process.Keywords: evaporative patterns, Lost Foam, ceramic layer, properties W procesie wytwarzania odlewów wg metody modeli zgazowywanych na modele polistyrenowe (styropianowe), nakładana jest warstwa pokrycia ceramicznego. Pokrycie ceramiczne, które jest nanoszone na model zgazowywany powinno charakteryzować się określonymi właściwościami fizykochemicznymi w tym: odpornością na termiczne, chemiczne i erozyjne działanie ciekłego metalu oraz odpowiednią przepuszczalnością gazów wytworzonych z zgazowywanego modelu polistyrenowego. W artykule przedstawiono wyniki badań własności, wytypowanych doświadczalnych powłok ceramicznych, nanoszonych na model polistyrenowy w procesie modeli zgazowywanych.
The article presents an analysis of the applicability of the Replicast CS process as an alternative to the investment casting process, considered in terms of the dimensional accuracy of castings. Ceramic shell moulds were based on the Ekosil binder and a wide range of ceramic materials, such as crystalline quartz, fused silica, aluminosilicates and zirconium silicate. The linear dimensions were measured with a Zeiss UMC 550 machine that allowed reducing to minimum the measurement uncertainty
The paper presents the effect of suction pressure exerted on the liquid AlSi alloy when it is introduced into a ceramic mould made in the investment process and the results compared with data obtained on gravity poured castings. The study used special pattern sets and ceramic moulds made with the alternately applied soluble silicate binder and ethyl silicate. Additionally, self-supported moulds based entirely on the Ekosil binder were used. In the analysis of castings, the following parameters were examined: a linear dimensional accuracy, the state of surface microgeometry and the possibility of metal penetration into a complex ceramic mould, allowing also for the presence of capillary phenomena. In the process of casting with back-pressure, the pressure values of 500 hPa, 600 hPa and 700 hPa were applied in the chamber where the ceramic mould was located, with the temperature of the said mould kept at a level of 150 ± 10°C. Keywords:Casting with back-pressure, Investment casting process, Capillarity phenomena Current state of the problemThe process of casting with back-pressure, developed by Hitchiner Manufacturing Co., is one of the most modern and promising methods for making high-accuracy castings, also by the lost wax process. Typical applications for castings made with the back-pressure are disclosed in [1,2,3,4,5]. Those studies also evaluate, in a very general way, parameters such as the dimensional accuracy, surface microgeometry, and the like ones.The quality of castings made in the process using backpressure has been discussed in more detail in [6,7]. This paper presents a comprehensive comparison of the process using back-pressure and the traditional lost wax process, following the adopted criteria for casting quality evaluation.2. Studies of the accuracy of ceramic mould filling with liquid AlSi9 aluminium alloy in the process using back-pressure and in the common investment casting process
Extremely intense development of civilization requires from foundry casting technologies very high quality and not expensive castings. In the foundries, there are many treatments that allow increasing of the final properties of produced castings such as refining, modification, heat treatment, etc. One of the methods of increasing the quality of the casting by removing inclusions from the liquid alloy is filtration. The use of ceramic-carbon foam filters in filtration process is still analysed phenomenon that allows improving the final properties of castings. A modern method of research, testing and synthesis of innovative chemical compositions allows improving the properties of such filters. In the paper the evaluation of application properties of developed ceramic-carbon bonded foam filters is presented. The quality of the foam filters is evaluated by Computer Tomography and foundry trials in pouring of liquid metal in test molds. Additionally computer simulations were made to visualize the flow characteristics in the foam filter. The analysed filters are the result of the research work of Foundry Research Institute and the Institute of Ceramics and Building Materials, Refractory Materials Department in Gliwice.
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