138 MATERIA£Y CERAMICZNE /CERAMIC MATERIALS/, 63, 1, (2011), 138-142 www.ptcer.pl/mccm KEREM ALTUG GULER, ZEYNEP T ASLICUKUR, GOKHAN OZER Yildiz Technical University, Metallurgical and Materials Engineering Department, Istanbul, Turkey e-mail: kguler@yildiz.edu.tr 1. Introduction Investment (lost wax) casting is a widely used casting technique in which a pattern is usually made of wax [1]. In investment casting, a ceramic slurry is applied around a disposable pattern (wax and some kinds of plastics) and allowed to harden to form a disposable casting mould [2]. Investment casting is used in the automotive, aerospace and biomedical industries for the production of complex metal shapes. In this process, the shape to be reproduced is formed in wax and coated in a chemically bonded ceramic invest- ment material [3]. Investment casting allows dimensionally accurate components to be produced in high or low volumes. The production of the investment casting ceramic mould is a crucial part of the whole process and can be summarized as follows. First, multi-component slurries are prepared, which normally consist of a refractory ller and a binder system. A pattern wax is dipped into the face coat slurry, sprinkled with a coarse grained refractory stucco and dried. The rst or ‘primary’ coat applied to the wax will ultimately be in contact with the molten alloy, and its composition therefore often differs from that of secondary or ‘backup’ coats. The Expanded Polystyrene (EPS) Pattern Application in Investment Casting and Chemical Removing Abstract In this study, expanded polystyrene (EPS) was used as a pattern material in investment casting and removed chemically by acetone. It is shown that EPS is an alternative pattern material to the wax material which is used in the conventional investment moulding. EPS pattern usage and chemical removing change basically the investment moulding process. The ceramic shell moulds with wax and EPS patterns were produced at the same dimensions and with the same techniques. Unmodied A 413 Al-Si alloy was cast into these moulds. XRD and SEM characterizations were performed on the mould internal surfaces, and image, EDS and surface roughness analysis were carried out on the cast parts for comparison. The effects of chemical removing of patterns on the structure of mould internal surfaces were investigated. Keywords: Investment casting, EPS, Wax ZASTOSOWANIE MODELU Z POLISTYRENU EKSPANDOWANEGO W ODLEWANIU METOD TRACONEGO WOSKU I CHEMICZNYM USUWANIU W tych badaniach ekspandowany polistyren (EPS) zosta wykorzystany jako materia modelu do odlewania metod traconego wosku i usunity chemicznie za pomoc acetonu. Pokazuje si, e EPS jest alternatywnym materiaem w stosunku do wosku, który jest tradycyj- nym materiaem formy do odlewania metod traconego wosku. Uycie modelu z EPS i jego chemiczne usuwanie zmieniaj zasadniczo proces odlewania. Wykorzystujc model woskowy lub EPS wytworzono formy o czerepie ceramicznym o tych samych wymiarach i za po- moc tej samej techniki. Niemodykowany stop A 413 Al-Si odlewano w tych formach. Wykonano charakterystyki XRD i SEM wewntrz- nych powierzchni formy; analizy obrazu, EDS i chropowatoci powierzchni przeprowadzono dla porównania na odlewach. Zbadani wpyw chemicznego usuwania modeli na budow wewntrznych powierzchni formy. Sowa kluczowe: odlewania metod traconego wosku, EPS, wosk wax pattern is removed, normally by high pressure steam autoclave, leaving a hollow mould. Moulds are red and cast with molten metal. After cooling, the ceramic is removed by mechanical or chemical methods [4]. The waxes used in investment casting are blends of waxes, polymers and resins [5]. Dimensional accuracy is essential for successful casting. The casting discrepancy (the lack of t) has usually been viewed as some effects and one of these effects is thermal expansion of wax pattern [6]. The investment cast- ing process involves the making of a disposable wax pattern by injecting the wax into a metal mould. After their injection, wax patterns shrink in the dies due to thermal contraction during solidication and/or crystallization phenomena and subsequent cooling at the end of the dwell time [7]. The de-waxing process is probably one of the most com- plex stages of the investment casting process, where matters such as steam, investment shell, wax, and different phase changes have to be taken into account in order to obtain accurate results. Moreover, the shell is a complex composite material, which does not have a well known behaviour, and the presence of steam and water has a strong inuence on the shell thermal properties [5].