The attempts to manufacture saturated composite castings With the use of a pressure casting machine
Jacek Jackowski Politechnika Poznańska, Instytut Technologii Materiałów, ul. Piotrowo 3, 61-138 Poznań
Annals 3 No. 6, 2003 pages 106-109
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abstract Saturated composite castings are usually produced with the use of autoclave equipment or by pressing of the charge in liquid state (squeeze casting). The first method enables maintaining better saturation conditions (and their monitoring), while the other considerably improves efficiency of the process. One of the reasons of porosity of saturated composite castings results from gas occlusions. They are unavoidable in the saturated castings, particularly in the case of pressing saturation. External pressure exerted on the matrix metal saturating the reinforcement should exceed the sum of pressures necessary for overcoming capillary pressures in the reinforcement under saturation, resistance of matrix flux through the capillary-porous reinforcement, and occlusion compression (Fig. 1). The attempts were made at producing saturated composite castings in a pressure casting die (Fig. 2) the ingate of large cross-section area, enabling operation with small velocity of saturating matrix metal flux. The pressure casting die was adapted for co-operation with the IDRA 320 pressure casting machine. Trial castings, of the shape of rectangular plates 70x60x20 mm, were obtained by saturating an aluminosilicate SIBRAL reinforcement with a technical AlSi11 alloy. The trial castings (Fig. 3) where then cut into parts (Fig. 4). Their porosities were determined based on measured densities (with a method of double weighing at an electronic analytical balance WPA 120K). Examples of porosity distribution of the casted composite materials obtained by reinforcement saturating for different external pressure values are shown in Figures 5 and 6. Preliminary trials proved the possibility of obtaining the saturated composite castings of porosity below 1 per cent, under conditions of a standard pressure-casting foundry, provided that small piston advance value and sufficiently rigid composite reinforcement are used. Key words: saturated composite castings