Machinery's Handbook, 31st Edition
CENTRIFUGAL CASTING
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Fig. 16. Centrifuge Casting: a) Mold; b) Final Casting Squeeze Casting
Squeeze casting (Fig. 17) combines casting and forging technologies. In contrast to other casting techniques in which a molten metal is poured or injected into the mold cavity after the two parts of the mold are assembled, a squeeze casting mold is closed after a por- tion of molten metal has been poured into the preheated bottom die. The applied pressure and instant contact of the molten metal with the die surface produce a rapid heat transfer condition that yields a pore-free, fine-grain casting with mechanical properties approach - ing those of a wrought product. Squeeze casting is easily automated to produce near-net to net shape high-quality components. Because of the high pressure applied during solidification, porosities caused by both gas and shrinkage can be prevented or eliminated. The cooling rate of the casting can be increased by applying high pressure during solidification, since that contact between the casting and the die is improved by pressurization, which results in the formation of fine- grained structures. With the current emphasis on reducing materials consumption through virtually net shape processing and the demand for higher-strength parts for weight savings, the emer- gence of squeeze casting as a production process has given materials and process en- gineers an alternative to traditional approaches to casting and forging. By pressurizing liquid metals while they solidify, near-net shapes can be achieved in sound, dense cast- ings. Squeeze casting is simple and economical, efficient in its use of raw material, has excellent potential for automated operation at high rates of production, and achieves the highest mechanical properties attainable in a cast product. The microstructural refine - ment and integrity of squeeze cast products are desirable for many critical applications.
Fig. 17. Sequence of Operations in Squeeze Casting Process: a) Pouring Molten Metal in Die; b) Closing Die and Applying Pressure; c) Casting Ejecting
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