casting

The production of objects of desired form by pressing the raw material (e.g., alloys, fiberglass, plastics, steel) in liquid form into a suitably shaped mold. Both the mold and the pattern from which it is made may be either permanent or expendable.

Permanent-mold techniques include die casting, where the molten material is forced under pressure into a die; centrifugal casting, used primarily for pipes, the molten material being poured into a rapidly rotating mold (see centrifuge); and continuous casting, for bars and slabs, where the material is poured into water-cooled, open-ended molds. Most important of the expendable-mold processes is sand casting (founding): here fine sand is packed tightly around each half of a permanent pattern, which is removed and the two halves of the mold placed together. The material is poured in through a channel (sprue); after setting, the sand is dispersed. In some processes, the mold is baked before use to remove excess water. See also cast iron.

Related category

• INDUSTRIAL CHEMISTRY

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