Casting

Casting, process of producing solid objects by pouring molten material into a shaped mold and allowing it to cool. Casting is used to shape such materials as glass and plastics, as well as metals and alloys.

The casting of metals has been practiced for more than 6,000 years, using first copper and bronze, then iron, and now alloys of zinc and other metals. The traditional method of casting metal is sand casting. Using a model of the object to be produced, a hollow mold is made in a damp sand and clay mix. Molten metal is then poured into the mold, taking its shape when it cools and solidifies. The sand mold is broken to release the casting. Permanent metal molds called dies are also used for casting, in particular, small items in mass-production processes where molten metal is injected under pressure into cooled dies (see Die-Casting). Continuous casting is a method of shaping slabs or sheets that involves pouring molten metal into the top of a hollow, water-cooled mold of the desired cross section and continuously withdrawing solid metal from the bottom. See Founding.