A foundry is a factory which produces castings of metal, both ferrous and non-ferrous. Ferrous metals are iron-based. The element iron is the most common base element poured in foundries. Non-ferrous metals are all other cast alloys.
In foundries, molten metal is poured into molds. Such molds may be made of sand, metal (permanent molding) or other ceramic or refractory materials. The pouring can be accomplished with gravity, or may be assisted with vacuum or pressurized gasses. When the metal freezes (changing from liquid to solid) the result is a casting.
Most foundries specialize in particular metals, and have furnaces dedicated to these. For example an iron foundry (for cast iron) may use a cupola, similar to a small blast furnace, while a steel, bronze or brass foundry will normally use an electrical induction furnace or in some cases a gas heated crucible furnace. Most aluminum foudries use either an electric resistance or a gas heated crucible furnace.
Furnaces in foundries are designed according to the type of metal being cast and the fuel available that will produce the desired temperature. Melting furnaces may range from a few hundred degrees (for low temperature melting point alloys, such as zinc or tin) to over 3000 degrees (for steels, nickel based alloys, tungsten and other elements and alloys with high melting points). The fuel used may be electricity, natural gas or propane, charcoal, coke (a by product of coal), fuel oil, or even wood. These furnaces are basically insulated vessels with a heat source created by the fuel. Furnaces can be any size, ranging from mere ounces to hundreds of tons.