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An iron foundry is an industrial installation that produces iron castings or molded items. These installations or factories feature a multi-step process that involves the melting of iron stock in furnaces, then pouring the molten metal into molds. Once the metal has cooled, the casting is removed from the mold, cleaned and all casting imperfections removed. Iron foundries are generally capable of producing small products weighing a couple of ounces to large castings weighing several tonnes. Various grades of iron are used to produce foundry pieces, including ductile and gray or cast iron.
Iron foundries are one of the oldest types of metal smelting operations and produce millions of tonnes of product each year. Common iron foundry cast pieces include machine and automobile parts, cookware, plumbing fittings and pipes. The iron casting process is suitable for producing iron and iron alloy pieces of great simplicity or complexity and in a wide range of sizes and weights, depending on demand. The process is relatively simple and consists of three basic steps: melting the iron, casting and finishing.
The raw materials used in iron foundry operations are melted in various types of furnaces depending on the desired grade of iron used and production quantities. The most simple of these and the oldest type of furnace is the crucible type. These furnaces consist of a large bowl-shaped crucible lined with refractory material into which the charge or raw material is placed. Heat is transferred to the charge through the walls of the crucible from a coke-, gas- or electrically-fueled heat source. Other iron foundry furnace types include cupola, induction and electric arc furnaces.
When the iron is melted, it is poured into molds to complete the casting step of the process. One of the most common foundry mold types is the sand mold. To produce sand molds, a pattern or model of the finished article is used to make a negative image impression in special molding sand. The molten iron is poured into the impression and left to cool and solidify. Other mold types include ceramic, ceramic-sand combination and metal molds.
Once the cast piece has cooled, it is removed from the mold and all mold references are removed. The piece is then sand blasted to remove all mold sand and to clean the surface. It is then machined or ground to ensure the piece is dimensionally correct with the desired surface finish. Several grades of raw iron stock and alloys thereof are used to produce iron foundry products, including ductile iron, cast or gray iron and malleable iron. These variants are produced by the addition of alloy materials or chemicals, different melting processes and by post-casting heat treatments. Most iron foundry facilities are capable of producing a wide variety of casting sizes, ranging from small machine parts to turbine impellers.