What is "cast iron"

Iron \I"ron\ ([imac]"[u^]rn), n. [OE. iren, AS. [=i]ren, [=i]sen, [=i]sern; akin to D. ijzer, OS. [=i]sarn, OHG. [=i]sarn, [=i]san, G. eisen, Icel. [=i]sarn, j[=a]rn, Sw. & Dan. jern, and perh. to E. ice; cf. Ir. iarann, W. haiarn, Armor. houarn.]

1. (Chem.) The most common and most useful metallic element, being of almost universal occurrence, usually in the form of an oxide (as hematite, magnetite, etc.), or a hydrous oxide (as limonite, turgite, etc.). It is reduced on an enormous scale in three principal forms; viz., cast iron, steel, and wrought iron. Iron usually appears dark brown, from oxidation or impurity, but when pure, or on a fresh surface, is a gray or white metal. It is easily oxidized (rusted) by moisture, and is attacked by many corrosive agents. Symbol Fe (Latin Ferrum). Atomic number 26, atomic weight 55.847. Specific gravity, pure iron, 7.86; cast iron, 7.1. In magnetic properties, it is superior to all other substances.

   Note: The value of iron is largely due to the facility with which it can be worked. Thus, when heated it is malleable and ductile, and can be easily welded and forged at a high temperature. As cast iron, it is easily fusible; as steel, is very tough, and (when tempered) very hard and elastic. Chemically, iron is grouped with cobalt and nickel. Steel is a variety of iron containing more carbon than wrought iron, but less that cast iron. It is made either from wrought iron, by roasting in a packing of carbon (cementation) or from cast iron, by burning off the impurities in a Bessemer converter (then called Bessemer steel), or directly from the iron ore (as in the Siemens rotatory and generating furnace).

2. An instrument or utensil made of iron; -- chiefly in composition; as, a flatiron, a smoothing iron, etc.

   My young soldier, put up your iron.
   --Shak.

3. pl. Fetters; chains; handcuffs; manacles.

   Four of the sufferers were left to rot in irons.
   --Macaulay.

4. Strength; power; firmness; inflexibility; as, to rule with a rod of iron.

5. (Golf) An iron-headed club with a deep face, chiefly used in making approaches, lifting a ball over hazards, etc.

   Bar iron. See Wrought iron (below).

   Bog iron, bog ore; limonite. See Bog ore, under Bog.

   Cast iron (Metal.), an impure variety of iron, containing from three to six percent of carbon, part of which is united with a part of the iron, as a carbide, and the rest is uncombined, as graphite. It there is little free carbon, the product is white iron; if much of the carbon has separated as graphite, it is called gray iron. See also Cast iron, in the Vocabulary.

   Fire irons. See under Fire, n.

   Gray irons. See under Fire, n.

   Gray iron. See Cast iron (above).

   It irons (Naut.), said of a sailing vessel, when, in tacking, she comes up head to the wind and will not fill away on either tack.

   Magnetic iron. See Magnetite.

   Malleable iron (Metal.), iron sufficiently pure or soft to be capable of extension under the hammer; also, specif., a kind of iron produced by removing a portion of the carbon or other impurities from cast iron, rendering it less brittle, and to some extent malleable.

   Meteoric iron (Chem.), iron forming a large, and often the chief, ingredient of meteorites. It invariably contains a small amount of nickel and cobalt. Cf. Meteorite.

   Pig iron, the form in which cast iron is made at the blast furnace, being run into molds, called pigs.

   Reduced iron. See under Reduced.

   Specular iron. See Hematite.

   Too many irons in the fire, too many objects or tasks requiring the attention at once.

   White iron. See Cast iron (above).

   Wrought iron (Metal.), the purest form of iron commonly known in the arts, containing only about half of one per cent of carbon. It is made either directly from the ore, as in the Catalan forge or bloomery, or by purifying (puddling) cast iron in a reverberatory furnace or refinery. It is tough, malleable, and ductile. When formed into bars, it is called bar iron.

1660s, from cast (past participle adjective) "made by melting and being left to harden in a mold" (1530s), from past participle of cast (v.) in sense "to throw something in a particular way" (c.1300), especially "form metal into a shape by pouring it molten" (1510s). From 1690s as an adjective, cast-iron.

a. 1 (context not comparable English) Made of #Noun. 2 durable; tough; resiliant. 3 inflexible or without exception. n. A hard and brittle, but strong, alloy of iron, carbon, and silicon, formed by casting in a mould.

n. an alloy of iron containing so much carbon that it is brittle and so cannot be wrought but must be shaped by casting

Cast iron is a group of iron- carbon alloys with a carbon content greater than 2%. Its usefulness derives from its low melting temperature. The alloy constituents affect its colour when fractured: white cast iron has carbide impurities which allow cracks to pass straight through; grey cast iron has graphite flakes which deflect a passing crack and initiate countless new cracks as the material breaks; ductile cast iron which stops the crack from further progressing due to their spherical graphite "nodules".

Carbon (C) ranging from 1.8–4 wt%, and silicon (Si) 1–3 wt% are the main alloying elements of cast iron. Iron alloys with less carbon content are known as steel. While this technically makes the Fe–C–Si system ternary, the principle of cast iron solidification can be understood from the simpler binary iron–carbon phase diagram. Since the compositions of most cast irons are around the eutectic point (lowest liquid point) of the iron–carbon system, the melting temperatures usually range from , which is about lower than the melting point of pure iron.

Cast iron tends to be brittle, except for malleable cast irons. With its relatively low melting point, good fluidity, castability, excellent machinability, resistance to deformation and wear resistance, cast irons have become an engineering material with a wide range of applications and are used in pipes, machines and automotive industry parts, such as cylinder heads (declining usage), cylinder blocks and gearbox cases (declining usage). It is resistant to destruction and weakening by oxidation ( rust).

The earliest cast iron artefacts date to the 5th century BCE, and were discovered by archaeologists in what is now Jiangsu in China. Cast iron was used in ancient China for warfare, agriculture, and architecture. During the 15th century, cast iron became utilized for artillery in Burgundy, France, and in England during the Reformation. The first cast iron bridge was built during the 1770s by Abraham Darby III, and is known as The Iron Bridge. Cast iron is also used in the construction of buildings.