Cast iron

Iron-cementite meta-stable diagram
Pair of English firedogs, 1576. These, with firebacks, were common early uses of cast iron, as little strength in the metal was needed.
Cast-iron artifact dated from 5th century BC found in Jiangsu, China
Diorama model of a Han dynasty blast furnace blower
The Iron Lion of Cangzhou, the largest surviving cast-iron artwork from China, 953 AD, Later Zhou period
Cast-iron drain, waste and vent piping
Cast-iron plate on grand piano
Cast-iron waffle iron, an example of cast-iron cookware
The Iron Bridge over the River Severn at Coalbrookdale, England (finished 1779)
The Eglinton Tournament Bridge (completed c1845), North Ayrshire, Scotland, built from cast iron
Original Tay Bridge from the north (finished 1878)
Fallen Tay Bridge from the north

Class of iron–carbon alloys with a carbon content more than 2%.

- Cast iron

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Gray iron

Micrograph of grey cast iron

Gray iron, or grey cast iron, is a type of cast iron that has a graphitic microstructure.

Ductile iron

Ductile iron microstructure at 100× magnification, showing carbon islanding effect around nodules.
Another micrograph showing the carbon islanding effect, with nodules surrounded by areas depleted of carbon

Ductile iron, also known as ductile cast iron, nodular cast iron, spheroidal graphite iron, spheroidal graphite cast iron and SG iron, is a type of graphite-rich cast iron discovered in 1943 by Keith Millis.


Alloy made up of iron with typically a few tenths of a percent of carbon to improve its strength and fracture resistance compared to other forms of iron.

Incandescent steel workpiece in this depiction of the blacksmith's art
Iron-carbon phase diagram, showing the conditions necessary to form different phases. Martensite is not shown, as it is not a stable phase.
Fe-C phase diagram for carbon steels; showing the A0, A1, A2 and A3 critical temperatures for heat treatments.
Iron ore pellets for the production of steel
Bloomery smelting during the Middle Ages
A Bessemer converter in Sheffield, England
A Siemens-Martin open hearth furnace in the Brandenburg Museum of Industry.
White-hot steel pouring out of an electric arc furnace.
Steel production (in million tons) by country in 2007
Bethlehem Steel (Bethlehem, Pennsylvania facility pictured) was one of the world's largest manufacturers of steel before its closure in 2003
Forging a structural member out of steel
A roll of steel wool
A carbon steel knife
A steel bridge
A steel pylon suspending overhead power lines
A stainless steel gravy boat

The interaction of the allotropes of iron with the alloying elements, primarily carbon, gives steel and cast iron their range of unique properties.


Chemical element with symbol Fe and atomic number 26.

Molar volume vs. pressure for α iron at room temperature
Low-pressure phase diagram of pure iron
Magnetization curves of 9 ferromagnetic materials, showing saturation. 1.Sheet steel, 2.Silicon steel, 3.Cast steel, 4.Tungsten steel, 5.Magnet steel, 6.Cast iron, 7.Nickel, 8.Cobalt, 9.Magnetite
A polished and chemically etched piece of an iron meteorite, believed to be similar in composition to the Earth's metallic core, showing individual crystals of the iron-nickel alloy (Widmanstatten pattern)
Ochre path in Roussillon.
Banded iron formation in McKinley Park, Minnesota.
Pourbaix diagram of iron
Hydrated iron(III) chloride (ferric chloride)
Comparison of colors of solutions of ferrate (left) and permanganate (right)
Blue-green iron(II) sulfate heptahydrate
The two enantiomorphs of the ferrioxalate ion
Crystal structure of iron(II) oxalate dihydrate, showing iron (gray), oxygen (red), carbon (black), and hydrogen (white) atoms.
Blood-red positive thiocyanate test for iron(III)
Iron penta- carbonyl
Prussian blue
Iron harpoon head from Greenland. The iron edge covers a narwhal tusk harpoon using meteorite iron from the Cape York meteorite, one of the largest iron meteorites known.
The symbol for Mars has been used since antiquity to represent iron.
The iron pillar of Delhi is an example of the iron extraction and processing methodologies of early India.
Iron sickle from Ancient Greece.
Coalbrookdale by Night, 1801. Blast furnaces light the iron making town of Coalbrookdale.
"Gold gab ich für Eisen" – "I gave gold for iron". German-American brooch from WWI.
Iron powder
Iron furnace in Columbus, Ohio, 1922
17th century Chinese illustration of workers at a blast furnace, making wrought iron from pig iron
How iron was extracted in the 19th century
This heap of iron ore pellets will be used in steel production.
A pot of molten iron being used to make steel
Iron-carbon phase diagram
Photon mass attenuation coefficient for iron.
Structure of Heme b; in the protein additional ligand(s) would be attached to Fe.
A heme unit of human carboxyhemoglobin, showing the carbonyl ligand at the apical position, trans to the histidine residue

In the modern world, iron alloys, such as steel, stainless steel, cast iron and special steels, are by far the most common industrial metals, because of their mechanical properties and low cost.

Cast-iron architecture

A street in SoHo in New York City famous for its cast-iron facades.
Spa Colonnade in Mariánské Lázně, 1889. Nearly every element is cast iron.
Pont Des Arts, Paris, 1804
Summer Garden fence, Saint Petersburg, 1780s
Balustrade of Palace Bridge, Berlin, 1824
Mender Chocolate Factory, Noisiel
New Orleans cast iron 'gallery', c. 1850s
Regatta Hotel 1886, Toowong, Brisbane
Close-up view of cast-iron detailing at the Ca d'Oro Building in Glasgow, Scotland, erected in 1872
Crystal Palace, London, 1851
The structure of the glass roof of Milan's Galleria, 1865–77
Eglise St-Eugene Ste-Cecile
Pont Des Arts, Paris, 1804
Pontcysyllte aqueduct, North Wales, 1805
Ha'penny Bridge, Dublin, 1816
Commissioners House, Bermuda, 1820s
Cast iron balcony and railing, Arden House, Leamington Spa, England, 1832
Bourse de Commerce dome, Paris, 1811 (photo 1880s)
Kreuzberg Memorial, Berlin, 1821
Kitchen with palm tree cast iron columns, Royal Pavilion, Brighton, c. 1820
Sayn Foundry hall, Bendorf, Germany, 1830
Cast iron balcony, town hall, 9th arrondissement, Paris, c. 1830
St Isaac's Cathedral dome structure, c. 1838
Pevchesky Bridge, St Petersburg, 1840
Eisernes Haus, 1848, today part of Kunsthaus Graz
Bibliotheque Sainte-Genevieve, Paris, 1843–50
King Frederick Augustus Tower, Löbau, Germany 1852
Haughwout Building, Soho, NY, 1856-7
U.S. Capitol section, 1859
Salle Labrouste, Bibliothèque nationale de France, 1861–68
Watson's Hotel, Mumbai, 1869
Mercado Central, Santiago, Chile, 1869
Clevedon Pier, England, 1869, cast iron base structure
Sphinx bench, Victoria Embankment, London, 1877
Brighton Beach Bandstand, Brighton UK, 1884
Cast Iron building St Louis, Missouri
Cast iron fountain, Alexandra Park, Glasgow, 1901
Old cast-iron bench, Bad Kissingen, Germany
St Stephen's Bulgarian Church, Istanbul, 1898
Mikhailovsky Garden fence, St Petersburg, 1907
Lamps on Elgin Bridge (Singapore), 1929
Typical Sydney iron lace terrace houses in Woollahra, New South Wales, late 19th century

Cast-iron architecture is the use of cast iron in buildings and objects, ranging from bridges and markets to warehouses, balconies and fences.

Casting (metalworking)

Process in which a liquid metal is delivered into a mold that contains a negative impression (i.e., a three-dimensional negative image) of the intended shape.

Molten metal before casting
Casting iron in a sand mold
An investment-cast valve cover
The permanent molding process
Intermediate cooling rates from melt result in a dendritic microstructure. Primary and secondary dendrites can be seen in this image.
A simple gating system for a horizontal parting mold.
Different types of risers
Schematic of the low-pressure permanent mold casting process
A high-performance software for the simulation of casting processes provides opportunities for an interactive or automated evaluation of results (here, for example, of mold filling and solidification, porosity and flow characteristics). Picture: Componenta B.V., The Netherlands)

Common metals that are cast include cast iron, aluminium, magnesium, and copper alloys.

Engine block

Structure which contains the cylinders, and other parts, of an internal combustion engine.

Block of a modern V6 diesel engine. The large holes are the cylinders, the small round orifices are mounting holes and the small oval orifices are coolant or oil ducts.
De Dion-Bouton engine, circa 1905. The cylinder heads are integrated into the engine block, but the crankcase is separate. The bottom half of the crankcase also includes the oil sump.
Typical 1930-1960 flathead engine with integrated crankcase (the cylinder head is tipped upwards for illustrative purposes)

Engine blocks are normally cast from either a cast iron or an aluminium alloy.

Malleable iron

Polycrystalline structure of malleable iron at 100x magnification

Malleable iron is cast as white iron, the structure being a metastable carbide in a pearlitic matrix.

Blast furnace

Type of metallurgical furnace used for smelting to produce industrial metals, generally pig iron, but also others such as lead or copper.

Former blast furnace in Port of Sagunt, Valencia, Spain.
Blast furnaces of Třinec Iron and Steel Works, Czech Republic
Charcoal burning iron blast furnace in Ohio, 1923
Rising carbon monoxide reduces iron oxides to pure iron through a series of reactions that occur at different areas within a blast furnace.
An illustration of furnace bellows operated by waterwheels, from the Nong Shu, by Wang Zhen, 1313, during the Yuan Dynasty of China
Chinese fining and blast furnace, Tiangong Kaiwu, 1637.
The first blast furnace in Germany, as depicted in a miniature in the Deutsches Museum
Period drawing of an 18th-century blast furnace
Early modern blast furnace pictured in the former coat of arms of Lohtaja
The original blast furnaces at Blists Hill, Madeley, England
Charging the experimental blast furnace, Fixed Nitrogen Research Laboratory, Washington D.C., 1930
Tuyeres of Blast Furnace at Gerdau, Brazil
Abandoned blast furnace in Sestao, Spain. The furnace itself is inside the central girderwork.
Part of the gas cleaning system of a blast furnace in Monclova, Mexico. This one is about to be de-commissioned and replaced.

Some pig iron is used to make cast iron.

Propulsion transmission

Mode of transmitting and controlling propulsion power of a machine.

Single stage gear reducer
Interior view of Pantigo Windmill, looking up into cap from floor—cap rack, brake wheel, brake, and wallower. Pantigo Windmill is located on James Lane, East Hampton, Suffolk County, Long Island, New York.
The main gearbox and rotor of a Bristol Sycamore helicopter
Gears from a five-speed + reverse gearbox from the 1600 Volkswagen Golf (2009).
Tractor transmission with 16 forward and 8 backward gears
Amphicar gearbox cutaway w/optional shift for water going propellers
A diagram comparing the power and torque bands of a "torquey" engine versus a "peaky" one
16-speed (2x4x2) ZF 16S181 — opened transmission housing (2x4x2)
16S181 — opened planetary range housing (2x4x2)
Epicyclic gearing or planetary gearing as used in an automatic transmission.
Operation of a typical 4-speed sequential manual transmission; commonly used used in motorcycles and race cars.
Shimano XT rear derailleur on a mountain bike

Many transmissions and gears used in automotive and truck applications are contained in a cast iron case, though more frequently aluminium is used for lower weight especially in cars.