An ingot is a material, usually metal
A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...

, that is cast
In metalworking, casting involves pouring liquid metal into a mold, which contains a hollow cavity of the desired shape, and then allowing it to cool and solidify. The solidified part is also known as a casting, which is ejected or broken out of the mold to complete the process...

 into a shape suitable for further processing. Non-metallic and semiconductor materials prepared in bulk form may also be referred to as ingots, particularly when cast by mold based methods.


Ingots require a second procedure of shaping, such as cold/hot working, cutting or milling to produce a useful final product. Additionally ingots (of less common materials) can be used as currency, or as a currency reserve as with gold bar
Gold bar
A gold bar is a quantity of refined metallic gold of any shape that is made by a bar producer meeting standard conditions of manufacture, labeling, and record keeping....



Metal, either pure or alloy, heated past its melting point
Melting point
The melting point of a solid is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends on pressure and is usually specified at standard atmospheric pressure...

 and cast into a bar or block using a mold chill method. Polycrystalline and single crystal ingots are made from semiconductor materials by pulling from a molten melt. Uses include the formation of photovoltaic cells from silicon ingots by cutting the ingot into flats, known as wafers.

Single crystal

Single crystal
Single crystal
A single crystal or monocrystalline solid is a material in which the crystal lattice of the entire sample is continuous and unbroken to the edges of the sample, with no grain boundaries...

 ingots (called boules
Boule (crystal)
A boule is a single-crystal ingot produced by synthetic means. A boule of silicon is the starting material for most of the integrated circuits used today....

) of materials are grown (crystal growth) using methods such as the Czochralski process
Czochralski process
The Czochralski process is a method of crystal growth used to obtain single crystals of semiconductors , metals , salts, and synthetic gemstones...

 or Bridgeman technique
Bridgeman technique
The Bridgman–Stockbarger technique is named after Harvard physicist Percy Williams Bridgman and MIT physicist Donald C. Stockbarger...


The boules may be either semiconductors—for the electronic industry, or non-conducting inorganic compounds for industrial and jewelry use, e.g., synthetic ruby, sapphire etc.

Single crystal ingots of metal are produced in similar fashion to that used to produce high purity semiconductor ingots, i.e. by vacuum induction refining. Single crystal ingots of engineering metals are of interest due to their very high strength due to lack of grain boundaries
Grain boundary
A grain boundary is the interface between two grains, or crystallites, in a polycrystalline material. Grain boundaries are defects in the crystal structure, and tend to decrease the electrical and thermal conductivity of the material...

. The method of production is via single crystal dendrite
Dendrite (crystal)
A crystal dendrite is a crystal that develops with a typical multi-branching tree-like form. Dendritic crystal growth is very common and illustrated by snowflake formation and frost patterns on a window. Dendritic crystallization forms a natural fractal pattern...

 and not via simple casting. Possible uses include turbine blade
Turbine blade
A turbine blade is the individual component which makes up the turbine section of a gas turbine. The blades are responsible for extracting energy from the high temperature, high pressure gas produced by the combustor. The turbine blades are often the limiting component of gas turbines...


Copper alloys

In the United States, the brass and bronze ingot making industry started in the early 19th century. The US brass industry grew to be the number one producer by the 1850s. During colonial times the brass and bronze industrial was almost non-existent because the British
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 demanded all copper ore be sent to Britain for processing. Copper based alloy ingots weighed approximately 20 lbs.


Ingots are manufactured by the freezing of a molten liquid (known as the melt) in a mold. The manufacture of ingots has several aims. Firstly, the mold is designed to completely solidify and form an appropriate grain structure required for later processing, as the structure formed by the freezing melt controls the physical properties of the material. Secondly, the shape and size of the mold is designed to allow for ease of ingot handling and downstream processing. Finally the mold is designed to minimize melt wastage and aid ejection of the ingot, as losing either melt or ingot increases manufacturing costs of finished products.

A variety of designs exist for the mold, which may be selected to suit the physical properties of the liquid melt and the solidification process. Molds may exist in top, horizontal or bottom-up pouring and may be fluted or flat walled. The fluted design increases heat transfer owing to a larger contact area. Molds may be either solid "massive" design, sand cast (e.g. for pig iron) or water-cooled shells, depending upon heat transfer requirements. Ingot molds are tapered to prevent the formation of cracks due to uneven cooling. Crack or void formation occurs as the liquid to solid transition has an associated volume change for a constant mass of material. Formation of these ingot defects may render the cast ingot useless, and may need to be re-melted, recycled or discarded.

The physical structure of a crystalline material is largely determined by the method of cooling and precipitation of the molten metal. During the pouring process, metal in contact with the ingot walls rapidly cools and forms either a columnar structure, or possibly a "chill zone" of equiaxed dendrites
Dendrite (metal)
A dendrite in metallurgy is a characteristic tree-like structure of crystals growing as molten metal freezes, the shape produced by faster growth along energetically favourable crystallographic directions. This dendritic growth has large consequences in regards to material properties.Dendrites form...

, depending upon the liquid being cooled and the cooling rate of the mold.

For a top-poured ingot, as the liquid cools within the mold, differential volume effects cause the top of the liquid to recede leaving a curved surface at the mold top which may eventually be required to be machined from the ingot. The mold cooling effect creates an advancing solidification front, which has several associated zones, closer to the wall there is a solid zone which draws heat from the solidifying melt, for alloys there may exist a "mushy" zone, which is the result of solid-liquid equilibrium regions in the alloy's phase diagram
Phase diagram
A phase diagram in physical chemistry, engineering, mineralogy, and materials science is a type of chart used to show conditions at which thermodynamically distinct phases can occur at equilibrium...

, and a liquid region. The rate of front advancement controls the time that dendrites or nuclei have to form in the solidification region. The width of the mushy zone in an alloy may be controlled by tuning the heat transfer properties of the mold, or adjusting the liquid melt alloy compositions.

Continuous casting methods for ingot processing also exist, whereby a stationary front of solidification is formed by the continual take-off of cooled solid material, and the addition of molten liquid to the to casting process.

Approximately 70 percent of aluminium ingots in the U.S. are cast using the direct chill casting process, which reduces cracking. A total of 5 percent of ingots must be scrapped because of stress induced cracks
A fracture is the separation of an object or material into two, or more, pieces under the action of stress.The word fracture is often applied to bones of living creatures , or to crystals or crystalline materials, such as gemstones or metal...

 and butt deformation.

Cultural references

  • The Chinese New Year
    Chinese New Year
    Chinese New Year – often called Chinese Lunar New Year although it actually is lunisolar – is the most important of the traditional Chinese holidays. It is an all East and South-East-Asia celebration...

     food Jiaozi
    Jiǎozi 餃子 or 饺子 , bánh bột luộc , gyōza , Mo:Mo: or Momocha म:म: or ममचा , or pot sticker is a Chinese dumpling widely spread to Japan, Eastern and Western Asia.Jiaozi typically consist of a ground meat and/or vegetable filling wrapped into...

     was made to symbolize the ingot.
  • The eighth letter in the Ogham
    Ogham is an Early Medieval alphabet used primarily to write the Old Irish language, and occasionally the Brythonic language. Ogham is sometimes called the "Celtic Tree Alphabet", based on a High Medieval Bríatharogam tradition ascribing names of trees to the individual letters.There are roughly...

     alphabet is Tinne
    Tinne is the Irish name of the eighth letter of the Ogham alphabet, , meaning "ingot". Its phonetic value is [t]....

     meaning "ingot".

See also

  • Billet (manufacturing)
    Billet (manufacturing)
    Semi-finished casting products are intermediate castings produced in a foundry that need further processing before being a finished good. There are four types: ingots, billets, blooms, and slabs.-Ingot:...

    —typically refers to a large ingot of less precious metal - both are forms of Bar stock
    Bar stock
    Bar stock, also colloquially known as billet, is a common form of raw purified metal, used by industry to manufacture metal parts and products....

  • Tin ingot
    Tin ingot
    Tin ingots were a trading currency unique to Malacca. Cast in the shape of a peck, or dou in Chinese, each block weighs just over...

  • Wafer etching
  • Oxhide ingot
  • Gold bar
    Gold bar
    A gold bar is a quantity of refined metallic gold of any shape that is made by a bar producer meeting standard conditions of manufacture, labeling, and record keeping....

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