Bronze
Bronze is the generic name of copper alloys and tin. The term bronze is also "the bronze, but rather is used in poetry and literary texts, as well as campanology , where it designates the alloy used for casting bells.
The bronzes are normally composed of more than 60% copper and varying amounts of tin, and they also contain varying proportions of aluminum , lead , beryllium , manganese and tungsten , incidentally silicon and phosphorus , but no zinc in significant amounts (not to be confused with the brass , including the term brass is often translated as bronze).
Their main features are a good resistance to wear , moderate resistance to corrosion and good electrical conductivity. They are often used as friction material in front of the steel. Corrosion of bronze coins is an obstacle to their use in the Navy and the shipbuilding industry.
These alloys were first used during the Bronze Age to make tools , weapons, musical instruments and armor more robust and resilient than their predecessors in copper or stone. During the Bronze Age, the arsenic was often added to bronze (mostly as an impurity), which increased in hardness.
Alloys
With few exceptions, the bronzes contain between 3 and 20% tin.
The alloys of this family that contain mainly copper and tin. There are two types based on the phases:
- bronzes containing only the alpha phase () up to about 16% tin
- bronzes containing alpha phase () and delta ().
The alloys most commonly used in industry are CuSn5 (UE5P) CuSn7Pb6Zn4 (UE7) CuSn8 (UE9P) and CuSn12 (EU12). The number following the designation indicates the percentage of secondary metal in the alloy (Ex: CuSn5: 5% tin and therefore 95% copper).
Generally, the hardness of bronze increases in proportion to their tin content.
The alpha alloys are alloys for wrought. The mechanical properties increase with the deformation ratio and with the tin content. The second are casting alloys.
The bronze used for making bells contain between 20 and 25% tin. Delta is the phase that gives the sound. This stage is hard.
The bronzes in mirror are comprised of 30 to 35% tin. The tin surface oxidizes more easily, while copper alloy or in the presence of impurities commonly oxidized to form the verdigris. Here we find the principle of tinning.
The bronzes with alloying elements
In some alloys are added, the phosphorus of zinc , of lead.
The phosphorus can increase the mechanical properties. Zinc increases the flowability and the malleability of the alloy. Lead (up to 6%) provides better machinability. The bronze used for parts of friction can contain up to 30% lead. Finally, the beryllium provides exceptional hardness to bronze, which approximates the hardness of steel, while retaining all the qualities of specific friction bronze.
See also
- Bronze Age
- Bronze Art
- Material
- Bronze , River Upper Savoy , a tributary of the Arve.
- Regulates
- Iron law of oligarchy
- Bronze Medal
- Brazen sea
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