Question about Bronze
RKKay
Posts: 3,015 ✭✭✭
95% Cu, 5% Sn and Zn usually is considered bronze for purposes of coins. Is 90% Cu, 10% Sn also considered bronze? Is this a statistically significant difference to consider it a different metallic variety? Thanks in advance for your help.
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<< <i>Among the binary brasses, Commercial Bronze 22000 holds a favored position where product appearance is a factor of concern. Nominally composed of 90% copper and 10% zinc(Sn), this alloy not only possesses a rich and pleasing bronze color, but has practical properties such as excellent malleability, ductility, strength and hardness, surpassing that of C21000. It is also noted for its galling and corrosion resistance. >>
Rick,
To the metallurgist there are many difference bronzes, depending on the proportional mix of the various component metals.
The following is from one encyclopedic source on various alloys.
Bronze, in metallurgy
<< <i>In metallurgy, alloy of copper, tin, zinc, phosphorus, and sometimes small amounts of other elements. Bronzes are harder than brasses. Most are produced by melting the copper and adding the desired amounts of tin, zinc, and other substances. The properties of the alloy depend on the proportions of its components. Aluminum bronze has high strength and resists corrosion; it is used for bearings, valve seats, and machine parts. Leaded bronze, containing from 10% to 29% lead, is cast into heavy–duty bushings and bearings. Silicon bronze is used for telegraph wires and chemical containers. Phosphor bronze is used for springs. Bronze is used for coins, medals, steam fittings, and gunmetal and was formerly employed for cannon. Because of its particularly sonorous quality, bell metal, containing from 20% to 24% tin, is used for casting bells. Bronze has long been used in art, e.g., for castings, engravings, and forgings. >>
Cupro-Nickel Alloy
<< <i>Self-evidently an alloy of copper and nickel, it is one of the most common alloys used in modern coins. It is also called copper-nickel in the US by some. A related alloy called Alpaca also contains zinc.
It is silvery in appearance and hard wearing, and yet easy to fabricate. In the UK was first used in 1947 where an alloy of 75% Cu and 25% Ni is used for most 'silver' coins. With this composition the coin shows no trace of the colour of its main constituent.
Other copper-nickel alloys have been used. The early US cents from 1857 to 1864 contain 87.5% Cu and 12.5% Ni, and so have a light yellow colour, while the present-day 20p coin of the UK is made from an 84% Cu and 16% Ni alloy. Some modern cupro-nickel coins of Russia also contain zinc. The Franklin Mint in the USA have developed a cupro-nickel alloy they call Franklinium. Bactrian coins of King Euthydemus (220 BC) are known in a copper-nickel alloy. The origin of the nickel in these coins is uncertain. >>
Anyway, I believe the alloy you are mentioning would be brass, one of several different brasses. There are hundreds of differnt alloys and I don't have my book that lists most of them handy, but a Google search would probably locate a list.
<< <i>Researching another coin with the SEM-EDX testing? Err... whatever it's called... >>
GMan: Yep.
Pushkin: Thank you very much. That answered my question perfectly. Thanks.
Specializing in 1854 and 1855 large FE patterns
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<< <i>Nominally composed of 90% copper and 10% zinc(Sn), >>
Well that throughly confuses the subject. 10% zinc(Sn) But Sn is the chemical symbol for Tin not Zinc, so which do they mean?
Basicly alloys of copper and zinc are considered to be brass. Once Tin or other elements are added it is normally called a bronze. Or at least that has been my understanding. So yes, 90% copper and 10% Tin would be bronze.
Specializing in 1854 and 1855 large FE patterns
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<< <i>Well that throughly confuses the subject. 10% zinc(Sn) But Sn is the chemical symbol for Tin not Zinc, so which do they mean? >>
Good point!
Yes, I think there is a typo.
Here is a link to many of the various alloys.
Bronzes, brasses and others
Good luck.