Brass Composition

[patholahan]

I understand that there are a range of brasses, but is there any criteria that determines an amount of zinc that must be present for the copper alloy to be considered "brass"?

 

[arunmrao]

Please take a look at Cu-Zn phase diagram to understand the solubility limits of Zn in Cu and the phase structure.



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[EdStainless]

and you will see why all of the alloys called brass fall into the 15%-38% Zn range.
The low end is rather arbitrary. Cu-Zn alloys with less than 15% Zn are usually called bronze.
The upper end is a phase structure limit. There are alloys with more Zn, but they are not considered brasses.

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[vipereyes]

Hi!

The ASTM B19 specification for Brass states that the composition is 68.5% - 71.5% copper, up to .07% lead, up to .05% iron and the remainder is zinc.

Hope this helps.

Kim

 

[JamesCKelly]

It might help if we knew why you are asking this question.
The most common brass is nominal 70% copper 30% zinc. It is also known as "cartridge brass".
This brass is subject to dezincification if left for long times in water. The Zn disappears, and the metal has a dull copper color, as copper is all that is left on the surface. You can see this in old plumbing fixtures, which used to be made of metal rather than plastic.
Brass with less than 15% zinc is supposed not to dezincify in water.
Copper with 5 or 6% zinc is called "gilding metal", and I believe was the chemistry of the US one cent coin prior to about 1980.
Just about anything that looks like brass will also stress corrode crack in ammonia, or nitrogen compounds that come from human or animal waste.