Definición

• Brass. An alloy with the major component of copper, plus moderate zinc or tin content, which is highly ductile and has a yellow hue. Zinc is most often used as the alloy, from 10- 40% (if less than 10% it is bronze). Zinc is used for its lower cost over tin, and is sometimes alloyed with other metals for a wide range of properties. Excellent for striking � somewhat softer than bronze but stronger than copper alone � brass is widely used for coins, tokens and nonart medals. It is an excellent base metal that can be electroplated with ease (such an item would bleed yellow should the plated metal wear thin). Brass, often used in bimetallic items for its contrasting color, does not acquire a patina like bronze. It can, however, be polished and lacquered for its sustained yellow color.
   
  Despite the great amount of brass in commercial use in the last 200 years, making brass alloy is very difficult. The zinc is added to molten copper, but the difficulty is that the temperature required to melt copper (1083� C, 1981� F) vaporizes zinc. Zinc melts at 419� C and vaporizes at 917� C). The zinc has to be fed into molten copper at a very precise time in the formulation of any brass alloy.
   
  See bronze, composition (2), oroide.
   
  Ancient brass. An early series of coins of the Roman Empire, in sestertius and dupondius denominations, were made of brass, called orichalcum. These coins were termed �First Brass,� �Second Brass� and such for different stages of their development. In the orient, Chinese cash coins were cast in brass.
  CLASS 05.4
   
  0895-(005)01 Illus: Full Color Page
   

Fuente

• D. Wayne Johnson Encyclopedia of Coin and Medal Technology

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