Smiths Metal Centres - Bronze Stockholder


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Bronze

Bronze is the oldest alloy known to man. It is an alloy of copper and tin but it is more often used with other alloying elements included. Bronze has found a wide variety of used over the years but other materials have replaced it in some instances. Bronze still, however, finds many uses in bearings, gears and electronic applications.

The basics
Strictly speaking, bronze is an alloy of copper and tin. However, bronze is also used to describe a wider range of copper based alloys. Generally, bronze alloys consist of about 12% tin, though some specialised products may contain much as 20%. Phosphor bronzes, which contain less than 8% tin, have an addition of phosphor to improve strength and hardness.

Superior attributes can often be attained through the addition of other elements to the basic bronze alloy. As well as phosphor, zinc and lead are the most common additions.

Bronze alloys
A leaded bronze will generally have better machining characteristics than an unleaded bronze. It will, however, retain a plasticity that makes it ideal for applications such as the production of bearings, as it allows slacker tolerances to be absorbed if softer shaft materials are used. This also prevents the overheating and seizure of like metals caused by friction.

Adding zinc to bronze alloys results in an alloy commonly known as “gunmetal”. This derives from the use of this product in early culverins etc., used because of its hardness and strength. It also has good resistance to corrosion and finds many applications in the marine industry. Added lead improves the machinability of this product.

Aluminium bronze, one of the newer additions to the alloy range, has become well established in the manufacturer of avionic equipment as well as use in naval and military applications.

Alloy specifications
During the late 1990s a new series of BS EN standards was brought in for all copper based alloys (i.e. bronze). The new series of standards brought with it a new system for describing products.

The system described products in two ways, one using symbols the other using numbers. The symbol system follows the ISO compositional system and a brass made up of a 63/37 ratio of copper and zinc is shown as CuZn37.

The numbering system is six-character alpha numeric system with two characters (the first of which will be ‘C’ for copper) followed by three numbers and a letter. Using this system PB1 has become CC481. with the second C denoting a cast product.

This catalogue displays the old and the new systems (including the symbol based new method).

Alloy selection

BSB23 (DTD197)	CC481 (PB1)	CW451 (PB102)
C932 (SAE660)	CC494 (LB4C)	NES833

Bronze

  overview
  grades/alloys
  flat bar
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  sheet & plate
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  strip in coil
  wire