|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
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.
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.
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).