The Unified Numbering
System (UNS) is the accepted alloy
designation system in North America for
wrought and cast copper and copper alloy
products. The three-digit system
developed by the U.S. copper and brass
industry was expanded to five digits
following the prefix letter C and made
part of the Unified Numbering System for
Metals and Alloys. UNS designations are
simply expansions of the former
designations. For example, Copper Alloy
No. 377 (forging brass) in the original
three-digit system became C37700 in the
UNS System. The UNS is managed jointly
by the American Society for Testing and
Materials and the Society of Automotive
Engineers. Because these old numbers are
embedded in the new UNS numbers, no
confusion need result. This designation
system is also used in Canada.
The designation system
is an orderly method of defining and
identifying coppers and copper alloys;
it is not a specification. It eliminates
the limitations and conflicts of alloy
designations previously used and at the
same time provides a workable method for
the identification marking of mill and
foundry products.
The designation system
is administered by the Copper
Development Association Inc. New
designations are assigned as new coppers
and copper alloys come into commercial
use, and designations are discontinued
when an alloy composition ceases to be
used commercially. Anyone may request
changes in the list. New designations
are assigned if a copper or copper alloy
meets three criteria:
- The complete chemical
composition is disclosed.
- The copper or copper alloy is in
commercial use or is proposed for
commercial use
- The composition does not fall
within the limits of any designated
composition already in the list.
In the designation
system, numbers from C10000 through
C79999 denote wrought alloys. Cast
alloys are numbered from C80000 through
C99999. Within these two categories, the
compositions are grouped into the
following families of coppers and copper
alloys:
Coppers-Metals which have a
designated minimum copper content of
99.3% or higher.
High Copper Alloys -For the
wrought products, these are alloys with
designated copper contents less than
99.3% but more than 96% which do not
fall into any other copper alloy group.
The cast high copper alloys have
designated copper contents in excess of
94%, to which silver may be added for
special properties.
Brasses-These alloys contain
zinc as the principal alloying element
with or without other designated
alloying elements such as iron,
aluminum, nickel and silicon. The
wrought alloys comprise three main
families of brasses: copper-zinc alloys;
copper-zinc-lead alloys (leaded
brasses); and copper-zinc-tin alloys
(tin brasses). The cast alloys comprise
four main families of brasses:
copper-tin-zinc alloys (red, semi-red
and yellow brasses); "manganese bronze"
alloys (high strength yellow brasses);
leaded "manganese bronze" alloys (leaded
high strength yellow brasses);
copper-zinc-silicon alloys (silicon
brasses and bronzes); and cast
copper-bismuth and
copper-bismuth-selenium alloys. Ingot
for re-melting for the manufacture of
castings may vary slightly from the
ranges shown.
Bronzes-Broadly speaking,
bronzes are copper alloys in which the
major alloying element is not zinc or
nickel. Originally "bronze" described
alloys with tin as the only or principal
alloying element. Today, the term is
generally used not by itself but with a
modifying adjective. For wrought alloys,
there are four main families of bronzes:
copper-tin-phosphorus alloys (phosphor
bronzes); copper-tin-lead-phosphorus
alloys (leaded phosphor bronzes);
copper-aluminum alloys (aluminum
bronzes); and copper-silicon alloys
(silicon bronzes).
The cast alloys have four main
families of bronzes: copper-tin alloys
(tin bronzes); copper-tin-lead alloys
(leaded and high leaded tin bronzes);
copper-tin-nickel alloys (nickel-tin
bronzes); and copper-aluminum alloys
(aluminum bronzes).
The family of alloys known as
"manganese bronzes," in which zinc is
the major alloying element, is included
in the brasses, above.
Copper-Nickels-These are
alloys with nickel as the principal
alloying element, with or without other
designated commonly as "nickel silvers,"
these are alloys which contain zinc and
nickel as the principal and secondary
alloying elements, with or without other
designated elements.
Leaded Coppers -These comprise
a series of cast alloys of copper with
20% or more lead, sometimes with a small
amount of silver, but without tin or
zinc.
Special Alloys -Alloys whose
chemical compositions do not fall into
any of the above categories are combined
in "special alloys."
Designations for the most widely used
coppers and copper alloys are shown in
bold-face type in the tables of
composition. For each of these, a
standard data sheet appears in either
Part 2 (wrought products) or Part 7
(cast products) of the CDA Standards
Handbook.
The use of these standard
designations by any member or non-member
of the Copper Development Association
Inc. is voluntary. These standard
designations do not preclude any member
or non-member from manufacturing or
supplying products which do not conform
to these standard designations.
The standard designation composition
limits do not preclude the possible
presence of other unnamed elements.
However, analysis shall regularly be
made only for the minor elements listed
in the table, plus either copper or zinc
or plus all major elements except one.
The major element that is not analyzed
shall be determined by difference
between the sum of those elements
analyzed and 100%. By agreement between
producer or supplier and consumer,
analysis may be required and limits
established for elements not cited.
Percentage content of elements shown as
"Remainder" (Rem.) is normally
calculated by difference.
