Ashford Instrumentation Ltd - Unified Numbering System (UNS)

Unified Numbering System (UNS)

The UNS number (short for "Unified Numbering System for Metals and Alloys") is a systematic scheme in which each metal is designated by a letter followed by five numbers. This alloy designation system is widely accepted in North America It is a composition-based system of commercial materials and does not guarantee any performance specifications or exact composition with impurity limits. Other nomenclature systems have been incorporated into the UNS numbering system to minimize confusion.

Overview of the UNS system

This is an overview of the UNS system, with special emphasis on common commercial alloys. As with any system, there are ambiguities such as the distinction between a nickel-based superalloy and a high-nickel stainless steel.


UNS series	Metal type(s)
A00001 to A99999	Aluminum and aluminum alloys
C00001 to C99999	Copper and copper alloys
D00001 to D99999	Specified mechanical property steels
E00001 to E99999	Rare earth and rare earthlike metals and alloys
F00001 to F99999	Cast irons
G00001 to G99999	AISI and SAE carbon and alloy steels (except tool steels)
H00001 to H99999	AISI and SAE H-steels
J00001 to J99999	Cast steels (except tool steels)
K00001 to K99999	Miscellaneous steels and ferrous alloys
L00001 to L99999	Low-melting metals and alloys
M00001 to M99999	Miscellaneous nonferrous metals and alloys
N00001 to N99999	Nickel and nickel alloys
P00001 to P99999	Precious metals and alloys
R00001 to R99999	Reactive and refractory metals and alloys
S00001 to S99999	Heat and corrosion resistant (stainless) steels
T00001 to T99999	Tool steels, wrought and cast
W00001 to W99999	Welding filler metals
Z00001 to Z99999	Zinc and zinc alloys