UNS system

The unified numbering system UNS


Unified Numbering System (UNS) is a system that is used as an alloy designation system. Its main objective is to classify the material in a specific way. This system helps to avoid confusion due to the use of more than one identification number for the same type of metal or alloy.


This system provides ways to correlate several internationally used metal and alloy numbering systems. This arrangement classifies a streamlined material with a prefix letter and five digits specifying a material structure. It has a prefix with five digits, the prefix sign denoting different metals to give the class of metals,
For example, C denotes copper, brass, or bronze alloys, T indicates tool steels, and A denotes steel. The other five digits indicate the composition of the material. Before this system, the system of three digits used to run, in this system, the first three digits are to correspond to the same old system while the last two digits represent new variations. The system is a joint effort between ASTM and SAE, to produce unique identifiers for materials based on chemical composition. Thus we can say that the UNS identifies nine chains for ferrous metals and their alloys. The UNS system series for ferrous metals and their alloys are given bellow as an example:


UNS Series Metal
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

General category of materias are as follows:

A = aluminium and alloys

C = copper and alloys

D = steel with specified mechanical properties

F = iron alloys

G – AISI & SAE carbon steels

J – cast alloys

K – miscellaneous steels and alloys

N – nickel and nickel alloys

S – heat and corrosion resistant stainless steels

T – tool steels

W – weld filler metals

Z – zinc and zinc alloys
U-section wafer body

Some common materials and translations to other standards are as follows:

UNS K11547 is T2 tool steel
UNS S17400 is ASTM grade 630, Cr-Ni 17-4PH precipitation hardened stainless steel
UNS S30400 is SAE 304, Cr/Ni 18/10, Euronorm 1.4301 stainless steel
UNS S31600 is SAE 316
UNS S31603 is 316L, a low carbon version of 316. The digits “03” were assigned since the maximum allowed carbon content is 0.03%
UNS C90300 is CDA 903

UNS Systems Metals has a wide range of identity that provides support to products operating worldwide.

Today almost all metals and its alloys are classified by structure according to the Unified Numbering System (UNS). The system has been adapted by manufacturers and industries around the world.

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