Unified numbering system
The unified numbering system (UNS) is an alloy designation system widely accepted in North America. It consists of a prefix letter and five digits designating a material composition. For example, a prefix of S indicates stainless steel alloys, C indicates copper, brass, or bronze alloys, T indicates tool steels, and so on. The first 3 digits often match older 3-digit numbering systems, while the last 2 digits indicate more modern variations. For example, Stainless Steel Type 310 in the original 3-digit system became S31000 in the UNS System. The more modern low-carbon variation, Type 310S, became S31008 in the UNS System. Often, the suffix digit is chosen to represent a material property specification. For example, "08" was assigned to UNS S31008 because the maximum allowed carbon content is 0.08%. The UNS is managed jointly by the ASTM International and SAE International. A UNS number alone does not constitute a full material specification because it establishes no requirements for material properties, heat treatment, form, or quality.
Some common materials and translations to other standards:
- 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 Number Lookup, MatWeb Entering the UNS number shows a data sheet on the alloy.