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. A prefix of S indicates stainless steel alloys, C for copper, brass, or bronze alloys, T for steel/" target="_blank" class="keylink">tool steels, etc. The first three digits often match older three-digit numbering systems, while the last two digits indicate more modern variations. 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 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 steel/" target="_blank" class="keylink">tool steel
• UNS S17400 is ASTM grade 630, Cr-Ni 17-4PH precipitation hardening 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