The Unified Numbering System (UNS)
What is The Unified Numbering System
The Unified Numbering System (UNS) is a standardized numbering system used to identify and classify various materials and alloys in industrial applications. It provides a unique alphanumeric code for each material, facilitating efficient material identification, selection, and specification.
The UNS encompasses a wide range of materials, including metals, plastics, ceramics, and more. By utilizing a consistent numbering system, the UNS simplifies communication, promotes international trade, and supports standardization across different industries.
History and Development of the UNS
The history and development of the Unified Numbering System (UNS) can be traced back to the early 20th century. Prior to the existence of the UNS, there were multiple proprietary numbering systems used by different industries to identify materials. This lack of standardization posed challenges in material identification, comparison, and communication.
To address this problem, efforts were initiated by different organizations, including the American Society for Testing and Materials (ASTM), the Society of Automotive Engineers (SAE), and the American Iron and Steel Institute (AISI), to develop a unified system that would would facilitate seamless communication, improve efficiency, and support standardization across industries.
In January 1971, a comprehensive 18-month study concluded that the implementation of a unified numbering system would be both feasible and beneficial. As a result, an advisory board was formed by the ASTM and SAE in April 1972 with the purpose of establishing the Unified Numbering System (UNS).
Structure of The UNS
The UNS system is a composition-based material numbering system. It assigns a unique alphanumeric code to each metal or alloy, consisting of a prefex letter followed by five digits. The letter in the UNS number indicates the base metal, while the remaining five digits designate the specific chemical composition of other elements in the alloy.
Examples of UNS numbers:
- S31000 - Stainless steel with 25% chromium and 20% nickel
- C11000 - Copper with 99.9% copper
- G11400 - Carbon Steel with 0.4% carbon
The UNS system incorporates other existing nomenclature systems. As an example, aluminum alloy 6061, which is commonly designated as AA6061, is converted to UNS A96061 within the UNS system. This conversion allows for seamless cross-referencing and identification across various material designation systems.
| UNS series | Metal |
|---|---|
| A00001 to A99999 | Aluminum and aluminum alloys |
| C00001 to C99999 | Copper and copper alloys (brasses and bronzes) |
| 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 | 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 |
A UNS number alone does not constitute a full material specification because it establishes no requirements for material properties, heat treatment, form, or quality.
Conclusion
The Unified Numbering System is a valuable tool for identifying and tracking metals and alloys. It provides a consistent and unambiguous way to identify materials, which can help to ensure that the correct material is used for a particular application. UNS numbers can also be used to cross-reference different materials specifications and track materials throughout the manufacturing process.