Development of the
UNIFIED NUMBERING SYSTEM
This article reviews the Unified Numbering System for Metals and Alloys—what it is, why it was conceived, and how it was developed.
Harold M. Cobb* Metallurgical Consultant Kennett Square, Pennsylvania
D
esignation systems for metals and alloys in the United States have traditionally been those established by various groups, including metal producers; trade associations such as the Aluminum Association (AA), the American Iron & Steel Institute (AISI), and the Copper Development Association (CDA); professional societies such as the American Society for Testing and Materials (ASTM), the American Welding Society (AWS), and the Society of Automotive Engineers (SAE); and the U. S. government. By the 1960s, it was becoming increasingly apparent that the traditional approach to the designation of metals left some problem areas that could not be satisfactorily solved. The following list of some of these problems should make it clear that a case could be made for developing an entirely new metals designation system: • Trade names: Many names: Many alloys were known only by trade names in cases where no central organization assigned numbers. However, the technical societies had policies prohibiting the use of trade names in their specifications. Therefore, it became the practice, for nickel alloys, to list the principal alloying elements as the designation. For example, a well-known nickel alloy was given the designation “Nickel-chromium-cobalt-m “Nickel-chromium-cobalt-molybdenum olybdenum alloy,” a designation which was not particularly meaningful to most readers. • Same number for different alloys: It alloys: It was not unusual for the various trade associations to assign the same number to different alloys. For example, Alloy 205 could be either a copper alloy, a nickel alloy, or a type of stainless steel. • Different numbers for the same alloy: The alloy: The AISI and SAE designated the same stainless steels by d i f -
Organization of UNS The UNS, jointly sponsored by the American Society for Testing and Materials (ASTM) and the Society of Automotive Engineers (SAE), is operated in accordance with ASTM E527/SAE J 1086, Recommended Practice for Numbering Metals and Alloys. The organization for administering the UNS consists of an advisory board, three number-assigning offices, a corps of volunteer consultants, and staffs at ASTM and SAE. Dr. James D. Redmond is the current chairman of the UNS Advisory Board. *Life member of ASM International
ferent numbers, three digits for AISI and five digits for SAE. • Discontinued numbers: The numbers: The AISI decided to discontinue the practice of designating numbers for steels, and this was a particular problem with regard to the assignment of designations to new stainless steels. ASTM was attempting to fill the gap by issuing a new series of numbers for proprietary stainless steels (e.g., XM-1, XM-2, XM-3, etc.) • Outmoded systems: CDA’s systems: CDA’s three-digit system for the numbering of copper alloys was outmoded, and a new system was being considered. • Variety of designations: The designations: The U.S. government often had metal metal designations that differed from those of other specification-writing bodies. A new numbering system Because of these problems, in 1967 the American Society for Testing and Materials (ASTM) and the Society of Automotive Engineers (SAE) began to explore the possibility of developing a new numbering system for metals that would address the difficulties described above and provide numbers for all alloys. The U.S. Army was especially interested in this subject, and in May 1969 the Army Materials and Mechanics Research Center (AMMRC) issued a contract to the SAE to conduct a “Feasibility Study of
Table 1— Primary series of UNS numbers UNS series
Metal group
UNS series
Metal group
Axxxxx Cxxxxx Dxxxxx Exxxxx Fxxxxx Gxxxxx Hxxxxx Jxxxxx Kxxxxx
Aluminum and aluminum alloys Copper and copper alloys Steels—designated by mechanical property Rare earth and rare earth-like alloys Cast irons AISI and SAE carbon and alloy steels AISI H-steels Cast steels Miscellaneous steels and ferrous alloys
Lxxxxx Mxxxxx Nxxxxx Pxxxxx Rxxxxx Sxxxxx Txxxxx Wxxxxx Zxxxxx
Low melting metals and alloys Miscellaneous nonferrous metals & alloys Nickel and nickel alloys Precious metal and alloys Reactive and refractory metals and alloys Stainless steels, valve steels, superalloys Tool steels Welding filler metals Zinc and zinc alloys
Table 2—Examples of UNS designations UNS
Traditional designation
A03190 A92024 C26200 G12144 G41300 K93600 L13700 N06007 N066 N0662 25
AA 319.0 (Aluminum alloy casting) AA 2024 (Wrought aluminum alloy) CDA 262 (Cartridge brass) AISI 12L14 (Leaded alloy steel) AISI 4130 (Alloy steel) Invar (36% nickel alloy steel) Alloy Sn 70 (Tin-lead solder) Nickel-chromium alloy (Hastelloy G) All Alloy 625 (Nickel-chromiu mium-mo -molybdenum-c m-columbi mbium alloy) Alloy 21 (Titanium alloy) AISI 304N (Stainless steel, high nitrogen) Ferralium 255 (Duplex stainless steel) AISI A-8 (Tool steel) AWS E307 (Stainless steel electrode) Alloy AG40A (Zinc alloy)
R58210 S30452 S32550 T30108 W30710 Z33520
a Unified Numbering System for Metals and Alloys.” This project was jointly sponsored by ASTM and SAE, and a committee was appointed to conduct the study. The committee was chaired by Norman L. Mochel, a past president of ASTM, and consisted of the following members: Herbert F. Campbell , Army Materials and Mechanics Research Center Harold M. Cobb , American Society for Testing and Materials Alvin G. Cook , Allegheny Ludlum Steel Corp. Henry B. Fernald , Technical Consultant Muir L. Frey , Engineering Consultant S. T. Main , Grumman Grumman Aircraft Corp. Norman L. Mochel,Engineering Mochel, Engineering Consultant R. Thomas Northrup , Society of Automotive Engineers Bruce A. Smith , General Motors Engineering Staff Harry H. Stout , Phelps Dodge Copper Products Corp. Development of the UNS Some individuals consulted during the course of
the eighteen-month feasibility study expressed grave doubts about the possibility of establishing an overall numbering system, but others thought it was worth exploring. The major trade associations concerned with metals numbering systems were also consulted, including the Aluminum Association, the American Iron & Steel Institute, the Copper Development Association, and the Steel Founders’ Society of America (SFSA). It was recognized at the outset that any new system could be successful only if these organizations were in general agreement with the concept. In January 1971, the study was completed and a report was submitted to the U.S. Army stating that it had been determined that a unified numbering systems for metals was feasible and desirable. The report included a general proposal of how such a system could be established to provide a coherent designation system for all current and future metals and alloys. In April 1972, ASTM and SAE established an Advisory Board to further develop and refine the proposed numbering system The Advisory Board consisted of the following members: Chairman: Bruce A. Smith , General Motors Engineering Staff Secretaries: Harold M. Cobb , ASTM Staff R. Thomas Northrup , SAE Staff Members: John Artman , Defense Industrial Supply Center Lawrence H. Bennett , National Bureau of Standards Alvin G. Cook , Allegheny Ludlum Steel Corp. Henry B. Fernald, Jr. Jr.,, Technical consultant John Gadbut , International Nickel Co. Joseph M. Engel , Republic Steel Corp. (representing AISI) W. Stuart Lyman , Copper Development Association Robert E. Lyons, Federal Supply Service Norman L. Mochel , Metallurgical Consultant Edward F. Parker , General Electric Co. Richard R. Senz , The Aluminum Co. of America
Tabel 3 — A typical entry from metals and alloys in the Unified Numbering System Nickel and Nickel Alloys Unified Number Description
Chemical Composition
Cross-reference Specifications
N1003 003
Al 0.50 0.50ma max x B0.0 B0.010 10ma max x C0.0 C0.044-0. 0.08 08 Co 0.20 0.20 max max Cr 6.0-8.0 Cu 0.35 max Fe 5.0 max Mn 1.00 max Mo 15.0-18.0 Ni rem P 0.15 max S 0.020 max Si 1.00 max V 0.50 max W 0.50 max
AMS AMS 5607 5607;; 577 5771 ASME SB434; SFA5.14 (ERNiMo-2) ASTM B366; B573 AWS A5.14 (E (ERNiMo-2)
Ni-M Ni-Mo o Allo Alloy. y. Solid solution strengthened (Hastelloy N)
(for the Aluminum Assoc.) Whitney Snyder , American Motors Corp. Rudolph Zillman , Steel Founders’ Society of America This Board decided that the official name of the new all-encompassing system would be the “Unified Numbering System for Metals (UNS).” The major guiding principles of the system would be as follows: • Each designation for a metal or alloy should pertain to a specific metal or alloy as determined by its it s unique chemical composition, or to its mechanical mechanical properties or physical characteristics characteristics when these are the primary defining criteria and the chemical composition is secondary or not significant. • For ease of recognition, the numbers assigned should incorporate numbers from existing numbering systems whenever possible. • The numbering system should be designed to accommodate accommodate current metals and alloys, and to anticipate the need to provide numbers for new alloys for the foreseeable future. • The system should be ideally suited for computer use and for the general indexing of metals and alloys. Description of the system In March 1974, the UNS Advisory Board completed the “SAE/ASTM Recommended Practice for Numbering Metals and Alloys.” This established eighteen series of designations, which consisted of a prefix letter and five digits, as shown in Table 1. Note that in most cases the letter is suggestive of the family of metals identified. The procedures for assigning numbers numbers to each of the 18 series of numbers were to be coordinated by the Advisory Board, but the specific details for each series would be developed by experts in each of those fields. Examples of some of these designations are shown in Table 2. By 1974, the Advisory Board had coordinated the establishment of specific UNS designations for over 1000 metals and alloys, including steel, stainless steel, tool steel, superalloys, aluminum, copper, cobalt, magnesium, and nickel. These designations were listed in the first edition of a UNS Handbook,which was published in 1975. Each entry in the book included the UNS designation, a brief description of the alloy, the chemical composition of the alloy, and a list of the national specifications in which the alloy appeared. A typical entry from the book is shown in Table 3. UNS achievements over 25 years The UNS designation system has been a highly successful venture from many standpoints. It has provided satisfactory solutions to the six problem areas discussed earlier in this article. Metals and Alloys in the Unified Numbering System, published jointl jointly y by by ASTM ASTM and SAE, SAE, lists lists over over 5000 5000 UNS desdesignations in the recently published ninth edition. It is also significant to note that this publication has been adopted by the Department of Defense (DoD) as a replacement for MIL-HDBK-H1, Cross Index
of Chemically Equivalent Specifications and IdenIdentification Code (Ferrous and Nonferrous Alloys). The Copper Development Association, in a sweeping change, replaced all of the traditional three-digit CDA numbers with UNS designations, and the American Welding Society now references UNS designations in all AWS specifications for welding filler metal and electrodes. A large per centage of ASTM specifications specifications include UNS refref erences and, for new stainless steel alloys and most nickel alloys, UNS is the only designation listed. Virtually all of the metals reference books published in the last 20 years have adopted UNS as their principal indexing system, and many metal producers now reference the UNS designations in their literature. n For more information: Dr. James D. Redmond, TMR Stainless, 3209 McKnight East Drive, Pittsburgh, PA 15327-6423; tel: 412/369-0377; fax: 412/367-2353; email
[email protected]
How useful did you find the information presented in this article? Very useful, Circle 270 Of general interest, Circle 271 Not useful, Circle 272
Virtually all of the metals reference books pub- lished in the last 20 years have adopted UNS as their principal indexing system.
