The SAE steel grade system's correspondence to other alloy numbering systems, such as the ASTM-SAE unified numbering system (UNS), can be seen in cross-referencing tables (including the ones given below). The alloy number is simply a general classifier, whereas it is the specification itself that narrows down the steel to a very specific standard. For example, in the alloy/grade field, a certificate might refer to '4140', 'AISI 4140', or 'SAE 4140', and in most light-industrial applications any of the above is accepted as adequate, and considered equivalent, for the job at hand, as long as the specific specification called out by the designer (for example, '4140 bar per ASTM-A108' or '4140 bar per AMS 6349') is certified to on the certificate. Today steel quotes and certifications commonly make reference to both SAE and AISI, not always with precise differentiation. In 1995 the AISI turned over future maintenance of the system to SAE because the AISI never wrote any of the specifications. For several decades the systems were united into a joint system designated the AISI/SAE steel grades. These efforts were similar and overlapped significantly. In the 1930s and 1940s, the American Iron and Steel Institute (AISI) and SAE were both involved in efforts to standardize such a numbering system for steels. The SAE steel grades system is a standard alloy numbering system (SAE J1086 - Numbering Metals and Alloys) for steel grades maintained by SAE International. Standard alloy numbering system for steel grades Steels

18 8 stainless steel composition