Most ASTM and ASME standards list the steel grades by their UNS (Unified Numbering system) numbers but also make reference, where appropriate to the more general AISI (American Iron and Steel Institute) grade designations. These grade numbering systems are widely used in the USA, where they originated and are recognised by most stainless steel specifiers and users.

The American Iron and Steel Institute (AISI) developed designations such as 309310 etc and published compositions for these in their 'Steel Products Manual' (1974).

These are NOT specifications, but steel grade composition ranges only.

These grades were used by the American Society Testing and Materials (ASTM) to identify grades in a wide range of standards they published for stainless products, such as sheets and plates (ASTM A240), bars (ASTM A276) and tubes (ASTM A269).

The compositions of the AISI grades were made more specific with the introduction of the 'Unified Numbering System', jointly established by ASTM and SAE (Society of Automotive Engineers).

This five digit number, preceded by the letter 'S' for most stainless steel, identified the specific variant of the grade

e.g. 309 being UNS S30900, 304H being UNS S30409

American Society of Mechanical Engineers (ASME) publish design codes and standards for pressure applications. ASME standards are generally based on the appropriate ASTM standards, but the standard numbers are preceded with the letters 'SA', rather than just the 'A' of the ASTM standards.

Where UNS grade numbers are used, these are universal, regardless of the product type or the standard in which they appear.

The AISI designations have been adopted in Japan. The AISI number is preceded with the letters SUH for heat resisting grades e.g. SUH 310.

The composition ranges should always be checked in the appropriate standard.

The tables in this article use the UNS number as their key, but also show the related AISI and SAE numbers. Where appropriate, common names for the steels are also shown.

Heat resisting grades

DesignationChemical composition % by mass max unless stated
UNS NoSAE NoAISI No / Common NameCSiMnPSCrMoNiOthers
S21500-Esshete 12500.06/0.150.20/1.05.50/7.00.0450.03014.0/16.00.80/1.209.00/11.0B 0.003/0.009; Nb 0.75/1.25; V 0.15/0.40
S30415-153MA0.04/0.061.00/2.000.800.0450.03018.0/19.0-9.0/10.0N 0.12/0.18; Ce 0.03/0.08
S30451-304N0.080.752.000.0450.03018.0/20.0-8.0/10.5N 0.10/0.16
S30452-304HN (XM-21)0.080.752.000.0450.03018.0/20.0-8.0/10.5N 0.16/0.30
S30615-RA85H0.16/0.243.2/ 0.80/1.50
S30815-253MA0.05/0.101.40/2.000.800.0400.03020.0/22.0-10.0/12.0N 0.14/0.20; Ce 0.03/0.08
S30940-309Cb0.080.752.000.0450.03022.0/24.0-12.0/16.0Nb 10xC / 1.10
S30941-309HCb0.04/0.100.752.000.0450.03022.0/24.0-12.0/16.0Nb 10xC / 1.10
S31040-310Cb0.081.502.000.0450.03024.0/26.0-19.0/22.0Nb 10xC / 1.10
S31041-310HCb0.04/0.100.752.000.0450.03024.0/26.0-19.0/22.0Nb 10xC / 1.10
S31651-316N0.080.752.000.0450.03016.0/18.02.00/3.0010.0/14.0N 0.10/0.16
S32109-321H0.04/0.100.752.000.0450.03017.0/19.0-9.0/12.0Ti 4x(C+N) / 0.70
S33228--0.04/0.080.301.000.0200.01526.0/28.0-31.0/33.0Al 0.025;Ce 0.05/0.10; Nb 0.6/1.0
S33400-3340. 0.15/0.60; Ti 0.15/0.60
S34709-347H0.04/0.100.752.000.0450.03017.0/19.0-9.0/13.0Nb 8xC /1.00
S34800-3480.080.752.000.0450.03017.0/19.0-9.0/13.0Nb+Ta 10xC / 1.00; Ta 0.10; Co 0.20
S34809-348H0.04/0.100.752.000.0450.03017.0/19.0-9.0/13.0Nb+Ta 10xC /1.00; Ta 0.10; Co 0.20
S35045--0.06/ 0.15/0.60; Ti 0.15/0.60
S35315-353MA0.04/0.081.20/ 0.12/0.18; Ce 0.03/0.10
S41041--0.13/0.180.500.40/0.600.0300.03011.50/ 0.05; Nb 0.15
S41425--0.050.500.50/1.000.0200.00512.0/15.01.50/2.004.0/7.0N 0.06/0.12; Cu 0.30
S41800-Greek Ascoloy (615)0.15/0.200.500.500.0400.03012.00/14.000.501.80/2.20W 2.50/3.50
S42200-6160.20/0.250.500.50/1.000.0250.02511.0/12.50.90/1.250.50/1.00V 0.20/0.30; W 0.90/1.25
S42300-Lapelloy (619)0.27/0.320.500.95/1.350.0250.02511.00/12.002.50/3.000.50V 0.20/0.30
S44300-MT4430. 0.90/1.25
S44600514464460.201.001.500.0400.03023.0/27.0-0.75N 0.25
S64152-XM-320.08/0.150.350.50/0.900.0250.02511.00/12.501.50/2.002.00/3.00N 0.01/0.05; V 0.25/0.40
N08800-800 (332) 39.5 min; Al 0.15/0.60; Ti 0.15/0.60
N08810-800H0.05/ 0.75; Fe 39.5 min; Al 0.15/0.60; Ti 0.15/0.60
N08811--0.06/ 0.75; Fe 39.5 min; Al 0.15/0.60; Ti 0.15/0.60

Related References:
1. Chemical Composition of AISI and UNS Austenitic Stainless Steel
2. Chemical Composition of ACI Heat Resisting Stainless Steel
3. Chemical Composition of AISI and UNS Ferritic Stainless Steel
4. Chemical Composition of AISI and UNS Duplex Stainless Steel
5. Chemical Composition of AISI and UNS Heat Resisting Stainless Steel
6. Chemical Composition of AISI and UNS Martensitic and Precipitation Hardening