Chemical Composition of AISI and UNS Martensitic and Precipitation Hardening Stainless Steel

Chemical Composition of Martensitic Precipitation Hardening

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 420, 440 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. 420 being UNS S42000, 630 or 17/4PH being UNS S17400

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 SUS e.g. SUS 630. The Japanese have developed variants on some grades for certain product forms e.g. SUS 304J1 for sheet products.

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.

Martensitic

precipitation hardening

Designation			Chemical composition % by mass max unless stated
UNS No	SAE No	AISI No / Common Name	C	Si	Mn	P	S	Cr	Mo	Ni	Others
S13800	-	XM-13 PH13-8Mo	0.05	0.10	0.20	0.010	0.008	12.25 /13.25	2.00 /2.50	7.50 /8.50	N 0.01; Al 0.90/1.35
S15500	-	XM-12 15-5PH	0.07	1.00	1.00	0.040	0.030	14.0 /15.5	-	3.50 /5.50	Cu 2.5/4.5; Nb+Ta 0.15/0.45
S15700	-	632 15-7PH	0.09	1.00	1.00	0.040	0.030	14.00 /16.00	2.00 /3.00	6.50 /7.75	Al 0.75/1.50
S17400	-	630 17-4PH	0.07	1.00	1.00	0.040	0.030	15.00 /17.50	-	3.00 /5.00	Cu 3.00/5.00; Nb+Ta 0.15/0.45
S17600	-	635	0.08	1.00	1.00	0.040	0.030	16.00 /17.50	-	6.00 /7.50	Al 0.40; Ti 0.40/1.20
S17700	-	631 17-7PH	0.09	1.00	1.00	0.040	0.030	16.00 /18.00	-	6.50 /7.75	Al 0.75/1.50
S35000	-	633	0.07 /0.11	0.50	0.50 /1.25	0.040	0.030	16.00 /17.00	2.50 /3.25	4.00 /5.00	N 0.07/0.13
S35500	-	634	0.10 /0.15	0.50	0.50 /1.25	0.040	0.030	15.00 /16.00	2.50 /3.25	4.00 /5.00	N 0.07/0.13
S41000	51410	410	0.08 /0.15	1.00	1.00	0.040	0.030	11.5 /13.5	-	0.75	-
S41040	-	XM-30	0.18	1.00	1.00	0.040	0.030	11.0 /13.0	-	-	Nb 0.05/0.30
S41400	51414	414	0.15	1.00	1.00	0.040	0.030	11.5 /13.5	-	1.25 /2.50	-
S41500	-	F6NM	0.05	0.60	0.50 /1.00	0.030	0.030	11.5 /14.0	0.50 /1.00	3.5 /5.5	-
S41600	51416	416	0.15	1.00	1.25	0.060	0.15 min	12.0 /14.0	-	-	-
S41610	-	XM-6 (416 Plus X)	0.15	1.00	1.50 /2.50	0.06	0.15 min	12.0 /14.0	-	-	-
S41623	51416 Se	416Se	0.15	1.00	1.25	0.060	0.060	12.0 /14.0	-	-	Se 0.15 min
S42000	51420	420	0.15 min	1.00	1.00	0.040	0.030	12.0 /14.0	-	-	-
S42010	-	Trim Rite	0.15 /0.30	1.00	1.00	0.040	0.030	13.5 /15.00	0.40 /0.85	0.35 /0.85	-
S42020	51420F	420F	0.30 /0.40	1.00	1.25	0.060	0.15 min	12.0 /14.0	-	0.50	Cu 0.60
S42023	51420 FSe	420FSe	0.20 /0.40	1.00	1.25	0.060	0.060	12.0 /14.0	-	-	Se 0.15 min Cu 0.60
S42900	51429	429	0.12	1.00	1.00	0.040	0.030	14.0 /16.0	-	-	-
S43100	51431	431	0.20	1.00	1.00	0.040	0.030	15.0 /17.0	-	1.25 /2.50	-
S44002	51440A	440A	0.60 /0.75	1.00	1.00	0.040	0.030	16.0 /18.0	0.75	-	-
S44003	51440B	440B	0.75 /0.95	1.00	1.00	0.040	0.030	16.0 /18.0	0,75	-	-
S44004	51440C	440C	0.95 /1.20	1.00	1.00	0.040	0.030	16.0 /18.0	0.75	-	-
S44020	51440F	440F	0.95 /1.20	1.00	1.25	0.060	0.15 min	16.0 /18.0	0.75	0.50	Cu 0.60
S44023	51440 FSe	440FSe	0.95 /1.20	1.00	1.25	0.060	0.060	16.0 /18.0	-	-	Se 0.15 min Cu 0.60
S45000	-	XM-25 Custom 450	0.05	1.00	1.00	0.030	0.030	14.00 /16.00	0.50 /1.00	5.00 /7.00	Cu 1.25/1.75; Nb 8xC min
S45500	-	XM-16 Custom 455	0.05	0.50	0.50	0.040	0.030	11.00 /12.50	0.50	7.50 /9.50	Cu 1.50/2.50; Nb 0.10/0.50 Ti 0.90/1.40
S45503	-	-	0.010	0.20	0.50	0.010	0.010	11.00 /12.50	0.50	7.50 /9.50	Cu 1.50/2.50; Ti 1.00/1.35 Nb 0.10/0.50
S46500	-	-	0.02	0.25	0.25	0.015	0.010	11.00 /12.50	0.75 /1.25	10.75 /11.25	Ti 1.50/1.80 N 0.01
S66286	-	A286	0.08	1.00	2.00	0.040	0.030	13.50 /16.00	1.00 /1.50	24.0 /27.0	Al 0.35; B 0.0010/0.010; Ti 1.90/2.35; V 0.10/0.50 W 1.90/2.35