Designations for Stainless Steels

In the United States, wrought grades of stainless steels are generally designated by the American Iron and Steel Institute (AISI) numbering system, the Unified Numbering System (UNS), or by the proprietary name of the alloy. In addition, designation systems have been established by most of the major industrial nations. Of the two institutional numbering systems used in the U.S., AISI is the oldest and most widely used. Most of the grades have a three-digit designation; the 200 and 300 series are generally austenitic stainless steels, whereas the 400 series are either ferritic or martensitic. Some of the grades have a one- or two-letter suffix that indicates a particular modification of the composition.

The UNS system is a broader-based system that comprises a list of all metallic materials, including stainless steel. This system includes a considerably greater number of stainless steels than AISI, because it incorporates all of the more recently developed stainless steels. The UNS designation for a stainless steel consists of the letter S, followed by a five-digit number. For those alloys that have an AISI designation, the first three digits of the UNS designation usually correspond to an AISI number. When the last two digits are 00, the number designates a basic AISI grade. Modifications of the basic grades use two digits other than zeroes.

Table 1 provides the compositional limits for select stainless steels, listed by UNS and AISI type designations and separated into the basic families described below. Where AISI type designations are not available, common trade names are listed. These names, the third commonly used identification of stainless steels, have often become the popular means of identifying a particular alloy.

Table 1 Composition of selected standard and special stainless steels

type

Composition, wt% max

C

Mn

Si

P

S

Cr

Ni

Mo

N

Others

Ferritic alloys

S40500

405

0.08

1.00

1.00

0.040

0.030

11.5014.50

0.10-0.30 Al

S40900

409

0.08

1.00

1.00

0.045

0.045

10.5011.75

0.50

6 x C-0.75 Ti

S43000

430

0.12

1.00

1.00

0.040

0.030

16.0018.00

S43020

430F

0.12

1.25

1.00

0.060

0.15(a)

16.0018.00

0.60

S43023

430FSe

0.12

1.25

1.00

0.060

0.060

16.0018.00

0.15 min Se

S43400

434

0.12

1.00

1.00

0.040

0.030

16.0018.00

0.751.25

S44200

442

0.20

1.00

1.00

0.040

0.030

18.0023.00

S44300

443(b)

0.20

1.00

1.00

0.040

0.030

18.0023.00

0.50

0.90-1.25 Cu

S44400

444(b)

0.025

1.00

1.00

0.040

0.030

17.5019.50

1.00

1.752.50

0.025

[0.20 + 4 (C + N)]-0.80 Ti + Nb

S44600

446(b)

0.20

1.50

1.00

0.040

0.030

23.0027.00

0.25

S18200

18-2FM(c)

0.08

1.252.50

1.00

0.040

0.15(a)

17.5019.50

1.502.50

Martensitic alloys

S40300

403

0.15

1.00

0.50

0.040

0.030

11.50-

type

Composition, wt% max

C

Mn

Si

P

S

Cr

Ni

Mo

N

Others

13.00

S41000

410

0.15

1.00

1.00

0.040

0.030

11.5013.00

S41400

414

0.15

1.00

1.00

0.040

0.030

11.5013.50

1.252.50

S41600

416

0.15

1.25

1.00

0.060

0.15(a)

12.0014.00

0.60

X(d)

0.15

1.502.50

1.00

0.060

0.15(a)

12.0014.00

0.60

S41623

416Se

0.15

1.25

1.00

0.060

0.060

12.0014.00

0.15 min Se

S42000

420

0.15(a)

1.00

1.00

0.040

0.030

12.0014.00

S42010

TrimRite(e)

0.150.30

1.00

1.00

0.040

0.030

13.5015.00

0.251.00

0.401.00

S42020

420F

0.15(a)

1.25

1.00

0.060

0.15(a)

12.0014.00

0.60

S42023

420FSe(b)

0.300.40

1.25

1.00

0.060

0.060

12.0014.00

0.60

0.15 min Se; 0.60 Zr or Cu

S43100

431

0.20

1.00

1.00

0.040

0.030

15.0017.00

1.252.50

S44002

440A

0.600.75

1.00

1.00

0.040

0.030

16.0018.00

0.75

S44003

440B

0.750.95

1.00

1.00

0.040

0.030

16.0018.00

0.75

S44004

440C

0.951.20

1.00

1.00

0.040

0.030

16.0018.00

0.75

S44020

440F(b)

0.951.20

1.25

1.00

0.040

0.100.35

16.0018.00

0.75

0.400.60

0.08

type

Composition, wt% max

C

Mn

Si

P

S

Cr

Ni

Mo

N

Others

S44023

440FSe(b)

0.951.20

1.25

1.00

0.040

0.030

16.0018.00

0.75

0.60

0.08

0.15 min Se

Austenitic alloys

S20100

201

0.15

5.507.50

1.00

0.060

0.030

16.0018.00

3.505.50

0.25

S20161

Gall-Tough(e)

0.15

4.006.00

3.004.00

0.040

0.040

15.0018.00

4.006.00

0.080.20

S20300

203EZ(f)

0.08

5.006.50

1.00

0.040

0.180.35

16.0018.00

5.006.50

0.50

1.75-2.25 Cu

S20910

22-13-5(c)

0.06

4.006.00

1.00

0.040

0.030

20.5023.50

11.5013.50

1.503.00

0.200.40

0.10-0.30 Nb; 0.100.30 V

S21000

SCF19(e)

0.10

4.007.00

0.60

0.030

0.030

18.0023.00

16.0020.00

4.006.00

0.15

2.00 Cu

S21300

15-15LC(e)

0.25

15.0018.00

1.00

0.050

0.050

16.0021.00

3.00

0.503.00

0.200.80

0.50-2.00 Cu

60(g)

0.10

7.009.00

3.504.50

0.040

0.030

16.0018.00

7.009.00

0.080.20

S21904

21-6-9LC(e)

0.04

8.0010.00

1.00

0.060

0.030

19.0021.50

5.507.50

0.150.40

S24100

18-2Mn(c)

0.15

11.0014.00

1.00

0.060

0.030

16.5019.50

0.502.50

0.200.45

Plus(e)

0.15

17.0019.00

1.00

0.045

0.030

17.0019.00

0.501.50

0.400.60

0.50-1.50 Cu

30(g)

0.10

7.009.00

1.00

15.0017.00

1.503.00

0.150.30

1.00 Cu

S30100

301

0.15

2.00

1.00

0.045

0.030

16.0018.00

6.008.00

S30200

302

0.15

2.00

1.00

0.045

0.030

17.00-

8.00-

type

Composition, wt% max

C

Mn

Si

P

S

Cr

Ni

Mo

N

Others

19.00

10.00

S30300

303

0.15

2.00

1.00

0.20

0.15(a)

17.0019.00

8.0010.00

0.60

X(d)

0.15

2.504.50

1.00

0.20

0.25(a)

17.0019.00

7.0010.00

0.75

S30323

303Se

0.15

2.00

1.00

0.20

0.060

17.0019.00

8.0010.00

0.15 min Se

S30330

303 Cu(b)

0.15

2.00

1.00

0.15

0.10(a)

17.0019.00

6.0010.00

2.50-4.00 Cu; 0.10 Se

S30400

304

0.08

2.00

1.00

0.045

0.030

18.0020.00

8.0010.50

S3043

304L

0.03

2.00

1.00

0.045

0.030

18.0020.00

8.0012.00

S30430

302 HQ(b)

0.10

2.00

1.00

0.045

0.030

17.0019.00

8.0010.00

3.00-4.00 Cu

FM(e)

0.06

2.00

1.00

0.040

0.14

16.0019.00

9.0011.00

1.30-2.40 Cu

S30452

304 HN(b)

0.08

2.00

1.00

0.045

0.030

18.0020.00

8.0010.50

0.160.30

S30500

305

0.12

2.00

1.00

0.045

0.030

17.0019.00

10.0013.00

S30900

309

0.20

2.00

1.00

0.045

0.030

22.0024.00

12.0015.00

S30908

309S

0.08

2.00

1.00

0.045

0.030

22.0024.00

12.0015.00

S31000

310

0.25

2.00

1.50

0.045

0.030

24.0026.00

19.0022.00

S31008

310S

0.08

2.00

1.50

0.045

0.030

24.0026.00

19.0022.00

type

Composition, wt% max

C

Mn

Si

P

S

Cr

Ni

Mo

N

Others

S31600

316

0.08

2.00

1.00

0.045

0.030

16.0018.00

10.0014.00

2.003.00

S31603

316L

0.030

2.00

1.00

0.045

0.030

16.0018.00

10.0014.00

2.003.00

S31620

316F

0.08

2.00

1.00

0.20

0.10(a)

17.0019.00

12.0014.00

1.752.50

S31700

317

0.08

2.00

1.00

0.045

0.30

18.0020.00

11.0015.00

3.004.00

S31703

317L

0.030

2.00

1.00

0.045

0.030

18.0020.00

11.0015.00

3.004.00

S32100

321

0.08

2.00

1.00

0.045

0.030

17.0019.00

9.0012.00

5 x C min Ti

S34700

347

0.08

2.00

1.00

0.045

0.030

17.0019.00

9.0013.00

10 x C min Nb

S34720

347F(b)

0.08

2.00

1.00

0.045

0.180.35

17.0019.00

9.0012.00

10 x C-1.10 Nb

S34723

347FSe(b)

0.08

2.00

1.00

0.110.17

0.030

17.0019.00

9.0012.00

10 x C-1.10 Nb; 0.15-0.35 Se

S38400

384

0.08

2.00

1.00

0.045

0.030

15.0017.00

17.0019.00

N08020

20Cb-3(e)

0.07

2.00

1.00

0.045

0.035

19.0021.00

32.0038.00

2.003.00

8 x C-1.00 Nb; 3.00-4.00 Cu

Duplex alloys

S31803

2205(c)

0.030

2.00

1.00

0.030

0.020

21.023.0

4.506.50

2.503.50

0.080.20

S32550

Alloy 255(c)

0.04

1.50

1.00

0.04

0.03

24.027.0

4.506.50

2.004.00

0.100.25

1.50-2.50 Cu

S32900

329

0.20

1.00

0.75

0.040

0.030

23.00-

2.50-

1.00-

type

Composition, wt% max

C

Mn

Si

P

S

Cr

Ni

Mo

N

Others

28.00

5.00

2.00

Plus(e)

0.03

2.00

0.60

0.035

0.010

26.029.0

3.505.20

1.002.50

0.150.35

Precipitation-hardenable alloys

Mo(g)

0.05

0.20

0.10

0.010

0.008

12.2513.25

7.508.50

2.002.50

0.01

0.90-1.35 Al

S15500

15-5PH(g)

0.07

1.00

1.00

0.040

0.030

14.0015.50

3.505.50

0.15-0.45 Nb; 2.504.50 Cu

S15700

15-7PH(g)

0.09

1.00

1.00

0.040

0.030

14.0016.00

6.507.25

2.003.00

0.75-1.50 Al

S17400

17-4PH(g)

0.07

1.00

1.00

0.040

0.030

15.5017.50

3.005.00

0.15-0.45 Nb; 3.005.00 Cu

S17700

PH 17-7(g)

0.09

1.00

1.00

0.040

0.040

16.0018.00

6.507.75

0.75-1.50 Al

S35000

633(b)

0.070.11

0.501.25

0.50

0.040

0.030

16.0017.00

4.005.00

2.503.25

0.070.13

S35500

634(b)

0.100.15

0.501.25

0.50

0.040

0.030

15.0016.00

4.005.00

2.503.25

0.070.13

450(e)

0.05

1.00

1.00

0.030

0.030

14.0016.00

5.007.00

0.501.00

8 x C min; 1.251.75 Cu

S45500

Custom 455(e)

0.05

0.50

0.50

0.040

0.030

11.0012.50

7.509.50

0.50

0.10-0.50 Nb; 1.502.50 Cu 0.80-1.40 Ti

S66286

A286(c)

0.08

2.00

1.00

0.040

0.030

13.5016.00

24.027.0

1.001.50

0.35 Al; 0.00100.010 B 1.90-2.35 Ti; 0.10-0.50 V

Note: All compositions include Fe as balance.

Note: All compositions include Fe as balance.

(a) Minimum, rather than maximum wt%.

(b) Designation resembles AISI type, but is not used in that system.

(c) Common trade name, rather than AISI type.

(d) Trade name of Crucible Inc.

(e) Trade name of Carpenter Technology Corporation.

(f) Trade name of Al-Tech Corp.

(g) Trade name of Armco Inc.

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