AISI steel grades

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Iron alloy phases
Austenite (γ-iron; hard) Bainite Martensite Cementite (iron carbide; Fe₃C) Ledeburite (ferrite - cementite eutectic, 4.3% carbon) Ferrite (α-iron; soft) Pearlite (88% ferrite, 12% cementite)
Types of Steel
Plain-carbon steel (up to 2.1% carbon) Stainless steel (alloy with chromium) HSLA steel (high strength low alloy) Tool steel (very hard; heat-treated)
Other Iron-based materials
Cast iron (>2.1% carbon) Wrought iron (almost no carbon) Ductile iron

The American Iron and Steel Institute standardizes numbered AISI steel grades, including the following:

1 Carbon Steel and Low Alloy Steel
2 Stainless steel
3 Other steels
4 References
5 See also

[edit] Carbon Steel and Low Alloy Steel

Carbon steels and low alloy steels are designated by a four digit number, where the first two digits indicate the alloying elements and the last two digits indicate the amount of carbon, in hundreths of a percent by weight.

**AISI Carbon and Alloy Steel Designations**^[1]
AISI Designation	Type of Steel
Carbon Steels
10xx	Plain Carbon (Mn 1.00% max)
11xx	Resulferized
12xx	Resulferized and Rephosphorized
15xx	Plain Carbon (Mn 1.00% to 1.65%)
Manganese Steels
13xx	Mn 1.75%
Nickel Steels
23xx	Ni 3.50%
25xx	Ni 5.00%
Nickel-Chromium Steels
31xx	Ni 1.25%, Cr 0.65% or 0.80%
32xx	Ni 1.25%, Cr 1.07%
33xx	Ni 3.50%, Cr 1.50% or 1.57%
34xx	Ni 3.00%, Cr 0.77%
Molybdenum Steels
40xx	Mo 0.20% or 0.25%
44xx	Mo 0.40% or 0.52%
Chromium-Molybdenum (Chromoly) Steels
41xx	Cr 0.50% or 0.80% or 0.95%, Mo 0.12% or 0.20% or 0.25% or 0.30%
Nickel-Chromium-Molybdenum Steels
43xx	Ni 1.82%, Cr 0.50% or 0.80%, Mo 0.25%
43BVxx	Ni 1.82%, Cr 0.50%, Mo 0.12% or 0.35%, V 0.03% min
47xx	Ni 1.05%, Cr 0.45%, Mo 0.20% or 0.35%
81xx	Ni 0.30%, Cr 0.40%, Mo 0.12%
86xx	Ni 0.55%, Cr 0.50%, Mo 0.20%
87xx	Ni 0.55%, Cr 0.50%, Mo 0.25%
88xx	Ni 0.55%, Cr 0.50%, Mo 0.35%
93xx	Ni 3.25%, Cr 1.20%, Mo 0.12%
94xx	Ni 0.45%, Cr 0.40%, Mo 0.12%
97xx	Ni 0.55%, Cr 0.20%, Mo 0.20%
98xx	Ni 1.00%, Cr 0.80%, Mo 0.25%
Nickel-Molybdenum Steels
46xx	Ni 0.85% or 1.82%, Mo 0.20% or 0.25%
48xx	Ni 3.50%, Mo 0.25%
Chromium Steels
50xx	Cr 0.27% or 0.40% or 0.50% or 0.65%
51xx	Cr 0.80% or 0.87% or 0.92% or 1.00% or 1.05%
50xxx	Cr 0.50%, C 1.00% min
51xxx	Cr 1.02%, C 1.00% min
52xxx	Cr 1.45%, C 1.00% min
Chromium-Vanadium Steels
61xx	Cr 0.60% or 0.80% or 0.95%, V 0.10% or 0.15% min
Tungsten-Chromium Steels
72xx	W 1.75%, Cr 0.75%
Silicon-Manganese Steels
92xx	Si 1.40% or 2.00%, Mn 0.65% or 0.82% or 0.85%, Cr 0.00% or 0.65%
High-Strength Low-Alloy Steels
9xx	Various SAE grades
xxBxx	Boron steels
xxLxx	Leaded steels

[edit] Stainless steel

200 Series—austenitic chromium-nickel-manganese alloys
300 Series—austenitic chromium-nickel alloys
- Type 301—highly ductile, for formed products. Also hardens rapidly during mechanical working.
- Type 303—Free machining version of 304 via addition of sulfur
- Type 304—the most common; the classic 18/8 stainless steel.
- Type 316—the next most common; for food and surgical stainless steel uses; Alloy addition of molybdenum prevents specific forms of corrosion. Also known as "marine grade" stainless steel due to its increased ability to resist saltwater corrosion compared to type 304. SS316 is often used for building nuclear reprocessing plants.
400 Series—ferritic and martensitic chromium alloys
- Type 408—heat-resistant; poor corrosion resistance; 11% chromium, 8% nickel.
- Type 409—cheapest type; used for automobile exhausts; ferritic (iron/chromium only).
- Type 410—martensitic (high-strength iron/chromium).
- Type 416
- Type 420—"Cutlery Grade" martensitic; similar to the Brearley's original "rustless steel". Also known as "surgical steel".
- Type 430—decorative, e.g., for automotive trim; ferritic.
- Type 440—a higher grade of cutlery steel, with more carbon in it, which allows for much better edge retention when the steel is heat treated properly.
500 Series—heat resisting chromium alloys
600 Series—martensitic precipitation hardening alloys
- Type 630—most common PH stainless, better known as 17-4; 17% chromium, 4% nickel

**AISI Carbon and Alloy Steel Designations**^[2]
AISI Type (UNS Designation)	Typical Composition [%]
Austenitic
201 (S20100)	16-18 Cr, 3.5-5.5 Ni, 0.15 C, 5.5-7.5 Mn, 0.75 Si, 0.060 P, 0.030 S, 0.25 N
202 (S20200)	17-19 Cr, 4-6 Ni, 0.15 C, 7.5-10.0 Mn, 0.75 Si, 0.060 P, 0.030 S, 0.25 N
205 (S20500)	16.5-18 Cr, 1-1.75 Ni, 0.12-0.25 C, 14-15.5 Mn, 0.75 Si, 0.060 P, 0.030 S, 0.32-0.40 N
301 (S30100)	16-18 Cr, 6-8 Ni, 0.15 C, 2.0 Mn, 0.75 Si, 0.045 P, 0.030 S
302 (S30200)	17-19 Cr, 8-10 Ni, 0.15 C, 2.0 Mn, 0.75 Si, 0.045 P, 0.030 S, 0.10 N
302B (S30215)	17-19 Cr, 8-10 Ni, 0.15 C, 2.0 Mn, 2.0-3.0 Si, 0.045 P, 0.030 S
303 (S30300)	17-19 Cr, 8-10 Ni, 0.15 C, 2.0 Mn, 1.0 Si, 0.20 P, 0.015 S min, 0.60 Mo (optional)
303Se (S30323)	17-19 Cr, 8-10 Ni, 0.15 C, 2.0 Mn, 1.0 Si, 0.20 P, 0.060 S, 0.15 Se min
304 (S30400)	18-20 Cr, 8-10.50 Ni, 0.08 C, 2.0 Mn, 0.75 Si, 0.045 P, 0.030 S, 0.10 N
304L (S30403)	18-20 Cr, 8-12 Ni, 0.03 C, 2.0 Mn, 0.75 Si, 0.045 P, 0.030 S, 0.10 N
304 Cu (S30430)	17-19 Cr, 8-10 Ni, 0.08 C, 2.0 Mn, 0.75 Si, 0.045 P, 0.030 S, 3-4 Cu
304N (S30451)	18-20 Cr, 8-10.50 Ni, 0.08 C, 2.0 Mn, 0.75 Si, 0.045 P, 0.030 S, 0.10-0.16 N
305 (S30500)	17-19 Cr, 10.50-13 Ni, 0.12 C, 2.0 Mn, 0.75 Si, 0.045 P, 0.030 S
308 (S30800)	19-21 Cr, 10-12 Ni, 0.08 C, 2.0 Mn, 1.0 Si, 0.045 P, 0.030 S
309 (S30900)	22-24 Cr, 12-15 Ni, 0.20 C, 2.0 Mn, 1.0 Si, 0.045 P, 0.030 S
309S (S30908)	22-24 Cr, 12-15 Ni, 0.08 C, 2.0 Mn, 1.0 Si, 0.045 P, 0.030 S
310 (S31000)	24-26 Cr, 19-22 Ni, 0.25 C, 2.0 Mn, 1.5 Si, 0.045 P, 0.030 S
310S (S31008)	24-26 Cr, 19-22 Ni, 0.08 C, 2.0 Mn, 1.5 Si, 0.045 P, 0.030 S
314 (S31400)	23-26 Cr, 19-22 Ni, 0.25 C, 2.0 Mn, 1.5-3.0 Si, 0.045 P, 0.030 S
316 (S31600)	16-18 Cr, 10-14 Ni, 0.08 C, 2.0 Mn, 0.75 Si, 0.045 P, 0.030 S, 2.0-3.0 Mo, 0.10 N
316L (S31603)	16-18 Cr, 10-14 Ni, 0.03 C, 2.0 Mn, 0.75 Si, 0.045 P, 0.030 S, 2.0-3.0 Mo, 0.10 N
316F (S31620)	16-18 Cr, 10-14 Ni, 0.08 C, 2.0 Mn, 1.0 Si, 0.20 P, 0.10 S min, 1.75-2.50 Mo
316N (S31651)	16-18 Cr, 10-14 Ni, 0.08 C, 2.0 Mn, 0.75 Si, 0.045 P, 0.030 S, 2-3 Mo, 0.10-0.16 N
317 (S31700)	18-20 Cr, 11-15 Ni, 0.08 C, 2.0 Mn, 0.75 Si, 0.045 P, 0.030 S, 3.0-4.0 Mo, 0.10 N max
321 (S32100)	17-19 Cr, 9-12 Ni, 0.08 C, 2.0 Mn, 0.75 Si, 0.045 P, 0.030 S, [Ti, 5(C + N) min, 0.70 max], 0.10 N max
329 (S32900)	23-28 Cr, 2.5-5 Ni, 0.08 C, 2.0 Mn, 0.75 Si, 0.040 P, 0.030 S, 1-2 Mo
330 (N08330)	17-20 Cr, 34-37 Ni, 0.08 C, 2.0 Mn, 0.75-1.50 Si, 0.040 P, 0.030 S
347 (S34700)	17-19 Cr, 9-13 Ni, 0.08 C, 2.0 Mn, 0.75 Si, 0.045 P, 0.030 S (Nb + Ta, 10 x C min, 1 max)
348 (S34800)	17-19 Cr, 9-13 Ni, 0.08 C, 2.0 Mn, 0.75 Si, 0.045 P, 0.030 S (Nb + Ta, 10 x C min, 1 max, but 0.10 Ta max), 0.20 Ca
384 (S38400)	15-17 Cr, 17-19 Ni, 0.08 C, 2.0 Mn, 1.0 Si, 0.045 P, 0.030 S
Ferritic
405 (S40500)	11.5-14.5 Cr, 0.08 C, 1.0 Mn, 1.0 Si, 0.040 P, 0.030 S, 0.1-0.3 Al, 0.60 max
409 (S40900)	10.5-11.75 Cr, 0.08 C, 1.0 Mn, 1.0 Si, 0.045 P, 0.030 S, 0.05 Ni (Ti 6 x C, but 0.75 max)
429 (S42900)	14-16 Cr, 0.12 C, 1.0 Mn, 1.0 Si, 0.040 P, 0.030 S, 0.75 Ni
430 (S43000)	16-18 Cr, 0.12 C, 1.0 Mn, 1.0 Si, 0.040 P, 0.030 S, 0.75 Ni
430F (S43020)	16-18 Cr, 0.12 C, 1.25 Mn, 1.0 Si, 0.060 P, 0.15 S min, 0.60 Mo optional
430FSe (S43023)	16-18 Cr, 0.12 C, 1.25 Mn, 1.0 Si, 0.060 P, 0.060 S, 0.15 Se min
434 (S43400)	16-18 Cr, 0.12 C, 1.0 Mn, 1.0 Si, 0.040 P, 0.030 S, 0.75-1.25 Mo
436 (S43600)	16-18 Cr, 0.12 C, 1.0 Mn, 1.0 Si, 0.040 P, 0.030 S, 0.75-1.25 Mo (Nb + Ta 5 x C min, 0.70 max)
442 (S44200)	18-23 Cr, 0.20 C, 1.0 Mn, 1.0 Si, 0.040 P, 0.030 S
446 (S44600)	23-27 Cr, 0.20 C, 1.5 Mn, 1.0 Si, 0.040 P, 0.030 S, 0.25 Ni
Martensitic
403 (S40300)	11.5-13.0 Cr, 0.15 C, 1.0 Mn, 0.5 Si, 0.040 P, 0.030 S, 0.060 Ni
410 (S41000)	11.5-13.5 Cr, 0.15 C, 1.0 Mn, 1.0 Si, 0.040 P, 0.030 S, 0.75 Ni
414 (S41400)	11.5-13.5 Cr, 1.25-2.50 Ni, 0.15 C, 1.0 Mn, 1.0 Si, 0.040 P, 0.030 S
416 (S41600)	12-14 Cr, 0.15 C, 1.25 Mn, 1.0 Si, 0.060 P, 0.15 S min, 0.060 Mo optional
416Se (S41623)	12-14 Cr, 0.15 C, 1.25 Mn, 1.0 Si, 0.060 P, 0.060 S, 0.15 Se min
420 (S42000)	12-14 Cr, 0.15 C min, 1.0 Mn, 1.0 Si, 0.040 P, 0.030 S
420F (S42020)	12-14 Cr, over 0.15 C, 1.25 Mn, 1.0 Si, 0.060 P, 0.15 S min, 0.60 Mo max (optional)
422 (S42200)	11-12.50 Cr, 0.50-1.0 Ni, 0.20-0.25 C, 0.5-1.0 Mn, 0.5 Si, 0.025 P, 0.025 S, 0.90-1.25 Mo, 0.20-0.30 V, 0.90-1.25 W
431 (S43100)	15-17 Cr, 1.25-2.50 Ni, 0.20 C, 1.0 Mn, 1.0 Si, 0.040 P, 0.030 S
440A (S44002)	16-18 Cr, 0.60-0.75 C, 1.0 Mn, 1.0 Si, 0.040 P, 0.030 S, 0.75 Mo
440B (S44003)	16-18 Cr, 0.75-0.95 C, 1.0 Mn, 1.0 Si, 0.040 P, 0.030 S, 0.75 Mo
440C (S44004)	16-18 Cr, 0.95-1.20 C, 1.0 Mn, 1.0 Si, 0.040 P, 0.030 S, 0.75 Mo
Heat Resisting
501 (S50100)	4-6 Cr, 0.10 C min, 1.0 Mn, 1.0 Si, 0.040 P, 0.030 S, 0.40-0.65 Mo
502 (S50200)	4-6 Cr, 0.10 C, 1.0 Mn, 1.0 Si, 0.040 P, 0.030 S, 0.40-0.65 Mo

[edit] Other steels

The standards organization ASTM International produces standards for structural steel used in the construction industry. Those steel alloys have designations which start with A, for example A36, A588, or A514.

[edit] References

^ Erik Oberg, et. al., "Machinery's Handbook," 25th ed., Industrial Press Inc., 1996, p. 406.
^ Erik Oberg, et. al., "Machinery's Handbook," 25th ed., Industrial Press Inc., 1996, pp. 411-412.