AISI / SAE STEEL NUMBERING SYSTEM


  • The first two numbers indicate the alloy according the the chart below.
  • The last two numbers indicate the amount of carbon in the alloy, where the digits “10”, for example, represent 0.10% carbon.

Example AISI/SAE 1020

  • the first two digits indicate this is plain carbon steel.
  • the last two digits indicates that the steel contains approximately 0.20% carbon.

Example AISI/SAE 4340

  • the first two digits indicate this is a Nickel-Chromium-Molybdenum alloy steel
  • the last two digits indicate that the steel contains approximately 0.4% carbon
AISI/SAE Steel Numbering System
Carbon steels 10XX Plain carbon, Mn 1.00% max
11XX Resulfurized free machining
12XX Resulfurized/rephosphorized free machining
15XX Plain carbon, Mn 1.00-1.65%
Manganese steel 13XX Mn 1.75%
Nickel steels 23XX Ni 3.50%
25XX Ni 5.00%
Nickel-chromium steels 31XX Ni 1.25%, Cr .65-.80%
32XX Ni 1.75%, Cr 1.07%
33XX Ni 3.50%, Cr 1.50-1.57%
34XX Ni 3.00%, Cr .77%
Molybdenum steels 40XX Mo .20-.25%
44XX Mo .40-.52%
Chromium-molybdenum steels 41XX Cr .50-.95%, Mo .12-.30%
Nickel-chromium-molybdenum steels 43XX Ni 1.82%, Cr .50-.80%, Mo .25%
47XX Ni 1.05%, Cr .45%, Mo .20-.35%
Nickel-molybdenum steels 46XX Ni .85-1.82%, Mo .20-.25%
48XX Ni 3.50%, Mo .25%
Chromium steels 50XX Cr .27-.65%
51XX Cr .80-1.05%
50XXX Cr .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 .60-.95%, V .10-.15%
Tungsten-chromium steels 72XX W 1.75%, Cr .75%
Nickel-chromium-molybdenum steels 81XX Ni .30%, Cr .40%, Mo .12%
86XX Ni .55%, Cr .50%, Mo .20%
87XX Ni .55%, Cr .50%, Mo .25%
88XX Ni .55%, Cr .50%, Mo .35%
Silicon-manganese steels 92XX Si 1.40-2.00%, Mn .65-.85%, Cr 0-.65%
Nickel-chromium-molybdenum steels 93XX Ni 3.25%, Cr 1.20%, Mo .12%
94XX Ni .45%, Cr .40%, Mo .12%
97XX Ni .55%, Cr .20%, Mo .20%
98XX Ni 1.00%, Cr .80%, Mo .25%

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