Basic Numbering Sytem
for AISI & SAE Steels


     
       The AISI and SAE identification systems are based upon the varying     amounts of carbon and other elements in the steel. The four or five digit designation identifies which alloys are present and the percentage of    carbon in the steel:
 
1st number:

2nd number:
 

3rd & 4th number:
 

 The first number indicates the major alloying element. 

The second number indicates the approximate 
percentage of the major alloying element. 

The third and fourth numbers indicate the carbon    content of the steel.

       The percentage values given are not exact and other elements may be   present... 
 
Type of Steel and Average Chemical Contents in % Numbers & Digits
Carbon Steels
      Plain Carbon ..........................................................
      Free Cutting.............................................................

Manganese Steels
      Mn I.75....................................................................

Nickel Steels
      Ni 3.50 ....................................................................
      Ni 5.00.....................................................................

Nickel-Chromium Steels
      Ni 1.25; Cr .65.........................................................
      Ni 3.50; Cr I.57........................................................
      Corrosion and Heat Resisting . .................................

Molybdenum Steels
      Mo 0.25...................................................................

Chromium-Molybdenum Steels
      Cr 0.50 and 0.95; Mo 0.25. 0.20. and 0.12 ................

Nickel-Chromium-Molybdenum Steels
      Ni 1.82; Cr 0.50 and 0.80; Mo 0.25...........................
      Ni 1.05; Cr 0.45; Mo 0.20.........................................
      Ni 0.55; Cr 0.50 and 0.65; Mo 0.20...........................
      Ni 0.55; Cr 0.5o; Mo 0.25.........................................
      Ni 3.25; Cr 1.20; Mo 0.12.........................................
      Ni I.00; Cr 0.80; Mo 0.25..........................................

Nickel-Molybdenum Steels
      Ni 1.57 and 1.82; Mo 0.20 and 0.25...........................
      Ni 3.50; Mo 0.25.......................................................

Chromium Steels
      Low Cr - Cr 0.27, 0.40 and 0.50................................
      Low Cr - Cr 0.80, 0.87, 0.92, 0.95, 1.00, and 1.05 ....
      Low Cr (bearing) Cr 0.50..........................................
      Medium Cr (bearing) Cr 1.02.....................................
      High Cr (bearing) Cr 1.45..........................................
      Corrosion and Heat Resisting ....................................

Chromium-Vanadium Steel
      Cr 0.8o and 0.95; V 0.10 and 0.15 min ......................

Silicon-Manganese Steels
      Mn 0.65, 0.82, 0.87, and 0.85; Si 1.40 and 2.00; Cr, 
      None, 0.17, 0.32, and 0.65.......................................

Low Alloy, High Tensile .................................................
Boron Intensified Steels, B denotes Boron Steel .............
Leaded Steels, L denotes Leaded Steel .........................

 X
10xx
11xx

XX
13xx

XX
23xx
25xx

XX
31xx
33xx
303xx

XX
40xx

XX
41xx

XX
43xx
47xx
86xx
87xx
93xx
98xx

XX
46xx
48xx

XX
50xx
51xx
501xx
511xx
521xx
514xx & 515xx
XX
61xx

XX
XX
92xx

950
xxBxx
xxLxx 
Index