1. 11/18/13 eFunda: General Information on Carbon Steels
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Carbon Steels
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General Information
Carbon steels are steels whose alloying elements do not exceed the following limits:
Element Max weight %
C 1.00
Cu 0.60
Mn 1.65
P 0.40
Si 0.60
S 0.05
Designation
Carbon steels are designated by distinct AISI (American Iron and Steel Institute) four-digit numbers. The
first two digits indicate the grades of the steels, while the last two digits give the nominal carbon content of
the alloy in hundredths of a percent. Here is an example:
XX :0.xx% average carbon content
AISI 10 60
10 :Nonresulfurized grades
11 :Resulfurized grades
12 :Resulfurized and rephosphorized grades
15 :Nonsulfurized grades; max Mn content > 1%
If a letter L or B shows up between the second and third digits of an AISI number, it means that this grade
is either a Leaded steel or a Boron steel; Sometimes a suffix H is attached to a AISI number to indicate that
the steel has been produced to prescribed hardenability limits. Examples are:
Leaded steels :AISI 12L14, AISI 12L15...
Boron steels :AISI 15B48H...
H-steels :AISI 1038H, AISI 15B48H...
