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... |
|
Bluish.ice 