| Designation | Class I (percent) | Class II (percent) | Class III (percent) |
|---|---|---|---|
| Carbon, maximum | 0.50 | 0.50 | 0.53 |
| Manganese, maximum | 1.65 | 1.65 | 1.85 |
| Phosphorus, maximum | .05 | .05 | .05 |
| Sulphur, maximum | .06 | .05 | .05 |
| Silicon, maximum | .35 | .30 | .37 |
| Molybdenum, maximum | .25 | .30 | |
| Chromium, maximum | .30 | .30 | |
| Sum of manganese and carbon not over | 2.10 | 2.10 | |
| Note 1: Alternate steel containing other alloying elements may be used if approved. | |||