| 420 / | HD | ALLOYS OR METALLIC COMPOSITIONS |
| 8 | DF | FERROUS (I.E., IRON BASE) {24} |
| 9 | DF | .~ 1.7 percent or more carbon containing {2} |
| 13 | DF | .~.~ 2.7 percent or more carbon equivalent containing (i.e., cast iron) {7} |
| 29 | | .~.~.~ Processes {4} |
| 30 | DF | .~.~.~.~> Adding rare earth or alkaline earth metal |
| 31 | DF | .~.~.~.~> Adding sulfur, selenium or tellurium |
| 32 | DF | .~.~.~.~> Adding vanadium, titanium, niobium, or zirconium |
| 33 | DF | .~.~.~.~> Adding silicon |