A570 - 79 Standard Specification for Hot-Rolled Carbon Steel Sheet And Strip, Structural Quality , Steel grades according to American standards - A36, Chemical composition A36 - 04b A36 0.26 0.05 0.04 0.40 A572 - 04 Grade 42 0.21 1.35 0.05 0.04 0.40 Grade 50 0.23 1.35 0.05 0.04 0.40