4340 is a 1.8% nickel – chromium – molybdenum high hardenability high tensile steel – generally supplied hardened and tempered in the tensile range of 930 – 1080 Mpa (condition U) – (Rc 28 – 36).. Characterized by high strength and toughness in relatively large sections. Prehardened and tempered 4340 can be further surface hardened by flame or induction hardening and by nitriding.
