This specification covers a premium aircraft-quality, low-alloy steel in the form of bars, forgings, mechanical tubing, flash welded rings, and stock for forging or flash welded rings. These products have been used typically for heat treated parts, which may be welded during fabric requiring through-hardening to high strength levels and which may be used at operational stress levels approaching the yield strength, but usage is not limited to such applications. This steel may become notch-sensitive when heat treated to a tensile strength level of 240,000 psi (1655 MPa) or higher.