This specification covers an aircraft-quality, low-alloy steel in the form of bars, forgings, flash welded rings, and stock for forging or flash welded rings. These products have been used typically for parts, 0.75 inch (19.0 mm) and under in nominal section thickness at the time of heat treatment, requiring a through-hardening steel capable of developing hardness as high as 40 HRC when properly hardened and tempered and for parts of greater thickness but requiring proportionally lower hardness but usage is not limited to such applications.