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, 0.50 inch (12.7 mm) and under in section thickness at time of heat treatment, requiring a through-hardened steel capable of developing hardness as high as 35 HRC when hardened and tempered, and also parts of greater thickness but requiring proportionately lower hardness, but usage is not limited to such applications.