Form 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. Application 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.