Form: This Specification covers an aircraft-quality@ low-alloy steel in the form of bars@ forgings@ flash welded rings@ and stock for forging and flash welded rings. Application: Primarily for parts 0.50 inch (12.7 mm) and under in nominal section thickness at time of heat treatment requiring a through-hardening steel capable of developing hardness as high as 50 HRC when properly hardened and tempered and also for parts of greater thickness requiring proportionately lower hardness. Certain design and processing procedures may cause these products to become susceptible to stress-corrosion cracking after heat treatment; ARP1110 recommends practice to minimize such conditions.