Form This specification covers a premium aircraft-quality@ low-alloy steel in the form of bars@ forgings@ mechanical tubing@ and forging stock. Application These products have been used typically for parts requiring a through-hardening steel capable of developing a combination of high tensile strength@ ductility@ and fracture toughness@ but usage is not limited to such applications. Certain design and processing procedures may cause these products to become susceptible to stress-corrosion cracking after heat treatment. ARP1110 recommends practices to minimize such conditions.