FormThis specification covers an aircraft-quality@ low-alloy steel in the form of bars@ forgings@ mechanical tubing@ and forging stock.ApplicationThis product has been used typically for carburized parts for which a high minimum core hardness is required and a wide hardness range in sections 0.375 inch (9.52 mm) and under in nominal thickness is permitted@ but usage is not limited to such applications. The core may or may not be machinable after hardening.