Form: This specification covers an aircraft-quality@ low-alloy steel in the form of sheet@ strip@ and plate. Application: Primarily for thick-section heat treated parts requiring good tensile and endurance strengths in combination with good ductility. The product may be thought-hardened to tensile strength ranges of 260@000 - 280@000 psi (1793 - 1931 MPa) in sections of 1.5 in. (38 mm) and under in nominal thickness and 180@000 - 220@000 psi (1241 - 1517 MPa) in nominal section thicknesses up to 3 in. (75 mm).