Form: This specification covers an aircraft-quality@ low-alloy steel in the form of sheet@ strip@ and plate. Application: These products have been used typically for heat treated parts requiring good tensile and fatigue strengths in combination with good ductility@ but usage is not limited to such applications. The product may be through-hardened to tensile strength ranges of 260@000 - 280@000 psi (1795 to 1930 MPa) in nominal section thickness of 1.5 in. (38 mm) and under and 180@000 - 22@000 psi(1240 - 1515 MPa) in nominal section thicknesses of 3 in. (75 mm) and under.