This specification covers an aircraft-quality, low-alloy steel in the form of sheet, strip, and plate. These welding products have been used typically for heat treated parts and structures that may require welding during fabrication, but usage is not limited to such applications. Product, 0.375 inch (9.52 mm) and under in nominal thickness, may be through-hardened to a minimum tensile strength of 180 ksi (1241 MPa) and proportionately lower strength in heavier section thicknesses.