1.1 This specification covers quenched and tempered alloy steel plates of structural quality in thicknesses of 6 in. [150 mm] and under intended primarily for use in welded bridges and other structures. This specification covers high-yield, quenched, and tempered alloy steel plates for use in welded bridges and other structures. Plates shall be subjected to heat treatment to conform to the tensile and hardness requirements for thickness, tensile stren