This specification covers high-tensile strength carbon-manganese steel plates intended for welded pressure vessels. 1.2This steel is usually made to a semi-killed or capped deoxidation practice; however, at the purchaser's or the steel producer's option, the steel may be made silicon-killed or aluminum-killed. 1.3The maximum thickness of plates furnished under this specification shall be ¾ in. [20 mm]. 1.4For plates produced from coil and furnished without heat treatment or with stress relieving only, the additional requirements, including additional testing requirements and the reporting of additional test results, of Specification A20/A20M apply.1.5The values stated in either inch-pound units or SI units are to be regarded separately as standard. Within the text, the SI units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system must be used independently of the other. Combining values from the two systems may result in nonconformance with the specification.