1.1 This specification covers 9 % nickel-alloy steel plates produced by the direct-quenching process. The plates are intended primarily for use in welded pressure vessels.

1.2 The direct-quenching process consists of quenching the plates directly after rolling, without permitting the plates to cool below the critical temperature prior to initiation of the quenching operation, and subsequently tempering the plates. (This differs from the “conventional” process in which the plates are permitted to cool to a temperature significantly below the critical temperature, usually to ambient temperature, prior to reheating to a temperature above the upper critical temperature, then quenching, and subsequently tempering.)

1.3 The maximum nominal thickness of plates furnished under this specification shall not exceed 2 in. [50 mm].

1.4 This material is susceptible to magnetization. Use of magnets in handling after heat treatment should be avoided if residual magnetism would be detrimental to subsequent fabrication or service.

1.5 The values stated in either inch-pound 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.