Description

1.1 This specification covers chromium-tungsten-molybdenum-vanadium, with or without tantalum, alloy steel plates intended primarily for welded boilers and pressure vessels designed for elevated temperature service.

1.2 Plates are available under this specification in two grades having different alloy contents as follows:

Grade	Nominal Chromium Content, %	Nominal Tungsten Content, %	Nominal Molybdenum Content, %	Nominal Vanadium Content, %	Nominal Tantalum Content, %
315	3.00	1.50	0.75	0.25

315T	3.00	1.50	0.75	0.25	0.10

1.3 The maximum thickness of plates is limited only by the capacity of the composition to meet the specified mechanical property requirements.

1.4 The specification is expressed in both inch-pound units and in SI units; however, unless the order specifies the applicable “M“ specification designation (SI units), the plates are furnished to inch-pound units.

1.5 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.