1.1This specification2 covers one type of manganese-molybdenum and four types of manganese-molybdenum-nickel alloy steel plates for use in the quenched and tempered condition for the construction of welded pressure vessels.

1.2Material under this specification is available in five types, designated “A”, “B”, “C”, “D”, and “E”. The material is also available in three classes having the following strength levels.

1.3The maximum thickness of Class 1 and Class 2 plates is limited only by the capacity of the composition to meet the specified mechanical property requirements; however, current practice normally limits the maximum thickness to 12 in. [300 mm] for Types A through D and to 7 in. [180 mm] for Type E.

1.4The maximum thickness of Class 3 plates is 2¹/₂in. [65 mm] for Types A through D and 2 in. [50 mm] for Type E.

1.5The minimum nominal thickness of plates of all classes is 0.25 in. [6.5 mm].

1.6These alloy steel plates in the as-rolled condition are sensitive to cracking during transit and handling, particularly in thicknesses over about 1 or 2 in. [25 or 50 mm]. They should be shipped in the as-rolled conditions only by mutual agreement of manufacturer and the purchaser.

1.7Plates covered by this specification are often used in the beltline region of nuclear reactor vessels where the material properties may be affected by high levels of radiation. Appendix X1 provides some information pertinent to this usage.

1.8The 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.