This specification covers two grades of low-carbon age-hardening alloy steel plates for welded pressure vessels and piping components. The two grades are nickel-copper-chromium-molybdenum-columbium and nickel-copper-manganese-molybdenum-columbium alloy steel. The heat treatment procedure for class 1, 2, 3 plates are presented. The steel shall conform to the required chemical compositions. Mechanical property requirements of the steel plates that include tension test requirements and notch-toughness requirements are presented in details.

1.1 This specification² covers low-carbon age-hardening alloy steel plates for welded pressure vessels and piping components. The specification covers nickel-copper-chromium-molybdenum-columbium steel.

1.2 Plates under this specification are available as follows:

1.2.1 Available in Grade A, Class 3 only.

1.2.1.1 Quenched and precipitation heat treated with a minimum specified tensile strength of 85 ksi for thinner plates and 75 and 70 ksi for thicker plates, with the minimum tensile strength dependent upon the plate thickness. The maximum thickness of Grade A, Class 3 plates is limited only by the capacity of the chemical composition and heat treatment to meet the specified mechanical property requirements; however, current practice usually limits the maximum thickness to 8 in. [200 mm].

1.3 This 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 material shall be furnished in inch-pound units.

1.4 The 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 this specification.