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 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 steels.

1.2 Plates under this specification are available in three classes, as follows:

1.2.1 Class 1—As-rolled and precipitation heat treated. Available in thicknesses of ¾ in. [20 mm] and under. Grade A, Class 1 has a minimum specified tensile strength of 90 ksi. Grade C, Class 1 has a minimum specified tensile strength of 100 ksi.

1.2.2 Class 2—Normalized and precipitation heat treated.

1.2.2.1 Available in Grade A only. Grade A has minimum specified tensile strength of 72 ksi for thinner plates and 65 and 60 ksi for thicker plates, with the minimum tensile strength dependent upon the plate thickness. The maximum thickness of Grade A, Class 2 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].

1.2.3 Class 3—Quenched and precipitation heat treated.

1.2.3.1 Available as Grade A 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].

1.2.3.2 Available as Grade C with a specified minimum tensile strength of 95 ksi for plates ¾in. [20 mm] and under in thickness and 90 ksi for plates over ¾ in. in thickness. The maximum thickness of Grade C, Class 3, plates is 2 in. [50 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.