This specification covers nickel-chromium-molybdenum alloy steel plates for use in the quenched and tempered condition, intended for the fabrication of welded pressure vessels and other pressure equipment. Material under this specification is available in two types, B and C. The material is also available in three classes as follows: Class 1; Class 2; and Class 3. The steel shall be killed and shall conform to the fine austenitic grain size requirement. All plates shall be heat treated by heating to a suitable austenitizing temperature. The steel shall conform to the chemical requirements specified. Tension tests shall be made to meet the required specifications.

1.1 This specification2 covers nickel-chromium-molybdenum alloy steel plates for use in the quenched and tempered condition, intended for the fabrication of welded pressure vessels and other pressure equipment. These alloy compositions are normally considered for construction involving plate thicknesses of 2 in. [50 mm] or greater.

1.2 Material under this specification is available in two types, B and C. The material is also available in three classes as follows:

  Class

Minimum Tensile Strength, ksi [MPa]

1

105 [725]

2

115 [795]

3

 90 [620]

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

1.4 The minimum plate thickness is ³/₁₆ in. [5 mm].

1.5 These alloy steel plates in the as-rolled condition are sensitive to cracking during flame cutting, transit, and handling. They should be shipped in the as-rolled condition only with the mutual agreement of the manufacturer and the purchaser or fabricator.

1.6 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 necessarily 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 specification.

1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.