This specification covers quenched and tempered vacuum-treated carbon and alloy steel forgings for pressure vessels, such as those used in reactor systems, specifically, vessel closures, shells, flanges, tube sheets, rings, heads, and similar parts. Steels shall be manufactured by basic electric-furnace process except when secondary ladle refining or remelting process is employed, and shall be vacuum treated prior to or during the pouring of the ingot. Materials shall also go through preliminary heat treatment and quenching for mechanical properties. Heat and product analyses shall be executed to evaluate the conformance of the forgings with specified chemical requirements. Tension and Charpy impact tests shall also be performed to examine the conformance of steel specimens with the following mechanical properties: tensile strength, yield strength, elongation, and reduction of area. Nondestructive inspection procedures, such as magnetic particle examination, and longitudinal wave and angle beam ultrasonic examination, shall also be carried out. Repair welding may be permitted at the option of the purchaser.

1.1 This specification2 covers quenched and tempered vacuum-treated carbon and alloy steel forgings for pressure vessels such as those used in reactor systems. Specifically, it covers forgings for vessel closures, shells, flanges, tube sheets, rings, heads, and similar parts.

1.2 All grades are considered weldable under proper conditions. Welding technique is of fundamental importance, and it is presupposed that welding procedure and inspection will be in accordance with approved methods for the grade of material used.

1.3 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.

1.4 Unless the order specifies the applicable “M” specification designation, the material shall be furnished to the inch-pound units.

Note 1: Grades 1 and 1A are composed of different chemistries but have the same mechanical requirements.

Note 2: Designations have been changed as follows:

  Current

Formerly

Grade 1

Class 1

Grade 1A

Class 1A

Grade 2 Class 1

Class 2

Grade 2 Class 2

Class 2A

Grade 3 Class 1

Class 3

Grade 3 Class 2

Class 3A

Grade 4N Class 1

Class 4

Grade 4N Class 2

Class 4A

Grade 4N Class 3

Class 4B

Grade 5 Class 1

Class 5

Grade 5 Class 2

Class 5A

Grade 22 Class 3

Class 22B

Grade 22 Classes 4, 5, 6, and 7

Grade 3V

Class 3V

1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

1.6 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.