1.1This specification 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.
1.2All 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.
1.3The 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.
1.4Unless 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 |
1.5This 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.6This 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.