1.1This specification covers relatively thin-walled forgings (including gas bottles) for pressure vessel use. Three types of carbon steel and six types of alloy steel are included. Provision is made for integrally forging the ends of vessel bodies made from seamless pipe or tubing.
Note 1:When working to the chemical and tensile requirements of this specification, the influence of wall thickness and cooling rate will necessarily eliminate certain forging sizes in each class.
Note 2:Designations have been changed as follows:
| Current | Formerly |
| Grade A | Type I |
| Grade B | Type II |
| Grade C | Type III |
| Grade D | Type IV |
| Grade E Class 55 | Type V Grade 1 Class 55 |
| Grade E Class 65 | Type V Grade 1 Class 65 |
| Grade E Class 70 | Type V Grade 1 Class 70 |
| Grade F Class 55 | Type V Grade 2 Class 55 |
| Grade F Class 65 | Type V Grade 2 Class 65 |
| Grade F Class 70 | Type V Grade 2 Class 70 |
| Grade G Class 55 | Type V Grade 3 Class 55 |
| Grade G Class 65 | Type V Grade 3 Class 65 |
| Grade G Class 70 | Type V Grade 3 Class 70 |
| Grade H Class 55 | Type V Grade 4 Class 55 |
| Grade H Class 65 | Type V Grade 4 Class 65 |
| Grade H Class 70 | Type V Grade 4 Class 70 |
| Grade J Class 55 | Type V Grade 5 Class 55 |
| Grade J Class 65 | Type V Grade 5 Class 65 |
| Grade J Class 70 | Type V Grade 5 Class 70 |
| Grade K | Type VI |
| Grade L | Type VII |
| Grade J Class 110 | Type VIII |
| Grade M Class 85 | Type IX Class A |
| Grade M Class 100 | Type IX Class B |
1.2The 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.
1.3Unless the order specifies the applicable “M” specification designation (SI units), the material shall be furnished to inch-pound units.