1.1 This 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 Grade B Grade C Grade D Grade E Class 55 Grade E Class 65 Grade E Class 70 Grade F Class 55 Grade F Class 65 Grade F Class 70 Grade G Class 55 Grade G Class 65 Grade G Class 70 Grade H Class 55 Grade H Class 65 Grade H Class 70 Grade J Class 55 Grade J Class 65 Grade J Class 70 Grade K Grade L Grade J Class 110 Grade M Class A Grade M Class B Type I Type II Type III Type IV Type V Grade 1 Class 55 Type V Grade 1 Class 65 Type V Grade 1 Class 70 Type V Grade 2 Class 55 Type V Grade 2 Class 65 Type V Grade 2 Class 70 Type V Grade 3 Class 55 Type V Grade 3 Class 65 Type V Grade 3 Class 70 Type V Grade 4 Class 55 Type V Grade 4 Class 65 Type V Grade 4 Class 70 Type V Grade 5 Class 55 Type V Grade 5 Class 65 Type V Grade 5 Class 70 Type VI Type VII Type VIII Type IX Class A Type IX Class B

1.2 The values stated in either inch-pound or SI [metric] units are to be regarded separately as the standard. Within the text and the tables, 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 the specification.

1.3 Unless the order specifies the applicable "M" specification designation (SI units), the material shall be furnished to inch-pound units.