This specification covers chromium-molybdenum-tungsten alloy steel plates intended primarily for welded boilers and pressure vessels designed for elevated temperature service. The plates shall be available in three grades, namely Grades 23, 911, and 122, having different alloy contents. The maximum thickness of plates is limited only by the capacity of the composition to meet the specified mechanical requirements. The steel shall be killed and the plates shall undergo heat treatment. In order to determine mechanical properties such as yield strength and elongation, the plates shall be subjected to tension and hardness tests.

1.1 This specification covers Chromium-Molybdenum-Tungsten alloy steel plates intended primarily for welded boilers and pressure vessels designed for elevated temperature service.

1.2 Plates are available under this specification in grades having different alloy contents as follows:

Grade

Nominal
Chromium
Content, %

Nominal
Molybdenum
Content, %

Nominal
Tungsten
Content, %

23

2.25

0.20

1.60

911

9.00

1.00

1.00

92

9.00

0.45

1.75

122

12.00

0.40

2.00

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

1.4 The specification is expressed in both inch-pound units and in SI units. However, unless the order specifies the applicable “M” specification designation (SI units), the material shall be furnished to inch-pound units.

1.5 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.

1.6 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.