1.1This specification2 covers chromium-molybdenum alloy steel plates intended primarily for welded boilers and pressure vessels designed for elevated temperature service.

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

	Nominal	Nominal
	Chromium	Molybdenum
Grade	Content, %	Content, %
2	0.50	0.50
12	1.00	0.50
11	1.25	0.50
22, 22L	2.25	1.00
21, 21L	3.00	1.00
5	5.00	0.50
9	9.00	1.00
91	9.00	1.00

1.3Each grade except Grades 21L, 22L, and 91 is available in two classes of tensile strength levels as defined in the Tensile Requirements tables. Grades 21L and 22L are available only as Class 1. Grade 91 is available only as Class 2.

Note 1:Grade 911, previously covered by this specification, is now covered by Specification A1017/A1017M.

1.4The maximum thickness of plates is limited only by the capacity of the composition to meet the specified mechanical property requirements.

1.5The values stated in either inch-pound units or SI units are to be regarded separately as standard. Within the text, 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 this specification.