This specifications covers chromium-molybdenum alloy steel plates intended primarily for welded boilers and pressure vessels designed for elevated temperature service.Plates are available under this specification in several grades having different alloy contents.Each 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.The maximum thickness of plates is limited only by the capacity of the composition to meet the specified mechanical property requirements.
| Grades | UNS Designation |
|---|---|
| Grade 2 | S50460 |
| Grade 5 | S50200 |
| Grade 9 | K90941 |
| Grade 12 | K11757 |
| Grade 11 | K11789 |
| Grade 22 | K21590 |
| Grade 22L | |
| Grade 21 | K31545 |
| Grade 21L | |
| Grade 91 | K90901 |