This specification covers carbonsilicon steel plates, in two intermediate tensile strength ranges designated grades A and B, intended particularly for fusion welding; for use in locomotive boiler shells, boilers for sfationary service and other pressure vessels. The maximum thickness of flange quality plates to be specified under this specification shall be 2 in.; of firebox quality plates of grade A shall be 12 in.; and of grade B shall be 8 in. Welding technique is of fundamental importance and it is presupposed that welding procedure will be in accordance with approved methods.