There are many chromium molybdenum steel products available, each of which has very different chemical and mechanical properties, but they are often grouped as a single category. Chrome moly is the most common name for this group but other names that are used include chromalloy, croalloy, and Cr-Mo (pronounced “cro-mo”).
Typical applications will include:
Chrome Moly pressure vessel plates from Brown McFarlane are manufactured to the following steel standards:
Chrome Moly plates are available:
Both SA387 and A387 are described as a "Standard Specification for Pressure Vessel Plates, Alloy Steel, Chromium-Molybdenum". The specification covers alloy steel plates intended primarily for welded boilers and pressure vessels designed for elevated temperature use.
Plates are available under these specifications in several grades each having different nominal Chromium (Cr) and Molybdenum (Mo) contents as follows:
Each grade except Grades 21L, 22L, and 91 is available in two classes of tensile strength described as Class 1 and Class 2.
The most regularly specified grades and hence those that are most readily available from stock are Grades 12, 11, 22, 5, and 9 and in most case stock plates will be produced to the tensile requirements of Class 2.
Tensile Requirements - SA/A387 Grade 11 Class 2
Tensile Requirements - SA/A387 Grade 12 Class 2
Tensile Requirements - SA/A387 Grade 22 Class 2
The European steel standard which includes Chrome Moly plate for pressure vessel purposes is EN 10028-2. The full designation of the standard is "Flat products made of steels for pressure purposes - Part 2: Non-alloy and alloy steels with specified elevated temperature properties". This standard includes Chrome Moly material grades with varying quantities of chromium and molybdenum and some of these grades are broadly equivalent to those in the American standards ASME SA387 and ASTM A387.
Chemical Requirements (cast analysis, % by mass, maximum permitted unless indicated otherwise)