Grade Position and Scope of Use
14Cr1MoR belongs to the family of chromium-molybdenum steel plates for pressure vessels and corresponds to the ASME SA387 Gr11 Cl2 grade. The chemistry is built around roughly one and a quarter percent chromium with molybdenum in the 0.45 to 0.65 percent band, a combination that gives the steel its defining characteristics: strength retained at elevated temperature, resistance to hydrogen attack and hydrogen mixed media, and adequate toughness for thick-wall vessel construction.
The grade is selected where carbon and manganese vessel steels would be overmatched by the service. Petrochemical reactors, hydrocrackers and heat exchangers, nuclear power components, steam turbine cylinders and thermal power equipment all appear on the reference list of applications, and the material is routinely produced in heavy plate for thick-wall equipment.
Governing Standard and Delivery Condition
Plates are manufactured to GB/T 713.2-2023, the part of the pressure equipment plate standard that covers non-alloy and alloy steels with specified temperature properties. The specification controls grade designation, ordering content, dimensions, shape and mass, technical requirements, test methods, inspection rules, packaging, marking and quality certificate content, and it is the document against which chemistry and mechanical values are verified.
The plate is normally delivered in the normalised plus tempered condition, or in a cooled and tempered condition for heavier thicknesses, so that the microstructure is stable enough for welding and for elevated temperature service. Additional requirements such as simulated post-weld heat treatment of test pieces, restricted residual elements or ultrasonic testing to a defined acceptance class are agreed at the ordering stage.
Chemical Composition
| Element | Content (%) |
|---|---|
| Carbon | 0.17 maximum |
| Silicon | 0.50 to 0.80 |
| Manganese | 0.40 to 0.65 |
| Chromium | 1.15 to 1.50 |
| Molybdenum | 0.45 to 0.65 |
| Copper | 0.30 maximum |
| Nickel | 0.30 maximum |
| Phosphorus | 0.020 maximum |
| Sulphur | 0.010 maximum |
Carbon is capped at 0.17 percent to keep the steel weldable and to limit hardening in the heat affected zone, while silicon, manganese and the chromium-molybdenum pair provide the strength and the carbide stability that elevated temperature service demands. Copper and nickel are held low because they are not needed for the application; phosphorus and sulphur are restricted so that toughness in heavy sections is not compromised.
Mechanical Properties
| Property | Thickness range | Requirement |
|---|---|---|
| Tensile strength | 6 to 100 mm | 520 to 680 MPa |
| Tensile strength | over 100 to 200 mm | 510 to 670 MPa |
| Yield strength | up to 100 mm | 310 MPa minimum |
| Yield strength | over 100 to 200 mm | 300 MPa minimum |
| Charpy V-notch impact energy | all sizes | 47 J minimum at 20 degrees Celsius |
| Bend test | all sizes | 180 degrees, test piece width 2a, mandrel diameter D = 3a |
Note that the tensile window steps down slightly for plate thicker than 100 mm, which reflects the lower degree of deformation and the slower cooling of heavy plate. Fabricators should confirm the property band against the actual ordered thickness when calculating allowable stresses.
Fabrication and Quality Control
Forming: hot forming followed by a restoring heat treatment is preferred for thick plate; cold forming limits should be agreed if used.
Welding: matched Cr-Mo consumables, controlled preheat and interpass temperature, and post-weld heat treatment for thick joints and restrained assemblies.
Inspection: ultrasonic testing sheet by sheet to JB/T 4730.3 or GB/T 2970 where specified, with the acceptance class declared in the order.
Testing: tensile, impact and bend tests taken in the delivery condition, with optional simulated post-weld heat treatment.
Traceability: heat number, heat treatment record and quality certificate supplied with the plate to GB/T 247.
Frequently Asked Questions
Q: What grade does 14Cr1MoR correspond to internationally?
A: It corresponds to the ASME SA387 Gr11 Cl2 chromium-molybdenum steel plate for welded pressure vessels.
Q: What is the chromium range of 14Cr1MoR?
A: Chromium is specified from 1.15 to 1.50 percent, with molybdenum from 0.45 to 0.65 percent.
Q: What is the tensile strength of 14Cr1MoR plate?
A: 520 to 680 MPa for plate from 6 mm to 100 mm thick, and 510 to 670 MPa for plate over 100 mm up to 200 mm.
Q: What impact requirement applies?
A: Charpy V-notch impact energy of at least 47 J at 20 degrees Celsius, tested in the delivery condition.
Q: Why is the grade used for hydrogen service?
A: The stable chromium and molybdenum carbides resist hydrogen attack and hydrogen mixed media at elevated temperature, which is the reason for specifying a Cr-Mo vessel steel.
