What Is 15CrMoR Steel?
15CrMoR is a chromium-molybdenum steel plate for boilers and pressure vessels, specified in GB/T 713. The designation breaks down as follows: 15 indicates a nominal carbon content of about 0.15%, Cr and Mo identify the chromium and molybdenum alloying elements, and R denotes pressure vessel steel (Rongqi). The chromium and molybdenum additions give the grade medium-temperature strength, creep resistance and resistance to hydrogen attack, which is why 15CrMoR is a standard material for high-pressure boilers, pressure vessels and chemical equipment operating at elevated temperature.
Chemical Composition
Composition limits (wt%):
| Element | Limit (%) |
|---|---|
| Carbon | 0.12–0.18 |
| Silicon | 0.15–0.40 |
| Manganese | 0.40–0.70 |
| Phosphorus, max | 0.025 |
| Sulfur, max | 0.010 |
| Chromium | 0.80–1.20 |
| Molybdenum | 0.30–0.60 |
The very low sulfur limit is a characteristic of the modern editions of the standard and is required to secure the toughness and weldability of the Cr-Mo steel in thick sections.
Mechanical Properties in the Normalized and Tempered Condition
Minimum mechanical values by thickness:
| Thickness (mm) | Tensile (MPa) | Yield (MPa) | Elongation (%) |
|---|---|---|---|
| 6–60 | 450–590 | ≥295 | ≥19 |
| 60–100 | 450–590 | ≥275 | ≥19 |
| 100–150 | 440–580 | ≥255 | ≥19 |
Impact testing is carried out at 20 °C with a minimum average energy of 31 J, and the cold bending test (180°, d = 3a) applies as specified in the standard.
Heat Treatment and Delivery Condition
15CrMoR is delivered in the normalized and tempered condition. Normalizing refines the grain structure, and tempering relieves transformation stress and stabilises the tempered martensite or bainite microstructure that provides the service properties at elevated temperature. The delivery condition is part of the specification and must be stated on the mill test certificate together with the heat analysis and test results.
Typical Applications
The grade is used for high-pressure boilers, pressure vessels and chemical equipment where the service temperature is too high for carbon-manganese steels but below the range of higher-alloy Cr-Mo grades. Typical components include boiler drums, reactors, heat exchangers and storage equipment in power generation, petrochemical and chemical plants, where its medium-temperature strength and hydrogen resistance are the deciding factors.
Frequently Asked Questions
What does 15CrMoR mean?
15 is the nominal carbon content in hundredths of a percent (about 0.15%), Cr and Mo are the alloying elements chromium and molybdenum, and R denotes pressure vessel steel in the GB/T 713 system.
Which standard covers 15CrMoR?
The grade is covered by GB/T 713, the Chinese standard for steel plates for boilers and pressure vessels; the current edition is GB/T 713-2023.
Why is 15CrMoR used for hydrogen service?
The chromium and molybdenum additions improve resistance to hydrogen attack and creep at medium temperature, which makes the grade suitable for hydrogen-bearing process equipment.
Do the mechanical properties change with thickness?
Yes. Yield strength decreases with thickness, from 295 MPa in the 6–60 mm tier to 275 MPa for 60–100 mm and 255 MPa for 100–150 mm, with tensile values also reduced in the thickest tier.
Is 15CrMoR weldable?
Yes, with qualified procedures. The carbon equivalent of the grade requires low-hydrogen practice and, for thicker plates, preheat; post-weld heat treatment is typically applied in code work to restore toughness in the heat-affected zone.
What is the difference between 15CrMoR and 12Cr2Mo1R?
15CrMoR has a nominal 1% chromium and 0.5% molybdenum level, while 12Cr2Mo1R is the 2.25Cr–1Mo grade with significantly higher elevated-temperature strength, used for more severe hydrogen and creep service.
