Stainless Steel 310H
Stainless Steel 310H (UNS S31009) is the high-carbon variant of Grade 310, with carbon controlled between 0.04% and 0.10%. This tighter carbon range maximizes creep rupture strength and elevated-temperature tensile properties. It is the designated grade for long-term service above 650°C under sustained mechanical load.
1. Chemical Composition
The table below shows the elemental limits for Stainless Steel 310H. The mandated carbon range is what drives its higher creep and stress-rupture performance at elevated temperatures.
| GRADE | UNS Designation |
C | Mn | P | S | Si | Cr | Ni | Mo | Ti | Cu | Al | Other |
| TP310H | S31009 | 0.04-0.1 | 2.00 | 0.045 | 0.030 | 1.00 | 24.0-26.0 | 19.0-22.0 | - | - | - | - | - |
2. Mechanical Properties
The table below lists minimum ambient-temperature mechanical properties for Stainless Steel 310H in the annealed condition. Elevated-temperature stress-rupture values are found in ASME Section II Part D tables.
| Grade | Condition & Size | Standard | Heat Treating Temp. : min | Tensile Strength Min. MPa |
Yield Strength Min. MPa |
Elongation min. % |
| TP310H | - | A312 | 1040°C | 515 | 205 | 35 |
3. Equivalent Grade
This table cross-references Stainless Steel 310H with its international equivalents across major standards systems. It is useful for verifying specification compliance in global procurement.
| GRADE | UNS | GB | JIS | ISO | DIN/EN | GOST | |
| ISC | NEW | ||||||
| 310H | S31009 | — | 20Cr25Ni20H | SUS310 (H) | X15CrNi25-21H | 1.4841 (H) | 20X25H20C2 |
4. Key Technical Advantages
- Superior Creep Rupture Strength: The minimum 0.04% carbon floor provides solid solution and carbide precipitation strengthening that raises stress-rupture life well above 310S (the low-carbon variant), particularly above 700°C.
- ASME High-Temperature Code Qualification: 310H is listed in ASME Section I and Section VIII Division 1 allowable stress tables at temperatures up to 900°C. 310S is not listed at these levels because it lacks the required creep strength.
- Long-Term Microstructural Stability: The controlled carbon chemistry supports a more stable elevated-temperature microstructure by promoting M23C6 carbide dispersion, which slows dislocation movement under creep conditions.
- Oxidation Resistance Equivalence: Despite its higher carbon, 310H has the same high-temperature oxidation resistance as 310 because the chromium and nickel levels are identical. The carbon difference affects mechanical behavior under load, not surface corrosion.
Technical Note: 310H should not be selected for applications requiring inter-granular corrosion resistance in corrosive liquid media, as the higher carbon content increases sensitization risk in the weld heat-affected zone.
5. Common Manufacturing Standards
Stainless Steel 310H is produced and qualified under the following manufacturing standards:
ASTM A213: Standard Specification for Seamless Ferritic and Austenitic Alloy-Steel Boiler, Superheater, and Heat-Exchanger Tubes — T310H designation, listed with elevated-temperature allowables.
ASTM A312: Standard Specification for Seamless, Welded, and Heavily Cold Worked Austenitic Stainless Steel Pipes — TP310H designation.
ASTM A249: Standard Specification for Welded Austenitic Steel Boiler, Superheater, Heat-Exchanger, and Condenser Tubes.
ASTM A358: Standard Specification for Electric-Fusion-Welded Austenitic Chromium-Nickel Stainless Steel Pipe for High-Temperature Service.
DIN EN 10095: Heat-resisting steels and nickel alloys (1.4841 — Si-alloyed variant with similar thermal capability).
GB/T 13296: Seamless stainless steel tubes for boiler and heat exchanger (10Cr25Ni20).
GOST 5632: High-alloy steels and alloys — compositional equivalent reference.
Standards Comparison Table:
| Standard | ASTM | EN/DIN | JIS | GB/T | GOST |
| Seamless Boiler Tube | A213 (T310H) | EN 10216-5* (no separate EN H-variant designation) | - | 13296 | 5632 |
| Seamless Pipe | A312 (TP310H) | EN 10095 | - | 13296 | - |
| Welded Pipe | A312 (TP310H) | EN 10217-7 | - | - | - |
| Welded Boiler Tube | A249 | EN 10217-7 | - | - | - |
6. Primary Applications
- Superheater and Reheater Tubes: High-temperature boiler circuits in power stations where metal temperatures exceed 700°C and long-term creep life determines tube wall thickness design.
- Steam Reformer Furnace Headers: Inlet and outlet manifolds in hydrogen production and ammonia synthesis reformers that operate at extreme thermal gradients and high process pressures.
- Ethylene Pyrolysis Coils: Radiant section coil hangers and supports in ethylene cracking furnaces where carburizing atmospheres and sustained mechanical stress are both present.
- Hydrocarbon Reforming Reactors: Catalyst tube supports and high-temperature piping in catalytic reforming units where creep strength at operating temperature determines design life.
- Aerospace Ground Test Facilities: High-temperature flow duct components and combustion test rigs where oxidation resistance and creep strength must both be maintained.