What is 1.4961 Stainless Steel?
Jan 14, 2026
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1.4961 stainless steel, commonly known as 347H or UNS S34709, is the high-carbon, niobium-stabilized variant of the 347 austenitic stainless steel. The "H" designation signifies its enhanced high-temperature strength and creep resistance due to controlled higher carbon content, making it ideal for prolonged service in high-temperature environments such as superheaters, heat exchangers, and pressure vessels in power generation and petrochemical industries.
This high-temperature stabilized grade is standardized under key international systems.
| Standard | Equivalent Grade |
|---|---|
| EN (Europe) | 1.4961 |
| ASTM/AISI (USA) | 347H, UNS S34709 |
| JIS (Japan) | SUS347H |
| KS (Korea) | STS347H |
Niobium (Nb) stabilization and controlled carbon content are key to its performance.
| Element | C | Si | Mn | P | S | Cr | Ni | Nb |
|---|---|---|---|---|---|---|---|---|
| Content (%) | 0.04 - 0.10 | ≤ 0.75 | ≤ 2.0 | ≤ 0.045 | ≤ 0.03 | 17.0 - 19.0 | 9.0 - 13.0 | 8xC min |
It offers robust mechanical properties suitable for high-temperature structural applications.
| Property (Room Temp) | Yield Strength (Rp0.2) | Tensile Strength (Rm) | Elongation (A) | Hardness (HB) |
|---|---|---|---|---|
| Typical Value | ≥ 205 MPa | 500 - 750 MPa | ≥ 40% | ≤ 215 |
Key Characteristics and Applications of 1.4961 / 347H
Excellent High-Temperature Creep Strength: The combination of niobium stabilization and controlled carbon content provides superior creep and stress rupture resistance at temperatures above 500°C, outperforming standard 347.
Resistance to Sensitization: Niobium forms stable carbides, preventing chromium depletion at grain boundaries and ensuring resistance to intergranular corrosion in the sensitization temperature range (450–850°C).
Good Oxidation Resistance: Maintains resistance to scaling and oxidation in continuous service up to about 900°C.
Primary Applications:
Power Generation: Superheater and reheater tubing, boiler components, and high-temperature headers.
Petrochemical: Catalytic converter shells, reformer tubes, and high-temperature process piping.
Heat Exchangers: Tubing and plates in high-temperature, high-pressure service.
Aerospace: High-temperature engine and exhaust components.
How does 347H (1.4961) differ from standard 347 (1.4550)?
The primary difference is the carbon content specification. 347H has a controlled carbon range of 0.04–0.10%, ensuring higher minimum carbon to guarantee enhanced creep strength at elevated temperatures. Standard 347 has a maximum carbon limit of 0.08% with no minimum requirement. 347H is therefore specified in ASME and other pressure vessel codes for high-temperature structural applications where long-term creep resistance is critical.
Why is niobium (Nb) used as a stabilizer in 347H instead of titanium?
Niobium provides more stable carbides than titanium at high temperatures, which is crucial for maintaining strength and preventing sensitization over prolonged service. Niobium carbides are less likely to dissolve or oxidize during welding or high-temperature exposure, making 347H particularly suitable for heavy welded sections and components subjected to cyclic heating and cooling.
Looking for a Reliable Supplier of 1.4961 / 347H Stainless Steel?
GNEE Steel supplies high-temperature grade 347H (1.4961) stainless steel in tubular, plate, and bar forms, designed for demanding power, petrochemical, and aerospace applications. We provide full material traceability and certification to relevant standards. If you have any requirements, please feel free to contact us.
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