Stainless 304H · UNS S30409 · W. Nr. 1.4948
Stainless 304H (S30409): composition, properties, fittings and flanges
Stainless 304H (S30409, W. Nr. 1.4948) is High-carbon austenitic stainless steel for elevated temperature. Stainless 304H is specified at Chromium 18.0 - 20.0, Nickel 8.0 - 10.5. 304H carries a minimum carbon of 0.04 % so that it keeps creep and rupture strength at 500 - 800 °C, which is why ASME B31.3 pressure piping at…
- UNS
- S30409
- W. Nr.
- 1.4948
- Density
- 8.00 g/cm³ (0.289 lb/in³)
- Key strength
- 515 MPa / 75 ksi
Identification and standards
| Short form | Stainless 304H · UNS S30409 · W. Nr. 1.4948 |
|---|---|
| Classification | High-carbon austenitic stainless steel for elevated temperature |
| UNS | S30409 |
| Werkstoff number | 1.4948 |
| Material family | Stainless Steel |
Chemical composition
| Element | Composition (wt %) | Why it is there |
|---|---|---|
| Chromium (Cr) | 18.0 - 20.0 | Oxidation resistance |
| Nickel (Ni) | 8.0 - 10.5 | Austenite stability |
| Carbon (C) | 0.04 - 0.10 | Creep and rupture strength above 500 °C |
| Manganese (Mn) | 2.00 max | - |
| Silicon (Si) | 0.75 max | - |
| Phosphorus (P) | 0.045 max | - |
| Sulphur (S) | 0.030 max | - |
| Iron (Fe) | Balance | Matrix |
Note Single figures are maximum limits unless shown as a range. Always confirm against the heat-specific EN 10204 3.1 certificate supplied with your order.
Mechanical properties
| Tensile strength, min (annealed) | 515 MPa / 75 ksi |
|---|---|
| 0.2 % yield strength, min | 205 MPa / 30 ksi |
| Elongation in 2 in, min | 40 % |
| Typical hardness, annealed | 145 - 190 HB |
| ASME B31.3 coverage | Elevated temperature design allowed |
Warning Values depend on product form, section thickness and heat treatment. Larger sections generally achieve lower strength than thin product; always design against the applicable code allowable stress rather than these figures.
Physical properties
| Density | 8.00 g/cm³ (0.289 lb/in³) |
|---|---|
| Melting range | 1400 - 1450 °C (2550 - 2640 °F) |
| Modulus of elasticity | 193 GPa (28.0 x 10⁶ psi) |
| Thermal conductivity at 20 °C | 16.2 W/m·K |
| Mean coefficient of thermal expansion, 20-100 °C | 17.3 µm/m·°C |
| Specific heat capacity | 500 J/kg·K |
Specifications by product form
| Forgings & flanges | ASTM A182 F304H · ASME SA-182 |
|---|---|
| Butt weld fittings | ASTM A403 WP304H · ASME SA-403 |
| Seamless pipe & tube | ASTM A312 TP304H · ASME SA-312 |
| Plate / sheet / strip | ASTM A240 304H · ASME SA-240 |
| Bar / rod | ASTM A276 / A479 |
| Welding consumables | ER308H |
| UNS / EN / China | UNS S30409 · W. Nr. 1.4948 · GB 07Cr19Ni10 |
Product forms available
Hangbo supplies this grade in the following forms. Sizes outside the listed range can often be produced to order.
- Forged flanges blanks and finished flanges to ASME B16.5, B16.47 Series A/B and B16.36
- Butt weld elbows, tees, reducers, caps and stub ends to ASME B16.9 and MSS SP-43
- Seamless pipe and tube to the applicable ASTM / ASME pipe specification
- Forged rings, discs and hubs machined to your drawing
Typical applications
- Superheater and reheater steam piping
- Refinery and petrochemical high-temperature process lines
- Boiler, pressure vessel and heat exchanger service above 500 °C
- Flare and exhaust ducting at elevated temperature
Welding, forming and machining
- Welding
- Weld with ER308H filler to keep the carbon level in the weld metal. Post-weld solution annealing restores corrosion resistance but is rarely needed for dry high-temperature service.
- Heat treatment
- Solution anneal at 1040 °C minimum and water quench.
- Hot and cold forming
- Hot work in the range stated by the mill for this grade, then re-solution or re-age before final machining so that the delivered condition matches the certificate.
- Machining
- Machine with sharp carbide or high-speed steel tooling, positive rake, constant feed and ample coolant. Never dwell - the surface work-hardens quickly.
Buy Stainless 304H from Hangbo
Material is supplied with full heat-number traceability, solution annealing or ageing performed under calibrated furnace control, and an EN 10204 3.1 certificate covering chemical analysis, mechanical properties, heat treatment records and the agreed NDT scope. Positive material identification and third party inspection and test reports from SGS are available for critical service.