Stainless 347 · UNS S34700 · W. Nr. 1.4550
Stainless 347 (S34700): composition, properties, fittings and flanges
Stainless 347 (S34700, W. Nr. 1.4550) is Niobium-stabilised austenitic stainless steel. Stainless 347 is specified at Chromium 17.00 - 19.00, Nickel 9.00 - 13.00, Niobium + Tantalum 10 x C min to 1.00 max. 347 uses niobium rather than titanium for stabilisation, which survives welding and high-temperature exposure better and…
- UNS
- S34700
- W. Nr.
- 1.4550
- Density
- 8.00 g/cm³ (0.289 lb/in³)
- Key strength
- 515 MPa / 75 ksi
Identification and standards
| Short form | Stainless 347 · UNS S34700 · W. Nr. 1.4550 |
|---|---|
| Classification | Niobium-stabilised austenitic stainless steel |
| UNS | S34700 |
| Werkstoff number | 1.4550 |
| Material family | Stainless Steel |
Chemical composition
| Element | Composition (wt %) | Why it is there |
|---|---|---|
| Chromium (Cr) | 17.00 - 19.00 | Passive film and oxidation resistance |
| Nickel (Ni) | 9.00 - 13.00 | Austenite stability |
| Niobium + Tantalum | 10 x C min to 1.00 max | Carbon stabilisation |
| Carbon (C) | 0.08 max | - |
| Manganese (Mn) | 2.00 max | - |
| Silicon (Si) | 0.75 max | - |
| Phosphorus (P) | 0.045 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 |
| Useful continuous service temperature | About 815 °C |
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 - 1455 °C (2550 - 2650 °F) |
| Modulus of elasticity | 193 GPa (28.0 x 10⁶ psi) |
| Thermal conductivity at 20 °C | 16.1 W/m·K |
| Mean coefficient of thermal expansion, 20-100 °C | 16.6 µm/m·°C |
| Specific heat capacity | 500 J/kg·K |
Specifications by product form
| Forgings & flanges | ASTM A182 F347 · ASME SA-182 |
|---|---|
| Butt weld fittings | ASTM A403 WP347 · ASME SA-403 |
| Seamless pipe & tube | ASTM A312 TP347 · ASME SA-312 |
| Plate / sheet / strip | ASTM A240 347 · ASME SA-240 |
| Bar / rod | ASTM A276 / A479 |
| Welding consumables | ER347 |
| UNS / EN / China | UNS S34700 · W. Nr. 1.4550 · GB 06Cr18Ni11Nb |
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
- Refinery heater, reformer and coker piping
- Power plant superheater and reheater tubing
- Heavy welded vessels that cannot be solution annealed
- Aircraft and exhaust components in the sensitising range
Welding, forming and machining
- Welding
- Weld with ER347 filler. Niobium stabilisation survives the weld thermal cycle better than titanium, giving reliable as-welded intergranular corrosion resistance.
- Heat treatment
- Stabilise at 870 - 900 °C, or solution anneal at 950 - 1120 °C 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 347 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.