Stainless 347 (UNS S34700)
Stainless 347 (UNS S34700) — Niobium-stabilised for high-temperature service.
| UNS number | S34700 |
| Material family | Austenitic stainless |
| Product specifications | A182 F347, A403 WP347, A312 TP347 |
| Density (typical) | 7.93 g/cm³ (7930 kg/m³) |
| Weight of 6" Sch 40 pipe | 28.55 kg/m |
Specifications by product form
One alloy is ordered under different ASTM/ASME numbers depending on form: forged flanges and fittings, wrought buttweld fittings, and pipe or tube. For Stainless 347 the usual specifications are A182 F347, A403 WP347, A312 TP347. Quote both the specification and the UNS number on purchase orders to avoid ambiguity.
Chemical and mechanical limits differ between these specifications — always check the edition of the standard named on your order and the mill test certificate.
Chemical composition & mechanical properties
| Property | SS 347 |
|---|---|
| Family | Austenitic stainless |
| UNS | S34700 |
| EN / W.Nr | 1.4550 X6CrNiNb18-10 |
| Basis spec | ASTM A240 |
| Density g/cm³ | 7.93 |
| Chemical composition, % | |
| C | 0.08 |
| Mn | 2.00 |
| P | 0.045 |
| S | 0.030 |
| Si | 0.75 |
| Cr | 17.0–19.0 |
| Ni | 9.0–13.0 |
| Nb | 10×C–1.00 |
| Mechanical properties (min) | |
| Tensile strength | 515 MPa (75 ksi) |
| Yield strength (0.2%) | 205 MPa (30 ksi) |
| Elongation | 40% |
| Hardness (max) | 201 HB |
| PREN (min, from spec) | 17.0 |
Single values are maximums; ranges are min–max; "bal" = balance. Limits are typical of the basis specification for that product form — forgings, pipe and fittings specifications differ slightly. Always check the exact specification, edition and the mill test certificate.
Frequently asked questions
What is the UNS number of Stainless 347?
S34700.
Which ASTM specifications cover Stainless 347?
A182 F347, A403 WP347, A312 TP347.
What is the density of Stainless 347?
About 7.93 g/cm³ (7930 kg/m³), used for weight calculations.
Last updated 2026-11-02