SS 347 — Sheet, Plate, Coil, Pipe & Tube & Fittings
Also sold as AISI 347 · UNS S34700 · W.Nr 1.4550 · Niobium-stabilised stainless
SS 347 is a niobium-stabilised austenitic stainless steel, chosen for welded high-temperature piping in refineries and power plants. We supply it as sheet, plate, coil, pipe & tube, fittings, flanges, fasteners, with EN 10204 3.1 certificates, from Mumbai to India, the Gulf, South-East Asia, South America, Europe, the UK and the USA.
- UNS S34700
- W.Nr 1.4550
- PREN ≈ 18
- ρ 7.96 g/cm³
Reviewed by the Kanak Steel & Engineering Co. technical team · Updated October 2026
SS 347 Names, Designations & Composition
SS 347 is one alloy sold under several names. Its UNS number is S34700, the European material number is W.Nr 1.4550 and the EN name is X6CrNiNb18-10. The chart on the right shows the specified range of each main alloying element; the balance is the base metal.
SS 347 Specifications by Product — Which Standard Applies?
The material standard changes with the product form. This is the table buyers ask for most.
| Product | Material standard | Dimensions |
|---|---|---|
| SS 347 sheet | ASTM A240 | ASTM A480 / B906 |
| SS 347 plate | ASTM A240 | ASTM A480 / B906 / A20 |
| SS 347 coil | ASTM A240 | ASTM A480 |
| SS 347 pipe & tube | ASTM A312 TP347 · ASTM A312 · A358 | ASME B36.19 / B36.10 |
| SS 347 fittings | ASTM A403 WP347 · ASTM A182 F347 | ASME B16.9 · B16.11 |
| SS 347 flanges | ASTM A182 F347 | ASME B16.5 · B16.47 |
| SS 347 fasteners | ASTM A193 B8C | ASME B18.2.1 · B18.2.2 |
SS 347 Chemical Composition
Under technical review for TDS.
| Element | Current requirement |
|---|---|
| Chromium | As specified |
| Nickel | As specified |
| Niobium | As specified |
| Carbon | As specified |
| Manganese | As specified |
| Silicon | As specified |
| Phosphorus | As specified |
| Sulphur | As specified |
| Iron | As specified |
Numerical specification requirements are published only after the applicable current standard edition has been verified. Governing specification to be verified: ASTM A240 for UNS S34700.
SS 347 Mechanical Properties
Under technical review for TDS.
| Property | Current requirement |
|---|---|
| Tensile strength | As specified |
| Yield strength 0.2% | As specified |
| Elongation | As specified |
| Hardness | As specified |
Numerical specification requirements are published only after the applicable current standard edition has been verified. Governing specification and condition to be verified: ASTM A240 for UNS S34700 — Annealed plate & sheet.
Density & Physical Properties
| Property | Value |
|---|---|
| Density | 7.96 g/cm³ |
| Melting range | 1400 – 1425 °C |
| Magnetic | Non-magnetic annealed |
| PREN (approx.) | ≈ 18 |
SS 347 Equivalent Grades
SS 347 Corrosion Resistance — What Each Element Does
About 18% chromium forms the passive film that makes the steel stainless.
Nickel keeps the structure austenitic — tough at low temperature and easy to form and weld.
Niobium binds carbon more stably than titanium, so 347 holds up in welded high-temperature service.
347H is the choice for hot hydrogen and high-temperature refinery piping.
SS 347 vs 321, 304 and 310S
| Grade | PREN (approx.) | Pick it for |
|---|---|---|
| SS 321 | ≈ 18 | High-temperature service between 425 and 815 °C |
| SS 304 | ≈ 18 | General corrosion resistance, food, water and architectural work |
| SS 347 | ≈ 18 | Welded high-temperature piping in refineries and power plants |
| SS 310 / 310S | ≈ 25 | Furnaces, burners and heat treatment at high temperature |
Welding SS 347
| Matching filler | ER347 (AWS A5.9) |
|---|---|
| Also used | ERNiCr-3 for dissimilar joints |
SS 347 for export
FOB / CIF · Nhava Sheva (JNPT), MumbaiSS 347 — questions buyers ask
What is SS 347?
SS 347 is a niobium-stabilised austenitic stainless steel. It is chosen for welded high-temperature piping in refineries and power plants.
Which standards cover SS 347 products?
Sheet: ASTM A240; Plate: ASTM A240; Coil: ASTM A240; Pipe & Tube: ASTM A312 TP347 · ASTM A312 · A358; Fittings: ASTM A403 WP347 · ASTM A182 F347; Flanges: ASTM A182 F347; Fasteners: ASTM A193 B8C. Always name the standard and edition on your order.
What is the UNS number of SS 347?
UNS S34700 · S34709 (347H), with the European material number W.Nr 1.4550.
What is the density of SS 347?
7.96 g/cm³ — use it to calculate weights: plate kg = L(m) × W(m) × t(mm) × 7.96.
SS 347 or SS 310 / 310S?
SS 347 suits welded high-temperature piping in refineries and power plants; SS 310 / 310S is the step up for furnaces, burners and heat treatment at high temperature.
Sources: the ASTM / ASME specifications named on this page and producer datasheets · Last updated October 2026