SS 347 Pipe & TubeASTM A312 TP347 · Manufacturer, stockist & exporter, India
Also sold as AISI 347 · UNS S34700 · W.Nr 1.4550 · Niobium-stabilised stainless
SS 347 pipe is supplied seamless to ASTM A312 TP347 and welded to ASTM A312 · A358, in ASME pipe sizes and schedules, with tube to ASTM A213. It is a niobium-stabilised austenitic stainless steel, chosen for welded high-temperature piping in refineries and power plants. Kanak Steel & Engineering Co. supplies it with EN 10204 3.1 mill certificates from Mumbai to buyers across India, the Gulf, South-East Asia, South America, Europe, the UK and the USA.
- Stock & mill supply
- EN 10204 3.1 / 3.2
- PMI on every heat
- Export packing
Reviewed by the Kanak Steel & Engineering Co. technical team · Updated October 2026
What is SS 347 Pipe & Tube?
SS 347 pipe & tube is a niobium-stabilised austenitic stainless steel supplied as pipe & tube to ASTM A312 TP347 (UNS S34700). Buyers specify it for welded high-temperature piping in refineries and power plants. It is also sold as AISI 347, UNS S34700, W.Nr 1.4550.
- What it is
- Niobium-stabilised austenitic stainless steel
- Seamless
- ASTM A312 TP347
- Welded
- ASTM A312 · A358
- Sizes
- NPS ⅛" – 24" · OD tube to order
- Schedules
- 5S · 10S · 40S · 80S · 160 · XXS
- Best at
- Welded high-temperature piping in refineries and power plants
SS 347 Pipe & Tube Specification & Sizes
| Seamless pipe | ASTM A312 TP347 |
|---|---|
| Welded pipe | ASTM A312 · A358 |
| Tube | ASTM A213 |
| Grade | SS 347 · UNS S34700 · S34709 (347H) · W.Nr 1.4550 |
| Size & schedule | NPS ⅛" to 24" to ASME B36.19 / B36.10; OD × wall for tube |
| Length | Single random, double random, or cut lengths |
| Ends | Plain end · bevelled end (for welding) · threaded |
| Testing | Hydrostatic or eddy-current · PMI · flattening & flaring · IGC on request |
| Documents | EN 10204 3.1 · 3.2 with third-party inspection |
Standards on this page
SS 347 Pipe: Seamless, Welded or Tube?
Three different specifications cover 347 tubular products. Pick the route first — it decides price, test requirements and lead time. General requirements (tolerances, hydrostatic or electric testing) come from ASTM A999. Schedules, the −12.5% wall tolerance and the B31.3 wall formula are explained in the pipe guide.
| Route | Specification | Use it for |
|---|---|---|
| Seamless pipe | ASTM A312 TP347 | Pressure and critical service; no weld seam to inspect. |
| Welded pipe | ASTM A312 · A358 | Economical in larger diameters and thinner walls where the code allows it. |
| Tube | ASTM A213 | Heat exchangers and instruments; ordered by exact OD × wall. |
SS 347 Pipe Wall & Weight by Schedule
For the same size, the schedule sets the wall — and the weight you pay for. Cross-sections are drawn to scale for 2" NPS (OD 60.33 mm, ASME B36.19); weights use the density of SS 347, 7.96 g/cm³.
Other sizes: pipe schedule chart and weight calculator.
SS 347 Pipe & Tube Chemical Composition
| Element | Weight % |
|---|---|
| Chromium | 17.0 – 19.0 |
| Nickel | 9.0 – 13.0 |
| Niobium | 10 × C min, 1.00 max |
| Carbon | 0.08 max |
| Manganese | 2.00 max |
| Silicon | 0.75 max |
| Phosphorus | 0.045 max |
| Sulphur | 0.030 max |
| Iron | Balance |
SS 347 Pipe & Tube Mechanical Properties
| Annealed plate & sheet | Value |
|---|---|
| Tensile strength | 515 MPa · 75 ksi |
| Yield strength 0.2% | 205 MPa · 30 ksi |
| Elongation | 40% |
| Hardness | 201 HB max |
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
Values follow ASTM A240 for UNS S34700. Always check against the edition named on your purchase order.
SS 347 Pipe Weight Chart (kg/m)
Weight per metre (kg/m) = (OD − WT) × WT × 0.02501, with OD and wall thickness in mm. The factor comes from SS 347's density of 7.96 g/cm³.
Example: 4" Sch 40S (114.30 × 6.02 mm)
(114.30 − 6.02) × 6.02 × 0.02501 = 16.30 kg/m
| NPS | OD mm | Sch 10S kg/m | Sch 40S kg/m |
|---|---|---|---|
| ½" | 21.34 | 1.01 | 1.29 |
| 1" | 33.40 | 2.12 | 2.54 |
| 2" | 60.33 | 3.99 | 5.52 |
| 3" | 88.90 | 6.55 | 11.45 |
| 4" | 114.30 | 8.49 | 16.30 |
| 6" | 168.28 | 14.02 | 28.66 |
| 8" | 219.08 | 20.25 | 43.14 |
Six-digit Harmonized System heading (iron and steel, chapter 72–73). Your country adds its own digits — confirm with your customs broker. All HS codes.
How to Verify SS 347 Pipe & Tube with PMI
Positive material identification with a handheld XRF gun confirms the alloy on the piece itself, in seconds, before it is cut or welded. SS 347 is most often mixed up with SS 321 — the table shows which elements tell them apart.
Handheld XRF does not measure carbon or nitrogen; those come from the mill certificate or optical emission (OES) testing. We PMI-test nickel alloys as standard and any grade on request.
| Element | SS 347 | SS 321 |
|---|---|---|
| Nickel | 9.0 – 13.0 | 9.0 – 12.0 |
| Chromium | 17.0 – 19.0 | 17.0 – 19.0 |
| Titanium | residual | 5 × (C + N) min, 0.70 max |
| Niobium | 10 × C min, 1.00 max | residual |
| Iron | Balance | Balance |
| Manganese | 2.00 max | 2.00 max |
SS 347 Pipe & Tube Price — What Decides It
Two quotes for "347 pipe & tube" can differ by 20% and both be fair. We quote 347 pipe & tube per kg for full sizes and per piece for cut sizes. These six things move the price per kg, so you can compare offers like for like.
Standards on this page
SS 347 Pipe & Tube Applications
SS 347 is specified when the cheaper grade will not survive the service but a higher alloy would be more than the job needs. These are the jobs our buyers use it for.
SS 347 Pipe & Tube vs 321, 304 and 310S
| Grade | Pipe & Tube standard | PREN (approx.) | Pick it when |
|---|---|---|---|
| SS 321 | ASTM A312 TP321 | ≈ 18 | High-temperature service between 425 and 815 °C |
| SS 304 | ASTM A312 TP304 | ≈ 18 | General corrosion resistance, food, water and architectural work |
| SS 347 | ASTM A312 TP347 | ≈ 18 | Welded high-temperature piping in refineries and power plants |
| SS 310 / 310S | ASTM A312 TP310S | ≈ 25 | Furnaces, burners and heat treatment at high temperature |
PREN = Cr + 3.3 Mo + 16 N, from mid-range chemistry. A screening guide, not a substitute for corrosion data on your medium.
SS 347 Corrosion Resistance — Element by Element
Each alloying addition has a job. Knowing which one protects against your medium is the quickest way to judge whether 347 fits.
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.
How your 347 pipe & tube order runs
- 01Enquiry review — we confirm size, standard edition and documents against your MR or drawing.
- 02Heat selection & PMI — the mill certificate is checked and material is PMI-tested before processing.
- 03Processing — cutting, machining or bevelling to your specification, with heat numbers marked.
- 04Inspection — your third-party inspector witnesses, or we share photos and test reports.
- 05Packing & dispatch — seaworthy packing from Nhava Sheva (JNPT), Mumbai, FOB or CIF, documents sent before the vessel sails.
Standards on this page
Welding & Fabricating SS 347 Pipe & Tube
SS 347 welds by all common arc processes. A few points our buyers ask about:
| Matching filler | ER347 (AWS A5.9) |
|---|---|
| Over-alloyed filler | ERNiCr-3 for dissimilar joints |
| Preheat | Not required; keep interpass temperature low |
| Cutting | Thermal or abrasive cutting; grind off heat-tinted edges before welding |
Follow your approved WPS; this is general guidance. See also 347 fittings and 347 flanges for the matching pipe-system parts.
How to Order SS 347 Pipe & Tube: RFQ Checklist
Get an accurate quote the first time. Copy this list into your enquiry:
- Seamless or welded, and the standard
- NPS and schedule (or OD × wall for tube)
- Length — random or cut, and number of lengths
- End finish — plain, bevelled or threaded
- Certificate type and extra tests
- Delivery port, Incoterm and required date
SS 347 pipe & tube for export
FOB / CIF · Nhava Sheva (JNPT), MumbaiSS 347 pipe & tube — questions buyers ask
Is SS 347 the same as AISI 347?
Yes. AISI 347, UNS S34700, W.Nr 1.4550 all refer to the same material, and pipe & tube is ordered to ASTM A312 TP347 whichever name is on the enquiry.
What is the difference between SS 347 pipe and tube?
Pipe is ordered by nominal pipe size and schedule, for carrying fluids. Tube is ordered by exact outside diameter and wall, for heat exchangers and instruments, and is held to tighter tolerances.
Seamless or welded SS 347 pipe — which should I buy?
Seamless (ASTM A312 TP347) is the default for pressure and critical service. Welded (ASTM A312 · A358) is cheaper in larger diameters and thinner walls and is accepted where the design code allows it.
What is the wall-thickness tolerance on SS 347 pipe?
Seamless pipe is normally allowed −12.5% on nominal wall under its general-requirements standard (ASTM A999). Allow for it in the pressure calculation or order on minimum wall.
Can SS 347 pipe be welded to carbon-steel pipe?
Yes, with the right filler: ER309L (or E309L electrode) is the usual filler when joining it to carbon steel. Follow a qualified WPS.
SS 347 or SS 310 / 310S — which should I choose?
SS 347 is chosen for welded high-temperature piping in refineries and power plants. SS 310 / 310S is the step up when you need more pitting resistance or strength. See the comparison table on this page, or ask us with your process conditions.
Sources: the ASTM / ASME specifications named on this page and producer datasheets · Last updated October 2026