SS 347 Pipe FittingsASTM A403 WP347 · Manufacturer, stockist & exporter, India
Also sold as AISI 347 · UNS S34700 · W.Nr 1.4550 · Niobium-stabilised stainless
SS 347 pipe fittings are made to ASTM A403 WP347 for buttweld fittings and ASTM A182 F347 for forged socket-weld and threaded fittings, with dimensions to ASME B16.9 and B16.11. 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 Fittings?
SS 347 pipe fittings is a niobium-stabilised austenitic stainless steel supplied as pipe fittings to ASTM A403 WP347 (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
- Buttweld
- ASTM A403 WP347
- Forged
- ASTM A182 F347
- Dimensions
- ASME B16.9 · B16.11 · MSS SP-43
- Sizes
- Buttweld ½" – 48" · forged ⅛" – 4"
- Best at
- Welded high-temperature piping in refineries and power plants
SS 347 Pipe Fittings Specification & Sizes
| Buttweld fittings | ASTM A403 WP347 — dimensions to ASME B16.9, MSS SP-43 |
|---|---|
| Forged fittings | ASTM A182 F347 — dimensions to ASME B16.11 |
| MSS SP-43 light-wall fittings | ASTM A403 CR347 — the A403 CR grade for MSS SP-43 dimensions (no class suffix) |
| Short-radius elbows | ASME B16.9 (formerly B16.28) |
| Buttweld sizes | NPS ½" to 48", schedule to match the pipe |
| Forged classes | Socket weld 3000 / 6000 / 9000 · threaded 2000 / 3000 / 6000 |
| Types | Elbow · Tee · Reducer · Cap · Stub end · Cross · Bend · Lateral · Coupling · Union · Nipple · Plug |
| Testing | PMI · dimensional · radiography of welded fittings · IGC on request |
| Documents | EN 10204 3.1 · 3.2 with third-party inspection |
Standards on this page
Choosing SS 347 Fittings: Elbow Radius, Schedule & Class
ASTM A403 fittings come in classes: S seamless, W welded (welds made by the fitting maker radiographed), WX all welds radiographed, WU all welds ultrasonically tested. Write the class after the grade, e.g. WP347-S.
Radius (LR, SR, 3D), the schedule-to-class map and the 1.5 mm socket-weld gap are explained in the fittings guide. For 347, buttweld fittings are ASTM A403 WP347 and forged fittings ASTM A182 F347.
SS 347 Pipe Fittings 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 Fittings 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 buttweld fitting dimensions — ASME B16.9
Centre-to-end and end-to-end dimensions are the same for every alloy; the wall thickness follows the pipe schedule. Values in mm.
| NPS | OD | 90° LR elbow A | 45° elbow B | Tee C | Reducer H | Cap E |
|---|---|---|---|---|---|---|
| ½" | 21.3 | 38 | 16 | 25 | — | 25 |
| 1" | 33.4 | 38 | 22 | 38 | 51 | 38 |
| 1½" | 48.3 | 57 | 29 | 57 | 64 | 38 |
| 2" | 60.3 | 76 | 35 | 64 | 76 | 38 |
| 3" | 88.9 | 114 | 51 | 86 | 89 | 51 |
| 4" | 114.3 | 152 | 64 | 105 | 102 | 64 |
| 6" | 168.3 | 229 | 95 | 143 | 140 | 89 |
| 8" | 219.1 | 305 | 127 | 178 | 152 | 102 |
| 10" | 273.1 | 381 | 159 | 216 | 178 | 127 |
| 12" | 323.9 | 457 | 190 | 254 | 203 | 152 |
Full chart to 24": ASME B16.9 fitting dimensions.
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 Fittings 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 Fittings Price — What Decides It
Two quotes for "347 pipe fittings" can differ by 20% and both be fair. We quote 347 pipe fittings 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.
SS 347 pipe fittings by type
SS 347 Pipe Fittings 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 Fittings vs 321, 304 and 310S
| Grade | Pipe Fittings standard | PREN (approx.) | Pick it when |
|---|---|---|---|
| SS 321 | ASTM A403 WP321 | ≈ 18 | High-temperature service between 425 and 815 °C |
| SS 304 | ASTM A403 WP304 | ≈ 18 | General corrosion resistance, food, water and architectural work |
| SS 347 | ASTM A403 WP347 | ≈ 18 | Welded high-temperature piping in refineries and power plants |
| SS 310 / 310S | ASTM A403 WP310S | ≈ 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 fittings 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 Fittings
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 Fittings: RFQ Checklist
Get an accurate quote the first time. Copy this list into your enquiry:
- Fitting type, size and schedule / class
- Buttweld, socket weld or threaded
- Seamless or welded (buttweld fittings)
- Material standard and grade marking
- Certificate type and extra tests
- Delivery port, Incoterm and required date
SS 347 pipe fittings for export
FOB / CIF · Nhava Sheva (JNPT), MumbaiSS 347 pipe fittings — 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 fittings is ordered to ASTM A403 WP347 whichever name is on the enquiry.
Which standard covers SS 347 buttweld fittings?
ASTM A403 WP347 is the material specification; dimensions follow ASME B16.9 (light-wall MSS SP-43 fittings are ordered as CR347). Forged socket-weld and threaded fittings are made from ASTM A182 F347 material to ASME B16.11.
What is the difference between SS 347 WP-S and WP-W fittings?
S is seamless; W is welded from plate or welded pipe with the maker's welds radiographed. WX means all welds radiographed and WU all welds ultrasonically tested. Seamless costs more and is preferred for critical service.
Can SS 347 fittings be welded to carbon steel?
Yes — ER309L (or E309L electrode) is the usual filler when joining it to carbon steel.
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