SS 347 CoilASTM A240 UNS S34700 · Manufacturer, stockist & exporter, India
Also sold as AISI 347 · UNS S34700 · W.Nr 1.4550 · Niobium-stabilised stainless
SS 347 coil is supplied as full-width mother coil, slit coil or precision strip to ASTM A240. 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 Coil?
SS 347 coil is a niobium-stabilised austenitic stainless steel supplied as coil to ASTM A240 (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
- Standard
- ASTM A240
- Forms
- Mother coil · slit coil · strip
- Density
- 7.96 g/cm³
- Finish
- 2B · BA · No.4
- Best at
- Welded high-temperature piping in refineries and power plants
SS 347 Coil Specification & Sizes
| Material standard | ASTM A240 |
|---|---|
| Grade | SS 347 |
| Thickness | 0.1 mm to 6 mm, depending on mill route |
| Width | Mill width, or slit from 10 mm upwards |
| Coil weight & ID | To order — state maximum coil weight and inner diameter |
| Finish | 2B · BA · No.4 · 2D |
| Documents | EN 10204 3.1 · 3.2 with third-party inspection |
SS 347 Coil: Slitting & Cut-to-Length Specification
347 coil is bought for a production line, so state thickness, slit width, inner diameter and maximum coil weight with the grade.
| Standard | ASTM A240 |
|---|---|
| Thickness tolerance | Per ASTM A480 |
| Finish | 2B · BA · No.4 · 2D |
ID, coil weight, edge, camber and interleaving: see the coil guide.
SS 347 Coil 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 Coil 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.
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 Coil 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 Coil 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 Coil vs 321, 304 and 310S
| Grade | Coil standard | PREN (approx.) | Pick it when |
|---|---|---|---|
| SS 321 | ASTM A240 | ≈ 18 | High-temperature service between 425 and 815 °C |
| SS 304 | ASTM A240 | ≈ 18 | General corrosion resistance, food, water and architectural work |
| SS 347 | ASTM A240 | ≈ 18 | Welded high-temperature piping in refineries and power plants |
| SS 310 / 310S | ASTM A240 | ≈ 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 coil 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.
Welding & Fabricating SS 347 Coil
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 Coil: RFQ Checklist
Get an accurate quote the first time. Copy this list into your enquiry:
- Thickness and width
- Coil weight and inner diameter
- Finish and edge (mill or slit)
- Certificate type
- Delivery port and date
SS 347 coil for export
FOB / CIF · Nhava Sheva (JNPT), MumbaiSS 347 coil — 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 coil is ordered to ASTM A240 whichever name is on the enquiry.
Can SS 347 coil be slit to width?
Yes. Coils can be slit to narrow widths for stamping, tube making and spring work; state width tolerance and coil weight on the enquiry.
What inner diameter do SS 347 coils have?
508 mm (20") and 610 mm (24") are the common IDs. Tell us your decoiler ID and maximum coil weight and we slit to suit.
Can I order SS 347 cut-to-length sheets from coil?
Yes. Coil can be levelled and cut to length; state length tolerance and flatness.
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