SS 347 PlateASTM A240 UNS S34700 · Manufacturer, stockist & exporter, India
Also sold as AISI 347 · UNS S34700 · W.Nr 1.4550 · Niobium-stabilised stainless
SS 347 plate is SS 347 (UNS S34700) rolled to 3/16" (4.76 mm) thickness and above for pressure parts, heavy sections and cut blanks under 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 request
- Export packing
Reviewed by the Kanak Steel & Engineering Co. technical team · Updated October 2026
What is SS 347 Plate?
SS 347 plate is a niobium-stabilised austenitic stainless steel supplied as plate 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
- Thickness
- 3/16" (4.76 mm) and above
- Density
- 7.96 g/cm³
- Supplied as
- Annealed · HRAP · cut to size
- Best at
- Welded high-temperature piping in refineries and power plants
SS 347 Plate Specification & Sizes
| Material standard | ASTM A240 · ASME SA-240 |
|---|---|
| General requirements | ASTM A480 — dimensions, tolerances and finishes |
| Grade | SS 347 · UNS S34700 · S34709 (347H) · W.Nr 1.4550 |
| Thickness | 3/16" (4.76 mm) and above — thinner is sheet |
| Width × length | 1000 / 1250 / 1500 / 2000 / 2500 mm × up to 6000 mm, or cut to drawing |
| Condition & finish | Annealed · hot rolled, annealed & pickled (No.1) |
| Cutting | Cut to size — rectangles, strips, circles & rings |
| Testing | PMI · UT (plate) · intergranular corrosion · hardness, on request |
| Documents | EN 10204 3.1 · 3.2 with third-party inspection · packing list · certificate of origin |
Sheet or plate?
Both are ordered under ASTM A240, so buyers often mix them up. The line is thickness: below 3/16" is sheet, 3/16" and over is plate. If your drawing calls for under 3/16" (4.76 mm), you need SS 347 sheet; for 4.76 mm and up, you are in the right place.
SS 347 Plate Cut to Size
Most 347 plate leaves us as pieces, not full mill plates. Cutting from a full plate means you pay only for what you use, and each piece keeps the heat number of the plate it came from.
| Full & part plates | Full mill plates, halves and quarters |
|---|---|
| Rectangles & strips | To your list of finished sizes, or to a drawing |
| Circles & rings | Blanks for blind flanges, covers, tube sheets and nozzles |
| Machining allowance | State finished size and allowance; thermally cut edges are normally machined back |
| Traceability | Heat number transferred to every piece before cutting |
Send a cutting list or DXF; we nest pieces to reduce off-cut and quote per piece.
SS 347 Plate 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 Plate 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 Plate Weight Chart & Calculator
Use this to budget freight and price per piece. Weight (kg) = length (m) × width (m) × thickness (mm) × 7.96.
Example: 2000 × 1000 × 10 mm
2.0 × 1.0 × 10 × 7.96 = 159.2 kg
Total weight —
| Thickness | 2000 × 1000 plate | Per m² |
|---|---|---|
| 5 mm | 79.6 kg | 39.8 kg |
| 6 mm | 95.5 kg | 47.8 kg |
| 8 mm | 127.4 kg | 63.7 kg |
| 10 mm | 159.2 kg | 79.6 kg |
| 12 mm | 191.0 kg | 95.5 kg |
| 16 mm | 254.7 kg | 127.4 kg |
| 20 mm | 318.4 kg | 159.2 kg |
| 25 mm | 398.0 kg | 199.0 kg |
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 Plate 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. PMI can be arranged on request — state it on your enquiry.
Under technical review for TDS.
| Element | SS 347 | SS 321 |
|---|---|---|
| Nickel | As specified | As specified |
| Chromium | As specified | As specified |
| Titanium | — | As specified |
| Niobium | As specified | — |
| Iron | As specified | As specified |
| Manganese | As specified | As specified |
SS 347 Plate Price — What Decides It
Two quotes for "347 plate" can differ by 20% and both be fair. We quote 347 plate 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 Plate Testing & Inspection
Plate goes into pressure parts and heavy sections, so it is inspected for internal soundness and flatness as well as chemistry. These tests are added to the order and reported on the certificate or as separate reports.
| Ultrasonic testing | Straight-beam UT to ASTM A578 (levels A, B or C; plate 10 mm and over) or EN 10160 (S0–S3 body, E0–E4 edge classes) |
|---|---|
| Flatness & dimensions | Per ASTM A480 tables for thickness, width and length |
| Corrosion testing | ASTM A262 (intergranular corrosion), practice as specified |
| PMI | Alloy verification on each plate, or each cut piece if required |
| Third-party inspection | Witness by your inspector or agency, with an EN 10204 3.2 certificate |
UT checks the plate body along a scan grid and a band along each edge, where laminations matter most for welding.
SS 347 Plate Applications
Plate is chosen for pressure-bearing walls, heavy sections and parts machined from solid. For linings, bellows and pressed parts, see SS 347 sheet.
SS 347 Plate vs 321, 304 and 310S
| Grade | Plate 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 plate order runs
- 01Enquiry review — we confirm size, standard edition and documents against your MR or drawing.
- 02Heat selection & PMI — the mill certificate is checked against your order; PMI before processing is available on request.
- 03Processing — cutting to your sizes, with heat numbers transferred to every piece.
- 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.
Fabricating Heavy SS 347 Plate
Shells, heads and tube sheets mean thick sections and multi-pass welds. These are the points that decide whether 347 plate keeps its corrosion resistance after fabrication; matching filler is ER347 (AWS A5.9).
General guidance only; follow your approved WPS, PQR and design code.
| Joint preparation | Single-V up to moderate thickness, double-V or J-prep for heavy plate to cut weld volume and distortion. |
|---|---|
| Interpass temperature | Keep it low — typically 150 °C maximum; no preheat is needed. |
| Cold forming | Heavy cold forming of heads and shells may require solution annealing under your code. |
| Machining | Sharp tools, positive rake and steady feed; austenitic grades work-harden if the tool rubs. |
How to Order SS 347 Plate: RFQ Checklist
Get an accurate quote the first time. Copy this list into your enquiry:
- Standard and edition — e.g. ASTM A240-latest
- Thickness × width × length, and number of pieces
- Full plates or cut pieces (attach drawing)
- Certificate type — 3.1 or 3.2, and the inspection agency
- Extra tests — UT, intergranular corrosion
- Delivery port, Incoterm and required date
SS 347 plate for export
FOB / CIF · Nhava Sheva (JNPT), MumbaiSS 347 plate — questions buyers ask
Is SS 347 the same as AISI 347?
AISI 347, UNS S34700, W.Nr 1.4550 are names used for SS 347 (W.Nr / EN numbers and older UNS variants are the closest designations; their limits can differ slightly, so specify the UNS number and ASTM grade on the order), and plate is ordered to ASTM A240 whichever name is on the enquiry.
What thickness counts as SS 347 plate?
Under ASTM A240 and its general-requirements standard, flat material below 3/16" (4.76 mm) is sheet (or strip if narrower than 24") and 3/16" (4.76 mm) and over is plate. Order the form that matches your drawing thickness.
What is the price of SS 347 plate per kg?
It moves with nickel on the LME, so a fixed list price is out of date within days. Thickness, cut size, quantity and documents also change it. Send your size and quantity and we quote the same working day.
Do you supply ultrasonically tested SS 347 plate?
Yes, UT can be added to the order — to ASTM A578 or the level your specification states. The UT report is supplied with the mill certificate.
Can SS 347 plate be cut into circles and rings?
Yes. Blanks for blind flanges, covers and tube sheets are cut from plate to your drawing, with the heat number marked on every piece.
What machining allowance should I leave on cut plate?
It depends on the cutting method and finished tolerance. Give us the finished size and your allowance; thermally cut edges are normally machined back to sound metal.
How heavy is a SS 347 plate?
Weight (kg) = length (m) × width (m) × thickness (mm) × 7.96. A 2000 × 1000 × 10 mm plate weighs about 159 kg; use the calculator on this page for your size.
What documents come with an export shipment?
An EN 10204 3.1 mill certificate (or 3.2 with a third-party inspector), commercial invoice, packing list with heat numbers, and certificate of origin. Test reports are added for any extra tests ordered.
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