Stainless steel / UNS S34700
347 is an 18/10 austenitic stainless steel stabilised with niobium (columbium), giving resistance to intergranular corrosion and good high-temperature properties after welding.
- UNS S34700
- W.Nr. 1.4550
- Spec ASTM A240
- Density 7.96 g/cm³
Also known as / equivalents
| System | Designation |
|---|---|
| UNS | S34700 |
| W.Nr. | 1.4550 |
| EN | X6CrNiNb18-10 |
| JIS | SUS347 |
| Also known as | AISI 347, 1.4550, SUS347 |
Chemical composition
| Element | Min % | Max % |
|---|---|---|
| C | — | 0.08 |
| Mn | — | 2.00 |
| P | — | 0.045 |
| S | — | 0.030 |
| Si | — | 0.75 |
| Cr | 17.0 | 19.0 |
| Ni | 9.0 | 13.0 |
| Nb | 10×C | 1.00 |
| Fe | Bal. | — |
Mechanical properties
| Property | Value |
|---|---|
| Tensile strength (min) | 515 MPa (74.7 ksi) |
| Yield strength, 0.2% offset (min) | 205 MPa (29.7 ksi) |
| Elongation in 50 mm (min) | 40 % |
| Hardness | 201 HB max |
Physical properties
| Property | Metric | Imperial |
|---|---|---|
| Density | 7.96 g/cm³ | 0.288 lb/in³ |
| Magnetic response | Non-magnetic when annealed; may become slightly magnetic after cold work | — |
Available forms & specifications
| Form | Specification | Size range |
|---|---|---|
| Sheets, plates & coils | ASTM A240 / ASME SA240 | 0.3 mm – 6 mm |
| Seamless & welded pipe | ASTM A312 / ASME SA312 | 1/8" – 24" NB |
| Tubes | ASTM A213, A249, A269 | 1/8" – 24" NB |
| Bars & rods | ASTM A276, A479 | 3 mm – 500 mm |
| Flanges & forgings | ASTM A182 / ASME SA182 | 1/2" – 48" NB (larger on request) |
| Buttweld fittings | ASTM A403 / ASME SA403 | 1/2" – 48" NB |
| Fasteners | ASTM A193 / A194, F593 / F594 | M3 – M56 |
Corrosion & temperature resistance
Corrosion resistance rises with chromium, molybdenum and nitrogen: 304 handles general atmospheric and food-contact service, 316/317 add resistance to chlorides and pitting, 904L handles strong reducing acids, and stabilised 321/347 resist intergranular attack after welding or high-temperature exposure.
Applications
SS 347: Aircraft exhaust, refinery and boiler parts. Process piping, tanks and vessels, heat exchangers, food, dairy and pharmaceutical equipment, architectural work and general engineering.
SS 347 vs SS 321
| SS 347 | SS 321 | |
|---|---|---|
| UNS | S34700 | S32100 |
| Key property | Niobium-stabilised | Titanium-stabilised, high-temperature use |
| Typical use | Aircraft exhaust, refinery and boiler parts | Exhaust systems, expansion joints, heaters |
| Cr (wt %) | 17.0–19.0 | 17.0–19.0 |
| Ni (wt %) | 9.0–13.0 | 9.0–12.0 |
| Mo (wt %) | — | — |
| C (wt %) | ≤ 0.08 | ≤ 0.08 |
| Tensile / yield (min, MPa) | 515 / 205 | 515 / 205 |
Frequently asked questions
What is the UNS number of SS 347?
SS 347 is designated UNS S34700 (W.Nr. 1.4550, EN X6CrNiNb18-10).
What is SS 347 used for?
Niobium-stabilised. Typical uses: aircraft exhaust, refinery and boiler parts.
Is SS 347 magnetic?
Non-magnetic when annealed; may become slightly magnetic after cold work.
In which forms can I buy SS 347 from Rajkamal Metals?
Coils & Strips, Sheets & Plates, Pipes & Tubes, Round Bars & Rods, Structural Sections, Flanges, Buttweld Fittings, Socket Weld & Threaded Fittings, Fasteners, Ferrule / Instrumentation Fittings, Dairy Fittings, Dish Ends, SS Tanks, Custom Orders. Sizes as per standard; other sizes on request.
Do you supply a Mill Test Certificate with SS 347?
Yes. Actual values are given in the Mill Test Certificate (EN 10204 3.1) supplied with each order.
What is the difference between SS 347 and SS 321?
SS 347: niobium-stabilised. SS 321: titanium-stabilised, high-temperature use. See the comparison table on this page.
Last updated: 30 October 2026. Grade names identify the supply range; designations are not engineering equivalents. Availability, make, origin and documentation are confirmed at quotation.
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