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UNS S34700 (AISI 347) Stainless Steel Forgings
Seamless rolled rings, forged flanges, round bars, discs, sleeves, bushings, shafts, tube sheets and forged tubes to ASTM A182 F347 and EN 1.4550
UNS S34700 is the UNS number for AISI 347, a niobium (columbium) stabilised 18Cr-11Ni austenitic stainless steel. Niobium locks up carbon as stable niobium carbides inside the grains, which keeps chromium in solution and lets the steel resist intergranular corrosion after exposure in the chromium carbide precipitation range of 800-1500 °F (427-816 °C). For forgings the grade is ordered as ASTM A182 F347 or EN 1.4550 / X6CrNiNb18-10. We forge it to drawing as rings, flanges, bars, discs and shafts.
Grade designations and equivalents
| System | Designation | Scope |
|---|---|---|
| UNS | S34700 (347H is S34709) | Unified numbering |
| AISI / ASTM | Type 347 | Wrought austenitic stainless steel |
| ASTM / ASME forgings | A182 F347, SA-182 F347 | Forged flanges, fittings, valves and parts for high-temperature service |
| ASTM bar | A276, A479 / SA-479 | Bars and shapes; bars for boilers and pressure vessels |
| ASTM plate, sheet, strip | A240 | Flat-rolled product |
| EN | 1.4550, X6CrNiNb18-10 | European designation |
| Aerospace | AMS 5646 | Bar for aerospace use |
One point worth clearing up, because it appears on a number of supplier pages: UNS S34700 is not AISI 310H. 310H is a separate 25Cr-20Ni heat resisting grade with its own UNS number and different properties. The two cannot be substituted for each other.
Chemical composition
| Element | Symbol | Requirement |
|---|---|---|
| Carbon | C | 0.08 max |
| Manganese | Mn | 2.00 max |
| Phosphorus | P | 0.045 max |
| Sulphur | S | 0.030 max |
| Silicon | Si | 1.00 max (flat-rolled 347 to A240 is limited to 0.75 max) |
| Chromium | Cr | 17.0 - 19.0 |
| Nickel | Ni | 9.0 - 13.0 |
| Niobium (columbium) | Nb (Cb) | 10 x C min, 1.10 max |
| Iron | Fe | Balance |
ASTM A182 states that grades F347 and F348 shall contain niobium (columbium) of not less than ten times the carbon content and not more than 1.10 %. Heat analysis appears on every test certificate we issue; product analysis is available on request.
Mechanical properties
Specified minimums, solution annealed, ASTM A182 F347
| Property | Metric | Imperial |
|---|---|---|
| Tensile strength, min | 515 MPa | 75 ksi |
| 0.2 % offset yield strength, min | 205 MPa | 30 ksi |
| Elongation in 50 mm (2 in.), min | 30 % | 30 % |
| Hardness, max | 217 HBW | 217 HBW |
Typical values, annealed 1038 °C (1900 °F), 25 mm (1 in.) round bar
| 0.2 % yield | Tensile | Elongation in 2 in. | Reduction of area | Brinell | Izod impact |
|---|---|---|---|---|---|
| 255 MPa / 37 ksi | 621 MPa / 90 ksi | 50 % | 65 % | 150 HB | 149 J / 110 ft-lb |
Typical values are for comparison only. Acceptance is always against the minimums of the ordered specification at the ordered section size.
Physical properties, typical for Type 347
| Density | 7.96 g/cm³ (0.288 lb/in³) |
|---|---|
| Modulus of elasticity | 193 GPa (28.0 x 106 psi) |
| Thermal conductivity at 100 °C | 16.3 W/m·K (9.2 Btu/ft·hr·°F) |
| Thermal expansion, 0-100 °C | 16.6 µm/m·K (9.3 x 10-6 in/in/°F) |
| Electrical resistivity at 20 °C | 72 µΩ·cm |
| Melting range | 1371-1400 °C (2500-2550 °F) |
| Magnetic response | Non-magnetic in the annealed condition |
Melting, forging and heat treatment
EAF plus VOD as standard. ESR remelt where the order or the end user specification calls for it.
Heat uniformly to 1149-1232 °C (2100-2250 °F). Do not forge below 927 °C (1700 °F). Forgings may be air cooled.
982-1093 °C (1800-2000 °F) followed by rapid cooling, to dissolve carbides and restore corrosion resistance after forging.
Because the grade is niobium stabilised, stress relief inside the 800-1500 °F band can be applied without sensitising the steel.
Each UNS S34700 forging leaves our works with a traceable record: melt and heat number, forging reduction ratio, heat treatment chart, test specimen location and NDT report. Where the purchaser calls for a corrosion acceptance test, intergranular corrosion testing to ASTM A262 can be added to the order.
UNS S34700 forged products we manufacture
| Forged form | Typical application |
|---|---|
| Seamless rolled rings, retaining rings, spacer rings | Compressor and turbine casings, expansion joints, bearing housings |
| Forged flanges: weld neck, slip-on, blind, long weld neck | Refinery and chemical piping, polythionic acid service, heat exchanger connections |
| Forged round bars, billets, blocks | Machined valve internals, fasteners, instrument parts |
| Forged discs, blanks, hubs | Pump and compressor components, closure heads |
| Forged sleeves, bushings, hollow bars | Offshore and subsea production equipment, rotating assemblies |
| Forged shafts, spindles, eccentric shafts | Power transmission, gearboxes, gas compressors, agitators |
| Forged tube sheets, nozzles, forged tubes and pipes | Heat exchangers, separators, pulp and paper digesters, desalination plant |
| Valve bodies, bonnets, seat rings, stems and stem blanks | Ball, gate, globe, check and plug valves |
| Custom open-die forging pieces | Made to drawing: aerospace piston engine manifolds, thermal oxidisers, pharmaceutical process equipment |
Size capability
| Rolled ring outside diameter | ____ to ____ mm |
|---|---|
| Ring height and wall thickness | ____ to ____ mm |
| Forged bar and shaft diameter | ____ to ____ mm |
| Maximum single piece weight | ____ kg |
| Supply condition | Black forged, rough machined or finish machined |
Testing, inspection and certificates
Non-destructive testing is matched to the metallurgy of the product rather than applied from a standard list. EN 10228-4 is the European standard covering ultrasonic testing of austenitic and austenitic-ferritic stainless steel forgings, so it is the correct reference for UNS S34700. EN 10228-3 applies to ferritic or martensitic forgings and does not suit this grade. ASTM A388/A388M is the usual North American practice for ultrasonic examination of steel forgings, with the acceptance quality level agreed between purchaser and manufacturer.
EN 10228-4 or ASTM A388/A388M, to the acceptance class stated on the order.
Liquid penetrant examination. Magnetic particle does not apply to this austenitic grade.
Tensile, hardness and, where specified, impact testing from prolongations or sacrificial pieces.
EN 10204 Type 3.1 issued by our authorised inspection representative, or Type 3.2 countersigned by SGS, BV, TUV, Lloyd's or another agreed third party.
Choosing between 347, 347H, 321 and 316
347 and 321 are both stabilised grades, 347 with niobium and 321 with titanium, and both are meant for service where unstabilised 304 would sensitise. 347H (UNS S34709) is the higher carbon, coarser grain variant used where creep and stress rupture strength above roughly 537 °C (1000 °F) governs the design. Where chloride pitting is the controlling mechanism, 316 or 316L is usually the better choice, since 347 behaves much like 304 and remains open to pitting, crevice attack and chloride stress corrosion cracking. 347 is also not hardenable by heat treatment, and the niobium addition makes it dearer than 304.
If the grade choice is still open, send us the operating temperature, the medium and the governing code at sales@steelforgepieces.com. We will comment before you commit to a forging.
Frequently asked questions
What is UNS S34700?
Is UNS S34700 the same as AISI 310H?
How much niobium does ASTM A182 F347 require?
What are the minimum mechanical properties of F347 forgings?
At what temperature is UNS S34700 forged?
Which ultrasonic standard applies to 347 forgings?
What is the difference between an EN 10204 3.1 and a 3.2 certificate?
Who supplies UNS S34700 open-die forgings from China?
Request a quotation for UNS S34700 forgings
Send a drawing, a finished machined size or a rough forging size. We reply with price, forging route, heat treatment plan, NDT scope and lead time.
- Jiangyin Jiangnan Metal Co., Ltd., Open-Die Forging Factory
- No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province 214423, China
- Phone, WhatsApp and WeChat: +86-189-2135-9659
- Email: sales@steelforgepieces.com
Related grades
Standards referenced
ASTM A182/A182M, forged or rolled alloy and stainless steel pipe flanges, forged fittings, and valves and parts for high-temperature service. ASTM A276, A479/SA-479 and A240. AMS 5646. ASTM A388/A388M, ultrasonic examination of steel forgings. ASTM A262, detecting susceptibility to intergranular attack in austenitic stainless steels. EN 10228-4, non-destructive testing of steel forgings, part 4, ultrasonic testing of austenitic and austenitic-ferritic stainless steel forgings. EN 10204, inspection documents for metallic products. Figures on this page are given for guidance; the ordered specification governs.