Stainless Steel 347/347H Pipe Fittings Supplier
Stainless steel 347/347H pipe fittings are particularly suited for hot hydrocarbon and steam lines as they can withstand the stress caused by welding in the temperature range from 425 °C to 815 °C. The conventional 304 steel is incapable of resisting chromium carbide formation in the same temperature range and niobium helps to overcome this problem. Metinox Overseas produces these pipe fittings and other products of similar kind according to ASTM A403 WP347 and WP347H, both in seamless and welded version, for clients in the GCC and worldwide. One common mistake made by customers when ordering is to ask for 347 while the design should be made for 347H, which is the only grade with controlled carbon content, hence providing the necessary resistance to creep.
Request a QuotationTable of Contents
- What Are SS 347 Pipe Fittings and Where Does UNS S34700 Earn Its Place?
- Stainless Steel 347 Pipe Fittings Specification
- Various Types of Stainless Steel 347 Pipe Fittings
- Chemical Composition of Stainless Steel 347 / 347H Pipe Fittings
- SS 347 / 347H Equivalent Grades
- Mechanical Properties of SS 347 / 347H Pipe Fittings
- Physical Properties of SS 347 / 347H
- ASME B16.9 Dimensions for SS 347 Buttweld Pipe Fittings
- SS 347 Stub End Dimensions
- Dimensional Tolerances of SS 347 / 347H Pipe Fittings
- Applications of Stainless Steel 347/347H Pipe Fittings
- What Sets the Price of SS 347 / 347H Pipe Fittings
- Certificates and Inspection for UNS S34709 Fittings
- Delivery, Packing and Laydown for Stainless Steel 347 Fittings
- Request a Price for Stainless Steel 347/347H Pipe Fittings
- Complete the Line with SS 347 Pipes, Tubes and Flanges
- Buyer Questions on SS 347 / 347H Pipe Fittings
What Are SS 347 Pipe Fittings and Where Does UNS S34700 Earn Its Place?
SS 347 is an austenitic chromium nickel stainless steel stabilised with niobium (columbium). The niobium ties up carbon as niobium carbide, so chromium stays in solution at the grain boundaries after welding and during long exposure in the sensitisation range. The result is resistance to intergranular corrosion without needing a low carbon grade.
The two variants serve different jobs:
- WP347 (UNS S34700, EN 1.4550): carbon 0.08% max. Chosen for intergranular corrosion resistance in welded lines and for polythionic acid stress corrosion cracking risk during refinery shutdowns.
- WP347H (UNS S34709): carbon controlled at 0.04 to 0.10%. The higher carbon gives better creep and stress rupture strength above about 540 °C (1000 °F), so it is the grade for hot steam and furnace outlet service.
Stainless Steel 347 Pipe Fittings Specification
| Parameter | Details |
|---|---|
| Material standard | ASTM A403 / ASME SA403 (buttweld); ASTM A182 / ASME SA182 F347, F347H (forged) |
| Grades | WP347 (UNS S34700), WP347H (UNS S34709) |
| Construction classes (A403) | WP-S, WP-W, WP-WX, WP-WU |
| Forms Available | Elbow, Tee, Reducer, Cap, Stub End, Bend, Cross, Nipple, Coupling, Socket Weld, Threaded |
| Dimensional standards | ASME B16.9, ASME B16.11, MSS SP-43, ASME B16.25 |
| Bending Radius | R = 1D, 2D, 3D, 5D, 6D, 8D, 10D or Custom |
| Buttweld Size range | ½" to 48" NPS (DN 15 to DN 1200) as covered by ASME B16.9 |
| Forged Size range | ⅛" to 4" NPS (DN 6 to DN 100) per ASME B16.11 |
| Schedule | Sch 5S, 10S, 40S, 80S, STD, XS, 160, XXS (ASME B36.19M / B36.10M) |
| Pressure class(forged ) | Socket weld 3000, 6000, 9000; threaded 2000, 3000, 6000 |
| Ends | Bevelled to ASME B16.25, socket weld, threaded NPT |
Choosing between WP-S and welded classes? Our guide on seamless vs welded stainless steel pipe sets out the trade offs, and the same logic applies to fittings made from that pipe.
Various Types of Stainless Steel 347 Pipe Fittings
Not sure which fitting fits your application? Share your size, pressure class and quantity, and our team will recommend the right type with a quick quote. Get a Free Quote
Chemical Composition of Stainless Steel 347 / 347H Pipe Fittings
| Grade | C | Mn | P | S | Si | Cr | Ni | Nb |
|---|---|---|---|---|---|---|---|---|
| SS 347(WP347) | 0.08 max | 2.00 max | 0.045 max | 0.030 max | 1.00 max | 17.0 to 19.0 | 9.0 to 13.0 | 10 × C min, 1.10 max |
| SS 347H(WP347H) | 0.04 to 0.10 | 2.00 max | 0.045 max | 0.030 max | 1.00 max | 17.0 to 19.0 | 9.0 to 13.0 | 8 × C min, 1.10 max |
SS 347 / 347H Equivalent Grades
| Grade | UNS | Werkstoff Nr. / EN | EN name | JIS |
|---|---|---|---|---|
| SS 347 | S34700 | 1.4550 | X6CrNiNb18-10 | SUS 347 |
| SS 347H | S34709 | 1.4961 (nearest) | X8CrNiNb16-13 | SUS 347H (tube/pipe) |
Mechanical Properties of SS 347 / 347H Pipe Fittings
Room-temperature mechanical properties per ASTM A403:
| Property | WP347 / WP347H (ASTM A403) |
|---|---|
| Tensile strength, min | 515 MPa (75 ksi) |
| Yield strength 0.2% offset, min | 205 MPa (30 ksi) |
| Elongation in 50 mm (2 in), min | 28% longitudinal; 20% transverse |
| Hardness | No limit set by ASTM A403. A hardness cap applies only where the purchase order invokes NACE MR0175 / ISO 15156 or a project specification |
Allowable stresses above room temperature come from ASME BPVC Section II Part D for the design code you are working to.
Physical Properties of SS 347 / 347H
| Property | Typical value |
|---|---|
| Density | 8.0 g/cm³ (0.29 lb/in³) |
| Melting range | About 1400 to 1425 °C |
| Modulus of elasticity | 193 GPa (28 × 10⁶ psi) |
| Thermal conductivity at 100 °C | About 16 W/m·K |
| Mean coefficient of thermal expansion, 0 to 100 °C | About 16.6 µm/m·°C |
| Electrical resistivity at 20 °C | About 0.73 µΩ·m |
ASME B16.9 Dimensions for SS 347 Buttweld Pipe Fittings
| NPS | DN | OD at bevel, mm (in) | 90° LR elbow A | 90° SR elbow | 45° LR elbow B | Tee C | Reducer H | Cap E |
|---|---|---|---|---|---|---|---|---|
| ½ | 15 | 21.3 (0.84) | 38 (1.50) | – | 16 (0.62) | 25 (1.00) | – | 25 (1.00) |
| ¾ | 20 | 26.7 (1.05) | 38 (1.50) | – | 19 (0.75) | 29 (1.12) | 38 (1.50) | 25 (1.00) |
| 1 | 25 | 33.4 (1.32) | 38 (1.50) | 25 (1.00) | 22 (0.88) | 38 (1.50) | 51 (2.00) | 38 (1.50) |
| 1½ | 40 | 48.3 (1.90) | 57 (2.25) | 38 (1.50) | 29 (1.12) | 57 (2.25) | 64 (2.50) | 38 (1.50) |
| 2 | 50 | 60.3 (2.38) | 76 (3.00) | 51 (2.00) | 35 (1.38) | 64 (2.50) | 76 (3.00) | 38 (1.50) |
| 3 | 80 | 88.9 (3.50) | 114 (4.50) | 76 (3.00) | 51 (2.00) | 86 (3.38) | 89 (3.50) | 51 (2.00) |
| 4 | 100 | 114.3 (4.50) | 152 (6.00) | 102 (4.00) | 64 (2.50) | 105 (4.12) | 102 (4.00) | 64 (2.50) |
| 6 | 150 | 168.3 (6.63) | 229 (9.00) | 152 (6.00) | 95 (3.75) | 143 (5.62) | 140 (5.50) | 89 (3.50) |
| 8 | 200 | 219.1 (8.63) | 305 (12.00) | 203 (8.00) | 127 (5.00) | 178 (7.00) | 152 (6.00) | 102 (4.00) |
| 10 | 250 | 273.0 (10.75) | 381 (15.00) | 254 (10.00) | 159 (6.25) | 216 (8.50) | 178 (7.00) | 127 (5.00) |
| 12 | 300 | 323.8 (12.75) | 457 (18.00) | 305 (12.00) | 190 (7.50) | 254 (10.00) | 203 (8.00) | 152 (6.00) |
Sizes 14" to 48" follow ASME B16.9 and are quoted to your drawing. Cap length E is for standard wall.
SS 347 Stub End Dimensions
| NPS | Lap diameter G, mm (in) | Long pattern F, mm (in) | Short pattern F, mm (in) |
|---|---|---|---|
| ½ | 35 (1.38) | 76 (3.00) | 51 (2.00) |
| 1 | 51 (2.00) | 102 (4.00) | 51 (2.00) |
| 2 | 92 (3.62) | 152 (6.00) | 64 (2.50) |
| 3 | 127 (5.00) | 152 (6.00) | 64 (2.50) |
| 4 | 157 (6.19) | 152 (6.00) | 76 (3.00) |
| 6 | 216 (8.50) | 203 (8.00) | 89 (3.50) |
| 8 | 270 (10.62) | 203 (8.00) | 102 (4.00) |
| 12 | 381 (15.00) | 254 (10.00) | 152 (6.00) |
Dimensional Tolerances of SS 347 / 347H Pipe Fittings
All fittings are supplied to the dimensional tolerances of the governing standards below.
| Fitting Type | OD Tolerance | Wall Thickness Tolerance | End-to-End Tolerance |
|---|---|---|---|
| Buttweld Fittings | +1.6 / −0.8 mm (NPS ≤2½), ±1.6 mm (NPS 3 to 4) | Min. 87.5% of nominal | ±2 mm (NPS ≤24) |
| Forged SW / Threaded | As per standard table | Min. wall as per standard table | As per standard table |
| Light Wall Fittings and Stub Ends | As per standard table | As per standard table | As per standard table |
Note: Tolerances for larger sizes and other fitting types are set out in the current edition of ASME B16.9. Send your size and schedule and we will confirm the applicable limits.
Applications of Stainless Steel 347/347H Pipe Fittings
Grade 347 is chosen when a line will sit for long periods between 425 °C and 815 °C, the band where ordinary 304 can lose chromium at its grain boundaries. Niobium ties up the carbon first, so welded joints keep their corrosion resistance after years of hot service.
- Refining: FCC units, hydroprocessing and reformer furnace piping, where 347 resists polythionic acid stress corrosion cracking during shutdowns.
- Petrochemicals and chemical processing: Pyrolysis units, hot reaction systems and furnace tube connections that operate inside the carbide precipitation range.
-
Power generation and boilers: Steam headers, superheater connections and HRSG circuits, where 347H provides creep strength above 538 °C.
-
Nuclear auxiliary systems: Auxiliary piping, coolant headers and waste handling circuits, where niobium holds up through welding better than the titanium in 321.
-
Heat exchangers and industrial furnaces: High temperature shell and tube units and hot zone components that need stability and oxidation resistance over long exposure.
-
Aerospace: Exhaust collectors and manifolds that face repeated heating and cooling cycles.
What Sets the Price of SS 347 / 347H Pipe Fittings
Nickel and niobium markets move the price, so each enquiry is quoted at current rates. No price list is published.
| Factor | Why it moves the price |
|---|---|
| Grade: WP347 or WP347H | 347H needs controlled carbon and checks for creep service |
| Size and schedule | More metal per piece; Sch 80S and heavier rise sharply |
| Seamless (WP-S) or welded (WP-W, WP-WX) | Seamless and fully radiographed welded fittings cost more |
| Quantity per size | Larger lots lower the unit price |
| Stock or mill order | Uncommon sizes need production setup |
| Certificate level | EN 10204 3.2 adds a witnessing inspector |
| Testing | PMI, IGC (ASTM A262 Practice E), RT, hardness are charged per lot |
| Incoterm and destination port | Freight and insurance are in CIF and similar terms, not in EXW or FOB |
For a fast quotation, send: grade (WP347 or WP347H), standard and edition, fitting type, NPS or DN, schedule or class, quantity, end finish, certificate level (3.1 or 3.2), inspection agency, any testing (PMI, IGC, RT, hardness), destination port and required date.
Request a QuotationCertificates and Inspection for UNS S34709 Fittings
Each fitting is marked with grade, size, schedule, standard and heat number so it traces to its EN 10204 certificate. Certificate level (3.1, or 3.2 with a witnessing inspector) is confirmed at quotation. Name the third party inspection agency your project requires in the enquiry.
Sample certificate formats are on our certificates page.
Ask for PMI on any mixed grade order. 347, 321 and 304 look identical in a laydown yard; only a reading of niobium and titanium separates 347 from 321.
Delivery, Packing and Laydown for Stainless Steel 347 Fittings
Lead time is confirmed at quotation.
For sea freight to the GCC and other export markets, fittings are typically packed with bevel protectors or end caps, separated by grade and heat, and boxed in wooden cases to keep carbon steel contact, sand and salt air away from the surface. On site, keep stainless fittings off the ground and covered, away from carbon steel grinding dust, which causes surface rust spots, and away from coastal chloride spray during long laydown.
Our packing and dispatch page shows how export cases are made up. For country supply notes, see UAE, Saudi Arabia, Qatar, Kuwait, Oman and Bahrain.
Request a Price for Stainless Steel 347/347H Pipe Fittings
Send your line list or material take off with grades, sizes, schedules and quantities. Add your certificate level, inspection agency, any sour service or IGC testing, Incoterm and destination port. A complete enquiry gets a complete quotation on the first reply.
Request a QuotationComplete the Line with SS 347 Pipes, Tubes and Flanges
Build a full 347 system, pipe to fitting to flange, in one grade:
- SS 347 flanges: ASTM A182 F347 weld neck, slip on, blind and threaded flanges
- SS 347H flanges: ASTM A182 F347H for creep service
- Stainless steel 347 seamless pipes: ASTM A312 TP347 / TP347H
- SS 347 welded pipes: ASTM A312 TP347 / TP347H
- SS 347 tubes and heat exchanger tubing: ASTM A213 / A249
- All stainless steel pipe fittings
Also in 347: SS 347/347H pipe specifications and pressure ratings and SS 347 EFW pipe for large bore lines. Browse every grade on our stainless steel pipes page.
Buyer Questions on SS 347 / 347H Pipe Fittings
Both are niobium stabilised. WP347H has carbon controlled at 0.04 to 0.10%, against 0.08% max for WP347. The higher carbon gives better creep and stress rupture strength above about 540 °C, so 347H is specified for hot steam and furnace outlet service.
Austenitic stainless steels including 347 are covered by ISO 15156-3 when solution annealed, at 22 HRC maximum, and only inside set limits on temperature, H2S partial pressure and chlorides. Outside those limits a higher alloy is normally needed.
Buttweld fittings follow ASTM A403 WP347 or WP347H for material and ASME B16.9 for dimensions. Forged socket weld and threaded fittings follow ASTM A182 F347 or F347H and ASME B16.11.
Certificate level and inspection agency are confirmed at quotation. State 3.1 or 3.2 and the agency you require in your enquiry.
Grade, standard, fitting type, size, schedule, quantity, end finish, certificate level, inspection and testing needs, destination port and required date. A line list or material take off works too.
Not for corrosion resistance. Niobium ties up carbon, so the heat-affected zone does not sensitise in normal welding. Some refinery specifications call for a stabilising heat treatment around 870 to 900 °C after welding for polythionic acid service; if yours does, state it in the enquiry.
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