Power Generation Boilers and Steam Lines
Boiler systems and high-pressure steam lines in power plants use TP347H for its creep strength at temperature, while 17.0 to 19.0% chromium forms a protective oxide layer on the hot surface.
ASTM A312 / ASME SA-312 / UNS S34709 / W.Nr. 1.4912
Stainless Steel 347H Seamless Pipes Manufacturer in Thailand
ASTM A312 TP347H stainless steel seamless pipes for high-temperature service are made by Thaida Stainless Steel Manufacturing (Thailand) Co., Ltd. in Ban Bueng, Chonburi, Thailand, where solution annealing, grain size measurement and lot marking follow the H-grade rules of the standard. As the niobium-stabilized H grade of 347 for creep-loaded piping, UNS S34709 belongs to our stainless steel seamless pipe family, with EN 1.4912 as its nearest European equivalent; technical queries go to our Bang Phli, Samut Prakan office.
Stainless Steel 347H seamless pipeUNS S34709 / W.Nr. 1.4912
- 6 to 1016 mmOutside diameter
- 1 to 65 mmWall thickness
- Up to 18 mLength
- EN 10204 3.1Test certificate
EN 10204 3.1 certificate / 3.2 on request
Specifications for SS 347H Seamless Pipe
Line-class sizes are ordered as NPS with a schedule, and drawing sizes as OD with a wall. Grade requirements below follow ASTM A312, while the dimensional rows show the range our seamless stainless mill produces.
- Standard
- ASTM A312 / ASME SA-312
- Grade
- TP347H (UNS S34709)
- WNR
- 1.4912 (X7CrNiNb18-10)
- Nearest equivalent
- NPS and Schedules
- NPS 1/8 to NPS 30, Schedules 5S, 10S, 40S and 80S (dimensions as in ASME B36.19)
- Outside Diameter
- 6 to 1016 mm
- Wall Thickness
- 1 to 65 mm
- Length
- Up to 18 mcut lengths to order
- Manufacturing Route
- 1Seamless
- 2Hot finished or cold finished
- Heat Treatment
- Solution annealedthen quenched in water or rapidly cooled
- Grain Size
- ASTM No. 7 or coarser
- End Type
- Plain endbeveled end; threaded on Schedules 40S and 80S
- Surface Finish
- Pickled and passivatedbright annealed (BA), polished, mirror or brushed
- Test Certificate
- EN 10204 3.13.2 on request
Every ASTM A312 TP347H stainless steel seamless pipe we ship conforms to ASTM A312 and to its ASME counterpart, SA-312. A312 treats TP347H as a modification of TP347 for service in which creep and stress-rupture behavior control the design, and it accepts non-tabulated dimensions provided the pipe complies with all its other requirements. For heat exchanger bundles and other duties specified by tube OD and average wall, we make the same grade as stainless steel 347H seamless tubes.
Every length of SS 347H seamless pipe is hydrostatically tested or given a nondestructive electric test under ASTM A312. Tension tests are taken from lots of 100 pipes or fewer, each lot is flattening tested, and grain size is measured lot by lot after heat treatment. Results are reported on an EN 10204 3.1 (3.2 on request) certificate, and a third-party inspector can witness testing on request.
Chemical Composition of UNS S34709 Seamless Pipe
Each heat of UNS S34709 seamless pipe is analyzed against the TP347H limits of ASTM A312:
- CrChromium, 17.0 to 19.0
- NiNickel, 9.0 to 13.0
- NbNiobium, 8 × C min, 1.0 max
- MnManganese, 2.00 max
- SiSilicon, 1.00 max
UNS S34709347H
| Element | TP347H (UNS S34709), % |
|---|---|
| C (Carbon) | 0.04 to 0.10 |
| Mn (Manganese) | 2.00 max |
| P (Phosphorus) | 0.045 max |
| S (Sulfur) | 0.030 max |
| Si (Silicon) | 1.00 max |
| Cr (Chromium) | 17.0 to 19.0 |
| Ni (Nickel) | 9.0 to 13.0 |
| Nb (Niobium) | 8 × C min, 1.0 max |
TP347H carries no requirement for tantalum, nitrogen or molybdenum, so niobium is the only stabilizing element the certificate has to prove.
Niobium Stabilization and the Carbon Window
Two controls define the grade. The 0.04% carbon floor gives the strength that creep-loaded piping is designed on, and the 0.10% ceiling limits how much carbon the niobium has to bind. Niobium, required at eight times the carbon content or more, combines with carbon as niobium carbide. The grain boundaries are therefore not stripped of chromium by carbide precipitation when the pipe passes through the sensitizing range in welding or service, and the chromium stays in solution to resist intergranular attack.
Seamless S34709 Stainless Steel Pipe: Tensile Minimums and Heat Treatment
ASTM A312 sets the room-temperature minimums below for TP347H, confirmed by tension tests on each lot after the solution anneal.
| Property | Requirement |
|---|---|
| Tensile Strength, min | 515 MPa (75 ksi) |
| Yield Strength, min | 205 MPa (30 ksi) |
| Elongation in 50 mm (2 in.) or 4D, min, longitudinal | 35% |
| Elongation in 50 mm (2 in.) or 4D, min, transverse | 25% |
| Solution Anneal, cold finished | 1100 °C (2000 °F) min |
| Solution Anneal, hot finished | 1050 °C (1925 °F) min |
| Cooling | Quenched in water or rapidly cooled by other means |
| Grain Size | 7 or coarser |
A312 gives no elevated-temperature values; those belong to the design code of your piping system. Share the design pressure and temperature with your inquiry for seamless S34709 stainless steel pipe, and we will review the specified wall against them.
Grade 347H Designations in Other Standards
National standards and data sheets refer to grade 347H by the designations below.
- USA (ASTM / ASME)TP347H (ASTM A312 / ASME SA-312)
- USA (UNS)S34709
- Europe (EN / WNR)1.4912 (X7CrNiNb18-10), nearest equivalent
- Japan (JIS)SUS347H
- China (GB)S34779 (ISC) / 07Cr18Ni11Nb
- Russia (GOST)08X18H12Б
EN 10216-5 lists 1.4912 (X7CrNiNb18-10) among its creep-resisting steels, which makes it the nearest European match to TP347H rather than an identical grade. Orders placed against seamless WNR 1.4912 pipe are produced and certified as UNS S34709 to ASTM A312 TP347H, with 1.4912 serving only as a cross-reference.
NPS, Schedules and Tolerances for 347H Stainless Steel Seamless Pipe
The A312 dimension table runs from NPS 1/8 to NPS 30 across the 5S, 10S, 40S and 80S schedules, following ASME B36.19. For header and transfer-line bores in the two heavier schedules, the table below gives nominal wall, the permitted OD variation and the wall over-tolerance that results (mm unless stated):
| NPS | DN | OD | Sch 40S Wall | Sch 80S Wall | OD Tolerance | Wall Over-Tolerance, 40S / 80S |
|---|---|---|---|---|---|---|
| 3 | 80 | 88.9 | 5.49 | 7.62 | +0.8 / -0.8 | +15.0% / +15.0% |
| 6 | 150 | 168.3 | 7.11 | 10.97 | +1.6 / -0.8 | +22.5% / +15.0% |
| 8 | 200 | 219.1 | 8.18 | 12.70 | +1.6 / -0.8 | +22.5% / +15.0% |
| 16 | 400 | 406.4 | 9.53 | 12.70 | +2.4 / -0.8 | +22.5% / +22.5% |
| 18 | 450 | 457 | 9.53 | 12.70 | +2.4 / -0.8 | +22.5% / +22.5% |
Swipe sideways to see the full table.
Every wall may run up to 12.5% under nominal. From NPS 3 upward, A312 allows +22.5% over nominal when t/D, the wall divided by the OD, is 5% or below, and +15.0% above that, which is why the heavier walls on the smaller bores take the tighter limit. Bores from NPS 1/8 to 2-1/2 take +20.0% at any wall.
Stainless steel 347H seamless pipes outside the schedule table are made to drawing sizes between 6 and 1016 mm OD, in any wall from 1 mm to 65 mm and lengths to 18 m. No cut length is supplied short, and the overrun is limited to 6 mm.
Choosing Between 347H, 347 and 321H
TP347 and TP347H share their chromium and nickel ranges and the same niobium stabilization. TP347 has no carbon floor, a lower solution annealing temperature and no grain size rule, which suits welded lines where corrosion resistance after welding, rather than creep, drives the choice. For that duty, compare our stainless steel 347 seamless pipes.
Titanium does the stabilizing job in seamless stainless steel 321H pipe: A312 asks for titanium of at least 4 × (C + N), capped at 0.70%, with nickel at 9.0 to 12.0%. Its H-grade controls match those of TP347H, so the choice between the two usually comes down to the stabilizing element and the wall thickness.
Fabrication Notes for Seamless Stainless Steel 347H Pipe
Seamless stainless steel 347H pipe has no longitudinal seam, so the welds in a line are limited to its girth and branch joints. Because niobium holds the carbon, the heat-affected zone of each joint resists chromium carbide precipitation, the damage that sensitizes unstabilized grades. Pipe leaves our mill hot finished or cold finished, and each route has its own minimum solution temperature, as listed above.
Two A312 supplementary requirements apply only when your order names them. S6 is a stabilizing heat treatment at a temperature below the initial solution anneal, agreed between you and us. S7 calls for an intergranular corrosion test.
Industrial Uses of Stainless Steel 347H Seamless Pipes
Long hours at temperature under internal pressure, usually in welded spools, link the plants where 347H stainless steel seamless pipe is installed.
Oil and Gas Furnace and Offshore Lines
In oil and gas service, the grade is used for furnace connections, offshore drilling equipment and pipelines, where hot sections need creep strength together with resistance to carbide precipitation.
Petrochemical Refineries and Processing Units
Petroleum refineries and chemical processing units run 347H in hot process lines, because its resistance to corrosion and carbide precipitation keeps fabrication welds resistant to intergranular attack.
Marine and Offshore Piping Systems
Shipbuilders and offshore platform builders use 347H for engine room piping systems and platform equipment, choosing the grade for its resistance to seawater corrosion.
Packing and Dispatch of Seamless 1.4912 Stainless Steel Pipe
Bundles
Steel-strapped and wrapped against moisture, or boxed in timber crates for ocean shipment.
Marking
SML, ASTM A312 TP347H, the size and schedule or wall, and the heat number and heat-treatment lot on every length, with project marks added on request.
Ends
Plastic caps on beveled and threaded ends to protect the weld preparation and the threads.
Records
The EN 10204 3.1 (3.2 on request) certificate together with a 100% PMI record, heat treatment charts, the certificate for the raw material, roughness and dimensional check results, and test results from a government-approved laboratory; a third-party inspection report is arranged on request.
Destinations
Road deliveries within Thailand and sea freight to Vietnam, Malaysia, Singapore, the Philippines, Indonesia and India.
Delivery terms
FOB, CIF or CFR, matched to your contract.
What Seamless TP347H Pipe Costs per kg
ASTM A312 stainless steel 347H seamless pipe carries an indicative price of USD 4 to 7.5 per kg. Most of the figure comes from the nickel and niobium in the heat; the H-grade carbon window, grain size testing, heavy walls and small lots move a quote toward the top of the band. A size list with schedules and quantities brings a firm figure.
Indicative price, Stainless Steel 347H Seamless Pipes
USD 4 to 7.5 per kg
Indicative only. Send your sizes and specification to Thaida for a firm quotation.
- Outside diameter
- Wall thickness
- Schedule
- Quantity
- Testing and certification
- Nickel price
Manufacturer of Seamless WNR 1.4912 Pipe in Thailand
Our factory at 154 Moo.1 Map Phai, Ban Bueng, Chonburi 20170, Thailand, makes every seamless 1.4912 stainless steel pipe order, from small-bore schedule sizes to heavy-wall drawing dimensions. Our office at 89/18 Moo.15 Enterprize Park, Bangna-Trad Road, Bang Kaeo, Bang Phli, Samut Prakan 10540, Thailand, handles the commercial and technical correspondence. The quotation states whether your stainless steel 347H seamless pipes ship from stock or from a new production run.
Factory154 Moo.1 Map Phai, Ban Bueng,
Chonburi 20170, Thailand
Chonburi 20170, Thailand
Office89/18 Moo.15 Enterprize Park, Bangna-Trad Road,
Bang Kaeo, Bang Phli, Samut Prakan 10540, Thailand
Bang Kaeo, Bang Phli, Samut Prakan 10540, Thailand
Exporting to
- Singapore
- Malaysia
- Vietnam
- Indonesia
- Philippines
- India
FAQ: Specifying Grade 347H
Why does A312 give TP347H a different cooling rule from TP347?
Because A312 lists TP347H separately in its annealing table, with a plain rule: quench in water or cool rapidly by other means. TP347, annealed at 1040 °C, carries a note tying its cooling rate to A262 Practice E capability. For TP347H, that test is run only when you order Supplementary Requirement S7.
Does wall thickness change the strength minimums of TP347H?
No. ASTM A312 gives TP347H a single strength level, 515 MPa (tensile) and 205 MPa (yield), whatever the wall. That matters for heavy walls: seamless TP321H drops to 480 MPa and 170 MPa above 9.50 mm, so an NPS 16 Sch 80S line (12.70 mm wall) designed on TP347H minimums cannot simply switch to TP321H.
Is seamless WNR 1.4912 pipe an exact match for UNS S34709?
No, it is a close match. EN 10216-5 sets 1.4912 at 9.0 to 12.0% nickel and niobium from ten times carbon up to 1.20%; ASTM A312 allows TP347H 9.0 to 13.0% nickel and niobium from eight times carbon up to 1.0%. If your drawing demands the EN limits as well, say so at inquiry.
Can seamless TP347H pipe be installed where a line class calls for TP347?
Only if the heat also meets TP347. That grade caps carbon at 0.08% and needs niobium of at least ten times the carbon, up to 1.00%, while TP347H allows carbon up to 0.10% with niobium from eight times carbon. Name both grades at inquiry so the heat analysis can be confirmed against each before dispatch.
Can transverse tension tests be added to large-bore 347H seamless pipe?
Yes, for NPS 8 and larger, through Supplementary Requirement S2. One transverse tension test is taken from one end of 10% of the lengths in each heat, and each specimen must meet 515 MPa tensile, 205 MPa yield and 25% transverse elongation. Smaller bores are covered by the standard lot tests only.
How is each length of 347H seamless pipe traced to its heat treatment?
ASTM A312 requires TP347H marking to show the heat-treatment lot identification alongside the heat number. That lot number links each length to its solution anneal record, its grain size result and its tension test on the EN 10204 3.1 (3.2 on request) certificate, so every length can be matched to the results that cover it.
Request a Quote for Stainless Steel 347H Seamless Pipes
or email sales@thaida.co.th