Power Generation Steam Lines
Main steam branches, superheater connections and turbine drain lines in power plants are welded on site and heat up with every start; niobium stabilization keeps those joints resistant to intergranular corrosion.
ASTM A312 / ASME SA-312 / UNS S34700 / W.Nr. 1.4550
Stainless Steel 347 Seamless Pipes Manufacturer in Thailand
We are Thaida Stainless Steel Manufacturing (Thailand) Co., Ltd., producer of niobium-stabilized stainless steel 347 seamless pipes to ASTM A312 TP347 in Ban Bueng, Chonburi, Thailand, for welded process, steam and hot-gas lines that run at elevated temperature for long periods. UNS S34700 and W.Nr. 1.4550 (X6CrNiNb18-10) identify the grade, one of the stabilized options in our stainless steel seamless pipe portfolio. Technical queries and quotations are answered from Bang Phli, Samut Prakan, where our sales office is based.
Stainless Steel 347 seamless pipeUNS S34700 / W.Nr. 1.4550
- 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
SS 347 Seamless Pipe: Grade, Range and Delivery Condition
We hot finish or cold finish each SS 347 seamless pipe, solution anneal it, and then apply the surface your order names. Sizes can follow the NPS and schedule of your line class or the exact OD and wall on a drawing.
- Standard
- ASTM A312 / ASME SA-312
- Grade
- TP347 (UNS S34700)
- W.Nr.
- 1.4550
- Outside Diameter
- 6 to 1016 mm
- Wall Thickness
- 1 to 65 mm
- Length
- Up to 18 mcut lengths to order
- Dimensions
- NPS 1/8 to 30Sch 5S, 10S, 40S and 80S to ASME B36.19M, or OD and wall to drawing
- End Type
- Plain endbeveled end, threaded (Sch 40S and 80S)
- Surface Finish
- Pickled and passivatedbright annealed (BA), polished, brushed or mirror
- Delivery Condition
- Hot finished or cold finished, solution annealed at 1040 °C (1900 °F) minimum and rapidly cooled
- Test Certificate
- EN 10204 3.13.2 on request
When the job is a heat exchanger bundle or an instrument run ordered to tube OD tolerances, ask for our stainless steel 347 seamless tubes.
ASTM A312 / ASME SA-312 governs each ASTM A312 stainless steel 347 seamless pipe we produce; its scope is austenitic stainless pipe intended for high-temperature and general corrosive service. We supply the seamless product, and every length is marked SML. Schedule sizes are taken from ASME B36.19M, while A312 also accepts other diameters and walls that satisfy its remaining clauses.
Hydrostatic or nondestructive electric: one of these two tests is applied to each TP347 length, and we choose which unless your order fixes it. A312 also calls for tensile testing per lot of no more than 100 pipes and for flattening 5% of each lot. Results are issued on an EN 10204 3.1 (3.2 on request) certificate, backed by 100% PMI, raw materials certificates, heat treatment charts and a report from a government-approved laboratory. If your project names an independent inspector, third-party inspection is available on request.
Chemical Limits on Every UNS S34700 Seamless Pipe Heat
ASTM A312 Table 1 fixes the TP347 chemistry below; the certificate for each UNS S34700 seamless pipe heat prints the actual analysis beside it.
- CrChromium, 17.0 to 19.0
- NiNickel, 9.0 to 13.0
- NbNiobium, 10 × C min, 1.00 max
- MnManganese, 2.00 max
- SiSilicon, 1.00 max
UNS S34700347
| Element | TP347 Limit (%) |
|---|---|
| C (Carbon) | 0.08 max |
| 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) | 10 × C min, 1.00 max |
How Niobium Stabilizes Grade 347
When an unstabilized austenitic steel is welded or held in the sensitizing range, chromium carbides can form along its grain boundaries and leave them open to intergranular attack. Niobium combines with carbon first. With the carbon tied up, chromium remains available to protect the boundaries next to every weld.
Seamless WNR 1.4550 Pipe Strength and Elongation
Every lot of seamless WNR 1.4550 pipe is tension tested, and the measured values sit beside these A312 minimums on the certificate. Hardness is not among the TP347 requirements.
| Property | Value | Unit |
|---|---|---|
| Tensile Strength, min | 515 (75) | MPa (ksi) |
| Yield Strength, min | 205 (30) | MPa (ksi) |
| Elongation in 2 in. or 50 mm (or 4D), min, longitudinal | 35 | % |
| Elongation in 2 in. or 50 mm (or 4D), min, transverse | 25 | % |
Stainless Steel 347 Cross-Reference Designations
Grade 347 appears under these names in national and international standards systems.
- USA (ASTM / ASME)ASTM A312 / ASME SA-312 TP347
- USA (UNS)UNS S34700
- Europe (EN / W.Nr.)1.4550 / X6CrNiNb18-10
- Japan (JIS)SUS347
- China (GB)S34778 (ISC) / 06Cr18Ni11Nb
- Russia (GOST)08X18H12Б
Wall Thickness by Schedule: Seamless Stainless Steel 347 Pipe
Seamless stainless steel 347 pipe is produced across a 6 mm to 1016 mm OD envelope, with walls between 1 mm and 65 mm and single pieces as long as 18 m. A312 Table X1.1 covers NPS 1/8 through NPS 30 in Schedules 5S, 10S, 40S and 80S. The rows below give nominal walls in mm for bores that steam and process headers often use:
| NPS | OD (mm) | Sch 5S | Sch 10S | Sch 40S | Sch 80S |
|---|---|---|---|---|---|
| 1/2 | 21.3 | 1.65 | 2.11 | 2.77 | 3.73 |
| 1 | 33.4 | 1.65 | 2.77 | 3.38 | 4.55 |
| 2-1/2 | 73.0 | 2.11 | 3.05 | 5.16 | 7.01 |
| 6 | 168.3 | 2.77 | 3.40 | 7.11 | 10.97 |
| 16 | 406.4 | 4.19 | 4.78 | 9.53 | 12.70 |
| 24 | 610 | 5.54 | 6.35 | 9.53 | 12.70 |
Swipe sideways to see the full table.
Wall, OD and Length Tolerances under ASTM A312
A312 Table 3 sets the wall limits. Thin side: 12.5% under nominal at any size. Heavy-side limits run 20.0% for NPS 1/8 to 2-1/2 and, from NPS 3, 22.5% or 15.0% depending on whether the wall is 5% of the OD or less, or thicker. Diameter variations permitted for A312 pipe, by DN and NPS band:
| DN | NPS | OD Tolerance (mm) |
|---|---|---|
| 6 to 40 | 1/8 to 1-1/2 | +0.4 / -0.8 |
| Over 40 to 100 | Over 1-1/2 to 4 | +0.8 / -0.8 |
| Over 100 to 200 | Over 4 to 8 | +1.6 / -0.8 |
| Over 200 to 450 | Over 8 to 18 | +2.4 / -0.8 |
| Over 450 to 650 | Over 18 to 26 | +3.2 / -0.8 |
| Over 650 to 850 | Over 26 to 34 | +4.0 / -0.8 |
| Over 850 to 1200 | Over 34 to 48 | +4.8 / -0.8 |
An ordered cut length is the minimum; a piece may be up to 6 mm (1/4 in.) longer.
Stabilized Alternatives: 321 and 347H
Grade 347 and titanium-stabilized 321 seamless pipes protect welds by the same principle with different elements. For welded piping that will spend years in the sensitizing range, 347 is the stabilized grade usually favored over 321, and niobium also gives it marginally higher tensile and yield strength than 321 at elevated temperature.
Where sustained load at high temperature sizes the wall, seamless 347H pipes add a carbon range of 0.04 to 0.10%, a grain size of ASTM 7 or coarser and a higher minimum solution anneal: 1100 °C for cold finished and 1050 °C for hot finished pipe. Standard TP347 caps carbon at 0.08% instead.
347 Stainless Steel Seamless Pipe in Power, Refining and Process Plants
347 stainless steel seamless pipe earns its place in welded systems that spend long periods hot and still need sound, corrosion-resistant joints.
Refinery and Petrochemical Process Piping
Hot hydrocarbon lines around fired heaters, reactors and fractionation units take 347 in NPS and schedule sizes matched to the line class, with ends beveled for field butt welding.
Chemical Plant Process Lines
Batch process lines in chemical plants cross the sensitizing range during every heat-up and cool-down. Certified niobium and carbon figures for every heat let inspectors confirm stabilization before installation.
Oil and Gas Facilities
Hot gas and condensate lines, plus utility headers on oil and gas processing plants, run in Sch 40S and 80S, where A312 wall tolerances and hydrostatic or electric testing support the pressure design.
Aerospace and Engine Test Facilities
Exhaust ducting and hot-gas transfer piping on engine test stands and aerospace ground facilities are built from thin-wall Sch 5S and 10S grade 347, joined by butt welds along each run.
Food Processing Utilities
Steam, hot water and clean-in-place supply lines in food processing plants use 347 in bright annealed or polished finish, ordered in exact lengths to cut site work.
How We Pack Seamless 1.4550 Stainless Steel Pipe
Bundles
Small-bore lengths are strapped together and sleeved against dust and salt air; large NPS and polished pipe travel in seaworthy wooden cases.
Identification
Every seamless 1.4550 stainless steel pipe carries SML, its heat number, our mark, NPS or OD and schedule or average wall, with ET or UT recorded where that test was applied and NH on any length shipped without the hydrostatic test.
Ends
Every length is capped in plastic to keep the bore clean, and beveled ends are guarded against knocks in handling.
Factory finishing
Cutting to length, beveling and threading of Sch 40S and 80S ends are completed before loading.
Sales terms
Quoted on FOB, CIF or CFR basis.
Documents in the cargo pouch
One EN 10204 3.1 (3.2 on request) certificate per heat, the packing list and, where ordered, the inspection report.
What ASTM A312 TP347 Stainless Steel Seamless Pipe Costs per kg
For ASTM A312 TP347 stainless steel seamless pipe, the indicative band is USD 3.5 to 6.5 per kg. Nickel at 9.0 to 13.0% sets the base cost and niobium stabilization places 347 slightly above 321; within the range, NPS, wall, finish, order size and added tests fix the figure. Thaida confirms a firm price against your size list.
Indicative price, Stainless Steel 347 Seamless Pipes
USD 3.5 to 6.5 per kg
Indicative only. Send your sizes and specification to Thaida for a firm quotation.
- Outside diameter
- Wall thickness
- Finish
- Quantity
- Testing and certification
- Nickel price
Where We Make and Ship Grade 347
At 154 Moo.1 Map Phai, Ban Bueng, Chonburi 20170, Thailand, our mill hot or cold finishes, solution anneals and tests stainless steel 347 seamless pipes. Our commercial team works from 89/18 Moo.15 Enterprize Park, Bangna-Trad Road, Bang Kaeo, Bang Phli, Samut Prakan 10540, Thailand, handling offers, order follow-up and export paperwork. Trucks deliver within Thailand, and export consignments sail for Singapore, Malaysia, Vietnam, Indonesia, the Philippines and India.
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 on Seamless S34700 Stainless Steel Pipe
How much niobium must TP347 seamless pipe contain?
The minimum is a ratio, not a fixed percentage: ASTM A312 requires the niobium content to be not less than ten times the carbon content and not more than 1.00%. A heat with lower carbon needs less niobium. The certificate for each seamless S34700 stainless steel pipe heat reports carbon and niobium together, so the ratio can be checked.
How does niobium stabilization in TP347 differ from titanium in TP321?
TP321 ties titanium to carbon plus nitrogen, at 5 × (C + N) minimum and 0.70% maximum, while TP347 ties niobium to carbon alone. More nitrogen raises the titanium a TP321 heat needs but leaves the TP347 niobium minimum unchanged. Nickel differs too: 9.0 to 13.0% for TP347 against 9.0 to 12.0% for TP321.
Is columbium (Cb) on a 347 data sheet the same as niobium?
Yes. ASTM A312 states that niobium (Nb) and columbium (Cb) are alternative names for the same element, so a data sheet asking for Cb-stabilized 347 calls for the niobium limits in the TP347 chemistry table. Name ASTM A312 TP347 in your inquiry and the heat analysis will be checked against that niobium rule.
Does TP347 seamless pipe need a grain size test like TP347H?
No. TP347 is absent from the A312 grain size table, so no grain size result is required for it. Its H-grade counterpart, TP347H, must show grain size 7 or coarser, measured on each heat-treatment lot, which is one reason a creep-designed line names TP347H rather than TP347.
Which schedules does A312 list for NPS 30 seamless 347 pipe?
Only Sch 5S and 10S. A312 Table X1.1 gives NPS 30 (762 mm OD) a 6.35 mm wall in Sch 5S and 7.92 mm in Sch 10S, with no 40S or 80S entry. A heavier wall at that diameter is produced to your drawing, within our 1 mm to 65 mm wall range.
Will TP347 limits satisfy a drawing that names W.Nr. 1.4550?
Not automatically. EN 10216-5 caps phosphorus in 1.4550 (X6CrNiNb18-10) at 0.040% against 0.045% for TP347, and its base nickel and sulfur limits (9.0 to 12.0%, 0.015% max) are tighter than TP347's 13.0% and 0.030%. Treat 1.4550 as a cross-reference, and state it at inquiry if a seamless WNR 1.4550 pipe heat must satisfy both.
Is TP347 seamless pipe hot finished or cold finished?
Either route is allowed; A312 leaves the choice to the manufacturer unless your order fixes it. Each route ends in a minimum 1040 °C (1900 °F) solution anneal with rapid cooling, or a direct quench from hot forming. Hot finished pipe is pickled free of scale, while bright annealed cold finished pipe needs no pickling under A312.
Request a Quote for Stainless Steel 347 Seamless Pipes
or email sales@thaida.co.th