Power Plant Boiler and Heater Lines
Boiler and heater piping in power plants carries high-pressure steam for long periods. 321H is ordered for these lines when stress-rupture strength, not room-temperature strength, decides the schedule.
ASTM A312 / ASME SA-312 / UNS S32109 / W.Nr. 1.4878
Stainless Steel 321H Seamless Pipes Manufacturer in Thailand
Our Ban Bueng, Chonburi mill in Thailand produces ASTM A312 TP321H stainless steel seamless pipes, and Thaida Stainless Steel Manufacturing (Thailand) Co., Ltd. supplies them for steam, power and hot process lines designed on creep and stress-rupture strength. Designated UNS S32109 and EN 1.4878, the grade is the controlled-carbon, titanium-stabilized H version of 321 within the stainless steel seamless pipes family we produce. Our Bang Phli, Samut Prakan office prepares the heat-treatment and grain size records that go with each order.
Stainless Steel 321H seamless pipeUNS S32109 / W.Nr. 1.4878
- 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
Specification Sheet: TP321H Seamless Pipe
Lines can be sized on NPS and schedule or on a drawing OD and wall. Hot or cold finishing comes first, followed by the A312 solution anneal set for that route.
- Standard
- ASTM A312 / ASME SA-312
- Grade
- TP321H (UNS S32109)
- WNR
- 1.4878
- 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 NPS 30 in Schedules 5S, 10S, 40S and 80S (ASME B36.19), or OD and wall to drawing
- Manufacturing Route
- 1Seamless
- 2Hot finished or cold finished
- Solution Annealing
- 1100 °C (2000 °F) min cold finished; 1050 °C (1925 °F) min hot finished; water quenched or rapidly cooled
- Grain Size
- ASTM No. 7 or coarser
- End Type
- Plain endbeveled end, threaded (Schedules 40S and 80S)
- Surface Finish
- Pickled and passivatedbright annealed (BA), polished, brushed or mirror
- Test Certificate
- EN 10204 3.13.2 on request
TP321H is governed by ASTM A312 / ASME SA-312, which groups it with the H grades intended for creep and stress-rupture service. Sizes outside the A312 dimension table are allowed, provided the pipe satisfies the rest of the specification.
Each length of ASTM A312 TP321H stainless steel seamless pipe is either hydrotested or examined by a nondestructive electric method. Tension and flattening tests are run lot by lot, and every heat-treatment lot gets its own grain size determination. Certification follows EN 10204 3.1 (3.2 on request). Two extras apply only when ordered: inspection by a third party, available on request, and the A312 S7 intergranular corrosion test (ASTM A262 Practice E).
Seamless S32109 Stainless Steel Pipe: Heat Analysis Limits
The heat analysis of each seamless S32109 stainless steel pipe must fall within these TP321H limits from ASTM A312:
- CrChromium, 17.0 to 19.0
- NiNickel, 9.0 to 12.0
- TiTitanium, 4 × (C + N) min, 0.70 max
- MnManganese, 2.00 max
- SiSilicon, 1.00 max
UNS S32109321H
| Element | TP321H (UNS S32109), % |
|---|---|
| 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 12.0 |
| Ti (Titanium) | 4 × (C + N) min, 0.70 max |
| N (Nitrogen) | 0.10 max |
Carbon is held inside a window rather than under a cap, and titanium is tied to carbon plus nitrogen at four times their sum, one step below the five-times rule for TP321. Because titanium combines with carbon in preference to chromium, chromium carbide is kept off the grain boundaries during welding and hot service.
UNS S32109 Seamless Pipe Strength Minimums
Seamless TP321H has two sets of strength minimums in ASTM A312, divided at a nominal wall of 9.50 mm (0.375 in.). Each lot of 321H stainless steel seamless pipe is tension tested, and results are judged against the set that matches the ordered wall.
| Property | Wall up to 9.50 mm | Wall over 9.50 mm |
|---|---|---|
| Tensile Strength, min | 515 MPa (75 ksi) | 480 MPa (70 ksi) |
| Yield Strength, min | 205 MPa (30 ksi) | 170 MPa (25 ksi) |
| Elongation in 50 mm (2 in.), min, longitudinal | 35% | 35% |
| Elongation in 50 mm (2 in.), min, transverse | 25% | 25% |
Design allowables at operating temperature are set by the code your piping is built to, so name that code on the inquiry.
Designations of Grade 321H Across Standards
Drawings from the USA, Europe, Japan, China and Russia, together with the international (ISO) name, identify grade 321H as follows.
- USA (ASTM / ASME)TP321H (ASTM A312 / ASME SA-312)
- USA (UNS)S32109
- Europe (EN / WNR)1.4878
- ISOX8CrNiTi18-10
- Japan (JIS)SUS321HTP
- China (GB)S32169 (ISC) / 07Cr19Ni11Ti
- Russia (GOST)12X18H10T
Engineers working from European drawings can order seamless WNR 1.4878 pipe directly; the line item is offered and supplied as ASTM A312 TP321H (UNS S32109), with 1.4878 serving only as a cross-reference.
Schedule Sizes and Range of SS 321H Seamless Pipe
SS 321H seamless pipe is produced with an OD of 6 to 1016 mm and a wall of 1 to 65 mm, with lengths reaching 18 m, either to A312 schedules or to drawing dimensions. Representative A312 schedule sizes, with nominal wall in mm:
| NPS | OD (mm) | Sch 10S | Sch 40S | Sch 80S |
|---|---|---|---|---|
| 1-1/2 | 48.3 | 2.77 | 3.68 | 5.08 |
| 3-1/2 | 101.6 | 3.05 | 5.74 | 8.08 |
| 8 | 219.1 | 3.76 | 8.18 | 12.70 |
| 16 | 406.4 | 4.78 | 9.53 | 12.70 |
| 20 | 508 | 5.54 | 9.53 | 12.70 |
| 24 | 610 | 6.35 | 9.53 | 12.70 |
Swipe sideways to see the full table.
Definite cut lengths carry a tolerance of plus 6 mm (1/4 in.) and minus nothing.
OD and Wall Tolerance Bands
The OD and wall tolerances for A312 pipe sit together in the table below. Wall under-tolerance is 12.5% of nominal at every size, while the over-tolerance depends on NPS and on t/D, the ratio of wall thickness to outside diameter.
| NPS | OD Tolerance (mm) | Wall, t/D up to 5% | Wall, t/D over 5% |
|---|---|---|---|
| 1/8 to 1-1/2 | +0.4 / -0.8 | +20.0% / -12.5% | +20.0% / -12.5% |
| Over 1-1/2 to 2-1/2 | +0.8 / -0.8 | +20.0% / -12.5% | +20.0% / -12.5% |
| 3 to 4 | +0.8 / -0.8 | +22.5% / -12.5% | +15.0% / -12.5% |
| Over 4 to 8 | +1.6 / -0.8 | +22.5% / -12.5% | +15.0% / -12.5% |
| Over 8 to 18 | +2.4 / -0.8 | +22.5% / -12.5% | +15.0% / -12.5% |
| Over 18 to 26 | +3.2 / -0.8 | +22.5% / -12.5% | +15.0% / -12.5% |
| Over 26 to 34 | +4.0 / -0.8 | +22.5% / -12.5% | +15.0% / -12.5% |
| Over 34 to 48 | +4.8 / -0.8 | +22.5% / -12.5% | +15.0% / -12.5% |
Swipe sideways to see the full table.
Choosing Among Grades 321H, 321 and 347H
Against TP321, the H grade keeps the chromium, nickel and nitrogen limits but differs mainly in the carbon window and titanium ratio shown above, a higher solution anneal for each finishing route and a grain size of No. 7 or coarser. In seamless walls over 9.50 mm the tensile minimum also differs slightly: 480 MPa for TP321H against 485 MPa for TP321, with 170 MPa yield for both. Stay with stainless steel 321 seamless pipes when weld-zone corrosion resistance drives the selection and creep does not enter the design; move to 321H once stress-rupture strength sets the wall.
Niobium-stabilized 347H seamless pipes follow the same H-grade rules for carbon, grain size and annealing. Their stabilizer is niobium at eight times the carbon or more, capped at 1.0%, and their nickel may reach 13.0%. Wall thickness can tip the choice: A312 cuts the minimums above 9.50 mm for the two 321 grades only, so a heavy-wall TP347H line is still checked against the full 515 MPa (75 ksi) and 205 MPa (30 ksi).
Joining and Weld Zones in Seamless 1.4878 Stainless Steel Pipe
Joints in 321H lines are butt welds, flanges or threads, with threads limited to Schedules 40S and 80S, so beveled ends are the usual order and plain ends are deburred square. Titanium stabilization keeps chromium carbide formation low in each heat-affected zone, which protects the welds of seamless 1.4878 stainless steel pipe against intergranular attack. Every 321H stainless steel seamless pipe is heat treated to A312 before dispatch; where your specification also asks for a stabilizing heat treatment, list A312 Supplementary Requirement S6 on the order.
Service Duties for ASTM A312 TP321H Stainless Steel Seamless Pipe
Seamless stainless steel 321H pipe belongs in lines that stay under pressure at high temperature long enough for creep strength to fix the wall thickness.
Petrochemical Plants
Petrochemical units run 321H piping at elevated temperature under continuous thermal cycling. Titanium keeps the welds resistant to intergranular corrosion while the controlled carbon supplies strength in high-temperature heat-transfer service.
Oil and Gas Processing
Refinery piping around heat exchangers and furnaces sees high heat and aggressive process streams together. SS 321H seamless pipe for these runs follows the NPS and schedule of the refinery line class.
Chemical Processing
Hot, corrosive chemicals move between distillation and separation columns through welded 321H lines. Titanium stabilization guards each heat-affected weld zone against intergranular corrosion during long hot service.
Packing, Marking and Dispatch
Bundling
Stainless steel 321H seamless pipes in small bores are strapped in wrapped bundles, while larger NPS and heavy walls are packed in wooden export crates.
Identification
A312 requires SML, the heat number and the heat-treatment lot ID on TP321H, and we add the size and our own mark to every UNS S32109 seamless pipe length.
End caps
Plastic caps close plain, beveled and threaded ends against dirt and moisture.
Lot records
Heat treatment charts and 100% PMI results are grouped by heat-treatment lot under the EN 10204 3.1 (3.2 on request) certificate; a third-party report is added only to orders that ask for one.
Routes and terms
Trucked to sites in Thailand or shipped by sea to Singapore, Malaysia, Vietnam, Indonesia, the Philippines and India, on FOB, CIF or CFR terms.
Price Guide for Seamless Stainless Steel 321H Pipe
For budgeting, ASTM A312 stainless steel 321H seamless pipe carries an indicative USD 3.75 to 7 per kg. The base is the same nickel and titanium cost as TP321, and the high-temperature requirements of the H grade (carbon window, grain size, solution anneal) add to it. Heavy walls, large OD and small boiler or refinery lots price highest within the range; a size list brings a firm offer.
Indicative price, Stainless Steel 321H Seamless Pipes
USD 3.75 to 7 per kg
Indicative only. Send your sizes and specification to Thaida for a firm quotation.
- Outside diameter
- Wall thickness
- Nickel price
- Titanium price
Where Our Stainless Steel 321H Seamless Pipes Are Made
Stainless steel 321H seamless pipes are finished, annealed, tested and marked at our factory, 154 Moo.1 Map Phai, Ban Bueng, Chonburi 20170, Thailand. Our sales and documentation team at 89/18 Moo.15 Enterprize Park, Bangna-Trad Road, Bang Kaeo, Bang Phli, Samut Prakan 10540, Thailand, answers inquiries and follows each order of ASTM A312 stainless steel 321H seamless pipe through to dispatch.
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
Frequently Asked Questions
Does the finishing route change the annealing temperature of seamless 321H?
Yes. A312 asks for at least 1100 °C (2000 °F) on cold finished TP321H and at least 1050 °C (1925 °F) on hot finished pipe, followed by water quenching or another rapid cooling method. A312 also permits seamless pipe to be quenched directly after hot forming instead of reheating, provided it has not cooled below that minimum.
Which strength level applies to NPS 8 Schedule 80S pipe in grade 321H?
The lower one. Its 12.70 mm wall exceeds 9.50 mm, so under A312 the minimum tensile drops to 480 MPa (70 ksi) and the minimum yield to 170 MPa (25 ksi). NPS 8 Schedule 40S, at 8.18 mm, keeps 515 MPa (75 ksi) and 205 MPa (30 ksi). Base heavy-wall design checks on the lower pair.
How do I confirm the grain size of a seamless 321H lot?
Check the grain size entry on the certificate. TP321H must show ASTM No. 7 or coarser, a figure obtained by the ASTM E112 method for every heat-treatment lot. Since the result belongs to the lot, compare the lot identification marked on each length with the lot named on the certificate.
Is seamless WNR 1.4878 pipe covered by EN 10216-5?
No. EN 10216-5 has no 1.4878 grade; its titanium-stabilized creep grades carry other numbers. Your order is therefore made and certified to ASTM A312 TP321H (UNS S32109), and 1.4878 (X8CrNiTi18-10) serves only as a cross-reference. If the project specification insists on an EN 10216-5 grade, let us review it before ordering.
Should 321H for a superheater be ordered as pipe or as tube?
It depends on how the drawing sizes it. Steam headers and connecting lines dimensioned by NPS and schedule take seamless pipe to ASTM A312. Superheater coils and exchanger bundles drawn to an exact OD and wall belong with our stainless steel 321H seamless tubes, made in the same grade.
Does a TP321H heat also meet the TP321 limits?
Only if its heat analysis satisfies both sets. Carbon must fall between 0.04 and 0.08%, since TP321 caps it at 0.08%. Titanium must reach 5 × (C + N), the TP321 rule, not just the 4 × (C + N) that TP321H accepts. Check both figures on the heat analysis before treating a heat as TP321 material.
Request a Quote for Stainless Steel 321H Seamless Pipes
or email sales@thaida.co.th