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SS 321H Seamless Tube
321H seamless tube carries no longitudinal weld, so there's no heat-affected zone to act as a creep-crack initiation site. We supply it to ASTM A213 / ASME SA-213 for boiler and superheater service.
Stainless Steel 321H Tube Manufacturer in India
MLTI Private Limited, formerly known as Moonlight Tube Industries, manufactures and exports stainless steel 321H tubes in Gujarat, India. We've been producing austenitic tubes on these mills since 2008 and have a combined stock capacity of 8,000 MT per year. Stainless steel 321H tube is the titanium-stabilised, higher-carbon form of Type 321, listed as UNS S32109. Carbon is held to 0.04 to 0.10%, chromium to 17.0 to 19.0%, and nickel to 9.0 to 12.0%, with titanium at four times carbon plus nitrogen under ASTM A213 and five times under ASTM A249, 0.70% maximum in both. In the annealed condition, the grade certifies a minimum tensile strength of 515 MPa (75 ksi), a yield floor of 205 MPa, and 35% elongation. Grain size is controlled to ASTM No. 7 or coarser, which increases creep-rupture strength above plain 321. European drawings refer to the same material as 1.4878.
We produce 321H seamless tube to ASTM A213 / ASME SA-213 and 321H welded tube, ERW included, to ASTM A249 / ASME SA-249; general-service 321 stainless steel tubing follows ASTM A269. Both seamless and welded options are available to meet different application requirements. Round sections cover 12.7 mm to 101.6 mm outside diameter on gauges from 19 SWG to 10 SWG, in lengths reaching 24 metres, with box sections made to order. Superheater, reheater, and heat-exchanger service accounts for most of this grade. Our plant is certified to ISO 14001 and ISO 45001. For product and pressure work, we hold material manufacturer approval under Annex I, 4.3 of PED 2014/68/EU, plus IBR approval and EIL vendor approval.
Stainless Steel 321H Tube Specifications
The table below lists all ordering parameters for the 321H tube in all forms (round, square, and rectangular), including specifications, dimensions, grain size, finish, and delivery.
| Parameter | Value |
|---|---|
| Applicable standards | ASTM A213 / ASME SA-213: Seamless Ferritic and Austenitic Alloy-Steel Boiler, Superheater, and Heat-Exchanger Tubes; ASTM A249 / ASME SA-249: Welded Austenitic Steel Boiler, Superheater, Heat-Exchanger, and Condenser Tubes; ASTM A554: Welded Stainless Steel Mechanical Tubing |
| Manufacturing processes | Seamless (ASTM A213); welded, cold worked and solution-annealed (ASTM A249); cold-drawn |
| Section | Round, square, rectangular |
| Outside diameter, round | 12.7 mm to 101.6 mm (1/2" to 4") |
| Wall thickness, round | 1.02 mm to 3.4 mm (19 SWG to 10 SWG) |
| Square section | 12 x 12 mm to 100 x 100 mm, wall 1.0 mm to 6.0 mm |
| Rectangular section | 13 x 25 mm to 100 x 50 mm, wall 1.0 mm to 6.0 mm |
| Length | To 24 metres round, to 12 metres box section, cut to order |
| Delivery condition | Solution annealed (round tube to ASTM A213 / ASTM A249); box section as-welded or cold-reduced. |
| Grain size | ASTM E112 No. 7 or coarser |
| Finish | Pickled and passivated; bright annealed; polished to order |
Stainless Steel 321H Tube Chemical Composition
The chemical composition of Type 321H Tube as per ASTM A213/ ASME SA-213 has been given in the table below.
| Element | Composition, % by mass |
|---|---|
| Carbon (C) | 0.04 – 0.10 |
| Manganese (Mn) | 2.00 max |
| Phosphorus (P) | 0.045 max |
| Sulphur (S) | 0.030 max |
| Silicon (Si) | 1.00 max |
| Chromium (Cr) | 17.0 – 19.0 |
| Nickel (Ni) | 9.0 – 12.0 |
| Titanium (Ti) | 4 x (C + N) min, 0.70 max |
| Nitrogen (N) | Not specified in ASTM A213 for TP321H; a 0.10% maximum can be applied by agreement at the order stage. |
| Iron (Fe) | Balance |
Stainless Steel 321H Tube Mechanical Properties
The mechanical properties governing acceptance of the ASTM A213 TP321H tube are recorded in the table that follows.
| Property | Value |
|---|---|
| Tensile strength, min | 515 MPa (75 ksi) |
| Yield strength, 0.2% offset, min | 205 MPa (30 ksi) |
| Elongation in 50 mm, min | 35% |
| Hardness, max | 90 HRB |
Room-temperature strength matches plain 321 exactly. Separation shows up in creep rupture: ASTM A213 states that grades carrying the letter H meet different requirements, delivering higher creep-rupture strength. The 90 HRB ceiling applies to the annealed condition; hardness above that comes only from cold work.
Stainless Steel 321H Tube Equivalent Grades
TP321H is registered as UNS S32109, and each national standard carries its own designation for the same material. The equivalent designations are matched in the table below.
| Country / Standard | Designation |
|---|---|
| USA (UNS) | UNS S32109 |
| Europe (EN/W.Nr.) | 1.4878, X8CrNiTi18-10 |
Continental buyers order 1.4878 tubing by that number alone.
Stainless Steel 321H Tube Forms and Types
SS 321H tube leaves our mills by two manufacturing routes and in three cross-sections. Seamless construction is covered first, then welded/ ERW, then the round, square, and rectangular profiles.
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SS 321H Welded (ERW) Tube
A welded tube begins as a slit strip, formed to round and seam-welded, then solution annealed to ASTM A249 / ASME SA-249. That specification names superheaters and reheaters as the H-grade duty. A 321H ERW tube is the lower-cost route. ASTM A249 attaches two conditions to it: the seam is welded without filler metal, and the weld is cold worked before the final solution anneal.
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SS 321H Round Tube
The round section is our highest-volume product, rolled across eleven diameters between 12.7 mm and 101.6 mm. Heat-exchanger bundles, boiler banks, and instrument runs all draw on 321H stainless steel tubes in round form.
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SS 321H Square Tube
Our SS 321H square tube is a welded box section, 12 x 12 mm through 100 x 100 mm, with walls of 1.0 mm to 6.0 mm, supplied as-welded or cold-reduced. Furnace framing and hot-gas support steelwork are the usual destinations.
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SS 321H Rectangular Tube
Rectangular box sections range from 13 x 25 mm to 100 x 50 mm, with walls of 1.0 mm to 6.0 mm. Fabricators specify SS 321H rectangular tube where a member carries a bending load about one axis.
Stainless Steel 321H Tube Sizes
Our stainless steel 321H tube sizes cover eleven round diameters plus box sections; the UNS S32109 tube is held in common gauges, with other gauges rolled to order. Diameters and their gauge bands appear in the table below.
Seamless SS 321H Tube Size Chart
| Size | OD (mm) | 10 BWG (3.40 mm) Weight/MTR | 12 BWG (2.77 mm) Weight/MTR | 14 BWG (2.11 mm) Weight/MTR | 16 BWG (1.65 mm) Weight/MTR | 18 BWG (1.25 mm) Weight/MTR | 19 BWG (1.07 mm) Weight/MTR |
|---|---|---|---|---|---|---|---|
| 1/2" | 12.7 | 0.78 | 0.68 | 0.55 | 0.45 | 0.35 | 0.31 |
| 5/8" | 15.875 | 1.05 | 0.89 | 0.72 | 0.58 | 0.45 | 0.39 |
| 3/4" | 19.05 | 1.31 | 1.11 | 0.88 | 0.71 | 0.55 | 0.47 |
| 1" | 25.4 | 1.85 | 1.55 | 1.21 | 0.97 | 0.74 | 0.64 |
| 1 1/4" | 31.75 | 2.38 | 1.98 | 1.54 | 1.23 | 0.92 | 0.81 |
| 1 1/2" | 38.1 | 2.91 | 2.41 | 1.87 | 1.48 | 1.13 | 0.97 |
| 2" | 50.8 | 3.98 | 3.28 | 2.53 | 2.00 | 1.52 | 1.31 |
| 2 1/2" | 63.5 | 5.04 | 4.15 | 3.19 | 2.52 | 1.91 | 1.64 |
| 3" | 76.2 | 6.11 | 5.01 | 3.85 | 3.04 | 2.30 | 1.98 |
| 3 1/2" | 88.9 | 7.18 | 5.88 | 4.51 | 3.55 | 2.69 | 2.31 |
| 4" | 101.6 | 8.24 | 6.75 | 5.17 | 4.07 | 3.08 | 2.65 |
SS 321H ERW Tube Size Chart
| Size | OD (mm) | 10 SWG (3.25 mm) Weight/Mtr | 12 SWG (2.64 mm) Weight/Mtr | 14 SWG (2.03 mm) Weight/Mtr | 16 SWG (1.63 mm) Weight/Mtr | 18 SWG (1.22 mm) Weight/Mtr | 19 SWG (1.02 mm) Weight/Mtr |
|---|---|---|---|---|---|---|---|
| 1/2" | 12.7 | 0.75 | 0.65 | 0.55 | 0.45 | 0.34 | 0.29 |
| 5/8" | 15.875 | 1.01 | 0.86 | 0.72 | 0.58 | 0.44 | 0.37 |
| 3/4" | 19.05 | 1.26 | 1.06 | 0.88 | 0.71 | 0.53 | 0.45 |
| 1" | 25.4 | 1.76 | 1.47 | 1.21 | 0.97 | 0.72 | 0.61 |
| 1 1/4" | 31.75 | 2.27 | 1.88 | 1.54 | 1.23 | 0.91 | 0.76 |
| 1 1/2" | 38.1 | 2.77 | 2.29 | 1.88 | 1.49 | 1.10 | 0.92 |
| 2" | 50.8 | 3.78 | 3.11 | 2.54 | 2.01 | 1.48 | 1.24 |
| 2 1/2" | 63.5 | 4.79 | 3.93 | 3.20 | 2.53 | 1.85 | 1.55 |
| 3" | 76.2 | 5.79 | 4.75 | 3.86 | 3.05 | 2.23 | 1.87 |
| 3 1/2" | 88.9 | 6.80 | 5.57 | 4.52 | 3.57 | 2.61 | 2.18 |
| 4" | 101.6 | 7.81 | 6.39 | 5.18 | 4.09 | 2.99 | 2.50 |
Note:
- SWG conversions are rounded. Order the millimetre wall you require, and we will confirm the nearest gauge.
- Tolerance follows the ordering specification rather than the grade. ASTM A213 tube is normally ordered to minimum wall, where the tolerance is all plus and none minus. Where an average wall is specified instead, A213 allows plus or minus 10% on cold-formed tubes; hot-formed tubes follow the wider band of A213. ASTM A249 sets plus or minus 10% of the nominal wall for all sizes.
Stainless Steel 321H Tube Industrial Applications
Four sectors account for most of the 321H stainless steel tubes, and each is described below with the equipment involved.
Thermal Power Generation
Superheater and reheater elements sit at the hottest point of a utility boiler, and a coarse-grained ASTM A213 TP321H tube holds its creep strength there.
Oil Refining and Petrochemicals
Refinery exchangers running hydrocarbon streams above 500°C take 321H heat exchanger tubes on the process side. The grade resists polythionic acid cracking during shutdown, which matters in hydrotreater service.
Chemical and Fertiliser Plant
Ammonia and nitric acid units pass hot process gas through stabilised austenitic tubes in waste-heat boilers and reformer convection banks. Chemical plants also specify 321 stainless steel tubing for jacketed vessel coils.
Aerospace and Engine Exhaust Fabrication
Exhaust manifolds, engine bleed lines and afterburner ducting use thin-wall 321H stainless steel tube, which welds without post-weld annealing and tolerates repeated thermal cycling.
Solution Annealing and Controlled Grain Size in 321H Tube
Coarse grain is a large part of that strength. Fewer boundaries per unit volume leave fewer paths for boundary sliding, so a No. 7 or coarser structure resists creep better than a fine grain. We reach it through a separate solution anneal after forming. ASTM A213 permits direct quenching from hot forming for most austenitic grades, but not for the H grades. Clause 6.2.2 requires the TP321H tube to be reheated to the specified heat-treatment temperature and held for the required time before quenching, so the solution anneal is always a separate operation. The standard sets a floor rather than a ceiling: hot-rolled ASTM A213 TP321H is solution-treated from 1925°F (1050°C). minimum and cold-worked ASTM A213 TP321H from 2000 °F (1100 °C) minimum. A213 also cautions that a solution treating temperatures above 1950°F (1065°C) may impair resistance to intergranular corrosion and later exposure to sensitising temperatures, and a purchaser can call for a lower-temperature stabilisation or re-solution anneal afterwards.
Stainless Steel 321H Tube vs 321 and 316 Tube: Selection Guide
Three questions settle the grade: operating metal temperature, chloride content of the stream, and the fabricator's machining and welding load.
When 321H Tube Replaces 321 Tube
Alloy 321H displaces 321 tubes once the sustained metal temperature passes roughly 538°C (1000°F). Below that, the extra carbon buys nothing. One heat certifies to both grades, provided carbon lands between 0.04% and 0.08% and titanium clears grade 321's stricter five-times multiplier.
321H Tube Against 316 Tube in Chloride Service
Chlorides are where Type 321H is the weaker choice. Titanium stabilisation doesn't help pitting resistance, and the grade holds no molybdenum, so warm chloride streams and sulphuric acid duty belong to 316 tube. In hot hydrocarbon service, the balance reverses, because 321H is supplied to the H-grade creep-rupture requirements of ASTM A213 and ASTM A249, which plain 316 tube is not.
Machinability and Weld Behaviour Compared With 304
321 stainless steel machinability sits close to 304, so tooling and feed rates carry over without much revision. Titanium does produce a stringier chip. On the weld side, heat-affected-zone carbide precipitation stays suppressed.
Testing and Inspection of SS 321H Tube
Every length is given either a hydrostatic test or a nondestructive electric test. Under ASTM A213, the choice rests with manufacturers like us unless the order specifies otherwise; under ASTM A249, the industrialist may specify which test is used. Eddy-current examination is available on request. Tension, hardness, and flattening tests apply to both routes. Flaring is the ASTM A213 requirement for seamless tubes; flange and reverse bend are the ASTM A249 requirements for welded tubes. All of them follow the general requirements of ASTM A1016/A1016M, with ASTM A262 corrosion testing on request.
Welding and Fabrication of 321H Tube
Fabricators welding 321 stainless steel tube in the H grade need no post-weld heat treatment, since titanium ties up carbon before chromium forms boundary carbides. Hot work suits the 1149 to 1260 °C band; below 927 °C isn't advisable.
Stainless Steel 321H Tube Shipping and Packaging
Every consignment leaves the works protected against transit damage and traceable to its heat. Lengths differ between round tubes and box sections, and export terms are fixed at the order stage.
- Round tube despatches in lengths up to 24 metres and box sections up to 12 metres, with cut lengths agreed at the order stage.
- Bundles are strip-strapped and end-capped, and each length is stencilled with its heat number; further marking is applied where the order calls for it.
- Each lot travels under its own mill test certificate, traceable to the stencilled heat number.
- Export consignments ship FOB or CFR under our Star Export House registration, with regular sailings to Turkey, Vietnam, and Brazil.
Stainless Steel 321H Tube Price
The stainless steel 321H tube price runs around ₹400–₹600 per kg and US$4.21–$6.32 per kg. The price of nickel input cost moves week to week, so we quote the day's rate rather than a list that ages fast. Six variables set the figure: outside diameter, wall gauge, cut length, route, finish, and quantity.
Why Buy Stainless Steel 321H Tube From MLTI?
Buyers return to Moonlight Tubes for certified material, approved grades and stock that ships on schedule. Every order is backed by documented quality, a wide size range and delivery commitments we hold to.
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Wide Range of Grades & Sizes
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Stainless Steel 321H Tube: Frequently Asked Questions
Seamless 321H tubes ship to ASTM A213 / ASME SA-213, and welded 321H tubes to ASTM A249 / ASME SA-249, both covering boiler, superheater, and heat-exchanger service.
The 321H tube holds carbon at 0.04 to 0.10% against a 0.08% ceiling for 321, and its grain size must be No. 7 or coarser. Both changes raise creep-rupture strength.
Yes, provided the heat analysis sits inside both carbon windows and titanium meets grade 321's five-times minimum. Dual certification then covers both line items on one certificate.
No. Titanium stabilisation suppresses chromium carbide precipitation in the heat-affected zone, so a stress-relief anneal is needed only where the design code calls for one.
ASTM No. 7 or coarser, measured to test method E112. That coarse-grain limit is a defining acceptance criterion for the TP321H tube and doesn't apply to plain 321.
No. 321H stainless steel holds no molybdenum, so pitting and stress corrosion cracking remain a risk in warm chloride streams and in sulphuric acid.
Round SS 321H tubes range from 12.7 mm to 101.6 mm in outside diameter, with walls of 1.02 mm to 3.4 mm and with square box sections from 12 x 12 mm and rectangular from 13 x 25 mm.