01
321 Stainless Steel Seamless Pipe
SS 321 seamless pipe begins as a solid billet, pierced and drawn to size, so no longitudinal joint runs through the wall. Higher-pressure refinery duty normally calls for it.
Stainless Steel 321 Pipe Manufacturer in India
MLTI Private Limited (Moonlight Tube Industries) manufactures Stainless Steel 321 Pipe at our modern manufacturing facility in Gujarat, India. We have been supplying austenitic pipe for over a decade, at a yearly capacity of nearly 8,000 MT.
Our 321 stainless steel pipe, grade TP321 (UNS S32100), is compliant with ASTM A312 / ASME SA-312 and ASME B36.19M dimensional standards. Titanium content is what sets the grade apart. SA-312 fixes the addition at five times the combined carbon and nitrogen content, capped at 0.70%, and titanium claims the carbon before chromium can. Chromium sits at 17.0 to 19.0% and nickel at 9.0 to 12.0% on an 18/8 austenitic base.
We manufacture SS 321 pipe by the seamless and welded (ERW) routes defined in ASTM A312 §6.1, round in section, with square and rectangular hollow profiles rolled to order, from 1/8 inch NB to 10 inch NB in SCH 10S, 20S, 40S, and 80S, with SCH 5S from 1/2 inch NB upward, in lengths reaching 24 feet (about 7.3 metres). SS 321 seamless pipe starts as a pierced billet, so ASME B31.3 gives it a longitudinal joint quality factor of 1.00. 321 stainless steel welded pipe starts at 0.85, and 100% radiography per B31.3 para. 344.5.1 raises it to 1.00. It fuses strip edges without filler, so weld chemistry matches the parent alloy.
Certified minima are 515 MPa tensile strength and 205 MPa yield strength at 35% elongation for welded pipe and for seamless pipe up to 9.5 mm wall. Seamless pipe above 9.5 mm wall drops to 485 MPa and 170 MPa under ASTM A312. The same alloy reads 1.4541 in Europe, SUS 321 in Japan and AISI 321 on older American drawings.
Refinery transfer lines, superheater piping, chemical circuits and process piping for the sugar, pharmaceutical and food-processing industries mostly use this pipe. Field welding on this grade needs no solution annealing afterwards, which is why fabricators call for it on site-joined spools. We hold ISO 14001 and ISO 45001 certifications, with IBR, EIL and PED approvals in place.
Stainless Steel 321 Pipe Specifications
This table details standards, dimensions, schedules, and conditions for Stainless Steel 321 pipes to ensure project compliance.
| Parameter | Value |
|---|---|
| Dimensional standard | ASME B36.19M for SCH 5S, 10S, 40S and 80S; SCH 20S walls to MLTI works standard, dimensions on request |
| Applicable standards | ASTM A312 / ASME SA-312 (Standard Specification for Seamless, Welded, and Heavily Cold Worked Austenitic Stainless Steel Pipes) ASME B36.19M (dimensions) ASME B31.3 (joint quality factor, design) |
| Size range | 1/8 inch NB to 10 inch NB |
| Schedule | SCH 5S, SCH 10S, SCH 20S, SCH 40S, SCH 80S |
| Wall thickness | 1.24 mm to 59.54 mm, by bore and schedule |
| Length | Up to 24 ft, permitted range 15 to 24 ft, for NPS 1/8 to NPS 10 per ASTM A312 §13.1.1; definite cut lengths to order per §13.1.2 |
| Manufacturing form | Seamless and welded (ERW) |
| Section profile | Round; square and rectangular hollow sections to order |
| Condition | Solution annealed at 1900°F (1040°C) minimum, rapidly cooled |
| End type | Plain end; bevelled to order |
SS 321 Pipe Chemical Composition
The ASTM A312 TP321 chemical composition holds chromium at 17.0 to 19.0% and nickel at 9.0 to 12.0%, with carbon capped at 0.08%. Element limits from ASME SA-312 are listed in the composition table below.
| Element | Composition (%) |
|---|---|
| Carbon (C) | 0.08 max |
| Manganese (Mn) | 2.00 max |
| Phosphorus (P) | 0.045 max |
| Sulphur (S) | 0.030 max |
| Silicon (Si) | 1.00 max |
| Chromium (Cr) | 17.0 to 19.0 |
| Nickel (Ni) | 9.0 to 12.0 |
| Titanium (Ti) | 5 × (C + N) min, 0.70 max |
| Nitrogen (N) | 0.10 max |
| Iron (Fe) | Balance |
321 SS Pipe Mechanical Properties
TP321 is certified to 515 MPa tensile and 205 MPa yield as welded, and as seamless up to 9.5 mm wall. ASTM A312 §1.5 reduces both figures for seamless pipe with heavier walls, and the table below carries both sets.
| Property | Value |
|---|---|
| Tensile strength, min — welded, and seamless ≤ 9.5 mm wall | 515 MPa (75 ksi) |
| Yield strength, min — welded, and seamless ≤ 9.5 mm wall | 205 MPa (30 ksi) |
| Tensile strength, min — seamless > 9.5 mm wall | 485 MPa (70 ksi) |
| Yield strength, min — seamless > 9.5 mm wall | 170 MPa (25 ksi) |
| Elongation in 2 in. (50 mm), longitudinal, min | 35% |
The reduced values apply to any seamless pipe with a nominal wall thickness greater than 3/8 in. [9.5 mm].
Alloy 321 Pipe Equivalent Grades and Designations
An enquiry rarely arrives written the way our own drawings are, and a European or Japanese designation calls up the same austenitic alloy. Cross-standard equivalents for A312 TP321 material and UNS S32100 pipe are compiled in the table underneath.
| Country / Standard | Designation |
|---|---|
| USA (UNS) | UNS S32100 |
| Europe (EN / W.Nr.) | X6CrNiTi18-10 (1.4541) |
| Japan (JIS) | SUS 321 / SUS 321TP (pipe) |
| India (IS) | X04Cr18Ni10Ti |
| China (GB/T) | 06Cr18Ni11Ti |
| UK (BS) | 321S31 |
| France (AFNOR) | Z6CNT18-10 |
| Russia (GOST) | 08Kh18N10T |
Stainless Steel 321 Pipe Types & Forms
Two manufacturing routes and three section profiles cover the 321 pipe we supply. Seamless and welded (ERW) come first, and round, square and rectangular profiles close the group.
02
321 Stainless Steel Welded Pipe (ERW)
Electric Resistance Welded (ERW) 321 pipe forms rolled steel strip into round profiles, joining seams without filler metal. Each length is subjected to the hydrostatic test or the nondestructive electric test, at the manufacturer's option under ASTM A312 §12.1 unless the order specifies one.
03
SS 321 Round Pipe
A round pipe carries internal pressure with hoop stress spread evenly through the wall, with no particular corner to concentrate it. Every A312 hydrostatic and tension report we issue covers this profile.
Square
04
SS 321 Square Pipe
Equal section modulus on both axes keeps orientation out of the fabricator's decisions. Flat faces sit flush against a fixture and take a fillet weld without a saddle cut.
Rectangular
05
SS 321 Rectangular Pipe
Orienting SS 321 rectangular pipe vertically along its longer side increases the moment of inertia, significantly improving flexural strength and resistance to deflection under load. This structural efficiency makes rectangular pipe ideal for applications subject to bending forces, such as handrails, structural frames, and heavy-duty equipment skid bases.
Stainless Steel 321 Pipe Sizes and Schedules
Our 321 pipe programme covers 1/8 inch NB through 10 inch NB in 5 schedules, in 15 ft to 24 ft lengths for sizes up to NPS 10 per ASTM A312 §13.1.1. Bores, outside diameters and wall thicknesses for each schedule are tabulated below.
| Nominal Bore (mm) | Nominal Bore (INCH) | Outside Diameter (mm) | Sch-5S Thickness (mm) | Sch-10S Thickness (mm) | Sch-20S Thickness (mm) | Sch-40S Thickness (mm) | Sch-80S Thickness (mm) |
|---|---|---|---|---|---|---|---|
| 6 | 1/8 | 10.30 | - | 1.24 | 1.50 | 1.73 | 2.41 |
| 8 | 1/4 | 13.70 | - | 1.65 | 2.00 | 2.24 | 3.02 |
| 10 | 3/8 | 17.10 | - | 1.65 | 2.00 | 2.31 | 3.2 |
| 15 | 1/2 | 21.34 | 1.65 | 2.11 | 2.30 | 2.77 | 3.75 |
| 20 | 3/4 | 26.70 | 1.65 | 2.11 | 2.55 | 2.87 | 3.91 |
| 25 | 1 | 33.40 | 1.65 | 2.77 | 3.00 | 3.38 | 4.55 |
| 32 | 1 1/4 | 42.20 | 1.65 | 2.77 | 3.00 | 3.56 | 4.85 |
| 40 | 1 1/2 | 48.30 | 1.65 | 2.77 | 3.00 | 3.68 | 5.08 |
| 50 | 2 | 60.30 | 1.65 | 2.77 | 3.00 | 3.91 | 5.54 |
| 65 | 2 1/2 | 73 | 2.11 | 3.05 | 4.00 | 5.16 | 7.01 |
| 80 | 3 | 88.9 | 2.11 | 3.05 | 4.00 | 5.49 | 7.62 |
| 100 | 4 | 114.3 | 2.11 | 3.05 | 4.50 | 6.02 | 8.56 |
| 125 | 5 | 141.3 | 2.77 | 3.4 | 5.00 | 6.55 | 9.53 |
| 150 | 6 | 168.3 | 2.77 | 3.4 | 6.35 | 7.11 | 10.97 |
| 200 | 8 | 219.1 | 2.77 | 3.76 | 6.35 | 8.18 | 12.7 |
| 250 | 10 | 273.1 | 3.4 | 4.19 | 6.35 | 9.27 | 12.7 |
Schedule 5S is not defined below 1/2 inch NB in ASME B36.19M.
Weight Chart of Stainless Steel 321 Pipe
This weight chart provides theoretical weight estimates per meter for SS 321 pipes across various nominal bores and schedules.
| Nominal Bore (mm) | Nominal Bore (INCH) | Sch-5S Weight (Kg/mt) | Sch-10S Weight (Kg/mt) | Sch-20S Weight (Kg/mt) | Sch-40S Weight (Kg/mt) | Sch-80S Weight (Kg/mt) |
|---|---|---|---|---|---|---|
| 6 | 1/8 | - | 0.28 | 0.33 | 0.37 | 0.47 |
| 8 | 1/4 | - | 0.49 | 0.58 | 0.631 | 0.8 |
| 10 | 3/8 | - | 0.63 | 0.74 | 0.845 | 1.1 |
| 15 | 1/2 | 0.8 | 1 | 1.08 | 1.27 | 1.62 |
| 20 | 3/4 | 1.03 | 1.28 | 1.52 | 1.68 | 2.2 |
| 25 | 1 | 1.3 | 2.09 | 1.94 | 2.5 | 3.24 |
| 32 | 1 1/4 | 1.65 | 2.7 | 2.90 | 3.38 | 4.47 |
| 40 | 1 1/2 | 1.91 | 3.11 | 3.35 | 4.05 | 5.41 |
| 50 | 2 | 2.4 | 3.93 | 4.24 | 5.44 | 7.48 |
| 65 | 2 1/2 | 3.69 | 5.26 | 6.81 | 8.63 | 11.4 |
| 80 | 3 | 4.51 | 6.45 | 8.37 | 11.3 | 15.2 |
| 100 | 4 | 5.84 | 8.36 | 12.18 | 16.07 | 22.3 |
| 125 | 5 | 9.47 | 11.57 | 16.81 | 21.8 | 31.97 |
| 150 | 6 | 11.32 | 13.84 | 25.36 | 28.3 | 42.7 |
| 200 | 8 | 14.79 | 19.96 | 33.31 | 42.6 | 64.6 |
| 250 | 10 | 22.63 | 27.78 | 41.77 | 60.5 | 96 |
Stainless Steel 321 Pipe Industrial Applications
Stainless Steel 321 pipes are engineered to withstand high temperatures, severe thermal cycling, and intergranular corrosion; key applications for these components are outlined below.
Petroleum Refining and Petrochemical Plant
Crude and vacuum unit piping runs hot enough to sensitise an unstabilised grade. We supply 321 pipe for transfer lines and reactor feed circuits, where a shutdown weld repair must hold with no heat treatment.
Power Generation
Superheater connecting piping, radiant headers and steam lines take SS 321 pipe. Boiler house joints are welded in the field, where no furnace anneal is possible afterwards.
Chemical Processing and Heat Exchanger Circuits
Connecting piping at exchangers cycles repeatedly through the precipitation range. Chemical plants also specify 321 pipe for jacketed vessel connections and organic acid lines.
Automotive and Motorsport Exhaust Systems
Turbo manifolds, downpipes, and collectors fabricated from 321 stainless pipe survive heat cycling that cracks 304 work inside a season. Builders weld them by hand.
Aerospace Exhaust Ducting
Engine exhaust collectors, bleed air lines, and auxiliary power unit ducting use the grade for the same reason. Weight rules here, so SCH 5S and 10S walls cover the work.
Welding and Heat Treatment of SS 321 Pipe
For welded pipe of NPS 6 and larger with a nominal wall of 0.200 in. and above, ASTM A312 §15 permits weld-seam repair over no more than 20% of the seam length. SA-312 Table 6 pairs TP321 with AWS A5.9 bare filler rod ER321 or ER347, applied by the gas tungsten-arc process.
Stainless Steel 321 Pipe Shipping and Packaging
We ensure secure packaging, damage-free transit, and complete documentation for all Stainless Steel 321 pipes.
- Pipes are packed and transported in strapped hexagonal bundles or wooden cases, where the destination requires it.
- Plastic caps close plain ends, and bevel protectors go on machined ends, with plastic wrap or paper interleaving to keep the passivated surface clean.
- Marking carries our identifying mark, the specification, grade, size, schedule, process designation (SML or WLD), heat number, and heat-treatment lot.
- Material test certificates to EN 10204 3.1 and A312 test reports travel with the consignment.
Stainless Steel 321 Pipe Price
The SS 321 price per kg in India ranges around ₹337-₹500/kg in India (approximately US$3.53-US$5.24/kg) for round pipe on marketplace listings, indicative at the time of writing rather than a standing offer. Nickel and titanium trade daily, so the stainless steel 321 price per kg we confirm depends on bore, wall, length, tonnage, and test scope. Seamless carries a premium over welded.
Why Buy Stainless Steel 321 Pipe 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.
Quality Certification
01
IBR & EIL Approved
02
Why
Choose Us
03
Wide Range of Grades & Sizes
04
Timely Global Delivery
Frequently Asked Questions
ASTM A312 TP321 pipe is used for refinery transfer lines, superheater and steam piping, exchanger connections and welded exhaust work, on services that would sensitise an unstabilised grade.
Post-weld solution annealing isn't normally required. Titanium at 5 × (C + N) minimum, 0.70% maximum ties up the carbon, so the heat-affected zone keeps its chromium.
ASME SA-312 Table 6 pairs TP321 with AWS A5.9 bare filler rod ER321 or ER347 for weld-seam repair. Both consumables carry a stabiliser, so the weld metal resists attack too.
ASME SA-312 sets no service ceiling; allowable stress at temperature comes from the design code. The grade is chosen because titanium stabilisation holds through the 425°C to 815°C band.
The UNS number is S32100. Order papers may equally read UNS S32100 pipe, AISI 321 or ASTM A312 TP321.
Standard bores and schedules move ex-stock from Umbergaon; the rest is rolled to order. Ask us to confirm what is on the floor first.