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SS 347 Seamless Tube
Seamless 347 tube starts as a pierced hollow and finishes by cold drawing, so there's no longitudinal seam to act as a crack initiation site under thermal cycling. ASTM A213 / ASME SA-213 governs it.
Stainless Steel 347 Tube Manufacturer in India
MLTI Private Limited, formerly known as Moonlight Tube Industries, has manufactured stainless steel 347 tube in Gujarat, India, for over a decade, at a capacity of nearly 8,000 MT a year.
Stainless steel 347 tube is the niobium-stabilised grade of the 18/8 austenitic family, registered as UNS S34700 and still called AISI 347 on older drawings. Niobium enters at ten times the carbon content with a 1.10% ceiling, and that addition is what sets this grade apart. Chromium runs 17.0 to 20.0% and nickel 9.0 to 13.0% under ASTM A213, with carbon capped at 0.08%. Welded tube works to a narrower band of 17.0 to 19.0% chromium and 9.0 to 12.0% nickel. In the solution-annealed condition, certified minima are 515 MPa (75 ksi) tensile strength, 205 MPa (30 ksi) yield strength and 35% elongation. Continental documentation reads 1.4550 for the same austenitic stainless steel 347 tube, Japanese ones SUS 347TB. We produce SS 347 seamless round tube to ASTM A213 / ASME SA-213 and welded 347 SS round tube, including ERW, to ASTM A249 / ASME SA-249. Welded round, square and rectangular sections are produced to ASTM A554. Round SS 347 tube spans 12.7 mm to 101.6 mm outside diameter on walls of 0.71 mm to 3.25 mm, cut to any length up to 24 metres.
We supply these tubes primarily for superheater, heat-exchanger and chemical-process duty across the power, oil and gas, chemical and petrochemical sectors. We offer competitive pricing based on dimensions and ship internationally on FOB or CFR terms. Our manufacturing facility holds ISO 14001 and 45001 certifications, BIS and EIL approvals, IBR registration, and AD 2000-Merkblatt W0 manufacturer approval, and supplies materials for pressure equipment placed on the EU market under Directive 2014/68/EU (PED).
Stainless Steel 347 Tube Specifications
Every ordering parameter for ASTM A213 TP347 tube sits in the table below: governing specifications, manufacturing processes, section, diameter, wall, length, and delivery condition.
| 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 A269 (Seamless and Welded Austenitic Stainless Steel Tubing for General Service); ASTM A554 (Welded Stainless Steel Mechanical Tubing) |
| Manufacturing process | Seamless and welded (ERW) |
| Section | Round (seamless or welded); square and rectangular (welded, ASTM A554) |
| Outside diameter, round | 12.7 mm to 101.6 mm (1/2" to 4") |
| Wall thickness, round | 0.71 mm to 3.2 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 at 1040 °C minimum, rapid cooled |
| Finish | Mill finish; pickled and passivated; polished to order |
SS 347 Tube Chemical Composition
Grade 347 parts from plain 18/8 on three lines of the analysis. Niobium comes in at ten times the carbon content, the chromium floor drops to 17.0%, and the nickel band shifts up to 9.0 to 13.0%. Limits for this niobium-stabilised stainless steel to ASTM A213 / ASME SA-213 are given in the table below.
| Element | Composition, % by mass |
|---|---|
| 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 – 20.0 |
| Nickel (Ni) | 9.0 – 13.0 |
| Niobium (Nb) | 10 x C min, 1.10 max |
| Iron (Fe) | Balance |
Alloy 347 Tube Mechanical Properties
Design calculations for boiler and exchanger duty start from three certified minima and one hardness maximum. The values governing acceptance of ASME SA-213 TP347 tube appear in the table below.
| 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 (192 HBW / 200 HV) |
Welded 347 stainless steel tube to ASME SA-249 is certified to the same four figures. Seamless tube supplied unstraightened after final heat treatment, such as coils, is the exception: under Supplementary Requirement S3 of ASME SA-213, the minimum yield strength is reduced by 35 MPa (5 ksi), and the grade designation carries a "U" suffix.
Stainless Steel 347 Tube Equivalent Grades
Cross-reference designations of SS 347 are matched in the table underneath, such as UNS, EN, JIS, and others.
| Country / Standard | Designation |
|---|---|
| USA (UNS) | UNS S34700 |
| Europe (EN / W.Nr) | 1.4550, X6CrNiNb18-10 |
| Japan (JIS) | SUS 347, SUS 347TB |
| China (GB) | 06Cr18Ni11Nb |
| UK (BS) | 347S31 |
| France (AFNOR) | Z6CNNb18-10 |
| Sweden (SS) | 2338 |
Stainless Steel 347 Tube Forms and Types
We supply seamless and welded SS 347 round tube, plus welded square and rectangular sections, solution-annealed to handle severe thermal and corrosive environments.
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SS 347 Welded (ERW) Tube
Tubes are made by automatically welding a strip without filler metal and are then solution annealed to ASTM A249 / ASME SA-249.
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SS 347 Round Tube
Round is our highest-volume profile, rolled across eleven diameters between 12.7 mm and 101.6 mm. Exchanger bundles, superheater coils and instrumentation runs all draw on Alloy 347 tube in round form.
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SS 347 Square Tube
Square box section runs 12 x 12 mm through 100 x 100 mm on walls of 1.0 mm to 6.0 mm. Furnace framing and hot-gas support steelwork take SS 347 square tube.
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SS 347 Rectangular Tube
Rectangular section covers 13 x 25 mm to 100 x 50 mm at the same wall range, to 12 metres long. Fabricators call for SS 347 rectangular tube on members loaded about one axis.
SS 347 Tube Sizes
Standard dimensions, outer diameters, and wall thicknesses for seamless and ERW small diameter 347 stainless steel tube options are provided in the table given below.
SS 347 Seamless 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 347 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 |
347 Stainless Steel Tube Industrial Applications
Engineers specify 347 SS tubing for extreme heat and chemical exposure across five key sectors, preventing carbide precipitation where unstabilised alloys fail.
Thermal Power Generation
Superheater and reheater elements run hot enough to sensitise an unstabilised austenitic analysis, so utility boiler builders specify SS 347 boiler tube for pendant and radiant banks.
Petroleum Refining
Polythionic acid forms on tube surfaces during refinery shutdown and attacks chromium-depleted grain boundaries in sensitised material. Niobium stabilisation slows sensitisation, so hydrotreater and reformer units take SS 347 heat exchanger tubes on the process side.
Chemical and Petrochemical Processing
Nitric acid plants, ammonia units and waste-heat recovery duty pass hot process gas through a stabilised austenitic tube. Jacketed vessel coils and reformer convection banks are the usual positions for alloy 347 tubing.
Aerospace Fabrication
Exhaust stacks, ring collectors and engine manifolds are formed from thin-wall aircraft stainless steel tubing in this grade. It welds without a post-weld solution anneal for dry high-temperature service and survives repeated thermal cycling.
Automotive and Motorsport
Turbocharger manifolds and heavy-duty exhaust headers reach metal temperatures that would sensitise SS 304 tubes. Builders of turbo manifolds use SS 347 tube in a round section, then leave the joints unannealed.
Alloy 347 Tube Shipping and Packaging
As a truncated exporter of SS 347 tubes, we ensure safe transit and compliant global delivery with custom export packaging.
- Round tube ships to 24 metres, box section to 12 metres.
- Bundles carry end caps, strip strapping and stencilling for grade, heat number and specification; polished material is PVC-sleeved inside wooden crates.
- Brazil, Turkey and Vietnam take regular shipments of 347 SS tube.
- Each lot carries its own mill test certificate quoting the heat number.
Stainless Steel 347 Tube Price
Stainless steel 347 tube price is quoted around ₹350-650/kg in India (approximately $3.66-6.79/kg), since nickel and niobium input costs fluctuate often and there's no rate card that holds for long. Seven variables set the figure: diameter, wall gauge, section, route, cut length, finish and quantity.
Why Buy Stainless Steel 347 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.
Quality Certification
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IBR & EIL Approved
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Why
Choose Us
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Wide Range of Grades & Sizes
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Timely Global Delivery
Frequently Asked Questions About Stainless Steel 347 Tube
Seamless 347 tube ships to ASTM A213 / ASME SA-213 and welded 347 tube to ASTM A249 / ASME SA-249, both covering boiler, superheater and heat-exchanger service. General-service tubing follows ASTM A269.
Niobium ties up carbon as niobium carbide before chromium can form chromium carbide at the grain boundaries. The tube then resists intergranular attack after exposure in the 425 °C to 815 °C sensitisation band.
Yes. Turbo manifolds and heavy-duty exhaust headers sit inside the sensitisation range, and stabilised 347 tube keeps its corrosion resistance there without post-weld heat treatment. A stabilising heat treatment after welding is added only for refinery service where polythionic acid cracking is a design concern; it is a supplementary requirement under ASTM A213 S2 and ASTM A249 S4.