What are the specifications of SS 347 Seamless Pipe?

Available in UNS S34700 (ASTM A312 TP347), OD 1/8"-24" NB, Sch 5S-160, hot finished or cold drawn seamless construction, niobium-stabilized at 10xC minimum.

How does SS 347 differ from SS 321?

347 uses niobium rather than titanium for stabilization, giving slightly better weldability in thick sections and marginally higher strength retention at elevated temperature.

Why is 347 often specified for boiler superheater tubing?

Niobium carbides remain stable and effective across the wide, repeated thermal cycling superheater tubing experiences, and niobium's lower affinity for oxidation during welding improves multi-pass weld consistency versus titanium.

Can 347 and 321 be substituted for one another?

In many general applications yes, but project specifications (especially in power generation) often name one specifically due to differences in weld procedure qualification and code allowable stress tables.

Does Sakshi Forge provide Material Test Certificates (MTC) for SS 347 Seamless Pipe?

Yes, MTC as per EN 10204 3.1 is provided with every dispatch along with inspection reports.

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SS 347 Seamless Pipe - Niobium-Stabilized High Temperature Pipe | Sakshi Forge

Niobium-Stabilized Austenitic Stainless Steel Pipe for Heavy-Section High Temperature Piping

Niobium stabilized (Nb ≥ 10xC) for outstanding intergranular corrosion resistance

Superior weld consistency and lower oxidation loss in multi-pass welding versus 321

High creep and stress-rupture strength for ASME boiler code pressure piping

EN 10204 3.1 MTC100% PMI TestedISO 9001:2015 CertifiedHydrostatic Tested

Hygienic Steel Grade

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MTC EN 10204 3.1 Included

Global Sea & Air Freight

Electro-Chemical Finish Certificate

Response turnaround: Under 2 hours

Product Profile

SS 347 (UNS S34700 / ASTM A312 TP347) is a niobium (columbium) stabilized austenitic stainless steel seamless pipe engineered for severe high-temperature service up to 850°C (1560°F). Niobium is added at a minimum of 10 times the carbon content (up to 1.00% max) to form ultra-stable niobium carbides (NbC). These carbides prevent chromium carbide precipitation at grain boundaries during thermal exposure, providing exceptional protection against intergranular corrosion. Compared to titanium-stabilized SS 321, niobium in SS 347 has a lower affinity for oxidation during electric-arc and TIG welding. This delivers superior weld pool fluidity, enhanced multi-pass weld integrity, and better creep-rupture strength retention in heavy-wall piping sections. Sakshi Forge manufactures SS 347 seamless pipes per ASTM A312 and ASME SA312 standards, supplied fully solution annealed and pickled with 100% NDT inspection for power generation steam systems, petroleum hydroprocessing, and chemical reactors.

Terminology & Abbreviations

UNS S34700|S34700

Werkstoff 1.4550|1.4550

JIS SUS347|SUS347

ASTM A312 TP347|TP347

Key Technical Facts

Niobium addition dosed at 10x carbon minimum (up to 1.00% max) forming stable NbC carbides

Provides higher elevated-temperature creep strength than un-stabilized 304 or titanium-stabilized 321

Resists sensitization during multi-pass heavy-wall welding and long-term thermal exposure (425-850°C)

Lower metal transfer oxidation during TIG/MIG welding compared to titanium-stabilized grades

Manufactured via hot piercing/extrusion and precision cold drawing per ASTM A312 TP347

Solution heat treated at 1040°C-1100°C with rapid cooling to optimize carbide phase distribution

Fully hydrotested per ASTM A999 or 100% Eddy Current / Ultrasonic flaw inspected

Supplied with complete heat lot traceability and EN 10204 3.1 certified test data

Why Choose Sakshi Forge

Our commitment to sterile, high-purity processing makes us a trusted manufacturing partner globally.

100% Heat Lot Traceability

Every pipe stamped with heat number matching EN 10204 3.1 MTC

Positive Material Identification (PMI)

Handheld XRF testing on every length prior to dispatch

Advanced NDT Inspection

Hydrostatic test and Eddy Current / Ultrasonic flaw detection on all orders

Precision Cold Drawing

Tighter wall thickness tolerances and superior internal bore smoothness

Custom Cut Lengths

Fixed lengths up to 12 meters or custom cut-to-length options to eliminate jobsite scrap

Ferrite & Phase Balance Testing

Ferritescope testing for duplex and super duplex grades to ensure 40-60% phase balance

High-Temperature Stabilization

Controlled heat treatment to fully precipitate carbides and optimize creep life

Pan-India & Export Freight

Fast dispatch across India and seaworthy export packing for global projects

Extensive Mill Stocking

Immediate inventory availability in standard schedules from Sch 10S to Sch 160

Third-Party Inspection Approved

Full support for TUV, SGS, DNV, Bureau Veritas, and Lloyds audits

Frequently Asked Questions

Common technical and pricing queries regarding specifications and ordering.

SS 347 seamless pipe is manufactured to UNS S34700 / ASTM A312 TP347, available in ODs from 1/8" to 24" NB and schedules Sch 5S to Sch 160. It features niobium stabilization (Nb ≥ 10xC) for high-temperature service.

Partner with Sakshi Forge for Reliable Industrial Steel Solutions

Delivering precision-engineered flanges, pipes, and forged steel components designed for strength, durability, and performance in critical high-pressure industrial applications.