Search
한국어
русский
عربى
Utilizing 26 high-precision cold rolling mills and 6 cold drawing machines, we ensure dimensional accuracy and superior mechanical properties.
ASTM A312 TP347 Seamless Steel Pipe
Niobium Stabilized | UNS S34700 | Highest Creep Rupture Strength
ASME SA312 | Power & Refinery GradeRelated Products
Introduction
ASTM A312 TP347 Seamless Steel Pipe is stabilized with niobium (columbium) plus tantalum at a minimum of eight times the carbon content, a stronger stabilizing ratio than titanium provides in TP321. Niobium carbides are thermally more stable than titanium carbides at the highest end of the austenitic service range, which is why TP347 is the grade of choice — rather than TP321 — whenever design temperatures push toward and beyond 600°C-650°C for extended periods. The same underlying mechanism applies: niobium ties up carbon preferentially, keeping chromium in solid solution at grain boundaries and preventing the intergranular corrosion that would otherwise follow welding or long-term sensitizing exposure.
TP347's principal advantage over both standard 304/316 grades and even TP321 is its published creep rupture strength at temperature, which is meaningfully higher in ASME Section II Part D allowable stress tables above roughly 550°C. This makes it a standard specification for superheater and reheater tubing headers, main steam piping in high-pressure boilers, and other components where the governing design case is long-term creep life under sustained pressure and heat rather than short-term yield strength. As true seamless pipe, it also avoids the weld-seam derating that would otherwise reduce allowable pressure in an equivalent welded product at the same wall thickness.
Fabrication follows the same general rules as other stabilized grades: TP347 tolerates as-welded service without post-weld heat treatment in most applications, resists polythionic acid stress corrosion cracking during refinery shutdown cycles, and should be welded with matching TP347 or ER347 filler metal to preserve the stabilization ratio across the joint. Mill certificates should confirm the Nb+Ta content meets the 8xC minimum (with an upper limit around 1.00%), since this ratio — not just the presence of niobium — is what determines whether the pipe actually delivers the intended high-temperature performance.
Specifications
| Material Grade | TP347 (UNS S34700) |
| Standard | ASTM A312, ASME SA312 |
| Outer Diameter | 10mm - 273mm |
| Wall Thickness | 1.0mm - 25mm |
| Length | Up to 18000mm |
| Finish | Solution Annealed, Pickled |
Chemical Composition
| C | Cr | Ni | Nb+Ta | Mn |
| ≤.08 | 17-19 | 9-13 | 8xC-1.00 | ≤2.0 |
Nb Stabilized High Creep Strength
Mechanical Strength
Comprehensive Info
| MOQ | 500kg |
| Lead Time | 25 - 40 Days |
| Testing | Nb/Ta Ratio Verification & Hydro |
| Design Reference | ASME Sec II Part D |
Key Applications
Superheaters High-pressure superheater and reheater headers
Main Steam Piping Boiler main steam and hot reheat lines
Refinery Piping High-temperature process lines with cyclic sulfur exposure
Advantages
Highest Creep Strength
Best published rupture strength among common stabilized grades.
600°C+ Rated
Suited to sustained service above the range TP321 tolerates.
No PWHT Typically Needed
Niobium stabilization protects weld zones from sensitization.
PASCC Resistant
Withstands polythionic acid attack during refinery shutdowns.
About Jiangsu Jend Tube Co.,Ltd.
As China ASTM A312 TP347 Seamless Steel Pipe Manufacturers and Wholesale ASTM A312 TP347 Seamless Steel Pipe Factory, Established in 2011 and is a manufacturing enterprise with a complete manufacturing cycle from raw material selection to finished product delivery. The company currently has more than 100 employees, covers an area of 30015 square meters, and has a registered capital of 48 million yuan, annual production capacity of 3800 tons.
The company has passed ISO9001:2015 quality certification, domestic pressure vessel TS certification, and foreign pressure vessel PED certification. With rich experience and mature technology, we have been expanding our market internationally. At present, our products are exported to more than 50 countries and regions including Europe, America, Southeast Asia, and the Middle East.
The company adheres to different production norms and standards such as the American standard (ASTM), the European standard (EN), the German standard (DIN), the Japanese standard (JIS), the Russian standard (GOST), and the Chinese standard (GB).
Our company specializes in and customizes various specifications of Martensite TP410 (0Cr13, 1Cr13), Ferrite TP405 (1Cr13Al), TP430 (1Cr17), TP444 (0Cr18Mo2), TP439, TP409 (0Cr11Ti), It is also proficient in manufacturing Austenitic seamless stainless steel pipes of series such as TP304(L/H), TP316(L/H/Ti), TP310S, TP317, TP321(H) and TP347(H). Duplex such as S31803, S2205, S32750, S32304, and Nickel-based alloys Monel400, Monel600, Monel800, GH3030, 904L, Inconel 625, etc.
The company mainly produces seamless steel pipes with the following specifications: outer diameter: 3.18mm to 406.4mm, wall thickness: 0.3mm to 20mm, and the longest length is 25000mm. Additionally, it can customize seamless steel pipes with special materials and specifications according to customer requirements. The company attaches great importance to scientific innovation. The staff of the company vigorously develop technological research and development.
Jiangsu Jend Tube Co.,Ltd. will continuously accumulate professional knowledge and capabilities, striving to become a leader in the domestic market and even the world market. Strive to be the most reassuring pipe manufacturing enterprise for customers.
Precision Manufacturing and Process Optimization
We rely on precision equipment and optimized production technologies to achieve outstanding mechanical performance and consistent product quality.
Cold Rolling and Cold Drawing
Solution Heat Treatment
Natural gas solution treatment furnaces and BA solution treatment furnaces optimize the material's grain structure, enhancing corrosion resistance.
Precision Straightening and Polishing
10 straightening machines and 8 finishing polishing machines guarantee product surface smoothness and dimensional accuracy.
Automated Inspection and Quality Assurance
Real-time monitoring systems ensure the stable quality of every batch of products.
Usage Tips
Filler Metal Match
Use ER347 or TP347 filler metal for welding to preserve the stabilization ratio across the joint.
Verify Nb+Ta Ratio
Confirm the mill certificate shows niobium plus tantalum at or above 8 times carbon content before accepting material for high-temperature service.
Services
Heat Traceable Cutting
Length control with heat number retained on every piece.
Hydrostatic Testing
Full pressure testing to ASME code requirements.
Bevel End Prep
Weld-ready bevels to project specification.
Logistics
30% T/T Deposit / L/C at sight. Export-packed in fumigated wooden cases with nitrogen-purged end caps for long-transit power project shipments.
Standards
ASME SA312
ASME Section II Part D
PED 2014/68/EU
ISO 9001
Frequently Asked Questions
How does TP347 differ from TP321?
TP347 uses niobium plus tantalum stabilization rather than titanium, and its carbides remain stable at higher temperatures, giving it better creep rupture strength above roughly 600°C.
What is the minimum stabilization ratio for TP347?
Niobium plus tantalum content must be at least 8 times the carbon content, up to a practical maximum of about 1.00%.
Is TP347 used in main steam piping?
Yes, it is a standard choice for high-pressure, high-temperature steam piping and superheater headers where long-term creep life governs design.
Does TP347 require post-weld heat treatment?
Typically not, since the stabilization protects the heat-affected zone from sensitization, though project code requirements should always be checked.
What filler metal should be used for welding?
ER347 or matching TP347 filler metal is recommended to keep the stabilization ratio consistent through the weld deposit.
Can TP347 be supplied with ASME Section II Part D certification?
Yes, allowable stress values for TP347 are published in ASME Section II Part D, and mill certificates can be issued referencing the applicable material specification.
Ready to Order TP347 Seamless Pipe?
Send your design pressure and temperature schedule for an ASME-compliant wall thickness quotation.
Request a Quote
