UNS S34700|1.4550|TP347 Seamless Stainless Steel Tube
Distinguished by the strategic addition of Niobium (Columbium), our TP347 tubing prevents chromium carbide precipitation during prolonged exposure to temperatures in the 427°C - 816°C (800°F - 1500°F) range. This makes them indispensable for mission-critical applications in chemical reactors, high-pressure steam systems, and aerospace components. Through advanced cold-drawing and precise solution annealing, XinZhe ensures every tube maintains a uniform microstructure and optimized mechanical strength for demanding industrial media.
"While TP347 provides excellent corrosion resistance, we also offer TP347H (UNS S34709) with higher carbon content for superior creep strength in temperatures above 1000°F."
What Is a Seamless Stainless Steel TP347 Tube?
TP347 (UNS S34700) is a niobium-stabilised austenitic stainless steel tube based on the 18-8 composition. Niobium at 8 × C to 1.00% ties up carbon as stable niobium carbides, preventing chromium carbide precipitation at grain boundaries and thereby preserving intergranular corrosion resistance after welding and in intermediate-temperature service.
Seamless TP347 stainless steel tube (UNS S34700 / W.Nr. 1.4550) is a niobium (columbium) stabilized austenitic stainless steel tube designed for applications involving high temperatures and intergranular corrosion resistance.
Manufactured through a seamless process (hot piercing + cold drawing/finishing) from a solid billet, TP347 tubes provide:
The key feature of TP347 is the addition of Niobium (Nb), which stabilizes carbon and prevents chromium carbide precipitation at grain boundaries. This ensures superior resistance to sensitization and intergranular corrosion (IGC), even after prolonged exposure to elevated temperatures or welding.
Key Features and Technical Advantages
Excellent Intergranular Corrosion Resistance Niobium stabilization prevents carbide precipitation, eliminating sensitization in the heat-affected zone (HAZ).
High-Temperature Performance (Up to 815°C) Performs reliably in continuous service up to 815°C (1500°F) with strong oxidation and scaling resistance.
Improved Creep Strength Compared with standard 304/304L, TP347 offers better creep resistance and structural stability under long-term high-temperature stress.
Excellent Intergranular Corrosion Resistance
Niobium stabilization prevents carbide precipitation, eliminating sensitization in the heat-affected zone (HAZ).
High-Temperature Performance (Up to 815°C)
Performs reliably in continuous service up to 815°C (1500°F) with strong oxidation and scaling resistance.
Improved Creep Strength
Compared with standard 304/304L, TP347 offers better creep resistance and structural stability under long-term high-temperature stress.
Excellent Weldability
Can be welded using standard methods without requiring post-weld heat treatment to restore corrosion resistance.
High Pressure Integrity
Seamless manufacturing ensures compliance with ASTM A213 / ASME SA213 / EN 10216-5, suitable for critical pressure systems.
Product Specifications and Data
To provide a comprehensive overview of this high-performance material, here are the detailed technical specifications and performance data for Stainless Steel 347.
The composition of Stainless Steel 347 is carefully balanced to achieve its superior high-temperature stability and corrosion resistance.
Grade | C | Cr | Ni | Mn | P | S | Si | Others |
| 347 | ≤0.08 | 17.00-20.00 | 9.00-13.00 | ≤2.00 | ≤0.045 | ≤0.030 | ≤1.00 | Nb≥10*C% |
| 347H | 0.04-0.10 | 17.00-19.00 | 9.00-13.00 | ≤2.00 | ≤0.045 | ≤0.030 | ≤1.00 | Nb≥8*C% |
Note: The niobium content must be at least ten times the carbon content to ensure stabilization.
Grade | Yield strength ksi(MPa) | Tensile Strength ksi(MPa) | Elongation % | Hardness Brinell/Vickers | Hardness Rockwell |
| 347 | ≥30(205) | ≥75(515) | ≥35 | ≤192 HBW/200HV | ≤90HRB |
| 347H | ≥30(205) | ≥75(515) | ≥35 | ≤192 HBW/200HV | ≤90HRB |
| Density | Melting Point | Thermal Expansion | Thermal Conductivity | Modulus of Elasticity | Electrical Resistivity |
|---|---|---|---|---|---|
| 8.0 g/cm³ | 1398 - 1454 °C | 16.6 µm/m·°C (20-100°C) | 16.3 W/m·K (20°C) | 193 GPa | 0.72 x 10⁻⁶ Ω·m (20°C) |
| Standard | OD(D) | Tolerance（MM) | Thickness(S) | Tolerance(MM) | Length | Tolerance | |
| MM | Common | High | MM | MM | |||
| EN 10216-5 HFD | 30≤D≤219.1（D2) | ±1.0% or ±0.5mm, whicever is the greater(取较大者) | T1, T≤4 | ±15% or ±0.6mm, whicever is the greater(取较大者) | L≤6M | +5/0 | |
| T2 | ±12.5% or ±0.4mm, whicever is the greater(取较大者) | ||||||
| 219.1≤D≤610 (D1) | ±1.5% or ±0.75mm, whicever is the greater (取较大者) | T≤0.05D | +22.5%/-15% | 6 | +10/0 | ||
| T1, 0.05D | ±15% or ±0.6mm, whicever is the greater(取较大者) | ||||||
| T2, T>0.09D | ±12.5% or ±0.4mm, whicever is the greater(取较大者) | L>12 | +by agreement/0 | ||||
| EN 10216-5 CFD | D3(D≤219.1) | ±0.75% or ±0.3mm, whicever is the greater(取较大者) | T3 | ±10% or ±0.2mm, whicever is the greater(取较大者) | |||
| D4(D≤219.1) | ±0.5% or ±0.mm, whicever is the greater(取较大者) | T4 | ±7.5% or ±0.15mm, whicever is the greater(取较大者) | ||||
| ASTM A213 HFD | D≤100 | +0.4/-0.8 | D<100,S≤2.4 | +40%/0 | HFD, all size | +5.0/0 | |
| +0.4/-1.2 | D<100,2.4 | +35%/0 | |||||
| +0.4/-1.6 | D<100,3.8 | +33%/0 | |||||
| D<100,S>4.6 | +28%/0 | ||||||
| 100 | +0.4/-1.2 | D>100, 2.4 | +35%/0 | ||||
| 200 | +0.4/-1.6 | D>100,3.8 | +33%/0 | ||||
| D>100,S>4.6 | +28%/0 | ||||||
| ASTM A213 CFD | D<25 | ±0.10 | D≤38.1 | +20%/0 | CFD, D<50.8 | +3.0/0 | |
| 25≤D≤40 | ±0.15 | ||||||
| 40 | ±0.20 | ||||||
| 50≤D<65 | ±0.25 | ||||||
| 65≤D<75 | ±0.30 | D>38.1 | +22%/0 | CFD, D≥50.8 | +5.0/0 | ||
| 75≤D≤100 | ±0.38 | ||||||
| 100 | +0.38/-0.64 | ||||||
| 200 | +0.38/-1.14 | ||||||
| ASTM A269 | D≤13 | ±0.13 | D≤13 | ±15% | D<38 | +3.2/0 | |
| 13 | ±0.13 | 13 | ±10% | ||||
| 38≤D<89 | ±0.25 | D>38 | +4.8/0 | ||||
| 89≤D<140 | ±0.38 | ||||||
| 140≤D<203 | ±0.76 | ||||||
| 203≤D<305 | ±1.01 | ||||||
| 305≤D<356 | ±1.26 | ||||||
| ASTM A270 | D<25 | ±0.13 | For weld pipe all size | ±12.5% | +3.0/0 | ||
| 25-50 | ±0.20 | ||||||
| 50-75 | ±0.25 | ||||||
| 75-100 | ±0.38 | For CD SMLS pipe D≤38.1 | +20%/0 | ||||
| 100-140 | ±0.38 | +5.0/0 | |||||
| 140-200 | ±0.75 | For CD SMLS pipe D>38.1 | +22%/0 | ||||
| 200-300 | ±1.25 | ||||||
Dimensional Standards and Tolerances
TP347 seamless tubes are supplied to the dimensional tolerances of ASTM A213 / A1016 unless a tighter project specification applies.
Common Industrial Applications
Power Generation
- Superheater and reheater tubing
- Boiler pressure parts
- High-temperature piping
Aerospace and Energy Systems
- High-temperature exhaust components
- Heat exchanger tubing
- Specialty energy equipment
Petrochemical and Refinery
- Heater and furnace tubing
- Process and transfer lines
- Polythionic-acid service piping
Waste and Incineration
- Incinerator heat recovery tubing
- Waste-heat boiler components
- Flue-gas handling equipment
Quality Assurance and Manufacturing Process
Certification
All TP347 (UNS S34700) tubes are supplied to ASTM A213 / ASME SA213 and ASTM A312 / ASME SA312 with EN 10204 3.1 mill test certificates. Third-party inspection (SGS, BV, TUV, Lloyd's), PMI reports and full heat-number traceability can be provided on request.
Non-Destructive Testing (NDT)
Hydrostatic or eddy-current testing is performed on 100% of tubes. Ultrasonic testing (UT) and dye-penetrant inspection (PT) are available for critical service, with records retained for each production lot.
Material Verification
Positive Material Identification (PMI) and spectrometric analysis confirm that the chemical composition matches the ordered grade and that the ferrite/austenite balance is within the specified range.
Mechanical Testing
Tensile, yield, elongation and hardness tests are carried out per heat. Impact testing can be supplied at the project design temperature for subsea and low-temperature service.
Dimensional Inspection
Outside diameter, wall thickness, ovality and straightness are measured against ASTM A1016 / A1016M or ASTM A789 tolerances. Length, square-cut ends and end-finish conditions are verified before packing.
TP347 vs TP321 / TP347H – Technical Comparison
TP347, TP321 and TP347H are all stabilised austenitic grades used at elevated temperature. The choice between them turns on the stabiliser and the carbon content.
Stabiliser and Carbon Content
- TP347: niobium-stabilised (8 × C to 1.00%), carbon 0.08% maximum
- TP321: titanium-stabilised (5 × C to 0.70%), carbon 0.08% maximum
- TP347H: niobium-stabilised with carbon 0.04–0.10% for creep strength
Elevated-Temperature Strength
TP347H delivers the highest creep-rupture strength of the three because of its controlled high-carbon range. TP347 and TP321 are comparable to each other, with niobium-stabilised grades generally preferred where high-temperature exposure follows welding.
Intergranular Corrosion Resistance
All three resist intergranular corrosion because the stabiliser ties up carbon as stable carbides. TP347 and TP347H also resist polythionic acid stress-corrosion cracking, which is the failure mode that governs refinery heater tubing.
Selection Guide
- Choose TP347 for welded equipment needing stabilisation at moderate temperature
- Choose TP347H for creep-limited superheater and heater tubing
- Choose TP321 where titanium stabilisation is specified
Frequently Asked Questions
What is TP347 tube?
TP347 (UNS S34700) is a niobium-stabilised austenitic stainless steel tube based on the 18-8 composition. Niobium ties up carbon as stable carbides, preventing chromium carbide precipitation at grain boundaries.
Why is TP347 stabilised with niobium?
Stabilisation preserves intergranular corrosion resistance in the heat-affected zone after welding and in intermediate-temperature service, and specifically protects against polythionic acid stress-corrosion cracking, the failure mode that governs refinery heater tubing.
What is the difference between TP347 and TP347H?
TP347 permits up to 0.08% carbon, while TP347H controls carbon in the 0.04–0.10% range. The controlled higher carbon content of TP347H delivers significantly better creep and stress-rupture strength at elevated temperature.
What is TP347 tube used for?
TP347 serves in power generation boiler and superheater components, petrochemical heater and process tubing, aerospace and energy systems, and waste incineration equipment.
Ready to Request a Quotation?
Send your Seamless Stainless Steel TP347 Tube enquiry with grade, application, size (OD and wall thickness or schedule), quantity, length, end finish and inspection requirements including any intergranular corrosion test data required.
UNS S34709|1.4912|TP347H Seamless Stainless Steel Tube
UNS S31703|1.4438|TP317L Seamless Stainless Steel Tube
UNS S31700|1.4449|TP317 Seamless Stainless Steel Tube
UNS S34700|1.4550|TP347 Seamless Stainless Steel Tube
UNS S32109|1.4878|TP321H Seamless Stainless Steel Tube
UNS S32100|1.4541|TP321 Seamless Stainless Steel Tube
UNS N08904|1.4539|TP904L Seamless Stainless Steel Tube
UNS N08031|1.4562|Alloy 31 Seamless Tube
UNS S30815|1.4835|253MA Seamless Stainless Steel Tube
UNS S31254|1.4547|254SMO Seamless Stainless Steel Tube