What Is a Seamless Stainless Steel TP347H Tube?
Seamless Stainless Steel TP347H Tube-ASTM A213 TP347H (UNS S34709) | High-Temperature Niobium-Stabilized Tubing
TP347H Seamless Stainless Steel Tube is supplied for niobium stabilization with higher carbon for creep and high-temperature service. The size range shown (OD 6–257 mm; WT 0.5–35 mm) is the overall capability across this product family, not a per-grade commitment. Confirm the specific OD × WT × length combination for the ordered grade in the quotation. The governing specification must be stated on the purchase order: ASTM A213 / ASME SA213. Chemistry, mechanical properties, heat treatment, dimensional tolerance, NDT and certification must be reported against the ordered standard and material heat; do not treat typical values as guaranteed acceptance limits.
As the “H-grade” version of TP347, it features a controlled carbon content (0.04–0.10%) to enhance:
- Creep strength
- Stress rupture resistance
- Long-term thermal stability
TP347H seamless tubes are manufactured via cold drawing (CF) or hot finishing (HF) processes, ensuring:
- Uniform metallurgical microstructure
- High dimensional accuracy
- No longitudinal weld seam, so no weld joint to assess in pressure design
These properties make TP347H the preferred material for boilers, superheaters, and heat exchangers operating above 538°C (1000°F).
Key Features & Technical Advantages
1. Niobium Stabilization (Anti-Sensitization)
- Niobium (Nb) binds carbon to limit chromium carbide precipitation
- Greatly reduces the risk of intergranular corrosion (IGC) in the heat-affected zone (HAZ)
- Suitable for long-term exposure at 427°C–816°C
2. Excellent High-Temperature Strength
- Optimized carbon-to-niobium ratio (Nb ≥ 8×C)
- Superior creep resistance compared to TP304H and TP321
- Ideal for load-bearing components under thermal stress
3. Outstanding Oxidation & Corrosion Resistance
4. Seamless Structural Integrity
- No longitudinal welds
- Enhanced pressure resistance
Technical Specifications
Applicable Standards
- ASTM A213 / ASME SA213
- EN 10216-5
- ASTM A312 (optional piping use)
- JIS G3463 / GB/T 14976
Chemical Composition (Weight %)
The key differentiator of TP347H is the Nb stabilization ratio:
Nb≥8×C
The stabilization ratio (Nb≥8xC) is the critical factor that distinguishes TP347H from standard 304 or 321 grades.
Product Specifications and Data
The enhanced strength of TP347H is a direct result of its high carbon content, while retaining the essential niobium, chromium, and nickel levels for heat and corrosion resistance.
Equivalent Grade
| UNS | Common grade name | EN material number | EN steel name | JIS grade | GB/T grade |
|---|---|---|---|---|---|
| S34709 | 347H | 1.4912 (approx.) | X7CrNiNb18-10 | SUS347HTB (product suffix to verify) | 07Cr18Ni11Nb |
Grade correspondence does not make ASTM, ASME, EN, JIS and GB delivery requirements interchangeable. Confirm chemistry, heat treatment, mechanical properties, dimensions, testing and certification against the purchase specification. Approximate or unconfirmed correspondences retain their qualification. See the grade designation index.
Chemical Composition
| Grade | C | Cr | Ni | Mn | P | S | Si | Other |
|---|---|---|---|---|---|---|---|---|
| 347 | ≤0.08 | 17.00–20.00 | 9.00–13.00 | ≤2.00 | ≤0.045 | ≤0.030 | ≤1.00 | Nb 10×C–1.10 |
| 347H | 0.04–0.10 | 17.00–19.00 | 9.00–13.00 | ≤2.00 | ≤0.045 | ≤0.030 | ≤1.00 | Nb 8×C–1.10 |
Data source: ASTM A213-25 / ASME SA213 Table 1, TP347H row ≤ heat-analysis acceptance limits. Confirm the values against the ordered edition and the MTC.
Grade 347H is specifically designed to maintain its strength and shape in high-stress, high-temperature applications.
Typical Mechanical Properties
| 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 |
Note: Typical values for reference only — not acceptance limits. Mechanical properties are reported on the MTC against the ordered standard, product form, condition and test temperature.
Typical Physical Properties
These physical properties highlight the material’s ability to perform reliably under extreme thermal conditions.
| 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 × 10-6 0:m (20°C) |
Note: Typical values for reference only — not acceptance limits. Physical and mechanical properties are reported on the MTC against the ordered standard, product form and condition.
ASTM A1016/A1016M Tube Size Tolerance Chart
Size Tolerance Chart (mm)
| Specified Outside Diameter (OD) (Inches) | Permissible Variations in OD (± Inches) |
|---|---|
| 1⁄2 to 1 | ±0.005 |
| Over 1 to 1-1⁄2 | ±0.008 |
| Over 1-1⁄2 to 2 | ±0.010 |
| Over 2 to 2-1⁄2 | ±0.012 |
| Over 2-1⁄2 to 3-1⁄2 | ±0.014 |
| Over 3-1⁄2 to 5 | ±0.020 |
Tolerance basis: permitted variations per the governing specification stated on this page and the applicable general-requirements standard (ASTM A1016 / ASME SA1016) for the ordered product form; the wall-thickness and length variations in this section follow the same basis.
| Specified Outside Diameter (OD) (Inches) | Specified Wall Thickness (WT) (Inches) | Permissible Variation (± Inches) |
|---|---|---|
| 1⁄2 to 1 (Inclusive) | 0.025 to 0.065(Inclusive) | ±0.010 |
| Over 0.065to 0.134 (Inclusive) | ±0.012 | |
| Over 1 to 1-1⁄2 (Inclusive) | 0.025 to 0.065 (Inclusive) | ±0.010 |
| Over 0.065 to 0.134 (Inclusive) | ±0.012 | |
| Over 1-1⁄2 to 2 (Inclusive) | 0.025 to 0.049 (Inclusive) | ±0.011 |
| Over 0.049 to 0.083 (Inclusive) | ±0.012 | |
| Over 0.083 to 0.148 (Inclusive) | ±0.014 | |
| Over 2 to 2-1⁄2 (Inclusive) | 0.032 to 0.065 (Inclusive) | ±0.013 |
| Over 0.065 to 0.109 (Inclusive) | ±0.015 | |
| Over 0.109 to 0.165 (Inclusive) | ±0.017 | |
| Over 2-1⁄2 to 3-1⁄2 (Inclusive) | 0.032 to 0.165 (Inclusive) | ±0.020 |
| Over 0.165 to 0.220 (Inclusive) | ±0.025 | |
| Over 3-1⁄2 to 5 (Inclusive) | 0.083 to 0.165 (Inclusive) | ±0.025 |
| Over 0.165 to 0.220 (Inclusive) | ±0.030 |
Length Tolerance
For Specific Cut Lengths, the standard tolerance is +1⁄8 in. [3 mm], -0 in. [0 mm].
Important Note: The values presented here are based on the dimensional tolerance tables in ASTM A1016/A1016M (General Requirements for Ferritic Alloy Steel, Austenitic Alloy Steel, and Stainless Steel Tubes), contains other essential requirements like straightness and details for tubes with ODs outside of this range. Always consult the latest official standard for design and procurement.
Typical Applications of TP347H Seamless Tubes
TP347H tubes are widely used in high-temperature, high-pressure, and corrosion-intensive industries:
Power Generation
- Superheater and reheater tubes
- Ultra-supercritical (USC) boilers
Petrochemical & Refining
- Hydrocracking units
- Hydrotreating systems
- High-temperature hydrogen service
Renewable Energy
- Biomass boilers
- Waste-to-energy incinerators
Chemical Processing
- Heat exchangers
- Acid-resistant high-temperature piping systems
Quality Assurance & Certifications
We ensure strict compliance with international standards through full inspection and testing:
Certification
- EN 10204 3.1 MTC as standard; 3.2 by arrangement
- Full traceability system
Non-Destructive Testing (NDT)
- Eddy Current Testing (ET) or Ultrasonic Testing (UT), as specified
Hydrostatic Testing
- Conducted in accordance with ASTM A1016
Metallurgical Testing
- Grain Size Analysis (ASTM E112)
- Intergranular Corrosion Test (ASTM A262 Practice E)
Material Verification
- PMI (Positive Material Identification), when specified on the purchase order
Why Choose Our TP347H Seamless Tubes?
- Stable supply with strict quality control
- Competitive factory pricing
- Full certification and third-party inspection support
- Fast delivery for global projects
Call to Action
Looking for a reliable TP347H seamless stainless steel tube supplier?
Contact our technical sales team today for:
- Competitive quotation
- Stock availability
- Technical support and customization
Frequently Asked Questions
What sizes are available for TP347H seamless tube?
The overall range is OD 6–257 mm; WT 0.5–35 mm. Requirements outside this range are reviewed against mill capability on request.
Which specification governs TP347H seamless tube?
ASTM A213 / ASME SA213 is the governing specification for TP347H seamless tube. The edition in force at order time is stated on the quotation and purchase order; chemistry, mechanical properties, heat treatment, dimensions and testing are reported against the ordered standard and material heat.
What inspection documents are provided?
Each order is documented with a mill test certificate stating heat chemistry and mechanical test results. EN 10204 3.1 certification, hydrostatic testing, eddy-current or ultrasonic inspection and PMI are performed when specified in the purchase order.
Technical review: page data reviewed by the Xinzhe technical desk on 2026-09-27. Chemistry acceptance limits are compiled from the governing ASTM/ASME specification stated on this page; mechanical and physical values are typical reference data and are not acceptance guarantees. Values must be confirmed against the standard edition in force at order time and the material test certificate.
Ready to Request a Quotation?
Send the size (OD and wall or schedule), quantity, length, end finish and the inspection items you need as acceptance criteria — you will get a written quotation stating the specification and edition, delivery condition, documents included and lead time.
For the same grade in pipe form, see the TP347H seamless pipe. To compare other grades and size combinations, browse the Stainless Steel Seamless Pipe category. Minimum order quantity and lead time are confirmed on enquiry against the ordered grade, size and quantity.
