What Is a Seamless Stainless Steel TP347 Pipe?
TP347 Seamless Stainless Steel Pipe is supplied for niobium stabilization for resistance to sensitization during high-temperature exposure. The size range shown (OD 6–1016 mm; WT 0.5–65 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 A312 / ASME SA312. 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.
The”347″designation signifies an austenitic stainless steel that is stabilized with the addition of niobium and tantalum. While a low-carbon grade like 304L is excellent for preventing intergranular corrosion during welding, it can still be vulnerable to”sensitization”(carbide precipitation) if exposed to high temperatures for a long time. The niobium/tantalum in 347 binds with carbon, preventing chromium from forming carbides at the grain boundaries. This stabilization ensures that the pipe maintains its superior corrosion resistance even after being exposed to high temperatures up to 870°C (1600°F).
Key Features and Advantages
Stainless Steel 347 Seamless Pipe offer a unique combination of benefits that make them invaluable in demanding applications:
Exceptional Resistance to Intergranular Corrosion: The addition of niobium/tantalum stabilises carbon as niobium carbides, reducing chromium carbide precipitation in the 450–850 °C range and limiting the risk of intergranular corrosion in the weld zone and heat-affected zone. Performance still depends on the welding procedure and the service temperature.
Superior High-Temperature Performance: It provides better high-temperature strength and creep resistance than 304 stainless steel, making it suitable for a wide range of thermal applications.
Excellent Corrosion Resistance: It offers good general corrosion resistance, similar to 304, in various atmospheric and chemical environments.
High Pressure Tolerance: The seamless construction provides a uniform, robust structure that safely handles high internal pressures.
Product Specifications and Data
To provide a comprehensive overview of this high-performance material, here are the detailed technical specifications and performance data for 347 stainless steel.
Equivalent Grade
| UNS | Common grade name | EN material number | EN steel name | JIS grade | GB/T grade |
|---|---|---|---|---|---|
| S34700 | 347 | 1.4550 | X6CrNiNb18-10 | SUS347 | 06Cr18Ni11Nb / 0Cr18Ni11Nb |
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. See the grade designation index.
Chemical Composition
The key to TP347 ‘s performance is its precise composition, including the crucial addition of niobium/tantalum.
| Grade | C | Cr | Ni | Mn | P | S | Si | Other |
|---|---|---|---|---|---|---|---|---|
| 347 | ≤0.08 | 17.00-19.00 | 9.00-13.00 | ≤2.00 | ≤0.045 | ≤0.030 | ≤1.00 | Nb 10×C–1.00 |
| 347H | 0.04-0.10 | 17.00-19.00 | 9.00-13.00 | ≤2.00 | ≤0.045 | ≤0.030 | ≤1.00 | Nb 8×C–1.00 |
Data source: ASTM A312-25 / ASME SA312 Table 1, TP347 row ≤ heat-analysis acceptance limits. Confirm the values against the ordered edition and the MTC.
Typical Mechanical Properties
Grade TP347 offers a balance of strength and ductility, making it a reliable solution for various industrial applications.
| 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 across a range of environments.
| 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 Ω·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.
Size Tolerance Chart (mm)
| NPS Designator (Inches) | Permissible Variations in Outside Diameter (Inches) |
| 1⁄8 to 1 1⁄2, inclusive | Over: 1⁄64 in. (0.015 in.) |
| Under: 1⁄32 in. (0.031 in.) | |
| Over 1 1⁄2 to 4, inclusive | Over: 1⁄32 in. (0.031 in.) |
| Under: 1⁄32 in. (0.031 in.) | |
| Over 4 to 8, inclusive | Over: 1⁄16 in. (0.062 in.) |
| Under: 1⁄32 in. (0.031 in.) | |
| Over 8 to 18, inclusive | Over: 3⁄32 in. (0.093 in.) |
| Under: 1⁄32 in. (0.031 in.) | |
| Over 18 to 26, inclusive | Over: 1⁄8 in. (0.125 in.) |
| Under: 1⁄32 in. (0.031 in.) | |
| Over 26 to 34, inclusive | Over: 5⁄32 in. (0.156 in.) |
| Under: 1⁄32 in. (0.031 in.) | |
| Over 34 to 48, inclusive | Over: 3⁄16 in. (0.187 in.) |
| Under: 1⁄32 in. (0.031 in.) |
Tolerance basis: permitted variations per the governing specification stated on this page and the applicable general-requirements standard (ASTM A999 / ASME SA999) for the ordered product form; the wall-thickness and length variations in this section follow the same basis.
The wall thickness tolerances are defined by the nominal wall thickness (t) and the outside diameter (D).
1. Minimum Wall Thickness
The minimum wall thickness at any point on the pipe shall not be more than {12.5%} under the nominal (specified) wall thickness.
2. Maximum Wall Thickness (Percentage Over Nominal)
The maximum allowable wall thickness variation depends on the size and the t/D ratio (ratio of nominal wall thickness to ordered outside diameter):
| NPS Designator (Inches) | t/D Ratio | Permissible Variation (Over Nominal WT) |
| 1/8 to 2, inclusive | All ratios | +20.0% |
| 3 to 18, inclusive | t/D ≤ 5% | +22.5% |
| 3 to 18, inclusive | t/D >5% | +15.0% |
| 20 and larger (Seamless) | t/D ≤ 5% | +22.5% |
| 20 and larger (Seamless) | t/D >5% | +15.0% |
| 20 and larger (Welded) | All ratios | +17.5% |
For pipe ordered to a Specific Cut Length, the standard tolerance is +1⁄8 in. [3.2 mm], -0 in. [0 mm].
Pipe is typically supplied in Single Random Lengths (17 to 24 ft) or Double Random Lengths (38 to 40 ft), unless otherwise specified.
Disclaimer: These tolerances are based on ASTM A999/A999M general dimensional requirements commonly referenced by ASTM A312 and ASTM A790. The full and most current specification document must always be consulted for official design and procurement purposes.
Common Industrial Applications
The combination of superior corrosion resistance and high-temperature stability makes TP347 stainless steel seamless pipes a preferred choice for:
Aerospace
Used in jet engine parts, exhaust manifolds, and afterburners due to its high-temperature strength.
Chemical Processing
In systems handling corrosive chemicals and gases at high temperatures.
Thermal Oxidizers and Boilers
For components that are exposed to high heat and corrosive conditions.
Food Processing
In environments where cleanliness is crucial and piping is exposed to heat.
Frequently Asked Questions
What sizes are available for TP347 seamless pipe?
The overall range is OD 6–1016 mm; WT 0.5–65 mm. Requirements outside this range are reviewed against mill capability on request.
Which specification governs TP347 seamless pipe?
ASTM A312 / ASME SA312 is the governing specification for TP347 seamless pipe. 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 NPS and schedule (or actual OD and wall), 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 tube form, see the TP347 seamless tube. To compare other grades and size combinations, browse the Stainless Steel Seamless Tube category. Minimum order quantity and lead time are confirmed on enquiry against the ordered grade, size and quantity.
