ASTM A376 TP347H Seamless austenitic steel tubes for high-temperature environments in power plants
ASTM A376 TP347H is a specification for seamless austenitic stainless steel tubing suitable for high-temperature, high-pressure applications in power plants, such as superheaters and heat exchanger tubes. Its main characteristics are high-temperature strength and creep resistance, thanks to the stabilizing effect of niobium in the alloy, which prevents carbide precipitation. This tubing requires heat treatment and undergoes mechanical property and non-destructive testing, and can be hot-finished or cold-finished.
What are the uses of 347 stainless steel?
It is a low-carbon steel containing chromium, nickel, and manganese. This stainless steel has corrosion resistance comparable to 340. 347 round bars are widely used in industries such as food processing, chemical processing, and oil refining. In addition, round bars can also be used to manufacture molds for high-pressure die casting.
Chemical Composition of TP347H (UNS S34709)
| Element | Requirement (%) | Notes |
| Carbon (C) | 0.04–0.10 | Controlled for high-temperature stability |
| Manganese (Mn) | 2.00 max | |
| Phosphorus (P) | 0.045 max | |
| Sulfur (S) | 0.030 max | |
| Silicon (Si) | 1.00 max | |
| Nickel (Ni) | 9.0–13.0 | Austenite stabilizer |
| Chromium (Cr) | 17.0–19.0 | Oxidation resistance |
Mechanical Properties of TP347H (UNS S34709)
| Property | Requirement |
| Grade | TP347H |
| UNS Designation | S34709 |
| Tensile Strength, min | 75 ksi [515 MPa] |
| Yield Strength, min | 30 ksi [205 MPa] |
| Elongation in 2 in.., min | 35% (Longitudinal) |
TP347H Testing Requirements Summary
| Category | Test Type | Key Requirements |
| Pressure/NDE | Hydrostatic Test | Each pipe tested per A999/A999M (except NPS≥24 with NH marking) |
| NDE (UT/ET) | Mandatory for all pipes (manufacturer's method selection) | |
| Mechanical | Tensile Test | 1 test per lot (≤100 pipes); 2 tests for >100 pipes |
| Flattening Test | 5% of batch furnace pipes; min. 2 pipes for continuous process | |
| Chemical | Product Analysis | Required for each pipe length (individual rejection) |
| Special Tests | Transverse Tension | Mandatory for NPS≥8 pipes (each end) |
| Etching Test | Checks homogeneity per Method E381 | |
| Ultrasonic Test | Full-length scanning with calibration notches | |
| Intergranular Corrosion | Practice A262 (as-shipped/sensitized condition) |
ASTM A376 TP347H Seamless Austenitic Steel Tube - Application Advantages
1. Superior High-Temperature Performance, Suitable for Power Plants
Excellent creep resistance up to 750°C (1382°F) - ideal for superheater and reheater applications
Excellent oxidation resistance ensures long-term stable operation in high-temperature flue gas environments
2. Enhanced Safety and Reliability of Critical Systems
Seamless structure with uniform wall thickness eliminates weak points under extreme pressure conditions
Niobium-stabilizing composition prevents intergranular corrosion during continuous high-temperature operation
3. Cost-Effective Power Generation Solution
Extended service life, reduced maintenance frequency and replacement costs
Optimized thermal efficiency helps power plants maintain optimal operating parameters
4. Material Properties Supporting Power Applications
High-Temperature Strength: Maintains structural integrity under thermal cycling conditions
Corrosion Resistance: Suitable for various fuel types, including coal, natural gas, and biomass energy
Gnee Steel specializes in the production of a wide range of stainless steel products. Gnee Steel's product packaging includes: Steel Strapping: Pipes with an outer diameter of 3 inches or less are typically strapped together with polypropylene film to prevent rust during ocean shipping, and then secured with steel strapping. Wooden Cases/Crates: Pipes are typically packaged in wooden cases or crates to protect the pipes during transportation, especially those that are longer or have larger diameters. Seaworthy Export Packaging: Suppliers typically use standard seaworthy export packaging methods, which may include a variety of materials and techniques to protect the pipes during transportation. Tarpaulin Packaging: This prevents rain, seawater, and other external factors from penetrating the export crates during transportation. Gnee Steel specializes in the production and sale of alloy materials. Gnee Steel's products are widely used in the aerospace, chemical, power, automotive, and nuclear energy sectors, and we can provide customized alloy material solutions based on customer needs. For alloy material pricing or customized alloy material solutions, please contact us for a quote: ru@gneesteelgroup.com
