ASTM A376 TP347H seamless high temperature steel pipe for power plants
Gnee Steel
ASTM A376 TP347H seamless high temperature steel pipe for power plants
ASTM A376 TP347H is a seamless, austenitic stainless steel pipe designed for high-temperature power plant applications, such as superheater and reheat lines. Key properties include excellent resistance to creep, oxidation, and intergranular corrosion, thanks to niobium (columbium) stabilization and a high carbon content, which prevents chromium carbide precipitation. These pipes must be heat treated to meet specifications and undergo various tests to ensure quality.
Gnee Steel
What is the difference between 347 and 347H?
The primary difference between 347 and 347H is that 347H has a higher carbon content, which gives it better high-temperature performance. Both alloys are nonmagnetic and can be used in applications where magnetic properties are a concern. Due to the higher carbon content, 347H is more expensive than 347.
Chemical Composition of TP347H (UNS S34709) Pipe
| 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) Tubing
| 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 Piping 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 Pipe - Application Benefits
1. Superior High-Temperature Performance in Power Plants
Excellent creep resistance at temperatures up to 750°C (1382°F) - ideal for superheater and reheater applications
Excellent oxidation resistance ensures long-term stability in high-temperature flue gas environments
2. Enhanced Safety and Reliability of Critical Systems
Seamless construction provides uniform wall thickness, eliminating weak points under extreme pressure conditions
Niobium-stabilized content prevents intergranular corrosion during continuous high-temperature operation
3. Cost-Effective Power Generation Solution
Extended service life, reduced maintenance frequency, and reduced replacement costs
Optimized thermal efficiency helps power plants maintain optimal operating parameters
4. Material Properties Support Power Applications
High-Temperature Strength ensures structural integrity under thermal cycling conditions
Corrosion Resistance: Suitable for a variety of fuel types, including coal, natural gas, and biomass
5. G Quality Assurance
Fully compliant with ASTM A376/ASME SA376 specifications
Fully tested, including hydrostatic, ultrasonic, and eddy current testing
Custom sizes available from 1/2" to 24" OD, with various thickness specifications
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
