Stainless Steel 347 / 347H Pipe
Columbium Stabilized Austenitic Stainless Steel Pipes
SS 347 Pipe is an austenitic stainless steel stabilized by the addition of Niobium (Columbium) and Tantalum. This stabilization allows the material to be used in temperatures ranging from 427°C to 816°C without risk of intergranular corrosion or carbide precipitation. Grade 347H is the high-carbon variant, providing superior creep resistance and strength for heavy-duty thermal applications in power plants and refineries.
Technical Specifications
| Feature | Details |
|---|---|
| Standards | ASTM A312, A358, A213, A269 |
| Grades | TP 347, TP 347H |
| Size Range | 1/4" NB to 24" NB (Seamless), up to 72" (Welded) |
| Schedules | SCH 10, 40, 80, 160, XXS |
| Type | Seamless / ERW / EFW / Welded / Fabricated |
| Testing | Hydrostatic, Eddy Current, HIC, Intergranular Corrosion |
Mechanical Properties
| Property | Grade 347 | Grade 347H |
|---|---|---|
| Yield Strength (0.2% Offset) | Min 205 MPa | Min 205 MPa |
| Tensile Strength (Min) | 515 MPa | 515 MPa |
| Elongation (Min %) | 35 - 40% | 35 - 40% |
| Hardness (Rockwell B) | Max 92 HRB | Max 92 HRB |
Chemical Composition (%)
| Element | SS 347 | SS 347H |
|---|---|---|
| Carbon (C) | 0.08 max | 0.04 - 0.10 |
| Manganese (Mn) | 2.00 max | 2.00 max |
| Chromium (Cr) | 17.0 - 19.0 | 17.0 - 19.0 |
| Nickel (Ni) | 9.0 - 13.0 | 9.0 - 13.0 |
| Silicon (Si) | 0.75 max | 0.75 max |
| Phosphorus (P) | 0.045 max | 0.045 max |
| Sulfur (S) | 0.030 max | 0.030 max |
| Nitrogen (N) | 0.10 max | 0.10 max |
| Niobium (Nb) + Ta | 10 x C min - 1.10 max | 8 x C min - 1.10 max |
Features and Benefits of SS 347 Pipe
- Excellent resistance to intergranular corrosion in the carbide precipitation range
- Niobium stabilization makes it superior to Grade 321 for high-heat environments
- High creep and stress rupture properties (Grade 347H)
- Exceptional mechanical properties at both low and high temperatures
- Resistant to polythionic acid stress corrosion cracking
- Superior weldability with minimal risk of sensitization
- Better high-temperature oxidation resistance than SS 304
- Reliable performance in strong oxidizing environments
Applications & Uses
Power Gen
Used in radiant superheaters, boiler tubes, and high-pressure steam pipes.
Oil Refining
Essential for catalytic cracking units and hydro-desulfurization equipment.
Aviation
Applied in aircraft exhaust manifolds and collector rings exposed to extreme heat.