ASME SA213 TP347 / UNS S34700 Stainless Steel Seamless Tube Heat Exchanger Tube
ASTM A213 / ASME SA213 TP347 Stainless Steel Seamless Tube Pickled Annealed Heat Exchanger Tube
The key of stainless steel 347 is the addition of Columbium (Niobium, Cb), typically at a minimum of 10x the carbon content. This element preferentially combines with carbon to form stable carbides, preventing chromium carbide formation. TP347 is a stabilized grade. This stabilization is its primary advantage over TP304/304H and TP316/316H. It prevents sensitization (chromium depletion at grain boundaries) during exposure in the 425-850°C (800-1560°F) range, which can lead to intergranular corrosion.
Stainless steel 347 VS stainless steel 347H
The choice between TP347 and TP347H depends primarily on the design temperature and required creep strength. When procuring, specifying the correct grain size (H vs non-H) and relevant supplemental tests (especially intergranular testing) is essential for ensuring performance in severe service.
Do not substitute one for the other without a thorough engineering review.
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Using standard 347 where 347H is specified could lead to premature creep failure and rupture under high stress at temperature.
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Using 347H where standard 347 is specified is often overkill, may be more expensive, and the coarse grain structure offers slightly lower yield strength at room temperature, which could be a design consideration for fabrication.
The "H" is a specific pedigree for the most demanding high-temperature, high-stress environments in the energy and process industries.
ASME SA213 TP347 Stainless Steel Seamless Tube Equivalent Grade
| STANDARD | WERKSTOFF NR. | UNS |
|---|---|---|
| SS 347 | 1.4550 | S34700 |
ASME SA213 TP347 Stainless Steel Seamless Tube Mechanical Properties
| Element | TP 347 |
|---|---|
| Density | 8.0 g/cm3 |
| Melting Range | 1454 °C (2650 °F) |
| Tensile Stress | Psi – 75000 , MPa – 515 |
| Yield Stress (0.2%Offset) | Psi – 30000 , MPa – 205 |
| Elongation | 35 % |
| Hardness (Brinell) | 201 |
ASME SA213 TP347 Stainless Steel Seamless Tube Chemical Composition
| TP347 | Maximum | Minimum |
|---|---|---|
| Ni | 13.00 | 9.00 |
| C | 00.08 | 00.04 |
| Mn | 2.00 | – |
| P | 00.045 | – |
| S | 00.030 | – |
| Si | 1.00 | – |
| Cr | 20.0 | 17.0 |
| Mo | 3 – 4 | – |
| N | – | – |
| OTHER | 1.0 | Nb=10(C+N) |
Application
Primary Applications:
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Power Generation Boilers:
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Superheater & Reheater Tubing (primary use) – Where steam temperatures exceed 500°C (930°F).
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Resists flue gas corrosion and creep failure over decades of operation.
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Petrochemical & Refining:
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Furnace tubing in ethylene crackers, reformer furnaces, and other high-temperature process heaters.
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Handles hot process gases (hydrocarbons) up to ~815°C (1500°F).
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Heat Exchangers:
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In severe service where thermal cycling and sensitization (chromium carbide precipitation) are concerns.
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