ASTM A312 TP347H Stainless Steel Seamless Pipe
Jan 26, 2026
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What is ASTM A312 TP347H?
ASTM A312 TP347H is the high-carbon Nb-stabilized austenitic stainless steel seamless pipe, designed for maximum high-temperature creep strength, used in critical high-temp pressure systems.
Equivalent Grades (Horizontal)UNS: S34709 | JIS: SUS347H | GB: 07Cr18Ni11Nb | EN: X7CrNiNb18-10 | W.Nr.: 1.4550
Chemical Composition (wt%, Horizontal)C: 0.04-0.10 | Si: ≤1.00 | Mn: ≤2.00 | P: ≤0.045 | S: ≤0.030 | Cr: 17.00-19.00 | Ni: 9.00-13.00 | Nb+Ta: ≥10×C | Fe: Balance
Key Properties (20°C, Annealed, Horizontal)Density: 7.93g/cm³ | Melting Point: 1400-1450°C | Tensile Strength: ≥515N/mm² | Yield Strength: ≥205N/mm² | Elongation: ≥40% | Hardness: ≤201HB
Core Characteristics
Excellent high-temperature creep strength (600-900°C)
Outstanding post-weld corrosion resistance
Mandatory post-weld annealing
For critical high-temp, high-stress piping (power, nuclear)
TP347 vs TP347H (Horizontal)Carbon: 347 (≤0.08%) | 347H (0.04-0.10%) | Creep: 347 (Good) | 347H (Excellent) | Annealing: 347 (Optional) | 347H (Mandatory)
| Element | 347 | 347H |
| Chromium | 17.00 min.-19.00 max. | 17.00 min.-19.00 max. |
| Nickel | 9.00 min.-13.00 max. | 9.00 min.-13.00 max. |
| Carbon | 0.08 | 0.04 min.-0.10 max. |
| Manganese | 2.00 | 2.00 |
| Phosphorus | 0.045 | 0.045 |
| Sulfur | 0.03 | 0.03 |
| Silicon | 0.75 | 0.75 |
| Columbium & Tantalum | 10 x (C + N) min.-1.00 max. | 8 x (C + N) min.-1.00 max. |
| Iron | Balance | Balance |
Stainless Steel Suppliers
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Testing and Documentation: Factory test certificate, EN 10204 3.1, chemical report, mechanical report, destructive testing report, non-destructive testing report, PMI test report, visual inspection report, third-party inspection report, NABL certified laboratory report.
Packaging: Wooden crate packaging, bubble wrap packaging, steel strapping, or packaging according to customer requirements.
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