ASTM A376 TP347H Seamless Tube Nb-Stabilized 515MPa Up to 900°C for Superheater Reheater Cracking Furnace
ASTM A376 TP347H Seamless Tube Nb-Stabilized 515MPa Up to 900°C for Superheater Reheater Cracking Furnace
| 347 vs 347H Comparison: | ||||
| Grade | UNS | C (%) | Grain Size | Primary Application |
| TP347 | S34700 | ≤0.08 | Finer | General service, moderate temperatures |
| TP347H | S34709 | 0.04–0.10 | ASTM No. 7 or coarser | High‑temperature creep service (>550°C) |
| Chemical Composition | ||||
| Element | Min (%) | Max (%) | Function Description | Standard Reference |
| C (Carbon) | 0.04 | 0.1 | Elevated carbon for coarse grain & creep strength | ASTM A376 |
| Mn (Manganese) | — | 2 | Deoxidation, hot workability | ASTM A376 |
| P (Phosphorus) | — | 0.045 | Cold brittleness control | ASTM A376 |
| S (Sulfur) | — | 0.03 | Hot brittleness control | ASTM A376 |
| Si (Silicon) | — | 1 | Oxidation resistance | ASTM A376 |
| Cr (Chromium) | 17 | 19 | Oxidation resistance & high‑temperature strength | ASTM A376 |
| Ni (Nickel) | 9 | 13 | Austenite structure stabilization | ASTM A376 |
| Nb (Niobium) + Ta (Tantalum) | 8×C | 1 | Stabilization – prevents sensitization | ASTM A376 |
| Mechanical Properties | ||
| Parameter | Requirement | Standard Reference |
| Tensile Strength (Rm) | ≥ 515 MPa (75 ksi) | ASTM A376 |
| Yield Strength (Rp0.2) | ≥ 205 MPa (30 ksi) | ASTM A376 |
| Elongation (longitudinal, 50mm gage length) | ≥ 35% | ASTM A376 |
| Hardness (Brinell) | ≤ 223 HB | ASTM A376 |
| Hardness (Rockwell B) | ≤ 95 HRB | ASTM A376 |
| Physical Properties | |||
| Parameter | Value | Unit | Standard Reference |
| Density | 7.7 – 8.03 | g/cm³ | ASTM A376 |
| Elastic Modulus (20°C) | ~195 | GPa | ASTM A376 |
| Thermal Conductivity | ~14.5 | W/(m·K) | ASTM A376 |
| Coefficient of Linear Expansion (20–300°C) | ~17.0 | ×10⁻⁶/°C | ASTM A376 |
| Specific Heat Capacity (20°C) | ~500 | J/(kg·K) | ASTM A376 |
| Electrical Resistivity | ~0.73 | μΩ·m | ASTM A376 |
| Melting Range | 1400 – 1425 | °C | ASTM A376 |
Application:
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Power Generation (core application): Superheaters and reheaters for supercritical and ultra‑supercritical power plant boilers; main steam piping; high‑temperature reheat piping
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Petrochemical Industry: Ethylene cracking furnace tubes; hydrogen conversion furnace tubes; refinery furnaces; high‑temperature piping systems
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Nuclear Industry: Non‑nuclear‑grade auxiliary piping systems within nuclear power plants requiring high‑temperature performance
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Industrial Heating: Heat treatment equipment, expansion joints, aircraft exhaust manifolds
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Heat Exchangers: High‑temperature thermal fluid piping and heat exchanger tube bundles exposed to cyclic thermal stress
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