Alloy 347 (UNS S34700)
Alloy 347 is a niobium-stabilised austenitic stainless steel with excellent resistance to intergranular corrosion following exposure to temperatures in the chromium carbide precipitation range. The stabilisation enhances its suitability for welded components operating at elevated temperatures.
The alloy provides good oxidation resistance and maintains strength and toughness in high-temperature environments. Alloy 347 is commonly used in refinery equipment, chemical processing plants, and power generation applications requiring thermal stability.
Specifications
- UNS: S34700
- ASTM: A276, A182 F347, A240
- EN / DIN: 1.4550
- Structure: Austenitic (Niobium Stabilised)
- Condition Supplied: Annealed
Data Tables
Chemical Composition:
| C | Mn | P | S | Si | Cr | Ni | Ti | Mo | N | Cu | Fe | Co | Nb (+Ta) | V | W | Al | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Min | 17 | 9 | 10 X C | ||||||||||||||
| Max | 0.08 | 2 | 0.045 | 0.03 | 1 | 19 | 13 | 1 | 0.1 | Bal |
Mechanical Properties:
| Material Grade | ASTM Standard | Desgnation(EN /UNS) | Yield Strength (MPa) | Yield Strength (KSI) | Tensile Strength (MPa) | Tensile Strength (KSI) | Elongation (%) | Reduction of Area (%) | Hardness(HRC/HBWMax) | Condition | |
|---|---|---|---|---|---|---|---|---|---|---|---|
| SS 347/347H | ASTM A276 / A182 / A479 | EN 1.4550( S34709) | 205 | 29.73279 | 515 | 74.69457 | 30 | 40 | 237 HBW | Solution Annealed |
Physical Properties:
| Material Grade | Density (g/cm³) | Melting Range (°C) | Modulus of Elasticity (GPa) | Thermal Conductivity (W/m·K) | Thermal Expansion (×10⁻⁶ /°C) | Electrical Resistivity (µΩ·m) | Magnetic Behavior |
|---|---|---|---|---|---|---|---|
| 347 | 7.9 | 1400–1425 | 193 | 16 | 16 | 0.72 | Non-magnetic |
Key Features
- High-temperature pressure vessels
- Excellent resistance to weld-related intergranular corrosion
- Good oxidation resistance at elevated temperatures
- Retains strength and toughness under thermal cycling
- Suitable for heavy welded components
Applications
- Refinery and petrochemical equipment
- Boilers and superheaters
- High-temperature piping systems
- Chemical processing equipment
- Welded pressure components