347/347H
Wst. 1.4550/1.4912
UNS S34700/S34709
Stock program: Available on request
Specification: ASTM A 269/A 213/A 312
EN10216-5 /EN ISO 1127 D4/T3/EN 10305
PED 97/23 EC
Maximum exposure temperature: 850°C / 1560°F
Alloy 347 is an austenitic, niobium, stabilized stainless chromium-nickel steel. It has slightly imposed corrosion resistance over 321 stainless steel in strongly oxidizing environments and is preferable for aqueous and low temperature environments due to its good resistance to inter granular attack. The 347H has high carbon (0.4 to 0.1%) for better high temperature creep properties.
Characteristics:
- Excellent resistance to inter granular corrosion due to niobium stabilization
- Good resistance to organic aids and salt solutions
- Sensitive to pitting and crevice corrosion
- Less resistance to stress corrosion crashing by chloride solutions
Market applications:
- Oil refineries
- Fires heater tubes
- Power plants
- Heat exchanges
- High chemical process
- High temperature stream service
Technical details
| Technical composition (%) | Fe | Cr | Ni | Mn | Si | P | C | S | Nb | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 347 | min | Bal. | 17.0 | 9.0 | – | – | – | 0.040 | – | 8xC | |||||||||
| max | – | 20.0 | 13.0 | 2.00 | 0.75 | 0.040 | 0.080 | 0.030 | 0.8 | ||||||||||
| 347H | min | Bal. | 17.0 | 9.0 | – | – | – | 0.040 | – | 10xC | |||||||||
| max | – | 20.0 | 13.0 | 2.00 | 0.75 | 0.040 | 0.100 | 0.030 | 1.0 | ||||||||||
| Mechanical properties | 347 | 347H | ||
|---|---|---|---|---|
| Tensile strenght (mpa, min) nl | 515 – 690 | 515 – 740 | ||
| Yield strength (0.2% offset mpa, min) | 215 – 260 | 215 – 260 | ||
| Elongation (%, min) | 40 | 40 | ||
| Density / weight (g / cm3 / kg) | 7.9 | 7.9 |