F347 Valve Manufacturer in Germany
F347 valves are used in elevated-temperature piping systems where resistance to sensitization and intergranular corrosion after welding or thermal exposure is important. ASTM A182 F347 is a forged austenitic stainless-steel grade associated with UNS S34700 and stabilized primarily with niobium.
F347 Valve Construction for Elevated Temperatures
F347 is selected where an 18Cr-8Ni-type stainless steel must retain resistance to intergranular corrosion following exposure to sensitizing temperatures.
Niobium stabilization reduces the availability of carbon to form chromium carbides at grain boundaries.
This helps preserve chromium near the grain boundaries and reduces susceptibility to intergranular corrosion following:
- Welding
- High-temperature operation
- Repeated thermal cycling
F347 is therefore used for forged pressure-containing valve components and high-temperature piping equipment where ordinary unstabilized grades may require additional consideration.
Niobium Stabilized Stainless Steel Properties
F347 is an austenitic stainless steel stabilized using niobium, with tantalum permitted within the applicable chemistry requirements.
The stabilizing addition forms stable carbides preferentially, helping reduce chromium-carbide precipitation.
Benefits include:
- Resistance to sensitization
- Good high-temperature strength
- Good oxidation resistance
- Weldability
- Resistance to intergranular corrosion after suitable thermal exposure
Outokumpu identifies 347/S34700 as a niobium-stabilized stainless steel intended for applications involving elevated or intermittent temperatures and lists valves among its typical applications.
ASTM A182 F347 Material Composition
Typical ASTM A182 F347 chemistry includes:
| Element | Typical ASTM Limit / Range |
| Carbon | 0.08% max |
| Chromium | 17–19% |
| Nickel | 9–13% |
| Manganese | 2.00% max |
| Silicon | 1.00% max or applicable specification limit |
| Phosphorus | 0.045% max |
| Sulfur | 0.030% max |
| Niobium + Tantalum | Stabilizing addition according to specification |
| Iron | Balance |
Gate, Globe, Ball and Check Configurations
- F347 Gate Valve: Full open/full-close isolation for elevated-temperature service.
- F347 Globe Valve: Linear throttling and repeated isolation.
- F347 Ball Valve: Quarter turn isolation in floating or trunnion designs.
- F347 Check Valve: Automatic reverse flow prevention using swing or dual-plate designs.
- F347 Butterfly Valve: Compact rotary isolation or flow regulation.
Technical Specifications
| Parameter | Typical Specification |
| Forged Material | ASTM A182 F347 |
| UNS | S34700 |
| EN Comparable Grade | 1.4550 |
| Valve Types | Ball, Butterfly, Check, Gate, Globe |
| Size Range | DN15–DN600 in the currently listed category range; larger project sizes design-dependent |
| Pressure Rating | ASME Class 150–2500 depending on valve design |
| End Connections | RF/RTJ Flanged, Butt Weld, Socket Weld, Threaded |
| Seats / Trim | F347, stainless trim, hard-facing or service-specific materials |
| Operation | Handwheel, Lever, Gear, Pneumatic or Electric |
| Pressure Design | ASME B16.34 where applicable |
| Face to Face | ASME B16.10 or valve specific requirement |
| Testing | API 598 / EN 12266-1 where applicable |
| Documentation | EN 10204 3.1/3.2 where specified |
Resistance to Sensitization and Intergranular Corrosion
When conventional austenitic stainless steel is exposed to certain elevated-temperature ranges, chromium carbides can precipitate along grain boundaries.
This locally reduces chromium content and may increase susceptibility to intergranular corrosion.
In F347, niobium preferentially combines with carbon and helps reduce this mechanism.
The benefit is particularly relevant for:
- Welded components
- Thermal cycling
- Elevated-temperature piping
- Components that cannot be solution annealed after fabrication
F347 should nevertheless be evaluated against the actual process corrosion environment because stabilization does not provide universal resistance to every acid, chloride or reducing medium.
Manufacturing and Heat Treatment Controls
Performance depends on preserving the specified material condition throughout manufacturing.
Important controls include:
- Verified ASTM A182 F347 raw material
- Heat-number traceability
- Qualified forging procedures
- Controlled heat treatment
- Machining without cross-contamination
- Qualified welding procedures where welding is required
- Proper filler material
- Controlled thermal exposure
Testing can include:
- PMI
- Tensile/hardness verification where required
- Liquid-penetrant examination
- UT or RT according to component and project requirements
- Intergranular corrosion testing where specified
- Hydrostatic and seat testing
Avoid stating that every valve is RT/UT tested unless this is actually a standard production requirement.
High Temperature Process Applications
F347 valves are used in:
- Petrochemical plants
- Power generation systems
- High temperature steam systems
- Chemical processing
- Heat transfer systems
- Thermal cycling service
- Hot hydrocarbon lines
- Industrial utility systems
The valve’s maximum service temperature should be determined from ASME allowable stresses, valve design, pressure class, seat material and process conditions, rather than assigning one universal 800°C or 900°C rating to every F347 valve.
