ASTM A403 WP347H
ASTM A403 WP347H Pipe Fittings
ASTM A403 WP347H is a high-carbon, niobium-stabilized austenitic stainless steel grade used for high-temperature and high-pressure applications. The “H” grade provides enhanced creep strength, stress-rupture resistance, and long-term stability in elevated-temperature environments.
Stabilized with niobium (columbium), WP347H offers superior resistance to carbide precipitation and intergranular corrosion, especially after welding. These properties make it ideal for petrochemical, refinery, power generation, furnace, steam piping, and thermal equipment applications.
Key Features
Niobium stabilized for excellent intergranular corrosion resistance
High-carbon version for superior high-temperature strength
Excellent creep strength & stress-rupture resistance
Ideal for 600°C – 900°C continuous high-temperature service
Improved weldability and structural stability
Strong resistance to oxidation, scaling & carburizing media
Long service life in aggressive thermal & corrosive conditions
Technical Specification
| Specification | Details |
|---|---|
| Standard | ASTM A403 / ASME SA403 |
| Grade | WP347H |
| UNS | S34709 |
| Material | Niobium Stabilized Austenitic Stainless Steel |
| Size Range | ½” to 48” |
| Thickness | SCH 10S – SCH XXS |
| Forms | Seamless / Welded / Fabricated |
| Dimensional Standards | ASME B16.9 / B16.28 / MSS-SP-43 |
| Ends | Beveled / Plain End |
Equivalent Grades
| Standard | Grade |
|---|---|
| ASTM / ASME | A403 / SA403 WP347H |
| UNS | S34709 |
| EN | 1.4912 |
| DIN | X8CrNiNb18-10 |
Available Sizes
1/2” to 48”
Thickness: SCH 10S – SCH XXS
Options: Seamless / Welded / Fabricated
Chemical Composition
| Element | % |
|---|---|
| Carbon (C) | 0.04 – 0.10 |
| Chromium (Cr) | 17.0 – 19.0 |
| Nickel (Ni) | 9.0 – 13.0 |
| Niobium (Nb + Ta) | ≥ 10 × C% (0.10 – 1.10) |
| Manganese (Mn) | ≤ 2.00 |
| Silicon (Si) | ≤ 1.00 |
| Phosphorous (P) | ≤ 0.045 |
| Sulfur (S) | ≤ 0.030 |
| Nitrogen (N) | ≤ 0.10 |
| Iron (Fe) | Balance |
Mechanical Properties
| Property | Value |
|---|---|
| Tensile Strength | ≥ 515 MPa |
| Yield Strength | ≥ 205 MPa |
| Elongation | ≥ 40% |
| Hardness | ≤ 217 HB |
Physical Properties
| Property | Value |
|---|---|
| Density | 7.9 g/cm³ |
| Melting Range | 1400 – 1455°C |
| Thermal Conductivity | 16 W/m-K |
| Specific Heat | 500 J/kg-K |
| Modulus of Elasticity | ~193 GPa |
Types of WP347H Fittings
ASTM A403 WP347H Elbow
ASTM A403 WP347H Tee
ASTM A403 WP347H Reducers
ASTM A403 WP347H Caps
ASTM A403 WP347H Cross Fittings
ASTM A403 WP347H Nipples
ASTM A403 WP347H Couplings
ASTM A403 WP347H Stub Ends
Corrosion Resistance
Excellent resistance to intergranular corrosion post-welding
Superior protection against carbide precipitation
Resistant to oxidizing & corrosive atmospheres
Performs well in chloride & acidic media
Heat Resistance
Reliable performance in up to 900°C service
High-temperature strength & creep resistance
Performs well in thermal cycling environments
Suitable for steam & furnace systems
Heat Treatment
| Process | Details |
|---|---|
| Solution Annealing | 1010°C – 1120°C |
| Cooling | Rapid air / water quench |
Welding
Excellent weldability with TIG, MIG, SMAW
Niobium stabilization prevents sensitization
No preheat required
Recommended fillers — ER347 / E347
Fabrication
Good formability & machinability
Cold forming followed by annealing recommended
Use carbide tooling for machining
Applications
Petrochemical & Refinery Piping Systems
Boilers, Superheaters & Heat Exchangers
Power Generation & Steam Lines
Chemical Processing Equipment
Furnace Components & Thermal Plants
Oil & Gas Pipelines
Exhaust & High-Temp Gas Handling Systems