Views: 0 Author: Site Editor Publish Time: 2025-03-19 Origin: Site
Stainless Steel 347H (UNS S34709) is a stabilized austenitic stainless steel designed for high-temperature applications. The "H" designation indicates enhanced high-temperature strength due to controlled carbon content, making it ideal for environments requiring resistance to creep, oxidation, and corrosion.
Key elements include:
- Chromium (Cr): 17–19% (provides oxidation resistance).
- Nickel (Ni): 9–13% (ensures austenitic structure and ductility).
- Niobium (Nb) + Tantalum (Ta): ~10× carbon content (stabilizes against carbide precipitation during welding).
- Carbon (C): 0.04–0.10% (higher than standard 347, boosting high-temperature strength).
This stabilization prevents sensitization (intergranular corrosion) in welded components.
1. High-Temperature Performance
- Retains strength and oxidation resistance up to **1500°F (816°C)**.
- Superior creep resistance under sustained loads at elevated temperatures.
2. Corrosion Resistance
- Resists general corrosion, pitting, and stress corrosion cracking.
- Performs well in acidic, chloride-rich, and sulfur-containing environments.
3. Mechanical Properties
- Tensile Strength: ≥515 MPa (75 ksi) at room temperature.
- Yield Strength: ≥205 MPa (30 ksi).
- Elongation: ≥40% (excellent ductility).
Common in industries requiring durability under thermal stress:
- Power Generation: Boiler tubes, superheaters, heat exchangers.
- Petrochemical: Pressure vessels, furnace parts, catalytic systems.
- Aerospace: Exhaust systems, gas turbine components.
- Nuclear: Reactor internals and piping.
- Welding: Use 347H filler metal; post-weld annealing optional for severe conditions.
- Machining: Prone to work hardening; use sharp tools and moderate speeds.
- Thermal Expansion: Higher than carbon steels (critical in high-temperature design).
- Heat Treatment: Solution anneal at 1900–2100°F (1038–1149°C) followed by rapid cooling.
- ASTM: A240 (plates), A312 (pipes), A358 (welded tubes).
- ASME: Compliant with Boiler and Pressure Vessel Code, Section VIII.
- Equivalent Grades: EN 1.4961, SUS 347H.
- Vs. 304/316H: Better intergranular corrosion resistance post-welding.
- Vs. 321H: Superior high-temperature strength due to niobium stabilization.
Stainless Steel 347H is a versatile choice for high-temperature and corrosive environments, combining stabilization, creep resistance, and ease of fabrication. Its optimized composition makes it indispensable in critical engineering applications where reliability under thermal stress is paramount.
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