Alloy 347H steel plate is a high-carbon austenitic stainless steel (UNS S34709, DIN 1.4550) stabilized with niobium (Nb), designed to excel in high-temperature environments while maintaining good corrosion resistance and mechanical properties. Below is a detailed overview of its key characteristics, performance advantages, and application fields:

Key Characteristics of Alloy 347H Steel Plate

1. Chemical Composition

Chromium (17.0%-19.0%): Provides excellent oxidation resistance, forming a protective chromium oxide film to resist high-temperature corrosion.

Nickel (9.0%-13.0%): Stabilizes the austenitic structure, ensuring ductility and toughness at both high and low temperatures.

Niobium (Nb + Ta, 8×C min. to 1.0%): The core stabilizing element, which reacts with carbon to form niobium carbides (NbC), preventing chromium carbide precipitation at grain boundaries (a common issue in unstabilized steels like 304). This avoids "sensitization" and intergranular corrosion, especially after welding or high-temperature exposure.

Carbon (0.04%-0.10%): Higher than standard 347 (≤0.08%), enhancing high-temperature strength (e.g., creep resistance) through solid solution strengthening and carbide formation.

Manganese (≤2.0%), Silicon (≤0.75%): Trace elements that aid in deoxidation and improve processability.

Performance Advantages

1. High-Temperature Stability

Creep and rupture strength: Superior to 304H and 316H at temperatures up to 800°C, making it suitable for long-term service under high-temperature, high-pressure conditions (e.g., in boilers or heat exchangers).

Resistance to sensitization: Niobium stabilizes carbon, preventing chromium depletion at grain boundaries during welding or annealing, thus avoiding intergranular corrosion in corrosive environments (e.g., aqueous solutions or high-temperature gases).

2. Corrosion Resistance

Good resistance to general corrosion, oxidation, and sulfidation in high-temperature atmospheres (e.g., industrial flue gases, steam).

Performs well in moderately corrosive media such as nitric acid, organic acids, and high-temperature water/steam systems.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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