347H Stainless Steel Flat Bar: Strength and High-Temperature Performance

In industries where materials must withstand extreme temperatures and mechanical stress, stainless steels with enhanced stability and strength play a vital role. One such material is the 347H Stainless Steel Flat Bar, a high-performance stainless steel product widely utilized in sectors such as petrochemical, power generation, and aerospace. Its unique composition and mechanical properties make it particularly suitable for environments that demand both corrosion resistance and high-temperature durability.

This article explores the characteristics, mechanical properties, advantages, and applications of 347H Stainless Steel Flat Bar, highlighting why it has become a preferred choice in critical industries.

What is 347H Stainless Steel?

Type 347H is an austenitic stainless steel that contains niobium, which enhances its resistance to intergranular corrosion. The “H” in 347H indicates its high carbon content compared to standard 347 stainless steel. This higher carbon content improves creep resistance, tensile strength, and performance at elevated temperatures.

The addition of niobium stabilizes the steel against chromium carbide precipitation, which otherwise weakens corrosion resistance. This property makes 347H Stainless Steel Flat Bar ideal for prolonged service in environments ranging between 427°C (800°F) and 816°C (1500°F).

Key Features of 347H Stainless Steel Flat Bar

1. High-Temperature Strength

   • The elevated carbon content enhances strength at high temperatures, making it suitable for boiler, heater, and furnace applications.

2. Excellent Corrosion Resistance

   • The niobium stabilisation prevents sensitisation, maintaining excellent resistance to intergranular corrosion even after welding.

3. Creep and Stress Rupture Resistance

   • 347H demonstrates better creep and stress rupture properties than standard grades, allowing it to maintain performance under prolonged stress at elevated temperatures.

4. Good Weldability and Fabrication

   • Despite the higher carbon content, the alloy maintains good weldability using standard methods, making it versatile for various industrial applications.

5. Oxidation Resistance

   • It offers outstanding resistance to oxidation and scaling at temperatures up to 1000°C (1832°F) in intermittent service and 870°C (1600°F) in continuous service.

Mechanical Properties of 347H Stainless Steel Flat Bar

• Tensile Strength (MPa): 515 minimum

• Yield Strength (MPa): 205 minimum

• Elongation (%): 40 minimum

• Hardness (Brinell): 201 maximum

These properties highlight its ability to perform under mechanical stress while offering ductility for shaping and machining.

Chemical Composition of 347H Stainless Steel

• Carbon (C): 0.04 – 0.10%

• Chromium (Cr): 17.0 – 20.0%

• Nickel (Ni): 9.0 – 13.0%

• Niobium + Tantalum (Nb + Ta): 10 x C – 1.0%

• Manganese (Mn): 2.0% max

• Silicon (Si): 1.0% max

• Phosphorus (P): 0.045% max

• Sulfur (S): 0.030% max

This balanced composition ensures high corrosion resistance and thermal stability.

Advantages of 347H Stainless Steel Flat Bar

• Durability in Extreme Heat: Its resistance to creep and rupture makes it perfect for use in furnaces, boilers, and reactors.

• Corrosion Resistance: Niobium stabilization ensures resistance to sensitization and intergranular corrosion.

• Fabrication Flexibility: Can be easily welded, cut, and shaped without compromising performance.

• Long Service Life: With excellent mechanical and corrosion-resistant properties, it ensures long-term reliability and reduced maintenance costs.

• Oxidation Resistance: Its ability to resist scaling at high temperatures adds to its reliability in harsh environments.

Applications of 347H Stainless Steel Flat Bar

Due to its strength and corrosion resistance at elevated temperatures, 347H Stainless Steel Flat Bar is used in various demanding industries:

1. Petrochemical Industry

   • For refinery equipment, catalytic crackers, and piping systems handling high-temperature fluids.

2. Power Generation

   • Widely used in superheaters, reheaters, and boiler tubes in thermal power plants.

3. Aerospace and Aviation

   • Suitable for exhaust manifolds, jet engine components, and high-stress airframe parts.

4. Chemical Processing

   • Used in heat exchangers, reactors, and pressure vessels exposed to harsh chemicals and elevated temperatures.

5. Food Processing Equipment

   • Its resistance to corrosion and scaling makes it reliable in equipment used for processing acidic or high-temperature food products.

6. Furnace Parts

   • Commonly used in furnace structural components, burner nozzles, and radiant tubes.

Comparison: 347 vs 347H Stainless Steel

While both 347 and 347H offer excellent corrosion resistance due to niobium stabilization, the difference lies in their carbon content.

• 347: Lower carbon content, better weldability, and general corrosion resistance.

• 347H: Higher carbon content, improved creep strength, and high-temperature performance.

This makes 347H Stainless Steel Flat Bar the preferred choice in applications where high-temperature strength is essential.

Maintenance and Care

To ensure the longevity and consistent performance of 347H Stainless Steel Flat Bar, industries must follow certain maintenance practices:

• Regular Cleaning: Prevents surface deposits that may cause localized corrosion.

• Proper Welding Techniques: Use low-carbon filler materials to avoid carbide precipitation.

• Inspection: Regular inspection of high-temperature equipment ensures early detection of stress cracks or scaling.

Why Choose 347H Stainless Steel Flat Bar?

When selecting a stainless steel grade for high-temperature applications, 347H stands out due to its unique combination of strength, corrosion resistance, and long-term reliability. It provides an excellent balance between performance and cost-effectiveness, making it the material of choice for industries where operational safety and durability are critical.

Whether used in refinery piping, aerospace engines, or power plant boilers, the 347H Stainless Steel Flat Bar delivers exceptional results and ensures reliable performance under extreme working conditions.

Conclusion

The 347H Stainless Steel Flat Bar is more than just a material—it is a solution for industries that demand strength, high-temperature resistance, and durability. Its ability to withstand corrosive environments and extreme heat without losing mechanical integrity makes it a trusted choice for engineers and manufacturers worldwide.

By offering superior creep strength, oxidation resistance, and long service life, 347H proves itself as one of the most reliable stainless steel grades available today. For any application requiring both performance and longevity under extreme conditions, 347H Stainless Steel Flat Bar is an ideal investment.