Understanding SS 347H Flanges: Composition, Benefits & Applications
In industrial systems where temperature, pressure, and corrosion resistance determine performance, SS 347H flanges play a vital role. These stainless steel flanges are engineered for high-temperature service, offering exceptional stability and strength in conditions where other alloys often fail. Whether used in refineries, chemical plants, or power generation systems, ss 347h flanges ensure leak-proof connections and long-term operational reliability.
This guide explores the detailed composition, mechanical properties, benefits, types, applications, and quality considerations of ss 347h flanges. It also covers how these flanges are manufactured, tested, and maintained — empowering engineers and procurement professionals to make informed decisions.
What Makes SS 347H Flanges Unique?
SS 347H flanges are a high-carbon version of standard 347 stainless steel. The “H” stands for high carbon, typically in the range of 0.04–0.10 %, which enhances high-temperature strength and creep resistance. The alloy is stabilized with niobium (columbium) to prevent chromium carbide precipitation — a common cause of intergranular corrosion in stainless steels.
This makes ss 347h flanges particularly suitable for service in environments with sustained exposure to temperatures between 450°C and 900°C, where both oxidation and mechanical stress are severe.
Key Characteristics
- Excellent resistance to oxidation and corrosion.
- High creep and rupture strength at elevated temperatures.
- Retention of mechanical integrity under cyclic heating.
- Superior weldability and machinability.
- Stabilized microstructure to resist sensitization.
In short, ss 347h flanges combine durability and reliability for critical industrial connections.
Chemical Composition & Mechanical Properties
The composition of SS 347H flanges is precisely balanced to achieve the best combination of strength, ductility, and corrosion resistance.
| Element | Percentage (%) |
|---|---|
| Carbon (C) | 0.04 – 0.10 |
| Chromium (Cr) | 17.0 – 19.0 |
| Nickel (Ni) | 9.0 – 13.0 |
| Niobium (Cb/Ta) | 10×C – 1.0 |
| Manganese (Mn) | ≤ 2.0 |
| Silicon (Si) | ≤ 1.0 |
| Phosphorus (P) | ≤ 0.045 |
| Sulfur (S) | ≤ 0.030 |
| Iron (Fe) | Balance |
Mechanical Properties
- Tensile Strength: 515 MPa (minimum)
- Yield Strength: 205 MPa (minimum)
- Elongation: 35 %
- Hardness (Brinell): ~ 217 HB
- Melting Point: ~1457 °C
- Density: 8.0 g/cm³
These properties enable ss 347h flanges to maintain structural integrity in piping systems operating under high thermal and mechanical loads.
Benefits of SS 347H Flanges
High Temperature Strength
Due to higher carbon content, ss 347h flanges maintain superior mechanical properties in elevated temperature service — ideal for steam piping, heat exchangers, and boilers.
Corrosion and Oxidation Resistance
The chromium-nickel composition resists scaling, oxidation, and general corrosion, even when exposed to acidic or marine atmospheres.
Long Service Life
Their structural integrity minimizes downtime and replacement frequency, reducing total lifecycle costs for industrial systems.
Excellent Weldability
They can be welded by standard fusion and resistance methods, allowing easy fabrication and installation.
Availability in Multiple Types
SS 347H flanges are available in a variety of configurations, pressure ratings, and dimensions, ensuring compatibility with global piping standards.
Types & Standards of SS 347H Flanges
Common Types
- Weld Neck Flanges (WNRF): For high-pressure, high-temperature pipelines.
- Slip-On Flanges (SORF): Cost-effective and easy to install.
- Socket Weld Flanges (SWRF): Used in small-bore piping systems.
- Blind Flanges (BLRF): Seal the ends of piping systems.
- Threaded Flanges: Ideal for low-pressure or non-weld applications.
- Lap Joint & Stub End Flanges: Used in systems requiring frequent dismantling.
- Ring Type Joint (RTJ) Flanges: Provide leak-proof sealing in high-pressure conditions.
Applicable Standards
- ASTM A182 / ASME SA182 — Forged stainless steel flanges
- ANSI / ASME B16.5, B16.47 — Dimensional standards
- DIN, EN 1092, BS 4504, ISO, JIS
- Pressure Ratings: Class 150 to 2500 / PN6 to PN64
- Face Types: Raised Face (RF), Flat Face (FF), Ring Type Joint (RTJ)
By adhering to these global standards, manufacturers ensure interoperability and safety across industrial systems.
Applications Across Industries
6.1 Power Generation
Used in steam turbines, boilers, and superheater systems due to high creep strength.
6.2 Oil & Gas
Applied in refining, transport, and offshore rigs where corrosion and heat are constant challenges.
6.3 Petrochemical & Chemical Industries
Ideal for reactors, pressure vessels, and heat exchangers exposed to aggressive chemicals.
6.4 Marine & Shipbuilding
Resist chloride-induced corrosion and seawater exposure.
6.5 Food & Pharmaceutical
Ensure hygienic, corrosion-resistant connections under temperature-controlled processes.
6.6 Aerospace & Defense
Used in propulsion and exhaust systems requiring extreme thermal stability.
The adaptability of ss 347h flanges across industries underscores their engineering significance.
Testing & Quality Assurance
Every flange undergoes rigorous testing to confirm compliance with international quality norms.
Standard Tests Include:
- Visual & Dimensional Inspection
- Mechanical Testing — Tensile, hardness, and impact tests
- Non-Destructive Testing (NDT): Ultrasonic, radiographic, or dye-penetrant
- Hydrostatic Pressure Test: Ensures no leakage under operational stress
- Chemical Composition Verification: Spectro analysis or PMI testing
- Intergranular Corrosion Test (IGC): Confirms stabilization efficiency
Certified suppliers such as Aerospace Alloys provide full traceability through Mill Test Certificates (MTC EN 10204 / 3.1B).
Global Market & Supply Chain Overview
Demand for ss 347h flanges is increasing due to global expansion of energy, petrochemical, and infrastructure projects.
Market Insights:
- Asia-Pacific leads production and consumption, with India and China as key exporters.
- Europe & the Middle East demand flanges for high-pressure refinery systems.
- North America shows steady demand from power and aerospace sectors.
Procurement Tips
- Prefer manufacturers offering custom dimensions, quick lead times, and third-party testing.
- Ensure international shipping compliance and protective packaging standards.
- Build long-term supplier relationships to secure consistent quality and price stability.
Maintenance & Handling Guidelines
Even high-grade ss 347h flanges require proper maintenance to ensure optimal performance and safety.
Best Practices:
- Store flanges in dry, covered areas away from corrosive atmospheres.
- Inspect sealing faces before installation to avoid leaks.
- Use compatible gaskets and fasteners per ASME B16.5.
- Apply anti-seize compounds during assembly to prevent galling.
- Perform regular torque checks in high-vibration systems.
- Clean with non-chloride solutions to maintain corrosion resistance.
Adhering to these maintenance guidelines extends service life and ensures system reliability.
How to Choose the Right Supplier
When sourcing ss 347h flanges, consider the following evaluation checklist:
-
Certifications: ISO 9001, PED, and compliance with ASTM / ASME standards.
-
Material Traceability: From billet stage to final delivery.
-
Testing & Inspection: 100 % NDT and documented test reports.
-
Customization Capability: Non-standard dimensions, coatings, and pressure classes.
-
After-Sales Service: Technical guidance and logistics support.
-
Customer Feedback: Check case studies or client references.
A trusted supplier ensures not only product quality but also efficient delivery and technical reliability.
Conclusion
From power generation to petrochemical processing, ss 347h flanges have proven indispensable for systems exposed to high heat, pressure, and corrosion. Their niobium-stabilized structure, high mechanical strength, and long service life make them a preferred choice in demanding industrial environments.
By understanding the composition, manufacturing process, standards, and maintenance of these flanges, engineers and procurement professionals can make smarter, cost-effective choices that enhance operational safety and efficiency. When sourced from certified manufacturers like Aerospace Alloy, ss 347h flanges deliver consistent performance and enduring reliability.