June 2025 – Shanghai, China — As industries worldwide continue to demand high-integrity, corrosion-resistant piping systems, Copper Nickel (Cu-Ni) flanges, particularly the 90/10 C71500 RF and 70/30 UNS C70600 welding neck types, are emerging as the reliable choice for marine, chemical, and energy applications. Manufactured to ASTM B151 / ASME SB151 standards and often rated at Class 300 (300#) pressure levels, these flanges provide long-term durability and mechanical strength in some of the harshest operating environments on earth.
Chinese manufacturers, particularly in the port cities of Wenzhou and Shanghai, are now producing these copper-nickel flanges with enhanced precision, quality certification, and global export capability, meeting the growing demand from shipbuilders, oil refineries, desalination plants, and offshore energy developers.
Understanding Cu-Ni 90/10 and 70/30 Alloys
Copper-nickel alloys are known for their excellent seawater corrosion resistance, thermal stability, and antifouling properties. The two most widely used grades include:
C70600 / Cu-Ni 90/10 (90% Copper, 10% Nickel)
Offers moderate strength and excellent corrosion resistance. Ideal for cooler water temperatures and standard marine environments.
C71500 / Cu-Ni 70/30 (70% Copper, 30% Nickel)
Higher nickel content improves strength and performance under high flow velocities, high pressure, and elevated temperatures. Preferred in naval, chemical, and offshore applications.
These alloys naturally resist pitting, stress corrosion cracking, and biofouling, making them ideal for saltwater piping systems, heat exchangers, and condenser lines.
RF and Welding Neck Flange Design Features
1. Raised Face (RF) Flanges – C71500
The raised face (RF) design is among the most common flange types, ensuring effective gasket compression and leak resistance. C71500 RF flanges are commonly used for joining pipes and valves in systems where corrosion resistance and high strength are critical.
2. Welding Neck Flanges – C70600
Weld neck flanges are designed with a long tapered hub, ideal for butt-weld connections to the piping system. The gradual transition of thickness helps reduce stress concentration, making it suitable for high-pressure and high-temperature systems.
When manufactured to ASTM B151 / ASME SB151, these flanges conform to the strict mechanical property and chemical composition standards required for industrial reliability.
Applications Across Key Industries
Cu-Ni flanges are deployed in several mission-critical applications due to their unique combination of durability, thermal conductivity, and resistance to biofouling.
● Marine and Shipbuilding
Used in seawater piping, fire suppression systems, ballast lines, and heat exchangers on commercial vessels, naval ships, and submarines. Their anti-biofouling properties reduce maintenance in saltwater environments.
● Offshore Oil and Gas
Essential for topside and subsea processing equipment, where chloride-induced corrosion is a major threat. Cu-Ni flanges ensure operational safety under extreme pressure and salinity.
● Desalination Plants
Highly resistant to brine and scaling, Cu-Ni 70/30 flanges are widely used in reverse osmosis systems, intake pipelines, and brine discharge units.
● Power Generation
In nuclear and thermal plants, Cu-Ni flanges are used in cooling systems, condensers, and turbine lines due to their ability to withstand hot, corrosive fluids.
● Chemical Processing
Where fluid purity and corrosion control are essential, Cu-Ni flanges deliver excellent reliability against acids, alkalis, and industrial solvents.
Compliance with International Standards
To ensure quality and global compatibility, the production of Cu-Ni flanges strictly adheres to internationally recognized specifications:
ASTM B151 / ASME SB151: Standard for seamless copper-nickel pipe and tube products, covering chemical composition, mechanical properties, and dimensional tolerances.
ANSI / ASME B16.5: Standards for flange dimensions, pressure classes, face types, and bolting patterns.
ISO 9001 / PED / DNV / ABS certifications are often available from top suppliers.
Buyers in Europe, the Middle East, and Southeast Asia often request EN 10204 3.1 or 3.2 MTCs, ultrasonic testing, and third-party inspection by SGS, BV, or TUV before shipment.
Production Capabilities in China
China's copper-nickel flange manufacturing has advanced significantly in recent years. Major factories now boast:
Advanced forging and CNC machining lines
Spectrometer analysis for alloy composition accuracy
Hydrostatic and air leak testing
Precision drilling and face machining
Export-ready packaging with palletized and capped flanges
Common size range: 1/2” to 24” (DN15–DN600)
Pressure classes: 150#, 300#, 600#, up to 2500# on request
Connection types: Welding neck, slip-on, socket weld, threaded, blind, lap joint
These manufacturers also provide OEM branding, custom bore machining, and fast turnaround for urgent project requirements.
Export Trends and Global Reach
With rising investment in renewable energy, marine logistics, and coastal infrastructure, demand for copper-nickel flanges is growing rapidly. China's role as a global supplier is secured by:
Cost-effective production with strict quality
Comprehensive alloy options (C70600 / C71500 / customized Cu-Ni blends)
Multilingual sales teams and responsive after-sales service
Reliable delivery to over 80 countries
Key export markets:
UAE, Saudi Arabia, Qatar – desalination, offshore oil
Germany, Netherlands, Italy – shipbuilding and green energy
USA and Canada – refinery upgrades and military applications
Sustainability and Lifecycle Advantages
Copper-nickel alloys offer strong environmental and economic advantages:
Longevity: Resistant to corrosion and scaling, reducing replacement costs.
Recyclability: 100% recyclable, supporting circular economy goals.
Low Maintenance: Naturally resists marine growth and biofouling.
Energy Efficiency: Excellent thermal conductivity in heat transfer systems.
For green infrastructure projects and ESG-compliant industries, Cu-Ni is the material of choice for the future.
Conclusion: Built to Withstand, Designed to Last
The Copper Nickel Cu-Ni 90/10 C71500 RF flange and 70/30 UNS C70600 welding neck flange, manufactured to ASTM B151 / ASME SB151, represent more than just industrial connectors—they embody trust, strength, and engineering excellence. Whether enduring the crushing depths of the ocean or supporting high-temperature fluid systems, these flanges are designed to perform without compromise.
As industries modernize and climate challenges demand more resilient infrastructure, copper-nickel flanges will continue to anchor global systems—quietly, reliably, and powerfully.