COMPREHENSIVE TECHNICAL ANALYSIS AND DATASHEET OF UNS C71500 CUPRO-NICKEL 70/30 FASTENERS
UNS C71500, universally recognized as Cupro-Nickel 70/30 or Alloy 715, represents the absolute pinnacle of corrosion resistance within the copper alloy family. By significantly increasing the Nickel content to 30% and maintaining precision additions of Iron and Manganese, this alloy achieves structural strength and erosion-corrosion resistance that vastly outperforms its 90/10 counterpart. It is specifically engineered to survive the most punishing, high-velocity seawater environments on the planet.
C71500 is completely immune to chloride stress-corrosion cracking and exhibits phenomenal resistance to impingement attack from turbulent, aerated seawater. Because of its massive 30% Nickel matrix, it maintains its structural integrity at elevated temperatures much better than other copper alloys, making it the uncompromising, premium choice for nuclear submarine pipe flanges, high-pressure desalination evaporators, and deep-water offshore platforms where maintenance is impossible and failure is catastrophic.
■ Product Overview & Specifications
| Material Classification | High-Nickel Copper Alloy (70/30 CuNi) |
|---|---|
| UNS Designation | C71500 |
| Microstructure | Single-Phase Alpha Solid Solution |
| Magnetic State | Completely Non-Magnetic |
| Density | 8.94 g/cm³ (0.323 lb/in³) |
| Size Range | Metric: M6 to M64 | Imperial: 1/4" to 2-1/2" |
| Primary Attribute | Maximum High-Velocity Seawater Erosion Resistance |
■ Proprietary Datasheet Download (GATED)
UNS C71500 Cupro-Nickel 70/30 — Complete Technical Datasheet
Contains detailed high-temperature yield reduction charts, maximum acceptable seawater flow-rate parameters (up to 4.5 m/s), and strict welding compatibility guidelines for Super Duplex flange assemblies.
⬇ DOWNLOAD DATASHEET■ MTC Integration Section
In extreme marine environments, metallurgical purity dictates survival. The 30% Nickel content must be exact, and the Iron/Manganese ratio perfectly balanced to form the necessary protective oxide shield. Ananka guarantees 100% mill traceability for all C71500 heavy marine fasteners.
- EN 10204 Type 3.1: Validates the critical 29.0–33.0% Nickel inclusion, verifies the trace Iron/Manganese levels, and certifies the mechanical yield limits of the finished fastener.
- EN 10204 Type 3.2: Routinely facilitated for nuclear submarine (NAVSEA) programs, major commercial shipbuilding, and critical offshore FPSO components requiring ABS, DNV, or Lloyd's Register certification.
■ Chemical Composition
The defining feature of C71500 is its massive 30% Nickel base, which fundamentally hardens the matrix and elevates its temperature resistance. The Iron (Fe) addition, while smaller than in 90/10, works in tandem with Manganese to build an extraordinarily tough, tightly adhering protective surface film that resists turbulent erosion.
| Copper (Cu) | Nickel (Ni) | Iron (Fe) | Manganese (Mn) | Zinc (Zn) | Lead (Pb) |
|---|---|---|---|---|---|
| Balance (~68.5) | 29.0 – 33.0 | 0.40 – 1.00 | 1.00 Max | 1.00 Max | 0.05 Max |
■ Mechanical Properties
| Mechanical Property | Typical Limits (Half-Hard / Cold Worked) |
|---|---|
| Tensile Strength | 55,000 - 80,000 psi (380 - 550 MPa) |
| Yield Strength | 25,000 - 50,000 psi (170 - 345 MPa) |
| Elongation (in 2 inches) | 30% - 40% |
| Hardness (Rockwell B) | 70 - 85 HRB |
■ Equivalent Grades & Designations
| Standard / System | Designation |
|---|---|
| ASTM Specifications | ASTM B151 (Rod & Bar), ASTM F467 / F468 |
| Common Trade Names | 70/30 CuNi, Alloy 715, Copper-Nickel 30% |
| European Equivalent | EN CW354H / CuNi30Mn1Fe (DIN 2.0882) |
| Military / Marine Std | MIL-C-15726 (US Navy), DEF STAN 02-780 (UK) |
■ Applications & Industries
- Military & Naval Defense: Primary fastening hardware for critical submarine hull penetrations, torpedo tube assemblies, and high-pressure fire-main piping exposed to high-velocity water.
- Industrial Desalination: Fasteners securing heavy brine heater shells, multi-stage flash (MSF) distillation evaporators, and deep-water intake screens.
- Chemical & Petrochemical: Offshore rig structural bolting and heat exchanger hardware exposed simultaneously to severe chloride levels and localized elevated temperatures.
■ Compatible Fastener Assemblies
| Mating Bolts/Studs | Internal Threads (Nuts) | Washers |
|---|---|---|
| C71500 CuNi Heavy Hex Bolts | C71500 Heavy Hex Nuts | C71500 Precision Flat Washers |
■ Torque & Installation Guidelines
Due to its 30% Nickel content, C71500 boasts significantly higher tensile and yield strength than standard 90/10 Cupro-Nickel, allowing for heavier clamping loads in pressure vessel assemblies. However, like all high-nickel alloys, thread galling under severe friction is a major risk. Application of premium, nickel-safe marine anti-seize is mandatory prior to torquing.
| Nominal Diameter | Threads Per Inch (UNC) | Max Target Torque (in-lbs) | Max Target Torque (ft-lbs) |
|---|---|---|---|
| 1/4" | 20 | 75 - 85 | ~ 6.5 |
| 3/8" | 16 | 220 - 240 | ~ 19 |
| 1/2" | 13 | 450 - 500 | ~ 40 |
| 3/4" | 10 | 1500 - 1700 | ~ 135 |
■ Frequently Asked Questions
1. What justifies the higher cost of 70/30 (C71500) over 90/10 (C70600)?
The leap from 10% Nickel to 30% Nickel drastically changes the metal's performance. 70/30 CuNi can withstand significantly higher seawater flow velocities (up to 4.5 m/s vs. 90/10's limit of ~2.5 m/s) without the protective oxide layer tearing away. It is also inherently stronger, handles higher localized heat, and offers better resistance to polluted harbor waters containing sulfides. It is essentially the "extreme-duty" upgrade.
2. Does 70/30 Cupro-Nickel resist polluted or stagnant water?
Yes. While standard brasses suffer from "dezincification" and stainless steels suffer from severe crevice corrosion in stagnant or sulfide-polluted harbor waters, Cupro-Nickel 70/30 remains highly stable. Its protective oxide film forms rapidly and heals itself, effectively blocking the corrosive attack of hydrogen sulfide found in polluted bays.
3. Are C71500 fasteners prone to Chloride Stress-Corrosion Cracking (SCC)?
No. This is one of the primary reasons C71500 is specified over 300-series stainless steel in offshore environments. Standard stainless steels (like 304 and 316) are highly susceptible to sudden, catastrophic failure via stress-corrosion cracking when exposed to warm, chloride-rich environments under tension. Cupro-Nickel alloys are metallurgically immune to this specific failure mode.