What is Copper Nickel CuNi Alloy?
Copper Nickel CuNi alloys are alloys of copper and nickel where the zinc content is no more than 1%. Nickel has the largest individual content after copper when other elements are present. GNEE supplies Copper Nickel alloys in multiple forms including plate, sheet, seamless tube, welded tube, seamless pipe, welded pipe, round bar, flanges, and butt-weld fittings.
Key characteristics of Copper Nickel alloys include:
Excellent resistance to seawater, brine water, organic compounds, salts, and diluted non-oxidizing acids
Good hot strength with only small nickel additions
Improved mechanical properties at room and elevated temperatures with iron additions
Superior resistance to erosion corrosion in flowing seawater
These alloys are widely used in desalination plants and seawater piping systems.
CuNi 90/10 and CuNi 70/30 Product Forms
| Product Form | CuNi 90/10 (C70600 / C70620 / C7060X) | CuNi 70/30 (C71500 / C71520 / C71640) |
|---|---|---|
| Plate / Sheet | Yes | Yes |
| Seamless Tube | Yes | Yes |
| Welded Tube | Yes | Yes |
| Seamless Pipe | Yes | Yes |
| Welded Pipe | Yes | Yes |
| Round Bar | Yes | Yes |
| Flanges | Yes | Yes |
| BW Fittings | Yes | Yes |
Specifications and Properties of C70600 Seamless Tube
| Trade Name | UNS | Industry Specifications | Chemical Composition | Tensile (KSI) min | Yield (KSI) min | Elongation % |
|---|---|---|---|---|---|---|
| CuNi 90/10 | C70600 / C70620 | ASME SB111, SB171, SB359, SB395, SB466, SB467, SB543 / ASTM B111, B122, B151, B171, B359, B395, B432, B466, B467, B543, B608 / DIN 2.0872 / MIL C-15726, T-15005, T-16420, T-22214 / SAE J461, J463 | Cu 88.6% min / Pb 0.05% max / Fe 1.8% max / Zn 1% max / Ni 9-11% / Mn 1.0% max | 38 | 15 | 30 |
| CuNi 90/10 | C7060X | EEMUA 144 90/10, 145 90/10, 14 90/1 | Cu remainder / Pb 0.01% max / Fe 1.5-2.0% / Zn 0.2% max / P 0.2% max / S 0.2% max / Ni 10-11% / Mn 0.5-1.0% | 40 | 15 | 30 |
Specifications and Properties of C71500 Welded Pipe
| Trade Name | UNS | Industry Specifications | Chemical Composition | Tensile (KSI) min | Yield (KSI) min | Elongation % |
|---|---|---|---|---|---|---|
| CuNi 70/30 | C71500 / C71520 | ASME SB111, SB171, SB359, SB395, SB466, SB467, SB543 / ASTM B111, B122, B151, B171, B359, B395, B432, B467, B543, B552, B608, F467, F468 / DIN 2.0882 / MIL C-15726, T-15005, T-16420, T-22214 / SAE J461, J463 | Cu 65.0% min / Pb 0.05% max / Fe 0.4-1.0% / Zn 1% max / Ni 29-33% / Mn 1% max | 52 | 18 | 45 |
| CuNi 70/30 | C71640 | ASTM B111, B543, B552 | Cu remainder / Pb 0.05% max / Fe 1.7-2.3% / Zn 1% max / Ni 29-32% / Mn 1.5-2.5% | 63 | 25 | -- |
Note for welding applications: When the product is for subsequent welding and specified by the purchaser, Zn shall be 0.50% max, Pb 0.02% max, P 0.02% max, Sulfur 0.02% max, and Carbon 0.05% max.
Corrosion Resistance of CuNi 90/10 Condenser Tube
| Alloy | Corrosion Resistance Characteristics |
|---|---|
| CuNi 90/10 (C70600 & C7060X) | Copper nickel iron alloy with small manganese content. Provides excellent resistance to sea and brackish water. Forms a stable protective film in seawater. |
| CuNi 70/30 (C71500) | Best corrosion resistance of all commercial copper alloys in watery environments. Resistant to acid solutions. Highly resistant to stress corrosion cracking and impingement corrosion. Provides greater strength at higher pressures. |
Heat Resistance of CuNi 70/30 Heat Exchanger Tube
| Alloy | Maximum Continuous Operating Temperature |
|---|---|
| CuNi 90/10 (CuNi10Fe1Mn) | Up to 300°C (572°F) for pressure vessel construction |
| CuNi 70/30 (CuNi30Mn1Fe) | Up to 350°C (662°F) |
Important: Above these limit temperatures, strength drops markedly, particularly creep strength and creep strain limit.
Heat Treatment of C70600 U-Bend Tube
| Treatment Type | Temperature Range | Purpose |
|---|---|---|
| Recrystallisation Annealing | 620°C to 900°C (1148°F to 1652°F) | Softens cold-worked material. High temperatures = short times (continuous annealing). Low temperatures = long times (static annealing). |
| Stress-Relief Annealing | 280°C to 500°C (536°F to 932°F) | Relieves internal stresses without altering mechanical properties |
| Atmosphere Recommendation | Excluding air or slightly reducing atmosphere | Avoids oxidation and eliminates need for pickling after annealing |
Applications of C71640 Coiled Tubing
| Industry | Specific Applications |
|---|---|
| Desalination | Evaporator tubes, heat exchanger tubes, brine piping, flash chambers |
| Seawater Piping Systems | Cooling water intake lines, firewater systems, ballast lines, sanitary systems |
FAQ
1. What is the difference between C70600 and C71500?
C71500 has 30% nickel and is stronger, while C70600 has 10% nickel and is more affordable. C70600 (90/10) contains 90% copper and 10% nickel with 1.8% max iron. Tensile strength is 38 KSI minimum. C71500 (70/30) contains 70% copper and 30% nickel with 0.4-1.0% iron. Tensile strength is 52 KSI minimum. C71500 provides better corrosion resistance in aggressive seawater and higher pressure capability, but C70600 is easier to fabricate and more economical.
2. What are the equivalents for C70600?
C70600 equivalents include ASTM B466, ASME SB466, DIN 2.0872, and MIL-T-16420K. Other equivalents are ASME SB111, ASTM B111, ASME SB171, ASTM B171, ASME SB359, ASTM B359, ASME SB395, ASTM B395, ASME SB467, ASTM B467, ASME SB543, ASTM B543, MIL C-15726, MIL T-15005, MIL T-22214, SAE J461, and SAE J463. The European equivalent is EN CW352H (CuNi10Fe1Mn). The British equivalent is BS CN102. The German equivalent is DIN 2.0872.
3. What is the maximum operating temperature for C70600?
C70600 can operate continuously up to 300°C (572°F) for pressure vessel applications. Above this temperature, strength drops markedly, particularly creep strength and creep strain limit. For applications above 300°C, C71500 (70/30) is recommended with a maximum operating temperature of 350°C (662°F).
4. How does iron content affect C70600 corrosion resistance?
Iron additions of 1.0-1.8% significantly improve resistance to erosion corrosion in flowing seawater. The iron content promotes formation of a stable, adherent protective film on the tube surface. This film resists impingement attack from turbulent flow, sand, and silt. Without sufficient iron (minimum 1.0%), C70600 would experience accelerated erosion corrosion in high-velocity seawater.
5. What welding restrictions apply to C70620 and C71520?
C70620 and C71520 are specifically intended for products that will be subsequently welded. For welding applications, Zn shall be 0.50% max, Pb 0.02% max, P 0.02% max, Sulfur 0.02% max, and Carbon 0.05% max. These lower impurity limits prevent hot cracking and porosity during welding. Standard C70600 and C71500 without these restrictions may still be weldable, but C70620/C71520 are preferred for critical welded assemblies.
6. Is C70600 suitable for brackish water?
Yes, C70600 provides excellent resistance to both sea and brackish water. Brackish water (mixture of fresh and seawater) is often more corrosive than pure seawater due to variable salinity, dissolved oxygen, and sediment content. C70600's protective film remains stable in brackish conditions, making it the standard choice for estuarine intake lines, cooling systems, and ballast water treatment.
7. What heat treatment is required after cold working C70600?
Recrystallisation annealing at 620-900°C (1148-1652°F) is required after significant cold work. The exact temperature depends on degree of cold work, nickel content, and additional alloying elements. High temperatures (850-900°C) with short times (continuous annealing) or low temperatures (620-700°C) with long times (static annealing) both achieve full softening. Stress-relief annealing (280-500°C) is sufficient for minor cold work.
8. Why use C70600 instead of stainless steel for seawater?
C70600 resists crevice corrosion and biofouling better than stainless steel in seawater. Stainless steel (304/316) suffers from crevice corrosion under gaskets, deposits, and marine growth. C70600 forms a protective film that self-heals and releases copper ions that prevent biofouling. C70600 also has better thermal conductivity than stainless steel for heat exchanger applications.
9. What is the difference between seamless and welded C70600 tube?
Seamless tube is extruded and drawn from solid billet with no weld seam. Welded tube is formed from strip and welded longitudinally. Seamless tube has no weld line, making it preferred for high-pressure, critical, or ASME code applications. Welded tube is more economical and suitable for general seawater piping. Both forms meet ASTM B466/B467 specifications with equivalent corrosion resistance.
10. Is C70600 subject to stress corrosion cracking?
C70600 is highly resistant to stress corrosion cracking, unlike austenitic stainless steel. C70600 has excellent resistance to SCC in chloride (seawater) environments. However, it can be susceptible in ammonia-rich environments or when exposed to sulfide pollution. For severe ammonia or sulfide services, alternative materials should be evaluated.
11. What sizes and forms does GNEE supply for C70600 and C71500?
GNEE supplies C70600 and C71500 in plate, sheet, seamless tube, welded tube, seamless pipe, welded pipe, round bar, flanges, and butt-weld fittings. Tube and pipe sizes range from 6mm to 300mm OD with wall thickness from 0.5mm to 10mm. Flanges are available in all standard pressure classes. Custom sizes and U-bend tubes can be manufactured upon request. Minimum order quantity is 1 ton per size.
Quality Testing for CuNi 90/10 Nickel Pipe
| Test Type | Standard / Method | Acceptance Criteria |
|---|---|---|
| Chemical Analysis | Optical Emission Spectrometry (OES) or ICP | Verify Cu (88.6% min for C70600, 65% min for C71500), Ni (9-11% or 29-33%), Fe (1.8% max or 0.4-1.0%), Mn (1.0% max) |
| Tensile Testing | ASTM E8 / E8M | C70600: 38 KSI min tensile, 15 KSI min yield, 30% elongation. C71500: 52 KSI min tensile, 18 KSI min yield, 45% elongation |
| Hardness Testing | Rockwell B or Vickers | Verify proper temper (soft annealed O60: 45 HRB max for C70600) |
| Flattening Test | ASTM B466 | Crush tube between flat plates. No cracks or defects visible |
| Expansion Test | ASTM B466 | Expand tube with tapered mandrel to specified percentage. No splitting |
| Eddy Current Testing | ASTM E243 | Detect surface and near-surface flaws. 100% of tubes |
| Hydrostatic Testing | Pressure test | Hold test pressure without leakage. 100% of tubes |
| Reverse Flattening Test | ASTM B466 | Flatten, cut longitudinally, open. No evidence of lamination or defects |
| Grain Size Test | ASTM E112 | Verify average grain size meets specification requirements |
| Intergranular Corrosion Test | ASTM G28 (as applicable) | Verify resistance to grain boundary attack |
| Dimensional Inspection | Micrometer, caliper, go/no-go gauges | Verify OD, ID, wall thickness, length, straightness, end condition |
| Visual Inspection | Naked eye and borescope | Check surface finish, scratches, dents, burrs, and overall appearance |
Packaging for CuNi 70/30 Straight Pipe
| Packaging Component | Material / Specification | Protection Function |
|---|---|---|
| End Protectors | High-density polyethylene (HDPE) thread-on or push-on caps | Seals tube ends against moisture, dirt, insects, and debris during storage and transit |
| Interlayer Paper | Neutral pH kraft paper or VCI (Vapor Corrosion Inhibitor) paper | Prevents direct metal-to-metal contact, absorbs moisture, inhibits corrosion |
| Inner Wrap | 0.10-0.15mm LLDPE (Linear Low-Density Polyethylene) film | Provides moisture barrier and dust protection |
| Bundling Straps | Galvanized steel or PET (polyester) strap, 13-16mm width | Secures tubes into stable bundles. 3-4 straps per 6-meter bundle |
| Edge Protectors | Cardboard or recycled plastic corner angles | Prevents strap cuts and edge damage to tubes |
| Outer Wrap | Woven polypropylene fabric (PP) or geotextile | Abrasion resistance, tear protection, UV protection for outdoor storage |
| Desiccant Packs | Silica gel or clay, 5-50g per package | Absorbs residual moisture inside wrapped bundles |
| Pallet Base | ISPM-15 certified heat-treated plywood or solid wood, 4-way entry | Forklift access, ground clearance (minimum 100mm), export compliance |
| Pallet Banding | 32mm x 0.8mm steel banding (2 vertical, 2 horizontal) | Secures complete pallet assembly for lifting and transport |
| Shipping Label | Weather-resistant adhesive label with barcode | Displays grade (C70600/C71500), size, heat number, quantity, net/gross weight, destination |
| Container Packing | Dunnage bags (air pillows), wooden bracing, or foam blocks | Prevents load shifting inside 20ft, 40ft, or 40ft high cube containers |
Factory Equipment for CuNi Alloy Tube
| Workstation | Equipment Type | Technical Specifications | Production Role |
|---|---|---|---|
| Melting | Medium-Frequency Induction Furnace | 3-ton capacity, 1500 kW power, max temperature 1600°C | Melts copper cathode (99.9% purity) with nickel (99.5% purity) and iron/manganese additions |
| Casting | Horizontal Continuous Casting Machine | 6-strand, billet diameter 90-180mm, casting speed 3-8 m/min | Produces homogeneous tube billets with minimal porosity |
| Extrusion | Hydraulic Extrusion Press | 3150-ton force, container diameter 250mm, max extrusion ratio 50:1 | Pierces solid billet and forms hollow tube shell at 850-1000°C |
| Surface Preparation | Outside/Inside Turning Machine | OD turning accuracy ±1mm, ID boring accuracy ±1mm | Removes oxidation and defects from extruded tube shell |
| Cold Pilgering | 2-High Cold Pilger Mill | Roll diameter 350mm, max rolling speed 120 strokes/min, reduction ratio up to 80% | Reduces OD and wall thickness progressively with high precision |
| Annealing (Intermediate) | Bell-Type Annealing Furnace | Hydrogen or dissociated ammonia atmosphere, max temperature 900°C, capacity 10 tons | Softens material after cold work for further drawing (620-900°C range) |
| Drawing | Chain-Type Draw Bench | 40-ton pull force, max tube length 18m, drawing speed 10-25 m/min | Achieves final OD, ID, and wall thickness tolerances (tenths of mm) |
| Annealing (Final) | Bright Annealing Furnace | Controlled hydrogen atmosphere, dew point -60°C, annealing temperature 650-750°C | Produces clean, oxide-free bright finish (soft annealed temper O60) |
| Straightening | 6-Roll Rotary Straightener | Roll arrangement 2-2-2, max tube OD 100mm, straightening speed 20-60 m/min | Corrects bending to straightness tolerance 0.5mm per meter |
| Cutting | Automatic Tube Saw | Carbide-tipped circular blade, cutting tolerance ±1.0mm, burr-free | Cuts tubes to single random (5-7m) or double random (9-13m) lengths |
| End Finishing | Deburring and Chamfering Machine | Conical brush for ID, abrasive belt for OD, bevel angle 30-35° | Removes burrs and prepares beveled ends for welding (plain or beveled ends) |
| Cleaning | Ultrasonic Cleaning Line | Multi-stage dip tanks with alkaline and acid solutions, hot rinse | Removes drawing lubricants, oils, and surface contaminants |
| Inspection | Eddy Current Testing (ECT) Unit | Frequency range 10 kHz to 2 MHz, detects flaws >0.1mm deep | 100% non-destructive testing of every tube length |
| Pressure Testing | Hydrostatic Tester | Max test pressure 10,000 psi (690 bar), automatic pressure hold | 100% leak testing of every tube length |
| Strapping | Automatic Tube Strapping Line | Pneumatic strap tensioner, 13mm steel or PET strap | Applies 3-4 evenly spaced straps per 6-meter bundle |
| Weighing | Platform Scale | Capacity 3,000 kg, accuracy ±0.5 kg | Verifies bundle weight against packing list |
| Labeling | Barcode Label Printer | Thermal transfer, weather-resistant labels | Generates packing labels with heat number, grade, size, quantity |
All Product Range from GNEE
| Material Category | Key UNS Grades | Cu % | Common Applications | Available Product Forms |
|---|---|---|---|---|
| Pure Copper | C10100 (OFE), C10200 (OF), C11000 (ETP), C12200 (DHP) | 99.9%+ | Electrical busbars, grounding, transformer windings, plumbing pipes, roofing sheets, heat exchanger fins | Tube, pipe, sheet, plate, bar, busbar, wire, rod, strip |
| Brass (Copper-Zinc) | C26000 (Cartridge), C27000 (Yellow), C28000 (Muntz), C33000 (Low Lead), C33200 (High Lead), C37000, C44300 (Admiralty), C44400, C44500, C46400 (Naval), C48500 | 60-85% | Plumbing fittings, ball valves, radiator cores, marine hardware, condenser tubes, ammunition casings, decorative trim, fasteners | Tube, pipe, sheet, plate, rod, hex bar, forging, wire |
| Copper-Nickel (Cupronickel) | C70400, C70600 (90/10), C70620, C7060X, C71000, C71500 (70/30), C71520, C71640, C72200 | 65-90% | Seawater cooling systems, power plant condensers, desalination evaporator tubes, shipbuilding piping, offshore platform firewater systems, heat exchangers, hydraulic lines, fish cages | Seamless tube, welded tube, seamless pipe, welded pipe, U-bend tube, coiled tubing, straight pipe, plate, sheet, round bar, flanges, BW fittings |
| Phosphor Bronze | C51000, C52100, C52400, C54400 | 90-95% | Spring contacts, electrical switches, bellows, corrosion-resistant bearings, pump impellers, welding rod, musical instrument strings | Rod, bar, sheet, strip, wire, tube |
| Aluminum Bronze | C61400, C62300, C63000, C63200, C95400, C95500 | 80-90% | High-strength valve bodies, pump impellers, marine propellers, landing gear components, worm gears, bushings, wear plates, downhole tools | Pipe, bar, forging, casting, sheet, plate, tube |
| Silicon Bronze | C65100, C65500 | 96-98% | Welding rod, pump shafts, valve stems, marine hardware, fasteners, chemical equipment | Rod, bar, wire, sheet, strip |
| Beryllium Copper | C17000, C17200, C17300, C17500 | 96-98% | High-strength non-sparking tools, downhole oil tools, plastic mold inserts, welding electrodes, connectors, springs, diaphragms | Rod, bar, wire, strip, casting, sheet |
| CuNi Cladding / Lined Pipe | C70600 / Carbon Steel, C71500 / Carbon Steel | N/A | Corrosion-resistant lining for seawater piping where full alloy pipe is cost-prohibitive | Clad pipe, lined pipe, bimetallic tube |
