UNS C70600 (CuNi 90/10) Forged Tubesheets, Rolled Rings and Bars to ASTM B171
90/10 copper-nickel open-die forgings for condensers, heat exchangers and seawater systems, made in Jiangyin, China.
UNS C70600 is a 90/10 copper-nickel alloy, nominally 88.6% copper, 10% nickel and 1.4% iron, specified in ASTM B171/B171M for condenser plate and tubesheets. It resists seawater corrosion and biofouling at flow velocities up to about 3.5 m/s and is hardened only by cold work. Jiangyin Jiangnan Metal open-die forges C70600 tubesheets, discs, flanges, rolled rings and hollow bars to 3,000 mm diameter.
What UNS C70600 is and where it is used
C70600 is a single-phase, solid-solution copper-nickel alloy. The 10% nickel addition raises strength and corrosion resistance over pure copper, and 1.0 to 1.8% iron stabilises the protective surface film that gives the alloy its resistance to flowing seawater.
Copper is the balance element and no carbon is added, so C70600 is not an alloy steel. The UNS C7xxxx series is reserved for copper-nickel alloys. The alloy is also called cupronickel 90/10, CuNi 90-10, CuNi10Fe and CuNi10Fe1Mn.
Typical service is seawater and brackish water over a design life measured in decades: shell-and-tube condensers, desalination and distiller plant, offshore firewater and ballast systems, ship hulls and sheathing, and splash-zone cladding on platform legs.
Typical components forged in C70600
- Heat exchanger and condenser tubesheets, stationary, floating, front and rear head, solid or weld-overlay clad
- Baffles, support plates and tube plates for shell-and-tube exchangers
- Forged discs, blanks, flanges and blocks
- Seamless rolled rings, sleeves, bushes and bushings
- Hollow bars, casings, shells, cylinders, hubs and housings
- Round bars, shafts and propeller sleeves
- Valve bodies, pump casings, ferrules and pipe fittings for seawater service
Chemical composition of C70600 (ASTM B171)
| Basis | Cu (1) | Ni (2) | Fe | Mn | Zn | Pb |
|---|---|---|---|---|---|---|
| Specified min./max. | Remainder | 9.0-11.0 | 1.0-1.8 | 1.0 max | 1.0 max | 0.05 max |
| Nominal | 88.6 | 10.0 | 1.4 | - | - | - |
(1) Copper plus the sum of the named elements shall be 99.5% minimum. (2) The nickel value includes cobalt.
Mechanical properties of C70600
| Property | Metric | Imperial |
|---|---|---|
| Tensile strength, min. | 275 MPa | 40 ksi |
| Yield strength (0.5% extension under load), min. | 105 MPa | 15 ksi |
| Elongation in 50 mm (2 in.), min. | 30% | 30% |
| Hardness, typical | 70-90 HB | 70-90 HB |
Values apply to the annealed condition. Cold-worked tempers reach higher strength at reduced ductility. For heavy forged sections, agree the test-piece location and section thickness on the order.
Physical properties of C70600
| Property | Value |
|---|---|
| Density | 8.94 g/cm3 (0.323 lb/in3) |
| Melting range | 1100-1145 C (2010-2100 F) |
| Modulus of elasticity | 124 GPa (18 x 106 psi) |
| Thermal conductivity | 40-45 W/m.K |
| Coefficient of thermal expansion (20-300 C) | 17.1 x 10-6 /K |
| Specific heat capacity | 377 J/kg.K |
| Electrical conductivity | 9% IACS approx. (resistivity 0.19 micro-ohm.m) |
| Relative magnetic permeability | Typically below 1.1, essentially non-magnetic |
| Max. recommended seawater velocity | 3.0-3.5 m/s |
C70600 equivalent grades and specifications
| System | Designation |
|---|---|
| UNS (USA) | C70600 |
| EN / ISO | CuNi10Fe1Mn, CW352H |
| DIN material number | 2.0872 |
| BS (UK) | CN102 |
| JIS (Japan) | C7060 |
| GB/T (China) | BFe10-1-1 |
| Naval / military | MIL-C-15726; DEF STAN 02-780 (ex NES 780) |
| ASTM, plate, sheet, tubesheets | B171 / B171M |
| ASTM, rod and bar | B151 |
| ASTM, seamless condenser tube | B111 / B111M |
| ASTM, seamless pipe and tube | B466 / B466M |
| ASTM, welded pipe | B467 |
| ASTM, fittings | B466 with MIL-F-16420 or customer standard |
Composition limits differ slightly between these documents. Always name the governing specification, edition and product form on the purchase order.
C70600 vs C71500: which copper-nickel to specify
| Criterion | C70600, CuNi 90/10 | C71500, CuNi 70/30 |
|---|---|---|
| Nickel content | 9.0-11.0% | 29.0-33.0% |
| Iron content | 1.0-1.8% | 0.40-1.0% |
| Tensile strength, min. (annealed) | 275 MPa | 345 MPa |
| Yield strength, min. (annealed) | 105 MPa | 125 MPa |
| Max. seawater velocity | 3.0-3.5 m/s | 4.5 m/s approx. |
| Biofouling resistance | Slightly better | Good |
| Relative material cost | Lower | Higher |
| Typical use | Condenser tubesheets, seawater piping, hull sheathing | High-velocity or high-temperature seawater circuits, feedwater heaters |
C70600 is the default for moderate-velocity seawater duty. C71500 is reserved for circuits where velocity, temperature or mechanical loading exceeds the 90/10 limits.
Seawater performance and service limits
C70600 depends on a cuprous oxide film that takes roughly two to three months to mature in clean, aerated seawater. Once the film has formed, long-term general corrosion rates in flowing seawater are typically below 0.05 mm per year.
Three conditions govern service life:
- Sulphide pollution. Sulphide-bearing or polluted water interferes with film formation and increases attack. Avoid stagnant polluted water in new systems.
- Velocity. Above the design limit the film is stripped and impingement attack follows, usually at tube inlets, bends and downstream of partial obstructions.
- Stagnation and sediment. Deposits create differential-aeration cells. Flush and drain systems that will stand idle.
C70600 is highly resistant to chloride stress-corrosion cracking and more tolerant of ammonia than brasses. Maximum continuous service temperature is generally taken as 300 C.
Forging, heat treatment and welding
Hot and cold working
C70600 is hot worked between about 850 and 950 C and has good hot and cold formability. It cannot be hardened by heat treatment, so forging practice concentrates on grain refinement and soundness rather than on any hardening response. Strength is raised only by cold work.
Annealing
Annealing is normally carried out at 700 to 850 C followed by rapid cooling. Scaling is limited, but a reducing atmosphere containing sulphur must be avoided.
Welding
The alloy is welded by GTAW, GMAW and SMAW using 70/30 copper-nickel filler, AWS A5.7 ERCuNi or AWS A5.6 ECuNi. The higher-nickel filler carries titanium and manganese as deoxidisers and produces sounder weld metal than matching 90/10 filler.
No preheat is required. Keep interpass temperature below about 150 C and make sure joint faces are free of oil, paint, marking crayon and sulphur-bearing residue, all of which cause hot cracking in copper-nickel welds.
Our C70600 forging capability
| Product form | Size range |
|---|---|
| Tubesheets, discs, blanks, flanges | OD 200-3,000 mm; thickness 10-500 mm |
| Seamless rolled rings | OD 200-3,000 mm; height to 800 mm |
| Hollow bars, sleeves, bushings, cylinders | OD 100-1,200 mm; length to 3,000 mm |
| Round bars and shafts | 20-600 mm diameter |
| Blocks, hubs, housings | To 5,000 kg single-piece weight |
| Clad and weld-overlay tubesheets | C70600 overlay on SA-266, SA-516 or SA-105 backing; overlay thickness by specification |
Supply condition is normally hot forged and annealed, rough machined or finish machined to drawing. Drilled and grooved tubesheets can be supplied complete to your tube layout.
Testing and certification
- Chemical analysis by optical emission spectrometry, plus positive material identification (PMI)
- Tensile strength, yield strength and elongation per ASTM B171
- Hardness survey and, on request, magnetic permeability check
- Ultrasonic examination and dye-penetrant examination to the customer standard
- Dimensional report against the approved drawing
- EN 10204 3.1 mill certificate as standard, 3.2 with third-party witness on request
What to send with your enquiry
A quotation usually takes under 24 hours when the enquiry includes:
- Drawing or sketch with dimensions and machining allowance
- Grade and governing specification, for example C70600 to ASTM B171
- Product form, quantity and required delivery condition
- Testing, NDE and certification requirements
- Destination port and required delivery date
Frequently asked questions about UNS C70600
What is UNS C70600?
UNS C70600 is a 90/10 copper-nickel alloy containing nominally 88.6% copper, 10% nickel and 1.4% iron. It is a single-phase solid-solution alloy used for seawater piping, condenser and heat exchanger tubesheets and marine hull components, and is specified for plate and tubesheet service in ASTM B171/B171M.
Is UNS C70600 an alloy steel?
No. C70600 is a copper-base alloy, not a steel. It contains no deliberate carbon addition and copper is the balance element. The UNS C7xxxx series covers copper-nickel alloys, so C70600 is classified as a cupronickel rather than an alloy steel.
What is the chemical composition of C70600 to ASTM B171?
Nickel including cobalt 9.0 to 11.0%, iron 1.0 to 1.8%, manganese 1.0% max, zinc 1.0% max and lead 0.05% max, with copper as the remainder. Nominal composition is Cu 88.6%, Ni 10.0%, Fe 1.4%. Copper plus the named elements must total at least 99.5%.
What is the difference between C70600 and C71500?
C70600 is 90/10 copper-nickel with 9.0 to 11.0% nickel. C71500 is 70/30 copper-nickel with 29.0 to 33.0% nickel. C71500 is stronger, 345 MPa minimum tensile against 275 MPa annealed, and tolerates roughly 4.5 m/s seawater velocity against 3.0 to 3.5 m/s. C70600 costs less and has slightly better biofouling resistance, so it is the usual choice at moderate flow velocity.
Can C70600 be hardened by heat treatment?
No. C70600 is a single-phase solid-solution alloy and cannot be strengthened by quenching or ageing. Strength is raised only by cold work. Heat treatment is limited to annealing, typically at 700 to 850 C followed by rapid cooling, to restore ductility after forging or cold working.
What is the maximum seawater velocity for C70600?
The accepted design limit for 90/10 copper-nickel in clean seawater is 3.0 to 3.5 m/s for tubes and small-bore pipe, rising for large-diameter pipework where flow is well developed. Above that limit the protective film can be removed and impingement attack begins. Where higher velocity is unavoidable, specify 70/30 copper-nickel C71500.
Is C70600 magnetic?
C70600 is essentially non-magnetic. Relative permeability is typically below 1.1 and falls as iron content is reduced, which is why 90/10 copper-nickel suits mine countermeasure vessels and other low-signature structures. Permeability responds to iron level and cold work, so state a maximum permeability on the order if it is a design requirement.
Which filler metal is used to weld C70600?
90/10 copper-nickel is normally welded with 70/30 filler, AWS A5.7 ERCuNi for GTAW and GMAW, or AWS A5.6 ECuNi for SMAW. The higher-nickel filler contains titanium and manganese as deoxidisers and gives sounder weld metal than matching 90/10 filler. Preheat is not required, interpass temperature is normally held below about 150 C, and joints must be free of oil, paint and sulphur-bearing residue.
Which international grades are equivalent to UNS C70600?
EN CuNi10Fe1Mn or CW352H, DIN 2.0872, BS CN102, JIS C7060 and Chinese GB/T BFe10-1-1. Naval equivalents include MIL-C-15726 and DEF STAN 02-780, formerly NES 780. Chemistry limits differ slightly between these specifications, so always name the governing standard on the purchase order.
What sizes of C70600 tubesheets and forgings can you produce?
Jiangyin Jiangnan Metal open-die forges C70600 tubesheets and discs to 3,000 mm outside diameter and 500 mm thick, seamless rolled rings from 200 to 3,000 mm outside diameter, hollow bars and sleeves from 100 to 1,200 mm outside diameter, and round bars from 20 to 600 mm diameter, with single-piece weights to 5,000 kg. Solid C70600 and copper-nickel weld-overlay clad tubesheets on carbon or low-alloy steel backing are both available.
Request a quotation for C70600 forgings
Send your drawing and specification. Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, supplying forged tubesheets, rings and bars worldwide.
Phone +86 189 2135 9659 | Email sales@steelforgepieces.com