Summary
UNS C70620 is the weldable grade of 90/10 copper-nickel specified in ASTM B171 / ASME SB-171 for plate and sheet used in pressure vessels, condensers and heat exchangers. It contains a minimum of 86.5 % copper including silver, 9.0 to 11.0 % nickel including cobalt, and 1.0 to 1.8 % iron.
C70620 differs from C70600 in its residual-element limits: lead 0.02 % max, zinc 0.50 % max, carbon 0.05 % max, phosphorus 0.02 % max and sulfur 0.02 % max. These limits reduce the risk of weld cracking and porosity, so C70620 is the grade specified when the part will be welded or weld-overlay clad. The mechanical requirements of C70600 and C70620 are the same: 40 ksi [275 MPa] minimum tensile strength, 15 ksi [105 MPa] minimum yield strength and 30 % minimum elongation, for thicknesses up to 5 in [140 mm].
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory in Jiangyin, Jiangsu, China. It manufactures C70620 tube sheets, baffles, support plates, forged discs, flanges, rings, sleeves and hollow bars to ASTM B171 with EN 10204 3.1 certification. Enquiries: sales@steelforgepieces.com, +86 189 2135 9659.
UNS C70620 at a glance
- UNS number
- C70620
- Common name
- 90/10 copper-nickel, welding grade (Cupronickel 10)
- Governing specification
- ASTM B171/B171M; ASME SB-171 (BPVC Section II, Part B)
- Alloy family
- Wrought copper-nickel (Cu-Ni), C7xxxx series
- Nominal composition
- Cu 86.5 % min, Ni 9.0 to 11.0 %, Fe 1.0 to 1.8 %
- Tempers available
- M10, M20, O20, O25 (per ASTM B601)
- Tensile strength, min
- 40 ksi [275 MPa]
- Yield strength, min
- 15 ksi [105 MPa]
- Elongation in 2 in [50 mm], min
- 30 %
- Density
- 8.94 g/cm³ (0.323 lb/in³)
- Nearest equivalents
- EN CuNi10Fe1Mn / CW352H, DIN 2.0872, BS CN102, JIS C7060, GB BFe10-1-1
- Typical products
- Tube sheets, baffles, support plates, forged discs, flanges, rolled rings, sleeves, hollow bars
What is UNS C70620?
UNS C70620 is a 90/10 copper-nickel alloy specified in ASTM B171/B171M, Standard Specification for Copper-Alloy Plate and Sheet for Pressure Vessels, Condensers, and Heat Exchangers. It is the welding grade of C70600.
ASTM B171 covers plate, sheet and circles cut from plate and sheet in fifteen copper alloys, among them C70600, C70620, C71500, C71520 and C72200. The material is supplied as cast cake and manufactured by hot rolling or forging, then finished by the cold working and annealing needed to reach the specified dimensions and properties. Because the standard admits forging as a production route, C70620 is available as heavy tube sheets and discs and not only as thin sheet.
In seawater the alloy forms a protective cuprous-oxide film that stays stable in chloride water. It resists macrofouling by barnacles and mussels, and it is not susceptible to chloride or sulphide stress corrosion cracking. The iron and manganese additions are required to maintain corrosion resistance at working flow velocities.
Note on data published elsewhere. Several online datasheets for C70620 carry a mechanical property table in which the entry “6 in [152 mm]”, a thickness, has been transcribed into a strength column as “152 MPa (6 ksi)”. The ASTM B171 tensile requirements for C70600 and C70620 are identical across both published thickness ranges and are given in Table 3 below. Verify against the current edition of the standard before design.
C70620 compared with C70600
C70600 and C70620 share the same nominal base alloy and the same mechanical requirements. The difference is in the residual elements. Lead, sulfur, phosphorus and carbon segregate to grain boundaries during welding and cause hot cracking and porosity, so C70620 caps them.
| Element | C70620 (welding grade) | C70600 | Reason for the difference |
|---|---|---|---|
| Copper, incl. silver | 86.5 min | Remainder | Stated as a minimum so the balance is verifiable |
| Nickel, incl. cobalt | 9.0 to 11.0 | 9.0 to 11.0 | Identical |
| Iron | 1.0 to 1.8 | 1.0 to 1.8 | Identical |
| Manganese | 1.0 max | 1.0 max | Identical |
| Zinc | 0.50 max | 1.0 max | Halved to limit fume and weld porosity |
| Lead | 0.02 max | 0.05 max | Reduced by 60 %; principal hot-cracking agent |
| Carbon | 0.05 max | Not specified | Added limit |
| Phosphorus | 0.02 max | Not specified | Added limit |
| Sulfur | 0.02 max | Not specified | Added limit |
| Cu plus named elements | 99.5 min | 99.5 min | Identical |
Source: ASTM B171/B171M, Table 1, chemical requirements. C70600 may also be ordered to the welding-application footnote limits, which are the same values that define C70620.
Ordering note. Specify C70620 for any tube sheet, baffle or forging that will be welded, weld-overlay clad, or seal-welded to tubes. C70600 is suitable where the part is mechanically joined only, for example roller-expanded with no seal weld. The cost difference between the two grades is small compared with the cost of repairing a cracked tube sheet weld.
Chemical composition of UNS C70620
| Element | Symbol | Content, % |
|---|---|---|
| Copper (incl. silver) | Cu | 86.5 min |
| Nickel (incl. cobalt) | Ni | 9.0 to 11.0 |
| Iron | Fe | 1.0 to 1.8 |
| Manganese | Mn | 1.0 max |
| Zinc | Zn | 0.50 max |
| Carbon | C | 0.05 max |
| Phosphorus | P | 0.02 max |
| Sulfur | S | 0.02 max |
| Lead | Pb | 0.02 max |
Source: ASTM B171/B171M, Table 1. When all listed elements are analysed, copper plus named elements shall total 99.5 % minimum. The composition limits do not preclude other elements; limits for unnamed elements may be agreed between supplier and purchaser. Chemical analysis per ASTM E478 for Cu, Fe below 1.3 %, Pb, Sn and Zn; E54 for Fe above 1.3 %; E62 for Mn and P.
Mechanical properties (ASTM B171)
ASTM B171 sets the same tensile requirements for C70620 as for C70600, and the same values apply across both published thickness ranges up to 5 in [140 mm].
| Thickness | Tensile strength, min | Yield strength, min (0.5 % ext. under load) |
Yield strength, min (0.2 % offset) |
Elongation in 2 in [50 mm], min |
|---|---|---|---|---|
| 2.5 in [60.0 mm] and under | 40 ksi [275 MPa] | 15 ksi [105 MPa] | 15 ksi [105 MPa] | 30 % |
| Over 2.5 to 5 in [60.0 to 140.0 mm] | 40 ksi [275 MPa] | 15 ksi [105 MPa] | 15 ksi [105 MPa] | 30 % |
Source: ASTM B171/B171M tensile property requirements table. Tension testing per ASTM E8/E8M. Yield strength at 0.5 % extension under load corresponds to 0.01 in [0.254 mm] in a 2 in [50.0 mm] gauge length. ksi = 1,000 psi. The values are specification minima, not typical or design values.
Tempers and code requirements
| Temper | Condition | Typical use |
|---|---|---|
| O25 | Hot rolled and annealed | Required for ASME Boiler and Pressure Vessel Code applications |
| M20 | As hot rolled | Non-code plate and tube sheets |
| M10 | As hot forged, air cooled | Non-code heavy forged tube sheets and discs |
| O20 | Hot forged and annealed | Non-code forgings requiring maximum ductility |
Source: ASTM B171/B171M, temper clause. Product manufactured for ASME BPVC applications shall be certified to the hot rolled and annealed (O25) temper. Product for other applications may be produced in M20, M10, O20 or O25.
Ordering note. The mill test certificate is issued against the temper, so state the temper on the purchase order together with the UNS number and the specification edition. An order that states only “ASTM B171 C70620” leaves the temper to the mill, and an M10 certificate will be rejected at document review for an ASME-stamped vessel.
Physical properties (typical)
The values below are typical published properties for the 90/10 copper-nickel family and are given for design reference. They are not requirements of ASTM B171, which specifies chemistry and tensile properties only.
| Property | Metric | Imperial |
|---|---|---|
| Density at 20 °C | 8.94 g/cm³ | 0.323 lb/in³ |
| Melting range | 1100 to 1145 °C | 2010 to 2095 °F |
| Modulus of elasticity | approx. 135 GPa | approx. 19.5 × 10⁶ psi |
| Thermal conductivity at 20 °C | approx. 40 W/m·K | approx. 23 Btu/ft·h·°F |
| Coefficient of thermal expansion, 20 to 300 °C | approx. 17 × 10⁻⁶ /K | approx. 9.5 × 10⁻⁶ /°F |
| Specific heat capacity | approx. 377 J/kg·K | approx. 0.09 Btu/lb·°F |
| Electrical conductivity | approx. 9 % IACS | approx. 9 % IACS |
| Machinability rating (C36000 = 100) | 20 | 20 |
Density per the ASTM B171 densities table, which lists 0.323 lb/in³ [8.94 g/cm³] for C70600, C70620, C71500, C71520 and C72200. The remaining values are typical published data for the alloy family; confirm against the current standard or a mill certificate for design use.
Fabrication and welding
| Process | Rating |
|---|---|
| Hot formability | Good |
| Cold formability | Excellent |
| Gas-shielded arc welding (GTAW, GMAW) | Excellent; preferred route |
| Coated metal-arc welding | Good |
| Resistance welding (spot, seam, butt) | Good |
| Brazing | Good |
| Soldering | Excellent |
| Oxy-acetylene welding | Not recommended |
| Carbon-arc welding | Not recommended |
Typical fabrication ratings published for C70600 and C70620. The machinability rating of 20 on the free-cutting brass scale (C36000 = 100) calls for slow feeds, sharp tooling and generous coolant when drilling tube holes.
International equivalents and cross-references
| System | Designation | Notes |
|---|---|---|
| UNS (USA) | C70620, C70600 | C70620 is the weldable grade |
| ASME | SB-171 | BPVC Section II, Part B |
| EN (chemical) | CuNi10Fe1Mn | Composition-equivalent family |
| EN (numeric) | CW352H | Wrought copper-nickel |
| DIN / Werkstoff | 2.0872 | Legacy German number |
| BS (UK) | CN102 | Legacy British designation |
| JIS (Japan) | C7060 | JIS H3300 and H3320 family |
| GB (China) | BFe10-1-1 | Chinese national standard |
| Military (USA) | MIL-C-15726, MIL-T-16420 | Naval seawater service |
These are composition-equivalent families rather than drop-in substitutes. C70620 carries the tightened residual limits for welding, so check lead, zinc, carbon, sulfur and phosphorus on the mill certificate before accepting any cross-reference. Other grades covered by ASTM B171: C36500, C44300, C44400, C44500, C46400, C46500, C61300, C61400, C63000, C63200, C70600, C70620, C71500, C71520, C72200.
C70620 components we manufacture
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory in Jiangyin, Jiangsu. C70620 is supplied as finished or semi-finished components rather than as stock plate. Tube-hole drilling, grooving, facing and edge preparation are carried out in-house to the customer drawing.
Tube sheets
Fixed, stationary, front, rear and floating tube sheets, drilled, grooved and faced to TEMA or to the customer drawing.
Baffles and support plates
Segmental, double-segmental and disc-and-doughnut baffles, tube support plates and impingement plates.
Forged discs and flanges
Open-die forged discs, blanks, blind flanges, weld-neck and slip-on flanges, forged blocks.
Rings
Seamless rolled rings, retaining rings and forged ring blanks.
Sleeves, bushes and hollow bars
Sleeves, bushings, hollow bars, barrels, casings, shells, cylinders, hubs and housings.
Clad and overlay tube sheets
C70620 explosion bonded or weld-overlay deposited onto carbon and low-alloy steel backing.
| Item | Capability |
|---|---|
| Tube sheet and disc diameter | Up to approx. 3,000 mm |
| Thickness | Up to approx. 400 mm |
| Single-piece weight | Up to approx. 10 t |
| Tube-hole drilling | CNC deep-hole drilling, grooved to TEMA or customer drawing |
| Cladding | Explosion bonding and weld overlay onto SA-516 Gr.70, SA-266, SA-105 and equivalents |
| Certification | EN 10204 3.1 as standard; 3.2 with third-party witness on request |
| Third-party inspection | TUV, BV, SGS, Lloyd’s Register, ABS and customer inspectors accepted |
| Typical lead time | 4 to 8 weeks, depending on size and quantity |
Capability figures are indicative. Send the drawing or datasheet to sales@steelforgepieces.com for a confirmed envelope, weight and delivery date.
Testing and documentation
- Chemical analysis. Ladle and product analysis; PMI by XRF or OES on the finished component on request.
- Tension testing. Per ASTM E8/E8M, with the specimen conforming to the figures referenced in ASTM B171.
- Ultrasonic examination. To acceptance criteria agreed on the order.
- Dye penetrant examination. On machined sealing faces and weld-overlay surfaces.
- Dimensional report. Hole pitch, ligament, flatness and thickness recorded against the drawing.
- Certification. EN 10204 3.1 mill test certificate as standard, stating UNS number, specification edition, temper, heat number and all test results.
Where UNS C70620 is used
C70620 is specified where seawater or brackish water contacts a welded copper-nickel component. Typical applications:
- Power generation. Main condenser tube sheets, auxiliary cooler tube sheets, baffles and support plates in coastal and once-through cooled stations.
- Desalination. MSF and MED evaporator and brine heater tube sheets, where seawater resistance and thermal conductivity are both required.
- Marine and naval. Shipboard seawater cooling systems, sea chests, ballast and firemain heat exchangers, propeller sleeves.
- Offshore and LNG. Topside seawater coolers, produced-water exchangers, utility condensers.
- Refining and petrochemical. Overhead condensers and coolers on seawater or cooling-tower water duty.
- HVAC and general industry. Large chiller and process condensers using raw or recirculated water.
Where the tube sheet is thick and only the waterbox face requires copper-nickel, a clad tube sheet gives the same corrosion performance at lower cost. A C70620 layer is explosion bonded or weld-overlay deposited on a carbon steel backing. This construction is commonly specified above about 150 mm finished thickness.
Information required for a quotation
Quotations are prepared from the following eight items. Supplying all of them avoids a revision cycle:
- Grade and specification. For example “ASTM B171 UNS C70620”, with the edition year if the project fixes one.
- Temper. O25 for ASME code work; M10, M20 or O20 otherwise.
- Component and dimensions. Outside diameter, thickness, and a drawing or sketch if the part is drilled.
- Tube-hole detail. Hole diameter, pitch, pattern, grooves, tolerance class or TEMA reference.
- Solid or clad. If clad, state the backing material and the required clad thickness.
- Quantity. Per item and total, with any call-off schedule.
- Testing and certification. EN 10204 3.1 or 3.2, NDE requirements, third-party inspection.
- Delivery terms. Incoterms, destination port, required delivery date.
Send the enquiry to sales@steelforgepieces.com or message +86 189 2135 9659 on WhatsApp or WeChat. Drawings in PDF, DWG or STEP are all accepted.
Frequently asked questions about UNS C70620
What is UNS C70620?
UNS C70620 is the weldable grade of 90/10 copper-nickel specified in ASTM B171 / ASME SB-171 for pressure vessel, condenser and heat exchanger plate and sheet. It contains a minimum of 86.5 % copper including silver, 9.0 to 11.0 % nickel including cobalt, and 1.0 to 1.8 % iron. It is used mainly for tube sheets, baffles and support plates that are welded or roller-expanded in service.
What is the difference between C70620 and C70600?
C70620 and C70600 have the same nominal 90/10 copper-nickel base, but C70620 applies tighter limits to the residual elements that cause weld cracking and porosity. In ASTM B171, C70620 restricts lead to 0.02 % max against 0.05 % for C70600, zinc to 0.50 % max against 1.0 %, and adds limits of carbon 0.05 % max, phosphorus 0.02 % max and sulfur 0.02 % max. Copper is stated as 86.5 % minimum rather than remainder. The mechanical property requirements of the two grades are identical. Specify C70620 when the component will be welded or weld-overlay clad.
What are the mechanical properties of C70620 to ASTM B171?
For thicknesses up to 5 in [140 mm], ASTM B171 requires C70600 and C70620 to meet a minimum tensile strength of 40 ksi [275 MPa], a minimum yield strength of 15 ksi [105 MPa] at 0.5 % extension under load and at 0.2 % offset, and a minimum elongation of 30 % in 2 in [50 mm]. The same values apply to the 2.5 in [60 mm] and under range and to the over 2.5 to 5 in [60 to 140 mm] range.
Which temper is required for ASME code work?
Product made for ASME Boiler and Pressure Vessel Code applications must be certified in the hot rolled and annealed temper, O25. Product for non-ASME applications may be supplied in M20 as hot rolled, M10 as hot forged and air cooled, O20 hot forged and annealed, or O25. State the required temper on the purchase order, because the mill test certificate is issued against the temper.
What is the C70620 equivalent in EN, DIN, JIS and GB?
The nearest equivalents to the C70620 and C70600 90-10 copper-nickel family are EN CuNi10Fe1Mn with numeric designation CW352H, DIN material number 2.0872, BS CN102, JIS C7060, ISO CuNi10Fe1Mn and Chinese GB BFe10-1-1. These are composition-equivalent families rather than exact substitutes. C70620 carries the tightened residual limits for welding, so check lead, zinc, carbon, sulfur and phosphorus before cross-substituting.
Is C70620 a steel?
No. UNS C70620 is a copper-nickel alloy in the C7xxxx wrought copper series, with copper as the base metal and no iron matrix. Iron is present only as a 1.0 to 1.8 % alloying addition that supports corrosion resistance. The grade is often filed under alloy steel in supplier catalogues, which is a cataloguing convention rather than a metallurgical classification.
Can C70620 tube sheets be supplied clad or weld-overlay coated?
Yes. Jiangyin Jiangnan Metal Co., Ltd. supplies C70620 as solid forged tube sheets and as clad tube sheets in which a C70620 layer is explosion bonded or weld-overlay deposited onto a carbon steel or low-alloy backing such as SA-516 Gr.70 or SA-266. Clad construction is normally chosen when the tube sheet is thick and only the process-side face needs seawater resistance, because it reduces the quantity of copper-nickel required.
What sizes of C70620 tube sheet can be forged?
Jiangyin Jiangnan Metal Co., Ltd. forges C70620 tube sheets and discs up to approximately 3,000 mm in diameter and 400 mm thick, with forged rings, sleeves and hollow bars in proportionate sizes. Confirm the exact envelope for the drawing before ordering, because maximum diameter depends on thickness and finished weight.
Where is C70620 used?
C70620 is used where seawater or brackish water contacts a welded copper-nickel component: condenser and heat exchanger tube sheets, baffles and support plates in power stations, MSF and MED desalination plants, LNG and offshore topside coolers, shipboard and naval seawater systems, and refinery overhead condensers. The properties that govern the choice are seawater corrosion resistance, low biofouling and resistance to chloride stress corrosion cracking.
How do I buy C70620 tube sheets from Jiangyin Jiangnan Metal?
Email the drawing or datasheet to sales@steelforgepieces.com, or call and message +86 189 2135 9659 on WhatsApp or WeChat. Include grade, temper, dimensions, tube-hole detail, quantity, certification requirements and Incoterms. The factory is at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, about two hours by road from the Port of Shanghai.
Related grades
Standards referenced
- ASTM B171/B171M, Standard Specification for Copper-Alloy Plate and Sheet for Pressure Vessels, Condensers, and Heat Exchangers. Source of the chemical composition, tensile property, temper and density data on this page.
- ASME Boiler and Pressure Vessel Code, Section II, Part B, SB-171. Governs temper certification for code construction.
- ASTM B601, Standard Classification for Temper Designations for Copper and Copper Alloys, Wrought and Cast. Defines M10, M20, O20 and O25.
- ASTM E8/E8M, Standard Test Methods for Tension Testing of Metallic Materials.
- ASTM E478, E54 and E62, chemical analysis methods referenced by ASTM B171.
- EN 10204, Metallic products, types of inspection documents (3.1 and 3.2 certificates).
This page summarises publicly documented requirements for reference only and is not a substitute for the standards themselves. Purchase the current edition from ASTM International or ASME, and confirm all values against the mill test certificate supplied with the material.