Copper Alloy C68700
UNS C68700 · ASTM B111 · EN CW702R, CuZn20Al2 · GB HAl77-2
C68700 is an arsenic-inhibited aluminum brass (CuZn20Al2As, also CW702R, HAl77-2, ASTM B111) whose alumina passive film makes it the standard condenser and heat exchanger tube alloy for seawater service.
Reference datasheet — C68700 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the O61 condition
C68700 tempers and conditions
C68700 is supplied in 7 conditions, soft to hard. O61 is the default FabDigit quotes; the values on this page are for it.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
As hot extruded | Mill hot-extruded stock, normally an intermediate feed for drawing rather than a service condition. | 170 | 400 | 50 | 85 HB | 23 % IACS |
O61Default Annealed | Default stocked condition for seawater condenser and heat-exchanger tube; maximum ductility for tube rolling/expanding. | 186 | 415 | 55 | 85 HB | 23 % IACS |
Light annealed | Pick when slightly higher strength than soft anneal is wanted while keeping good expandability. | 200 | 425 | 50 | 95 HB | 23 % IACS |
Drawn and stress relieved | Preferred where residual-stress corrosion cracking (ammonia, amines) must be avoided in cold-worked tube. | 220 | 440 | 45 | 105 HB | 23 % IACS |
Light drawn | Choose for straighter, stiffer tube with better handling strength while still expandable into tubesheets. | 240 | 450 | 45 | 110 HB | 22 % IACS |
Drawn, general purpose | General-purpose drawn tube where higher pressure rating matters more than expansion ductility. | 310 | 490 | 30 | 125 HB | 22 % IACS |
Hard drawn | Highest-strength cold-worked condition for straight tube/rod where forming is not required. | 415 | 560 | 12 | 150 HB | 22 % IACS |
What is C68700?
C68700 is an arsenic-inhibited aluminum brass (CuZn20Al2As, also CW702R, HAl77-2, ASTM B111) whose alumina passive film makes it the standard condenser and heat exchanger tube alloy for seawater service. Annealed tube provides 415 MPa tensile, 186 MPa yield and 55 % elongation at 85 HB (52 HRB), with 100 W/m·K thermal conductivity, 23 % IACS and service to 200 °C. It is supplied mainly as seamless tube; machinability is about 30 % of free-cutting brass and arc welding is not recommended because of the oxide film and zinc fume. Where dezincification resistance in plumbing tube is the driver, C68300 is the alternative. C68700 has a density of 8.33 g/cm³ (0.301 lb/in³), lighter than 77% of copper alloy grades. It melts at 971°C (1,780 °F). C68700 has a yield strength of 186 MPa (27 ksi) and a tensile strength of 415 MPa (60.2 ksi) — weaker than 58% of copper alloy grades. Elongation at break is 55% and the elastic modulus is 103 GPa (14.9 Msi).
What is C68700 used for?
- condenser tubes
- heat exchanger tubes
- seawater piping
Advantages
- Ductile — tolerates forming and impact — 55%, better than 98% of copper alloy grades
- Forms and bends easily — 85/100, better than 85% of copper alloy grades
- Good corrosion resistance — 72/100, better than 84% of copper alloy grades
C68700 properties
Typical room-temperature values for C68700-O61; bars are the position among copper alloy grades.
Physical3
C68700 has a density of 8.33 g/cm³ (0.301 lb/in³), lighter than 77% of copper alloy grades. It melts at 971°C (1,780 °F).
Mechanical12
C68700 has a yield strength of 186 MPa (27 ksi) and a tensile strength of 415 MPa (60.2 ksi) — weaker than 58% of copper alloy grades. Elongation at break is 55% and the elastic modulus is 103 GPa (14.9 Msi).
Thermal6
C68700 is rated for continuous service to 200°C (392 °F). It conducts heat at 100 W/m·K (57.8 BTU/hr·ft·°F), better than 54% of copper alloy grades. Thermal expansion is 18 µm/m·K (10 µin/in·°F).
Electrical3
C68700 conducts electricity at 23 % IACS, better than 56% of copper alloy grades.
Chemical & Environmental3
Corrosion resistance is very good (72/100), better than 84% of copper alloy grades.
Sustainability4
Producing a kilogram of C68700 takes about 52 MJ of energy and emits 3.6 kg of CO₂ — less than 87% of copper alloy grades. Typical recycled content is 30%.
Manufacturability7
C68700's machinability is poor (30/100, worse than 67% of copper alloy grades); weldability fair (35/100); formability excellent (85/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the copper alloy family
Yield strength against density for every copper alloy grade FabDigit runs. C68700 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with C68700
Is C68700 easy to machine?
Machinability ~30 % of free-cutting brass: gummy, needs sharp positive-rake tools, high speed and generous coolant; expect long chips.
Can C68700 be welded?
Arc welding is not recommended (Al oxide film, Zn fume); join by soft soldering or brazing with proper flux, or use resistance/seam welding on thin tube.
Can C68700 be formed, bent or molded?
Annealed tube expands, bends and rolls into tubesheets readily; heavily cold-worked tube should be stress relieved (~300 °C) to avoid SCC.
C68700 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| Cu | 76 – 79 | 77.5 |
| Alforms protective alumina film | 1.8 – 2.5 | 2.1 |
| Asdezincification inhibitor | 0.02 – 0.06 | 0.04 |
| Fe | ≤ 0.06 | |
| Pb | ≤ 0.07 | |
| Znremainder, nominally ~20.4 % | balance |
What surface finishes work on C68700?
Not anodizable; clean and passivate, and use controlled FeSO₄ dosing or clean-water commissioning to build the protective film — avoid stagnant, sulfide-bearing water.
Surface treatments FabDigit runs on copper alloy parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Equivalent designations
Standards and trade names that resolve to Copper Alloy C68700 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- ASTM
- B111
- EN / DIN / Werkstoff-Nr.
- CW702RCuZn20Al2
- GB (China)
- HAl77-2
- Similar grades
- CuZn20Al2AsC6870
How much does C68700 cost?
C68700 is a high-cost copper alloy ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
C68700 — frequently asked
What is C68700 used for?
C68700 is typically used for condenser tubes, heat exchanger tubes and seawater piping. In short: standard seawater condenser tube; arsenic-inhibited aluminum brass; 100 W/m·K conductivity.
What is the yield strength of C68700?
C68700 has a typical yield strength of 186 MPa (27 ksi) and a tensile strength of 415 MPa (60.2 ksi) — weaker than 58% of copper alloy grades. Strength varies by condition: see the 7 listed tempers.
Is C68700 easy to machine?
Not especially — machinability is rated poor (30/100, worse than 67% of copper alloy grades). Machinability ~30 % of free-cutting brass: gummy, needs sharp positive-rake tools, high speed and generous coolant; expect long chips.
Can C68700 be welded?
With care — weldability is rated fair (35/100). Arc welding is not recommended (Al oxide film, Zn fume); join by soft soldering or brazing with proper flux, or use resistance/seam welding on thin tube.
What surface finishes work on C68700?
Not anodizable; clean and passivate, and use controlled FeSO₄ dosing or clean-water commissioning to build the protective film — avoid stagnant, sulfide-bearing water.
Can C68700 be formed, bent or molded?
Annealed tube expands, bends and rolls into tubesheets readily; heavily cold-worked tube should be stress relieved (~300 °C) to avoid SCC.
What is the maximum service temperature of C68700?
C68700 is rated for continuous use to about 200°C (392 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between C68700-O61 and C68700-H80?
O61 is the default condition — default stocked condition for seawater condenser and heat-exchanger tube; maximum ductility for tube rolling/expanding. H80: highest-strength cold-worked condition for straight tube/rod where forming is not required. Yield strength is 186 MPa in O61 versus 415 MPa in H80.
How much does C68700 cost?
C68700 is a high-cost copper alloy ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- ASTM B111/B111M — Copper and Copper-Alloy Seamless Condenser Tubes — ASTM (2021)
- ASTM B171/B171M — Copper-Alloy Condenser Tube Plates — ASTM (2018)
- EN 12451 / CW702R CuZn20Al2As — CEN (2012)
- CDA Alloy Datasheet C68700 — Copper Development Association (copper.org) (2024)
- ASM Handbook Vol. 2 — Properties of Nonferrous Alloys — ASM International (1990)
- ASM Handbook Vol. 13B — Corrosion: Materials — ASM International (2005)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.