Copper Alloy C68700-HR50
Supply condition
UNS C68700 · ASTM B111 · EN CW702R, CuZn20Al2 · GB HAl77-2
HR50 = drawn and stress relieved
Preferred where residual-stress corrosion cracking (ammonia, amines) must be avoided in cold-worked tube.
Values for the HR50 condition
Other C68700 tempers and conditions
C68700 is listed in 7 conditions; see the grade overview at C68700.
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 |
HR50This page 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-HR50?
C68700-HR50 is C68700 supplied in the HR50 condition — preferred where residual-stress corrosion cracking (ammonia, amines) must be avoided in cold-worked tube. C68700-HR50 has a yield strength of 220 MPa (31.9 ksi) and a tensile strength of 440 MPa (63.8 ksi) — weaker than 51% of copper alloy grades. Elongation at break is 45% and the elastic modulus is 103 GPa (14.9 Msi). C68700-HR50 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). O61 is the default condition FabDigit quotes; HR50 is available on request or by drawing note.
Advantages
- Ductile — tolerates forming and impact — 45%, better than 91% of copper alloy grades
- Good corrosion resistance — 75/100, better than 90% of copper alloy grades
- Forms and bends easily — 70/100, better than 80% of copper alloy grades
C68700-HR50 properties
Typical room-temperature values for C68700-HR50; 20 are specific to this condition. Other listed values are C68700 reference data and may not represent this condition. Bars are the position among copper alloy grades.
Physical3
C68700-HR50 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-HR50 has a yield strength of 220 MPa (31.9 ksi) and a tensile strength of 440 MPa (63.8 ksi) — weaker than 51% of copper alloy grades. Elongation at break is 45% and the elastic modulus is 103 GPa (14.9 Msi).
Thermal6
C68700-HR50 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-HR50 conducts electricity at 23 % IACS, better than 56% of copper alloy grades.
Chemical & Environmental3
Corrosion resistance is very good (75/100), better than 90% of copper alloy grades.
Sustainability4
Producing a kilogram of C68700-HR50 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-HR50's machinability is poor (33/100, worse than 53% of copper alloy grades); weldability fair (35/100); formability very good (70/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with C68700-HR50
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.
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.
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 | — |
C68700-HR50 — frequently asked
What is C68700-HR50 used for?
C68700-HR50 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-HR50?
C68700-HR50 has a typical yield strength of 220 MPa (31.9 ksi) and a tensile strength of 440 MPa (63.8 ksi) — weaker than 51% of copper alloy grades. Strength varies by condition: see the 7 listed tempers.
Is C68700-HR50 easy to machine?
Not especially — machinability is rated poor (33/100, worse than 53% 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-HR50 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-HR50?
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-HR50 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-HR50?
C68700-HR50 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.
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. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.