C11000 Electrolytic Tough Pitch Copper Pipe in Heat Exchanger Service
C11000 electrolytic tough pitch (ETP) copper is the benchmark heat transfer material of the copper family. It contains 99.90 % copper minimum with a nominal oxygen content of 0.040 %, and it is produced by electrolytic refining followed by tough pitch casting, a route that leaves the metal exceptionally free of metallic impurities. Those low impurity levels are the reason the grade holds its very high electrical and thermal conductivity through rolling, drawing and forming operations, and why it is specified for heat exchanger tubing, water-cooled busbars, commutators, ground straps and current-carrying hardware.
In heat exchanger duty the grade is selected for two reasons that rarely appear together in one alloy: heat moves through the wall quickly, and the tube can be bent, drilled, peened, riveted, soldered and brazed into almost any header or tube-sheet design. C11000 also has excellent hot workability, so it can be formed hot where a complex end fitting is required.
Chemical Composition and Grade Identification
| Element | Content | Note |
|---|---|---|
| Copper (Cu) | 99.90 % minimum | Includes silver |
| Oxygen (O) | Nominal 0.040 % | Characteristic of tough pitch copper |
The oxygen content is deliberately retained in the ETP process and is the property that distinguishes C11000 from oxygen-free grades such as C10100 and C10200 and from phosphorus deoxidised C12200. It is also the reason that furnace operations in a hydrogen-bearing reducing atmosphere must be reviewed before they are applied to this grade.
Physical and Thermal Properties
The following values are typical for C11000 ETP copper at room temperature, quoted in both metric and US customary units because original equipment specifications frequently mix the two systems.
| Property | Metric | US customary |
|---|---|---|
| Density | 8.91 g/cm3 at 20 °C | 0.322 lb/in3 at 68 °F |
| Electrical conductivity | 0.591 MS/m at 20 °C | 101 % IACS at 68 °F |
| Electrical resistivity | 1.71 microhm·cm at 20 °C | 10.3 ohm·cmil/ft at 68 °F |
| Thermal conductivity | 391.1 W/(m·K) at 20 °C | 226.0 Btu·ft/(hr·ft2·°F) at 68 °F |
| Coefficient of thermal expansion | 16.9 × 10-6/°C (20 – 100 °C) | 9.4 × 10-6/°F (68 – 212 °F) |
| Coefficient of thermal expansion | 17.3 × 10-6/°C (20 – 200 °C) | 9.6 × 10-6/°F (68 – 392 °F) |
| Coefficient of thermal expansion | 17.6 × 10-6/°C (20 – 300 °C) | 9.8 × 10-6/°F (68 – 572 °F) |
| Melting range, solidus / liquidus | 1065 °C / 1083 °C | 1949 °F / 1981 °F |
| Modulus of elasticity in tension | 117 000 MPa | 17 000 ksi |
| Modulus of rigidity | 44 130 MPa | 6400 ksi |
| Specific gravity | 8.91 | 8.91 |
| Specific heat capacity | 393.5 J/(kg·K) at 293 K | 0.092 Btu/(lb·°F) at 68 °F |
The expansion data are given at three temperature intervals because the coefficient rises with temperature; a heat exchanger sized on the 20 – 100 °C figure alone will under-predict thermal growth where the shell side runs hotter. The modulus of rigidity is the value needed for torsional calculations on tube-sheet and support-plate designs.
Fabrication and Joining Characteristics
| Process or rating | Assessment |
|---|---|
| Soldering | Excellent |
| Brazing | Good |
| Butt weld | Good |
| Gas shielded arc welding | Fair |
| Coated metal arc welding | Not recommended |
| Oxyacetylene welding | Not recommended |
| Seam weld | Not recommended |
| Spot weld | Not recommended |
| Capacity for being cold worked | Excellent |
| Capacity for being hot formed | Excellent |
| Machinability rating | 20 |
| Forgeability rating | 65 |
The ratings point to a clear fabrication strategy: join with solder or braze wherever the design allows, keep fusion welding to butt joints made with care, and avoid the arc and gas processes that are classed as not recommended. Because cold working capacity is excellent, tube can be expanded, swaged and bent to a tight radius, which is what allows a single tube size to be used across several heat exchanger patterns.
Typical Heat Exchanger and Industrial Applications
Heat transfer equipment: heat exchangers, condensers, pans, vats and kettles
Electrical power hardware: busbars, switchgear, stab terminals, conductors, magnet wire, commutation parts and welding fixtures
Chemical and process plant: pressure vessels, chlorine cells, anodes, chemical process equipment, plating racks and hooks
Building services: downspouts, flashing, roofing, gutters, skylight frames and countertops
Automotive and hardware: gaskets, radiators, rivets, nails, cotter pins, nuts, bolts and expansion plates
Frequently Asked Questions
Q: What does electrolytic tough pitch mean in C11000?
It describes the manufacturing route and the residual oxygen. The copper is refined electrolytically to a purity of 99.90 % or better, then cast as tough pitch wire bar with a nominal oxygen content of 0.040 %. That residual oxygen is characteristic of the grade and is why the material is not classed as oxygen free.
Q: Why is C11000 chosen for heat exchanger tubes?
Because its thermal conductivity of about 391 W/(m·K) and electrical conductivity of 101 % IACS are the highest available in a widely produced wrought copper, and its hot and cold forming behaviour is excellent. For seawater or brackish cooling water, copper nickel alloys such as C70600 and C71500 are usually preferred on erosion and corrosion grounds, while C11000 remains the standard for clean water, steam condensate and process fluids.
Q: Which ASTM specifications apply to C11000 pipe and tube?
ASTM B75 covers seamless copper tube, ASTM B111 covers seamless condenser and heat exchanger tube, ASTM B280 covers refrigeration and air-conditioning tube, ASTM B68 covers bright annealed tube and ASTM B88 covers copper water tube. The matching ASME SB documents apply for pressure retaining service.
Q: Can C11000 pipe be welded into a heat exchanger header?
Butt welding is rated good, but gas shielded arc welding is only fair and coated metal arc and oxyacetylene welding are not recommended. Soldering is excellent and brazing is good, so most headers are designed for brazed or soldered joints, with fusion welding reserved for butt connections. Reducing atmosphere furnaces must be avoided because oxygen-bearing copper can be embrittled by hydrogen.
Q: What is the recommended melting and service temperature basis?
The solidus is approximately 1065 °C and the liquidus approximately 1083 °C. Those figures define the melting range only. Mechanical design should be based on the tensile and yield values of the temper actually supplied, because the annealed condition is the softest state and does not soften further in normal heat exchanger duty.
Q: How should C11000 heat exchanger pipe be specified on a purchase order?
State the specification and its revision, the grade C11000, the temper, the outside diameter and wall thickness with tolerances, the length and cut-length mode, the required testing such as eddy-current or pressure test, and the cleanliness requirement where the tube will enter a refrigeration or oxygen-adjacent circuit.
