What ASTM B188 ETP Copper Tube Is
ASTM B188 covers seamless copper bus pipe and tube, and C11000 electrolytic tough pitch copper is the grade most often ordered against it. The alloy is refined electrolytically and then melted and cast in air, which leaves a small but controlled amount of oxygen in the metal as cuprous oxide. That feature keeps the material economical while preserving a minimum copper content of 99.9%, excellent electrical conductivity and the formability that makes copper the reference conductor material for switchyards, bus systems and industrial electrical equipment.
C11000 Chemical, Physical and Electrical Data
| Property | Value |
|---|---|
| Copper content | 99.9% minimum |
| Type | electrolytic tough pitch, oxygen present as cuprous oxide |
| Density | 8.94 g/cm3 |
| Melting point | 1083 deg C |
| Modulus of elasticity | 110 - 130 GPa |
| Thermal conductivity | 401 W/m-K |
| Thermal expansion | 16.5 micrometre/m-deg C |
| Specific heat capacity | 0.385 J/g-K |
| Electrical conductivity | 101% IACS |
| Electrical resistivity | 1.724 x 10-8 ohm-m |
Mechanical Properties by Temper
| Property | Annealed | Half hard |
|---|---|---|
| Tensile strength | 210 MPa | 250 MPa |
| Yield strength | 69 MPa | 186 MPa |
| Elongation | 45% | 12% |
| Hardness, Brinell | 50 HB | 80 HB |
The temper choice follows the duty. Annealed tube bends, flares and is brazed easily and is used for plumbing, cooling and instrument lines. Half hard tube carries higher stiffness and is selected where a bus run must resist deflection, or where fittings are formed and rolled threads are required.
Tough Pitch Behaviour: Oxygen, Hydrogen and Joining
Because C11000 is not deoxidised, the residual cuprous oxide phase has to be kept in mind during fabrication. Heating in a strongly reducing or hydrogen-bearing atmosphere can cause that oxide to react and produce steam at grain boundaries, which embrittles the metal. Where such a furnace atmosphere is unavoidable, an oxygen-free grade such as C10100 or a deoxidised grade such as C12200 should be used instead. In ordinary fabrication, C11000 tube joins easily: soft soldering, brazing with silver filler and gas tungsten arc welding with a copper deoxidised filler are all routine, and the material machines and cold forms without difficulty.
Available Forms, Sizes and Related Standards
| Form | Standard | Available size range |
|---|---|---|
| Pipe and tube | ASTM B188, ASTM B42 | diameter 6 mm - 500 mm, length up to 6 m |
| Sheet and plate | ASTM B152 | thickness 0.5 mm - 50 mm, width up to 1500 mm, length up to 3000 mm |
| Bars and rods | ASTM B187 | diameter 3 mm - 200 mm |
| Angles, channels and beams | ASTM B152 | custom sections for electrical supports |
| Fittings | ASTM B16, ASTM B61 | standard and custom sizes for connectors |
| Foils and bus strip | ASTM B152, ASTM B370 | rolled strip and bus bar in temper to order |
Applications
Bus bars, bus tube and flexible conductors in substations, switchyards and large industrial transformers.
Cooling and plumbing lines, HVAC distribution and industrial process piping where high thermal conductivity is essential.
Heat exchanger and condenser components, electrical contacts and switchgear hardware.
Roofing, cladding, gutters and architectural flashings, where corrosion resistance and long service life matter.
Electrical frames, structural supports and earthing conductors in industrial installations.
Fasteners, terminals, connectors and general electrical hardware.
Ordering and Quality Control
Orders normally state the ASTM designation and year of issue, the UNS number, the temper, dimensions and form, the length and quantity, and any special packaging. Testing for tube and pipe includes tension testing, eddy-current examination, and flattening, expansion or bend tests as applicable to the product form. Certificates and mill test reports are supplied with each lot, and each shipping unit is marked with the order number, grade, temper, dimensions and weight.
Frequently Asked Questions
Q: What does electrolytic tough pitch mean?
The copper is refined electrolytically and then cast in air, which leaves a small controlled amount of oxygen as cuprous oxide. That is what distinguishes tough pitch copper from oxygen-free grades.
Q: How conductive is C11000 copper?
Approximately 101% IACS in the annealed condition, with a resistivity of about 1.724 x 10-8 ohm-m and a thermal conductivity of 401 W/m-K.
Q: Which standard covers C11000 bus tube?
ASTM B188 covers seamless copper bus pipe and tube. Round pressure tube for general service follows ASTM B42, while sheet, plate, bar and fittings follow ASTM B152, B187, B16 and B61.
Q: Can C11000 be used in a hydrogen atmosphere?
It should not be annealed in a strongly reducing or hydrogen-bearing atmosphere, because the oxide phase can cause embrittlement. Use an oxygen-free or deoxidised grade for such duty.
Q: Why choose half hard rather than annealed tube?
Half hard tube gives higher yield strength and stiffness, which suits long bus runs and threaded fittings, while annealed tube is chosen for bending, flaring and general plumbing work.
Q: Does tough pitch copper resist corrosion outdoors?
Yes. A stable patina forms in most atmospheres and protects the metal, which is why C11000 is widely used for roofing, cladding and external electrical equipment.
