Copper Grades That Move in International Trade
The copper that a factory actually buys falls into a small number of well-defined specifications. Cathode copper is the refinery product, specified to GB/T 467-2010 for high-purity and standard grades, to ASTM B115, or to EN 1978 for exchange-registered delivery. Wire rod for drawing into conductor is specified to GB/T 3952 in the Chinese system or to ASTM B49 internationally. Plate, sheet and strip are ordered to GB/T 2059 or to ASTM B152/B152M, oxygen-free grades to ASTM B170 and ASTM F68, busbar and conductor bar to ASTM B187/B187M, and tube to ASTM B88, ASTM B280, EN 1057 or GB/T 1527 depending on the service. The grade designations themselves come from GB/T 5231 in China and from the UNS system internationally, and the two vocabularies must be cross-referenced rather than assumed to coincide.
Composition and Conductivity Requirements
| Grade | Composition | Typical conductivity | Typical supply form |
|---|---|---|---|
| T1 | Cu+Ag 99.95 % min | 100 % IACS and above | wire, strip, busbar |
| T2 | Cu+Ag 99.90 % min | 100 % IACS | rod, strip, tube, busbar |
| T3 | Cu+Ag 99.70 % min | below T2 | general fabricated parts |
| TU1 | Cu+Ag 99.97 % min, oxygen 0.002 % max | 101-102 % IACS | vacuum and electronic parts |
| TUP | phosphorus-deoxidised, high purity | about 90 % IACS | welded assemblies, tube |
| C11000 | Cu 99.90 % min, oxygen 0.02-0.04 % | 100-101 % IACS | sheet, strip, bar, busbar |
| C10100 | Cu 99.99 % min, oxygen 0.0005 % max | 101-102 % IACS | high-vacuum and RF components |
The 100 % IACS reference is defined as 58.0 MS/m at 20 C, and certified conductivity values must always be read together with the test temperature and the test method. Wire rod is normally supplied at or slightly above 100 % IACS, with the billet continuously cast and hot rolled from cathode, and coil weights in the range of three to four tonnes for an eight-millimetre diameter coil.
Supply Forms, Dimensions and Packaging
Copper is shipped in forms that suit the first operation the customer performs. Cathode arrives as strapped bundles of two to four tonnes, marked with refinery brand and lot. Wire rod arrives as coils or as continuous lengths on carriers, with the diameter, surface condition, coiling temperature and pickling or shaving route stated. Billet and extrusion billet arrive cut to length for tube and profile production. Strip arrives as coils with thickness, width, edge condition, temper, grain size and coil weight stated, typically from 0.1 mm to 3 mm thick and up to about 1,000 mm wide in mill supply. Bar and busbar arrive as straight lengths or coils, with straightness, edge radius and corner condition specified. Tube arrives as straight lengths or coils in soft, half-hard or hard temper, capped and dry on the inside where refrigeration or medical duty requires it.
Guaranteed Properties and How They Are Verified
Every commercial property is tied to a test method. Chemical composition is determined by GB/T 5121 or ASTM E478, tensile properties by ASTM E8, hardness by ASTM E18, grain size by ASTM E112, resistivity by ASTM B193 and electrical conductivity by the eddy-current method of ASTM E1004. Dimensions are verified against the tolerance tables in the relevant product standard rather than against a drawing note, and surface quality is assessed against the permitted defect schedule of that standard. For conductor applications the customer will also expect the elongation and the surface cleanliness of wire rod to be controlled, because both affect drawing performance and wire breakage rates downstream.
Typical Ordering Mistakes
Four mistakes cause most disputes. Specifying electrolytic tough pitch copper for a component that will be furnace brazed or annealed in a reducing atmosphere, when oxygen-free or phosphorus-deoxidised grade is required to avoid hydrogen embrittlement. Quoting a conductivity requirement without the test temperature and method, which makes the result impossible to compare. Assuming that cathode purity carries through to the finished product, when melting, casting and rolling each introduce their own limits and defects. Finally, ordering strip or tube by alloy name alone without stating the temper, since two coils of the same grade in different tempers behave completely differently in the press or the bender. A complete purchase order therefore names the standard, the grade, the temper, the dimensions with tolerances, the mechanical and electrical requirements, the surface condition, the test certificates and the packaging.
Frequently Asked Questions
Q: What is the difference between T2 and C11000 copper?
A: Both are electrolytic tough pitch copper at 99.90 % minimum copper, but T2 is the GB/T 5231 designation with Chinese composition limits while C11000 is the UNS designation governed by ASTM product standards.
Q: When should oxygen-free copper be ordered instead of T2?
A: Whenever the part will be brazed, welded or annealed in a hydrogen-bearing atmosphere, or when vacuum performance and very high conductivity are required, since oxygen-bearing copper can crack through hydrogen embrittlement.
Q: What conductivity should a copper wire rod certificate show?
A: Rod is normally certified at or slightly above 100 % IACS, which corresponds to 58.0 MS/m at 20 C, with the test method and temperature stated on the certificate.
Q: How is copper strip ordered correctly?
A: By standard and grade, temper code, thickness and width with tolerances, edge condition, grain size where bending is severe, coil weight, surface condition and the required test certificate.
Q: Which documents should accompany an export copper shipment?
A: A certificate of conformity to EN 10204 3.1 linking heat number to chemical and mechanical results, conductivity test data, dimensional inspection records and packing list marking that matches the coil or bundle identification.
