What the Cu-DHP Designation Means
Cu-DHP is the designation given in EN 1412 to phosphorus-deoxidised high-conductivity copper, a wrought grade identified as CW024A in the European numbering system and as UNS C12200 in the American system. The name states the two defining characteristics: the copper content stays at a high level, and the residual phosphorus is deliberately held in a narrow band so that the melt is fully deoxidised.
That deoxidation is the practical reason the grade exists. Oxygen dissolved in copper reacts with hydrogen at high temperature and causes embrittlement, an effect that shows up as cracking in the heat-affected zone of a weld or in a brazed joint. By combining the oxygen with phosphorus before casting, Cu-DHP avoids the problem and can be joined by brazing, soldering and welding with predictable results.
Composition and Conductivity
| Element | Cu-DHP |
|---|---|
| Copper | 99.90 % minimum, including silver |
| Phosphorus | 0.015 to 0.040 % |
| Other elements, total | limited by the designation |
| Electrical conductivity | about 85 % IACS minimum |
| UNS equivalent | C12200 |
Conductivity is the point of comparison with other pure copper grades. High-conductivity tough pitch copper reaches about 100 to 101 % IACS, while the phosphorus in Cu-DHP brings the figure down to roughly 85 % IACS. That reduction is the deliberate price paid for weldability, and it is why Cu-DHP is chosen for fabricated assemblies and Cu-ETP or Cu-OF for the highest-conductivity electrical components.
Tempers, Forms and Mechanical Values
The grade is supplied as sheet, strip, plate, tube, rod, bar and wire, each under its own product standard: EN 1172 for sheet and strip for building purposes, EN 12449 for seamless round tubes for general purposes, EN 1057 for water and gas tube, EN 13601 for rod, bar and wire for general electrical purposes, and ASTM B152/B152M for sheet, strip, plate and rolled bar.
Tempers follow the designation system of EN 1173. Soft annealed conditions such as the R220 class give maximum elongation for bending and deep drawing, while the harder tempers, up to the R360 class, raise tensile strength and reduce elongation for load-bearing or self-supporting parts. The pattern is consistent across the range: as the temper hardens, strength rises and ductility falls, and the temper must be stated on the order because the same nominal grade behaves very differently in a forming press.
Applications and Fabrication
Plumbing and heating tube is the largest single use. Cu-DHP tube to EN 1057 is installed in domestic water and heating systems, bent, brazed and connected with capillary fittings, and it resists corrosion in potable water while remaining hygienic. Building sheet to EN 1172 is used for roofing, gutters, cladding and rainwater goods, where the patina develops into a stable protective layer.
Heat exchangers, condensers, distillation and brewing equipment use the grade for tube and plate because thermal conductivity stays high even though the electrical figure is reduced. Electrical applications include conductors that must be welded or brazed into assemblies, where the deoxidised grade avoids the cracking risk that would otherwise require a different joining process.
Quality Control and Certification
Releases are normally based on certified chemical analysis of each heat, dimensional inspection, and mechanical testing of the finished product. Where conductivity is a requirement it is measured on the finished item rather than inferred from the analysis, because processing history influences the final value. Surface condition, straightness and, for tube, pressure integrity and cleanliness are additional inspection points matched to the duty.
Inspection records follow EN 10204 3.1 so that the delivered product can be traced to the heat number and its test results. For drinking water systems, additional national approvals and material listings may apply, and the supplier should be able to confirm the grade and standard under which the material was produced.
Frequently Asked Questions
Q: What does Cu-DHP stand for?
A: Phosphorus-deoxidised high-conductivity copper. The designation combines the copper content requirement with the narrow phosphorus range that removes dissolved oxygen from the melt.
Q: Is Cu-DHP the same as C12200?
A: Yes. CW024A is the European number and UNS C12200 the American designation for essentially the same phosphorised copper grade, and they are normally treated as equivalent in purchase enquiries.
Q: Why is Cu-DHP conductivity lower than tough pitch copper?
A: The residual phosphorus that deoxidises the melt also reduces conductivity to roughly 85 % IACS. The trade-off buys reliable welding and brazing, which matters more than a few percent of conductivity in fabricated assemblies.
Q: Which product forms are available?
A: Sheet, strip, plate, seamless tube, rod, bar and wire. Each form is covered by a dedicated product standard such as EN 1172 for building sheet or EN 1057 for water and gas tube.
Q: Can Cu-DHP be used for drinking water installations?
A: Yes. Tube to EN 1057 is widely used in potable water and heating systems, subject to the water chemistry limits applicable to the installation and to local approval requirements.
