What Is C12200 DHP Copper Tube
ASTM B111 C12200 is phosphorus deoxidised copper, also written DHP, with a copper content of 99.90% minimum. The grade is made by deoxidising the melt with phosphorus, which leaves a controlled residual phosphorus level in the metal. That residual phosphorus is what makes the alloy resistant to hydrogen embrittlement during brazing and welding in reducing atmospheres, and it is also the reason the electrical conductivity of C12200 is lower than that of oxygen free copper such as C10200.
Hard drawn C12200 tube combines two useful properties for cooling circuits: the strength and dimensional stability of a cold worked temper, and the corrosion resistance of commercial pure copper in water, refrigerant and process fluid service. Cooler, condenser and refrigerant tubes are therefore commonly specified as hard drawn tube where the bundle is not U-bent after production and where straightness and tube to tubesheet fit are critical.
Composition and Comparison with C10200
| Property | C12200 (DHP) | C10200 (OF) |
|---|---|---|
| Copper content | 99.90% min | 99.95% min |
| Deoxidation | Phosphorus deoxidised | Oxygen free, no phosphorus |
| Residual phosphorus | Typically 0.015 - 0.040% | Not deliberately added |
| Hydrogen embrittlement resistance | High | High |
| Electrical conductivity | Lower, reduced by the phosphorus addition | Very high |
| Typical use | Plumbing, cooling and refrigeration tube | Busbar and conductor tubing |
The choice between the two grades follows the duty. Where the tube carries refrigerant, chilled water or potable water and electrical conductivity is irrelevant, C12200 delivers the same fabrication behaviour at lower cost. Where the tube doubles as an electrical conductor, as in busbar tubing and switchgear cooling, the higher conductivity of C10200 is worth the premium. Both grades are readily obtainable in seamless form and both can be supplied as straight tube or coils.
Hard Drawn Temper for Cooling Systems
The hard drawn condition is produced by cold drawing after the final anneal, which raises the yield strength of the tube and improves straightness. In a cooling system this matters in several ways. Hard drawn tube resists deformation when it is pushed through baffle plates and support sheets, it holds a uniform wall thickness around the circumference so that heat transfer stays predictable, and it allows tighter tubesheet hole clearances for reliable roller expansion.
For refrigerant duty, C12200 tube is used as evaporator coil, condenser tubing and liquid and suction line material. In new energy vehicle thermal management systems, tubes are specified to withstand working pressures above 4.2 MPa while also meeting the vibration fatigue requirements of refrigerant circuits, which is where the combination of purity, ductility and fatigue performance of deoxidised copper is important.
Fabrication and Joining Behaviour
| Joining technique | Suitability |
|---|---|
| Soldering | Excellent |
| Brazing | Excellent |
| Gas shielded arc welding | Excellent |
| Oxyacetylene welding | Good |
| Butt welding | Good |
| Coated metal arc welding | Not recommended |
| Spot and seam welding | Not recommended |
Capacity for cold working and for hot forming is rated excellent for this alloy, which is why coils can be bent and headers formed without intermediate annealing. Forgeability is moderate and machinability is low, so cutting, grooving and facing operations are normally done with dedicated copper tooling and sharp, high rake tooling geometry. Where the tube is to be welded, the phosphorus content actually helps by protecting the weld pool from oxygen pickup.
Applications in Cooling and Building Services
Refrigeration and air conditioning: refrigerant tubes, evaporator coils and condenser tubing
Building piping: water supply, gas transmission and capillary radiant heating systems
Drinking water service, where the tube complies with NSF/ANSI 61 requirements
Electronics and electrical: connectors, terminals and heat sinks
Chemical and marine engineering: sulphuric acid coolers and shipboard desalination plant
General engineering: closed circuit cooling loops, chillers and heat recovery circuits
In heating and cooling circuits a hydrophilic surface treatment can be applied to improve heat transfer efficiency, and the inherent corrosion and oxidation resistance of the alloy is what extends equipment life in chemically aggressive service. Because the tube is seamless, there is no weld seam to act as a leak path in a pressurised cooling loop.
Tube is produced from continuously cast or extruded stock, cold drawn to size in multiple passes, then annealed and pickled before the final drawing pass that sets the hard drawn temper. Dimensional control covers wall thickness from 0.2 mm to 120 mm and outside diameter from 2 mm to 910 mm for round tube, with square and rectangular section also available. Straight lengths are typically supplied in 3 m, 5.8 m, 6 m, 11.8 m and 12 m, and hardness is offered across the range from soft through quarter hard and half hard to full hard.
Testing includes spectrometer verification of chemistry, eddy current inspection of the full tube length, dimensional gauging and pressure testing where specified. Surface finish can be supplied as mill, polished, bright, oiled, hairline or brushed, and packaging uses standard export seaworthy bundles suitable for container transport.
FAQ About C12200 Hard Drawn Copper Tube
Q: What does DHP stand for?
DHP means phosphorus deoxidised high conductivity copper. The melt is deoxidised with phosphorus, which leaves a controlled residual level of phosphorus and makes the copper resistant to hydrogen embrittlement during brazing and welding.
Q: Is C12200 suitable for refrigeration circuits?
Yes. C12200 is a standard choice for refrigerant tubes, evaporator coils and condenser tubing. Tubes are specified to withstand working pressures above 4.2 MPa and to meet the vibration fatigue requirements of refrigerant tubing in thermal management systems.
Q: What is the difference between C12200 and C10200?
C12200 contains 99.90% minimum copper with residual phosphorus from deoxidation, giving lower electrical conductivity but excellent performance in water and refrigerant duty. C10200 contains 99.95% minimum copper with no deliberate phosphorus addition and delivers much higher conductivity for conductor tubing.
Q: Can C12200 be used for drinking water?
Yes, C12200 is widely used for water supply, gas transmission and radiant heating pipework and complies with the NSF/ANSI 61 drinking water system requirements when supplied to the applicable specification.
Q: How is the tube joined?
Soldering and brazing are rated excellent, gas shielded arc and butt welding are rated good, and oxyacetylene welding is rated good. Coated metal arc welding and resistance spot or seam welding are not recommended for this alloy.
Q: What sizes and tempers are available?
Round tube covers wall thickness from 0.2 mm to 120 mm with outside diameter from 2 mm to 910 mm, and straight lengths are normally 3 m, 5.8 m, 6 m, 11.8 m or 12 m. Tempers range from soft to full hard, including quarter hard, three eighths hard and half hard.
