What C12200 Phosphorus-Deoxidized Copper Is
C12200 is a deoxidized copper that contains a deliberately controlled amount of phosphorus. The grade is known internationally as DHP, short for deoxidized high phosphorus, and appears in the European designation system as Cu-DHP and in the Chinese and Japanese wrought copper systems as TP2 and C1220 respectively. It combines a copper content of 99.90 % minimum with a phosphorus range that is high enough to complete deoxidation in the melt yet low enough to leave usable electrical and thermal conductivity in the finished product.
The distinction between C12200 and the oxygen-free grades is important. Oxygen-free copper removes oxygen by process control alone and contains no deliberate deoxidant. C12200 removes oxygen by reacting it with phosphorus, so the finished material contains a residual of that element in solid solution. That residual is the reason the grade is ductile enough to be welded and brazed without hydrogen embrittlement, and also the reason its conductivity is lower than that of oxygen-free copper.
Phosphorus Content and Its Role
The specified phosphorus range for C12200 is 0.015 % to 0.040 % in the relevant product standards, including ASTM B152/B152M for plate, sheet, strip and rolled bar, ASTM B75/B75M and ASTM B68/B68M for seamless tube, and the European designation Cu-DHP. The upper limit exists because excess phosphorus lowers conductivity and can impair hot workability; the lower limit exists because too little phosphorus leaves dissolved oxygen in the melt.
| Grade | Phosphorus content | Copper, minimum | Conductivity, annealed |
|---|---|---|---|
| C11000, electrolytic tough pitch | No phosphorus addition; oxygen present as cuprous oxide | 99.90 % | about 100 % IACS |
| C12200, DHP | 0.015 - 0.040 % | 99.90 % | about 85 % IACS |
| C10200, oxygen-free | No deliberate addition; low residual | 99.95 % | about 101 % IACS |
The mechanism is straightforward. During melting, phosphorus reacts with dissolved oxygen to form a phosphorus oxide that leaves the melt as slag, so the cast material solidifies free of the cuprous oxide network that causes hydrogen embrittlement in tough pitch copper. What remains is a small amount of phosphorus in solid solution in the copper lattice. Because dissolved phosphorus scatters conduction electrons very effectively for its low concentration, the effect on conductivity is disproportionate: the difference between the deoxidized high phosphorus grade and oxygen-free copper in the table above is produced by a phosphorus content of only a few hundredths of one per cent.
Grades with an intermediate phosphorus content are available where a compromise is wanted. The deoxidized low phosphorus copper C12000 contains less phosphorus than C12200 and therefore retains rather more conductivity while still being fully deoxidized, which makes it suitable for applications such as bus bar and hollow conductors where both weldability and efficiency matter.
Physical and Mechanical Properties
C12200 is a soft, ductile copper with the density and melting behaviour expected of the metal. Its strength is developed by cold reduction in the same way as the other wrought coppers, and the temper nomenclature follows the standard practice for wrought copper products, running from annealed through quarter-hard, half-hard and hard.
| Property | Typical value | Comment |
|---|---|---|
| Density | about 8.94 g per cubic centimetre | Used for mass and pressure calculations |
| Melting range | about 1080 degrees Celsius | Little affected by the residual phosphorus |
| Electrical conductivity, annealed | about 85 % IACS minimum | Lower than oxygen-free copper because of dissolved phosphorus |
| Tensile strength, annealed | about 210 - 260 MPa | Typical for rod and tube in the soft temper |
| Elongation, annealed | 40 % and above | Allows bending, flaring and expanding without cracking |
| Hardness, annealed | about 45 - 65 HV | Rises steadily with cold reduction |
Mechanical property minima for a particular product form and temper are set by the applicable standard, and the values above are typical commercial figures rather than specification limits. The practical point for a designer is the shape of the property curve: in the soft temper the material has high elongation and moderate strength, and cold working trades elongation for strength. For water and gas tube, where joints are made by bending, flaring and brazing, the soft temper is almost always specified.
Applications of C12200 Rod, Bar and Tube
The combination of full deoxidation, adequate conductivity and excellent formability gives C12200 a wide field of use:
Water tube, gas tube and heating pipe, including the type K, type L and type M wall thicknesses used for domestic and commercial plumbing.
Refrigeration and air-conditioning tubing, where the material must be bent, expanded into fins and brazed without cracking.
Automotive and commercial heat exchangers, radiators, oil coolers and brake lines.
Marine and desalination equipment, seawater piping, condenser water boxes and shipboard plumbing.
Electrical conductors, bus bar and switchgear parts in sizes where the conductivity of the deoxidized grade is sufficient.
Roofing, flashing, gutters and architectural components, where the alloy takes a stable patina and can be soldered.
Rod and bar stock for machining, forged fittings, valves and threaded parts.
In marine and desalination work the grade is used in the forms that carry water rather than in the high-conductivity current-carrying parts, because the oxygen-free grades are preferred wherever conductor efficiency governs the design.
Forming, Joining and Corrosion Notes
C12200 is among the easiest of the wrought coppers to fabricate. It is bent, flared, expanded and swaged in the annealed temper; it is machined with conventional tooling, using sharp edges and generous rake angles because copper work-hardens quickly; and it is joined by soft soldering, silver brazing, gas-shielded arc welding and resistance welding. Because the material is already fully deoxidized, it can be heated in a reducing atmosphere, bright annealed and furnace brazed without the intergranular cracking that affects tough pitch copper. This is a genuine processing advantage and it is often the deciding factor in the selection of the grade.
Corrosion behaviour in water service is generally good, with the usual qualifications that apply to all copper alloys. Attack is influenced by water chemistry, by the presence of residual chlorine or high dissolved solids, and by flow velocity. Pitting can occur in certain waters with aggressive characteristics, and it is managed by controlling water treatment, by keeping velocities within the range recommended for the tube diameter, and by avoiding stagnant conditions during commissioning. C12200 contains no zinc, so dezincification, which is a failure mode of the high-zinc brasses, does not apply to it; the corresponding risk in this family is ant-nest type attack by residual carbon films left inside tube after bright annealing, which is controlled by proper cleaning and by specified carbon residue limits.
FAQ
Q: What is the exact phosphorus content of C12200?
The specified range is 0.015 % to 0.040 %. The lower limit ensures that the melt is fully deoxidized and the upper limit protects conductivity and hot workability.
Q: Why does phosphorus reduce conductivity?
Phosphorus dissolves in the copper lattice and the dissolved atoms scatter conduction electrons. Even a few hundredths of one per cent has a measurable effect, which is why the annealed conductivity of C12200 is about 85 % IACS while oxygen-free copper reaches about 101 % IACS.
Q: Is C12200 the same as oxygen-free copper?
No. Both are free of cuprous oxide, but they achieve that by different means: C12200 uses a phosphorus addition that remains in the finished metal, while oxygen-free copper removes oxygen by process control and contains no deliberate deoxidant.
Q: Can C12200 be welded or brazed?
Yes. It is fully deoxidized, so it can be joined and bright annealed in reducing atmospheres without the intergranular cracking that affects tough pitch copper. Soft soldering, silver brazing and gas-shielded arc welding are all used successfully.
Q: Which standards cover this grade?
ASTM B152/B152M covers plate, sheet, strip and rolled bar, ASTM B75/B75M and ASTM B68/B68M cover seamless tube, and the grade is also designated Cu-DHP in the European system and TP2 or C1220 in the Chinese and Japanese wrought copper systems.
Q: What is the difference between DHP and DLP copper?
DHP means deoxidized high phosphorus and refers to C12200 with its 0.015 % to 0.040 % phosphorus range. DLP means deoxidized low phosphorus and refers to grades such as C12000 that contain less phosphorus and therefore keep a higher conductivity while still being fully deoxidised.
