What Is ASTM B68 C12200 Copper Tube
ASTM B68 covers seamless copper tube for use in refrigerators, oil lines, gasoline lines and similar service where the bore must be free from scale, dirt and excessive oxide. The tube is supplied in the annealed temper, bright finished, and is made from C12200, a deoxidized high-phosphorus (DHP) copper with a phosphorus content of 0.015 to 0.040 percent. The phosphorus removes residual oxygen during melting, which gives the material sound weldability and brazeability.
Chemical Composition
| Element | Requirement |
|---|---|
| Copper + Silver | 99.90% minimum |
| Phosphorus | 0.015 - 0.040% |
| Lead | 0.005% maximum |
| Total impurities excluding oxygen | 0.03% maximum |
Available Sizes and Forms
C12200 tube under ASTM B68 is commonly supplied in outer diameters from 4 mm to 100 mm and wall thicknesses from 0.6 mm to 6 mm. It is available as straight lengths and as coils up to about 6 metres, with a plain, bright finish. The thin-wall, clean-bore character of B68 tube suits capillary lines, liquid lines and suction lines in refrigeration circuits, where a single particle of debris can block a small orifice.
Mechanical and Physical Properties
| Property | Value |
|---|---|
| Tensile strength (annealed) | 220 MPa minimum typical |
| Elongation (annealed) | 40% minimum |
| Hardness (annealed) | 40 HV maximum typical |
| Electrical conductivity | Approximately 85% IACS |
| Thermal conductivity | Approximately 340 W/(m·K) |
The annealed temper gives the tube the ductility needed for bending, flaring and expanding during installation. Because the material is phosphorus-deoxidized, it remains weldable and brazeable, which is a decisive advantage over oxygen-bearing ETP copper in joining-intensive assemblies.
Equivalent Standards and Designations
| Standard | Grade |
|---|---|
| ASTM B68 / B75 | C12200 |
| BS 2871 Part 3 | C106 |
| EN 12451 / EN 1057 | Cu-DHP |
| JIS H3300 | C1220 |
Fabrication Characteristics
C12200 tube rates excellent for bending, flaring, soldering and brazing, and its corrosion resistance in water, steam and common industrial fluids is good. These characteristics make it the standard choice for heat exchanger tubing, water supply lines, air-conditioning refrigerant circuits and general engineering tube where joints must be made by brazing or welding rather than mechanical fastening alone.
Frequently Asked Questions
Q: What is the difference between ASTM B68 and ASTM B75?
A: ASTM B68 covers annealed seamless tube for refrigerator, oil and gasoline lines where absolute freedom from scale and dirt is required; ASTM B75 covers seamless copper tube for general engineering applications. Both are commonly produced from C12200.
Q: Is C12200 the same as ETP copper?
A: No. C12200 is deoxidized high-phosphorus copper and contains 0.015 to 0.040 percent phosphorus; ETP copper is C11000 and contains oxygen. C12200 is weldable and brazeable, while C11000 is not recommended for fusion joining in reducing atmospheres.
Q: What does DHP stand for?
A: Deoxidized high phosphorus, referring to the residual phosphorus level left in the metal after deoxidation.
Q: Why is the bore cleanliness of B68 tube important?
A: Refrigeration and oil circuits contain small orifices; scale and debris inside the tube can restrict flow or block expansion devices, so the internal surface is kept bright and clean.
Q: Can B68 C12200 tube be coiled?
A: Yes, small-diameter tube is regularly supplied in coils for long-run refrigerant and instrument lines.
