1. Up-Casting Method (UPCAST)
In the up-casting process, electrolytic copper is melted and continuously drawn upward through a water-cooled crystalliser to form a solid bar, which is then cold rolled and drawn into tube. Because the cast structure is less worked and can be somewhat looser, the tube has moderate pressure capability and is mainly used for smaller-diameter air-conditioning and refrigeration lines where working pressure is modest.
Advantages: low investment, low production cost, high output, inexpensive product. Limitations: less dense structure, lower pressure rating - not recommended for high-pressure refrigerant circuits.
2. Continuous Casting and Rolling Method
Electrolytic copper is melted and cast directly into a hollow billet, which is then rolled into tube by a planetary (or similar) rolling mill and finished by drawing. This route is highly productive and cost-efficient, and modern high-speed lines deliver good surface quality.
Advantages: low production cost, high efficiency, long coil lengths. Limitations: the structure is typically less dense than extruded tube and pressure capability is limited, so the product is generally restricted to small-diameter tubing and applications without severe pressure demand.
3. Extrusion Method
Copper is melted and cast into an ingot, the ingot is reheated, and the tube shell is forced through a die on a large extrusion press; the extruded tube is then drawn to final size. Extrusion produces a dense, fine-grained, homogeneous structure.
Advantages: good quality, high density, high pressure resistance, large allowable bending deformation, and suitability for frequent hot/cold cycling and wide temperature differences - including large-diameter tube. This is why extruded-and-drawn copper tube is the standard for HVAC systems, including those using high-pressure refrigerants such as R410A. Limitations: lower output and higher production cost than the casting routes.
4. Process Comparison Table
| Method | Structure density | Pressure rating | Cost | Typical use |
| Up-casting | Moderate | Moderate | Lowest | Small refrigeration lines |
| Continuous cast & roll | Moderate | Moderate | Low | Small-diameter general tube |
| Extrusion + drawing | Dense, fine grain | High | Higher | HVAC, high-pressure refrigerant |
5. Specification and Selection Notes
Air-conditioning copper tube is commonly supplied to ASTM B280 (seamless copper tube for air-conditioning and refrigeration field service), with clean, dehydrated, internally scale-free surfaces and specific pressure ratings. Wall thickness must be verified against the refrigerant's working pressure - high-pressure refrigerants such as R410A require thicker walls than R22 at the same diameter. For brazed field connections, the tube must be free of residual drawing lubricant. When ordering, confirm the standard, temper (typically annealed or light-drawn), size range and internal cleanliness requirement with the mill test certificate.
