Copper tubes: metal veins that span thousands of years

Copper pipes, as one of the metal pipes with the longest history of human use, still occupy an irreplaceable position in modern industry and life with their excellent electrical conductivity, thermal conductivity and corrosion resistance. From water pipes on ancient bronzes to hydraulic pipes on spacecraft, from refrigerant delivery in central air conditioners to capillary tubes in precision instruments, this copper-based tubular product, with its "hard and soft" characteristics, has built a "metal vein" that spans ancient and modern times.
1. The core characteristics of copper pipes: derived from the natural advantages of copper
The excellent performance of copper pipes is rooted in the metallic nature of copper. These characteristics have been verified for thousands of years and are still shining in modern industry.

The extreme electrical conductivity and thermal conductivity are the "foundation" of copper pipes. The conductivity of pure copper tubes can reach 97% IACS (International Annealed Copper Standard), far exceeding aluminum (61% IACS) and steel (17% IACS), and the loss in power transmission is extremely low. The φ10×1mm copper tube is used as the lead of the motor commutator, which can efficiently conduct large currents without generating heat. In terms of thermal conductivity, the thermal conductivity of copper tubes reaches 401W/(m・K), which is 5 times that of steel tubes and more than 20 times that of plastic tubes. In air conditioning refrigerant tubes, it can increase the heat transfer efficiency by 30% and significantly reduce energy consumption.

Excellent plasticity and formability give copper tubes "versatility". The elongation of pure copper tubes can reach more than 45%. They can be drawn into capillaries with a diameter of 0.1mm (such as medical infusion needles) through cold drawing, and can also be made into elbows of any angle through hot bending (the minimum bending radius is only 1.5 times the tube diameter). This "hard and soft" characteristic enables it to accurately adapt to the spatial layout in complex piping systems (such as the oil circuit of a car engine), reduce the number of joints, and reduce the risk of leakage.

The natural corrosion resistance and antibacterial properties expand the application boundaries. Copper forms a dense oxide film (basic copper carbonate) in the air to prevent further corrosion of the internal metal, so the service life of the exposed copper pipe in the atmospheric environment can reach more than 50 years. In the water system, the antibacterial performance of copper pipes is particularly outstanding - it can kill 99% of Escherichia coli and Staphylococcus aureus within 2 hours, which meets FDA food contact standards and is an ideal choice for water supply and drainage pipes in hospitals and high-end residential buildings.
2. Classification of copper pipes: precise division from material to process
The classification system of copper pipes reflects both material differences and process characteristics. Different types of copper pipes have clear boundaries in performance and application.
1. Classification by material: Performance gradient of purity and alloy
Pure copper tube (red copper tube): copper content ≥99.5%, represented by T2 (99.90% copper) and TU1 (oxygen-free copper, 99.97% copper). T2 copper tube has excellent conductivity (conductivity 97% IACS), moderate cost, and is widely used in water supply and drainage, air conditioning refrigerant pipes; TU1 oxygen-free copper tube has oxygen content ≤0.003%, no pores and inclusions, and is suitable for high vacuum systems (such as vacuum pipelines for semiconductor manufacturing) and capillary tubes (φ0.5×0.1mm) of precision instruments.
Brass tube: copper-zinc alloy tube, zinc content 5%-45%, H62 (62% copper, 38% zinc) and H68 (68% copper, 32% zinc) are common. H62 brass tubes are stronger than pure copper (tensile strength 300MPa vs 200MPa), 15%-20% cheaper, and suitable for architectural decoration (such as guardrails, door handles) and low-pressure water pipes; H68 brass tubes have excellent plasticity (elongation 40%), and are special materials for ammunition shells and musical instrument blowpipes, and can withstand complex stamping and forming.
Bronze tubes: copper-tin alloy tubes (tin bronze) or special bronze tubes (such as phosphor bronze, beryllium bronze). QSn6.5-0.1 tin bronze tubes have outstanding wear resistance and are used for bearing bushings of ships and shaft seals of chemical pumps; QBe2 beryllium bronze tubes have a strength of 1200MPa after heat treatment, and have both high conductivity and fatigue resistance. They are the core pipes of aerospace hydraulic systems.
White copper tubes: copper-nickel alloy tubes, containing 10%-30% nickel, such as B10 (90% copper, 10% nickel), B30 (70% copper, 30% nickel). White copper tubes have excellent seawater corrosion resistance (corrosion rate ≤ 0.02mm/year) and are not brittle at low temperatures. They are the preferred material for low-temperature pipelines of LNG carriers and heat exchange tubes of seawater desalination equipment.
3. Forming process of copper tubes: from casting to precision drawing
The performance and form of copper tubes depend largely on the manufacturing process. From rough blanks to precision pipes, every step reshapes its microstructure.

The production of seamless copper tubes is the art of "plastic deformation". Take T2 seamless copper tube as an example: first, electrolytic copper is melted and cast into a Φ80mm solid copper rod; after heating to 600℃, it is punched into a Φ90×10mm hollow rough tube by a punching machine; then it enters the cold rolling mill, and after multiple rolling (deformation rate of more than 70%), the outer diameter is reduced to Φ22mm, and the wall thickness is controlled at 1mm (tolerance ±0.03mm); for high-precision pipes (such as air conditioning refrigerant pipes), bright annealing (400℃ hydrogen protection) is required to eliminate stress, and then cold drawing to Φ19×0.8mm through a mold, the surface roughness reaches Ra0.4μm, to ensure smooth flow of refrigerant.

Welded copper tubes are characterized by "high efficiency and continuity". The brass strip (H62) is rolled into a round tube by a forming machine, and the seam is heated by high-frequency induction welding (current frequency 400kHz), and fused under pressure (the weld strength reaches 90% of the parent material). After welding, it is annealed and sized online to form a Φ10-Φ200mm welded tube. This process is suitable for mass production, and the cost is 20%-30% lower than that of seamless pipes. It is widely used in building water supply and drainage (such as Φ25×1mm tap water pipes).

Special forming processes have expanded the morphological boundaries of copper pipes. The continuous casting and rolling process can directly roll the copper liquid into a Φ5-Φ30mm thin-walled copper tube, eliminating the casting process and increasing efficiency by 50%; while the explosive composite process can combine copper tubes with steel, aluminum and other materials to form a "copper-steel composite tube", which not only retains the conductivity of copper, but also reduces costs with the strength of steel (such as power grounding devices).
4. Core application scenarios: full coverage from people's livelihood to cutting-edge technology
The application map of copper tubes spans from "millimeter level" to "meter level", releasing customized performance in different scenarios.
1. HVAC and refrigeration: extreme use of thermal conductivity
Air conditioning refrigerant pipe: More than 90% of household air conditioners use Φ9.52×0.8mm, Φ12.7×1mm T2 seamless copper tubes. Their high thermal conductivity (401W/(m・K)) ensures efficient heat exchange of refrigerants (Freon, R32), which saves more than 10% energy compared to aluminum tube systems; while the branch pipes (Φ28×1.2mm) of commercial central air conditioners require precise size control to avoid uneven refrigerant diversion.
Refrigerator evaporator/condenser: Φ6×0.7mm H65 brass welded tubes are used, and serpentine pipes are formed by continuous bending to increase the heat exchange area. Its resistance to refrigerant corrosion ensures that the refrigerator life is more than 10 years.
2. Water supply and drainage and gas: double guarantee of safety and durability
High-end building water supply pipe: Φ15-Φ100mm T2 seamless copper pipe (smooth inner wall Ra≤0.8μm) is used in hospitals and five-star hotels. The water flow resistance is 30% lower than that of plastic pipes, and copper ions can inhibit the growth of Legionella (sterilization rate 99%), which meets the WHO drinking water safety standards and has a service life of up to 70 years (the same life as the building).
Gas transmission pipe: Φ10-Φ50mm H62 brass pipe (with anti-corrosion coating) is used for natural gas meter connection. It is non-magnetic (avoids electric sparks) and anti-aging (stable performance from -20℃ to 60℃), which is safer than plastic gas pipes.
3. Power and Electricity: The Core Value of Conductivity
Motors and Transformers: The rotor coils of large generators use TU1 oxygen-free copper tubes of Φ8×2mm, which can withstand high currents of more than 1000A by removing heat through cooling water. The cooling oil pipes of transformers (Φ25×2mm) use the high thermal conductivity of copper tubes to remove the heat generated by core loss.
Cables and Busbars: The grounding copper tubes (Φ50×3mm) of high-voltage cables must have a conductivity of more than 97% to ensure rapid discharge of fault currents. The contact copper tubes (Φ100×5mm) of the third rail of the subway are silver-plated on the surface to reduce the contact resistance with the power shoe.
4. Cutting-edge technology and industry: performance challenges in extreme environments
Aerospace: The aircraft hydraulic system uses Φ6×1mm beryllium bronze tubes (QBe2), which maintain a tensile strength of 1200MPa at -55℃ to 120℃, ensuring precise movement of the servo; the rocket fuel delivery pipe (Φ20×2mm) uses TU1 oxygen-free copper tubes to withstand the low-temperature impact of liquid oxygen (-183℃).
Medical equipment: The capillary catheter (Φ0.8×0.1mm) of the infusion pump uses TU2 oxygen-free copper tubes, and the dimensional accuracy (tolerance ±0.01mm) ensures the stability of the liquid flow; and the cooling pipeline (Φ12×0.5mm) of the nuclear magnetic resonance (MRI) does not interfere with magnetic field imaging because the copper tube is non-magnetic.
Shipbuilding and marine engineering: B30 white copper tubes (Φ150×5mm) are used for cryogenic pipelines of LNG carriers, which are not brittle in a -163℃ liquid nitrogen environment; B10 white copper tubes are used for heat exchange tubes of seawater desalination equipment, with an annual corrosion rate of ≤0.01mm and a service life of 20 years.
V. Future Trends: Two-Way Evolution of Green and Smart
With the upgrading of industries and the improvement of environmental protection requirements, copper tubes are evolving towards a more efficient, environmentally friendly and intelligent direction.

Green manufacturing and recycling have become an industry consensus. The recycling rate of copper tubes is as high as over 95%, and waste air conditioning copper tubes can be remade into new tubes after smelting, with almost no impact on performance (conductivity only decreases by 1%-2%). Short-process smelting (using waste copper as raw material) reduces carbon emissions by 60% compared to traditional processes. At present, the proportion of recycled copper in European and American countries has reached over 60%.

High-performance alloys and thin-walled materials continue to break through. The new copper-chromium-zirconium alloy tube (CuCrZr) has a conductivity of 85% IACS and a strength of 450MPa. It is used for motor leads of new energy vehicles to meet the dual requirements of "high conductivity + high strength". The thin-wall technology (such as reducing the thickness of air-conditioning tubes from 0.8mm to 0.6mm) reduces the copper usage per meter of copper tube by 15% while ensuring pressure resistance, reducing costs and resource consumption.

Intelligent applications expand functional boundaries. "Smart copper tubes" with IoT sensors embedded in building water supply pipes can monitor flow, pressure and corrosion status in real time, and warn of water leakage risks through the cloud; and in industrial heat exchange systems, copper tubes with laser-engraved micro-grooves on the inner wall have a 30% higher heat exchange efficiency than ordinary light tubes, helping equipment save energy and reduce consumption.

From the bronze water pipes of ancient civilizations to the liquid cooling pipes of modern data centers, copper tubes, with their golden combination of "conductivity, thermal conductivity, and corrosion resistance", have been the "all-round player" among metal pipes for thousands of years. It does not have the extreme corrosion resistance of stainless steel, but it covers a wider range of scenarios with a higher cost-effectiveness; it does not have the extreme strength of alloy tubes, but it has become a "rigid need" for people's livelihood and industry with its comprehensive performance. In the future, with the deepening of material technology and green manufacturing, copper tubes will continue to expand their application boundaries while maintaining their core advantages, and continue to write the legend of "metal veins".