Seamless copper tubes for air conditioning and refrigeration equipment
Seamless copper tubes for air conditioning and refrigeration equipment are core pipes used to transport refrigerants in refrigeration systems. Due to copper’s excellent thermal conductivity, corrosion resistance, and low-temperature toughness, they play a crucial role in heat exchange and media transmission in refrigeration equipment such as air conditioners, refrigerators, and cold storage. They typically have an outer diameter of 6-35mm and a wall thickness of 0.5-2mm. Materials commonly used are TP2 phosphorus-deoxidized copper (containing ≥99.9% copper and 0.015%-0.040% phosphorus) and T2 pure copper. TP2 copper tubes, due to their low oxygen content (≤0.003%), offer superior weldability and corrosion resistance, and account for over 90% of air conditioning refrigerant piping.
The production process for seamless copper tubes for air conditioners requires precise steps, including smelting, casting, extrusion, stretching, and annealing. First, electrolytic copper is smelted in an industrial frequency induction furnace at a controlled temperature of 1100-1150°C. Phosphorus is added for deoxidation, and an inert gas atmosphere is used to prevent secondary oxidation. The resulting ingots are then cast into round ingots with a diameter of 80-120mm. Semi-continuous casting is used at a cooling rate of 80-120°C/min to ensure the absence of pores and looseness. In the extrusion process, the ingots are heated to 650-700°C and extruded into rough tubes using a horizontal extruder with an extrusion ratio of 15-25. The rough tubes have an outer diameter of 30-60mm and a wall thickness of 3-8mm. Carbide is used in the extrusion die to ensure a smooth inner surface. Stretching is key to achieving high precision. Multi-pass cold drawing is performed, with each pass deforming 20%-30%. Lubricated with specialized drawing oil, the final outer diameter tolerance is controlled to ±0.05mm, the wall thickness tolerance is ±0.03mm, and the inner wall roughness Ra ≤ 0.8μm. Annealing is performed under nitrogen at 350-400°C for 1-2 hours to eliminate work hardening and reduce the copper tube’s hardness to HV50-70. The elongation is ≥35%, meeting bending requirements. Finally, eddy current testing and hydrostatic testing (test pressure ≥ 2.5MPa) are performed to ensure the absence of leaks and defects.
The performance advantages of seamless copper tubes for air conditioning make them an ideal choice for the refrigeration field. First, they offer excellent thermal conductivity. TP2 copper tubes have a thermal conductivity of ≥ 380W/(m・K) , eight times that of steel tubes and 1.5 times that of aluminum tubes. They can efficiently transfer heat from the refrigerant, improving air conditioning heat exchange efficiency by 15%-20% . Second, they offer excellent corrosion resistance. In new, environmentally friendly refrigerants such as R32 and R410A , their annual corrosion rate is ≤ 0.002mm , resulting in a service life of over 15 years, far exceeding the 5-8 years of aluminum tubes. Third, they exhibit excellent low-temperature toughness. Within an operating temperature range of -50 °C to 120 °C, their impact energy is ≥ 20J , eliminating the risk of brittle fracture and adapting to temperature fluctuations in refrigeration systems. Fourth, they feature high-precision dimensional control with an outer diameter deviation of ≤ 0.05mm, ensuring a close fit with the fins and reducing contact thermal resistance. Fifth, they offer excellent bending performance, with a minimum bending radius of 1.5 times the tube diameter, allowing for flexible shaping at the installation site, reducing construction complexity.
In various applications, seamless copper tubes are the “vascular system” of refrigeration equipment. In split-type air conditioners, the indoor and outdoor unit connecting pipes use TP2 copper tubes (Ø9.52mm × 0.8mm and Ø12.7mm × 1.0mm), connected by a bell-shaped connection to ensure a tight refrigerant seal. In central air conditioners, the evaporator and condenser use Ø7mm × 0.7mm internally threaded copper tubes. The spiral pattern on the inner surface increases the heat exchange area by 30%, improving cooling efficiency. In refrigerator refrigeration systems, capillary tubes and evaporators use thin-walled copper tubes (Ø4-6mm) to precisely control refrigerant flow. In cold storage equipment, condensing coils use seamless copper tubes (Ø19-25mm) to withstand long-term operation with high-pressure refrigerants (pressure ≥1.6MPa). In automotive air conditioners, the use of special-shaped flat tubes (cross-section 8mm × 2mm) reduces wind resistance and improves heat exchange efficiency by 10%.
Industry trends indicate that seamless copper tubes for air conditioners are moving towards thinner walls, higher efficiency, and environmentally friendly features. Breakthroughs in the production of ultra-thin-wall copper tubes (wall thickness ≤ 0.5mm) have reduced weight by 20% while maintaining strength, lowering material costs. Optimized internal thread structures (such as cross-threading and variable pitch) have further increased heat transfer efficiency by 10%-15%. Environmentally friendly processing techniques, including the use of biodegradable drawing oil and clean energy, have been promoted to reduce production pollution. The application of intelligent manufacturing technology, through online dimensional inspection and defect detection, has increased product qualification rates to 99.8%. A comprehensive recycling system has resulted in a recycling rate of over 98% for scrap copper tubes, reducing energy consumption by 70% compared to virgin copper. With the advancement of variable-frequency air conditioners and heat pump technology, demand for high-efficiency heat transfer copper tubes will continue to grow, driving the industry to achieve greater breakthroughs in material innovation and structural design.
