Copper coil: a versatile metal coil with high electrical and thermal conductivity

Copper coil is a continuous coil made from pure copper or copper alloys through cold rolling, hot rolling, or annealing processes. Its excellent electrical and thermal conductivity, as well as its ductility, make it a key raw material in the electrical, decorative, and industrial manufacturing sectors. It combines the dual advantages of ease of processing and high performance.
I. Core Classifications of Copper Coil
1. Classification by Production Process
Cold-rolled copper coil: Rolled at room temperature, it boasts a thin thickness (0.05-3mm), a smooth surface, high dimensional accuracy, and high hardness. It is suitable for the processing of precision parts (such as copper foil for circuit boards and connectors) and decorative panels.
Hot-rolled copper coil: Rolled at high temperatures, it boasts a thick thickness (3-20mm), excellent toughness, and is easy to bend and weld. It may have an oxide scale on the surface and is primarily used for structural parts (such as copper pipe blanks and large electrical connectors).
2. Classification by Material
Pure copper coil (red copper coil): Contains a copper content of ≥99.5%, offers optimal electrical and thermal conductivity, good ductility, and is non-magnetic. It is suitable for use in the electrical sector (cables, transformer windings) and food contact parts (tableware and storage tanks). Brass Coil (Copper-Zinc Alloy): Contains 30%-40% zinc, boasts higher strength than pure copper, lower cost, and is wear-resistant and corrosion-resistant. It is used in hardware (door locks, hinges), pipe fittings, and decorative accessories.
Bronze Coil (Copper-Tin Alloy): Contains 5%-15% tin, boasts high hardness and wear resistance, making it suitable for industrial applications (bearings, gears, and mechanical parts). Some specialized bronzes (such as phosphor bronze) can also be used in precision springs.
II. Core Performance: Advantages and Limitations
1. Advantages
Excellent Electrical and Thermal Conductivity: Pure copper has an electrical conductivity approximately 94% that of silver, making it a preferred choice in the electrical field. Its thermal conductivity is five times that of carbon steel, making it suitable for heat exchange components such as radiators and heat exchangers.
Excellent Ductility and Ease of Processing: It can be cold-rolled to ultra-thin thicknesses (such as micron-level copper foil), and can also be bent, stamped, and welded, making it suitable for complex part forming.
High Corrosion Resistance: It is resistant to rust in dry air and fresh water environments. Brass and bronze perform better in weak acid and alkaline environments, with a service life of up to decades. 2. Limitations
High Cost: Raw material prices are significantly higher than those of steel and aluminum. The cost of pure copper coils is approximately 8-10 times that of carbon steel coils, limiting their application in large-scale, low-cost scenarios.
Low Strength: Pure copper has low hardness and weak impact resistance, making it a poor substitute for steel in heavy-duty structural components. Alloying (e.g., brass or bronze) is required to enhance its strength.
Susceptible to Oxidation and Discoloration: Prolonged exposure to air can cause copper oxide (blackening) to form on the surface, affecting its appearance. Plating (e.g., nickel or chrome plating) or a protective agent is required.
III. Main Applications
Electrical and Electronics: Pure copper cold-rolled coils (copper foil) are used in circuit boards and lithium battery current collectors. Copper coils are cut and made into cable connectors and transformer coils, relying on their high conductivity.
Architectural Decoration: Pure copper coils (brushed/mirror finish) are used in hotel wall cladding and elevator decorative panels. Brass coils are used in door and window hardware and furniture fittings, balancing aesthetics and durability. Industrial Manufacturing: Bronze coils are processed into mechanical bearings and gears; brass coils are made into water pipes and gas pipe fittings; pure copper coils are used in heat exchangers and radiators, leveraging their high thermal conductivity.
Pure copper coils are used to make food-grade containers (such as copper pots); brass coils are used in musical instrument accessories (such as trumpet keys) and household hardware (such as zipper pulls).
IV. Selection and Maintenance Key Points
1. Selection Recommendations
Select pure copper coils for electrical and heat exchange applications; select brass coils for a balance of strength and cost; and bronze coils for heavy-duty, wear-resistant applications.
Use cold-rolled copper coils for precision parts and thin components; and hot-rolled copper coils for thick-walled structural parts and components requiring welding.
2. Maintenance Recommendations
Avoid humidity and high temperatures during storage. Cover with moisture-proof paper or apply anti-rust oil to prevent oxidation and discoloration.
Avoid scratching the surface with sharp tools during processing. Mirrored/brushed copper coils should be packaged separately to prevent wear. If the surface oxidizes, lightly sand it with fine sandpaper or wipe it with a specialized copper cleaner to restore the appearance (food-contact parts require a food-grade cleaner).
V. Future Development Trends
High-Performance Alloy Upgrades: Develop highly conductive and high-strength copper alloy coils (such as copper-beryllium alloys) for high-end applications such as aerospace and precision electronics.
Green Recycling: Copper is 100% recyclable without performance degradation. The future will strengthen the "production-recycling-reuse" closed loop to reduce carbon emissions.
Thinning and Precision: Promote upgrades in cold rolling processes to produce thinner copper foil coils (such as nanometer-thick) to meet the needs of flexible circuit boards and microelectronic devices.

In summary, although copper coils are relatively expensive, their core advantages of electrical and thermal conductivity and ease of processing make them irreplaceable in the electrical and high-end manufacturing sectors. With the optimization of alloy technology and processes, their applications will further expand towards precision and green manufacturing.