Copper wire billets for electrical use
Electrical copper wire billets are the fundamental raw material for producing various types of electrical copper wire. Made from high-purity copper, these billets are produced through continuous casting or upcasting to form round or shaped billets. They are widely used in the production of copper wire for applications such as wire and cable, motor windings, and electrical connectors. These billets typically come in round billets with diameters of 8-30 mm or shaped billets of corresponding cross-sections. Based on purity, they can be categorized into high-purity copper wire billets (copper content of 99.99% or higher) and standard copper wire billets (copper content of 99.95% or higher). The former are suitable for high-end wire and cable, while the latter are used in general electrical products. They are a key link in the electrical copper product industry chain.
The production process for electrical copper wire billets involves core steps such as raw material purification, smelting and casting, and surface treatment. The precision of this process directly impacts the quality of the subsequent copper wire. First, electrolytic copper with a purity of at least 99.95% is used as the raw material. This is then subjected to fire refining to further remove impurities. The copper is then heated to 1180-1230°C in a reverberatory furnace or an industrial frequency induction furnace. A phosphor copper deoxidizer is added to reduce the oxygen content to below 0.002%. An online degassing system is also used to remove hydrogen and other gases to ensure melt purity. There are two main casting processes: The upward continuous casting method is suitable for producing small round billets. Molten copper is drawn upward through a graphite crystallizer to solidify into billets. Cooling water is passed through the crystallizer to control the solidification rate, resulting in a smooth billet surface with a diameter tolerance of ±0.1 mm. The horizontal continuous casting method is suitable for producing larger billets. Molten copper is continuously cast horizontally through the crystallizer , producing round billets or shaped billets with diameters exceeding 30 mm. This method offers high production efficiency but requires further surface finishing. After casting, the wire billets undergo a peeling process to remove surface oxide layers and defects. The peeling thickness is 0.5-1 mm, ensuring a surface roughness Ra ≤ 3.2 μm. Finally, an online inspection system thoroughly checks the diameter, roundness, and surface quality, and rejects any defective products promptly.
The performance characteristics of electrical copper wire billets determine the quality of downstream copper wires. First, purity is the core indicator. The copper content of high-purity copper wire billets is ≥99.99%, and the total impurities are ≤0.01%. In particular, the content of brittle elements such as lead and bismuth is strictly controlled to be ≤0.0005% to avoid wire breakage during the subsequent wire drawing process. Second, the microstructure is uniform. By controlling the casting cooling rate, the grains are refined and evenly distributed, with an average grain size of ≤50μm, reducing stress concentration during wire drawing. Third, the mechanical properties are moderate, with the tensile strength controlled at 200-250MPa and the elongation ≥30%, ensuring sufficient strength for easy handling and processing, and good plasticity to meet subsequent cold working requirements. Fourth, the surface quality is excellent. After peeling treatment, the surface is free of cracks, inclusions, scratches and other defects, which can reduce the wear of the wire drawing die and extend the life of the die. Fifth, the dimensional accuracy is high, with the round billet diameter tolerance ≤±0.1 mm and the roundness error ≤0.05 mm, ensuring uniform wire diameter during subsequent wire drawing.
In terms of application scenarios, electrical copper wire billets are the first gateway to the electrical copper wire industry chain. In the wire and cable industry, high-purity copper wire billets are drawn and annealed to form conductive cores for high-voltage cables and communication cables. For example, the conductive cores of 500kV cross-linked polyethylene cables require 99.99% purity copper billets to ensure low-loss transmission. In motor manufacturing, copper wire billets are drawn into enameled wire for motor windings. Small and medium-sized motors typically use billets with diameters of 8-12 mm, while large motors use billets with diameters of 15-20 mm. In the electrical equipment sector, copper wire billets are cold-worked into connectors such as copper busbars and rods. For example, the conductive copper busbars in switchgear are often made from rectangular copper wire billets. In the new energy sector, the copper tabs for power batteries require high-purity copper billets to ensure high conductivity and weldability. In the electronics and information technology sector, the production of ultra-fine copper wire (diameter ≤ 0.1 mm) relies on high-precision copper billets for integrated circuit leads and micromotor windings. With the technological upgrading of the electrical industry, the requirements for the purity and precision of copper wire billets are increasing.
Industry trends indicate that electrical copper wire billets are moving toward ultra-high purity, precision molding, and green production. Breakthroughs have been achieved in the research and development of ultra-high-purity copper wire billets (copper content exceeding 99.999%). Through vacuum melting and regional purification, impurity levels have been reduced to below 10 ppm, meeting the demands of high-end electronics. The promotion of precision molding technology allows for the direct casting of billets with special cross-sections, such as trapezoidal and semi-circular shapes, reducing subsequent machining allowances and increasing material utilization by over 15%. Green production processes are becoming increasingly popular, with clean energy smelting, such as natural gas or electric heating, replacing traditional coke ovens to reduce carbon emissions. The utilization of recycled copper is increasing. Through advanced pyrometallurgical and hydrometallurgical refining techniques, the performance of recycled copper wire billets has reached the level of virgin copper, while reducing production energy consumption by 30%. In the future, with the rapid development of industries such as 5G communications and new energy vehicles, demand for high-quality electrical copper wire billets will continue to grow, driving further advancements in purification technology, molding processes, and environmentally friendly production, providing the electrical industry with higher-quality basic raw materials.
