What are the reasons for the black coil?

Today, Xiaobian and everyone know about the problem of blackening of the coil. Of course, people often encounter the problem of blackening of the coil in life. Many people don’t know why this phenomenon is. Please look down:


1、 Copper wire annealing process
Copper wire annealing refers to a metal heat treatment in which the copper wire is slowly heated to a certain high temperature and then kept for a period of time, and then cooled at a corresponding rate. Copper wire annealing can reduce hardness, improve machinability, eliminate residual stress, stabilize size, and reduce deformation and crack tendency; Refine the grain, adjust the structure and eliminate the structural defects. However, the manufacturer of Beijing Kexun Hongsheng High-temperature Wire thinks that once the temperature is higher than 50 ℃ during the production process, the specified extraction time is insufficient, the SO2 content is high, and the protective gas is not pure, which will cause the deficiency of annealing. After a period of time, the copper wire will be easy to blacken.

2、 Material problem of insulation layer
The paint can be divided into five categories: impregnating paint, enameled wire paint, covering paint, silicon steel sheet paint and anti-corona paint. Among them, impregnating paint is used for impregnating motor and electrical coil. Impregnated paint can play a role in filling the gaps and micropores in the insulation system, and form a continuous paint film on the surface of the impregnated material, and make the coil bond into a solid whole, effectively improving the integrity, thermal conductivity, moisture resistance, dielectric strength and mechanical strength of the insulation system. Secondly, it also plays the role of heat dissipation. If the insulating paint is soaked, the dried coil can be seen as a whole, and the heat of the inner and outer layers can be easily transferred, thus playing the role of heat dissipation. At present, China’s impregnating paint and insulating oil production process, preparation method, patent formula and technical data are relatively backward. The impregnating paint produced and processed basically only plays a temporary role, and will fall and fail over time.


3、 Problems in use
In the process of using the coil copper wire, we often encounter such problems – collision and friction, slow washing, large amount of water contacting with the coil, use of waste oil lubrication, resulting in residue on the surface of the conductor and damage to the insulation layer, and conductor oxidation during subsequent processing.
4、 Technical reasons
Previously, most manufacturers in China used universal copper rods, and the copper content could reach 99.95%, but even now, there is still O in copper. The reason is that copper itself is not oxygen-free copper. During processing, the surface of copper will inevitably contact with air and oxidize. By now, the advanced production technology of oxygen-free copper has been introduced in China, as well as the oxygen-free copper production technology developed by China itself, so that the entire copper wire industry has used oxygen-free copper, which undoubtedly has greatly improved the blackening problem of copper wire. However, due to the processing of the copper rod, especially the application of the toughening process and the poor storage conditions of the finished copper wire core, the copper wire itself will still be slightly oxidized.

Post time: Feb-11-2023