What are the causes of blackening of coils?

Xiaobian today with you to understand the problem of coil blackening, of course, in life people often encounter the problem of coil blackening, many people do not know what this phenomenon is for, please look below:


First, copper wire annealing process
Copper wire annealing refers to a metal heat treatment in which copper wire is slowly heated to a certain high temperature and then maintained 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 grains, adjust tissues, eliminate tissue defects. However, Beijing Kexun Hongsheng high temperature line manufacturer feels that once the temperature is higher than 50 °C in the production process, the required pumping time is insufficient, the SO2 content is high, and the impurity of the protective gas will cause the lack of annealing, and the copper wire will be easy to blacken after a period of time.

Second, the material problem of the insulation layer
Paint can be divided into five categories: impregnating paint, wire enameled paint, covering paint, silicon steel sheet paint, and anti-corona paint. Among them, impregnating paint is used for impregnating motors and electrical coils. Impregnating 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 object, and bond the coil into a strong whole, effectively improving the integrity of the insulation system, thermal conductivity, moisture resistance, dielectric strength and mechanical strength performance. Secondly, it also plays a role in heat dissipation, if the insulation paint is soaked, the dried coil can be regarded as a whole, and the heat of the inner and outer layers can be easily conducted, thus playing the role of dissipating heat. At present, China’s impregnating paint, insulating oil production process, preparation method, patented formula technical data is still relatively backward, the production and processing of impregnating paint basically only play a short-term role, over time will appear drop, failure phenomenon.

 Square membrane wrapped wire

Third, the problem of use

In the process of using coil copper wire, we often have such problems – collision friction, slow flushing, a large amount of moisture contact with the coil, the use of waste engine oil lubrication, resulting in the destruction of residues and insulation on the surface of the conductor, and the oxidation of the conductor during subsequent processing.
Fourth, technical reasons
In the past, most manufacturers in China used universal copper rods, and the copper content number could reach 99.95%, but even now, there was still O in copper. The reason is that copper itself is not oxygen-free copper, and the surface of copper will inevitably be oxidized in contact with air during processing. Now the introduction of oxygen-free copper advanced production technology, as well as domestic self-developed oxygen-free copper production technology, so that the entire copper wire industry has used oxygen-free copper, which has undoubtedly greatly improved the blackening problem of copper wire. However, due to the processing of the copper rod, especially the use of the toughening process and the poor storage conditions of the finished copper wire core, the copper wire itself will still have slight oxidation.

Post time: Mar-15-2023