Annealing process of enamelled wire

The purpose of annealing is to make the conductor due to the mold tensile process due to lattice changes and hardening of the wire through a certain temperature heating, so that the molecular lattice rearrangement after the recovery of the process requirements of the softness, at the same time to remove the conductor surface residual lubricants, oil, etc., during the tensile process, so that the wire is easy to paint, ensure the quality of enamelled wire.

The most important thing is to ensure that the enamelled wire has suitable softness and elongation during the use of the winding, while helping to improve the conductivity.

The larger the deformation degree of conductor, the lower the elongation and the higher the tensile strength.

Copper wire annealing, commonly used in three ways: disk annealing; Continuous annealing on wire drawing machine; Continuous annealing on the lacquer machine. The first two methods can not meet the requirements of coating technology. Disk annealing can only soften the copper wire, and the oil is not complete, because the wire is soft after annealing, and the bending is increased when the wire is set off.

Continuous annealing on the wire drawing machine can soften the copper wire and remove the surface grease, but after annealing, the soft copper wire is wound to the wire reel to form a lot of bending. Continuous annealing before painting on the paint machine can not only achieve the purpose of softening and removing oil, but also the annealed wire is straight, directly into the paint device, can be coated with uniform paint film.

The temperature of annealing furnace should be determined according to the length of annealing furnace, copper wire specifications and line speed. At the same temperature and speed, the longer the annealing furnace, the more fully restored the conductor lattice. When the annealing temperature is low, the higher the furnace temperature, the better the elongation, but the opposite phenomenon occurs when the annealing temperature is very high, the higher the temperature, the smaller the elongation, and the surface of the wire lose luster, and even easy to break.

Annealing furnace temperature is too high, not only affect the service life of the furnace, but also easy to burn the line when stopping and finishing. The maximum temperature of annealing furnace is required to be controlled at about 500℃. It is effective to select temperature control points at similar positions of static and dynamic temperature.

Copper is easy to oxidize at high temperature, copper oxide is very loose, the paint film can not be firmly attached to the copper wire, copper oxide has catalytic effect on the aging of the paint film, on the flexibility of the enameled wire, thermal shock, thermal aging have adverse effects. To copper wire is not oxidized, it is necessary to make the copper wire at high temperature without contact with oxygen in the air, so there should be a protective gas. Most annealing furnaces are water-sealed at one end and open at the other.

The water in the annealing furnace sink has three functions: it closes the furnace, cools the wire, and generates steam as a protective gas. At the beginning of the drive due to the annealing tube of little steam, can not be timely out of the air, the annealing tube can be filled with a small amount of alcohol solution (1:1). (Be careful not to drink pure alcohol and control the amount used)

The water quality in the annealing tank is very important. Impurities in the water will make the wire is not clean and affect the paint, unable to form a smooth paint film. The chlorine content of the water used should be less than 5mg/l and the electrical conductivity should be less than 50μΩ/cm. After a period of time, chloride ions attached to the surface of the copper wire will corrode the copper wire and the paint film, resulting in black spots on the surface of the wire in the paint film of the enamelled wire. The gutters must be cleaned regularly to ensure quality.

The water temperature in the sink is also required. High water temperature is conducive to the occurrence of water steam to protect the annealing copper wire, the wire leaving the tank is not easy to bring water, but to the cooling of the wire. Although the low water temperature plays a cooling role, there is a lot of water on the wire, which is not conducive to painting. Usually, the thick line is cooler and the thin line is warmer. When the copper wire leaves the water surface and makes a splash, the water temperature is too high.

Generally, the thick line is controlled in 50~60℃, the middle line is controlled in 60~70℃, and the fine line is controlled in 70~80℃. Because of the high speed and serious water problem, the thin wire should be dried by hot air.

Post time: Mar-21-2023