1. Pay off
On a normally running enameled wire, most of the operator's energy and physical strength are consumed in the pay-off part. The replacement of the pay-off reel requires the operator to pay a lot of labor, and the joints are prone to quality problems and operational failures when changing the wires. An effective method is to pay off with large capacity. The key to pay off is to control the tension. When the tension is large, it will not only draw the conductor thin, make the surface of the wire lose its brightness, but also affect many properties of the enameled wire. From the appearance point of view, the enameled wire that is drawn thinner has poor gloss; from the performance point of view, the elongation, resilience, flexibility, and thermal shock of the enameled wire are all affected. If the pay-off tension is too small, the line will easily jump and cause the line to be merged and the line to touch the furnace mouth. When paying off, the most fear is that the half-turn tension is high and the half-turn tension is small. This will not only cause the wires to loosen, break, and be thinned one by one, but also cause large jumps of the wires in the oven, resulting in failures of merging and touching the wires. Pay-off tension should be even and appropriate. Installing a booster wheel in front of the annealing furnace is very helpful for tension control. The maximum non-extension tension of soft copper wire at room temperature is about 15kg/mm2, the maximum non-extension tension at 400℃ is about 7kg/mm2; the maximum non-extension tension at 460℃ is 4kg/mm2; the maximum non-extension tension at 500℃ The extension tension is 2kg/mm2. In the normal enameled wire coating process, the tension of the enameled wire is significantly less than the non-extended tension, which is required to be controlled at about 50%, and the pay-off tension should be controlled at about 20% of the non-extended tension.
Large-size and large-capacity spools generally use radial rotary pay-offs; medium-size wires generally use over-end or brush-type pay-offs; fine-size wires generally use brush-type or double-cone pay-offs.
Regardless of the method of wire pay-off, there are strict requirements on the structure and quality of the bare copper wire spool. The surface should be smooth to ensure that the wire is not scratched. There are 2-4mm radius r angles on both sides of the shaft and inside and outside the side plates. Ensure that the line can be discharged evenly during the pay-off process. After the spool is processed, a dynamic and static balance test must be performed. The brush pay-off device requires the shaft core diameter: the diameter of the side plate is less than 1:1.7; the over-end pay-off requirement is less than 1:1.9, Otherwise, wire breakage will occur when the wire is paid to the shaft core.
The purpose of annealing is to heat the wire hardened by the change of the crystal lattice due to the mold stretching process to a certain temperature to restore the softness required by the process after the molecular crystal lattice is rearranged, and to remove the residue on the conductor surface during the stretching process. Lubricants, oil stains, etc., make the wire easy to paint and ensure the quality of the enameled wire. The most important thing is to ensure that the enameled wire has suitable softness and elongation during use as a winding, and at the same time helps to improve the conductivity.
The greater the deformation of the conductor, the lower the elongation and the higher the tensile strength.
There are three commonly used methods for annealing copper wire: coil annealing; continuous annealing on wire drawing machine; continuous annealing on enamelled machine. Neither of the first two methods can meet the requirements of the enameling process. Coil annealing can only soften the copper wire, but the degreasing is not complete. As the wire becomes soft after annealing, the bend is increased when the wire is laid out. Continuous annealing on the wire drawing machine can achieve the softening of the copper wire and remove the surface grease, but the soft copper wire is wound on the wire reel to form a lot of bends after annealing. Continuous annealing before painting on the enamelling machine can not only achieve the purpose of softening and degreasing, but also the annealed wire is straight, directly enters the painting device, and can be coated with a uniform paint film.
The temperature of the annealing furnace should be determined according to the length of the annealing furnace, copper wire specifications, and line speed. At the same temperature and speed, the longer the annealing furnace, the more fully recovered the conductor lattice. When the annealing temperature is low, the higher the furnace temperature, the better the elongation, but when the annealing temperature is high, the opposite phenomenon will occur. The higher the temperature, the smaller the elongation, and the surface of the wire loses its luster and is even vulnerable to brittle fracture. .
The temperature of the annealing furnace is too high, which not only affects the service life of the furnace, but also easily burns and breaks when the line is shut down and threaded. The maximum temperature of the annealing furnace is required to be controlled at about 500°C. Two-stage temperature control is used for the furnace, and it is effective to select the temperature control point at a position where the static and dynamic temperatures are similar. Copper is easy to oxidize at high temperature. Copper oxide is very loose, and the paint film cannot be firmly attached to the copper wire. Copper oxide has a catalytic effect on the aging of the paint film, and has adverse effects on the flexibility, thermal shock and thermal aging of the enameled wire. . If the copper wire is not oxidized, it is necessary to keep the copper wire at high temperature from contact with oxygen in the air, so there must be a protective gas. Most annealing furnaces are sealed with water at one end and open at the other end. The water in the water tank of the annealing furnace has three functions: closing the furnace mouth, cooling the wire, and generating steam as a protective gas. Since the water vapor in the annealing tube is very small when driving, the air cannot be removed in time, so a small amount of alcohol solution (1:1) can be poured into the annealing tube. (Be careful not to pour 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 unclean and affect the paint, and it will not be able to form a smooth paint film. The chlorine content of the used water should be less than 5mg/l, and the conductivity should be less than 50μΩ/cm. The chloride ion attached to the surface of the copper wire will corrode the copper wire and the paint film after a period of time, and produce black spots on the surface of the wire in the paint film of the enameled wire. To ensure quality, the sink must be cleaned regularly.
The temperature of the water in the sink is also required. High water temperature is conducive to the generation of water vapor to protect the copper wire during annealing. The wire leaving the water tank is not easy to carry water, but it is not good for the cooling of the wire. Although low water temperature has a cooling effect, there is a large amount of water on the wire, which is not good for painting. Generally, the water temperature of the thick line is lower, and the water temperature of the thin line is higher. When the copper wire makes the water vaporize and splash when it leaves the water surface, it means that the water temperature is too high. Generally, the thick line is controlled at 50~60°C, the middle line is controlled at 60~70°C, and the thin line is controlled at 70~80°C. Because of the high speed of the thin thread, the water-carrying problem is serious, so hot air drying should be used.