p>After the insulating varnish is applied to the wire, the solvent and thinner are first evaporated in the baking process. Liquids turn into gases in two forms: evaporation and boiling. The molecules on the surface of the liquid enter the air, which is called evaporation. It can be carried out at any temperature. It is affected by temperature and density. High temperature and low density can accelerate evaporation. When the density reaches a certain amount, the liquid no longer evaporates and becomes saturated. Molecules inside the liquid turn into gas to form bubbles that rise to the surface of the liquid, and the bubbles burst to release vapor.
The paint film of the enameled wire needs to be smooth, and the vaporization of the solvent must be carried out in the form of evaporation, and boiling is absolutely not allowed, otherwise the surface of the enameled wire will produce air bubbles and hair particles. As the solvent in the lacquer evaporates, the insulating varnish becomes thicker and thicker, and the time for the solvent inside the lacquer to migrate to the surface becomes longer, especially for thick enameled wires. Due to the thickness of the lacquer, the evaporation time needs to be prolonged to avoid the internal solvent. Evaporation phenomenon, a smooth paint film is obtained.
The temperature of the evaporation zone of the oven depends on the boiling point of the solution, and the temperature of the evaporation zone is lower if the boiling point is lower. However, the temperature of the paint liquid on the surface of the wire is transferred from the furnace temperature, coupled with the heat absorption of the evaporation of the solution and the heat absorption of the wire, so the temperature of the paint liquid on the surface of the wire is much lower than the furnace temperature.
Although the baking of fine-sized enameled packages also has an evaporation stage, the solvent evaporates in a very short period of time due to the thin paint on the wire, so the temperature in the evaporation area can be higher. If the paint film is curing Lower temperatures are required, such as polyurethane enameled wires, and the temperature in the evaporation zone is higher than the temperature in the curing zone. If the temperature of the evaporation zone is low, the surface of the enameled wire will form shrinking enamel hair, and the shape of the hair is sometimes wavy or slub-like, and sometimes concave. This is because a uniform layer of paint is formed on the wire after the wire is painted. If it is not quickly baked to form a film, the paint will shrink due to the surface tension of the paint and the effect of the wetting angle. When the temperature of the evaporation zone is low, the temperature of the paint will also Low, the solvent evaporation time is long, the movement of the paint liquid when the solvent evaporates is small, and the leveling is poor. When the temperature of the evaporation zone is high, the temperature of the paint liquid is also high, the evaporation time of the solvent is short, and the movement of the paint liquid when the solvent evaporates High performance, good leveling, the surface of the enameled wire is smooth.
If the temperature of the evaporation zone is too high, the solvent in the outer layer of the painted wire will evaporate rapidly as soon as the painted wire enters the oven, so that the lacquer resin quickly forms a “jelly”, which prevents the inner layer solvent from continuing to migrate outward. A large amount of solvent is forced to evaporate or boil after entering the high temperature zone with the progress of the wire, which destroys the continuity of the surface paint film and causes quality problems such as pinholes and bubbles in the paint film.