In the process of copper wire drawing in China's cable industry, copper material and enamelled wire industry, oxidation discoloration and blackening are common, especially in spring and summer. With the popularization of the existing high-speed machine, the copper wire drawing speed has been greatly improved, and the contradiction is more and more prominent. The temperature of wire rod during copper wire drawing and the friction between copper wire and mold directly affect the lubrication effect, which can be analyzed from the following aspects: fat content of copper wire drawing oil, drawing speed and use temperature, copper drawing force, copper oxidation blackening.

1、 Fat content of copper wire drawing oil (commonly known as fat content)

The grease content of wire drawing oil produced by each manufacturer is different. (The type, specification and setting of wire drawing oil are different for large drawing, fine drawing and micro drawing, and high-speed drawing.) The grease content, viscosity and use temperature of copper wire drawing oil are the main factors affecting the lubrication effect. It is further analyzed as follows:

The so-called fat content can be simply understood as the thickness of the oil film formed in the deformation area during the copper wire drawing process. If the fat content of the copper wire drawing oil is too high (that is, excessive lubrication), the oil film formed in the deformation area during the wire drawing process will be too thick, and the following adverse conditions will occur:

A. The oil film is too thick, and the drawn copper wire loses its surface gloss

B. It causes uneven and incomplete oil film locally, leading to direct contact area, increasing friction and making the surface of the product pulled out with oil spots. (It is difficult to paint if enameled wire is to be produced later)

C. If the fat content of copper wire drawing oil is too high, some of it will be free, causing lotion to delaminate and adhere to the copper powder, suspending on the lotion, fouling the mold hole, blocking the mold hole, and then breaking the wire. If it is serious, it will directly lead to the deterioration of copper wire drawing oil, resulting in the replacement of the whole tank and loss.

If the fat content of wire drawing fluid is too low, the oil film must be very thin or cannot form a complete oil film. In the process of wire drawing, it is easy to cause cracks, so that the drawn copper wire can not play the role of lubrication when contacting with the mold, and the friction force is increased, resulting in the following adverse conditions:

A. Tensile force will lead to frequent wire breakage

B. Friction increases, heat is generated, oil temperature increases, and oil consumption increases

C. The surface quality of the drawn wire is reduced

D. Rapid loss of moulds and tower wheels and increase of copper powder

Therefore, when selecting copper wire drawing oil, we should determine the amount of fat content according to the wire diameter of the drawing specification (for example, for large wire drawing, the fat content of crude copper wire drawing oil is generally about 8-12%, for medium wire drawing, it is about 8-10%, for small wire drawing, it is about 5-6%, and for micro wire drawing, it is about 1.5-2.5%). The concentration of copper wire drawing oil is different from the fat content. Generally, the fat content of copper wire drawing oil is 70-80%, That is to say, the fat content in every 100kg of wire drawing oil is only 70-80kg, so when some users adjust the emulsified oil according to the concentration recommended in the user manual, they think that 10kg of oil plus 90kg of water is fat and has reached 10%. In fact, it is wrong. The actual fat content is 7-8kg, so it is necessary to use a saccharometer to detect the fat content. The method is as follows: at room temperature of 24 ℃, put 10ml of crude oil of drawing oil into a 100ml measuring cylinder with a plug, then add distilled water to the scale of 100ml, (that is, 10ml of drawing oil, then add 90ml of distilled water), tightly plug the measuring cylinder cover, shake it up and down about 20 times. After the filling is uniform, take the saccharometer, wash the mirror surface with clean water, wipe it with soft paper (or soft cloth), drop a few drops of lotion prepared evenly on the mirror surface, and wipe it off after cleaning once. Add 1-2 drops on the mirror of the saccharometer again, and observe it at the bright place. The obtained reading multiplied by 10 times is the fat content of this copper wire drawing oil.

2、 Temperature and tensile speed

The use temperature of copper wire drawing oil and the lubrication effect are mutually dependent. If the temperature is too low, the newly added wire drawing oil is not easy to emulsify, and the particle mobility of its lotion will decline, which is not conducive to lubrication. On the contrary, if the temperature is too high, the grease is easy to decompose and suspended on the lotion, which reduces the lubrication effect. If the temperature of the lotion rises further without taking measures to control its temperature, the oil film in the deformation zone may break, leading to the chemical chain break in the drawing oil process formula. In this way, the friction coefficient will inevitably increase greatly. Under the vicious cycle, not only the surface quality of the product will decline, but also the emulsion temperature will rise rapidly, leading to the increase of the scrap rate. Therefore, it cannot be ignored to keep the cooling state of copper wire drawing oil. The temperature shall be controlled below the oil film rupture point, and the cooling tower or heat exchanger shall be used for temperature stabilization.