In the wire drawing process of my country's wire and cable industry, copper material and enameled wire industry, oxidation, discoloration and blackening are common, and it is more serious in spring and summer. With the popularization of existing high-speed machines, the drawing speed has been greatly improved, and the contradiction has become more and more prominent. For these problems and their relationships, I focus on the analysis of the temperature caused by the copper wire drawing process that affects oxidation lubrication and other issues: because the wire temperature and the friction between the wire and the mold directly affect the lubrication effect during the drawing process, the following Analyze the aspects: one is the fat content of the lubricating oil; the second is the stretching speed and the temperature of use; the third is the stretching force; the fourth is how to prevent oxidation and blackening.
1. Fat mass The grease content of the drawing oil produced by almost every manufacturer is different. The grease content, viscosity and use temperature of the drawing oil are the main reasons that affect the lubricating effect. Let's analyze them separately:
The so-called fat mass can be simply understood as the thickness of the oil film formed in the deformation zone during the drawing process. If the fat content of the drawing emulsion is too high, the oil film formed in the deformation zone during the drawing process will be too thick, resulting in the following adverse conditions: A. The oil film is too thick, and the drawn copper wire loses its surface gloss B. Cause partial unevenness and incompleteness of the oil film, resulting in an increase in the direct contact area, increasing friction and causing oil spots on the surface of the drawn product. C. In addition, if the fat content of the emulsion is too high, a part of it will be released, causing the emulsion to stratify and adhere to the copper powder, suspend on the emulsion, stick to the mold hole, block the mold hole, and then break the wire. In severe cases, it will directly lead to the deterioration of the lubricating oil, resulting in the replacement of the whole pool and causing losses. If the fat content of the drawing fluid is too low, the oil film must be very thin, or a complete oil film cannot be formed. In the process of drawing, it is easy to cause cracks, resulting in that the stretched copper wire contacts the mold without lubrication, which increases the friction and causes undesirable conditions. 2. Temperature and stretching speed The use temperature and lubricating effect of the drawing oil are mutually influential. If the temperature is too low, the newly added drawing oil is not easy to emulsify, and the particle mobility of the emulsion will decrease, which is not conducive to lubrication. On the contrary, if the temperature is too high, the grease is easily decomposed and suspended on the emulsion, which reduces the lubricating effect. If the temperature of the emulsion rises further without taking effective measures to control its temperature, the oil film in the deformation zone may break, leading to the break of the chemical chain in the drawing oil process formula. As a result, the friction coefficient will inevitably increase greatly. Under the vicious circle, not only the surface quality of the product will decrease, but also the temperature of the emulsion will rise rapidly, leading to an increase in the rejection rate. Therefore, maintaining the cooling state of the high-speed drawing emulsion is not negligible. The temperature should be controlled below the breaking point of the oil film, and a cooling tower or heat exchanger should be used for temperature-regulating treatment. 3. Stretching force During the normal operation of the wire drawing, the higher the wire drawing speed, the easier it is to bring the emulsion into the die hole and increase the pressure of the lubricating fluid in the die. As a result, the thickness of the lubricating film is increased, thereby reducing the coefficient of friction. In the stretching process, the greater the load, the greater the pressure. As a result, the emulsion is easily squeezed out of the deformation zone, thereby reducing the thickness of the lubricating oil film, increasing the actual contact area, and increasing the friction coefficient. The influence of tensile force on the lubrication effect: The greater the tensile force, the greater the extreme pressure it produces when drawing wires of the same weight or length, and the more work it converts to heat. At this time, the temperature rise of the wire will increase. Therefore, the factors that affect the tensile force will increase the tensile force, such as deformation resistance, mold damage and continued stretching. The greater the tensile force, the greater the frictional force and the greater friction loss, which is transformed into heat energy, which causes the temperature of the wire surface to rise and the temperature of the emulsion oil to rise, which cannot be ignored. 4. How to prevent oxidation and blackening? There are many reasons for the blackening and oxidation of copper wires:
(1) The area of the wire drawing emulsified oil pool is small, the return pipe is short and sealed, which results in slow heat dissipation and high temperature of the emulsified oil.
(2) It is caused by copper wire annealing. Firstly, tap water and groundwater are generally used for cooling water for continuous cooling. Because the water quality varies from place to place, the PH value of water quality in some areas is low, only 5.5-5.0, and the anti-oxidant oil film in the original emulsion is washed away. , The annealed copper wire is easy to oxidize and turn black; the second is that the finished copper wire drawn on an ordinary wire drawing machine is annealed on another annealing line. The cooling water does not use antioxidants, and the antioxidant time is short, and it will appear soon Oxidation blackening phenomenon;
(3) Some old factories still use annealing cylinders for annealing, and the following reasons can also cause oxidation and blackening: one is that the annealing cylinder nut is not tightened, and the gas leaks after flushing carbon dioxide or high-purity nitrogen; second, the cylinder is discharged The temperature of the copper wire is too high, exceeding 30℃; third, the drawing emulsion is not maintained enough and the PH value is too low; these situations are more common when the temperature is high in summer, and the emulsion will be lost if the temperature is high. Faster, if the new crude oil is not replenished in time, the fat content is small at this time, and the temperature is high, the temperature of the emulsion may also exceed 45°C, which will easily cause oxidation and blackening.
(4) Another situation is that due to the current widespread use of high-speed wire drawing, the speed has increased, and the relative heat dissipation time is reduced, which brings a certain amount of space and time to oxidation. Therefore, it is recommended that manufacturers pay more attention to the fat content of the emulsion. Whether the conditions, temperature, pH value, etc. are appropriate, the bacteria multiply faster in the yellow mold rain season in spring, you can use bactericidal and anti-fungal agents, and antioxidants in summer, so it is not a problem to solve the problem of oxidation and blackening.
