Copper strip production technology, production method characteristics and solutions to common problems
Copper strip is a very common metal component. It is often seen in electrical components, lamp holders, battery caps, buttons, seals, connectors, etc. Its main function is to conduct electricity, heat, corrosion resistance, etc. There are six areas in copper strip production, namely the furnace area, laboratory, cutting area, hot rolling area, water washing area and plate rolling area. The production process of copper strips: 1. Preparation: According to the predetermined production target, different amounts of zinc blocks are added to the scrap copper material to produce copper raw materials of different specifications. 2. Laboratory testing: In order to ensure the production of finished products that are both qualified and economically beneficial, the accuracy of laboratory testing results is extremely important. The responsibility of the laboratory is to quickly and accurately report the test results to the furnace master based on the copper blocks submitted for inspection. 3. Cutting: The complete copper bar is pulled by a hanging rope, placed stably on a special cutting table, and then cut by a cutting wheel saw. The uneven surface of the copper bar is then smoothed by a copper bar washing machine, which is beneficial to later processing. The flatness and smoothness of the copper strip surface. 4. Hot rolling: The cut copper strip is heated at a high temperature of 1000°C, then hot rolled, and rolled into a copper strip with a thickness of about 2.3cm. 5. Water washing: After each copper block has been rolled, due to the presence of surface impurities, in order to avoid affecting the quality of the finished product, it must go through the sealing furnace again and then go through the water washing process. The water washing area is divided into two types of pools according to the acidity. The high concentration is 6-8 degrees, and the low concentration is 3-5 degrees. Among them, the medium red patches on the surface of copper rods and copper strips can be washed away by the acid in the washing tank, while the dark red patches can be removed by brushing with fine iron hair during washing. The copper strips after this series of treatments are obviously The ground shines with the inherent luster of copper. Similarly, if there are still red patches and red patches during the rolling process, the water washing step still needs to be repeated. During the washing period, the acidity in the pool should be checked regularly and acid should be added in time to avoid insufficient washing due to low acid content. 6. Plate rolling: The plate rolling area is divided into 180 preliminary rolling and 110 intermediate rolling according to the roller area. According to the different sizes of various rollers, the hot-rolled copper strips that have been forged in the sealing furnace are processed from rough to fine through the above two steps. Characteristics of the copper strip production method: 1. Cold rolling of copper strip (1) Plastic deformation. (2) The pressure in the roll gap area is high and there is pressure distribution, which can reach a maximum of 2700MPa. (3) There are friction forces along the rolling direction and the opposite rolling direction at the same time. (4) The instantaneous temperature of the roll gap is high, reaching 200~300℃. (5) Scrolling and sliding states coexist. 2. Hot rolling of copper strip Advantages of hot rolling of copper strip: (1) Hot rolling can significantly reduce energy consumption and reduce costs. During hot rolling, the metal has high plasticity and low deformation resistance, which greatly reduces the energy consumption of hot rolling during metal deformation. (2) Hot rolling can improve the processing performance of metals and alloys, that is, break the coarse grains in the casting state, significantly heal cracks, reduce or eliminate casting defects, transform the as-cast structure into a deformed structure, and improve the processing performance of the alloy. (3) Hot rolling usually uses large ingots and large rolling reductions, which not only improves production efficiency, but also creates conditions for increasing the rolling speed and realizing the continuity and automation of the rolling process. Disadvantages of hot rolling of copper strips: (1) After hot rolling, non-metallic inclusions (mainly sulfides, oxides, and silicates) inside the metal are pressed into thin sheets, resulting in delamination (interlayering). Delamination greatly deteriorates the tensile properties of the metal along the thickness direction and may cause interlaminar tearing as the weld shrinks. The local strain induced by weld shrinkage often reaches several times the yield point strain, which is much larger than the strain caused by load. (2) Residual stress caused by uneven cooling. Residual stress is the internal self-balanced stress in the absence of external force. Hot-rolled steel sections of various sections have such residual stress. Generally, the larger the cross-section size of the section steel, the greater the residual stress. Although residual stress is self-balanced, it still has a certain impact on the performance of metal under the action of external forces. For example, it may have adverse effects on deformation, stability, fatigue resistance, etc. (3) Hot rolling cannot control the required mechanical properties of the product very accurately, and the structure and properties of hot-rolled products cannot be uniform. Its strength index is lower than cold work hardened products, but higher than fully annealed products; its plasticity index is higher than cold work hardened products, but lower than fully annealed products. (4) The thickness and size of hot-rolled products are difficult to control, and the control accuracy is relatively poor; the surface of hot-rolled products is rougher than that of cold-rolled products, and the Ra value is generally 0.5 to 1.5 μm. Therefore, hot rolled products are generally used as blanks for cold rolling processing. Solutions to common problems with copper strips: 1. Solutions to discoloration of copper strips (1) Control the concentration of acid during pickling. In the case of washing away the oxide layer on the surface of the annealed copper strip, a high acid concentration does not make any sense. On the contrary, if the concentration is too high, the residual acid attached to the surface of the copper strip is not easy to wash off, and it accelerates the pollution of the cleaning water, causing the concentration of residual acid in the cleaning water to be too high, making the cleaned copper strip more likely to change color. Therefore, when determining the concentration of the pickling solution, the following principle should be followed: on the premise that the oxide layer on the surface of the copper strip can be cleaned, the concentration should be reduced as much as possible. (2) Control the conductivity of pure water. Control the conductivity of pure water, that is, control the content of harmful substances such as chloride ions in pure water. Generally, it is safer to control the conductivity below 50μS/cm. (3) Control the conductivity of hot cleaning water and passivation agent. The increase in conductivity of hot cleaning water and passivation agent mainly comes from the residual acid brought in by the running copper strip. Therefore, while ensuring the quality of pure water for cleaning, controlling the conductivity means controlling the amount of residual acid. According to many experiments, it is safe to control the conductivity of hot cleaning water and passivation agent below 200 μS/cm respectively. (4) Ensure the copper strip is dry. Partially seal the coiling outlet of the air cushion furnace, and use a dehumidifier and air conditioner in the partially enclosed device to control the humidity and temperature during copper strip coiling within a certain range. (5) Use passivation agent to passivate. Most copper processing plants now use benzotriazole, or BTA (molecular formula: C6H5N3) as a passivating agent. Practice has proved that it is an easy to use, economical and practical passivation agent. When the copper strip passes through the BTA solution, the oxide film on the surface reacts with the BTA to form a dense complex, which protects the copper matrix. 2. The solution to the shear indentation of the copper strip is to prevent the shearing indentation. It is mainly necessary to select a reasonable round knife and the outer diameter difference of the rubber peeling ring according to the thickness, softness and hardness of the strip; the hardness of the rubber peeling ring meets Requirements for the use of the cut strip; when the width of the cut strip is small, the thickness of the circular knife should be reasonably selected to increase the width of the rubber peeling ring.
