Copper strip is a very common metal component, which is often seen in electrical components, lamp caps, battery caps, buttons, seals, connectors and other places. Its main function is to conduct electricity, conduct heat, and corrosion-resistant equipment. There are six areas for copper strip production, namely furnace area, laboratory, cutting area, hot rolling area, washing area and plate rolling area. Now, let's talk about the production process of copper strip, the characteristics of cold rolling and hot rolling in the production method, and the solutions to some common problems, such as discoloration and shear indentation. Let's have a look!

The production process of copper strip is as follows

1. Embryo making: according to the predetermined production target, different amounts of zinc blocks are added into the waste copper material to make different specifications of copper raw materials.

2. Test: in order to ensure the production of both qualified and economic benefits of finished products, the accuracy of test results is still important. The responsibility of the laboratory is to quickly and accurately report the test results to the furnace master according to the copper block submitted for inspection.

3. Cutting: the complete copper strip is pulled by the lifting rope and placed stably on the special cutting table. Then it is cut by the cutting wheel saw, and the uneven surface of the copper strip is polished smooth by the copper strip washing machine, which is conducive to the flatness and smoothness of the later processed copper strip surface.

4. Hot rolling: the cut copper strip is heated at 1000 ℃ and then hot rolled into a copper strip with a thickness of about 2.3cm.

5. Water washing: each copper block after the blooming step, due to the existence of surface impurities, in order to avoid affecting the quality of the finished product, it must go through the sealing furnace again and then the water washing process. The water washing area is divided into two kinds of pools according to the acidity. The high concentration is 6-8 degrees, and the low concentration is 3-5 degrees. The medium red patches on the surface of copper rod and strip can be washed away by the acid in the washing pool, while the dark red patches can be removed by the iron fine brush during the washing period. After a series of treatment, the copper strip obviously shines out the inherent luster of copper. In the same way, if there are still red patches and red patches during the rolling process, the washing process should be repeated. During water washing, the acidity in the pool should be checked regularly, and acid should be added in time to avoid insufficient water washing due to too low acid content.

6. Plate rolling: the plate rolling area is divided into 180 blooming and 110 intermediate rolling according to the roller. According to the different sizes of various rollers, the hot rolled copper strip which has been forged in the sealed furnace is processed from rough to fine through the above two steps.

Characteristics of copper strip production method:

1. Cold rolling of copper strip

(1) Plastic deformation.

(2) The pressure in roll gap area is high, and there is pressure distribution, and the maximum pressure can reach 2700mpa.

(3) At the same time, there is friction along the rolling direction and the opposite rolling direction.

(4) The instantaneous temperature of roll gap is high, up to 200 ~ 300 ℃.

(5) Rolling and sliding coexist.

2. Hot rolling of copper strip

Advantages of copper strip hot rolling

(1) Hot rolling can significantly reduce energy consumption and cost. During hot rolling, the metal has high plasticity and low deformation resistance, which greatly reduces the hot rolling energy consumption of metal deformation.

(2) Hot rolling can improve the processing properties of metals and alloys, that is, the coarse grains in the casting state are broken, the cracks are obviously healed, the casting defects are reduced or eliminated, the as cast structure is transformed into deformed structure, and the processing properties of alloys are improved.

(3) Hot rolling usually adopts large ingot and large reduction rolling, which not only improves production efficiency, but also creates conditions for improving rolling speed and realizing continuous and automatic rolling process.

Disadvantages of copper strip hot rolling:

(1) After hot rolling, the non-metallic inclusions (mainly sulfides and oxides, and silicates) inside the metal are pressed into thin sheets, resulting in delamination (sandwich) phenomenon. Delamination can deteriorate the tensile properties of the metal along the thickness direction, and interlaminar tearing may occur when the weld shrinks. The local strain induced by weld shrinkage is often several times of that at yield point, which is much larger than that caused by load.

(2) Residual stress caused by uneven cooling. The residual stress is the internal self balance stress without external force. All kinds of hot-rolled section steel have this kind of residual stress. The larger the section size of general section steel is, the larger the residual stress is. Although the residual stress is self-equilibrium, it has a certain influence on the properties of metal under external force. Such as deformation, stability, anti fatigue and other aspects may have adverse effects.

(3) The mechanical properties of hot-rolled products can not be controlled accurately, and the microstructure and properties of hot-rolled products can not be uniform. Its strength index is lower than that of cold work hardening products, but higher than that of fully annealed products; its plasticity index is higher than that of cold work hardening products, but lower than that of fully annealed products.

(4) The thickness of hot-rolled products is 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 ~ 1.5 μ M. Therefore, hot rolled products are usually used as cold rolled billets.

Solutions to common problems of copper strip:

1. Solution of copper strip discoloration

(1) Control the acid concentration during pickling. When the oxide layer on the surface of annealed copper strip is washed away, the high acid concentration is meaningless. 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 the pollution of the cleaning water is accelerated, resulting in the high concentration of residual acid in the cleaning water, which makes the copper strip easier to change color after cleaning. Therefore, when determining the concentration of pickling solution, the principle should be followed: on the premise that the oxide layer on the surface of copper strip can be cleaned, the concentration should be reduced as far as possible.

(2) Control the conductivity of pure water. Control the conductivity of pure water, that is, control the content of chlorine ion and other harmful substances in pure water. Generally, it is safe to control the conductivity below 50 μ s / cm.

(3) Control the conductivity of hot cleaning water and passivator. The increase of conductivity of hot cleaning water and passivation agent is mainly due to the residual acid brought by the running copper strip. Therefore, under the condition of ensuring the quality of pure water for cleaning, it is necessary to control the conductivity, that is, the amount of residual acid. According to many experiments, it is safe to control the conductivity of hot cleaning water and passivator below 200 μ s / cm respectively.

(4) Make sure the copper strip is dry. In order to control the humidity and temperature of copper strip coiling within a certain range, the air conditioner and dehumidifier are used in the local sealing device.

(5) Passivation with passivator. Now most copper processing plants use BTA (molecular formula: c6h5n3) as passivator. It is proved to be a convenient, economical and practical passivator. When the copper strip passes through BTA solution, the oxide film on the surface reacts with BTA to form a compact complex, which can protect the copper substrate.

2. Solution of copper strip shear indentation

In order to prevent the generation of cutting edge indentation, it is mainly necessary to select a reasonable outer diameter difference between the round knife and the rubber stripping ring according to the thickness and hardness of the strip; the hardness of the rubber stripping ring meets the use requirements of the cut strip; when the width of the cut strip is small, the thickness of the round knife should be reasonably selected to increase the width of the rubber stripping ring.