Guide reading: Copper tape is a very common metal components, often in electrical components, lamp, battery Cap, buttons, Seals, connectors and other places to see, the main role is conductive, thermal, corrosion-resistant equipment. There are six areas in copper strip production, they are furnace area, laboratory, cutting area, hot rolling area, water washing area and rolling plate area. Below, small series and we talk about copper production process, production methods of cold rolling and hot rolling characteristics of some common problems, such as the problem of discoloration and shear indentation, we look at it together!

1.Production process of copper strip

(1) PREFORM: In accordance with the target of production, different amounts of zinc are added to the waste copper materials to make copper materials of different specifications.

(2)Assay: In order to ensure the production of both qualified and economic benefits of the finished product, the accuracy of the assay results is particularly important. The duty of the laboratory is to inform the smelter of the test results quickly and accurately according to the copper block.

(3)CUTTING: the complete copper strip is drawn by the hanging rope, placed on the special cutting table smoothly, cut by the cutting wheel saw, and then polished and smoothed by the copper strip washing machine, this is conducive to post-processing out of the copper strip surface smoothness and smoothness.

(4) Hot Rolling: THE CUT Copper Strip is heated at 1000 °C, then over-hot rolled and pressed into 2.3 cm thick copper strip.

(5) washing: each copper block after the first rolling step, because the surface impurities exist, in order to avoid affecting the quality of the finished product, must be again through the closed furnace again through the washing process. The washing area is divided into two pools according to their acidity. The high concentration was 6.8 °C, while the low concentration was 3.5 °C. The red spots on the surface of copper bar and copper strip can be washed away by the acid in the water washing tank, while the dark red spots are removed by the iron fine brush during the water washing, to give a distinct shine to the copper itself. The same rolling plate during the red spots and red spots still need to re-wash steps. Regularly check the acidity of the pool during washing, add acid in time to avoid too low acid content resulting in insufficient washing.

(6)Rolling Plate: The Rolling Plate area is divided into 180 primary rolling and 110 intermediate rolling according to the roller area. According to the different sizes of the rollers, the hot rolled copper strip, which has been forged in a closed furnace, is processed from rough to fine by the above two steps.

2.Features of copper strip production method

1. Cold rolled copper strip

(1) plastic deformation. 

(2) the pressure in the gap area is high, and there is pressure distribution, the maximum is 2700MPA. 

(3) there is friction along the rolling direction and in the reverse rolling direction. 

(4) the instantaneous temperature of roll gap is high, which can reach 200 ~ 300 °C. (5) co-existence of rolling and sliding states.

2. Copper Strip hot rolled

ADVANTAGES OF COPPER STRIP HOT ROLLING

1) hot rolling can significantly reduce energy consumption and cost. The metal has high plasticity and low deformation resistance during hot rolling, so the energy consumption of hot rolling is greatly reduced. 

(2) hot rolling can improve the processing properties of metals and alloys, that is, crushing the coarse grains in the casting state, significantly healing the cracks, reducing or eliminating the casting defects, transforming the as-cast structure into deformed structure, and improving the processing properties of the alloys. 

(3) the hot rolling usually uses the big INGOT and the big reduction rolling, not only has improved the production efficiency, but also has created the condition for increasing the rolling speed and realizing the rolling process continuity and the automation.

3.Defects of Copper Strip hot rolling

(1) after hot rolling, non-metallic inclusions (mainly sulfides and oxides, as well as silicates) inside the metal are compressed into thin sheets and delaminated. Delamination deteriorates the tensile properties of the metal along the thickness direction and May Cause Interlaminar tearing when the weld contract. The local strain induced by weld shrinkage often reaches several times of the yield point strain, which is much larger than that induced by load. 

(2) residual stress due to uneven cooling. The residual stress is a kind of self-balanced stress without external force, which is found in all kinds of hot-rolled steel sections. Although the residual stress is self-equilibrium, it still has some influence on the performance 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 precisely controlled, and the microstructure and properties of hot rolled products can not be uniform. The strength index is lower than that of the cold-cured products, but higher than that of the completely annealed products, and the plasticity index is higher than that of the cold-cured products. 

(4) it is difficult to control the thickness and size of hot rolled products, and the Ra value of the surface of hot rolled products is generally 0.5 ~ 1.5 m. Therefore, hot-rolled products are generally used as cold-rolled blanks.

4.olution to common problems of copper strip

1. Solution to discoloration of copper strip

(1) control the concentration of acid solution during pickling. When the oxide layer on the surface of annealed copper strip is washed off, the higher acid concentration does not make any sense. On the contrary, the high concentration of residual acid on the surface of the copper strip makes it difficult to wash off, and accelerates the pollution of the cleaning water, which results in the high concentration of residual acid in the cleaning water and the discoloration of the copper strip. Therefore, when determining the concentration of the pickling solution, the principle should be followed: on the premise that the oxide layer on the surface of the copper strip can be cleaned off, the concentration should be reduced as far as possible. 

(2) control the electrical conductivity of pure water. Control the electrical conductivity of pure water, that is, control the content of chlorine ion and other harmful substances in pure water. It is safe to control the conductivity below 50 S/CM.

 (3) control the electrical conductivity of hot cleaning water and passivator. The increase of conductivity of hot cleaning water and passivator mainly comes from the residual acid brought in by the running copper strip. Therefore, under the condition of ensuring the quality of pure water, the residual acid content can be controlled by controlling the electrical conductivity. According to many experiments, it is safe to control the conductivity of hot-cleaning water and passivator below 200 S/CM.

 (4) ensure the copper strip is dry. In order to control the temperature and humidity of the coil in a certain range, a dehumidifier and an air conditioner are used in the local closed device.

(5) passivation with a passivator. Most copper processing plants now use Benzotriazole, or BTA (molecular formula: C6H5N3) , as a passivator. Practice has proved that it is 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 protects the copper matrix.

2. Solution of Copper Strip shearing indentation

To prevent cutting edge indentation, mainly according to the thickness of the Strip, soft and hard degree to choose a reasonable round knife and rubber peel ring outside diameter difference, rubber peel ring hardness to meet the use of cut strip requirements; When cutting the width of the strip smaller, should be reasonable selection of the thickness of the circular knife, increase the width of the rubber peel ring. 

Source: Tongxin Tongde

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