Copper strip is a very common metal component, often found in electrical components, lamp holders, battery caps, buttons, seals, connectors, and other applications. Its primary functions include electrical and thermal conductivity, as well as corrosion resistance. Copper strip production involves six areas: the furnace, laboratory, cutting area, hot rolling area, water washing area, and plate rolling area. Below, we will discuss the copper strip production process, the characteristics of cold and hot rolling, and solutions to common problems, such as discoloration and shear marks. Let's take a look!
Copper Strip Production Process:
1. Blank Making: Based on predetermined production targets, varying amounts of zinc ingots are added to scrap copper to produce copper raw materials of varying specifications.
2. Testing: To ensure both qualified and cost-effective finished products, accurate testing results are crucial. The laboratory's responsibility is to quickly and accurately communicate the test results to the furnace operators based on the copper ingots submitted for testing. 3. Cutting: The whole copper bar is pulled by a rope and placed steadily on a dedicated cutting table. It is then cut with a cutting wheel saw. A copper bar scrubber smoothes any uneven surfaces, which facilitates the flatness and smoothness of the resulting copper strip.
4. Hot Rolling: The cut copper bars are heated to 1000°C and then hot rolled into copper strips approximately 2.3cm thick.
5. Washing: After the initial rolling process, each copper bar must pass through a sealing furnace and then undergo a water washing process to prevent surface impurities from affecting the quality of the finished product. The washing area is divided into two water tanks based on the acidity: a high concentration of 6-8°C and a low concentration of 3-5°C. Medium-red spots on the copper bars and strips can be removed with acid in the washing tank, while dark red spots are removed with a fine-bristled iron brush during the washing process. After this series of treatments, the copper strips exhibit a distinct, inherent copper luster. If red spots and red spots still exist during the rolling process, the water washing step needs to be repeated. During the water washing process, the acidity in the water pool should be checked regularly and acid should be added in time to avoid insufficient water washing due to low acid content.
6. Plate rolling: The plate rolling area is divided into 180 initial rolling and 110 intermediate rolling according to the roller area. According to the different sizes of various rollers, the copper strips that have been hot-rolled and forged in the sealing furnace are processed from rough to fine through the above two steps.
Features of the copper strip production method:
1. Copper strip cold rolling
(1) Plastic deformation.
(2) The pressure in the roll gap area is high and there is a pressure distribution, which can reach up to 2700MPa.
(3) Friction exists in both the rolling direction and the anti-rolling direction.
(4) The instantaneous temperature of the roll gap is high, which can reach 200-300℃.
(5) Rolling 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 for metal deformation.
(2) Hot rolling can improve the processing performance of metals and alloys, that is, it can crush the coarse grains in the cast state, significantly heal cracks, reduce or eliminate casting defects, transform the cast structure into a deformed structure, and improve the processing performance of the alloy.
(3) Hot rolling usually uses large ingots and large reductions, which not only improves production efficiency, but also creates conditions for increasing rolling speed and realizing the continuity and automation of the rolling process.
Solutions to common problems of copper strip:
1. Solutions to discoloration of copper strip
(1) Control the concentration of the acid solution during pickling. When washing away the oxide layer on the surface of the annealed copper strip, a high acid concentration has no meaning. On the contrary, if the concentration is too high, the residual acid attached to the surface of the copper strip is difficult to wash off, and the pollution of the cleaning water is accelerated, resulting in an excessively high residual acid concentration in the cleaning water, which makes the copper strip more likely to change color after cleaning. Therefore, when determining the concentration of the pickling solution, the following principle should be followed: under the premise of being able to clean the oxide layer on the surface of the copper strip, its concentration should be reduced as much as possible.
(2) Control the conductivity of pure water. Controlling the conductivity of pure water means controlling 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 the conductivity of hot cleaning water and passivation agent mainly comes from the residual acid brought into the running copper strip. Therefore, while ensuring the quality of the pure water used for cleaning, controlling the conductivity means controlling the amount of residual acid. According to multiple experiments, it is safe to control the conductivity of hot cleaning water and passivation agent below 200μS/cm respectively.
(4) Ensure that the copper strip is dry. The coiling outlet of the air cushion furnace is partially sealed, and a dehumidifier and air conditioner are used in the partially sealed device to control the humidity and temperature of the copper strip during coiling within a certain range. (5) Use a passivating agent for passivation. Most copper processing plants now use benzotriazole, namely BTA (molecular formula: C6H5N3) as a passivating agent. Practice has proved that it is a convenient, economical and practical passivating agent. When the copper strip passes through the BTA solution, the oxide film on the surface reacts with BTA to form a dense complex, which plays a role in protecting the copper substrate.
2. Solution to shear indentation of copper strips To prevent the occurrence of shear blade indentations, it is mainly necessary to select a reasonable outer diameter difference between the circular knife and the rubber stripping ring based on the thickness and hardness of the strip; the hardness of the rubber stripping ring must meet the use requirements of the cut strip; when the width of the cut strip is small, the thickness of the circular knife should be reasonably selected and the width of the rubber stripping ring should be increased.
The company has a cluster of leading copper processing production lines in China, including:
German imported precision copper tube production line (annual output of 30,000 tons)
Japanese technology copper foil rolling line (thinnest up to 6μm)
Fully automatic copper bar continuous extrusion line
Intelligent copper sheet and strip finishing mill unit
Digitalized control and management of the whole production process is realized through MES system, and the dimensional accuracy of the products can reach ±0.01mm.
