How to prevent the oxidation of common rubber sheathed conductors

General purpose rubber sheathed cable is a type 5 copper conductor as the conductive core. In its production process, copper conductor is often found to be oxidized and discolored. This seriously affects the quality of the product and has become an old technical problem for many domestic cable manufacturers. .

Copper is a transition metal and is easily oxidized to black CuO by oxygen in the air under acidic conditions. When the surface of the copper conductor has water film or water droplets, the atmosphere contains a lot of dust, such as smoke, coal, automobile exhaust, chlorides and other acids, alkalis, salt particles, dust, etc. These harmful substances are dissolved in water film or water droplets. In the electrolyte can be formed, thereby accelerating the oxidation of copper conductor discoloration. The light affects the appearance of the product and the quality of the product. In severe cases, the use of the copper conductor is affected, resulting in a waste of production costs. Therefore, the copper conductor must be properly stored, pay attention to oxidation and discoloration.

The principle of copper metal used for cables is that there are physical methods for blocking copper from contact with humid air, cathodic protection with redox to prevent oxidation of copper conductors, chemical methods to form passive films on the surface of copper conductors to prevent oxidation, or spraying special liquids on conductor surfaces. protection. Take the production of general rubber cable as an example, the main method of preventing oxidation in each process.

1, copper rod into the factory before transport, testing and storage

Most of the cable companies in China use copper for outsourcing. They should select high quality metal copper rods, standardize suppliers' transportation and delivery procedures and systems, and copper rods entering the factory to be inspected in accordance with GB/T 3048.2 or cable companies' corporate standards. The storage of the copper rods can be covered with a plastic or plastic film, ie the simplest physical barrier prevents the copper rods from coming into contact with moist air. When the workshop uses copper rods, it is necessary to visually inspect the copper rods one by one to see if they are blackened, and to control them from the source of production.

2, copper wire drawing process control

The drawing of 0.4mm monofilament generally adopts copper annealing machine and medium tension machine which are continuously annealed. It needs to go through the processes of wire drawing, drawing and annealing, cooling, drying, and take-up. First of all, you should select a suitable mold, must not be too small, otherwise it will force the variation of the crystal lattice of copper, and aggravate the rapid rise of metal temperature.

Secondly, check the pH of the emulsion before turning on the machine to ensure that it is an alkaline solution. At the same time, antioxidants should be added to the drawing oil to form a passivation film on the surface of the copper conductor to prevent oxidation. When the wire is released, the tension of the payoff line should be stable and uniform. Excessive tremors; Operators should ensure proper water level during wire drawing, ensure uniform annealing, avoid under-annealing or over-annealing; at the time of take-up, there should be no residual liquid on the surface of the copper conductor, and a dry felt can be placed in front of the take-up line. (Replace frequently) to ensure monofilament drying.

Finally, after the drawing, it is sealed with a transparent plastic film and stored in a dry environment until it flows. Otherwise, the risk of oxidation due to the high surface temperature of the conductor and the humid air will occur.

3, copper wire stranding (bundle) and insulating rubber, sheath rubber extrusion process

For example, in the twisting of copper wire, during the twisting process of the conductor, the copper copper crystal lattice changes its structure after passing through various channels. Under the action of a strong external force, the temperature of the copper conductor after the over-molding is greatly improved compared with that before the overmolding. The outer conductor of the copper conductor is susceptible to oxidation. Therefore, the antioxidant (0.3% benzotriazole alcohol solution) can be dripped into the copper wire using an infusion hose during the twisting process. The standard is to infiltrate the surface of the copper wire immediately. Oxidation or excessive waste occurs. After all oxidation protection work is ready, turn it on again. The take-up line shall ensure that the take-up spool is dry. After the take-up reel is full, seal it with a transparent plastic film.

The polyester tape shall be wrapped or wrapped around the conductor before the insulation is extruded, and the material in the rubber insulation shall be placed to corrode the conductor. During the extrusion process, the insulating rubber and sheath rubber should prevent the thread from entering the water, and the oxidation of the thread ends can occur.

In our daily production observations, we found that by selecting high-quality copper rods, effectively controlling the drawing process and the emulsion concentration and temperature, annealing process, passivation treatment of conductor strands or bundles of twisted copper wires, and prevention of water ingress of threads In addition, the workshop operators should establish a sense of quality, strengthen business training, be able to clearly recognize the adverse consequences of oxidation of copper wire, and strictly control quality in order to effectively control the quality of cable copper conductors and prevent their oxidation. Improve the work efficiency, reduce the frequency of rework, so as to achieve the beneficial effect of reducing costs and improving the quality of internal products.

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