The general rubber sheathed cable uses Category 5 copper conductors as the conductive cores. During the production process, the copper conductors are often found to be oxidized and discolored, which seriously affects the quality of the products and has become a long-standing 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 there is a water film or water droplets on the surface of the copper conductor, because the atmosphere contains a lot of dust, such as smoke, coal, automobile exhaust, chloride and other acid, alkali, salt particle dust, etc., these harmful substances are dissolved in the water film or water droplets. In the process, an electrolyte can be formed, thereby aggravating the oxidative discoloration of the copper conductor. The light ones affect the appearance quality and product quality of the products, and the heavy ones affect the use of copper conductors, resulting in waste of production costs. Therefore, copper conductors must be kept properly, and attention should be paid to preventing oxidation and discoloration.
In principle, metal copper for cables mainly includes physical methods to prevent copper from contacting with moist air, cathodic protection redox method to prevent oxidation of copper conductors, chemical methods to form a passivation film on the surface of copper conductors to prevent oxidation, or spray special liquid on the surface of conductors to prevent oxidation. Protect. Taking the production of general rubber sheathed cables as an example, the main methods of anti-oxidation control in each process.
1. Transportation, testing and storage of copper rods before entering the factory
Most cable companies use copper for outsourcing, and should choose high-quality metal copper rods to standardize the supplier’s transportation and delivery processes and systems. The copper rod can be stored by covering the copper rod with plastic cloth or plastic film, that is, the simplest physical barrier method to prevent the copper rod from contacting with moist air. When receiving copper rods in the workshop, it is necessary to visually check whether there is any blackening phenomenon one by one, and control them from the source of production.
2. Control of copper rod drawing process
The drawing of 0.4mm monofilament generally adopts continuous annealing copper large drawing machine and middle drawing machine, which needs to go through the processes of pay-off, wire drawing and annealing, cooling, drying, and wire take-up. First of all, a suitable mold should be selected, and it must not be too small, otherwise the lattice of the metal copper will be forced to mutate, which will aggravate the sharp rise of the metal temperature. Secondly, check the pH of the emulsion before starting 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 paying off, keep the pay-off tension stable and uniform. Excessive vibration; during the wire drawing process, the operator should ensure the proper water level to ensure uniform annealing, and avoid insufficient or excessive annealing; when taking up the wire, there should be no residual liquid on the surface of the copper conductor, and a piece of dry felt can be placed in front of the wire take-up (replace frequently) to keep the monofilament dry. Finally, after drawing the bottom plate, it is sealed with a transparent plastic film, and stored in a dry environment until it is circulated, otherwise there will be a risk of oxidation with the humid air due to the high temperature of the conductor surface.
3. Copper wire stranding (strand stranding) and extrusion process of insulating rubber and sheath rubber
Taking copper wire twisting as an example, during the twisting process of the conductor, the metal copper lattice changes its structure through various compression dies. The outer layer of the copper conductor is easily oxidized. Therefore, the antioxidant (0.3% benzotriazole alcohol solution) can be dripped into the copper wire with the infusion hose during the twisting process. Oxidation or excessive waste occurs. After all anti-oxidation work is properly prepared, start the machine again. Make sure that the take-up reel is dry at the take-up location, and after the take-up reel is full, seal it with a transparent plastic film.
Before the conductor is extruded and insulated, the polyester tape should be longitudinally wrapped or wrapped, and the substances in the rubber insulating material should be placed to corrode the conductor. During the extrusion process of insulating rubber and sheath rubber, water should be prevented from entering the thread, which may cause the thread to oxidize and turn black.
Through the observation of daily production, we found that by selecting high-quality copper rods, effectively controlling the wire drawing process and the concentration and temperature of the emulsion, annealing process, passivation treatment of the conductor stranded or bundled copper wire surface, and preventing the wire head from entering water and other means , In addition, workshop operators should establish quality awareness, strengthen business training, clearly recognize the adverse consequences of copper wire oxidation, and strictly control the quality, in order to effectively control the quality of cable copper conductors, prevent their oxidation, and greatly Improve work efficiency and reduce the frequency of rework, so as to achieve the beneficial effects of reducing costs and improving internal product quality.