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Metal Copper atomic number 29, density is 8.92g/cm3, melting point 1083.4 ℃, with good heat conduction and conductive properties, but in humid air copper surface and oxygen chemical reaction, generate CU2 (OH) 2co3, namely patina, usually in cable production plant copper oxide more display surface blackening, It is this kind of cable copper conductor surface oxidation phenomenon exists, which puzzles many cable enterprises.
In our daily production observation and extensive data research, we found that through selection of high quality copper rods, effective control of wire drawing process and emulsion concentration and temperature, passivation treatment of copper conductor stranded or strand copper wire surface, and subsequent process optimization treatment, the quality of cable copper conductor will be effectively controlled and the oxidation will be greatly improved, Reduce rework frequency, so as to reduce costs and improve the intrinsic product quality beneficial effects. In this paper, Guangdong Zhujiang Wire and cable production as an example, from the copper rods arrived at the production plant, storage, drawing, stranding, the core storage to the insulation extrusion, the effective control measures for each step analysis.
Cable copper conductor
Anti-oxidation control of copper conductor in the process of wire and cable production
Metal copper for cable from the principle of the main physical methods of blocking copper and moist air contact, cathodic protection Oxidation reduction method to prevent copper conductor oxidation, chemical methods on the copper conductor surface production of passivation film to prevent oxidation, or on the conductor surface spraying special liquid to protect. The main method of preventing oxidation control in each procedure is taking the production of Zhujiang wire and cable in Guangdong as an example.
1.1 Copper rod before entering the factory transportation, inspection and storage
Most of China's cable enterprises with copper basic outsourcing, and most enterprises often ignore the copper rod into the plant before the transport process Control, in the south and the coastal zone (Jiangsu, Zhejiang, Fujian and Guangdong) in the summer longer and more rain, copper rods through heavy truck transport to the company, through the author understand that many cable enterprises do not have a corresponding copper rod supplier transport norms, Summer Rainy day packaging system, which makes the copper rod suppliers often appear when the copper rod surface is intact without oxidation black, and to reach the cable business users in front of the copper rod surface blackening phenomenon, brought unnecessary trouble.
Copper rod into the factory inspection in accordance with GB/T 3953-2009 or cable enterprises, there are strict procedures. Copper rod storage General cable enterprises are placed in the warehouse, General enterprises have a more stringent storage management methods, in the copper rod storage, especially in summer rainy days, must be covered with plastic sheeting or plastics film, copper rods, with the simplest physical blocking method to prevent the copper rod and moist air contact system, and this is often the cable enterprises ignored. In the workshop with copper rods must be a copper rod coil for the naked eye check whether there is blackening phenomenon, from the source of production control.
1.2 Copper rod drawing Process Control
In this stage, the most commonly used power cable 8mm copper Rods For example, today, the general use of wire drawing in the continuous annealing copper pull, need to go through the line, drawing and annealing, cooling, drying, line and other processes, the preferred choice of the corresponding specifications of the mold, must not be too small, such as too small will force the crystal lattice variation of metal to increase the sharp increase in metal temperature.
Check the concentration of the emulsion before booting, to ensure that the concentration of the line, in the process, should keep the line tension steady, uniform, not excessive vibration (vibration inevitable), the process of drawing the operator should pay close attention to the changes in annealing temperature, drawing after the conductor hardening, elongation, the conductor DC resistivity rise, Drawing waiting into the ring when the copper conductor surface should not have residual emulsion, where the operator needs to identify the naked eye, in the drawing of transparent plastic film sealed, stored in a dry environment, to be circulated, but most cable enterprises because the copper wire bag film trouble and omit the film process. The surface temperature of the conductor, which is just drawn into a circle, is higher than room temperature, such as the potential oxidation during the rainy season.
1.3 Copper wire stranding (twisted) and chemical crosslinking extrusion process
Taking copper wire as an example, in the process of conductor stranding, each monofilament is twisted by regular or irregular twist, after each road die, the copper conductor temperature is higher than before the die, especially the tight pressure conductor, sector conductor, and there is no online annealing or cooling device, so the copper conductor outer layer is easy to oxidize, Before the stranding, select the appropriate clamping die, tight wheel, wire, adjust the line and line tension, equipment adjusted, the operator to observe the upper plate copper wire and put the center of the wire frame of the surface finish, to ensure that no obvious black spots, and then start the machine.
General Cable enterprises in the stranding process (box cutter, cage-stranded machine in the application of antioxidants, antioxidant formula is about 0.3% of benzene and triazole alcohol solution, the operation of the antioxidant into the industrial alcohol, with infusion hose drip into the copper wire, dripping into the standard to just infiltration of copper wire, whichever, Avoid too little local potential oxidation or excessive waste of the phenomenon occurs, in all the preparation of the oxidation prevention work, and then turn on the operation.
The receiving line should ensure that the reel is dry, after the line is full, with transparent plastic film seal, and copper wire drawing system, many cable enterprises also omitted this step, if this step caused by copper conductor oxidation, low voltage cable effect is still lower, for ultra-high voltage cable, the impact is unimaginable. After the copper conductor is brushed, twisted and stored, the crystal lattice form of copper is basically stable. Chemical crosslinking is the uniform extrusion of xlpe on copper conductor under the condition of crosslinking agent, antioxidant and coupling agent. Adjust the tension of the take-up line to ensure the smooth operation of the equipment before the release coil filled with copper conductor is started.
Almost all the cable factories in China are confronted with the oxidation of copper conductor, which is to maintain the reduction of metal copper from the chemical properties of copper. In the daily production, the use of Guangdong Zhujiang wire and cable as follows measures to reduce the probability of copper conductor oxidation:
1, select high quality metal copper rods, standardize supplier transport, delivery process and system, the copper rod to the company, take transparent plastic film sealing measures, copper conductor pull system, twisted after all should take transparent plastic film sealing measures;
2, the use of appropriate copper wire drawing process, regular inspection of the annealing parts of wire drawing machine, priority selection of drawing oil containing antioxidants, regular inspection of emulsion concentration, the expiration date must be replaced in advance;
3, copper wire stranded, extrusion insulation process using passivation treatment technology;
4, to establish quality awareness, strengthen business training for the above process operators to understand the adverse effects of copper wire oxidation.