Talking about conductor oxidation and preventive measures in the production of rubber sheathed cable

General rubber sheathed cable is a 5 class copper conductor as a conductive core, in its production process, copper conductor oxidation and discoloration are often found, which seriously affects the quality of the product, has become a difficult technical problem
for many domestic cable manufacturers.

Copper is a transition metal that 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 large amount 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, which can form an electrolyte, 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 the waste
of production costs.
Therefore, copper conductors must be properly kept, pay attention to prevent oxidation and discoloration
.

In principle, the metal copper for cables mainly has physical methods to block the contact between copper and humid air, cathodic protection redox method to prevent copper conductor oxidation, chemical method to form a passivation film on the surface of copper conductor to prevent oxidation, or spray special liquid on the surface of the conductor for protection
.
Taking the production of general-purpose rubber sheathed cable as an example, the main method
of anti-oxidation control in each process.

1.
Transportation, testing and storage of copper rods before entering the factory

Most of China's cable enterprises use copper for purchase, should choose high-quality metal copper rod, standardize supplier transportation, delivery process and system, copper rod inspection in accordance with GB/T 3048.
2 or cable enterprise standard implementation
.
The storage of copper rods can be covered with plastic sheeting or plastic film, i.
e.
the simplest physical barrier method prevents the copper rod from coming into contact
with moist air.
When the workshop uses copper rods, it is necessary to visually check whether there is blackening phenomenon by the naked eye one by one copper rod rolls, and control
them from the source of production.

2.
Control of copper rod wire drawing process

The drawing of 0.
4mm monofilament generally adopts continuous annealing copper large drawing machine and medium pulling machine, which needs to go through the processes of paying, wire drawing and annealing, cooling, drying and winding
.
First of all, a suitable mold should be selected, which must not be too small, otherwise it will force the lattice variation of metal copper and aggravate the sharp rise
of metal temperature.
Secondly, check the pH of the emulsion before start-up to ensure that it is an alkaline solution, and antioxidants should be added to the drawing oil to form a passivation film on the surface of the copper conductor to prevent oxidation; When unwinding, keep the pay-off tension stable and uniform, and do not flutter excessively; During the wire drawing process, the operator should ensure the appropriate water level height to ensure a uniform annealing degree and avoid insufficient annealing or excessive annealing; When winding the wire, 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 (replaced frequently) to ensure the drying
of the monofilament.
Finally, after drawing, the disc is sealed with a transparent plastic film and stored in a dry environment for circulation, otherwise it will easily oxidize with the humid air due to the high surface temperature of the conductor
.

3.
Copper wire stranding (bundle stranding) and insulating rubber and sheath rubber extrusion process

Taking copper wire stranding as an example, the conductor in the stranding process, through each pressing mold to make the metal copper lattice change the structure, under the action of strong external force, the temperature of the copper conductor after the mold is greatly increased compared with before the mold, so the outer layer of the copper conductor is easy to oxidize
.
Therefore, the antioxidant (0.
3% benzotriazole alcohol solution) can be dropped into the copper wire with an infusion hose during the twisting process, and the drop standard is based on just infiltrating the surface of the copper wire to avoid too little local oxidation or too much waste, and then start the machine after all the
anti-oxidation work is prepared safely.
The take-up should ensure that the take-up reel is dry, and after the take-up reel is full, it is sealed
with a transparent plastic film.

Before the conductor is squeezed for insulation, the polyester tape should be longitudinally wrapped or wrapped, and the material in the rubber insulation material should be placed to corrode the conductor
.
During the extrusion process, the insulating rubber and sheathed rubber should avoid water entering the thread, and the oxidation and blackening phenomenon
of the wire end occurs.

In our daily production observation, we found that by selecting high-quality copper rods, effectively controlling the wire drawing process and emulsion concentration and temperature, annealing process, conductor stranding or passivation treatment of the surface of stranded copper wire and preventing water ingress at the end of the wire, etc.
, in addition, workshop operators should establish quality awareness, strengthen business training, can clearly understand the adverse consequences of copper wire oxidation, strictly control the quality, in order to effectively control the quality of cable copper conductors, prevent their oxidation, greatly improve work efficiency, reduce the frequency of rework, This has the beneficial effect
of reducing costs and improving intrinsic product quality.