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Analysis of copper wire turns black
Oct 25, 2017


The factors of cause copper wire turns black

  1. The area of the drawing emulsified oil pool is small, the reflux pipeline is short and sealed, resulting in the slow cooling and the high temperature of emulsion oil.

  2. Copper wire annealing causes.

        even pull even the return of cooling water is generally use tap water, groundwater, due to vary across the water, the PH of the water quality in some areas is low, only 5.5 ~ 5.0 (normal is 7.0 ~ 7.0), the original antioxidant oil in emulsion membrane cleaning off, after annealing of easy oxidation of copper wire, black;

       The copper wire of finished products is annealed on another annealing line. The cooling water also does not use the anti-oxidant, and the anti-oxygen time is short.

  3. Some old factories still use the annealing cylinder to reduce the fire, the following reasons can also cause oxidation and blackening:

       The annealing cylinder nut is not tightened and the leakage of carbon dioxide or high purity nitrogen is completed.

       a copper cylinder temperature is too high, more than 30 ℃;

       ③It is not maintained enough, the PH value is too low;

These more common when summer air temperature is high, the emulsion used constantly to loss, at high temperature is loss faster, if not timely supplement new oil, then very little fat content, coupled with high temperature, the temperature of the emulsion may exceed 45 ℃, it is easy to cause the black oxide.

  4. and another is that the current widespread use of high speed wire drawing, the speed increase, relatively reduce the cooling time, brings a certain space and time to the oxidation, therefore, suggest the manufacturers pay more attention to the emulsion of fat content, temperature, PH value of appropriateness, bacteria multiply faster yellow mould rains in spring season, can be used antiseptic fungicide, summer antioxidants are available, and solve the problem of oxidation, black is not a problem.

▎ reason

1. The deformation amount of finished die is too small.

2. The outside and front of the mould paneling are not sealed.

▎ solution

Add a rubber mat to the exit direction of the finished die, then screw the finished mould to solve the oil leakage problem.

Finished product mode of small deformation, is a common mistake, single-mode deformation should be a minimum of deformation, the pressure may be greater than the yield limit of the metal, can be realized is a plastic deformation, size stability, single surface will be drawn to produce light.


Cause the coil to be blackened

In life, we often use all sorts of use coil products, such as motor, horn, hearing AIDS, remote control toys, wireless charger, power switch, computer...... black because of the oxidation of copper wire coil, coil, the main material of basic copper and metal oxide, so we'll see the black wire coil.

   1. Technical reasons: in the past, most of my factories in China have used copper rods with universal applicability. The copper content can reach 99.95%, but even if this is the day, there is still this O in copper.The reason is that copper itself is not free of oxygen, and the copper surface is inevitably oxidized by contact with air during processing.Now the domestic introduction of oxygen-free copper advanced production technology, as well as domestic self-developed oxygen-free copper production technology, make whole oxygen-free copper copper industry are used, it has been greatly improved the problem of black copper wire.However, due to the processing of the copper rod, especially the application of the toughening process and the conditions of the finished copper wire storage, the copper wire itself will have a slight oxidation.

   2. Material problem of insulating layer: insulating paint can be divided into five categories: impregnated paint, enameled wire paint, coating paint, silicon steel sheet paint, anticorona paint, etc.The impregnation paint is used for impregnation motor, electric coil.Impregnating varnish can act as a filling gaps in the insulation system and microporous, and the dipping form a continuous film, and make the whole of the coil binding into a strong, effectively improve the integrity of the insulation system and thermal conductivity, resistance to moisture, the performance of the dielectric strength and mechanical strength.Second is also have the effect of heat dissipation, if insulating paint when soaking, drying after the coil can be considered as a whole, both inside and outside layer heat transmission can easily, so as to have the effect of heat.Dipping paint, insulation oil production technology in China now, preparation methods, patent formula technical data or is relatively backward, the production processing of impregnating varnish generally have the effect of short, only over time can appear to drop, the failure phenomenon.

   3.use question: we are in the process of using copper wire coil, often appear such problem - collision friction, flushing slower, water a lot of contact with the coil, use waste oil lubrication, conductor surface residue and insulation damage, conductor oxidation during subsequent processing;

   4. Copper wire annealing process: copper wire annealing refers to a metal heat treatment that is cooled at the corresponding speed after the copper wire is slowly heated to a certain temperature for a period of time.Copper wire annealing can reduce hardness, improve machining, eliminate residual stress, stabilize dimension, reduce deformation and crack tendency.Refine grain, adjust tissue, eliminate tissue defects.But once in the production process of temperature above 50 ℃ out of cans, rules extraction time and high SO2 content, protective gas impurity can cause the lack of annealing, a period of time after the copper wire will be easy to black.

Copper wire coil nigrescent reason is caused by many factors, not just the above four factors, also with wire itself of the state, coil processing, vulcanization process, structure, formulation of coil, coil production environment, and many other factors.


The reason why the copper wire is black

Copper wire nigrescent reason is caused by many factors, it is not just a rubber formula problems, also with wire itself in the state, rubber processing, rubber vulcanization process, the structure of cable, the sheath of rubber formula, production environment, and many other factors.

   1. Analysis of the causes of rubber hair adhesion and copper wire blackening

   1.1   the copper wire itself in the 50 to 60 s of the 20th century, the cause of most of the domestic manufacturers are using normal copper rod, copper content is 99.99%, are aerobic copper rod, production methods are copper ingot heating was prepared through multichannel rolling after black copper rod, a large, medium and small compare copper rod made of fine copper wire.Because copper itself is not free of oxygen, the surface of copper wire is inevitably oxidized during processing.In the eighty s of the 20th century, the domestic introduction of advanced production technology of oxygen-free copper rod, as well as the domestic self-developed oxygen free copper rod production technology, make whole oxygen-free copper rod, wire and cable industry are used that is improved the problem of black copper wire.But due to the processing of the copper rod, especially anneal process control and processing good copper wire core storage condition is bad, make the copper wire itself has mild oxidation, this also is one of the reasons for the black wire.

   1.2  The reason for rubber formula is that in the 1950s, rubber insulation was made from natural rubber and styrene.Since the insulating rubber is directly in contact with the copper wire, it is not possible to use sulphur directly for vulcanization, which means that the use of very little sulfur can also make the copper wire black.Must use some can decompose the free sulphur compounds, such as the aforementioned accelerator TMTD, vulcanizing VA - 7, at the same time will also cooperate with some vulcanization accelerator to improve the curing rate and degree of cure, to ensure the physical and mechanical properties of the rubber insulation and electrical performance.However, the elasticity, strength and permanent deformation of the insulating rubber are not as good as the rubber with sulphur (if the copper wire is not considered black).Decades of practice have proven that TMTD cannot solve the problem of black copper wire.In addition, insulation eraser should have all kinds of colors, red, blue, yellow, green, black is the basic color, these color appearance also can make rubber hair stick

And brass hair black.Formula of main filler is light calcium carbonate and talcum powder, because of the price, some manufacturers in order to reduce costs, with a special cheap price of calcium carbonate and talcum powder, the coarse filler particles, the content of free alkali, impurities, so with poor physical and mechanical properties, electric performance is not good, also easy to cause black copper wire.In addition, the plant USES superfine calcium carbonate to improve the physical mechanical properties of the insulating rubber, while the active calcium is mostly treated with stearic acid, which also causes the copper wire to be blackened.The use of va-7 vulcanizate can improve the black of copper wire, but because of the lack of vulcanization, the rubber is permanently deformed, which can cause the rubber to be sticky.Especially after the addition of the promoter ZDC, the rate of vulcanization is improved, and in order to prevent coke burning, the promoter DM is added to delay the coke burn time.Look from ZDC's structures, it is in the TETD structure between two connected sulfur connected to a metal zinc, structural formula is: S S H5C2 lots lots H5C2 > N - C - S - zinc - S - C - N < H5C2 H5C2 and TETD structured S S H5C2 lots lots H5C2 > N - C - S - S - C - N < H5C2 H5C2 very close, in formula also cannot avoid structure similar to that of thiuram black copper wire may be slightly longer time, but not fundamentally resolved.

   2. Analysis of wire and cable structure

   2.1   copper catalyst aging is the important reason for the sticky rubber cable research institute in the former Soviet union test show that: in the process of sulfide copper from contact with the rubber into rubber insulation, 1.0 2.0 mm thickness of insulation rubber copper 0.009 0.0027%.As is known to all, trace copper has great destructive effect on rubber, which is the catalytic aging of rubber.In the process of insulation sulfide, thiuram several free sulfur precipitation reaction with copper, forming active copper groups: CH3 │ CH2 - CH - C - CH2 - │ │ S S │ │ Cu Cu in aging, the weaker - S - S - bond rupture, forming active copper base: Cu - S -, its function, and rubber and oxygen at the same time, the damage of rubber long key molecules, make the rubber soft sticky, is a combination of low molecular chain.French sticky rubber research institute research also points out that while a recurring problem: if the rubber contains harmful metals, such as: copper, manganese and other heavy metal salts, then whatever kind of the accelerator, both rubber sticky phenomenon happens.

   2.2  the application of radioactive isotopes by the former Soviet scientists to the surface of the insulating rubber and copper wire in the rubber sheathed cable proves the possibility of the sulfur diffusion in the cable sheath rubber.Vulcanized rubber with natural rubber as base, under the temperature of 130-150 ℃, the diffusion coefficient of the free sulphur is about 10-6 cm2 / s.Continuous vulcanization production plants, vulcanized rubber sheath, the temperature between 185-200 ℃, the diffusion coefficient is bigger.Due to the diffusion of free sulfur in rubber, the structure of chulam rubber may be changed.These polysulfide compounds are migrated by chemical decomposition and chemical synthesis, known as chemical amplification.As a result of the migration, it can not only change the structure of the insulating rubber, reduce its heat resistance, but also the sulfur and copper surface reaction, forming copper sulfide and sulfide copper, resulting in black copper wire.In turn, copper sulfide and sulfide, which accelerate the aging of rubber, lead to the occurrence of sticky phenomenon.

   3. Reasons for processing technology

   3.1  The reason for the processing of rubber is that in the insulating formulation based on natural rubber and butyl benzene rubber, natural rubber needs to be plasticided to improve the plasticity of rubber.In order to produce, some of the big plants use the mixer, and a small amount of chemical plasticizer, promoting agent M to improve the plasticity.If the molding temperature and the temperature at which the raw rubber rubber filter control is not good, appear the high temperature of 140 ℃ above, when raw rubber into the mixing machine slowly through the drum, and the above product glue due to the hot oxygen and accelerator M's role at the same time, will find that the rubber surface coated with a layer of oil, is actually the rubber molecules under the promoting of chemical plasticizer chain scission is serious, the comparison of smaller molecular weight of soft sticky rubber.Although later with styrene butadiene rubber and mixing the rubber insulation materials, these small molecular weight of natural rubber is evenly dispersed in rubber, the extruded rubber continuous vulcanization on the copper wire, can don't see any problems at the time, but it is a hidden trap for rubber adhesive copper wire, that is to say, these small molecular weight of natural rubber will be the first to a local phenomenon of copper wire.The process of insulating rubber and vulcanizing agent and promoter is also very important.Some small factories add vulcanizing agent on the mill, which is to pour the canister of sulfide, in the middle of the roller, many, but less on both sides.When vulcanizates are in the rubber, the number of times of triangulation is less, and the vulcanization can be spread out in the rubber.In this way, there is a lot of sulfide in the place where the extrusion is continuous, and the copper wire is very easy to appear. In the dark place for a long time, there will be the appearance of rubber copper wire.

   3.2   insulating rubber vulcanization reasons in pursuit of production enterprise, continuous vulcanization tube is only 60 meters long, steam pressure is 1.3 Mpa, and the curing rate to open to 120 m/min, the insulating rubber tube in the residence time is only 30 seconds.Rubber itself is a poor conductor of heat, the surface of the insulation wire core temperature greater than 190 ℃, when the temperature of heat transfer by contact with the copper layer rubber, and copper heat, copper heat to the inner rubber temperature approaches, vulcanized rubber wire has been out of vulcanizing tube.The layer rubber temperature is lower, this is about 170 ℃, stay only a few seconds out of vulcanizing tube, enter cooling and take-up, insulating rubber will lack of sulfide.To get enough vulcanization.The dosage of accelerant TMTD (for vulcanization agent) up to 3.4%, excessive vulcanization agent, the free sulfur that is released during vulcanization process, except for crosslinking rubber molecules, there is excess free sulfur.This is why the copper wire is blackened.

In a word, the problem of solving the black problem of copper wire is still very difficult, and every process from copper wire to rubber must be taken seriously to achieve better results.The use of the adhesive selection and vulcanization system is still the key to the problem.The solution to this problem needs to be tested by time.

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