The cause of copper wire blackening
1. The area of the wire-drawing emulsion oil pool is small, the return flow pipe is short, and sealed, resulting in slow heat dissipation and high temperature of the emulsion oil.
2. It is caused by the annealing of copper wire.
(1) Even the cooling water is generally used tap water, groundwater, due to the water quality is not the same everywhere, in some areas the PH value of water is low, only 5.5~5.0 (normal is 7.0~7.5), the original emulsion in the anti-oxidation oil film were cleaned off, annealed copper wire easy to oxidation, black;
(2) The finished copper wire drawn in the ordinary wire drawing machine is annealed on another annealing line, and the cooling water is not used antioxidant. The antioxidant time is short, and the oxidation blackening phenomenon will soon occur;
3. Some old factories use annealing cylinders for annealing, so oxidation and blackening may also occur for the following reasons:
(1) The annealed cylinder nut is not tightened, after the carbon dioxide or high pure nitrogen leakage;
When the temperature of the copper wire out of the cylinder is too high, beyond 30℃;
Draw emulsion maintenance is not enough, PH value is too low;
These situations are more common in summer when the temperature is high, and the emulsion will lose a little when kept in use, but will lose quickly when the temperature is high. If the new crude oil is not replenished in time, there will be little fat content at this time. In addition to the high temperature, the temperature of the emulsion may exceed 45℃, which will easily cause oxidation blackening.
4. On the other hand, due to the widespread use of high-speed wire drawing, its speed is improved and the relative heat dissipation time is reduced, which brings a certain space and time for oxidation. Therefore, it is recommended that manufacturers pay more attention to the fat content of the emulsion, use temperature, PH value and other appropriate, the season of yellow mould in spring bacterial reproduction faster, can use fungicidal mildew agent, summer available antioxidant, solve oxidation, blackening and other problems.
1.reason
The deformation of the finished mold is too small
(2) mold insert sleeve periphery and the front did not seal well
The solution
Add a rubber pad at the outlet of the finished mold, and then screw the finished mold tightly to solve the problem of oil leakage.
It is a common mistake that the deformation amount of the finished mold is too small. Only when the deformation of the single mold has a minimum amount of deformation, can the pressure generated be greater than the yield limit of the metal, can the plastic deformation be realized, the size can be stable, and the light generated by the cold drawing on the surface of the single line be realized.
2.The cause of the coil's blackening
We often use a variety of products that use coils, such as motors, hearing AIDS, remote control toys, wireless chargers, power switches, computers... The coil is black because of copper wire oxidation. The main material of the coil is basically copper wire, and metals will oxidize, so we will see the coil black.
1. Technical reasons
Before most domestic manufacturers are used universal copper rod, copper content can reach 99.95%, but even so, there is oxygen in copper. Because copper itself is not oxygen-free copper, during the processing process, copper surface will inevitably come into contact with air and oxidation.
Now, the introduction of advanced production technology of oxygen-free copper in China and the development of oxygen-free copper production technology in China have made the whole copper wire industry use oxygen-free copper, which has undoubtedly greatly improved the blackening problem of copper wire.
However, due to the processing of the copper rod, especially the application of toughening technology, and the poor storage conditions of the finished copper wire core, the copper wire itself will still have a slight oxidation.
2. Material problem of insulating layer
Insulation paint can be divided into five types: impregnation paint, enameled wire paint, coating paint, silicon steel sheet paint, anti-corona paint, etc. Macerating paint is used for macerating motors and electric coils. Impregnated paint can fill the gap and microhole in the insulation system, and form a continuous paint film on the surface of the impregnated material, so that the coil bond into a solid whole, effectively improve the integrity of the insulation system, thermal conductivity, moisture resistance, dielectric strength and mechanical strength performance.
Secondly, it also plays the role of heat dissipation. When insulating paint is soaked, the coil after drying can be regarded as a whole, and the heat of inner and outer layer can be easily conducted, thus playing the role of heat emission.
At present, China's macerate paint, insulation oil production technology, preparation method, patent formula technical data is still relatively backward, the production and processing of macerate paint only plays a temporary role, a long time will appear to fall off, failure phenomenon.
3. Use problems
In the process of using coil copper wire, such problems often occur: collision friction; The washing is slow and the moisture is in contact with the coil. The use of waste oil lubrication, resulting in the conductor surface residue and insulation layer damage; Oxidation of the conductor during subsequent processing;
4. Copper wire annealing process
Copper wire annealing is a heat treatment process in which copper wire is slowly heated to a certain high temperature, kept for a period of time, and then cooled at a corresponding rate.
Copper wire annealing process can reduce hardness, improve machinability, eliminate residual stress, stabilize size, reduce deformation and crack tendency. Refine grain, adjust structure and eliminate structure defects. However, once the production process temperature above 50 ℃ out of cans, rules extraction time is insufficient, SO ₂ content high, protective gas impurity can cause annealing is insufficient, the copper wire after period of time will be easy to black.
Coil copper wire blackening is caused by a variety of factors, not only the above four problems, but also the state of copper wire itself, coil processing technology, vulcanization process, coil structure, formula, coil production environment and many other factors.
3.The cause of copper wire blackening of rubber sheathed cable
The black of rubber sheathed cable copper wire is caused by many factors, not only the formula of rubber, but also the state of copper wire itself, rubber processing technology, rubber vulcanization technology, cable structure, rubber sheathed formula, production environment and many other factors.
1. Cause analysis of rubber stickiness and copper wire blackening
1.1 Reasons for copper wire itself
In the 1950s to 1960s, most of the domestic manufacturers are using ordinary copper rod, copper content is 99.99%, are aerobic copper rod, the production method is the copper ingots after heating through multiple calendrons made of black copper rod, after large, medium and small draw copper rod into a relatively fine copper wire. Because copper itself is not oxygen-free copper, in the process of copper wire surface oxidation is inevitable.
In the 1980s, the introduction of advanced production technology of oxygen-free copper rod and the domestic self-developed production technology of oxygen-free copper rod made the whole wire and cable industry use oxygen-free copper rod, which undoubtedly improved the blackening problem of copper wire. However, due to the processing of copper rod, especially the mastery of toughening technology and the poor storage conditions of the processed copper wire core, the copper wire core itself has been slightly oxidized, which is also one of the reasons for the black of copper wire.
1.2 Reasons for rubber formulation
In the 1950s, rubber insulation was made of natural gum and styrene butadiene gum. Since the insulating rubber is in direct contact with copper wire, sulfur cannot be used as a vulcanizing agent directly, and even the use of very little sulfur can make copper wire black. It is necessary to use some compounds that can break down free sulfur, such as the previously mentioned accelerator TMTD and vulcanization agent VA-7, together with some vulcanization accelerator to improve the vulcanization speed and degree to ensure the physical, mechanical and electrical properties of the insulating rubber. But in terms of elasticity, strength and permanent deformation, insulation rubber is not as good as rubber with sulfur (if copper wire is not considered black). Decades of practice have proven that TMTD cannot solve the blackening problem of copper wire.
In addition, insulation rubber to have a variety of colors, red, blue, yellow, green, black is the basic color, the appearance of these colors will also make rubber sticky and copper wire 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.
Some factories use active ultrafine calcium carbonate to improve the physical and mechanical properties of insulation rubber, while most active calcium is treated with stearic acid, which is also the cause of copper wire blackening. The use of vulcanizing agent VA-7 can improve copper wire blackening, but because the degree of vulcanization is not enough, rubber permanent deformation is large, will cause rubber stickiness. Especially after the addition of accelerator ZDC, the curing rate was increased. In order to prevent the burning, the accelerator DM was added to delay the burning time.
Look from ZDC's structures, it is in the TETD structure between two connected sulfur connected to a metal zinc, structured as a 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. Analyze the structure of wires and cables
2.1 The catalytic aging of copper is an important cause of rubber's stickiness.
The former Soviet Union cable Scientific Research Institute test proved: copper in the vulcanization process from the rubber contact into the insulation rubber, the thickness of 1.0-2.0mm insulation rubber containing copper 0.009-0.0027%. It is well known that trace amounts of copper have a devastating effect on rubber, which is often referred to as the catalytic aging of heavy metals on rubber.
In the process of insulation sulfide, thiuram several free sulfur precipitation reaction with copper, forming active copper group 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. The French Rubber research institute also pointed out that if the rubber contains harmful metals, such as copper, manganese and other heavy metal salts, then regardless of the type of accelerator, rubber will be sticky phenomenon.
2.2 Migration of sulfur from rubber sheathed cable to the surface of insulating rubber and copper wire
Soviet scientists used radioisotopes to confirm the possibility of sulfur spreading from the cable sheath rubber. In the vulcanized rubber based on natural rubber, the diffusion coefficient of free sulfur is about 10-6cm /s at 130-150℃. In a continuous vulcanization plant, the diffusion coefficient is greater when vulcanizing sheathed rubber at a temperature between 185-200℃.
Due to the diffusion of free sulfur in rubber sleeve, the structure of the rubber may be changed and polysulfur bonds may be formed. These polysulfur compounds migrate through chemical decomposition and combination, known as "chemical enlargement." As a result of the migration, not only can the insulation rubber structure, reduce its heat resistance, and sulfur and copper surface reaction, the formation of copper sulfide and cuprous sulfide, resulting in copper wire black. In turn, copper sulfide and cuprous sulfide accelerate the aging of rubber, and lead to the occurrence of sticky phenomenon.
3. Reasons for processing technology
3.1 Reasons for rubber processing
In the combination of natural rubber and styrene butadiene rubber insulation formula, natural rubber needs to be plasticized to improve rubber plasticity. Some large factories, in order to yield, plasticize with mixer, also add a small amount of chemical plasticizer - accelerator M to improve 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 adding vulcanizing and accelerator to the insulating rubber is also very important. Some small factories in the open refining machine to add vulcanizing agent, is to have the canister of vulcanizing agent, in the middle of the drum into, in the middle of a lot, and less on both sides. When vulcanizing agent into the rubber, the number of triangle turn less, will make the vulcanizing agent in the rubber distribution is not uniform. So in the extrusion bag continuous vulcanization, containing more vulcanizing agent is easy to appear in the copper wire blackening phenomenon, in the black place for a long time, there will be the phenomenon of rubber copper wire.
3.2 Reasons for insulating rubber vulcanization
Some enterprises in order to pursue output, continuous vulcanized pipe only 60 meters long, steam pressure is 1.3Mpa, and vulcanized speed to 120 meters/minute, so the insulation rubber in the pipe stay time is only 30 seconds.
Rubber itself is a poor conductor of heat, insulation wire core surface temperature is more than 190℃, when the temperature heat to contact with copper wire inner rubber, and copper wire heat absorption, copper wire temperature and the inner rubber rubber is close to the temperature, vulcanized rubber wire core has been out of the vulcanized tube. This layer of rubber temperature is relatively low, about 170℃, stay only a few seconds out of the vulcanization tube, into the cooling and cable, insulation rubber will be insufficient vulcanization. In order to achieve sufficient vulcanization. The dosage of accelerator TMTD (used as a vulcanizing agent) is up to 3.4%. Excessive vulcanizing agent also gives off more free sulfur during the vulcanizing process. In addition to providing crosslinked rubber molecules, there is also excess free sulfur. This is what blackens the surface of copper wire.
In a word, it is still difficult to solve the problem of copper wire blackening. Every working procedure from copper wire to rubber should be taken seriously so as to achieve better results. The selection of rubber seed and the adoption of vulcanization system are still the key problems. The solution of this problem will stand the test of time.