[China Aluminum Network] article published in the Lw2016 proceedings - author Zhang Anle, He Yuzhi, Liu Xuemei (Luoyang Longding Aluminum Co., Ltd.)
With the continuous improvement of people's lives, aluminum products are becoming more and more widespread in our lives. The problem of improving the quality of electronic Aluminum Foil is particularly important. Electronic foil production process as long as divided into rolling and finishing two parts. In recent years, the market demand for electronic aluminum foil has gradually shifted to higher quality and greater differences. Finishing techniques represented by processes such as cleaning, shearing, rewinding and annealing have become very important, involving stability and improvement. The quality of products and the ability to improve the ability of companies to meet the needs of customers' different needs have become the key issues that companies must face in order to survive and develop.
1 defects on the surface of aluminum foil
1.1 Pressure pit
After the aluminum foil is cleaned, it must be awakened and dried. Since the rolling mill and cleaning agent are flammable and explosive, the ignition point is about 200°C. During the drying process, the aluminum foil is cut off by solid particles that are peeled off from the air passages, heat exchangers, drying boxes, etc. The small particles are wound between the steel roll and the aluminum foil and are generally formed on the foil surface. Defects, lower product quality; large particles can even cut through the foil, causing scrap
1.2 Oil spots
In the cleaning and rinsing process of the aluminum foil, the nozzle sprays the cleaning agent onto the foil surface with a certain pressure and flow rate. After the cleaning agent reaches the foil surface and rebounds to the four walls, a large amount of oil mist will be generated, and the oil spots will form over time. .
1.3 bruises
Wiping and scratching is a common quality problem in all finishing equipment including cleaning. The mechanism is that the electronic aluminum foil slips on the thin surface and the roll surface during the cleaning process, but the causes of slipping involve machinery, electrical appliances, and processes. Various aspects.
1.4 Wrinkles
The thickness of the electronic aluminum foil entering the cleaning pass is generally around 0.1mm. Due to the thin incoming materials, large fluctuations in the plate type, and the appearance of medium wave and variable wave, the material in the cleaning process will pass through the pinch roller and the squeeze roller. Wrinkles appear.
2 measures to improve the foil surface
2.1 The improvement measures of the pressure pit
The control of the crater is divided into two steps for the maintenance of the pre-equipment only during and after maintenance. The high-temperature oxidation of drying equipment is unavoidable, but the oxidation-resistant stainless steel material was used in the previous equipment manufacturing process, and the protective gas welding process such as argon arc welding may reduce the oxidation of the material surface and the welding part after use. The possibility. In the later period of use, multi-layer stainless steel filters are added to the air duct. In order to reduce the clogging of the filter and reduce the air volume, the filter can be periodically cleaned or replaced for daily maintenance.
2.2 Oil Spot Improvement Measures
During the cleaning and rinsing of the aluminum foil, a large amount of high-concentration oil mist is generated in the box and eventually falls on the surface of the foil to cause pollution. Due to the large amount of evaporative exhaust that consumes cleaning agents, increases the cost of the enterprise, and the effect is not ideal, it is only considered to block the oil droplets to the foil surface. It was found that the oil droplets were mainly installed on the top of the box with an arc-shaped baffle during the distance from the squeeze roller to the rinsing tank, and an oil reservoir was installed at the top of the outlet of the rinsing tank to direct the oil droplets to both sides to eliminate the oil spots on the foil surface. .
2.3 Wipe scratch improvement measures
The causes of scratches and scratches are mechanical structure, electrical control and process selection.
1 For each roller can be synchronized to check whether the synchronous toothed belt is tight and the bearing is lubricated in place;
2 Electrical adjustment The motor parameters make each active roller not synchronized, and the control method of the correction coil diameter error selects simple tension control and speed control.
3 The process tension and speed settings should be matched with the front and rear passes to select a more reasonable range.
2.4 Wrinkle Improvement Measures
For the poor version of the material, the following measures have been taken: 1. Adding several sets of S-shaped U-rolls on both sides of the unwinding and rewinding to correct the effect; 2. Mounting the plate-type adjusting rolls on both the unwinding and take-up sides. Eliminate edge waves by adjusting the level and parallelism of the roller; 3. Eliminate mid-waves by increasing the roller or other convexity.
3 Electronic aluminum foil cleaning
3.1 Status Analysis
3.1.1 The importance of cleaning
Electronic aluminum foil is a deep-processing technology, the surface quality of the impact on the electronic storage capacity of the previous process in the aluminum foil surface caused by minor defects will be amplified in the subsequent process, so only in the production process of each process on the foil surface quality strict control.
3.1.2 The process of cleaning
The cleaning process of the aluminum foil is as follows: the strip material enters the device from the uncoiler and inlet deflector roller, first passes the lower brush roller, and a cleaning liquid is sprayed between the lower brush roller and the strip material to wash the lower surface of the strip material. Then, the strip passes through the upper roll, and a cleaning liquid is sprayed between the upper roll and the strip to wash the upper surface of the strip. The strip then enters the rinse tank. Or use the same cleaning solution to spray the upper and lower surfaces of the strip. After 2# dry roller is used to squeeze the clean oil on the strip surface. After the strip is rinsed out of the box, it enters the drying box and the remaining cleaning liquid on the strip is evaporated under the blowing of hot air. Later, after the strip passes through the outlet deflector roller, it is wound up by a winder and is wound up. Cleaning is over.
4 Cutting of Electronic Foil
4.1 Description of the status of equipment and quality defects
There are different types of shears, these devices are both narrow and wide, both trimming and pulling, both single-axis and double-axis, no matter what type of shear mainly by decoiling, slitting, The coiling consists of three parts. With customers' demand for aluminum foil rolls, the company will change its weight, quality, delivery time, and specifications. The cutters, shafts, rollers, and die parts of the shearing machine all face problems such as increased wear, reduced precision, and frequent replacement. The shearing part may cause scratches, pressure pits, burrs and other quality defects due to the manufacturing and mating accuracy of the disc knife and the knife pad. Due to the use and design issues of the surface pressure roller, take-up shaft and die, the take-up part can cause defects such as flanging, splitting, and unstable internal stress.
4.2 Causes and Improvements of Cutting Quality Defects
4.2.1 Scratching
Cause: The problem of scratching and scratching is a common problem in the cutting process, and it is also a difficult problem to solve completely. The main cause of scratches and scratches is due to the sharp corners of the end face when the disc knife or knife pad is assembled with the knife shaft. When the aluminum foil slides over the sharp corners, the material of the lower knife or knife pad is harder than the aluminum foil at a specific rotation speed. In a very short period of time, there is minimal slip, reflected on the material surface is a punctiform or linear scratch. Because everyone pays more attention to the machining accuracy and assembling accuracy of the disc cutter, knife pad and cutter shaft, the scratches and scratches caused by the above reasons will not be discussed here. This article mainly studies the following situations that are easily overlooked. Because the disc cutter will become dull after using for a period of time, the new knife needs to be replaced frequently, and the knife pad is generally fixed, and each time the new disc knife is changed, the equipment and quality defects of the disc knife and the knife pad will be described. Our company currently has several different models of aluminum foil shearing machines. These equipments have both narrow width and wide width. Both the trimming and the long-term accumulation of the pulling strips will cause the outer diameter of the cutter pad at the joint to become relatively small. A lot of old disc cutters are used up, and the sharp corner problem after putting in a new batch of disc cutters will be more prominent. 2 design problems: aluminum foil prone to flanging and pressure pits in the cutting process, mainly due to aluminum powder sticking knife. There are two sources of aluminum powder, one is the aluminum powder attached to the surface of the aluminum foil; the other is the aluminum powder produced during the shearing process. The two parts of aluminum powder gather on the blade tip to make the blade blunt, thus causing the material surface to turn over. When the aluminum powder falls onto the material surface, it will produce a pressure pit. Improvement measures: The new knife needs to be replaced frequently, and the knife pad is generally fixed. Every time a new disc knife is changed, the status of equipment and quality defects of the disc knife and knife pad will be polished.
4.2.2 Flanging and Pressing
Cause: Aluminum foil is prone to flanging and crushing during the slitting process. The main cause is the aluminum powder sticking knife. There are two sources of aluminum powder, one is the aluminum powder attached to the surface of the aluminum foil; the other is the aluminum powder produced during the shearing process. The two parts of aluminum powder gather on the blade tip to make the blade blunt, thus causing the material surface to turn over. When the aluminum powder falls onto the material surface, it will produce a pressure pit. Improvement measures: (1) Add a set of aluminum powder purging device, blow the tool in the opposite direction, and remove the aluminum powder attached to the tool; (2) Immerse the felt in light oil such as kerosene, diesel, etc., and put it on the knife. Cut the felt on-line to wipe the surface of the knife to prevent the aggregation of aluminum powder; 3 Soak the tool with 5‰NaOH alkali solution and heat it to 60-70°C. After removing, rinse with clean water and dry it. This method can be used on the knife. Form a protective layer on the surface to reduce the amount of aluminum foil sticking.
4.2.3 uneven surface layer and volume density
Causes: The reason for the disagreement between the end dislocation and the volume density is mainly on the take-up shaft. When the heavier shaft is used to cut the heavier material roll, whether it is the inflation-preserving inflation shaft or the continuous inflation shaft, When the weight of the roll exceeds the supporting force provided by the air pressure, the self-weight of the roll is too large, causing the tube to sagging, eccentricity of the roll, and affecting the roll density and end face quality. Improvement measures: The simpler measure is to replace the knife pad in time, and secondly, the structure of the outer rubber-coated knife pad can be adopted. The outer diameter size is larger than the disc knife outer diameter 0.01ram-0.05ram, and the upper part is a rounded corner. The radius is about 0.01ram - 0.15ram, which is covered with urethane rubber and hardness ≥ HS85. Upper and lower knives usually use external gear transmission. According to the change of the upper knife diameter, the number of teeth and modulus of the upper knife transmission gear can be adjusted to achieve the purpose of matching.
4.2.4 Jumping and teething
Reason: Jumping and punching are problems that can easily occur during tool use. The outer diameter of the upper knife will be reduced 6-8ram cumulatively after repeated grinding, relying only on the gap between the upper and lower knife transmission gears for elastic fit, can not guarantee the overlap of the upper and lower knife, which will make the inner wall of the steel tube core provide support and torque structure Instead, the shaft provides the support and the drive pin provides the rotational torque structure. Both of these problems can cause equipment damage and waste. Improvement measures: The upper and lower blades are usually driven by external gears. According to the change of the upper knife diameter, the number of teeth and modulus of the upper knife transmission gear can be adjusted to achieve the purpose of matching. By improving the take-up shaft, the drive and support functions are separated, and the use of bearings for support can ensure the stability of the shaft rotation and improve the quality of the coil. By adopting the clutch transmission, frequent replacement caused by cone wear can be eliminated and the maintenance cost of the equipment can be reduced.
5 Rewinding of electronic aluminum foil
5.1 Technical Requirements for Aluminum Foil Rewinder
In order to ensure that the paper roll does not deform or crack during transportation or storage, it can run smoothly on printing equipment or other processing equipment. The finished paper roll must have sufficient hardness, and the inner tight outer core must have sufficient hardness and uniform radial hardness distribution. Therefore, the rewinding machine must possess the following kinds of functions: 1 The set integrator of the support roller torque is set so that the input speed signal is a smoothly rising ramp signal instead of a sudden change. By changing the integration date of the given integrator to the constant, the E slope of the ramp signal can be changed. When the system is started, the rotational speed acceleration is smaller than when there is no given integrator; 2 the pressure of the platen roller is adjusted and extracted; 3 the “disturbance†start of the electric drive and the appropriate speed program control; 4 the indirect or willingness to connect the tension Control etc.
Figure 1: Aluminum foil rewinding machine
5.2 The composition of the electronic control system
The front roller, back roller and exit roller of the rewinding machine are respectively driven by separate AC motors. The longitudinal cutting knife adopts AC variable frequency drive and maintains 5% - 20% speed difference with the back bottom roller. The auxiliary transmission consists of two parts: pneumatic and hydraulic systems, which are used to control the operation of the auxiliary transmission machinery and cooperate with the main transmission. The entire electronic control system is mainly composed of three volumes, and the chain of front and rear bottom rollers is also adjusted to be smaller.
5.3 Control of Rewind Roll Tension
The control of the tension of the unwinding roll affects the form of the finished roll. Stable web tension can avoid lateral deflection of the web. The proper web tension can improve the quality of the web to a certain extent, reduce the end of the web, and keep the winder stable. Therefore, web tension control is an important part of the electronic control system.
5.4 Dynamic Compensation in Roll-out Tension Control
In the actual operation of the system, the diameter of the unwinding roll is getting smaller and smaller. Due to its own inertia, the exiting paper roll should have positive dynamic torque when accelerating lifting, decelerating parking and steady running. Moment M. To compensate for the energy that needs to be absorbed.
6 Annealing System Effect on Aluminum Foil Performance
6.1 Effect of Thickness on Finished Properties of Aluminum Foil
When the metal undergoes cold deformation, the internal energy of the metal will rise, and the atoms will be in an unstable state. Naturally, there is a tendency to want to stabilize the state. Most metal materials do not want to complete this transformation at room temperature. When the metal back heats, Increasing the activity of atoms and accelerating the diffusion of atoms can complete the transition of atoms to stable states. This is the internal reason why the cold-deformed metal will fly and recrystallize during annealing. However, the thermal energy provided to the atom at the temperature of the cold-deformed metal back heating is sufficient to overcome the interatomic bonding force, so that the atoms can migrate and freely diffuse to occur in the crystallization, and the recrystallization temperature depends on the atom migration to re-form the crystal nuclei and The size of the activation energy needed to grow up, the higher the required activation energy, the higher the recrystallization temperature. The first option is to intermediate-anneal the aluminum foil blank at a thickness of 1.5 mm (about 80% cold deformation rate). The second option is to intermediate-anneal the aluminum foil blank at a thickness of 2.5 mm (cold deformation processing rate is about 65%). The smaller the production rate of the second billet, the higher the activation energy required for the recrystallization of the metal, the higher the recrystallization temperature and the higher the strength. On the other hand, the 2.5 mm intermediate annealing of the aluminum foil blank is processed into According to the metallurgical theory, the storage energy mainly retained in the form of dislocations in the metal structure is the driving force for recrystallization during annealing, and the nucleation rate in the recrystallization process increases as the amount of metal deformation increases. Therefore, 2.5 is used. In the intermediate annealing of aluminum foil blanks, the finished aluminum foil obtained by rolling has a greater amount of deformation during annealing, and the stored energy in the form of dislocations is also greater. In the recrystallization process, the nucleation rate in the original aluminum foil is greatly increased. As a result, the aluminum foil can obtain finer grain structure after the finished product is annealed, so its strength and elongation are higher.
6.2 Effect of Temperature on the Properties of Aluminum Foil Finished Products
For the aluminum foil billet produced by the casting and rolling method, the cooling solidification and deformation of the metal during the casting and rolling are performed in the casting area with a roll diameter of 650 mm to 700 mm. The Yuanji Large Cast Zone has a length of about 50 mm. The length of the casting zone is only about ten millimeters. The solidification of Yuan metal only completes this cooling in about 1s. The speed of solidification is about two orders of magnitude higher than semi-continuous casting. Various impurities and alloying elements in aluminum alloy are The solubility of aluminum in the solution varies with temperature. For example, according to the equilibrium phase diagram, the solubility of iron in aluminum at the eutectic temperature (655 °C) is about 0.052%, and the solubility decreases to 0.002% at room temperature. The faster the cooling rate deviates from the equilibrium, the more severe it is. Therefore, the intragranular segregation of the billet produced by the casting method and the degree of supersaturation of the solid solution are more serious than semi-continuous casting. If the annealing temperature is high (to the homogenization temperature) during the intermediate annealing, supersaturated elements in the metal can be promoted. When the charge is analyzed, the decrease of the solid solubility in the phase increases the self-diffusion coefficient of the atom, which favors the nucleation and growth of the new nuclei when annealing reduces the recrystallization temperature of the material. Similarly, if the temperature during the intermediate annealing does not reach the homogenization effect However, merely satisfying the plastic recovery of the metal is that the supersaturated solid solution of the metal is not fully analyzed.
Therefore, the aluminum foil produced by adopting the scheme 3 is more likely to be crystallized under annealing under the same conditions during the finish annealing, and the internal nucleation and the solid solution are increased due to the homogenization treatment. The grain structure is finer, so the elongation of the finished product is higher. The strength of the rolled surface of the ordinary intermediate annealing aluminum foil billet is higher because the temperature during the intermediate annealing is not enough, and the intragranular segregation in the internal structure of the material occurs. (2) The solid solution does not completely precipitate, and the aluminum foil has a solid-solution strengthening effect. However, if the temperature continues to increase during the finish annealing, the grain may continue to grow, resulting in a sharp decrease in strength and elongation.
7 Conclusion
Electronic aluminum foil is a product with high quality control requirements, so the details of the process must be taken seriously. During the design, manufacturing, and use of the equipment, maintenance personnel must take the initiative to participate in it and reduce the inherent defects of the equipment to a small extent, which can create favorable prerequisites for the use and maintenance of equipment in the future.
The main way to solve the scratched aluminum strip is to improve the precision of the cleaning agent. According to the different production of aluminum foil, the aluminum foil rewinding machine to be used is not the same. According to the characteristics of aluminum foil, the problems that are needed in the production process are raised.
According to the needs of the industrial control of aluminum foil annealing furnace, the defects and improvement measures in the annealing were studied. The industrial experiment tests the uniformity of the furnace gas temperature and the material temperature in the aluminum foil annealing furnace and the temperature of the insulation process. The temperature control system can meet the aluminum foil annealing furnace industry. Production requirements.
references
[1] Xu Jun, Chen Xuesen. Current status of China's aluminum industry and future development and construction. Light Metals, 2001, (10): 3-6
[2] Xie Xingang. Production and quality control of aluminum for flexible packaging. China Packaging Industry, 1998, (12): 38-40
[3] Wang Cuimei, Jiao Xinggui, Yu Wenchun. Design and application of aluminum foil annealing furnace. Light Metals, 2003, (12): 47-50
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