A production method of cold-rolled aluminum coil for battery aluminum foil

Abstract

The application discloses a production method of cold-rolled aluminum coil for battery aluminum foil, and comprises the following steps: casting and rolling a coil as raw material, cold-rolling the raw material to 4mm for the first time, cold-rolling to 2.2mm for the second time, annealing in an annealing furnace, cooling, cold-rolling to 0.9mm for the third time, re-rolling and edge cutting of a semi-finished product, cold-rolling to 0.45mm for the fourth time, cold-rolling to 0.22-0.24mm for the fifth time, re-rolling and edge cutting of a finished product, and transferring to a foil rolling workshop. The application avoids quality defects of aluminum strips caused by sticking and damage, and good plate shape is obtained.

Description

Technical Field

[0001] This invention relates to the field of cold-rolled aluminum coil production technology, and specifically to a method for producing cold-rolled aluminum coils for battery aluminum foil. Background Technology

[0002] The production process of battery aluminum foil is roughly completed in three workshops: The first step is to produce cast aluminum coils in the casting and rolling workshop. Electrolytic aluminum, remelted aluminum ingots, and intermediate alloys are fed into a melting furnace for melting and alloy composition adjustment. After refining the aluminum melt to remove impurities, the cast aluminum coils are obtained through a casting and rolling mill. The second step is to produce cold-rolled aluminum coils in the cold rolling workshop. After thinning in a cold rolling mill, edge trimming in a rewinding machine, and annealing in an annealing furnace, cold-rolled aluminum coils are obtained. The third step is to roll the cold-rolled aluminum coils into battery aluminum foil in the foil rolling workshop. It is evident that the cold-rolled aluminum coils produced in the second step are an indispensable link in the battery aluminum foil production process, playing a crucial role in connecting the preceding and following steps.

[0003] Currently, complaints about battery aluminum foil produced by manufacturers and delivered to downstream customers mainly focus on three aspects: excessive pinholes (longitudinal linear pinholes, transverse pinholes, and excessive number of pinholes), unqualified plate shape, and unqualified surface quality. These three types of complaints account for more than 80% of the total complaints, while other defect complaints are occasional and sporadic.

[0004] Regarding the issue of excessive pinholes, the cooling process of cast-rolled aluminum coils, as well as the heating and cooling processes of annealed aluminum coils, inevitably result in cold shrinkage and thermal expansion adhesion. Furthermore, the surface of cast-rolled aluminum coils is dry, and the surface of annealed aluminum coils remains dry, lacking oil lubrication. During uncoiling, the dry surface can also experience adhesion due to tension fluctuations, resulting in dry surface uncoiling adhesion. The essence of adhesion is excessive local pressure between aluminum coil layers, causing localized metal sections of the upper and lower layers to firmly "bond" together. When uncoiling, a section of metal from one layer detaches from the aluminum substrate and adheres to another layer. Therefore, the result of adhesion is a small protrusion on one layer and a small pit on the other. During rolling, foreign matter such as aluminum powder and dust can fall into this pit, forming pinholes when rolled into the finished battery aluminum foil (approximately 0.013 mm thick). When small protrusions pass through the tension rolls and coloring rolls of the cold rolling mill, some may detach and adhere to the tension rolls and coloring rolls, causing scratches on the aluminum coil. These scratches may further develop into surface quality defects such as black streaks. Meanwhile, the small protrusions that do not detach are pressed into the surface of the aluminum plate by the cold rolling mill, forming metal indentation. The bonding between this metal indentation and the aluminum plate substrate is not very strong. When it is rolled into the finished battery aluminum foil later, it may detach from the substrate, thus forming pinhole defects.

[0005] Regarding the issue of substandard sheet shape, the ideal sheet shape is achieved through similar deformation, meaning the thickness of the aluminum sheet is reduced proportionally at all locations across its cross-section. However, during cold rolling, the cold rolling work rolls are designed with a central crown, called the work roll mechanical crown. Simultaneously, the thinning of the aluminum sheet during cold rolling generates heat, and a portion of the mechanical energy of the cold rolling mill is converted into heat energy for the aluminum sheet and rolls, resulting in thermal expansion and contraction, creating a thermal crown. The crown of the cast-rolled aluminum coil, the work roll mechanical crown, and the thermal crown during rolling collectively determine the final crown of the aluminum coil. The greater the crown variation (from the start of feeding into the melting furnace to the yield rate of battery aluminum foil packaging and warehousing), the worse the similar deformation and the worse the sheet shape.

[0006] Furthermore, many surface quality issues in battery aluminum foil are closely related to the cold rolling production process. In short, the cold rolling process often significantly affects the defect rate and product yield of battery aluminum foil. Summary of the Invention

[0007] The purpose of this invention is to propose a method for producing cold-rolled aluminum coils for battery aluminum foil. This method is applicable to 1060 / 1070 aluminum alloys. By optimizing and controlling the production process of each step of cold rolling, the probability of quality defects (such as linear pinholes, transverse pinholes, etc.) is significantly reduced, greatly improving product yield and reducing production costs. When cold-rolled aluminum coils produced using this method are used to produce battery aluminum foil, the yield reaches over 70% (from the start of feeding into the smelting furnace to the packaging and warehousing of the battery aluminum foil), which is 5-10 percentage points higher than the industry average of 60-65%, resulting in significant benefits.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a method for producing cold-rolled aluminum coils for battery aluminum foil, comprising the following steps: incoming cast-rolled coil → first cold rolling to 4mm → second cold rolling to 2.2mm → annealing in an annealing furnace → cooling → third cold rolling to 0.9mm → rerolling and trimming of the semi-finished product → fourth cold rolling to 0.45mm → fifth cold rolling to 0.22-0.24mm → rerolling and trimming of the finished product → transferring to the foil rolling workshop; the requirements for the above cold rolling steps are as follows:

[0009] The mechanical crown of the cold rolling work roll is 0.005±0.002mm, and the surface roughness Ra is 0.5±0.02um; the crown of the cast-rolled coil is required to be 0.2-0.4%.

[0010] During the first and third cold rolling processes, no tension rolls or coloring rolls are used, and the uncoiling tension is 1.0 ± 0.1 kg / mm. 2 Rolling oil is sprayed onto the surface of the inlet guide roll at a rate of 0.5-1.0 liters per second. Tension rolls and coloring rolls are added during the second, fourth, and fifth cold rolling processes. During the second cold rolling, the coiling tension is 1.6 ± 0.1 kg / mm. 2 .

[0011] During the first cold rolling, the rolling speed was 400-450 m / min and the rolling oil temperature was 30±1℃; during the second cold rolling, the rolling speed was 550-600 m / min and the rolling oil temperature was 32±1℃; during the third cold rolling, the rolling speed was 700-750 m / min and the rolling oil temperature was 32±1℃; during the fourth cold rolling, the rolling speed was 850-900 m / min and the rolling oil temperature was 35±1℃; during the fifth cold rolling, the rolling speed was 550-700 m / min and the rolling oil temperature was 35±1℃.

[0012] The requirements for the above rewinding and trimming steps are as follows:

[0013] The cutting speed of the semi-finished product rewinding and trimming is 200-350m / min. It is fed into the first set of tension rollers, but not into the second set of tension rollers or the winding and flattening rollers.

[0014] The cutting speed for rewinding and trimming the finished product is 300-550 m / min. The product is fed into the first and second sets of tensioning rollers, but not into the winding and flattening rollers.

[0015] As a preferred embodiment of this technical solution, the requirements for the annealing furnace annealing step are as follows:

[0016] Drill a thermocouple hole 30-40mm deep at a point 50mm away from the steel sleeve on the end face of the aluminum coil, and insert a thermocouple to measure the temperature of the aluminum coil metal.

[0017] The annealing process in the furnace is divided into three stages. In the first stage, the furnace gas temperature is set to 300℃, and the heating time is set to 15 minutes. After the furnace gas temperature reaches 300℃, it is maintained for 45 minutes. After the time is up, the process proceeds to the next stage. In the second stage, the furnace gas temperature is set to 580℃, and the heating time is set to 30 minutes. After the furnace gas temperature reaches 580℃, it remains unchanged. When the temperature of the aluminum coil reaches 550℃, the timing starts, and the process proceeds to the next stage. In the third stage, after 3 hours of timing, the coil is removed from the furnace and cooled. The cooling process involves natural air cooling for the first 2 hours after removal from the furnace, followed by forced air cooling using a fan after 2 hours.

[0018] As a preferred embodiment of this technical solution, during the first and second cold rolling processes, tension rolls and coloring rolls are not used. After tension is established, the distance between the aluminum strip and the upper and lower tension rolls, coloring rolls, and the entry shear blade is not less than 3mm.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] 1. In the first cold rolling production, the incoming material is cast-rolled aluminum coil, and in the third cold rolling production, the incoming material is annealed aluminum coil. The aluminum coils produced in these two cold rolling productions have cold shrinkage adhesion, thermal expansion adhesion, and dry surface uncoiling adhesion. In the first and third cold rolling, the present invention does not use tension rolls and coloring rolls, which overcomes the technical bias and will not cause scratches due to vibration. It also reduces the small protrusions that adhere firmly to the tension rolls and coloring rolls, which cause scratches between the small protrusions and the aluminum strip, thereby reducing the probability of linear pinholes in the aluminum foil blank after it is rolled into finished aluminum foil.

[0021] 2. This invention sprays rolling oil onto the surface of the inlet guide roller. The rolling oil adheres evenly to the surface of the inlet guide roller, providing lubrication and isolation. When the small protrusions are pressed against the guide roller by the aluminum strip, the adhesion between the protrusions and the guide roller is not firm due to the presence of a rolling oil film, sometimes preventing the protrusions from being pressed onto the guide roller at all. Therefore, this reduces the scratches caused by the small protrusions adhering firmly to the inlet guide roller.

[0022] 3. This invention finds the optimal match between many factors such as the crown of the cast-rolled coil, the mechanical crown of the cold rolling work roll, the amount of deformation, the rolling speed, and the temperature of the rolling oil, thereby obtaining a good sheet shape and reducing the clump-like adhesion caused by poor local sheet shape, which will develop into transverse pinholes after foil rolling.

[0023] 4. This invention has taken measures to reduce heating and cooling rates, thereby reducing thermal expansion and contraction damage. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the rolling mill structure when the tension rolls and coloring rolls are put into use.

[0025] Figure 2 A schematic diagram of the rolling mill structure when the tension rolls and coloring rolls are not in use. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Please see Figure 1-2This invention discloses a method for producing cold-rolled aluminum coils for battery aluminum foil, comprising the following steps: incoming cast-rolled coil → first cold rolling to 4mm → second cold rolling to 2.2mm → annealing in an annealing furnace → cooling → third cold rolling to 0.9mm → rewinding and trimming of the semi-finished product → fourth cold rolling to 0.45mm → fifth cold rolling to 0.22-0.24mm → rewinding and trimming of the finished product → transfer to the foil rolling mill. Specific embodiments of the above production method are described below.

[0028] Example 1

[0029] The incoming material for the cast-rolled coil is 1070 aluminum alloy, with a thickness of 6.95mm, a width of 2010mm, a coil weight of 28879kg, a crown of 0.29%, and a metal temperature of 46.2℃.

[0030] For the first cold rolling production, the cold rolling work roll crown was 0.0051 mm, the work roll roughness was 0.49 μm, and the cold rolling exit thickness was 4 mm. During the strip threading process before rolling, the inlet guide roll was sprayed with oil at a rate of 0.6 liters / second. The upper and lower tension rolls were open and not used, the coloring roll was not used, and the uncoiling tension was 1.0 kg / mm. 2 After the rolling speed is increased to 420 m / min, it is maintained at a constant speed, and the rolling oil temperature is 29℃. After the first cold rolling is completed, the process begins a second cold rolling.

[0031] In the second cold rolling production, the cold rolling work roll crown was 0.0051 mm, the work roll roughness was 0.49 μm, and the cold rolling exit thickness was 2.2 mm. During the strip threading process before rolling, the inlet guide roll was sprayed with oil at a rate of 0.6 liters / second. The upper and lower tension rolls and coloring rolls were put into use. After the rolling speed was increased to 580 m / min, constant speed rolling was maintained. The rolling oil temperature was 31℃, and the coiling tension was 1.6 kg / mm. 2 After the second cold rolling is completed, it is transferred to an annealing furnace for annealing.

[0032] Before loading the aluminum coil into the annealing furnace, thermocouple holes are drilled on the end face of the aluminum coil. After inserting the thermocouple, the following program is entered into the computer software in the control room: First stage: the furnace gas temperature is set to 300℃, the heating time is set to 15 minutes, and the furnace gas temperature is maintained at 300℃ for 45 minutes. After the time is up, the next stage begins. Second stage: the furnace gas temperature is set to 580℃, the heating time is set to 30 minutes, and the furnace gas temperature remains unchanged after reaching 580℃. When the aluminum coil metal temperature reaches 550℃, the timing starts, and the next stage begins. Third stage: after the timing is up for 3 hours, the coil is removed from the furnace and air-cooled. After cooling to 50℃, it is transferred to the cold rolling mill for the third cold rolling production.

[0033] The third cold rolling process resulted in a work roll crown of 0.0050 mm, a work roll roughness of 0.50 μm, and a cold roll exit thickness of 0.9 mm. The upper and lower tension rolls were opened and not used, as were the coloring rolls. The uncoiling tension was 1.1 kg / mm.2 After the rolling speed is increased to 720 m / min, it is maintained at a constant speed, and the rolling oil temperature is 32℃. After the third cold rolling is completed, it is transferred to the cooling zone for air cooling until the metal temperature is ≤50℃, and then transferred to the rewinding machine for edge trimming.

[0034] The semi-finished product is trimmed at a rewinding mill to a width of 1980mm at a trimming speed of 200m / min. It is then fed into the tension rolls but not into the winding and flattening rolls for production. After trimming, it is transferred to a cold rolling mill for a fourth cold rolling.

[0035] The fourth cold rolling process resulted in a work roll crown of 0.0050 mm, a work roll roughness of 0.52 μm, and a cold roll exit thickness of 0.45 mm. The upper and lower tension rolls and the coloring rolls were put into operation. The rolling speed was increased to 880 m / min and then maintained at a constant speed. The rolling oil temperature was 34°C. After the fourth cold rolling process, the process transitioned to the fifth cold rolling process.

[0036] In the fifth cold rolling process, the work roll crown was 0.0051 mm, the work roll roughness was 0.52 μm, and the cold rolling exit thickness was 0.22 mm. The upper and lower tension rolls and the coloring rolls were put into use. The rolling speed was increased to 680 m / min and then maintained at a constant speed. The rolling oil temperature was 35°C. After the fifth cold rolling, the coils were transferred to a recoiling mill for edge trimming to produce finished aluminum coils.

[0037] The finished product is trimmed at a rewinding machine to a width of 1960mm at a trimming speed of 440m / min. It is fed into the tension rollers but not into the winding and flattening rollers for production. After trimming, it is transferred to the foil rolling workshop for foil rolling or to the packaging area for packaging and warehousing.

[0038] The cold-rolled aluminum coils produced in this embodiment exhibit excellent surface quality and pinhole index after being processed into finished battery foils with a thickness of 0.013 mm. No quality complaints were received from downstream manufacturers after the battery foils were shipped to them. Statistics show that the yield rate was 70.3% from the start of electrolytic aluminum molten metal feeding to the warehousing of the battery foils.

[0039] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for producing cold-rolled aluminum coils for battery aluminum foil, characterized in that, Includes the following steps: Cast-rolled coil incoming material → First cold rolling to 4mm → Second cold rolling to 2.2mm → Annealing in an annealing furnace → Cooling → Third cold rolling to 0.9mm → Semi-finished product rerolling and edge trimming → Fourth cold rolling to 0.45mm → Fifth cold rolling to 0.22-0.24mm → Finished product rerolling and edge trimming → Transferred to foil rolling workshop; The requirements for the above cold rolling steps are as follows: The mechanical crown of the cold rolling work roll is 0.005±0.002mm, and the surface roughness Ra is 0.5±0.02um; the crown of the cast-rolled coil is required to be 0.2-0.4%. During the first and third cold rolling processes, no tension rolls or coloring rolls are used, and the uncoiling tension is 1.0 ± 0.1 kg / mm. 2 Rolling oil is sprayed onto the surface of the inlet guide roll at a rate of 0.5-1.0 liters per second. Tension rolls and coloring rolls are added during the second, fourth, and fifth cold rolling processes. During the second cold rolling, the coiling tension is 1.6 ± 0.1 kg / mm. 2 ; During the first cold rolling, the rolling speed was 400-450 m / min and the rolling oil temperature was 30±1℃; during the second cold rolling, the rolling speed was 550-600 m / min and the rolling oil temperature was 32±1℃; during the third cold rolling, the rolling speed was 700-750 m / min and the rolling oil temperature was 32±1℃; during the fourth cold rolling, the rolling speed was 850-900 m / min and the rolling oil temperature was 35±1℃; during the fifth cold rolling, the rolling speed was 550-700 m / min and the rolling oil temperature was 35±1℃. The requirements for the above rewinding and trimming steps are as follows: The cutting speed of the semi-finished product rewinding and trimming is 200-350m / min. It is fed into the first set of tension rollers, but not into the second set of tension rollers or the winding and flattening rollers. The cutting speed for rewinding and trimming the finished product is 300-550 m / min. The product is fed into the first and second sets of tensioning rollers, but not into the winding and flattening rollers.

2. The method for producing cold-rolled aluminum coils for battery aluminum foil according to claim 1, characterized in that, The requirements for the annealing furnace annealing step are as follows: Drill a thermocouple hole 30-40mm deep at a point 50mm away from the steel sleeve on the end face of the aluminum coil, and insert a thermocouple to measure the temperature of the aluminum coil metal. The annealing process in the furnace is divided into three stages. In the first stage, the furnace gas temperature is set to 300℃, and the heating time is set to 15 minutes. After the furnace gas temperature reaches 300℃, it is maintained for 45 minutes. After the time is up, the process proceeds to the next stage. In the second stage, the furnace gas temperature is set to 580℃, and the heating time is set to 30 minutes. After the furnace gas temperature reaches 580℃, it remains unchanged. When the temperature of the aluminum coil reaches 550℃, the timing starts, and the process proceeds to the next stage. In the third stage, after 3 hours of timing, the coil is removed from the furnace and cooled. The cooling process involves natural air cooling for the first 2 hours after removal from the furnace, followed by forced air cooling using a fan after 2 hours.

3. The method for producing cold-rolled aluminum coils for battery aluminum foil according to claim 1, characterized in that, During the first and third cold rolling processes, without engaging the tension rolls and coloring rolls, after establishing tension, the distance between the aluminum strip and the upper and lower tension rolls, coloring rolls, and the entry shear blade should not be less than 3mm.

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