A method for homogenizing the corrosion structure of a cathode foil based on synergistic regulation of deformation and annealing

Abstract

This invention discloses a method for homogenizing the corrosion structure of cathode foil based on deformation-annealing synergistic control, comprising the following steps: S1: Selecting high-purity aluminum foil as raw material and performing surface pretreatment; S2: Performing multi-pass rolling deformation on the aluminum foil, controlling the cumulative rolling deformation to be 60%–95%; S3: Performing intermediate annealing on the rolled aluminum foil; S4: Performing secondary rolling deformation on the intermediate annealed aluminum foil; S5: Performing finished product annealing on the secondary rolled aluminum foil; S6: Performing electrochemical corrosion treatment on the finished annealed aluminum foil to obtain a cathode foil with a uniform corrosion pit structure. This invention adopts a deformation-annealing synergistic control mode, establishing a quantitative linkage between deformation and annealing temperature, overcoming the drawbacks of independently controlling rolling and annealing in traditional processes, improving the problems of dislocation and uneven grain distribution within the aluminum foil, avoiding defects such as shear bands and differential textures, and achieving overall microstructure homogenization.

Description

Technical Field

[0001] This invention relates to the field of cathode foil production technology, and specifically to a method for homogenizing the corrosion structure of cathode foil based on deformation-annealing synergistic regulation. Background Technology

[0002] Aluminum electrolytic capacitors are among the most widely used passive components in electronic circuits. The uniformity of the surface corrosion pits on the cathode foil, as its core component, directly determines the capacitor's equivalent series resistance (ESR), specific capacitance, and lifespan. In solid-state aluminum electrolytic capacitors, the uniform corrosion pits on the cathode foil surface serve as the template structure for the subsequent formation of the mesoporous alumina dielectric layer. The consistency of pit depth, diameter, and area distribution is crucial for ensuring uniform dielectric layer thickness and stable dielectric properties.

[0003] Currently, the homogenization of corrosion pits in cathode foils mainly relies on the control of the aluminum foil's microstructure, which is jointly determined by rolling deformation and annealing processes. In existing technologies, rolling deformation and annealing are typically optimized as two independent processes: on the one hand, dislocations and grain fragmentation are introduced by controlling the number of rolling passes and the reduction rate; on the other hand, recrystallization is achieved through annealing temperature and holding time. However, these methods treat deformation and annealing separately, lacking a systematic study of their synergistic relationship.

[0004] Specifically, the existing technology has the following shortcomings: 1. Controlling rolling deformation alone is insufficient to guarantee the uniformity of microstructure. When the cumulative deformation is large (≥70%), the dislocation density distribution inside the aluminum foil is uneven, which easily forms shear bands and local texture differences, resulting in uneven recrystallization during subsequent annealing, and ultimately corrosion pits with varying depths and large diameter dispersion.

[0005] 2. Individually controlling the annealing process cannot compensate for the structural defects caused by deformation. Even with high-precision annealing furnace control of temperature and time, if the amount of preceding deformation is not precisely matched with the annealing parameters, a mixed structure will still appear with some areas of insufficient recrystallization (coarse grains) and some areas of excessive recrystallization (fine grains). The coefficient of variation of the corrosion pit area is usually >0.35, which is difficult to meet the uniformity requirements (coefficient of variation ≤0.2) of high-end capacitors.

[0006] 3. Lack of a quantitative synergistic matching model among the three parameters: deformation amount, annealing temperature, and annealing time. Existing processes rely heavily on trial and error based on experience, and have not established a linkage control mechanism between deformation parameters and annealing parameters. This results in significant fluctuations in the uniformity of corrosion pits across different batches and specifications of products, leading to poor batch consistency.

[0007] Therefore, it is necessary to invent a method for homogenizing the corrosion structure of cathode foil based on deformation-annealing synergistic regulation to solve the above problems. Summary of the Invention

[0008] The purpose of this invention is to provide a method for homogenizing the corrosion structure of cathode foil based on deformation-annealing synergistic regulation, so as to solve the problems in the above-mentioned technology.

[0009] To achieve the above objectives, the present invention provides the following technical solution: a method for homogenizing the corrosion structure of cathode foil based on deformation-annealing synergistic regulation, comprising the following operational steps: S1: High-purity aluminum foil is selected as the raw material and its surface is pretreated; S2: Perform multi-pass rolling deformation on the aluminum foil, controlling the cumulative rolling deformation to be 60%–95%; S3: Perform intermediate annealing on the rolled aluminum foil; S4: Perform secondary rolling deformation on the aluminum foil after intermediate annealing; S5: Perform finished product annealing on the aluminum foil after secondary rolling; S6: Perform electrochemical etching treatment on the finished annealed aluminum foil to obtain a cathode foil with a uniform corrosion pit structure.

[0010] Preferably, in step S1, the surface pretreatment is performed sequentially using an alkaline washing device and an electrolytic polishing device. The alkaline washing device uses a NaOH aqueous solution with a mass concentration of 2% to 5%, a temperature of 50 to 70°C, and a treatment time of 30 to 90 seconds. The electrolytic polishing device uses a phosphoric acid-sulfuric acid mixed electrolyte, a voltage of 10 to 30V, and a treatment time of 10 to 60 seconds to remove the oxide film and work-hardened layer from the aluminum foil surface.

[0011] Preferably, in step S2, a 20-roll mill is used for rolling, the reduction rate per pass is controlled at 10% to 25%, the rolling speed is 50 to 500 m / min, the rolling temperature is controlled at 20 to 80°C, and the cumulative rolling deformation is precisely controlled by adjusting the number of rolling passes and the reduction rate per pass, with the total deformation being 60% to 95%.

[0012] Preferably, in step S3, a continuous annealing furnace is used for intermediate annealing treatment. The annealing temperature is 280-400℃, the annealing time is 30-120s, and the protective atmosphere is nitrogen gas with a purity of ≥99.99% or a mixture of nitrogen and hydrogen gas, with hydrogen accounting for 3%-10% of the volume. After annealing, the aluminum foil undergoes partial recrystallization, providing a uniform deformation matrix for secondary rolling.

[0013] Preferably, the deformation-annealing synergistic matching relationship is satisfied between steps S2 and S3, and between steps S4 and S5. Specifically, for every 10% increase in the cumulative rolling deformation, the intermediate annealing temperature is increased by 15-25°C, and the finished product annealing temperature is increased by 10-20°C, so as to ensure that a uniform recrystallized structure can be obtained under different deformation amounts.

[0014] Preferably, in step S4, a 20-roll mill, the same as in step S2, is used for secondary rolling. The cumulative deformation of the secondary rolling accounts for 30% to 60% of the total deformation. The rolling speed is 100 to 400 m / min, and the rolling temperature is controlled at 20 to 60°C. The secondary rolling further breaks down the grains and introduces a uniform dislocation density.

[0015] Preferably, in step S5, a bell-type annealing furnace is used for annealing the finished product. The annealing temperature is 350-450℃, the holding time is 2-8h, the protective atmosphere is nitrogen, and the cooling method is furnace cooling or controlled cooling at a rate of 10-50℃ / h, so that the aluminum foil obtains a uniform equiaxed grain structure with complete recrystallization, and the grain size is controlled at 5-30μm.

[0016] Preferably, in step S6, an electrochemical corrosion is performed using a spray corrosion device or an immersion corrosion tank. The corrosion solution is an aqueous solution of hydrochloric acid or a mixed acid solution of hydrochloric acid and nitric acid. The mass concentration of hydrochloric acid is 10% to 30%, the corrosion temperature is 40 to 70°C, and the corrosion time is adjusted according to the depth of the target corrosion pit. A DC power supply is used during the corrosion process, with a current density of 10 to 100 mA / cm².

[0017] Preferably, in step S6, the cathode foil obtained after etching has a corrosion pit depth deviation of ≤±10%, a corrosion pit diameter deviation of ≤±15%, and a coefficient of variation of corrosion pit area distribution of ≤0.2, which meets the uniformity requirements of cathode foil for solid aluminum electrolytic capacitors.

[0018] The technical effects and advantages provided by the present invention in the above technical solution are as follows: 1. By adopting a deformation-annealing synergistic control mode, a quantitative linkage relationship between deformation amount and annealing temperature is established, breaking the drawback of independent control of rolling and annealing in traditional processes. This effectively improves the problems of dislocation and uneven grain distribution inside aluminum foil, avoids defects such as shear bands and differential texture, and achieves overall uniformity of microstructure. 2. Through a combination of two rolling processes and graded annealing, aluminum foil can form uniform equiaxed grains with controllable size, which greatly improves the synchronicity of subsequent electrochemical corrosion reactions, resulting in cathode foil with excellent uniformity in the size and distribution of corrosion pits. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall operation process of the present invention. Detailed Implementation

[0020] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0021] This invention provides, for example Figure 1 The method for homogenizing the corrosion structure of a cathode foil based on deformation-annealing synergistic regulation, as shown, includes the following steps: S1: High-purity aluminum foil is selected as the raw material and its surface is pretreated; S2: Perform multi-pass rolling deformation on the aluminum foil, controlling the cumulative rolling deformation to be 60%–95%; S3: Perform intermediate annealing on the rolled aluminum foil; S4: Perform secondary rolling deformation on the aluminum foil after intermediate annealing; S5: Perform finished product annealing on the aluminum foil after secondary rolling; S6: Perform electrochemical etching treatment on the finished annealed aluminum foil to obtain a cathode foil with a uniform corrosion pit structure.

[0022] In one aspect of this embodiment, in step S1, the surface pretreatment is performed sequentially using an alkaline washing device and an electrolytic polishing device. The alkaline washing device uses a NaOH aqueous solution with a mass concentration of 2% to 5%, a temperature of 50 to 70°C, and a treatment time of 30 to 90 seconds. The electrolytic polishing device uses a phosphoric acid-sulfuric acid mixed electrolyte, a voltage of 10 to 30V, and a treatment time of 10 to 60 seconds to remove the oxide film and work-hardened layer from the aluminum foil surface.

[0023] In step S2, a 20-roll mill is used for rolling. The reduction rate per pass is controlled at 10% to 25%, the rolling speed is 50 to 500 m / min, and the rolling temperature is controlled at 20 to 80°C. The cumulative rolling deformation is precisely controlled by adjusting the number of rolling passes and the reduction rate per pass, and the total deformation is 60% to 95%.

[0024] In step S3, intermediate annealing is performed using a continuous annealing furnace at a temperature of 280–400°C and a time of 30–120 seconds. The protective atmosphere is nitrogen or a mixture of nitrogen and hydrogen with a purity of ≥99.99%, and the hydrogen volume percentage is 3%–10%. After annealing, the aluminum foil undergoes partial recrystallization, providing a uniform deformation matrix for secondary rolling.

[0025] The deformation-annealing synergistic matching relationship is satisfied between steps S2 and S3, and between steps S4 and S5. Specifically, for every 10% increase in the cumulative rolling deformation, the intermediate annealing temperature is increased by 15-25°C, and the finished product annealing temperature is increased by 10-20°C, so as to ensure that a uniform recrystallized structure can be obtained under different deformation amounts.

[0026] In step S4, a second rolling mill, the same as in step S2, is used for secondary rolling. The cumulative deformation of the second rolling accounts for 30% to 60% of the total deformation. The rolling speed is 100 to 400 m / min, and the rolling temperature is controlled at 20 to 60°C. The secondary rolling further breaks down the grains and introduces a uniform dislocation density.

[0027] In step S5, a bell-type annealing furnace is used for annealing the finished product. The annealing temperature is 350-450℃, the holding time is 2-8h, the protective atmosphere is nitrogen, and the cooling method is furnace cooling or controlled cooling at a rate of 10-50℃ / h, so that the aluminum foil obtains a uniform equiaxed grain structure with complete recrystallization, and the grain size is controlled at 5-30μm.

[0028] In step S6, electrochemical corrosion is carried out using a spray corrosion device or an immersion corrosion tank. The corrosion solution is an aqueous solution of hydrochloric acid or a mixed acid solution of hydrochloric acid and nitric acid. The mass concentration of hydrochloric acid is 10% to 30%, the corrosion temperature is 40 to 70°C, and the corrosion time is adjusted according to the depth of the target corrosion pit. A DC power supply is used during the corrosion process, with a current density of 10 to 100 mA / cm².

[0029] In step S6, the cathode foil obtained after corrosion has a corrosion pit depth deviation of ≤±10%, a corrosion pit diameter deviation of ≤±15%, and a corrosion pit area distribution variation coefficient of ≤0.2, which meets the uniformity requirements for cathode foil used in solid aluminum electrolytic capacitors.

[0030] Working principle of this invention: Refer to the instruction manual appendix Figure 1 When using this invention, first select high-purity aluminum foil raw material, and then complete the surface pretreatment by alkaline washing and electrolytic polishing in sequence to remove the oxide film and work hardening layer on the aluminum foil surface and eliminate the interference of surface defects on subsequent rolling and corrosion. Then, a multi-pass rolling process is carried out to control the cumulative rolling deformation of the aluminum foil at 60% to 95%, and dislocations are introduced through large deformation to initially break the grains. Next, intermediate annealing is carried out, and partial recrystallization of aluminum foil is achieved by relying on nitrogen protective atmosphere, which optimizes the uniformity of matrix structure and creates a stable and consistent deformation basis for secondary rolling. Then, a second rolling process is carried out to further refine the grains and introduce a uniformly distributed dislocation structure. At the same time, the deformation-annealing synergistic matching rule is strictly followed: for every 10% increase in the cumulative deformation of rolling, the intermediate annealing temperature is increased by 15-25℃ and the finished product annealing temperature is increased by 10-20℃. This allows the deformation and annealing process parameters to be precisely linked, solving the problem of uneven microstructure caused by the separation of deformation and annealing in traditional processes. After the second rolling is completed, the finished product is annealed and kept at a high temperature for a long time under nitrogen protection and cooled at a controlled rate to allow the aluminum foil to recrystallize completely and form uniform equiaxed grains with a size of 5 to 30 μm, thus ensuring the consistency of corrosion conditions from the microstructure level. Finally, electrochemical corrosion was carried out on the annealed aluminum foil. The uniform grain and dislocation structure allowed the corrosion reaction to proceed simultaneously, ultimately resulting in a cathode foil with satisfactory corrosion pit depth, diameter, and area distribution.

[0031] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for homogenizing the corrosion structure of cathode foil based on deformation-annealing synergistic regulation, characterized in that, The following steps are included: S1: High-purity aluminum foil is selected as the raw material and its surface is pretreated; S2: Perform multi-pass rolling deformation on the aluminum foil, controlling the cumulative rolling deformation to be 60%–95%; S3: Perform intermediate annealing on the rolled aluminum foil; S4: Perform secondary rolling deformation on the aluminum foil after intermediate annealing; S5: Perform finished product annealing on the aluminum foil after secondary rolling; S6: Electrochemical corrosion treatment is performed on the finished annealed aluminum foil to obtain a cathode foil with a uniform corrosion pit structure.

2. The method for homogenizing the corrosion structure of cathode foil based on deformation-annealing synergistic regulation according to claim 1, characterized in that: In step S1, the surface pretreatment is carried out by sequentially using an alkaline washing device and an electrolytic polishing device. The alkaline washing device uses a NaOH aqueous solution with a mass concentration of 2% to 5%, a temperature of 50 to 70°C, and a treatment time of 30 to 90 seconds. The electrolytic polishing device uses a phosphoric acid-sulfuric acid mixed electrolyte, a voltage of 10 to 30V, and a treatment time of 10 to 60 seconds to remove the oxide film and work-hardened layer from the aluminum foil surface.

3. The method for homogenizing the corrosion structure of cathode foil based on deformation-annealing synergistic regulation according to claim 1, characterized in that: In step S2, a 20-roll mill is used for rolling. The reduction rate per pass is controlled at 10% to 25%, the rolling speed is 50 to 500 m / min, and the rolling temperature is controlled at 20 to 80°C. The cumulative rolling deformation is precisely controlled by adjusting the number of rolling passes and the reduction rate per pass, and the total deformation is 60% to 95%.

4. The method for homogenizing the corrosion structure of cathode foil based on deformation-annealing synergistic regulation according to claim 1, characterized in that: In step S3, intermediate annealing is performed using a continuous annealing furnace at a temperature of 280–400°C and a time of 30–120 seconds. The protective atmosphere is nitrogen or a mixture of nitrogen and hydrogen with a purity of ≥99.99%, and the hydrogen volume percentage is 3%–10%. After annealing, the aluminum foil undergoes partial recrystallization, providing a uniform deformation matrix for secondary rolling.

5. The method for homogenizing the corrosion structure of cathode foil based on deformation-annealing synergistic regulation according to claim 1, characterized in that: The deformation-annealing synergistic matching relationship is satisfied between steps S2 and S3, and between steps S4 and S5. Specifically, for every 10% increase in the cumulative rolling deformation, the intermediate annealing temperature is increased by 15-25°C, and the finished product annealing temperature is increased by 10-20°C, so as to ensure that a uniform recrystallized structure can be obtained under different deformation amounts.

6. The method for homogenizing the corrosion structure of cathode foil based on deformation-annealing synergistic regulation according to claim 1, characterized in that: In step S4, a second rolling mill, the same as in step S2, is used for secondary rolling. The cumulative deformation of the second rolling accounts for 30% to 60% of the total deformation. The rolling speed is 100 to 400 m / min, and the rolling temperature is controlled at 20 to 60°C. The secondary rolling further breaks down the grains and introduces a uniform dislocation density.

7. The method for homogenizing the corrosion structure of cathode foil based on deformation-annealing synergistic regulation according to claim 1, characterized in that: In step S5, a bell-type annealing furnace is used for annealing the finished product. The annealing temperature is 350-450℃, the holding time is 2-8h, the protective atmosphere is nitrogen, and the cooling method is furnace cooling or controlled cooling at a rate of 10-50℃ / h, so that the aluminum foil obtains a uniform equiaxed grain structure with complete recrystallization, and the grain size is controlled at 5-30μm.

8. The method for homogenizing the corrosion structure of cathode foil based on deformation-annealing synergistic regulation according to claim 1, characterized in that: In step S6, electrochemical corrosion is carried out using a spray corrosion device or an immersion corrosion tank. The corrosion solution is an aqueous solution of hydrochloric acid or a mixed acid solution of hydrochloric acid and nitric acid. The mass concentration of hydrochloric acid is 10% to 30%, the corrosion temperature is 40 to 70°C, and the corrosion time is adjusted according to the depth of the target corrosion pit. A DC power supply is used during the corrosion process, with a current density of 10 to 100 mA / cm².

9. The method for homogenizing the corrosion structure of cathode foil based on deformation-annealing synergistic regulation according to claim 1, characterized in that: In step S6, the cathode foil obtained after corrosion has a corrosion pit depth deviation of ≤±10%, a corrosion pit diameter deviation of ≤±15%, and a corrosion pit area distribution variation coefficient of ≤0.2, which meets the uniformity requirements for cathode foil used in solid aluminum electrolytic capacitors.

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