A process for the hot rolling of low voltage anode foil for aluminum electrolytic capacitors

Abstract

The application discloses a kind of aluminum electrolytic capacitor low-voltage anode foil hot rolling preparation process, it is related to low-voltage anode foil preparation field, to solve the problem of the service life of low-voltage anode foil being lower in prior art in the existing low-voltage anode foil uniformity being poor, surface is easy to corrode when using in special environment, leading to.The low-voltage anode foil hot rolling preparation process steps are: S1 raw material selection, using high-purity aluminum ingot with purity ≥99.995% as main raw material and adding copper, magnesium, silicon three trace elements;S2 mixing stirring;S3 smelting and refining, S4 semi-continuous casting;S5 homogenization treatment;S6 hot rolling process, adopt the strategy of "big-small-big" reduction, and the total reduction amount of hot rolling is controlled between 78% and 89%, high-purity aluminum ingot is used as main raw material, and the addition amount of copper, magnesium, silicon and other trace elements is accurately controlled, combined with fine hot rolling, cold rolling and foil rolling process, the mechanical properties and corrosion resistance of the material are enhanced, effectively solve the problem that low-voltage anode foil is easy to corrode in special environment.

Description

Technical Field

[0001] This invention relates to the field of low-voltage anode foil preparation, specifically a hot rolling process for preparing low-voltage anode foil for aluminum electrolytic capacitors. Background Technology

[0002] Low-voltage anode foil is a crucial component of electrolytic capacitors, specifically referring to the aluminum foil material used as the anode. This aluminum foil undergoes a series of precise processing steps, including etching and anodizing, ultimately transforming it into a formed foil with specific functions. In electrolytic capacitors, the primary function of low-voltage anode foil is to store charge; its performance directly affects the capacitor's capacitance, losses, and lifespan. According to voltage classification standards, the operating voltage range of low-voltage anode foil is typically between 7.7V and 170V, suitable for various low-voltage electronic devices. Its unique sponge-like corrosion morphology, coupled with a precisely controlled corrosion process, significantly increases the surface area of ​​the aluminum foil, thereby improving the capacitor's capacitance. Furthermore, low-voltage anode foil possesses excellent conductivity and chemical stability, maintaining stable performance even in harsh operating environments. During capacitor manufacturing, the quality and technological level of the low-voltage anode foil have a decisive impact on capacitor performance. Therefore, when selecting low-voltage anode foil, its material composition, processing technology, and performance parameters must be strictly considered to ensure the quality and reliability of the capacitor.

[0003] Existing low-voltage anode foils have poor uniformity and are prone to surface corrosion when used in special environments, resulting in a short service life. Therefore, there is an urgent need in the market to develop a hot rolling process for preparing low-voltage anode foils for aluminum electrolytic capacitors to help solve the existing problems. Summary of the Invention

[0004] The purpose of this invention is to provide a hot rolling process for preparing low-voltage anode foil for aluminum electrolytic capacitors, in order to solve the problems mentioned in the background art, such as poor uniformity of existing low-voltage anode foil, easy surface corrosion when used in special environments, and low service life of low-voltage anode foil.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a hot rolling process for preparing low-voltage anode foil for aluminum electrolytic capacitors, characterized in that the hot rolling process steps for preparing low-voltage anode foil are as follows:

[0006] S1 uses high-purity aluminum ingots with a purity of ≥99.995% as the main raw material and adds three trace elements: copper, magnesium, and silicon.

[0007] S2 mixing and stirring: high-purity aluminum ingots are fined into particles by a crushing device, and then copper, magnesium, and silicon raw materials are mixed evenly with granular aluminum raw materials by a stirring device.

[0008] S3 Smelting and Refining: The mixed raw materials are added into a high-frequency induction smelting furnace to mix and smelt the main materials and trace elements. During smelting, flotation, filtration, and inert gas purging are used to remove impurities from the melt.

[0009] After S4 semi-continuous casting and refining, the raw materials are cast into shape by a vibration casting device. During casting, electromagnetic stirring is used simultaneously to optimize the internal structure of the ingot, reduce segregation and porosity, and strictly control parameters such as casting speed and cooling water volume.

[0010] S5 homogenization treatment: After the ingot is cast, it is placed in the homogenization device for high-temperature homogenization to ensure that the alloying elements are fully diffused. At the same time, nitrogen or argon is introduced into the homogenization device to homogenize the ingot under the protection of nitrogen or argon.

[0011] The S6 hot rolling process involves hot rolling the ingot using a hot rolling device and adopting a "large-small-large" reduction strategy: the initial pass uses a larger reduction of ≥16%, the intermediate pass reduces the reduction by ≤10%, and the final pass increases the reduction by ≥12%. The total hot rolling reduction is controlled between 78% and 89%, and is completed in 22 to 25 passes.

[0012] S7 cold rolling and foil rolling are carried out at room temperature, with the total reduction rate controlled between 22% and 28% to maintain the surface smoothness of the strip. After cold rolling, a high-precision foil rolling mill is used for foil rolling, and the final foil thickness is controlled between 0.08mm and 0.10mm.

[0013] S8 annealing involves annealing the foil sheets after they are wrapped in nitrogen or argon under a protective atmosphere, and then cooling them using a rapid cooling technique such as forced air cooling or water mist cooling.

[0014] S9 surface treatment first uses an environmentally friendly etching solution to micro-etch the foil surface to increase the surface area, and then forms a dense oxide film on the foil surface through electrolysis.

[0015] Preferably, in the S1 raw material selection, the amount of copper added is 0.02%-0.12%, the amount of magnesium added is 0.01%-0.1%, and the amount of silicon added is 0.04%-0.25%.

[0016] Preferably, the homogenization temperature in the S5 homogenization process is set to 595°C to 615°C, and the holding time is 9 to 11 hours.

[0017] Preferably, in the S6 hot rolling process, the hot rolling inlet temperature of the hot rolling unit is maintained at 425°C to 435°C, and the hot rolling unit outlet temperature is not lower than 350°C.

[0018] Preferably, the S6 hot rolling process uses a high-efficiency water-based lubricant and simultaneously employs an intelligent spray cooling device.

[0019] Preferably, in the S7 cold rolling and foil rolling process, a high-precision foil rolling mill is used to precisely control the roll gap ≤0.012mm and the rolling speed ≤1000m / min, achieving a thickness uniformity ≤±2.5%.

[0020] Preferably, the annealing temperature in the S8 annealing is selected to be 365°C to 380°C, and the holding time is 7 to 10 hours to eliminate work hardening.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] (1) In this invention, high-purity aluminum ingots are used as the main raw material, and the addition of trace elements such as copper, magnesium, and silicon is precisely controlled, which effectively improves the composition distribution of the material. Combined with refined hot rolling, cold rolling, and foil rolling processes, especially the "large-small-large" pressing strategy adopted in the hot rolling process, the microstructure of the material is further optimized, significantly improving the uniformity and density of the low-pressure anode foil. This optimization not only reduces internal defects and porosity of the material, but also enhances the mechanical properties and corrosion resistance of the material, thereby effectively solving the problem of easy corrosion and short service life of existing low-pressure anode foils in special environments.

[0023] (2) In this invention, a high-efficiency water-based lubricant and an intelligent spray cooling device are used in the hot rolling process. The application of these innovative technologies not only reduces friction loss and energy consumption during the rolling process, but also optimizes the microstructure of the material, such as grain refinement and uniform structure. This optimization of the microstructure helps to improve the mechanical properties and surface quality of the low-voltage anode foil, further extending the service life of the capacitor. At the same time, by precisely controlling the reduction and temperature during the hot rolling process, the material properties are precisely controlled, meeting the high-performance requirements of the capacitor for the low-voltage anode foil.

[0024] (3) In this invention, the work hardening phenomenon is eliminated and the plasticity of the material is restored through strict annealing and surface treatment processes. At the same time, a dense oxide film is formed on the surface of the foil. This film not only improves the corrosion resistance of the low-voltage anode foil, but also enhances its wettability with the electrolyte. This improvement in wettability helps the capacitor to store and release charge more effectively during charging and discharging, thereby improving the electrostatic capacity and stability of the capacitor. In addition, this dense oxide film also plays a role in protecting the substrate, further extending the service life of the low-voltage anode foil. Attached Figure Description

[0025] Figure 1 This is a flowchart illustrating the hot rolling process for preparing low-voltage anode foil for aluminum electrolytic capacitors according to the present invention. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0027] Please see Figure 1 The present invention provides an embodiment of a hot rolling process for preparing low-voltage anode foil for aluminum electrolytic capacitors, characterized by comprising the following steps:

[0028] S1 Raw Material Selection: High-purity aluminum ingots with a purity of ≥99.995% are used as the main raw material, with the addition of three trace elements: copper, magnesium, and silicon. The addition amount of copper is 0.02%-0.12%, magnesium is 0.01%-0.1%, and silicon is 0.04%-0.25%. This raw material ratio not only improves the corrosion resistance, strength, and processability of the material, but also lays a solid foundation for the optimization of subsequent processes.

[0029] S2 Mixing and Stirring: High-purity aluminum ingots are fined into particles by a crushing device, and then copper, magnesium, and silicon raw materials are mixed evenly with granular aluminum raw materials by a high-efficiency stirring device.

[0030] S3 Smelting and Refining: The mixed raw materials are added into a high-frequency induction melting furnace to mix and melt the main materials and trace elements. During the smelting process, flotation, filtration, and inert gas purging are used to remove impurities from the melt and improve the purity of the alloy.

[0031] S4 Semi-continuous Casting: The refined raw materials are cast into shape by a vibration casting device. During casting, electromagnetic stirring is used simultaneously to optimize the internal structure of the ingot, reduce segregation and porosity, and strictly control parameters such as casting speed and cooling water volume to ensure ingot quality.

[0032] S5 Homogenization Treatment: The ingot is placed inside the homogenization device for high-temperature homogenization treatment. The homogenization treatment temperature is set to 595℃ to 615℃, and the holding time is 9 to 11 hours to ensure that the alloying elements are fully diffused and improve the uniformity and stability of the material. At the same time, nitrogen or argon is introduced into the homogenization device during the homogenization treatment process so that the ingot is homogenized under the protection of nitrogen or argon to prevent oxidation.

[0033] S6 hot rolling process: The ingot is hot rolled using a hot rolling mill. The hot rolling mill inlet temperature is maintained at 425℃ to 435℃, and the hot rolling mill outlet temperature is not lower than 350℃ to ensure that the material has good plasticity and deformation capacity. A "large-small-large" reduction strategy is adopted, that is, the initial pass uses a large reduction of ≥16% to promote grain refinement, the intermediate pass reduces the reduction by ≤10% to maintain plate shape stability, and the final pass increases the reduction by ≥12% to optimize surface quality. The total hot rolling reduction is controlled between 78% and 89%, and is completed in 22 to 25 passes. At the same time, a high-efficiency water-based lubricant is used during the hot rolling process to reduce friction and energy consumption. A smart spray cooling device is used simultaneously to adjust the cooling intensity in real time according to the rolling temperature to avoid overheating and coarsening of the microstructure.

[0034] S7 Cold Rolling and Foil Rolling: Cold rolling and foil rolling are carried out at room temperature, with the total reduction rate controlled between 22% and 28% to maintain the surface smoothness of the strip. After cold rolling, a high-precision foil rolling mill is used for foil rolling, with precise control of the roll gap ≤0.012mm and the rolling speed ≤1000m / min to achieve thickness uniformity ≤±2.5%, and the final foil thickness controlled between 0.08mm and 0.10mm.

[0035] S8 Annealing: The foil after rolling is annealed under nitrogen or argon protection. The annealing temperature is selected from 365℃ to 380℃, and the holding time is 7 to 10 hours to eliminate work hardening, restore the plasticity of the material, and use rapid cooling technology such as forced air cooling or water mist cooling to avoid grain growth.

[0036] S9 Surface Treatment: First, an environmentally friendly etching solution is used to micro-etch the surface of the foil. This step not only increases the surface area of ​​the foil and improves its wettability with the electrolyte, but also forms a dense oxide film on the foil surface through electrolysis. This oxide film not only further improves the corrosion resistance of the foil, but also significantly enhances its electrochemical performance, providing a more reliable quality assurance for the low-voltage anode foil of aluminum electrolytic capacitors.

[0037] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A hot rolling process for preparing low-voltage anode foil for aluminum electrolytic capacitors, characterized in that, The hot rolling process for preparing low-pressure anode foil is as follows: S1 Raw Material Selection: High-purity aluminum ingots with a purity of ≥99.995% are used as the main raw material, with the addition of three trace elements: copper, magnesium, and silicon. S2 Mixing and Stirring: High-purity aluminum ingots are fined into particles by a crushing device, and then copper, magnesium, and silicon raw materials are mixed evenly with granular aluminum raw materials by a stirring device; S3 Smelting and Refining: The mixed raw materials are added into a high-frequency induction smelting furnace to mix and smelt the main materials and trace elements. During smelting, flotation, filtration and inert gas purging are used to remove impurities from the melt. S4 Semi-continuous Casting: After refining, the raw materials are cast into shape by a vibration casting device. During casting, electromagnetic stirring is used simultaneously to optimize the internal structure of the ingot, reduce segregation and porosity, and strictly control the casting speed and cooling water parameters. S5 Homogenization treatment: After casting, the ingot is placed inside the homogenization device for high-temperature homogenization to ensure that the alloying elements are fully diffused. At the same time, nitrogen or argon is introduced into the homogenization device to homogenize the ingot under the protection of nitrogen or argon. S6 hot rolling process: The ingot is hot rolled using a hot rolling device, and a "large-small-large" reduction strategy is adopted: the initial pass uses a larger reduction amount ≥16%, the intermediate pass reduces the reduction amount ≤10%, and the final pass increases the reduction amount again ≥12%. The total hot rolling reduction amount is controlled between 78% and 89%, and is completed in 22 to 25 passes. S7 cold rolling and foil rolling: carried out at room temperature, with the total reduction rate controlled between 22% and 28% to maintain the surface smoothness of the strip. After cold rolling, a high-precision foil rolling mill is used for foil rolling, and the final foil thickness is controlled between 0.08mm and 0.10mm. S8 Annealing: The foil sheet after foil rolling is annealed under nitrogen or argon protection and cooled by rapid cooling technology such as forced air cooling or water mist cooling. S9 Surface Treatment: First, an environmentally friendly etching solution is used to micro-etch the foil surface to increase the surface area. Then, a dense oxide film is formed on the foil surface through electrolysis.

2. The hot rolling process for preparing low-voltage anode foil for aluminum electrolytic capacitors according to claim 1, characterized in that: The raw material S1 contains 0.02%-0.12% copper, 0.01%-0.1% magnesium, and 0.04%-0.25% silicon.

3. The hot rolling process for preparing low-voltage anode foil for aluminum electrolytic capacitors according to claim 1, characterized in that: The homogenization temperature in the S5 homogenization process is set to 595°C to 615°C, and the holding time is 9 to 11 hours.

4. The hot rolling process for preparing low-voltage anode foil for aluminum electrolytic capacitors according to claim 1, characterized in that: In the S6 hot rolling process, the hot rolling inlet temperature of the hot rolling unit is maintained at 425°C to 435°C, and the hot rolling unit outlet temperature is not lower than 350°C.

5. The hot rolling process for preparing low-voltage anode foil for aluminum electrolytic capacitors according to claim 1, characterized in that: The S6 hot rolling process uses a high-efficiency water-based lubricant and simultaneously employs an intelligent spray cooling device.

6. The hot rolling process for preparing low-voltage anode foil for aluminum electrolytic capacitors according to claim 1, characterized in that: The S7 cold rolling and foil rolling process employs a high-precision foil rolling mill, precisely controlling the roll gap to ≤0.012mm and the rolling speed to ≤1000m / min, achieving a thickness uniformity of ≤±2.5%.

7. The hot rolling process for preparing low-voltage anode foil for aluminum electrolytic capacitors according to claim 1, characterized in that: The S8 annealing process involves selecting an annealing temperature of 365°C to 380°C and a holding time of 7 to 10 hours to eliminate work hardening.

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