Cold-drawing manufacturing method of battery shell

Abstract

The invention discloses a cold-drawing manufacturing method of a battery shell, which comprises the following steps: 1) preparing and optimizing an aluminum alloy material which at least comprises the following components in percentage by mass: 0.3-1wt% of Ce, 0.3-1wt% of Mn, 0.1-1wt% of Si, 0.1-1wt% of Cu, 0.1-1wt% of Fe and the balance of Al; (2) extruding the aluminum alloy material obtained in the step (1) to form a cylindrical shell blank; (3) the shell blank is arranged on a core rod of a cold drawing die in a sleeving mode, the front end of the shell blank extends into a cold drawing cavity of the cold drawing die, and the size of the core rod is matched with the size of an inner cavity needed by the battery shell; and (4) the shell blank is pulled in the drawing direction, the core rod and the shell blank are made to move in the same direction in the drawing direction, and the whole shell blank penetrates out of the cold drawing cavity to form the battery shell. The battery shell prepared by the method has relatively high structural rigidity and bending resistance limit.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum alloy materials, and in particular to a cold drawing method for manufacturing a battery shell. Background Art

[0002] The rapid development of the new energy vehicle industry has put forward higher requirements on the performance of power batteries, especially stability and safety in extreme environments. During the charging and discharging process of power batteries, the thermal expansion and contraction of battery components will cause the shell to deform. This deformation is particularly significant in harsh environments such as high temperature and humidity, high altitude and high cold, which seriously affects the performance and service life of the battery. Therefore, improving the heat resistance and structural strength of the power battery shell has become the key to the current technological development.

[0003] Aluminum alloys are widely used in power battery housings due to their light weight, corrosion resistance and excellent mechanical properties. However, the protection effect of existing aluminum alloys in special operating environments, such as charge and discharge cycles and extreme climatic conditions, needs to be improved. In particular, the performance of existing materials still has room for improvement in terms of improving structural stiffness, bending limit, pressure resistance limit and thermal attenuation gradient. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the technical problem to be solved by the present invention is: to provide a cold drawing method for manufacturing a battery shell, wherein the battery shell manufactured by the method has strong structural rigidity and bending resistance limit.

[0005] In order to solve the above technical problems, a technical solution adopted by the present invention is: a cold drawing method for manufacturing a battery shell, comprising the following steps:

[0006] 1) taking an aluminum alloy material after configuration and optimization, wherein the aluminum alloy material comprises at least Al, Mn, Si, Cu, Fe and Ce, wherein the mass percentage of Ce is 0.3-1wt%;

[0007] 2) forming a cylindrical shell blank by extruding the aluminum alloy material in step 1);

[0008] 3) The housing blank is sleeved on a core rod of a cold drawing die, and the front end of the blank is extended into a cold drawing cavity of the cold drawing die, wherein the size of the core rod matches the size of the internal cavity required for the battery housing;

[0009] 4) Pulling the shell blank along the drawing direction, and moving the core rod in the same direction as the shell blank along the drawing direction, so that the shell blank is entirely drawn out of the cold drawing cavity to form a battery shell.

[0010] As an achievable manner, in the aluminum alloy material, the total mass percentage of Fe and Mn is 1.75-1.95wt%, wherein the mass percentage of Fe is 0.45-0.55wt%.

[0011] As a feasible manner, the aluminum alloy material also includes alloy elements with the following mass contents: the mass percentage of Cu is 0.08-0.20wt%; the mass percentage of Si is 0.18-0.70wt%; the mass percentage of Ti is 0.01-0.02wt%; the mass percentage of Ni is less than 0.02wt%; the mass percentage of Zn is less than 0.10wt%; and the balance is Al.

[0012] As a feasible method, the aluminum alloy material contains 1.25wt% Mn, 0.48wt% Si, 0.10wt% Cu, 0.55wt% Fe, Mg<0.02wt%, Cr<0.001wt%, Ni 0.004wt%, Ti 0.013wt%, Zn0.03wt%, Ce 0.38wt%, and the balance is Al.

[0013] As a feasible method, during the cold drawing process, a clamp is used to clamp the front end of the shell blank, and the moving speed of the core rod is less than or equal to the moving speed of the clamp during drawing, and greater than or equal to the feeding speed of the shell blank.

[0014] As a feasible manner, the core rod vibrates along the drawing direction while moving.

[0015] As a feasible manner, the vibration amplitude of the core rod is 5 μm to 30 μm; the vibration frequency of the core rod is 10 KHz to 25 KHz.

[0016] As a feasible manner, the method further includes 5) demoulding the cold-drawn battery casing from the core rod, wherein the core rod is vibrated along its axial direction during the demoulding process.

[0017] As a feasible manner, the vibration amplitude of the core rod is 12 μm to 18 μm; the vibration frequency of the core rod is 20 KHz to 22 KHz.

[0018] As a feasible method, before cold drawing, the shell blank is immersed in oil, then taken out of the oil and tilted to drain the oil droplets, and cold drawing is performed after an oil film is formed on the inner wall of the shell blank.

[0019] This application starts from the purpose of improving the strength of aluminum alloys, and uses aluminum alloy materials that have been specially configured and optimized as raw materials. On the one hand, because Ce is a rare earth element with a large atomic radius, which is much larger than the atomic radius of Al, it can bear the nucleation point in the melt, increase the nucleation concentration during solidification, and has a strong ability to refine grains. It can refine grains, improve mechanical strength and microhardness of the organization, and increase the elastic modulus, thereby improving the structural rigidity of the battery shell and ensuring the life of lithium batteries at 100 degrees Celsius. 2500-3000 breathing cycles. Compared with low-multiple organizations without adding Ce elements, it can reduce aluminum grains by one-half to one-third, which can refine grains and effectively hinder the movement of dislocations, thereby improving the strength and hardness of aluminum alloy materials; on the other hand, Ce is highly active and easy to react chemically with most metals to form a variety of refractory and hard intermetallic compounds that are very small. In aluminum alloy modification, extremely trace elements that have no strengthening effect can be converted into strengthening phases, increasing the concentration of strengthening phases and contributing to the purification of the melt.

[0020] Moreover, the Ce intermetallic compound formed is dissolved in the aluminum particles, which will cause a large lattice distortion and form high-density dislocations, hindering deformation and further ensuring strength. In the metallographic field of view, the Ce intermetallic compound generally appears as tiny white flakes, part of which is dissolved in the aluminum particles, and part of which exists in the grain boundary to form a broken chain ring, which greatly enhances the metal bond, ionic bond and van der Waals force between metals and improves the resistance to deformation.

[0021] The above-mentioned specific configuration makes the aluminum alloy material used in the present application have higher strength, which can make the manufactured battery shell have excellent performance. In addition, when preparing a battery shell with certain explosion-proof requirements, the aluminum alloy used in the present application can be processed with thinner profiles than other aluminum alloys due to its high strength. The process is simpler and easier to operate, and it is also relatively more cost-effective. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions and advantages of the present application clearer, the following will be combined with the specific embodiments of the present application and the corresponding technical solutions of the present application for a clear and complete description. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0023] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be an intermediate element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be an intermediate element at the same time.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0025] The present embodiment provides a cold drawing method for manufacturing a battery casing, comprising the following steps:

[0026] 1) taking an aluminum alloy material after configuration and optimization, wherein the aluminum alloy material comprises at least Al, Mn, Si, Cu, Fe and Ce, wherein the mass percentage of Ce is 0.3-1wt%;

[0027] 2) forming a cylindrical shell blank by extruding the aluminum alloy material in step 1);

[0028] 3) Before cold drawing, the shell blank is immersed in oil, then taken out of the oil and placed at an angle to drain the oil droplets, and then cold drawing is performed after an oil film is formed on the inner wall of the shell blank. The oil film has the effect of reducing the friction coefficient during the cold drawing process, reducing the friction between the mold and the blank, ensuring the uniform flow of the shell material during the cold drawing process, and avoiding surface defects; in addition, the oil film can effectively reduce the temperature rise during the cold drawing process and reduce the plastic rheological pressure of the aluminum alloy material; the shell blank is sleeved on the mandrel of the cold drawing die, and the front end of the blank is extended into the cold drawing cavity of the cold drawing die, and the size of the mandrel matches the size of the internal cavity required by the battery shell;

[0029] 4) Pull the shell blank along the drawing direction, and move the mandrel in the same direction as the shell blank along the drawing direction, so that the shell blank as a whole passes through the cold drawing cavity to form a battery shell. During the cold drawing process, a clamp is used to clamp the front end of the shell blank, and the moving speed of the mandrel is less than or equal to the moving speed of the clamp during drawing, and greater than or equal to the feeding speed of the shell blank. The clamp ensures the stable stretching of the shell blank during the cold drawing process by uniformly applying the clamping force, avoiding uneven stretching or distortion of the material during the cold drawing process. The relative speed control between the mandrel and the clamp is achieved through a precise transmission system to ensure accuracy and consistency during the cold drawing process. While moving, the mandrel also vibrates in the drawing direction. The vibration helps to increase the plasticity of the material, reduce the concentration of internal stress, improve the fluidity during the cold drawing process, and avoid cracks or defects caused by excessive rigidity of the material. The mandrel rod also vibrates along the drawing direction while moving, and the vibration amplitude of the mandrel rod is 5μm to 30μm; the vibration frequency of the mandrel rod is 10KHz to 25KHz, and the vibration system can dynamically adjust the vibration frequency during the cold drawing process to adapt to the fluidity requirements of different materials. The frequency and amplitude range ensures that the uniform forming and ductility of the aluminum alloy material are effectively promoted during the cold drawing process, while avoiding cracks or surface defects in the material during the stretching process.

[0030] It also includes 5) the step of demolding the cold-drawn battery shell from the mandrel, and the mandrel is vibrated along its axial direction during the demolding process. The vibration helps to reduce the internal stress generated during the cold drawing process, ensuring that the cold-drawn battery shell can be smoothly removed from the mandrel, and avoiding demolding difficulties caused by mold adhesion or stress concentration; the amplitude and frequency of the vibration are adjusted according to the shape and material properties of the cold-drawn product to optimize the demolding process. The vibration amplitude of the mandrel is 12μm to 18μm; the vibration frequency of the mandrel is 20KHz to 22KHz.

[0031] In the aluminum alloy material, the total mass percentage of Fe and Mn is 1.75-1.95wt%, wherein the mass percentage of Fe is 0.45-0.55wt%.

[0032] The aluminum alloy material also includes alloy elements with the following mass contents: the mass percentage of Cu is 0.08-0.20wt%; the mass percentage of Si is 0.18-0.70wt%; the mass percentage of Ti is 0.01-0.02wt%; the mass percentage of Ni is <0.02wt%; the mass percentage of Zn is <0.10wt%; and the balance is Al.

[0033] The specific parameter conditions of each embodiment are as follows:

[0034]

[0035]

[0036] The modified 3003B aluminum alloy battery case obtained above and the unmodified 3003B aluminum alloy battery case were tested for tensile strength, yield strength and cross-sectional shrinkage / elongation respectively. The specific test methods can refer to GB / T228.1-2021 Metal Material Tensile Test. The results are as follows:

[0037]

[0038] From the above experimental results, it can be seen that the modified 3003B aluminum alloy battery-grade subject in the embodiment of the present application has significantly improved tensile strength and yield strength, especially the tensile strength of 3003B aluminum alloy is increased from an average of 113MPa to a maximum of 142MPa, an increase of 25.7%, and the yield strength is increased from an average of 75MPa to a maximum of 98MPa, an increase of 30.7%. It can be seen that the embodiment of the present application obtains an aluminum alloy battery shell with better strength.

[0039] It can be seen from the test results of cross-sectional shrinkage and elongation that the elastic modulus of the aluminum alloy shell of this embodiment increases and the toughness is improved.

[0040] In summary, it can be seen that the battery shell prepared by the method of the present application has good strength, high rigidity and better performance.

[0041] The above embodiments only express the preferred implementation modes of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A cold drawing method for manufacturing a battery housing, characterized in that: The steps include: 1) taking an aluminum alloy material after configuration and optimization, wherein the aluminum alloy material comprises at least Al, Mn, Si, Cu, Fe and Ce, wherein the mass percentage of Ce is 0.3-1wt%; 2) forming a cylindrical shell blank by extruding the aluminum alloy material in step 1); 3) The shell blank is sleeved on the core rod of the cold drawing die, and the front end of the shell blank is extended into the cold drawing cavity of the cold drawing die, and the size of the core rod matches the size of the internal cavity required for the battery shell; 4) Pulling the shell blank along the drawing direction, and moving the core rod in the same direction as the shell blank along the drawing direction, so that the shell blank is entirely drawn out of the cold drawing cavity to form a battery shell.

2. The cold drawing method for manufacturing a battery casing according to claim 1, characterized in that: In the aluminum alloy material, the total mass percentage of Fe and Mn is 1.75-1.95wt%, wherein the mass percentage of Fe is 0.45-0.55wt%.

3. The cold drawing method for manufacturing a battery casing according to claim 2, characterized in that: The aluminum alloy material also includes alloy elements with the following mass contents: the mass percentage of Cu is 0.08-0.20wt%; the mass percentage of Si is 0.18-0.70wt%; the mass percentage of Ti is 0.01-0.02wt%; the mass percentage of Ni is less than 0.02wt%; the mass percentage of Zn is less than 0.10wt%; and the balance is Al.

4. The cold drawing method for manufacturing a battery casing according to claim 3, characterized in that: The aluminum alloy material contains 1.25wt% Mn, 0.48wt% Si, 0.10wt% Cu, 0.55wt% Fe, Mg<0.02wt%, Cr<0.001wt%, Ni0.004wt%, Ti 0.013wt%, Zn 0.03wt%, Ce 0.38wt%, and the balance is Al.

5. The cold drawing method for manufacturing a battery casing according to claim 1, characterized in that: During the cold drawing process, a clamp is used to clamp the front end of the shell blank, and the moving speed of the core rod is less than or equal to the moving speed of the clamp during drawing, and greater than or equal to the feeding speed of the shell blank.

6. The cold drawing method for manufacturing a battery casing according to claim 1, characterized in that: The mandrel also vibrates along the drawing direction while moving.

7. The cold drawing method for manufacturing a battery casing according to claim 5, characterized in that: The vibration amplitude of the core rod is 5 μm to 30 μm; the vibration frequency of the core rod is 10 KHz to 25 KHz.

8. The cold drawing method for manufacturing a battery casing according to claim 1, characterized in that: The method further comprises the step of 5) demoulding the cold-drawn battery casing from the core rod, wherein the core rod is vibrated along its axial direction during the demoulding process.

9. The cold drawing method for manufacturing a battery casing according to claim 8, characterized in that: The vibration amplitude of the core rod is 12 μm to 18 μm; the vibration frequency of the core rod is 20 KHz to 22 KHz.

10. The cold drawing method for manufacturing a battery casing according to claim 1, characterized in that: Before cold drawing, the shell blank is immersed in oil, then taken out of the oil and placed at an angle to drain the oil droplets, and cold drawing is performed after an oil film is formed on the inner wall of the shell blank.

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