Casting preparation method of aluminum alloy for new energy automobile battery shell

Abstract

The invention discloses a casting preparation method for a new energy automobile battery shell aluminum alloy, and relates to the technical field of battery shell aluminum alloys. The casting preparation method comprises the following steps that S1, after 3003 aluminum alloy is cast, yttrium tetraboride is added, and liquid metal is obtained after heating; s2, after aluminum-titanium-boron seed crystal alloy is added into the liquid metal, heat preservation and slagging-off are conducted, and aluminum alloy liquid is obtained; and S3, the molten aluminum alloy is subjected to die casting, annealing, surface treatment and subzero treatment. The aluminum alloy obtained through the method is excellent in mechanical performance and welding performance.

Description

Technical Field

[0001] The invention belongs to the technical field of battery shell aluminum alloys, and specifically relates to a casting preparation method for aluminum alloys used in battery shells of new energy vehicles. Background Art

[0002] New energy battery shells usually use aluminum alloy materials, mainly including 3000 series (Al-Mn series), 5000 series (Al-Mg series) and 6000 series (Al-Mg-Si series). Among these series, 3000 series aluminum alloys are favored for their high plasticity, good welding performance and low density. In particular, 3003 aluminum alloy is known for its high cost-effectiveness, light weight, strong corrosion resistance and excellent welding performance. However, the mechanical properties of 3003 aluminum alloy are relatively weak, and its strength cannot be enhanced by traditional heat treatment methods. In addition, its processing performance also has certain limitations, which restrict its use in some new energy battery shell application scenarios with high material performance requirements. Therefore, in order to meet the higher requirements of new energy vehicle battery shells for material performance, it is necessary to develop aluminum alloy materials with better mechanical properties and processing performance. Summary of the invention

[0003] The present invention overcomes the above technical problems and provides a casting preparation method for aluminum alloy for new energy vehicle battery shell. The aluminum alloy for new energy vehicle battery shell prepared by the method of the present invention has good mechanical properties and welding properties.

[0004] The present invention solves the above technical problems through the following technical solutions.

[0005] A casting preparation method for an aluminum alloy for a battery housing of a new energy vehicle comprises the following steps: S1. After 3003 aluminum alloy is melted and cast, yttrium tetraboride is added and heated to obtain liquid metal; S2. After adding aluminum-titanium-boron seed alloy to the liquid metal, heat preservation and slag removal are performed to obtain aluminum alloy liquid; S3. The aluminum alloy liquid is subjected to die casting, annealing, surface treatment and cryogenic treatment; The aluminum alloy for the battery housing of new energy vehicles includes the following raw materials by weight: 100 parts of 3003 aluminum alloy, 0.2-1.8 parts of yttrium tetraboride, and 0.1-0.7 parts of aluminum-titanium-boron seed alloy; preferably, 100 parts of 3003 aluminum alloy, 0.3-0.9 parts of yttrium tetraboride, and 0.1-0.3 parts of aluminum-titanium-boron seed alloy; The aluminum-titanium-boron seed alloy includes the following elements in percentage by mass: Ti: 4.5-5.5%, B: 0.8-1.2%, Si≤0.2%, Fe≤0.2%; The annealing temperature is 400-450°C, and the annealing temperature is kept for 1-2 hours, and finally cooled naturally to room temperature; the room temperature of the present invention is 20-25°C; The deep freezing treatment is carried out by keeping the temperature at -40 to -60°C for 40 to 60 minutes, and then cooling to -100 to -160°C and keeping the temperature for 3 to 6 hours.

[0006] Among them, yttrium tetraboride has the characteristics of high melting point, high hardness, good chemical stability and excellent electromagnetic properties. The addition of yttrium tetraboride can significantly improve the strength and toughness of aluminum alloys, and help improve their overall quality and service life; aluminum-titanium-boron seed alloy, as a nucleation center, can effectively refine the aluminum alloy grains. Therefore, the addition of aluminum-titanium-boron seed alloy can significantly improve the processing performance and mechanical properties of aluminum alloys.

[0007] In the present invention, the 3003 aluminum alloy includes the following elements in mass percentage: Fe: 0.7%, Si: 0.6%, Cu: 0.05~0.20%, Mn: 0.1~1.5%, Zn: 0.1%; preferably, the 3003 aluminum alloy is composed of the following elements in mass percentage: Fe: 0.7%, Si: 0.6%, Cu: 0.12%, Mn: 0.12%, Zn: 0.1%, and the balance is Al and unavoidable impurities.

[0008] In the present invention, the yttrium tetraboride (CAS No.: 12008-32-1) has a tetragonal crystal structure.

[0009] In the present invention, the aluminum-titanium-boron seed alloy is composed of the following elements in percentage by mass: Ti: 4.5-5.5%, B: 0.8-1.2%, Si≤0.2%, Fe≤0.2%, and the remainder is Al and unavoidable impurities.

[0010] In the present invention, the tensile strength of the aluminum alloy used for the battery housing of new energy vehicles is 246~263MPa.

[0011] In the present invention, the abnormal weld pool occurrence rate of the aluminum alloy used for the battery housing of new energy vehicles is ≤2%, for example, 0%, 1%, 2%.

[0012] In S1, the melting and casting temperature is 620-670°C, preferably 630-660°C.

[0013] In S1, the smelting time is 2 to 4 hours, preferably 2 to 3 hours.

[0014] In S1, the heating temperature is 680-750°C, preferably 710-730°C.

[0015] In S1, the heating time is 20 to 60 minutes, preferably 30 to 50 minutes.

[0016] Step S1 and step S2 are both carried out in a nitrogen atmosphere, and the nitrogen pressure is independently 1.5-2.5 kg / mm 2 .

[0017] In S2, the insulation temperature is 600-650°C, preferably 610-630°C.

[0018] In S2, the insulation time is 0.5 to 1.5 hours.

[0019] In S3, the die-casting temperature is 670-720°C.

[0020] In S3, the die-casting filling speed is 30-55 m / s, preferably 46-55 m / s.

[0021] In S3, the die casting injection pressure is 30-90 MPa, for example, 50 MPa.

[0022] In S3, the annealing temperature is 430-450° C., and the annealing temperature is kept for 1.5-2 hours, and finally naturally cooled to room temperature.

[0023] In S3, the deep cryogenic treatment is carried out by keeping the temperature at -50 to -60°C for 40 to 60 minutes, and then cooling to -100 to -120°C and keeping the temperature for 3 to 4 hours.

[0024] Among them, annealing can ensure that the material's structure is uniform and stable, and eliminate internal stress, thereby improving the material's plasticity and toughness; cryogenic treatment can enhance the material's hardness and strength through rapid cooling, but it will also increase the material's brittleness, so the cryogenic treatment parameters must be controlled. Therefore, the combination of appropriate annealing temperature and cryogenic treatment can improve the material's strength while maintaining good plasticity and toughness.

[0025] The application of the aluminum alloy for new energy vehicle battery shell as mentioned above or the aluminum alloy for new energy vehicle battery shell prepared by the casting preparation method as described in any of the preceding items in new energy vehicle battery shells, high-voltage distribution box bodies, on-board charger shells and control boxes.

[0026] On the basis of being in accordance with the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0027] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention obtains an aluminum alloy for a battery housing of a new energy vehicle by mixing 3003 aluminum alloy, yttrium tetraboride and aluminum-titanium-boron seed alloy. In the aluminum alloy for a battery housing of a new energy vehicle of the present invention, yttrium tetraboride is added to the aluminum alloy to significantly enhance its strength and toughness due to its high melting point, high hardness and excellent chemical stability.

[0028] 2. In the casting preparation method of the present invention, the annealing temperature and time are strictly controlled in combination with the specific aluminum alloy liquid composition of the present invention to ensure that the alloy material structure is more uniform and stable and eliminate internal stress; at the same time, the process of deep cryogenic treatment is precisely adjusted and controlled, and deep cryogenic treatment is to eliminate residual stress. The aluminum alloy of the present invention is subjected to deep cryogenic treatment after annealing treatment, which can further improve its comprehensive performance, so that the mechanical properties and welding properties of the aluminum alloy used for the battery housing of new energy vehicles are excellent.

[0029] 3. The aluminum alloy for the battery housing of new energy vehicles of the present invention has good toughness and processing performance, its tensile strength can reach 246~263MPa, and the occurrence rate of abnormal welding pool is ≤2%. DETAILED DESCRIPTION

[0030] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and carefully in combination with preferred embodiments below, but the protection scope of the present invention is not limited to the following specific embodiments.

[0031] Unless otherwise defined, all professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0032] The "range" disclosed in the present invention is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The range defined in this way can be inclusive or exclusive of end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60-120 and 80-110 is listed for a specific parameter, it is understood that the range of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following ranges can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present invention, unless otherwise specified, the numerical range "ab" represents an abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" represents that all real numbers between "0-5" have been fully listed herein, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0033] If not otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form a new technical solution.

[0034] Unless otherwise specified, all technical features and optional technical features of the present invention can be combined with each other to form a new technical solution.

[0035] If not otherwise specified, all steps of the present invention may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0036] If there is no special explanation, the "include" and "comprising" mentioned in the present invention represent open-ended or closed-ended expressions. For example, the "include" and "comprising" may represent that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0037] If not specifically stated, in the present invention, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0038] The following examples or comparative examples use the following raw materials: Al-Ti-B seed alloy was purchased from Jiangxi Hongke Special Alloy; 3003 aluminum alloy was purchased from Mingtai Aluminum Co., Ltd. and consisted of the following elements in mass percentage: Fe: 0.7%, Si: 0.6%, Cu: 0.12%, Mn: 0.12%, Zn: 0.1%, and the balance was Al and unavoidable impurities; Yttrium tetraboride was purchased from Hunan Rare Earth Metal Materials Research Institute. Yttrium tetraboride has a tetragonal crystal structure. The aluminum-titanium-boron seed alloy was purchased from Taizhou Xinuo Metal Materials Co., Ltd. and consisted of the following elements in percentage by mass: Ti: 5%, B: 1%, Si≤0.2%, Fe≤0.2%, and the remainder was Al and unavoidable impurities.

[0039] Example 1 1. The aluminum alloy for the battery housing of new energy vehicles in this embodiment is composed of the following raw materials by mass: 100 parts of 3003 aluminum alloy, 0.7 parts of yttrium tetraboride, and 0.2 parts of aluminum-titanium-boron seed alloy.

[0040] 2. The casting preparation method of the aluminum alloy for the battery housing of new energy vehicles in this embodiment is as follows: S1. After the above raw materials are prepared, the nitrogen pressure is 2.0kg / mm 2 Under these conditions, 3003 aluminum alloy was melt-cast at 650°C for 3 hours, and then yttrium tetraboride was added and heated at 710°C for 45 minutes to obtain liquid metal.

[0041] S2. At nitrogen pressure of 2.0kg / mm 2 Under these conditions, aluminum-titanium-boron seed alloy is added to the liquid metal and kept warm at 620°C for 1 hour. During the process, slag needs to be removed to obtain aluminum alloy liquid.

[0042] S3. The aluminum alloy liquid is die-casted at 680°C with a filling speed of 46m / s and an injection pressure of 50MPa; the annealing temperature is 430°C, and it is kept at this annealing temperature for 2h, and then cooled to room temperature; it is kept at -50°C for 45min, and then cooled to -100°C and kept for 3h. After deep cryogenic treatment, an aluminum alloy for new energy vehicle battery shell is obtained.

[0043] Example 2 The difference between this embodiment and embodiment 1 is that: 1. The aluminum alloy for the battery housing of new energy vehicles in this embodiment is composed of the following raw materials by mass: 100 parts of 3003 aluminum alloy, 0.5 parts of yttrium tetraboride, and 0.3 parts of aluminum-titanium-boron seed alloy.

[0044] Example 3 The difference between this embodiment and embodiment 1 is that: 2. The casting preparation method of the aluminum alloy for the battery housing of new energy vehicles in this embodiment is as follows: S1. After the above raw materials are prepared, the nitrogen pressure is 2.5kg / mm 2 Under the above conditions, 3003 aluminum alloy was melt-casted at 630℃ for 2h, and then yttrium tetraboride was added and heated at 710℃ for 30min to obtain liquid metal. S2. At nitrogen pressure of 2.5kg / mm 2 Under these conditions, aluminum-titanium-boron seed alloy is added to the liquid metal and kept warm at 610°C for 1.5 hours. During the process, slag needs to be removed to obtain aluminum alloy liquid.

[0045] Example 4 The difference between this embodiment and embodiment 1 is that: 2. The casting preparation method of the aluminum alloy for the battery housing of new energy vehicles in this embodiment is as follows: S3. The aluminum alloy liquid is die-casted at 670°C with a filling speed of 50m / s and an injection pressure of 60MPa; the annealing temperature is 450°C, and it is kept at this annealing temperature for 2h, and then cooled to room temperature; it is kept at -50°C for 60min, and then cooled to -120°C and kept for 4h. After deep cryogenic treatment, an aluminum alloy for new energy vehicle battery shell is obtained.

[0046] Comparative Example 1 The difference between this comparative example and Example 1 is: 1. The aluminum alloy for the battery shell of new energy vehicles in this embodiment is composed of the following raw materials by mass: 100 parts of 3003 aluminum alloy and 0.9 parts of aluminum-titanium-boron seed alloy.

[0047] 2. The casting preparation method of the aluminum alloy for the battery housing of new energy vehicles in this embodiment is as follows: S1. After the above raw materials are prepared, the nitrogen pressure is 2.0kg / mm 2 Under these conditions, 3003 aluminum alloy was melt-cast at 650°C for 3 hours to obtain liquid metal.

[0048] Comparative Example 2 The difference between this comparative example and Example 1 is: 1. The aluminum alloy for the battery housing of new energy vehicles in this embodiment is composed of the following raw materials by mass: 100 parts of 3003 aluminum alloy and 2.0 parts of yttrium tetraboride.

[0049] 2. The casting preparation method of the aluminum alloy for the battery housing of new energy vehicles in this embodiment is as follows: S2. At nitrogen pressure of 2.0kg / mm 2 Under these conditions, the liquid metal is kept at 620°C for 1 hour. During the process, the slag needs to be removed to obtain aluminum alloy liquid.

[0050] Comparative Example 3 The difference between this comparative example and Example 1 is: S3. The aluminum alloy liquid is die-casted at 680°C with a filling speed of 46m / s and an injection pressure of 50MPa; the annealing temperature is 530°C, and it is kept at this annealing temperature for 1h, and then cooled to room temperature; it is kept at -35°C for 40min, and then cooled to -100°C and kept for 3h. After deep cryogenic treatment, an aluminum alloy for new energy vehicle battery shell is obtained.

[0051] Comparative Example 4 The difference between this comparative example and Example 1 is: S3. The aluminum alloy liquid is die-casted at 680°C, with a filling speed of 46m / s and an injection pressure of 50MPa; the annealing temperature is 430°C, and the temperature is kept at the annealing temperature for 2h, and then cooled to room temperature; then cooled to -100°C and kept for 6h, and after deep cryogenic treatment, an aluminum alloy for the battery shell of new energy vehicles is obtained. The aluminum alloy obtained in this comparative example will crack during welding, and the joint will soften.

[0052] Effect Example The tensile strength and abnormal weld pool occurrence rate of the above comparative examples and embodiments are determined in accordance with GB / T 33824; the abnormal weld pool occurrence rate is the average value of the abnormal weld pool occurrence rate of two welds (100 weld pools are randomly selected for each weld) as the final result. The salt spray resistance performance is referred to in Table 1.

[0053] ;

[0054] Compared with Example 1, in Comparative Example 1, the raw material does not contain yttrium tetraboride, thereby resulting in a decrease in the strength and toughness properties of the aluminum alloy. In Comparative Example 2, the raw material does not contain an aluminum-titanium-boron seed alloy, which may cause coarsening of the aluminum alloy grains, thereby reducing its ductility. Grain coarsening may also increase stress during welding. In Comparative Example 3, the high annealing temperature does not provide sufficient temperature and time conditions for grain refinement. In Comparative Example 4, too fast a cryogenic treatment rate may result in excessive thermal stress, which may damage the microstructure of the aluminum alloy material, thereby affecting its mechanical properties. Too fast a cryogenic treatment rate may also produce higher residual stresses in the weld joint area, which may further affect the welding quality.

[0055] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods. The specific embodiments described above further describe the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A casting preparation method for aluminum alloy for new energy vehicle battery housing, characterized in that: The following steps are involved: S1. After 3003 aluminum alloy is melted and cast, yttrium tetraboride is added and heated to obtain liquid metal; S2. After adding aluminum-titanium-boron seed alloy to the liquid metal, heat preservation and slag removal are performed to obtain aluminum alloy liquid; S3. The aluminum alloy liquid is die-casted, annealed, surface treated and cryogenically treated to obtain an aluminum alloy for a new energy vehicle battery housing; The aluminum alloy for the battery housing of new energy vehicles comprises the following raw materials by weight: 100 parts of 3003 aluminum alloy, 0.2-1.8 parts of yttrium tetraboride, and 0.1-0.7 parts of aluminum-titanium-boron seed alloy; The aluminum-titanium-boron seed alloy includes the following elements in percentage by mass: Ti: 4.5-5.5%, B: 0.8-1.2%, Si≤0.2%, Fe≤0.2%; The annealing temperature is 400-450°C, and the annealing temperature is kept for 1-2 hours, and finally cooled naturally to room temperature; The deep freezing treatment is carried out by keeping the temperature at -40 to -60°C for 40 to 60 minutes, and then cooling to -100 to -160°C and keeping the temperature for 3 to 6 hours.

2. The casting preparation method for the aluminum alloy for the battery housing of new energy vehicles according to claim 1, characterized in that: Meet at least one of the following conditions ①~②: ① The 3003 aluminum alloy includes the following elements in mass percentage: Fe: 0.7%, Si: 0.6%, Cu: 0.05-0.20%, Mn: 0.1-1.5%, Zn: 0.1%; ② The yttrium tetraboride has a tetragonal crystal structure.

3. The casting preparation method for the aluminum alloy for the battery housing of new energy vehicles according to claim 1, characterized in that: Meet at least one of the following conditions ①~②: ① The tensile strength of the aluminum alloy used for the battery housing of new energy vehicles is 246~263MPa; ② The occurrence rate of abnormal welding pool of aluminum alloy used for new energy vehicle battery shell is ≤2%.

4. The casting preparation method for the aluminum alloy for the battery housing of new energy vehicles according to claim 1, characterized in that: Meet at least one of the following conditions ①~②: ① The melting and casting temperature is 620~670℃; ② The smelting time is 2 to 4 hours.

5. The casting preparation method for the aluminum alloy for the battery housing of new energy vehicles according to claim 1, characterized in that: Meet at least one of the following conditions ①~②: ① The heating temperature is 680~750℃; ②The heating time is 20 to 60 minutes.

6. The casting preparation method for the aluminum alloy for the battery housing of new energy vehicles according to claim 1, characterized in that: Step S1 and step S2 are both carried out in a nitrogen atmosphere, and the nitrogen pressure is independently 1.5~2.5kg / mm 2 .

7. The casting preparation method for the aluminum alloy for the battery housing of new energy vehicles according to claim 1, characterized in that: Meet at least one of the following conditions ①~②: ① The insulation temperature is 600-650°C; ②The insulation time is 0.5~1.5h.

8. The casting preparation method for the aluminum alloy for the battery housing of new energy vehicles according to claim 1, characterized in that: Meet at least one of the following conditions ①~③: ① The die-casting temperature is 670~720℃; ② The die-casting filling speed is 30~55m / s; ③ The die casting injection pressure ratio is 30~90 MPa.

9. The casting preparation method for the aluminum alloy for the battery housing of new energy vehicles according to claim 1, characterized in that: The annealing temperature is 430-450° C., and the annealing temperature is kept for 1.5-2 hours, and finally naturally cooled to room temperature.

10. The casting preparation method for the aluminum alloy for the battery housing of new energy vehicles according to claim 1, characterized in that: The deep freezing treatment is carried out by keeping the temperature at -50 to -60°C for 40 to 60 minutes, and then cooling to -100 to 120°C and keeping the temperature for 3 to 4 hours.