A casting preparation method for aluminum alloy of new energy vehicle battery housing

Abstract

The present invention discloses a casting preparation method for an aluminum alloy used in a battery housing of a new energy vehicle, which relates to the technical field of aluminum alloys for battery housings. The casting preparation method of the present invention includes the following steps: S1. After melting and casting 3003 aluminum alloy, yttrium boride is added and heated to obtain liquid metal; S2. Aluminum-titanium-boron grain refiner alloy is added to the liquid metal, and then heat preservation and slag skimming are carried out to obtain aluminum alloy liquid; S3. The aluminum alloy liquid is subjected to die casting, annealing, surface treatment and cryogenic treatment. The aluminum alloy obtained by the method of the present invention has excellent mechanical properties and welding properties.

Description

Technical Field

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

[0002] New energy battery casings usually adopt aluminum alloy materials, mainly including the 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 due to their high plasticity, good welding performance, and low density. In particular, 3003 aluminum alloy is well-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 through traditional heat treatment methods. In addition, its processing performance also has certain limitations, which restrict its use in some application scenarios of new energy battery casings with higher material property requirements. Therefore, in order to meet the higher requirements for material properties of new energy vehicle battery casings, 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 alloys used in new energy vehicle battery casings. The aluminum alloy for new energy vehicle battery casings prepared by the method of the present invention has good mechanical properties and welding performance.

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

[0005] A casting preparation method for aluminum alloys used in new energy vehicle battery casings includes the following steps:

[0006] S1. After melting and casting 3003 aluminum alloy, add yttrium boride and heat to obtain liquid metal;

[0007] S2. Add aluminum-titanium-boron master alloy to the liquid metal, then carry out heat preservation and slag skimming to obtain aluminum alloy liquid;

[0008] S3. Carry out die casting, annealing, surface treatment, and cryogenic treatment on the aluminum alloy liquid;

[0009] The aluminum alloy for new energy vehicle battery casings includes the following raw materials in parts by mass: 100 parts of 3003 aluminum alloy, 0.2 - 1.8 parts of yttrium boride, 0.1 - 0.7 parts of aluminum-titanium-boron master alloy; preferably, 100 parts of 3003 aluminum alloy, 0.3 - 0.9 parts of yttrium boride, 0.1 - 0.3 parts of aluminum-titanium-boron master alloy;

[0010] The aluminum-titanium-boron grain refiner alloy comprises the following elements in mass percentages: Ti: 4.5 - 5.5%, B: 0.8 - 1.2%, Si ≤ 0.2%, Fe ≤ 0.2%.

[0011] The annealing temperature is 400 - 450 °C, and it is held at this annealing temperature for 1 - 2 h, and finally naturally cooled to room temperature; the room temperature in the present invention is 20 - 25 °C.

[0012] The cryogenic treatment method is to hold at -40 - -60 °C for 40 - 60 min; then cooled to -100 - -160 °C and held for 3 - 6 h.

[0013] Among them, yttrium tetraboride has the characteristics of high melting point, high hardness, good chemical stability, excellent electromagnetic properties, etc. The addition of yttrium tetraboride can significantly improve the strength and toughness of aluminum alloy, and contribute to improving its overall quality and service life; the aluminum-titanium-boron grain refiner alloy as a nucleation center can effectively refine the grains of aluminum alloy. Therefore, adding the aluminum-titanium-boron grain refiner alloy can significantly improve the processing performance and mechanical properties of aluminum alloy.

[0014] In the present invention, the 3003 aluminum alloy comprises the following elements in mass percentages: 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 percentages: Fe: 0.7%, Si: 0.6%, Cu: 0.12%, Mn: 0.12%, Zn: 0.1%, and the balance is Al and inevitable impurities.

[0015] In the present invention, the yttrium tetraboride (CAS No.: 12008-32-1) has a tetragonal crystal system structure.

[0016] In the present invention, the aluminum-titanium-boron grain refiner alloy is composed of the following elements in mass percentages: Ti: 4.5 - 5.5%, B: 0.8 - 1.2%, Si ≤ 0.2%, Fe ≤ 0.2%, and the balance is Al and inevitable impurities.

[0017] In the present invention, the tensile strength of the aluminum alloy for the battery housing of new energy vehicles is 246 - 263 MPa.

[0018] In the present invention, the incidence rate of abnormal welding pools of the aluminum alloy for the battery housing of new energy vehicles ≤ 2%, such as 0%, 1%, 2%.

[0019] In S1, the melting and casting temperature is 620 - 670 °C, preferably 630 - 660 °C.

[0020] In S1, the melting and casting time is 2 - 4 h, preferably 2 - 3 h.

[0021] In S1, the heating temperature is 680 - 750 °C, preferably 710 - 730 °C.

[0022] In S1, the heating time is 20 - 60 min, preferably 30 - 50 min.

[0023] Both step S1 and step S2 are carried out in a nitrogen atmosphere, and the nitrogen pressure is independently 1.5 - 2.5 kg / mm 2 .

[0024] In S2, the heat preservation temperature is 600 - 650 °C, preferably 610 - 630 °C.

[0025] In S2, the heat preservation time is 0.5 - 1.5 h.

[0026] In S3, the die-casting temperature is 670 - 720 °C.

[0027] In S3, the filling speed of die-casting is 30 - 55 m / s, preferably 46 - 55 m / s.

[0028] In S3, the injection specific pressure of die-casting is 30 - 90 MPa, such as 50 MPa.

[0029] In S3, the annealing temperature is 430 - 450 °C, and it is heat-preserved at the annealing temperature for 1.5 - 2 h, and finally naturally cooled to room temperature.

[0030] In S3, the cryogenic treatment method is to heat-preserve at -50 - -60 °C for 40 - 60 min; then cool to -100 - -120 °C and heat-preserve for 3 - 4 h.

[0031] Among them, annealing can ensure the uniform and stable structure of the material and eliminate internal stress, thereby improving the plasticity and toughness of the material; cryogenic treatment can enhance the hardness and strength of the material through rapid cooling, but at the same time it will also increase the brittleness of the material, so the cryogenic treatment parameters need to be controlled. Therefore, the combined use of appropriate annealing temperature and cryogenic treatment can improve the strength of the material while maintaining good plasticity and toughness.

[0032] The application of the aluminum alloy for new energy vehicle battery housing as described above or the aluminum alloy for new energy vehicle battery housing prepared by the casting preparation method as described in any previous item in new energy vehicle battery housing, high-voltage distribution box body, on-vehicle charger housing and control box body.

[0033] On the basis of conforming to the common knowledge in the art, the above preferred conditions can be combined arbitrarily to obtain various preferred examples of the present invention.

[0034] Compared with the prior art, the beneficial effects of the present invention are:

[0035] 1. The present invention obtains an aluminum alloy for a new energy vehicle battery housing by proportioning the components of 3003 aluminum alloy, yttrium boride, and aluminum-titanium-boron master alloy. In the aluminum alloy for a new energy vehicle battery housing of the present invention, yttrium boride 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.

[0036] 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 to eliminate internal stress; at the same time, the process of cryogenic treatment is precisely adjusted. The cryogenic treatment is to eliminate residual stress. After the aluminum alloy of the present invention is annealed and then subjected to cryogenic treatment, its comprehensive performance can be further improved, making the mechanical properties and welding properties of the aluminum alloy for a new energy vehicle battery housing excellent.

[0037] 3. The aluminum alloy for a new energy vehicle battery housing of the present invention has good toughness and workability, its tensile strength can reach 246 - 263 MPa, and the incidence rate of abnormal weld pools is ≤ 2%. Detailed Embodiments

[0038] To facilitate the understanding of the present invention, the following will describe the present invention more comprehensively and meticulously in combination with preferred embodiments, but the protection scope of the present invention is not limited to the following specific embodiments.

[0039] Unless otherwise defined, all professional terms used hereinafter have the same meaning as commonly 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 protection scope of the present invention.

[0040] The "scope" disclosed in the present invention is defined in the form of a lower limit and an upper limit. A given scope 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 scope. The scope defined in this way can include or exclude the end values, and any combination is possible, that is, any lower limit can be combined with any upper limit to form a scope. For example, if ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, ranges of 60 - 110 and 80 - 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5. In the present invention, unless otherwise stated, the numerical range "a - b" represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" are fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations. Additionally, when stating that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0041] If there is no special instruction, all embodiments and optional embodiments of the present invention can be combined with each other to form a new technical solution.

[0042] If there is no special instruction, all technical features and optional technical features of the present invention can be combined with each other to form a new technical solution.

[0043] If there is no special instruction, all steps of the present invention can be carried out sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method can include steps (a) and (b) carried out sequentially, or can also include steps (b) and (a) carried out sequentially. For example, it is mentioned that the method may further include step (c), which means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b), and (c), or can also include steps (a), (c), and (b), or can also include steps (c), (a), and (b), etc.

[0044] If there is no special instruction, the "including" and "comprising" mentioned in the present invention mean open-ended, and can also be closed-ended. For example, the "including" and "comprising" can mean that other components not listed can also be included or comprised, or can also only include or comprise the listed components.

[0045] Unless otherwise specified, 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 present) and B is false (or absent); A is false (or absent) while B is true (or present); or both A and B are true (or present).

[0046] The following examples or comparative examples use the following raw materials:

[0047] The aluminum-titanium-boron master alloy was purchased from Jiangxi Hongke Special Alloys Co., Ltd.;

[0048] The 3003 aluminum alloy was purchased from Mingtai Aluminum Co., Ltd. and consisted of the following elements by 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;

[0049] Yttrium tetraboride was purchased from Hunan Rare Earth Metal Materials Research Institute, and yttrium tetraboride had a tetragonal crystal system structure;

[0050] The aluminum-titanium-boron master alloy was purchased from Taizhou Xinuo Metal Materials Co., Ltd. and consisted of the following elements by mass percentage: Ti: 5%, B: 1%, Si ≤ 0.2%, Fe ≤ 0.2%, and the balance was Al and unavoidable impurities.

[0051] Example 1

[0052] 1. The aluminum alloy for the battery housing of new energy vehicles in this example was composed of the following raw materials in parts by mass: 100 parts of 3003 aluminum alloy, 0.7 part of yttrium tetraboride, and 0.2 part of aluminum-titanium-boron master alloy.

[0053] 2. The casting preparation method of the aluminum alloy for the battery housing of new energy vehicles in this example was as follows:

[0054] S1. After preparing the above raw materials, under the condition of a nitrogen pressure of 2.0 kg / mm 2 The 3003 aluminum alloy was melted and cast at 650 °C for 3 h, and then yttrium tetraboride was added and heated at 710 °C for 45 min to obtain liquid metal.

[0055] S2. Under the condition of a nitrogen pressure of 2.0 kg / mm 2 The aluminum-titanium-boron master alloy was added to the liquid metal and kept warm at 620 °C for 1 h, and slag skimming was required during the process to obtain aluminum alloy liquid.

[0056] S3. Die aluminum alloy liquid is die-cast at 680 °C, with a filling speed of 46 m / s and an injection specific pressure of 50 MPa; then the annealing temperature is 430 °C, and it is held at this annealing temperature for 2 h, and then cooled to room temperature; it is held at -50 °C for 45 min, and then cooled to -100 °C and held for 3 h. After cryogenic treatment, the aluminum alloy for the new energy vehicle battery housing is obtained.

[0057] Example 2

[0058] The difference between this example and Example 1 is as follows:

[0059] 1. The aluminum alloy for the new energy vehicle battery housing in this example is composed of the following raw materials in parts by mass: 100 parts of 3003 aluminum alloy, 0.5 part of yttrium boride, and 0.3 part of aluminum-titanium-boron master alloy.

[0060] Example 3

[0061] The difference between this example and Example 1 is as follows:

[0062] 2. The casting preparation method of the aluminum alloy for the new energy vehicle battery housing in this example is as follows:

[0063] S1. After preparing the above raw materials, under the condition of a nitrogen pressure of 2.5 kg / mm 2 , the 3003 aluminum alloy is melted and cast at 630 °C for 2 h, and then yttrium boride is added and heated at 710 °C for 30 min to obtain liquid metal;

[0064] S2. Under the condition of a nitrogen pressure of 2.5 kg / mm 2 , the aluminum-titanium-boron master alloy is added to the liquid metal and held at 610 °C for 1.5 h. During the process, slag needs to be skimmed to obtain aluminum alloy liquid.

[0065] Example 4

[0066] The difference between this example and Example 1 is as follows:

[0067] 2. The casting preparation method of the aluminum alloy for the new energy vehicle battery housing in this example is as follows:

[0068] S3. The aluminum alloy liquid is die-cast at 670 °C, with a filling speed of 50 m / s and an injection specific pressure of 60 MPa; then the annealing temperature is 450 °C, and it is held at this annealing temperature for 2 h, and then cooled to room temperature; it is held at -50 °C for 60 min, and then cooled to -120 °C and held for 4 h. After cryogenic treatment, the aluminum alloy for the new energy vehicle battery housing is obtained.

[0069] Comparative Example 1

[0070] The difference between this comparative example and Example 1 is as follows:

[0071] 1. The aluminum alloy for the battery housing of new energy vehicles in this embodiment is composed of the following raw materials in parts by mass: 100 parts of 3003 aluminum alloy and 0.9 part of aluminum-titanium-boron grain refiner alloy.

[0072] 2. The casting preparation method of the aluminum alloy for the battery housing of new energy vehicles in this embodiment is as follows:

[0073] S1. After preparing the above raw materials, under the condition that the nitrogen pressure is 2.0 kg / mm 2 The 3003 aluminum alloy is melt-cast at 650 °C for 3 h to obtain liquid metal.

[0074] Comparative Example 2

[0075] The difference between this comparative example and Example 1 lies in:

[0076] 1. The aluminum alloy for the battery housing of new energy vehicles in this embodiment is composed of the following raw materials in parts by mass: 100 parts of 3003 aluminum alloy and 2.0 parts of yttrium boride.

[0077] 2. The casting preparation method of the aluminum alloy for the battery housing of new energy vehicles in this embodiment is as follows:

[0078] S2. Under the condition that the nitrogen pressure is 2.0 kg / mm 2 The liquid metal is kept warm at 620 °C for 1 h, and slag needs to be skimmed during the process to obtain aluminum alloy liquid.

[0079] Comparative Example 3

[0080] The difference between this comparative example and Example 1 lies in:

[0081] S3. The aluminum alloy liquid is die-cast at 680 °C, the filling speed is 46 m / s, and the injection specific pressure is 50 MPa; then the annealing temperature is 530 °C, and it is kept warm at this annealing temperature for 1 h, and then cooled to room temperature; it is kept warm at -35 °C for 40 min, and then cooled to -100 °C and kept warm for 3 h. After cryogenic treatment, the aluminum alloy for the battery housing of new energy vehicles is obtained.

[0082] Comparative Example 4

[0083] The difference between this comparative example and Example 1 lies in:

[0084] S3. The aluminum alloy liquid is die-cast at 680 °C, the filling speed is 46 m / s, and the injection specific pressure is 50 MPa; then the annealing temperature is 430 °C, and it is kept warm at this annealing temperature for 2 h, and then cooled to room temperature; then it is cooled to -100 °C and kept warm for 6 h. After cryogenic treatment, the aluminum alloy for the battery housing of new energy vehicles is obtained. The aluminum alloy obtained in this comparative example will crack during welding, and the joint will soften.

[0085] Effect Examples

[0086] The tensile strength and the incidence rate of abnormal weld pools in the above comparative examples and examples were measured with reference to GB / T 33824; among them, the average value of the incidence rate of abnormal weld pools of two welds (100 weld pools were randomly selected from each weld) was taken as the final result. The reference measurement results of the salt spray resistance performance are shown in Table 1.

[0087] ;

[0088] Compared with Example 1, in Comparative Example 1, the raw material did not contain yttrium boride, which led to a decrease in the strength and toughness of the aluminum alloy. In Comparative Example 2, the raw material did not contain the aluminum-titanium-boron master alloy, which might cause the grains of the aluminum alloy to coarsen, thereby reducing its ductility. The coarsening of grains might also increase the stress during the welding process. In Comparative Example 3, the annealing temperature was too high, so there were not enough temperature and time conditions for grain refinement. In Comparative Example 4, the too-fast cryogenic treatment speed might lead to excessive thermal stress, which might damage the microstructure of the aluminum alloy material, thereby affecting its mechanical properties. The too-fast cryogenic speed might also generate higher residual stress in the welded joint area, which might further affect the welding quality.

[0089] Unless otherwise specifically stated, all kinds of raw materials, reagents, instruments, equipment, etc. used in the present invention can be obtained through market purchase or can be prepared by existing methods. The above specific embodiments have further detailed the purpose, technical solutions and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within 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 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%; 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: 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 30~90MPa.

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.