Preparation method of Al-Mn series aluminum alloy flat cast ingot for power battery shell

Abstract

The invention relates to a preparation method of an Al-Mn series aluminum alloy flat cast ingot for a power battery shell, in particular to the preparation method of the Al-Mn series aluminum alloy flat cast ingot for the power battery shell. The invention aims to solve the problems of low performance, poor processing stability and poor surface quality of plates and strips produced by the Al-Mn series aluminum alloy flat cast ingot for the power battery shell manufactured by the existing method. Ar gas is adopted to refine and purify the melt, and the melt is purified outside the furnace; a double-rotor degassing device and a 30 + 50ppi double-stage ceramic filter are adopted, so that the content of gas and inclusions in a cast ingot is reduced, and the melt quality is improved; a double-row pulse water cooling technology is adopted, the cooling strength is reduced in the casting starting stage, ingot casting stress is reduced, and the ingot casting forming rate is increased. The method is applied to preparation of the Al-Mn series aluminum alloy flat cast ingot for the power battery shell.

Description

Technical Field

[0001] The present invention specifically relates to a method for preparing an Al-Mn series aluminum alloy flat ingot for a power battery shell. Background Art

[0002] With the development of new energy vehicles, the demand for large-size power battery shells has increased significantly. Al-Mn aluminum alloys are widely used in power battery shells because of their easy forming, excellent comprehensive mechanical processing performance, good corrosion resistance, light specific gravity, moderate strength and strong explosion resistance. However, the power battery shell has extremely high requirements on the comprehensive performance of materials. The power battery shell is formed by stamping, with large deformation, many stamping processes, complex stamping processes, precise mold design and asymmetric box-type stamping. Material properties are one of the important basic conditions for successful stamping. It is required to have good deep drawing performance and various mechanical properties are stable within a strict range. In order to effectively protect the internal battery structure, the power battery shell must have sufficient strength and hardness while ensuring the necessary plasticity. In order to adapt to different use environments and ensure the service life of the battery, the materials used must have good corrosion resistance and chemical stability. In view of this, it is urgent to study a method for preparing Al-Mn aluminum alloy flat ingots for power battery shells to meet the market demand for high-quality products. Summary of the invention

[0003] The present invention aims to solve the problems of low performance of plates and strips produced by Al-Mn aluminum alloy flat ingots for power battery shells manufactured by existing methods, as well as poor processing stability and surface quality, and provides a method for preparing Al-Mn aluminum alloy flat ingots for power battery shells.

[0004] A method for preparing an Al-Mn aluminum alloy flat ingot for a power battery shell is completed by the following steps:

[0005] 1. Weighing: According to the ratio of Si being 0.4% to 1.0%, Fe being 0.2% to 1.0%, Cu being 0.3% to 1.2%, Mn being 1.3% to 1.6%, Zn being 0.01% to 0.10%, Ti being 0.05% to 0.25% and the balance being Al, weigh the remelted aluminum ingot, metal Cu, metal Zn, Al-Ti master alloy, Al-Si master alloy, Fe additive and Mn additive as smelting raw materials;

[0006] 2. Melting: adding the weighed smelting raw materials into a natural gas melting furnace to melt all the added materials at a temperature of 700°C to 750°C, and then stirring the melt for 15 to 20 minutes at a temperature of 720 to 750°C and a stirring speed of 1.0 to 1.5 m / s to obtain an aluminum alloy melt;

[0007] 3. Casting: The aluminum alloy melt is introduced into a natural gas insulation furnace, refined with Ar gas at a temperature of 720-740°C, covered with 2# flux and allowed to stand for 20-30 minutes to obtain a casting melt; the casting melt is successively passed through an out-of-furnace degassing device and a filtering device, and the casting melt is made into an Al-Mn aluminum alloy flat ingot for power battery shell by a semi-continuous casting method under the conditions of a temperature of 720-750°C, a metal liquid level of 70-100mm, and a cooling water temperature of 10-25°C.

[0008] Beneficial effects of the present invention:

[0009] The present invention optimizes the chemical composition of Al-Mn alloys, and can carry out rolling, deep drawing deformation processing and inflation process on the basis of maintaining the high strength and high plasticity of Al-Mn alloys, and at the same time, has good surface quality; the present invention adopts Ar gas to refine and purify the melt in the insulation furnace, and adopts a double rotor degassing device and a 30+50ppi two-stage ceramic filter to purify the melt outside the furnace, so as to reduce the gas and inclusion content in the ingot and improve the melt quality; adopts advanced double-row pulse water cooling technology to reduce the cooling intensity at the beginning of casting, reduce the ingot stress, and improve the ingot forming rate. The room temperature ultimate tensile strength of the standard sample of the O-state product is 140-165MPa, the yield strength is ≥70MPa, the elongation after fracture is ≥28%, and the average grain size is <90μm. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 The actual Al-Mn aluminum alloy flat ingot for the power battery shell formed in the embodiment Figure 1 ;

[0011] Figure 2 The actual Al-Mn aluminum alloy flat ingot for the power battery shell formed in the embodiment Figure 2 . DETAILED DESCRIPTION

[0012] The technical solution of the present invention is not limited to the specific implementation modes listed below, but also includes any combination of the specific implementation modes.

[0013] Specific implementation method 1: In this implementation method, a method for preparing an Al-Mn aluminum alloy flat ingot for a power battery shell is completed by the following steps:

[0014] 1. Weighing: According to the ratio of Si being 0.4% to 1.0%, Fe being 0.2% to 1.0%, Cu being 0.3% to 1.2%, Mn being 1.3% to 1.6%, Zn being 0.01% to 0.10%, Ti being 0.05% to 0.25% and the balance being Al, weigh the remelted aluminum ingot, metal Cu, metal Zn, Al-Ti master alloy, Al-Si master alloy, Fe additive and Mn additive as smelting raw materials;

[0015] 2. Melting: adding the weighed smelting raw materials into a natural gas melting furnace to melt all the added materials at a temperature of 700°C to 750°C, and then stirring the melt for 15 to 20 minutes at a temperature of 720 to 750°C and a stirring speed of 1.0 to 1.5 m / s to obtain an aluminum alloy melt;

[0016] 3. Casting: The aluminum alloy melt is introduced into a natural gas insulation furnace, refined with Ar gas at a temperature of 720-740°C, covered with 2# flux and allowed to stand for 20-30 minutes to obtain a casting melt; the casting melt is successively passed through an out-of-furnace degassing device and a filtering device, and the casting melt is made into an Al-Mn aluminum alloy flat ingot for power battery shell by a semi-continuous casting method under the conditions of a temperature of 720-750°C, a metal liquid level of 70-100mm, and a cooling water temperature of 10-25°C.

[0017] In step 1 of this embodiment, Si, Fe, Cu, Mn, Zn, and Ti are the main alloying elements, and the remaining elements are impurity elements. The lower the element content in actual production, the better. Using flux to cover the melt can reduce melt oxidation and gas absorption, thereby improving melt quality.

[0018] This embodiment strictly controls Si, Fe, Cu, Mn, Zn, Ti and other elements within a specific mass percentage range, so that the elements can play a synergistic effect. For example, Mn is a key strengthening element in Al-Mn aluminum alloys. The appropriate content (1.3% to 1.6%) can effectively improve the strength of the alloy, and can improve the overall performance of the alloy in combination with other elements. The addition of Ti (0.05% to 0.25%) can play a role in refining the grains, making the structure of the aluminum alloy more uniform and dense, which helps to improve the strength and toughness of the material, and also has a positive effect on subsequent processing performance, such as improving the forming performance of plates and strips, and reducing the problem of uneven deformation during processing. Clearly defining the content range of each element can effectively control the impurity content. For example, strictly controlling the content of elements such as Fe (0.2 to 1.0%) can avoid excessive impurities from forming coarse intermetallic compounds. These coarse compounds often become stress concentration points and reduce the performance of the material. Reasonable composition control can reduce such adverse effects, thereby improving the performance of the manufactured plates and strips.

[0019] This embodiment melts all the smelting raw materials at 700-750°C. This temperature range can not only ensure that various raw materials are fully melted, but also avoid excessive burning of certain elements or other adverse metallurgical reactions due to excessively high temperatures. For example, too high a temperature may cause a large amount of low-melting-point elements such as Zn to volatilize, change the actual composition of the alloy, and thus affect the performance of the alloy; while the appropriate temperature can ensure that each element is evenly melted into the alloy liquid in the expected proportion, laying the foundation for the subsequent acquisition of aluminum alloys with good performance. Stir the melt for 15-20 minutes at a temperature of 720-750°C and a stirring speed of 1.0-1.5m / s. Such stirring parameter settings can make the melt fully mixed and uniform. Through stirring, various added elements can be evenly distributed in the aluminum alloy melt, avoiding local element enrichment or depletion, thereby ensuring the uniformity of the alloy composition, making the subsequent plates and strips more consistent in performance, and improving the stability of product quality.

[0020] After the aluminum alloy melt is introduced into the natural gas holding furnace, it is refined with Ar gas at 720-740℃, which can effectively remove gas impurities in the melt, such as hydrogen. Gas impurities are easy to form pores during the solidification process of aluminum alloy, which seriously affects the density and performance of the material. Refining treatment can greatly reduce pore defects and improve the density and strength of the material. Covering with 2# flux and letting it stand for 20-30 minutes will help further float or sink the inclusions in the melt, play a role in purifying the melt, and further improve the purity of the aluminum alloy melt, thereby improving the internal quality of the manufactured plates and strips and improving their performance.

[0021] The gas and fine inclusions in the molten metal can be further removed by the degassing device and the filtering device outside the furnace in turn, ensuring that the quality of the molten metal entering the casting process is higher. The semi-continuous casting method is adopted under the conditions of temperature of 720-750°C, metal liquid level of 70-100mm, and cooling water temperature of 10-25°C. The fine control of these casting conditions can ensure the stability of the casting process, make the solidification structure of the ingot more uniform, reduce the occurrence of casting defects, and thus improve the surface quality and processing stability of the flat ingots produced and the subsequent processed plates and strips. Through the above-mentioned fine control and reasonable operation in terms of component ratio, smelting process and casting process, this scheme can effectively solve the problems of low performance of plates and strips produced by Al-Mn aluminum alloy flat ingots for power battery shells manufactured by existing methods, as well as poor processing stability and poor surface quality.

[0022] Specific embodiment 2: This embodiment is different from specific embodiment 1 in that in step 1, the mass percentages of Si are 0.6%, Fe is 0.5%, Cu is 0.8%, Mn is 1.4%, Zn is 0.05%, Ti is 0.1% and the balance is Al. The rest is the same as specific embodiment 1.

[0023] Specific implementation method three: This implementation method is different from specific implementation method one in that the metal Cu and metal Zn described in step one are pure metals, the Ti content in the Al-Ti master alloy is 6%, the Si content in the Al-Si master alloy is 20%, the Fe content in the Fe additive is 75%, and the Mn content in the Mn additive is 75%. Other aspects are the same as specific implementation method one.

[0024] Specific implementation method 4: This implementation method is different from the specific implementation method 1 in that the stirring in step 2 is electromagnetic stirring. The rest is the same as the specific implementation method 1.

[0025] In this embodiment, electromagnetic stirring is used for stirring, so that the chemical composition of the melt is more uniform and local overheating of the melt can be prevented.

[0026] Specific implementation method 5: This implementation method is different from the specific implementation method 1 in that: the purity of argon gas in the Ar gas refining in step 3 is ≥ 99.996%, and the gas flow rate is 13Nm 3 / hr. Other aspects are the same as those in the first embodiment.

[0027] In this embodiment, the impurities in the argon are mainly water and oxygen. These impurities react with the aluminum liquid and may produce chemical reactions that are not conducive to refining. For example, water reacts with the aluminum liquid to produce atomic hydrogen, while oxygen may cause oxidation inclusions to form in the aluminum liquid and form an aluminum oxide film on the surface of the bubble. This aluminum oxide film is very dense and prevents hydrogen from diffusing from the aluminum liquid into the bubble, thereby significantly reducing the refining effect. Therefore, the purity of the argon needs to be strictly required to ensure the refining effect and the quality of the ingot.

[0028] Specific embodiment 6: This embodiment is different from the specific embodiment 1 in that: the 2# flux in step 3 is composed of 40% KCl, 45% MgCl2, 8% BaCl2, and 7% NaCl+CaCl2 by mass percentage; the amount of 2# flux added is 0.15% of the mass of the aluminum alloy melt. The rest is the same as the specific embodiment 1.

[0029] Specific embodiment 7: This embodiment differs from specific embodiment 1 in that the degassing device in step 3 is a dual-rotor online degassing device, and the gas in the degassing device is Ar gas with a purity of 99.996%. Other aspects are the same as specific embodiment 1.

[0030] In this embodiment, a dual-rotor online degassing device is used to ensure that the liquid hydrogen content of the melt is less than 0.12 ml / 100 gAl, meeting the gas content requirements of the ingot for the battery shell.

[0031] Specific embodiment 8: This embodiment differs from specific embodiment 1 in that the filtering device in step 3 uses a double-stage ceramic filter sheet for filtering, and the double-stage ceramic filter sheet is imported 30ppi+50ppi. Others are the same as specific embodiment 1.

[0032] In this embodiment, the filtering device adopts imported ceramic filter plates. The main reason is that the imported ceramic filter plates are more advanced in production technology, can ensure higher filtering efficiency and longer service life, have higher stability and reliability, and can effectively remove inclusions in the melt.

[0033] Specific embodiment 9: This embodiment differs from the specific embodiment 1 in that: in the semi-continuous casting process described in step 3, the cooling water is firstly pulsed with a single row of water for 30 to 40 m 3 / h for cooling, the casting speed is 40-45mm / min, and the casting length is 140mm; the cooling water is 50-60m 3 / h double-row pulse water cooling, casting speed is 45-50mm / min, casting to length 600mm; cooling water is double-row pulse water 100-110m 3 / h for cooling, the casting speed is 50-60mm / min, and the casting is continued. Other aspects are the same as those in the first embodiment.

[0034] In this embodiment, an advanced double-row pulse water cooling control system is adopted to provide a stable water flow for casting; single-row water cooling technology is adopted in the early stage of semi-continuous casting to reduce cooling intensity, stress, and warping, thereby avoiding aluminum leakage or hanging of the ingot due to excessive warping; double-row water cooling technology is used in the later stage to increase the cooling intensity during the transition period, thereby avoiding insufficient cooling of the ingot during the transition period and overheating and cracking.

[0035] Specific embodiment 10: This embodiment differs from specific embodiment 1 in that the size of the Al-Mn aluminum alloy flat ingot for the power battery shell in step 3 is 630 mm×1050 mm×7000 mm. The rest is the same as specific embodiment 1.

[0036] The following examples are used to verify the beneficial effects of the present invention:

[0037] Embodiment 1: A method for preparing an Al-Mn aluminum alloy flat ingot for a power battery shell is completed by the following steps:

[0038] 1. Weighing: According to the mass percentage, Si is 0.6%, Fe is 0.5%, Cu is 0.8%, Mn is 1.4%, Zn is 0.05%, Ti is 0.1% and the balance is Al, and remelted aluminum ingots, metal Cu, metal Zn, Al-Ti master alloy, Al-Si master alloy, Fe additive, and Mn additive are weighed as smelting raw materials;

[0039] 2. Melting: Add the weighed smelting raw materials into a natural gas melting furnace and melt all the added materials at a temperature of 735°C, then stir the melt for 20 minutes at a temperature of 740°C and a stirring speed of 1.2 m / s to obtain an aluminum alloy melt;

[0040] 3. Casting: The aluminum alloy melt is introduced into a natural gas insulation furnace, refined with Ar gas at a temperature of 720-740°C, covered with 2# flux and allowed to stand for 20-30 minutes to obtain a casting melt; the casting melt is sequentially passed through an out-of-furnace degassing device and a filtering device, and the casting melt is made into an Al-Mn aluminum alloy flat ingot for a power battery shell by a semi-continuous casting method under the conditions of a temperature of 740°C, a metal liquid level of 70-100mm, and a cooling water temperature of 21°C; during the semi-continuous casting process, the cooling water is firstly cooled by a single row of pulse water for 30-40m 3 / h for cooling, the casting speed is 40-45mm / min, and the casting length is 140mm; the cooling water is 50-60m 3 / h double-row pulse water cooling, casting speed is 45-50mm / min, casting to length 600mm; cooling water is double-row pulse water 100-110m 3 / h for cooling, the casting speed is 50-60mm / min, and casting is continued.

[0041] In this embodiment, the Al-Mn series 630mm×1050mm×7000mm flat ingot for battery shell for ultra-wide wallboard has qualified chemical composition, no surface defects such as cracks, cold shuts, slag inclusions, etc., and the standard sample of the strip product in O state after rolling has an ultimate tensile strength of 153MPa at room temperature, a yield strength of 78MPa, an elongation after fracture of 31%, and an average grain size of 80μm. The surface of the strip is smooth and has no defects such as periodic adhesion and marks.

Claims

1. A method for preparing an Al-Mn aluminum alloy flat ingot for a power battery shell, characterized in that The preparation method of the Al-Mn aluminum alloy flat ingot for the power battery shell is completed in the following steps:

1. Weighing: According to the ratio of Si being 0.4% to 1.0%, Fe being 0.2% to 1.0%, Cu being 0.3% to 1.2%, Mn being 1.3% to 1.6%, Zn being 0.01% to 0.10%, Ti being 0.05% to 0.25% and the balance being Al, weigh the remelted aluminum ingot, metal Cu, metal Zn, Al-Ti master alloy, Al-Si master alloy, Fe additive and Mn additive as smelting raw materials; 2. Melting: adding the weighed smelting raw materials into a natural gas melting furnace to melt all the added materials at a temperature of 700°C to 750°C, and then stirring the melt for 15 to 20 minutes at a temperature of 720 to 750°C and a stirring speed of 1.0 to 1.5 m / s to obtain an aluminum alloy melt; 3. Casting: The aluminum alloy melt is introduced into a natural gas insulation furnace, refined with Ar gas at a temperature of 720-740°C, covered with 2# flux and allowed to stand for 20-30 minutes to obtain a casting melt; the casting melt is sequentially passed through an out-of-furnace degassing device and a filtering device, and the temperature is 720-750°C, the casting speed is 35-60mm / min, the metal liquid level is 70-100mm, and the cooling water flow rate is 30-130m 3 / h and a cooling water temperature of 10 to 25°C, a semi-continuous casting method is used to make the casting melt into an Al-Mn aluminum alloy flat ingot for a power battery shell.

2. The method for preparing an Al-Mn aluminum alloy flat ingot for a power battery shell according to claim 1, characterized in that In step 1, the proportions are as follows: Si is 0.6%, Fe is 0.5%, Cu is 0.8%, Mn is 1.4%, Zn is 0.05%, Ti is 0.1% and the balance is Al.

3. The method for preparing an Al-Mn aluminum alloy flat ingot for a power battery shell according to claim 1, characterized in that The metal Cu and metal Zn described in step 1 are pure metals, the Ti content in the Al-Ti master alloy is 6%, the Si content in the Al-Si master alloy is 20%, the Fe content in the Fe additive is 75%, and the Mn content in the Mn additive is 75%.

4. The method for preparing an Al-Mn aluminum alloy flat ingot for a power battery shell according to claim 1, characterized in that The stirring in step 2 is electromagnetic stirring.

5. The method for preparing an Al-Mn aluminum alloy flat ingot for a power battery shell according to claim 1, characterized in that The purity of argon gas in the Ar gas refining in step 3 is ≥99.996%, and the gas flow rate is 13Nm 3 / hr.

6. The method for preparing an Al-Mn aluminum alloy flat ingot for a power battery shell according to claim 1, characterized in that The 2# flux described in step 3 is composed of 40% KCl, 45% MgCl2, 8% BaCl2, and 7% NaCl+CaCl2 in mass percentage; the added amount of 2# flux is 0.15% of the mass of the aluminum alloy melt.

7. The method for preparing an Al-Mn aluminum alloy flat ingot for a power battery shell according to claim 1, characterized in that The degassing device described in step three is a dual-rotor online degassing device, and the gas in the degassing device is Ar gas with a purity of 99.996%.

8. The method for preparing an Al-Mn aluminum alloy flat ingot for a power battery shell according to claim 1, characterized in that The filtering device described in step three uses a double-stage ceramic filter for filtering, and the double-stage ceramic filter is imported 30ppi+50ppi.

9. The method for preparing an Al-Mn aluminum alloy flat ingot for a power battery shell according to claim 1, characterized in that In the semi-continuous casting process described in step 3, the cooling water is firstly pulsed with single row water for 30-40m 3 / h for cooling, casting speed is 40~45mm / min, casting to length 140mm; cooling water is 50~60m 3 / h double-row pulse water cooling, casting speed is 45-50mm / min, casting to length 600mm; cooling water is double-row pulse water 100-110m 3 / h for cooling, the casting speed is 50-60mm / min, and casting is continued.

10. The method for preparing an Al-Mn aluminum alloy flat ingot for a power battery shell according to claim 1, characterized in that The size of the Al-Mn aluminum alloy flat ingot for the power battery shell in step 3 is 630mm×1050mm×7000mm.

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