High pressure die casting motor rotor casting aluminum alloy and its preparation method

Abstract

The application discloses a high-pressure die-casting motor rotor casting aluminum alloy and a preparation method thereof, and belongs to the technical field of motor rotor materials. The high-pressure die-casting motor rotor casting aluminum alloy comprises the following components in percentage by mass: Mg 0.75-0.85 wt%, Fe 0.15-0.25 wt%, Ti≤0.03 wt%, Ga≤0.03 wt%, Zn≤0.03 wt%, Cu≤0.03 wt%, Mn≤0.01 wt%, Si≤0.01 wt%, other impurities≤0.35 wt%, and the balance of Al. The type of elements and the percentage by mass of each element are specifically limited, the percentage by mass of Si is reduced, the influence of Si on the electrical conductivity of the aluminum alloy is reduced, the electrical conductivity of the aluminum alloy is improved to a certain extent, the percentage by mass of Mg and Fe is limited, Mg forms a solid solution in Al, Fe interacts with Al to form phases such as Al3Fe, and the strength and hardness of the aluminum alloy are improved, so that the balance between the mechanical properties and the electrical conductivity of the motor rotor casting aluminum alloy is achieved.

Description

Technical Field

[0001] This application relates to a high-pressure die-casting aluminum alloy for motor rotors and its preparation method, belonging to the field of motor rotor material technology. Background Technology

[0002] With the increasing severity of energy and environmental issues, the development of new energy vehicles has attracted growing attention. The electric motor is one of the core components of a new energy vehicle chassis, and the motor rotor is a crucial part of the motor. Traditionally, motor rotors primarily used copper, but due to the high price of copper and the lightweight requirements of new energy vehicles, aluminum is gradually being used as a substitute to reduce raw material costs and achieve the goal of lightweight components.

[0003] In the preparation method of cast aluminum rotors for new energy vehicles, Al99.50b aluminum ingots, which are typically used for primary remelting, are conventionally employed. Although this type of motor rotor has relatively high plasticity, corrosion resistance, and electrical conductivity, it has low strength. The tensile strength of the aluminum alloy is only 60-80 MPa, and the yield strength is only 25-65 MPa. Furthermore, heat treatment cannot achieve a strengthening effect, and its machinability is poor.

[0004] In current technologies, various other metallic elements are added to molten aluminum to improve the electrical and mechanical properties of the motor rotor alloy. However, the addition of multiple metallic elements not only increases costs and hinders large-scale production, but also leads to improvements in one rotor property while others deteriorate. For example, silicon (Si) is typically added to the cast aluminum alloy of motor rotors, resulting in the formation of the Al-Si phase, which helps improve the alloy's hardness and wear resistance. However, Si, as a semiconductor material, significantly reduces the effective conductive interface of the aluminum substrate, lowering the alloy's conductivity.

[0005] Patent WO2020028730A1 discloses an Al-Ni system high conductivity cast aluminum alloy for use in asynchronous motor rotors, with a Ni content of 4-6 wt%. The high price of nickel (about 7 times that of aluminum) has led to an increase of about 35% in the raw material price of this aluminum alloy. The significant price increase is not conducive to large-scale promotion and application.

[0006] Therefore, it is necessary to develop an aluminum alloy for new energy vehicle motor rotors that achieves a balance between mechanical properties, electrical properties, and production costs to meet actual production needs. Summary of the Invention

[0007] To address the aforementioned issues, a high-pressure die-casting aluminum alloy for motor rotors and its preparation method are provided. By specifically limiting the types and mass percentages of elements, the mass percentage of Si is reduced, thereby decreasing its impact on the electrical conductivity of the aluminum alloy and improving the conductivity to a certain extent. Furthermore, the mass percentages of Mg and Fe are limited, allowing Mg to form a solid solution in Al and Fe to interact with Al to form phases such as Al3Fe, thereby improving the strength and hardness of the aluminum alloy and achieving a balance between the mechanical properties and electrical conductivity of the die-cast aluminum alloy for motor rotors.

[0008] According to one aspect of this application, a high-pressure die-casting motor rotor aluminum alloy is provided, comprising the following components by mass percentage: Mg 0.75-0.85 wt%, Fe 0.15-0.25 wt%, Ti ≤0.03 wt%, Ga ≤0.03 wt%, Zn ≤0.03 wt%, Cu ≤0.03 wt%, Mn ≤0.01 wt%, Si ≤0.01 wt%, other impurities ≤0.35 wt%, and the balance being Al.

[0009] Specifically, the electrical conductivity of aluminum mainly depends on the migration of free electrons formed by metallic bonds. Si, as a semiconductor element, readily exists in aluminum alloys in a free state or as a silicon phase (such as α-Al+Si eutectic). When the Si content is high, coarse needle-like or plate-like silicon phases form, disrupting the continuous conductive path of the aluminum matrix and reducing the effective conductive cross-section. Furthermore, the conductivity of the silicon phase itself is much lower than that of pure aluminum, leading to a decrease in the overall conductivity of the alloy. This application controls the Si content to ≤0.01wt%, allowing it to exist almost entirely in a solid solution state within the aluminum matrix, avoiding the formation of independent silicon phases. This maximizes the preservation of the conductive continuity of the aluminum matrix, increasing the conductivity to ≥32 MS / m.

[0010] Optionally, the content ratio of Mg to Fe is (3.5 to 5.5): 1.

[0011] Optionally, the content ratio of Mg to Al is 1:(120-130); the content ratio of Fe to Al is 1:(450-600).

[0012] Specifically, magnesium forms a solid solution in aluminum, which can increase the strength and hardness of aluminum alloys and improve their mechanical properties. In the Al-Fe-Mg system formed in this application, the three elements interact to form different phases, such as the Al3Fe phase, which can improve the strength of the alloy while maintaining good ductility.

[0013] Optionally, the high-pressure die-cast motor rotor aluminum alloy has a tensile strength of at least 150 MPa, a yield strength of at least 90 MPa, an electrical conductivity of at least 32 MS / m, and an elongation of at least 15%.

[0014] Specifically, the high-pressure die-cast motor rotor aluminum alloy provided in this application can balance mechanical strength, electrical conductivity and ductility, and achieve a balance between mechanical properties, electrical properties and production costs.

[0015] According to another aspect of this application, a method for preparing the above-mentioned high-pressure die-casting motor rotor aluminum alloy is also provided, comprising the following steps:

[0016] (1) According to the composition ratio of aluminum alloy for high pressure die casting motor rotor, each raw material component is placed in a melting furnace for melting to obtain a melt;

[0017] (2) The obtained melt is refined using argon gas;

[0018] (3) The refined melt is allowed to stand and then subjected to high-pressure die casting to obtain the casting.

[0019] (4) Heat treatment is performed on the casting to obtain high pressure die-cast motor rotor aluminum alloy.

[0020] Optionally, in step (1), the melting temperature is 690-715°C; preferably, the melting temperature is 700°C.

[0021] Optionally, the refining temperature in step (2) is 705-730°C and the refining time is 15-20 min; preferably, the refining temperature in step (2) is 720°C and the refining time is 15 min.

[0022] Optionally, the high-pressure die casting temperature in step (3) is 695-715°C and the high-pressure die casting pressure is 650-750 MPa; preferably, the high-pressure die casting temperature is 705°C and the high-pressure die casting pressure is 700 MPa.

[0023] Optionally, the heat treatment involves heating the casting to 180-200°C at a heating rate of 90-100°C / h, holding it at that temperature for 20 hours, and then air-cooling it to room temperature.

[0024] According to another aspect of this application, the application of the high-pressure die-cast motor rotor aluminum alloy described above or the high-pressure die-cast motor rotor aluminum alloy prepared by the above method in new energy vehicles is also provided.

[0025] The beneficial effects of this application include, but are not limited to:

[0026] 1. The high-pressure die-casting aluminum alloy for motor rotors according to this application, by specifically limiting the types of elements and the mass percentage of each element, reduces the mass percentage of Si, thereby reducing its influence on the electrical conductivity of the aluminum alloy and improving the electrical conductivity of the aluminum alloy to a certain extent; and by limiting the mass percentage of Mg and Fe, Mg forms a solid solution in Al, and Fe interacts with Al to form phases such as Al3Fe, thereby improving the strength and hardness of the aluminum alloy and achieving a balance between the mechanical properties and electrical conductivity of the die-cast aluminum alloy for motor rotors.

[0027] 2. According to the high-pressure die-casting motor rotor casting aluminum alloy of this application, the atomic radius of Mg is close to that of Al, which easily forms a substitutional solid solution. After Mg atoms dissolve into the Al lattice, on the one hand, it causes lattice distortion, increases the resistance to dislocation movement, realizes solid solution strengthening, and greatly improves tensile strength; on the other hand, it forms Mg atom clusters or short-range ordered structures, which can induce precipitates (such as Mg2Si) in subsequent heat treatment, further strengthening the alloy; Fe and Al form Al3Fe intermetallic compounds, which are distributed in rod-shaped or needle-shaped forms at grain boundaries or within grains. The hardness of the Al3Fe phase is higher than that of the aluminum matrix, and the alloy strength is improved through dispersion strengthening; the Al3Fe phase formed by an appropriate amount of Fe content is small in size, avoiding brittleness caused by coarse phases.

[0028] 3. According to the high-pressure die-casting motor rotor casting aluminum alloy of this application, when the Mg / Fe ratio is between 3.5 and 5.5, the system tends to form a mixed strengthening phase of Mg2Si and Al3Fe, rather than a single brittle phase; the Mg2Si phase provides high strength, and the Al3Fe phase supplements toughness. The alternating distribution of the two can suppress crack propagation; under this ratio, the volume fraction of Mg solid solution and Fe strengthening phase is matched to achieve a balance between strength and elongation.

[0029] 4. The high-pressure die-casting motor rotor made of aluminum alloy according to this application has simple and readily available raw materials, low cost, simple preparation process, and is easy to promote and utilize on a large scale. Detailed Implementation

[0030] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of skill in the art. The reagents and raw materials used in this invention are readily available through conventional means, and unless otherwise specified, they shall be used in accordance with conventional methods in the art or as per the product instructions. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to the methods of this invention. The preferred embodiments and materials described in this patent are for illustrative purposes only.

[0032] Example 1

[0033] A high-pressure die-casting aluminum alloy for motor rotors comprises the following components by mass percentage: Mg 0.75wt%, Fe 0.15wt%, Ti 0.03wt%, Ga 0.03wt%, Zn 0.03wt%, Cu 0.03wt%, Mn 0.01wt%, Si 0.01wt%, other impurities 0.35wt%, with the balance being Al.

[0034] A method for preparing high-pressure die-cast motor rotor aluminum alloy includes the following steps:

[0035] (1) According to the composition ratio of the aluminum alloy for high-pressure die-casting motor rotor, each raw material component is placed in a melting furnace for melting to obtain a melt; the melting temperature is 690℃;

[0036] (2) The obtained melt was refined by argon gas at a temperature of 705℃ for 15 min.

[0037] (3) The refined melt is allowed to stand for 30 minutes and then high pressure die casting is performed. The high pressure die casting temperature is 695℃ and the high pressure die casting pressure is 650MPa to obtain the casting.

[0038] (4) The casting is heat-treated by heating the casting to 180°C at a heating rate of 90°C / h, holding it at that temperature for 20h, and then air-cooling it to room temperature to obtain a high-pressure die-cast motor rotor aluminum alloy.

[0039] Example 2

[0040] A high-pressure die-casting aluminum alloy for motor rotors comprises the following components by mass percentage: Mg 0.85wt%, Fe 0.25wt%, Ti 0.02wt%, Ga 0.02wt%, Zn 0.02wt%, Cu 0.02wt%, Mn 0.01wt%, Si 0.01wt%, other impurities 0.25wt%, with the balance being Al.

[0041] A method for preparing high-pressure die-cast motor rotor aluminum alloy includes the following steps:

[0042] (1) According to the composition ratio of the aluminum alloy for high-pressure die-casting motor rotor, each raw material component is placed in a melting furnace for melting to obtain a melt; the melting temperature is 715℃.

[0043] (2) The obtained melt was refined by argon gas at a temperature of 730℃ for 20 min.

[0044] (3) The refined melt is allowed to stand for 50 minutes and then high pressure die casting is performed. The high pressure die casting temperature is 715℃ and the high pressure die casting pressure is 750MPa to obtain the casting.

[0045] (4) The casting is heat-treated by heating the casting to 200°C at a heating rate of 100°C / h, holding it at that temperature for 20h, and then air-cooling it to room temperature to obtain a high-pressure die-cast motor rotor aluminum alloy.

[0046] Example 3

[0047] A high-pressure die-casting motor rotor aluminum alloy comprises the following components by mass percentage: Mg 0.80wt%, Fe 0.20wt%, Ti 0.01wt%, Ga 0.01wt%, Zn 0.01wt%, Cu 0.01wt%, Mn 0.01wt%, Si 0.01wt%, other impurities 0.35wt%, and the balance being Al.

[0048] A method for preparing high-pressure die-cast motor rotor aluminum alloy includes the following steps:

[0049] (1) According to the composition ratio of the aluminum alloy for high-pressure die-casting motor rotor, each raw material component is placed in a melting furnace for melting to obtain a melt; the melting temperature is 700℃;

[0050] (2) The obtained melt was refined by argon gas at a temperature of 720℃ for 18 minutes.

[0051] (3) The refined melt is allowed to stand for 30 minutes and then high pressure die casting is performed. The high pressure die casting temperature is 705℃ and the high pressure die casting pressure is 700MPa to obtain the casting.

[0052] (4) The casting is heat-treated by heating the casting to 190°C at a heating rate of 95°C / h, holding it at that temperature for 20h, and then air-cooling it to room temperature to obtain a high-pressure die-cast motor rotor aluminum alloy.

[0053] Comparative Example 1

[0054] The difference between Comparative Example 1 and Example 3 is that the mass percentage of Mg is 0.7, while all other aspects are the same.

[0055] Comparative Example 2

[0056] The difference between Comparative Example 2 and Example 3 is that the mass percentage of Mg is 0.9, while all other aspects are the same.

[0057] Comparative Example 3

[0058] The difference between Comparative Example 3 and Example 3 is that the mass percentage of Fe is 0.1%, while all other aspects are the same.

[0059] Comparative Example 4

[0060] The difference between Comparative Example 4 and Example 3 is that the mass percentage of Fe is 0.3, while all other aspects are the same.

[0061] Comparative Example 5

[0062] The difference between Comparative Example 5 and Example 3 is that Mg is not included; otherwise, they are the same.

[0063] Comparative Example 6

[0064] The difference between Comparative Example 6 and Example 3 is that it does not include the Fe element, but all other aspects are the same.

[0065] Comparative Example 7

[0066] The difference between Comparative Example 7 and Example 3 is that the heat treatment conditions in step (4) of this comparative example are as follows: the casting is heated to 160°C at a heating rate of 80°C / h, held for 20h and then air-cooled to room temperature, and the rest are the same.

[0067] Comparative Example 8

[0068] The difference between Comparative Example 8 and Example 3 is that centrifugal die casting is used in step (3). The centrifugal die casting steps are as follows: the mold is preheated to 540°C and cast at 520°C and 300r / min. After the melt solidifies, the centrifugal casting equipment stops rotating to obtain the casting. The casting is then naturally cooled to room temperature.

[0069] Experimental Example 1

[0070] Samples were taken from the end faces of the high-pressure die-cast motor rotor aluminum alloys prepared in the above embodiments and comparative examples, and their performance was tested. The conductivity test specimens met the requirements of GB / T12966 2008 and were tested for conductivity. The mechanical property test specimens met the standard of ASTM E8 and were analyzed for tensile properties. The specific test results are shown in Table 1 below:

[0071] Table 1 Performance Test Results

[0072]

[0073]

[0074] Table 1 shows that the high-pressure die-casting motor rotor aluminum alloy prepared in the embodiments of this application can balance mechanical properties, electrical conductivity, and ductility. In Comparative Example 1, insufficient Mg content leads to decreased tensile strength but improved ductility; in Comparative Example 2, although Mg can improve strength, excessive content exacerbates lattice distortion and reduces elongation; in Comparative Example 4, excessive Fe easily forms coarse and brittle phases, resulting in a significant reduction in elongation; in Comparative Examples 5 and 6, element deficiency significantly reduces strength; in Comparative Example 7, the low heat treatment temperature results in less precipitation of strengthening phases and reduced strength; in Comparative Example 8, centrifugal die casting affects density and thus strength.

[0075] The above description is merely an embodiment of this application, and the scope of protection of this application is not limited to these specific embodiments, but is determined by the claims of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the technical concept and principles of this application should be included within the scope of protection of this application.

Claims

1. A high-pressure die-casting aluminum alloy for motor rotors, characterized in that, The composition comprises the following components by mass percentage: Mg 0.75–0.85 wt%, Fe 0.15–0.25 wt%, Ti ≤0.03 wt%, Ga ≤0.03 wt%, Zn ≤0.03 wt%, Cu ≤0.03 wt%, Mn ≤0.01 wt%, Si ≤0.01 wt%, other impurities ≤0.35 wt%, and the balance being Al; the Mg to Fe content ratio is (3.5–5.5):1; the Mg to Al content ratio is 1:(120–130); the Fe to Al content ratio is 1:(450–600); the high-pressure die-cast motor rotor aluminum alloy has a tensile strength of at least 150 MPa, a yield strength of at least 90 MPa, an electrical conductivity of at least 32 MS / m, and an elongation of at least 15%. The method for preparing the high-pressure die-cast motor rotor aluminum alloy includes the following steps: (1) According to the composition ratio of aluminum alloy for high pressure die casting motor rotor, each raw material component is placed in a melting furnace for melting to obtain a melt; (2) The obtained melt is refined using argon gas; (3) The refined melt is allowed to stand and then subjected to high-pressure die casting to obtain the casting. (4) Heat treatment is performed on the casting to obtain high pressure die-cast motor rotor aluminum alloy; The high-pressure die casting temperature in step (3) is 695-715℃, and the high-pressure die casting pressure is 650-750MPa; the standing time in step (3) is not less than 30min; the heat treatment is to heat the casting to 180-200℃ at a heating rate of 90-100℃ / h, keep it at that temperature for 20h, and then air cool it to room temperature.

2. The high-pressure die-casting motor rotor aluminum alloy according to claim 1, characterized in that, In step (1), the melting temperature is 690-715℃.

3. The high-pressure die-casting motor rotor aluminum alloy according to claim 2, characterized in that, In step (1), the melting temperature is 700°C.

4. The high-pressure die-casting aluminum alloy for motor rotors according to claim 1, characterized in that, The refining temperature in step (2) is 705-730℃; the refining time is 15-20 min.

5. The high-pressure die-casting aluminum alloy for motor rotors according to claim 4, characterized in that, The refining temperature in step (2) is 720℃; the refining time is 15min.

6. The high-pressure die-casting aluminum alloy for motor rotors according to claim 1, characterized in that, The high-pressure die-casting temperature is 705℃, and the high-pressure die-casting pressure is 700MPa.

7. The application of high-pressure die-casting motor rotor aluminum alloy according to any one of claims 1 to 6 in new energy vehicles.

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