A high-strength aluminum alloy for motor rotors and its high-pressure casting method and application

Abstract

This invention provides a high-strength aluminum alloy for motor rotors, its high-pressure die-casting method, and its application, relating to the field of materials technology for motor rotors in new energy vehicles. The high-strength aluminum alloy for motor rotors of this invention comprises Si 0.28-0.32%, Mg 0.68-0.74%, Fe 0.3-0.35%, Ti≤0.05%, Ga≤0.03%, Zn≤0.03%, Cu≤0.03%, Mn≤0.01%, unavoidable impurities ≤0.01%, and the balance being Al. By introducing Mg, Si, and Fe into the aluminum alloy and adjusting the proportions of each element, it achieves good fluidity and castability. Defects such as porosity and cracks do not occur during high-pressure die-casting. The resulting rotor also possesses excellent toughness, ductility, and mechanical properties, overcoming the shortcomings of existing technologies and suitable for industrial application.

Description

Technical Field

[0001] This invention relates to the field of new energy vehicle motor rotor material technology, and in particular to a high-strength motor rotor aluminum alloy and its high-pressure casting method and application. Background Technology

[0002] The motor rotor, as the rotating component of a motor, is a crucial part for converting electrical energy into mechanical energy and is one of the key factors determining motor efficiency. Currently, cast aluminum rotors used in new energy vehicles mainly use high-purity aluminum, and the casting processes are primarily high-pressure casting and centrifugal casting. However, with the rapid development of new energy vehicles, the requirements for motor rotors are becoming increasingly stringent. Generally, other metallic elements are added within a certain range to improve their electrical conductivity or mechanical properties.

[0003] However, the metal elements added in existing technologies are expensive, have poor performance improvement effects, or cannot simultaneously meet the improvement of multiple performance requirements, resulting in low cost-effectiveness. On the other hand, the addition of metal elements will affect its casting and processing performance. For example, in the high-pressure die casting of rotors, although adding Si elements to the alloy can improve the fluidity and castability of aluminum alloys, it can also easily lead to some negative effects. For example, Si elements can easily form large silicon particles in the casting, reducing the toughness and ductility of the rotor, and may also cause defects on the surface of the casting, such as porosity and cracks.

[0004] Therefore, it is necessary to improve the existing motor rotor to meet actual production needs. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a high-strength aluminum alloy for motor rotors, its high-pressure casting method, and its application, which can at least solve some of the problems existing in the prior art.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] On the one hand, a high-strength motor rotor aluminum alloy, by weight percentage, comprises the following components:

[0008] Si 0.28-0.32%, Mg 0.68-0.74%, Fe 0.3-0.35%, Ti≤0.05%, Ga≤0.03%, Zn≤0.03%, Cu≤0.03%, Mn≤0.01%, unavoidable impurities≤0.01%, balance Al.

[0009] Preferably, the content ratio of Si to Mg is 1:(2.1-2.6), more preferably 3:7.

[0010] Preferably, the total content of Si, Mg and Fe is ≤1.35%, more preferably ≤1.3%.

[0011] On the other hand, a high-pressure casting method for a high-strength motor rotor aluminum alloy as described above includes the following steps:

[0012] S1. The alloy raw materials are added to the melting furnace and melted to obtain a melt;

[0013] S2. The melt is refined using argon gas;

[0014] S3. After the melt has been refined in step S2, it is left to stand for more than 30 minutes and then subjected to high-pressure die casting to obtain the casting.

[0015] S4. Heat treat the casting obtained in step S3 to obtain the high-strength motor rotor aluminum alloy.

[0016] Further, in step S1, the melting temperature is 710-750℃; preferably, the melting temperature is 730℃.

[0017] Further, in step S2, the refining temperature is 720-740℃ and the refining time is 15-20 min; preferably, the refining temperature is 730℃ and the refining time is 15 min.

[0018] Further, in step S3, the high-pressure die-casting temperature is 705-725℃, and the high-pressure die-casting pressure is 650-750MPa; preferably, the high-pressure die-casting temperature is 715℃, and the high-pressure die-casting pressure is 700MPa.

[0019] Further, in step S4, the heat treatment step is as follows: the casting is heated to 180-200℃ at a heating rate of 90-100℃ / h, held at that temperature for 20h, and then air-cooled to room temperature to obtain a high-strength motor rotor aluminum alloy.

[0020] On the other hand, the above-mentioned high-strength motor rotor aluminum alloy is applicable to the rotor of new energy vehicle motors.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. This invention provides a high-strength motor rotor aluminum alloy and its high-pressure die-casting method and application. By introducing Mg, Si and Fe into the aluminum alloy and adjusting the ratio of each element to a reasonable level, it can achieve good fluidity and castability. During the high-pressure die-casting process, defects such as porosity and cracks will not occur. The resulting rotor also has excellent toughness, ductility and mechanical properties, which makes up for the deficiencies of the prior art and is suitable for industrial promotion.

[0023] 2. The high-strength motor rotor aluminum alloy of the present invention introduces Mg, Si, and Fe into the aluminum alloy. Si readily forms a solid solution with aluminum and usually exists as a strengthening phase to improve the strength and hardness of the alloy, as well as improve the casting performance of the aluminum alloy. The addition of Mg can also enhance the strength, hardness, and corrosion resistance of the alloy. The introduction of Fe will form Al-Fe-Si phases (such as the θ phase), which exist in the alloy in the form of aluminum-iron compounds. The presence of these compounds helps to improve the mechanical properties and corrosion resistance of the alloy. However, the presence of Fe will also promote the formation of some hardening phases such as Al5FeSi, and Mg will form Mg2Si with aluminum (especially in the presence of Si). While these second phases improve the strength of the alloy, they will lead to a decrease in the ductility of the alloy and will also cause porosity and cracks during high-pressure die casting, affecting product quality. This invention reduces the risk of hot cracking by limiting the silicon-magnesium content ratio to 3:7 and the total content of Si, Mg and Fe to ≤1.3%. In particular, during casting and cooling, the alloy's crystal structure is more uniform, reducing the tendency for hot cracking. While improving the mechanical properties of the product, its toughness and ductility are also improved. Detailed Implementation

[0024] The following non-limiting embodiments are intended to enable those skilled in the art to gain a more comprehensive understanding of the present invention, but do not limit the invention in any way. The following description is merely an exemplary illustration of the scope of protection of the present invention, and those skilled in the art can make various changes and modifications to the invention based on the disclosed content, which should also fall within the scope of protection of the present invention.

[0025] The present invention will be further described below by way of specific embodiments. Unless otherwise specified, all chemical reagents used in the embodiments of the present invention are obtained through conventional commercial means.

[0026] Example 1

[0027] A high-strength aluminum alloy for motor rotors, comprising the following components by weight percentage:

[0028] Si 0.32%, Mg 0.68%, Fe 0.35%, Ti 0.05%, Ga 0.03%, Zn 0.03%, Cu 0.03%, Mn 0.01%, unavoidable impurities 0.01%, balance Al.

[0029] The preparation method of the above-mentioned high-strength motor rotor aluminum alloy includes the following steps:

[0030] S1. According to the formula, the alloy raw materials are added to the melting furnace and melted at 710°C to obtain the melt;

[0031] S2. The melt is refined using argon gas at a temperature of 720°C for 20 minutes.

[0032] S3. After refining in step S2, the melt is allowed to stand for 30 minutes, and then high-pressure die casting is performed at 705℃ and 750MPa to obtain the casting.

[0033] S4. Heat the casting to 180℃ at a heating rate of 90℃ / h, hold for 20h, and then air cool to room temperature to obtain a high-strength motor rotor aluminum alloy.

[0034] Example 2

[0035] A high-strength aluminum alloy for motor rotors, comprising the following components by weight percentage:

[0036] Si 0.3%, Mg 0.7%, Fe 0.3%, Ti 0.03%, Ga 0.02%, Zn 0.02%, Cu 0.01%, Mn 0.01%, unavoidable impurities 0.01%, balance Al.

[0037] The preparation method of the above-mentioned high-strength motor rotor aluminum alloy includes the following steps:

[0038] S1. According to the formula, add the alloy raw materials into the melting furnace and melt them at 730°C to obtain the melt;

[0039] S2. The melt is refined using argon gas at a temperature of 730°C for 15 minutes.

[0040] S3. After refining in step S2, the melt is allowed to stand for 50 minutes, and then high-pressure die casting is performed at 715℃ and 700MPa to obtain the casting.

[0041] S4. Heat the casting to 180℃ at a heating rate of 100℃ / h, hold for 20h, and then air cool to room temperature to obtain a high-strength motor rotor aluminum alloy.

[0042] Example 3

[0043] A high-strength aluminum alloy for motor rotors, comprising the following components by weight percentage:

[0044] Si 0.28%, Mg 0.74%, Fe 0.3%, Ti 0.03%, Ga 0.02%, Zn 0.02%, Cu 0.01%, Mn 0.01%, unavoidable impurities 0.01%, balance Al.

[0045] The preparation method of the above-mentioned high-strength motor rotor aluminum alloy includes the following steps:

[0046] S1. According to the formula, add the alloy raw materials into the melting furnace and melt them at 750°C to obtain the melt;

[0047] S2. The melt is refined using argon gas at a temperature of 740°C for 15 minutes.

[0048] S3. After refining in step S2, the melt is allowed to stand for 60 minutes, and then high-pressure die casting is performed at 725℃ and 650MPa to obtain the casting.

[0049] S4. Heat the casting to 200℃ at a heating rate of 100℃ / h, hold for 20h, and then air cool to room temperature to obtain a high-strength motor rotor aluminum alloy.

[0050] Comparative Example 1

[0051] The difference between this comparative example and Example 2 is that the mass percentage of Si in the high-strength motor rotor aluminum alloy of this comparative example is 0.26%.

[0052] Comparative Example 2

[0053] The difference between this comparative example and Example 2 is that the mass percentage of Si in the high-strength motor rotor aluminum alloy of this comparative example is 0.34%.

[0054] Comparative Example 3

[0055] The difference between this comparative example and Example 2 is that the mass percentage of Mg in the high-strength motor rotor aluminum alloy of this comparative example is 0.62%.

[0056] Comparative Example 4

[0057] The difference between this comparative example and Example 2 is that the mass percentage of Mg in the high-strength motor rotor aluminum alloy of this comparative example is 0.8%.

[0058] Comparative Example 5

[0059] The difference between this comparative example and Example 2 is that the mass percentage of Fe in the high-strength motor rotor aluminum alloy of this comparative example is 0.28%.

[0060] Comparative Example 6

[0061] The difference between this comparative example and Example 2 is that the mass percentage of Fe in the high-strength motor rotor aluminum alloy of this comparative example is 0.38%.

[0062] Comparative Example 7

[0063] The difference between this comparative example and Example 2 is that Si was not added to the high-strength motor rotor aluminum alloy in this comparative example.

[0064] Comparative Example 8

[0065] The difference between this comparative example and Example 2 is that Mg was not added to the high-strength motor rotor aluminum alloy in this comparative example.

[0066] Comparative Example 9

[0067] The difference between this comparative example and Example 2 is that Fe was not added to the high-strength motor rotor aluminum alloy in this comparative example.

[0068] Comparative Example 10

[0069] The difference between this comparative example and Example 2 is that the heat treatment conditions in step S4 of this comparative example are as follows: the casting is heated to 160°C at a heating rate of 80°C / h, held at that temperature for 20h, and then air-cooled to room temperature to obtain a high-strength motor rotor aluminum alloy.

[0070] Comparative Example 11

[0071] The difference between this comparative example and Example 2 is that the heat treatment conditions in step S4 of this comparative example are as follows: the casting is heated to 220°C at a heating rate of 110°C / h, held at that temperature for 20h, and then air-cooled to room temperature to obtain a high-strength motor rotor aluminum alloy.

[0072] Comparative Example 12

[0073] The difference between this comparative example and Example 2 is that centrifugal die casting is used in step S3 of this comparative example. 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 allowed to cool naturally to room temperature.

[0074] Experimental Example 1

[0075] The mechanical properties and elongation of the aluminum alloys obtained in the above embodiments and comparative examples were tested, and their surface morphology was observed. The results are shown in Table 1 below. The test specimen dimensions conform to ASTM E8.

[0076] Table 1

[0077]

[0078] The results showed that the aluminum alloys obtained in Examples 1-3 of this invention had high yield strength and tensile strength, and elongation of over 20%, with no surface defects such as hot cracks or porosity. In contrast, the contents of Si, Mg, and Fe in Comparative Examples 1-6 were either too high or too low, and the ratio of Si to Mg and the total content of Si, Mg, and Fe were not within specific ranges. The strength or elongation of the resulting aluminum alloys was significantly lower than that of Example 2, and surface defects such as hot cracks appeared. The mechanical properties and elongation of the aluminum alloys obtained in Comparative Examples 7-9 were also significantly lower than those in the examples. This demonstrates that by limiting the silicon-magnesium content ratio and the total content of Si, Mg, and Fe, the risk of hot cracking is reduced. Especially during casting and cooling, the crystal structure of the alloy is more uniform, reducing the tendency for hot cracking, improving mechanical properties and ductility, and avoiding the defects of the prior art.

[0079] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A high-strength aluminum alloy for motor rotors, characterized in that, It contains the following components by mass percentage: Si 0.28-0.32%, Mg 0.68-0.74%, Fe 0.3-0.35%, Ti≤0.05%, Ga≤0.03%, Zn≤0.03%, Cu≤0.03%, Mn≤0.01%, unavoidable impurities≤0.01%, balance Al; The content ratio of Si to Mg is 1:(2.1-2.6). The method for preparing the high-strength motor rotor aluminum alloy includes the following steps: S1. The alloy raw materials are added to the melting furnace and melted to obtain a melt; S2. The melt is refined using argon gas; S3. After the melt has been refined in step S2, it is left to stand for more than 30 minutes and then subjected to high-pressure die casting to obtain the casting. S4. Heat treatment is performed on the casting obtained in step S3. The heat treatment steps are as follows: heat the casting to 180-200℃ at a heating rate of 90-100℃ / h, hold it at the temperature for 20h, and then air cool it to room temperature to obtain a high-strength motor rotor aluminum alloy. In step S3, the high-pressure die casting temperature is 705-725℃, and the high-pressure die casting pressure is 650-750MPa.

2. The high-strength aluminum alloy for motor rotors according to claim 1, characterized in that, The content ratio of Si to Mg is 3:

7.

3. The high-strength aluminum alloy for motor rotors according to claim 1, characterized in that, The total content of Si, Mg and Fe is ≤1.35%.

4. The method for preparing the high-strength motor rotor aluminum alloy according to any one of claims 1-3, characterized in that, Includes the following steps: S1. The alloy raw materials are added to the melting furnace and melted to obtain a melt; S2. The melt is refined using argon gas; S3. After the melt has been refined in step S2, it is left to stand for more than 30 minutes and then subjected to high-pressure die casting to obtain the casting. S4. The casting obtained in step S3 is subjected to heat treatment. The heat treatment steps are as follows: the casting is heated to 180-200℃ at a heating rate of 90-100℃ / h, held at the temperature for 20h, and then air-cooled to room temperature to obtain a high-strength motor rotor aluminum alloy.

5. The method for preparing high-strength motor rotor aluminum alloy according to claim 4, characterized in that, In step S1, the melting temperature is 710-750℃.

6. The method for preparing high-strength motor rotor aluminum alloy according to claim 5, characterized in that, The melting temperature is 730℃.

7. The method for preparing high-strength motor rotor aluminum alloy according to claim 4, characterized in that, In step S2, the refining temperature is 720-740℃ and the refining time is 15-20 minutes.

8. The method for preparing high-strength motor rotor aluminum alloy according to claim 7, characterized in that, In step S2, the refining temperature is 730°C and the refining time is 15 minutes.

9. The method for preparing high-strength motor rotor aluminum alloy according to claim 4, characterized in that, In step S3, the high-pressure die-casting temperature is 715°C and the high-pressure die-casting pressure is 700 MPa.

10. The application of the high-strength motor rotor aluminum alloy according to any one of claims 1-3 or the high-strength motor rotor aluminum alloy prepared by the preparation method according to any one of claims 4-9, characterized in that, It is suitable for the rotor of motors in new energy vehicles.

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